ERRATA MCI SEPT 2011.

45. Largest source of radiation exposure to general population is
a. Computers
b. Diagnostic radiology
c. Nuclear weapons
d. Freon

thanks for the feedback .

AIIMS MAY 2011 with explanations

ANATOMY


1. All are seen in Horner’s syndrome except

a. Heterochromia iridis

b. Ptosis

c. Mitosis

d. Apparent exophthalmos

Ans. D Apparent exophthalmos

* Horner syndrome presents with enophthalmos (and not expothalmos-d)

- Enophthalmos (snken eyeball) is due to paralysis of the orbitalis muscle

- Orbitalis muscle is supplied by T-1 sympathetic bifres and is important for slight protrusion of eyeball, It’s paralysis leads to sunken eyeball



*Horner syndrome is essemtially a triad of: Miosis (c) with ipsilateral ptosis (b) and Anhydrosis

- Most cases are idiopathic, but it could be due to brainstem lesions, carotid dissection, or neoplasm compressing upon the sympathetic chain (E.g Pancoast tumor)



*Heterochromia irides (a) may be present it the lesion occurred in a child younger than 2 years. The affected iris may remain blue when the other iris changes to brown/ black

-iris pigmentation is under sympathetic control during development, which is completed by age 2 years

- Heterochromia is uncommon in patients with Horner syndrome acquired later in life



*Sympathetic nervous system is concerned with the fright/fight/flight (Emergency) reaction and leads to

- Elevation of upper eyelied by Muller muscle (wide open eyes)

- Pupillary dilatation by Dilator papillae (wide open eyes)

- Sweating (sudomotor)

- Pallor of the skin (vasomotor)

* This activity is under Sympathetic T-1 nerves in the face, and are lesioned in Horner syndrome leading to

-Drooping of upper eyelid (ptosis)- due to unopposed orbicularis oculi

-pupillary constriction (miosis) –due to unopposed sphincter papillae

-Loss of sweating (anhydrosis)

-Red flushed face –due to loss of vasoconstrictive tone (and resultant vasodilation) in the skin s



References

1. Pg. 560; Gray’s Anatomy (39th Ed)



2. Fascia around nerve bundle of brachial plexus is derived from

a. Prevertebral fascia

b. Clavipectoral fascia

c. Pre-tracheal fascia

d. Pectoral fascia



Ans. A Prevertebral fascia

* Fascia around the brachial plexus is called as axillary sheath and is a derivative of pre-vertebral fascia (a)

* Prevertebral fascia (PVF) covers the anterior vertebral muscles and lies on the anterior aspect of scalenus anterior and medius thus forming the floor of posterior triangle of neck.



* Brachial plexus emerge between scalenus and medius in the neck and pass behind the clavicle along with subcalvian artery to reach the axilla

- In the process they carry an extension of PVF over them as a cover (the axillary sheath) towards the axial

- subclavian/Axillary veins lie outside the axillary sheath and therefore can distend freely

* Applied antomy

* Neck infections behind the PVF are usually due to tuberculosis of cervical bertebral and may from chronic retropharyngeal absecess – a bulging in the posterior wall of pharynx

- the pus may track into the axilla via the axillary sheath and point in the posterior/lateral wall of axialla.

- the pus may also extend into the superior mediastinum but doesn’t reach the posterior mediastinum, since the PVF fuses to the fourth thoracic vertebra

* PVF is separeated from the pharynx/buccopharyngeal fascia by the retro-pharyngeal space

- Neck infections in front of PVF in the retropharyngeal space forms acute retropharyngeal abscess which bulges forward in the paramedian position

- This is due to attachment of PVF with Buccopharyngeal fascia in the median plane

- This infection may spread to the posterior mediastinum via the superior mediastinum

* most of the nerves in the neck are behind the PVF but spinal accessory nerve lies superficial to it and may get damaged quite often

-Spinal accessory nerve is the most common nerve damaged iatrogenically. The happens mostly during I & D (Incision & Drainage) Procedures in the neck



References:

1.Pg. 542, Gray’s Anatomy (39th Ed.)



3. Root of mesentery is crossed by

a. Inferior mesenteric artery

b. Horizontal part of douddenum

c. Left ureter

d. Left gonadal vessel

Ans. B Horizontal part of duodenum

- Root of mesentery crosses the third of the duodenum, which is alos called as the horizontal part of the duodenum

- Root of mesentery starts at the left side of the L-2 vertebra and runs infero-laterally towards the right side, to end at the right sacro-iliac joint

- The root of mesentery lies on the posterior abdominal wall and crosses the right but not the left ureter and gonadal vessels

- It also crosses the superior mesenteric artery, but inferior mesenteric artery



References:

1. Pg. 247; B D chaurasia (5th Ed.); Vol-2



4. Carpal tunnel syndrome caused by all except

a. Hypothyroidism

b. Addison’s disease

c. Diabetes mellitus

d. Amyloidosis

Ans. B Addison’s disease

* Addison’s disease has not been co-related with carpal tunnel syndrome in clinical studies

- Hypothyroidism leads to Myx-oedema, and leads to increase in the thickness (myxomatous) of tendons passing under the flexor retinaculum. This comporomiss the carpal tunnel space, leading to compression of the median nerve passing through it

- Diabetes mellitus leads to nerve pathology, makes them weak and fragile, hence prone to any compression injury (including carpal tunnel syndrome)

- Amyloid deposits make the space of carpal tunnel compromised, thus predisposing to median nerve compression under the flexor retinaculum

References:

1. Harrison (17th Ed.) Pg. 214, 21154, 2231



5. Weight transmission from upper limb to axial skeleton is done by all except

a. Costo-calvicular ligament

b. Coraco-acrominal ligament

c. Coraco-calvicular ligament

d. Inter –calvicular ligament

Ans. B. Coraco-acrominal ligament

Ref: Gray’s 14th edition, Chapter 46

Interclavicualr ligament

• The interclavicular ligament is continous above with deep cervical fascia, and unites the superior aspect of the sterna ends of both calvicles: some fibres are attached to the superior manubrial margin

• Costoclavicular ligament

• The costoclavicualr ligament it like an inverted cone, but short and flattened. It has anterior and posterior laminae which are attached to the upper surface of the first rib and costal cartilage, and ascends to the margins of an impression on the inferior clavicular surface at its medial end. Fibres of the anterior lamina ascend laterally and those of the posterior lamina (which are shorter) ascend medially (Fig.1) they fuse laterally and nerve medially with the capsule



Acromioclavicular ligament

The coracoclavicualr ligament is quadrilateral. It extends between the upper aspects of the lateral end of the clavids and the adjoin acromion. Its parallet fibres interface with the aponeuroses of trapezius and deltoid



Coracoclavicular ligament

• The coracoclavicualr ligament connects the clavicle and the coracoids process of the scapula (Fig.1). Thought separate from the acromicocalvicular joint, it is a most efficient accessory ligament, and mainfains the apposition of the clavicle to the acromion

• The trapezoid and conoid parts of the ligament, usually separated by fat or, frequently, by a bursa, connect the medial horizontal part of the coracoid process and lateral end of the subclavian groove of the clavicle; these adjacent areas may even be covered by cartilage to from a coracoclavicular joint.

• The trapezoid part is anterolateral and is broad, thin and quadrilateral ascending slightly from the upper coracoids surface to the trapezoid the on the inferior clavicular surface. It is almost horizontal, its anterior border as free, and its posterior border is joined to the conoid part, forming an angle which projects backwards

• The conoid part is posteromedial and is a dense, almost vertical triangular band. Its base is attached to the conoid tubercle of the calvicle and its inferior apex is attached posteromedially to the root of the coracoids process in front of the scapular notch



All ligament excluding coracoacromial are seen to connect scapula to axial skeleton. Hence they help in transfer of weight



6. Which of the following artery is more susceptibkle for dissenction whicl doin arteriography

a. Celiac axis

b. Gastro duodenal artery

c. Superior mesenteric artery

d. Inferior mesenteric artery

Ans. (D) Inferior mesenteric artery

During cauterization through femoral route following are % of dissection

1. Inferior mesenteric - 7.5%

2. Gastro duodenal artery - 6.8%

3. Superior mesenteric - 0.3%

4. Coeliac axis -1.1%



In human anatomy, the inferior mesenteric artery, often obbreviated as IMA, supplies the large intestine from the left colic (or splenic) flexure to the upper part of the rectum, which includes the descending colon, the sigmoid colon, and part of the rectum. Proximally, its territory of distribution overlaps (forms a watershed) with the middle colic artery, and therefore the superior mesenteric artery. The SMA and IMA anastomose via the marginal artery of the colon (artery of Drummond). The territory of distribution of the IMA is more or less equivalent to the embryonic hindgut



Branching

The IMA branches of the anterior surface of the abdominal aorta below the renal artery branch points, and approximately midway between these and the aortic bifurcation (into the common iliac arteries)



The IMA has the following branches:

Branch Notes

Left Colic Artery Supplies descending colon

Sigmoid Branches The most superior being described as ‘the superior sigmoid artery

Superior Branches Effectively the terminal branch of the IMA (the continuation of the IMA after all other branches )

All these arterieal branches further divide into arcades which then supply the colon at regular intervals



Surgery and Pathology

The IMA and/or its branches muse be resected for a left hemicolectomy

7. Vertical crest in fundus of internal acoustic canal is

a. Facial crest

b. Bill’s bar

c. Ponticulus

d. Cog

Ans. (B) Bill’s bar

Ref: Manual of middle ear surgery: Mastoid surgery and reconstructive procedures by Mirko Tos

The fallopian canal which contains facial nerve begins at the fundus superior to the transverse crest, and anterior to Bill’s bar. (The vertical crest) it passes laterally and anteriorly towards the geniculate ganglion.



8. Boundary of triangle of auscultation is not formed by

a. Scapula

b. Trapeziu’s

c. Latissimus dorsi

d. Serratus anterior

Ans. D Serratus anterior

• Serratus anterior (d) is inserted on the medial border of scapula but lies anterior to scapula hence is not in the triangle especially, the sounds of swallowed fluids.

• Cardiac end of the stomach lies deep to this triangle



References:

1. Pg. 64; B D Chaurasia (4th Ed.); Vol-1



9. Sternocleridomastoid is supplied by all of the following arteries except

a. Superior thyroid

b. Thyrocervical trunk

c. Occipital

d. Post auricular



Ans. B Thyrocervical trunk

• Thyrocervical trunk (b) seems to be the most appropriate answer, thought suprascapular artery is a branch of thyrocervical trunk and supplies the lower part of stermocleidomastoid

• Remember, in such questions we may have no appropriate answer but we have to use the strike out method and method and choose the less definite/left over option ]

• Upper part of the muscle is supplied by the occipital (c) and posterior auricular (d) artery

• middle part is supplied by the superior thyroid (a) artery

• Definitely a/c/d are stroked out and not our answers.

• Applied anatomy: A superiorly based flap can be raised on sternocleidomastoid to reconstruct the lip, floor of mouth and inner cheeks

• But a converntional myo-cutaneous flap like pectoralis major flap is a better alternative

• Microvascular fre transfer flaps have superseded all the conventional methods now a day



References:

1.Pg. 536; grays Anatomy (39th Ed.)



10. In a subcalvian artery block at the outer border of 1st rib, of the following arteries help in maintaining the circulation to upper limb except

a. Subscapular

b. Thyrocervical trunk

c. Suprasvapular

d. Superior thoracic

Ans. D Superior thoracic

• Scapular anastomosis maintains circulation to the upper limb clinical situation, which doesn’t involve superior thoracic (d) artery

• A block of Subclavian artery distally at the outer border of first rib (E.g. Cervical rib) or axillary artery proximally (E.g. axillary metastasis of Ca Breast) compreomises blood supply to the upper limb

• collateral circulation (scapular) opens up to maintain the circulation to the upper limb.

• Scapular anatomosis involves branches of proximal subcalvian and distal axillary arteries as following

1. subcalvian artery- Thyrocervical trunk (b) branches: Supra scapular (c) and Deep branch of transverse cervical .

2. Axillary artery Sub scaular(a), Posterior circumflex humeral and thoraco-acrominal arteries

• Deep branch of transverse cervical (subclavian) mainly anastomose with subscapular (axillary)

• Suprascapular (subclavian) mainly anastomose with Circumflex scapular (axillary)



References:

1. Pg. 841, 42; Gray’s Anatomy (39th Ed.)



11. Spleen projects into the following space of peritoneal cavity

a. Greater sac

b. Left subhepatic space

c. Infracolic compartment

d. Paracolic gutter

Ans. A Greater Sac

• Spleen develop in the dorsal mesentery and projects into the grater sac (a) of peritoneal cavity



• Liver develops in the ventral mesentery and is also projecting into the greater sac



• Lesser sac is the smaller part of peritoneal cavity lying posterior to the stomach. It is also called as left posterior (Sub-hepatic-b) space.



• Spleen is separated from the lesser sac by the Gastro-spenic and Lieno renal ligaments



• Left anterior (Sub-hepatic-b) space reaches the spleen, but spleen is not projecting into it.



• Spleen lies above the level of transverse colon and is in the supra-colic compartment (and not the infra-colic - c).



• infracolic compartments lie below the transverse colon and are having the right & left paracolic gutters. This compartment extends till true pelvis.



• Sp!een is separated from the left paracolic gutter (d) by the phreno-colic ligament



• Phrenocolic ligament attaches the splenic flexure of transverse colon to the diaphragm and supports the anterior end of spleen, preventing its projection into the left paracolic gutter.



Supra-coiic compartment has a number of spaces:

-1. Right subphrenic space -2. Right subhepatic space (Hepato-renal pouch of Morrison)

-3. Lesser sac -4. Left subphrenic space '

-5. Left sub-hepatic space



-
nfra-coMc compartment spaces:

-1 . Right para-colic gutter -2. Left para colic gutter



The right paracolic gutter is continuous with the right supra-colic compartment, and hence, bile/pus/blood released from viscera above can reach inferiorly till the pelvic cavity.

-For e.g., Trackingof.pus in gastric ulcer perforation:



Pus of gastric antra! perforation moves into iesser sac → Epiploic foramen→ Hepatorenal pouch of Morrison (supra-coljc compartment).

→ Right paracolic gutter (infracolic compartment) → Pouch of Douglas (pelvic cavity).



The right supra-colic compartment) is separated from the right paracolic gutter (Infracolic compartment) by the phrenp-colic ligament and that's why right iliac fossa collections are more common than the left.



References:

1. Pg. 230,233,234; B D Chaurasia (4th Ed.); V

2. Pg.1 135, 6; Gray's Anatomy (39th Ed.)



12. Which of the following is the terminal group of lymph node for colon?

a. Preaortic

b. Intermediate

c. Para colic

d. Epicolic



Ans. A. Preaortic



Colonic lymphatic drainage terminally reaches Superior & Inferior mesenteric lymph nodes, which belong to the Pre-aortic (a) lymph nodes.



'Lymph from colon passes through 4 set of lymph nodes:

-Epi-colic - d (lie on the serosal wall of gut) → Para-colic - c (on medial side of ascending/descending colon £ mesenteric border of transverse/sigmoid colon) →Intermediate - b (on named branches of colonic vessels) →Pre-terminal/pre-aortic - a (on Inferior/superior mesenteric vessels).

- The efferents from the pre-aortic lymph nodes drain into the coeliac lymph nodes (terminal), which also belong to the pre-aortic

category.

-Coeliac lymph nodes then drain into the intestinal trunks which ultimately join the cisterna chyli.





'Aortic lymph nodes are present on the posterior abdominal wall and divided into - pre, lateral and retro Aortic.

-Collectively, they are called as para-aortic lymph nodes.



-Preaortic lymph nodes lie anterior to abdominal aorta and is divided into - Coeliac, Superior mesenteric and Inferior mesenteric,

- Coeliac lymph nodes are the terminal pre-aortic lymph nodes and drain the foregut derivatives.



-They also receive the lower (pre-terminal) pre-aortic - superior/inferior mesenteric lymph nodes.

'Superior/Inferior mesenteric lymph nodes are pre-terminal draining the mid/hind gut derivatives. They ultimately drain towards the

terminal lymph nodes - the coeliac lymph nodes.



-Pre-aortic terminal coeliac lymph nodes send their efferents towards the intestinal trunks, which ultimately enter the cisterna chyli.



'Lateral aortic lymph nodes lie on each side of abdominal aorta and receive afferents mainly from the common iliac lymph nodes.

-The efferents form the lumbar trunks, which enter the cisternal chyli.

-Few efferents pass to pre-aortic/retro-aortic lymph nodes.

- Retro-aortic lymph nodes are a very small group and are considered as an extension of lateral aortic lymph nodes only. ,

ixfends

'Lymph flow from the pelvic region; Sacral/External/lnternal iliac -» Common iliac -> Lateral Aortic -> Lumbar trunks -* Cisterna

chyli,

-Lateral sacral lymph nodes drain into the Common iliac group.



References:

1. Pg. 254,317; B D Chaurasia (4th Ed.); Vol-2.

2. Pg. 1122-3,1182, 6; Gray's Anatomy (39th Ed.)



13. AM of the following muscles retract the scapula except

a. Levator scapulae

b. Trapezius

c. Rhomboideus major

d. Rhomboideus minor

Ans, A. Levator scapulae

Levator scapulae muscle is mainly an elevator of scapula.



'Origin and insertion of levator scapulae decides its functions:

• It arises by tendinous slips from the transverse processes of the atlas and axis vertebrae and from the posterior tubercles of the transverse processes of the third and fourth cervical vertebrae.

- K is inserted into the vertebral border of the scapula, between the medial angle and the triangular smooth surface at the root of the spine.



Actions of levator scapulae:

- If the head is fixed,, the levator scapulae raises the media! angle of the scapula.

- If the shoulder is fixed, the muscle inclines the neck to the corresponding side and rotates it in the same direction.

- The levator scapulae, along with the trapezius muscle, makes a shrug at shoulder possible.



Protraction of scapula takes scapula away from midline as happens in pushing a wail in front. The protractors of scapula are: -

- Serratus anterior .. - Pectoraiis minor



*Retraction of scapula brings the scapula back to the midline.

*The main retractors of scapula are:

- Trapezius

- Rhomboideus minor

- Rhomboideus major

References:

Pg. 809,810; Gray's Anatomy (40th Ed.)



14. Sphincter of Oddi consists of how many sphincters

a. 2

b. 3

c. 4

d. 5

Ans. B. 3

• The sphincter of Oddi consists of circular and longitudinal smooth muscle fibers surrounding a variable length of the distal bile and pancreatic duct.

• There are three discrete areas of muscle thickness and 3 mini sphincters:

o Bile duct sphincters (surround the common bile duct)

o Pancreatic sphincter (surround the pancreatic duct), and

o Ampullary sphincter (surrounds hepato-pancreatic duct)

• Ampullary sphincter is divided surgically (sphincterotomy) to approach the common bile duct, while performing ERCP (Endo-scopic retrograde cholangio-graphy).

• Variations in the relation between the common bile duct and the pancreatic duct at the duodenal opening:

o Both the ducts form a common opening with no sphincter mechanism to protect flow between the ducts - Y shape

o A common opening is present but for a very short length - V shape

o Separate openings* are present for the 2 ducts (rare) - U shape

• Chances of gall stones are less if there are separate openings.

• Sphincter of Oddi dysfunction (SOD)

o Passage of stones, pancreatitis or endoscopic sphincterectomy can lead to scarring or stenosis of the Oddi sphincter leading to SOD.

o It can result in dilatation of bile duct and pancreatic duct.

o Pain is a common feature but the dysfunction is not fatal.

o SOD is more common in females.

o Sphincter-ectomy or stenting of the involved duct is recommended for chosen cases. Surgical transduodenal

o sphincteroplasty is advised for some selected cases for long term palliation.



References:

1178; Gray's Anatomy (40th Ed.)



15. Which of the following is not true about the trochlear nerve

a. Longest intracranial course

b. Arise from dorsal aspect

c. Supplies ipsilateral superior oblique

d. Arises from out side the common tendinous ring

Ans. C. Supplies ipsilateral superior oblique

Trochlear nerve innervates the contralateral (and not ipsilatera!- c) superior oblique.

-Left Trochlear nucleus gives the axons which decussate within the brainstem (internal decussation} and become the right trochlear nerve.



-Similarly left trochlear nerve arises from the neuron bodies on the right (right occulomotor nucleus). Lesion of right occulomotor nucleus will paralyse the left superior obiique.



-Superior rectus muscle is also supplied contralaterally by the occulomotor nerve. Left occulomotor nucleus supplies the right superior rectus.



'Trochlear nerve is the only cranial nerve which exits dorsally (b) from the brainstem.

-This nerve exits dorsally/ posteriorly, loops around the brainstem and turns anteriorly to move along with other cranial nerves -which all exit the brainstem anteriorly.



-Trochlear nerve gains additional length as it goes dorsal and then comes ventral, whereas other nerves were simply exiting ventrally. Thus the nerve has the longest intracranial course (a).



-It is also having the longest intracranial (subarachnoid) course.



Severe head injury may lead to torn trochlear nerve (due to its long intracranial course) and the patient presents with paralysed

superior oblique. This leads to diplopia and difficulty in reading /going downstairs.



-"Head tilt test" is a cardinal diagnostic feature - Diplopia is redu:ed on turning the head away from the site of lesion.



'Abducent nerve has the longest intracranial (intradural) course.



-Because of the long course, it is often stretched when intracranial pressure rises and presents with lateral rectus palsy- Medial squint, .



'Evolutionary history suggests thai the trochlear nerve used to supply pineal gland (dorsally) and then turn anteriorly to reach the orbit and supply superior oblique. At present there is no evidence of trochlear nerve axons entering the pineal gland.



'Trochlear nerve passes through the superior orbital fissure to reacn ine orDii and supply superior oblique rnuscie. IT passes

outside (d) the common tendinous ring of Zinn.



-Occulomotor & Abducent nerves also pass through the superior orbital fissure, but they pass inside the CTR of Zinn.



References: • *

1. Pg. 193; Harrison's Internal medicine (17th Ed.)



16. True about hepatic duct are all except

a. Caudate lobe drains only left hepatic duct]

b. Right anterior hepatic duct formed by V and VIII segment

c. Left hepatic duct formed in umbilical fissure

d. Left hepatic duct crosses IV segment



Ans. A. Caudate lobe drains only left hepatic duct



• Caudate Jobe.(segment I) of left surgical liver drains into both right and left hepatic ducts.

• According to Couinaud's classification, the liver is divided into 8 (subsequently 9) segments

o Left surgical liver - segments I, II, III and IV

o Right surgical liver - segments V, VI, VII & VIII

• Right hepatic duct receives segments V, VI, VII & VIII (right surgical liver).



• Right anterior tiepatic duct (RASD - right anterior segmentai duct) is formed by V and VIII segment and Right posterior hepatic duct (RPSD) is formed by VI and VII segment. Both these hepatic ducts join to form the Right hepatic duct.



• Left hepatic duct is formed by the ducts draining II, III and IV segment of left surgical liver.



• Bile ducts draining Segment I (Caudate lobe) open into both the right & left hepatic ducts near their point of confluence.



• Segment I is closely related to porta hepatis and inferior vena cava and is usually not resected in liver operations.



• Umbilical fissure lies in the left surgical liver on inferior surface

o It is the fissure for Ligamentum feres

o It separates segment III from IV

o Lies along the plane of Left hepatic vein

o It is often avascular and can be divided safely with diathermy during surgeries

o It contains the final divisions of left hepatic duct

o The knowledge of arrangement of the portal vein, hepatic artery and the bile duct within this fissure is important for liver transplantation surgeries.

• Left hepatic duct is formed in the umbilical fissure and lies along the base of segment IV.



References:i) Pg. 1166, 1178; Gray's Anatomy (40th Ed.)









































































BIOCHEMISTRY

1. The gaps between segments of DMA on the lagging strand produced by restrictin enzymes are rejoined / sealed by

a. DNA Ligases

b. DNA Helicase

c. DNA Topoisomerase

d. DNA phosphorylase

Answer: A. DNA Ligases



The fragments of newly synthesized DNA on the lagging strand are joined / sealed by DNA ligases

Enzyme Primary Function

Helicase Unwinds the DNA to provide single stranded DNA

Topoisomerase Relieves torsional strain that results from helicase induced unwinding

DNA prlmase Intiates synthesis of RNA primers

DNA polymerase



Polymerizes dexnucleotides (Polymerizes DNA)

Polymerase I : Gap filling & synthesis of lagging strand

Polymerase II : DNA proof reading and repair

Pofymerase III: Processive leading strand synthesis (5 -> 3 direction)

DNA ligase Seals the nicks between okazaki fragments on lagging strand.

2. CAP in lac operon is an example of

a. Positive regulator

b. Negative regulator

c. Constitutive expression

d. Attenuation

Answer: A. Positive regulator

• Lac operon an example of negative regulation operon required for the transport and metabolism of lactose in Escherichia coli and some other enteric bacteria. It consists of three adjacent structural genes, lacZ, lacY and lacA.

• The lac operon is regulated by several factors including the availability of glucose and of lactose. Gene regulation of the lac operon was the first complex genetic regulatory mechanism to be elucidated and is one of the foremost examples of prokaryotic gene regulation.

• In its natural environment, the lac operon allows for the effective digestion of lactose. The cell can use lactose as an energy source by producing the enzyme U-galactosidase to digest that lactose into glucose and gaiactose.

• However, it would be inefficient to produce enzymes when there is no lactose available, or if there is a more readily-available energy source available such as glucose;

• The lac operon uses a two-part control mechanism to ensure that the cell expends energy producing p-galactosidase, p- gatactoside permease and thiogalactoside transacetylase (also known as galactoside 0-acetyltransferase) only when necessary.-

• It achieves this with the lac represser, which halts production in the absence of lactose, and the Catabolite activator' protein (CAP), which assists in production in the absence of glucose. Thus CAP is positive regulator

• This dual control mechanism causes the sequential utilization of glucose and lactose in two distinct growth phases, known as diauxie. Similar diauxic growth patterns have been observed in bacteria! growth on mixtures of other sugars as well, such as mixtures of glucose and arabinose, etc.

• The genetic control mechanisms underlying such diauxic growth patterns are known as xyl operon and ara operon, etc.



Structure of lactose and the products of its cleavage.



• The lac operon consists of three structural genes, and a promoter, a terminator, regulator, and an operator. The three structural genes are: lacZ, lacY, and lacA.

• lacZ encodes ®-galactosidase (LacZ), an intracellular enzyme that cleaves the disaccharide lactose into glucose and gaiactose.

• lacY encodes® -galactoside permease (LacY), a membrane-bound transport protein that pumps lactose into the cell.

• lacA encodes (3-galactoside transacetylase (LacA), an enzyme that transfers an acetyl group from acetyl-CoA to p-galactosides.

Only lacZ and lacY appear to be necessary for lactose catabolism.

• Specific control of the lac genes depends on the availability of the substrate lactose to the bacterium. The proteins are not produced by the bacterium when lactose is unavailable as a carbon source.

• The lac genes are organized into an operon; that is, they are oriented in the same direction immediately adjacent on the chromosome and are co-transcribed into a single polycistronic mRNA molecule.

• Transcription of all genes starts with tie binding of the enzyme RNA poiymerase (RNAP), a DNA-binding protein, which binds to a specific DNA binding site, the promoter, immediately upstream of the genes.

• From this position RNAP proceeds to transcribe all three genes (lacZYA) into mRNA. The DNA sequence of the E. coli lac operon, the lacZYA mRNA, and the lacl genes are available from GenBank . ~

• The first control mechanism is the regulatory response to lactose, which uses an intraceliular regulatory protein called the lactose represser to hinder production of p-galactosidase in the absence of lactose. » The lacl gene coding for the represser lies nearby the lac operon and is always expressed (constitutive). If lactose is missing from the growth medium, the represser binds very 'tightly to a short DNA sequence just downstream of the promoter near the beginning of lacZ called the lac operator.

• The represser binding to the operator interferes with binding of RNAP to the promoter, and therefore mRNA encoding LacZ and LacY is only made at very low levels. When cells are grown in the presence of lactose, however, a lactose metabolite called alloiactose, which is a combination of glucose and galactose, binds to the represser, causing a change in its shape.

• Thus altered, the represser is unable to bind to the operator, allowing RNAP to transcribe the lac genes and thereby leading to high levels of the encoded proteins.

• The second control mechanism is a response to glucose, which uses the Catabolite activator protein (CAP) to greatly increase production of (3-galactosidase in the absence of glucose.

• Cyclic adenosine monophosphate (cAMP) is a signal molecule whose prevalence is inversely proportional to that of glucose.

• It binds to the CAP, which in turn allows the CAP to bind to the CAP binding site (a 16 bp DNA sequence upstream of the promoter on the left in the diagram below), which assists the RNAP in binding to the DNA.

• In the absence of glucose, the cAMP concentration is high and binding of CAP-cAMP to the DNA significantly increases the production of p-galactosidase, enabling the cell to hydrolyse (digest) lactose and release galactose and glucose.

Reference:

• Principle of Biochemistry by Lehninger, 3rd edition, Pages 1074 - 1087 Jacob F; Monod J (June 1961). "Genetic regulatory mechanisms in the synthesis of proteins". J Mql Biol. 3: 318-56.

3. Which of the following plant components is not fermented by gastrointestinal microorganisms

a. Lignin

b. Cellulose

c. Hemicellulose

d. Pectin

Answer: A. Lignin

Lignin is a non carbohydrate type f dietary fiber that can neither be digested by endogenous mammalian enzymes nor fermented by gasrointestinal microorganism.

Cellulose, hemicellulose and pectins are all components that cannot be digested by endogenous enzymes, but these components can be fermented by local resisdent bacteria in a gastrointestinal tract.



Type of Fiber

Digestion / Hydrolysis in small

intestine Digestion / Fermentation by colonic bacteria

In soluble

Cellulose

Hemicellulose

Lignin Not digested

Not digested

Not digested Fermented

Fermented

Not Fermented



Solube

Pectins

Gums and

Alginates Not digested

Not digested Fermented

Fermented



4. Triplex DNA is formed because of

a. In palindromic sequences

b. Increase no. of guanosine repeat

c. Increase in polypyrimidine sequences

d. Hoogstein pairing

Answer: D. Hoogstein pairing

• A Hoogsteen base pair is a variation of base-pairing in nucleic acids such as the A«T pair. In this manner, two nucleobases on each strand can be held together by hydrogen bonds in the major groove.

• A Hoogsteen base pair applies the N7 position of the purine base (as a hydrogen bond acceptor) and C6 amino group (as a donor), which bind the Watson-Crick (N3-N4) face of the pyrimidine base.

• This term is named for Karst Hoogsteen, who. in 1963, first recognized the potential for these unusual pairings (quoted from Lehninger Principles of Biochemistry by David Nelson and Michael Cox, 4th edition, published in 2005 by Freeman).

Chemical properties

• Hoogsteen pairs have quite different properties from Watson-Crick base pairs. The angle between the two glycosylic bonds (ca. 800 in the A* T pair) is larger and the C1-C1' distance (ca. 860 pm or 8.6 A) is smaller than in the regular geometry.

• In some cases, called reversed Hoogsteen base pairs, one base is rotated 180° with respect to the other.



Triplex structures

This non-Watson-Crick base-pairing allows the third strands to wind around the 'duplexes, which are assembled in the Watson Crick pattern, and form triple-stranded heiices such as (poly(dA)*2poly(dTV) and (poly(rC)»2poly(rC)). !t can be also seen in three-dimensional structures of transfer RNA.



To form a triplex, a sequence must conform to unusual requirements. One can see that the guanine and thymine residues in the half of the purine-rich strand that turns back to make a triplex form Hoogsteen hydrogen bonds with guanine and adenine residues, respectively, in the other half of the same strand

References:

In vivo veritas: Using yeast to probe the biological functions of G-quadruplexes. Johnson JE, Smith JS, Kozak ML, Johnson FB. Biochimie. 2008



5. Which is true about histone acetylation

a. Increased euchromatin formation

b. Increased heterochromatin formation

c. Methylation of DMA

d. DNA replication

Answer: A. Increased euchromatin formation

• In histone acetylation and deacetylation, the histones are acetylated and deacetylated on lysine residues in the N-terminal tail and on the surface of the nucleosome core as part of gene regulation,

• Typically, these reactions are catalyzed by enzymes with "histone acetyltransferase" (HAT) or "histone deacetylase" (HDAC) activity. The source of the acetyl group in histone acetylation is Acetyi-Coenzyme A, and in histone deacetylation the acetyl group is transferred to Coenzyme A.

• Acetylated histones and nucleosomes represent a type of epigenetic tag within chromatin. Acetytation brings in a negative charge, acting to neutralize the positive charge on the histones and decreases the interaction of the N termini of histones with the negatively charged phosphate groups of DNA.

• As a consequence, the condensed chromatin is transformed into a more relaxed structure which is associated with greater levels of gene transcription.

• This relaxation can be reversed by HDAC activity. Relaxed, transcriptionally active DNA is referred to as euchromatin. More condensed (tightly packed) DNA is referred to as heterochromatin. Condensation can be brought about by processes including deacetylation and methylation; the action of methylation is indirect and has no effect upon charge.

• This charge neutralization mode! has been challenged by recent studies, according to which transcriptionaily active genes are correlated with rapid turnover of histone acetylation.

• This requires that the HATs and HDACs must act continuously on the affected histone tail. Methylation at a specific lysine residue (K4) is involved in targeting histone tails for continuous acetylation and deacetyiation.

• Eukaryotic DNA is packaged into a nucleoprotein structure known as chromatin.. which is comprised of DNA, histones, and nonhistone proteins.

• Chromatin structure is highly dynamic, and can shift from a transcriptionaily inactive state to an active form in response to intra-and extracellular signals. A major factor in chromatin architecture is the covalent modification of histones through the addition of chemical moieties, such as acetyl. methyl, ubiquitin, and phosphate groups.

• The acetylation of the amino-terminal tails of histones is a process that is highly conserved in eukaryotes, and was one of the earliest histone modifications characterized. Since its identification in 1964, a iarge body of evidence has accumulated demonstrating that histone acetylation plays an important role in transcription.

• Despite our ever-growing understanding of the nuclear processes involved.in nucieosome acetylation, however, the exact biochemical mechanisms underlying the downstream effects of histone acetylation have yet 10 be fully elucidated.



6. Which of the following method Is use for detection of protein motion irorri ceii nuclei to cytoplasm

a. FISH

b. FRAP

c. Electron microscopy

d. Confoca! microscopy ; -

Answer: B. FRAP

• Fluorescence recovery after photobleaching (FRAP) denotes an optica! technique capable of quantifying the two dimensional lateral diffusion of a molecularly thin film containing fiuorescently labeled probes, or to examine single cells

• This technique is very useful in biological studies of cell membrane diffusion and protein binding. In addition, surface deposition of a ftuorescing phospholipid bilayer (or monolayer) allows the characterization of hydrophilic (or hydrophobic) surfaces in terms of surface structure and free energy,

• Similar, though less well known, techniques have been developed to investigate the 3-dimensional diffusion and binding of molecules inside the cell; they are also referred to as FRAP,

• This technique is commonly used in conjunction with green fluorescent protein (GFP) fusion proteins, where the studied protein is fused to a GFP. When excited by a specific wavelength of light, the protein will fluoresce. When the protein that is being studied is produced with the GFP, then the fluorescence can be tracked.

• Photodestroying the GFP; and then watching the repopulation into the bleached area can reveal information about protein interaction partners, organelle continuity and protein trafficking.

• If after some time the fluorescence doesn't reach the inittel level anymore, then some part of the fluorescence is caused by an immobile fraction (that cannot be replenished by diffusion). Similarly, if ih

• This observation has most recently been exploited to investigate protein binding



7. Gene duplication leads to maximal evolution of:

a. r-Rna

b. m-Rna

c. t-Rna

d. hn-Rna

Answer: B. m-RNA

• Gene duplication is any duplication of a region of DNA that contains a gene; it may occur as an error in homologous recombination, a retrotransposition event, or duplication of an entire chromosome. The second copy of the gene is often free from selective pressure — that is, mutations of it have no deleterious effects to its host organism. Thus it accumulates mutations faster than a functional single-copy gene, over generations of organisms.

• A duplication is the opposite of a deletion. Duplications arise from an event termed unequal crossing-over that occurs during meiosis between misaligned homologous chromosomes. The chance of this happening is a function of the degree of sharing of repetitive elements between two chromosomes. The product of this recombination are a duplication at the site of the exchange and a reciprocal deletion,

• Gene duplication is believed to play a major role in evolution; this stance has been held by members of the scientific community for over 100 years.

• The duplication of a gene.results in an additional copy that is free from selective pressure. One kind of view is that this allows the new copy of the gene to mutate without deleterious consequence to the organism.

• This freedom from consequences allows for the mutation of novel genes that could potentially increase the fitness of the organism or code for a new function. An example of this is the apparent mutation of a duplicated digestive gene in a family of ice fish into an antifreeze gene.

• Another view is that both copies are equally free to accumulate degenerative mutations, so long as any defects are complemented by the other copy. This leads to a neutral "subfunctionalization" or DDC (duplication-degeneration-complementation) model, in which the functionality of the original gene is distributed among the two copies.

• The two genes that exist after a gene duplication event are called paralogs and usually code for proteins with a similar function and/or structure. By contrast, orthologous genes are ones which code for proteins with similar functions but exist in different species, and are created from a speciation event

• It is important (but often difficult) to differentiate between paralogs and orthologs in biological research. Experiments on human gene function can often be carried out on other species if a homolog to a human gene can be found in the genome of that species, but only if the homolog is orthologous. If they are paralogs and resulted from a gene duplication event, their functions are likely to be too different.

• The paralogous segments can be repeat sequences with more than 90% sequence similarity. In such cases, they are known as low copy repeats (LCRs) though they are not highly repetitive sequences. » They are mostly found in pericentronomic, subtelorneric and interstitial regions of a chromosome. The LCRs, due to their size (>1 Kb), similarity, and orientation, are highly susceptible to duplications and deletions.

• These genomic rearrangements are caused by the mechanism of non-a!!e!ic homologous recombination.

• The resulting genomic variation leads to gene dosage dependent neurological disorders such as Rett-like syndrome and Pelizaeus-Merzbacher disease. - -

8. Which of the following act on intra cytoplasmic receptor then act through nuclear protein

a. Growth hormone

b. Thyroxin

c. Epinephrine

d. ADH

Answer: B. Thyroxine

Reference: Harper 27th edition page 464 & 465

• Intracellular receptors, such as nuclear receptors and cytoplasmic receptors, are soluble proteins localized within their respective areas.

• The typical ligands for nuclear receptors are lipophilic hormones like the steroid hormones testosterone and progesterone and derivatives of vitamins A and D. To initiate signal transduction, the ligand must pass through the plasma membrane by passive diffusion.

• On binding with the receptor, the ligands pass through the nuclear membrane into the nucleus, enabling gene transcription and protein production.

• Activated nuclear receptors attach to the DNA at receptor-specific hormone-responsive element (HRE) sequences, located in the promoter region of the genes activated by the hormone-receptor complex. Due to them enabling gene transcription, they are alternatively called inductors of gene expression. Activation of gene transcription is slower than signals directly affecting existing proteins; therefore, the effects of hormones that use nucleic receptors are long-term.

• Signal transduction via these receptors involves little proteins, but the details of gene regulation by this method are not well understood. Nucleic receptors have DNA-binding domains containing zinc fingers and ligand-binding domain; the zinc fingers stabilize DNA binding by holding its phosphate backbone. DNA sequences that match the receptor are usually hexameric repeats of any kind: the sequences are similar but their orientation and distance differentiate them. The ligand-binding domain is additionally responsible for dimerization of nucleic receptors prior to Binding and providing structures for transactivation used for communication with the translational apparatus.

• Steroid receptors are a subclass of nuclear receptors located primarily within the cytosoj; in the.absence of steroids, they cling together in an aporeceptor complex containing chaperone or heatshock proteins (HSPs). The HSPs are necessary to activate the receptor by assisting the protein to fold in a way such that the signal sequence enabling its passage into the nucleus is accessible. Steroid receptors, on the other hand, may be repressive on gene expression when their transactivation domain is hidden; activity can be enhanced by phosphorylation of serine residues at their N-terminal as a result of another signal transduction pathway, a process called crosstalk.

• Retinoic acid receptors are another subset of nuclear receptors. They can be activated by an endocrine-synthesized ligand that entered the cell by diffusion, a ligand synthesised from a "precursor like retinol brought to the cell through the bloodstream or a completely intracellularly synthesised ligand like prostaglandin. These receptors are located in the,nucleus and are not accompanied by HSPs; they repress their gene by binding to their specific DMA sequence when no ligand binds to them and vice versa.

• Certain intracellular receptors of the immune system are cytoplasmic receptors; recently identified NOD-like receptors (NLRs) reside in the cytoplasm of some eukaryotic cells and interact with ligands using a leucine-rich repeat (LRR) motif similar to TLRs. Some of these molecules like NOD2 interact with RIP2 kinase that activates NF-. B signaling, whereas others like NALP3 interact with inflammatory caspases and initiate processing of particular cytokines like interleukin-1p.



Thyroid Hormone Receptors and Mechanism of Action:

• Receptors for steroid and thyroid hormones are located inside target cUk, in the cytoplasm or nucleus, and function as ligand-dependent transcription factors. Receptors for thyroid hormones are intracellular DNA-binding proteins that function as hormone-responsive transcription factors, very similar conceptually to the receptors for steroid hormones,

• Thyroid hormones enter cells through membrane transporter proteins. A number of plasma membrane transporters have been identified, some of which require ATP hydrolysis; the relative importance of different carrier systems is not yet clear and may differ among tissues.

• Once inside the nucleus, the hormone binds its receptor, and the hormone-receptor complex interacts with specific sequences of DNA in the promoters of responsive genes. The effect of the hormone-receptor complex binding to DNA is to modulate gene expression, either by stimulating or inhibiting transcription of specific genes,

• For the purpose of illustration, consider one mechanism by which thyroid hormones increase the strength of contraction of the heart. Cardiac contractility depends, in part, on the relative ratio of different types of myosin proteins in cardiac muscle. Transcription of some myosin genes is stimulated by thyroid hormones, while transcription of others in inhibited. The net effect is to alter the ratio toward increased contractility.



9. Apo B48, B100 belongs to same RNA, difference between them is due to

a. mRNA splicing

b. Chemical changes in mRNA & splicing

c. Differetial RNA processing

d. Upstream regression

Answer: The correct answer is RNA editing. None of the option matches the answer. Similar answer out of following can be Chemical changes in mRNA after splicing (option B) check for typographic errors

• Chylomicrons are assembled in the enterocytes, and consist of droplets of non-polar lipid, triacylglycerol (TAG) and cholesterol esters, stabilized by a shell of phospholipid, cholesterol and protein.

• The major protein is apolipoprotein (apo)-B48, "which is essential for the assembly, secretion and subsequent metabolism of Chylomicrons.

• apo-B48 is a truncated form of apo-BlOO, and is produced by post-transcriptional editing of the mRNA for apo-8100.

• Cytidine 6666 is deaminated by an RNA-editing enzyme, apobec-1, resulting in the production of a stop codon after 48% of the mRNA has been translated. This change generates an in-frame stop codon at amino acid 2153 and results in synthesis of a 2152-amino acid product (apoB-48), ;

• The C to U nucleotide substitution in the apoB mRNA is a co- or post-transcriptionai event and is not present in the apoB gene. The editing enzyme is expressed in the enterocytes of all mammals investigated, and is regulated developmental in human fetal intestine

• Thus RNA editing is a molecular process in which the base of a RNA molecule is altered by specific enzymes. In the following example, Cytosine (C) is changed to Uraci! (U).

Figure shows: RNA editing of the apo-B gene. In mammals, the apo-B gene is expressed in both hepatocytes (liver cells) and intestinal epithelial ceils. However, in liver cells, its product is a 500 kD protein called Apo-B10Q whereas in intestine cells its product is a smaller protein called Apo-B48. The Apo-B100 is produced without RNA editing, but the Apo-B48 is synthesized from an mRNA whose sequence has been altered by a specific enzyme. This enzyme changes a codon, CAA, in the middle of the original mRNA to the stop codon UAA, thereby causing early termination of the protein synthesis.



10. By which of the following actions GS receptor can be stimulated to induce watery diaorrhea

a. Phosphorylation

b. Dephosphorylation

c. ATP-ADP exchange

d. ADP ribosylation

Answer: The answer can be Cyclic AMP if it is option or ribosylation of G regulator protein. Please check for any typographic errors.

• The cholera toxin (CTX or CT) is an oligomeric complex made up of six protein subunits: a single copy of the A subunit (part A), and five copies of the B subunit (part 8), connected by a disulfide bond.

• The five B subunits form a five-membered ring that binds to GM1 gangliosides on the surface of the intestinal epithelium cells.

• The A1 portion of the A subunit is an enzyme that ADP-ribosylates G proteins, while the A2 chain fits into the central pore of the B subunit ring. Upon binding, the complex is taken into the cell via receptor-mediated endocytosis.

• Once inside the celt: the disulfide bond is reduced, and the A1 subunit is freed to bind with a'human partner protein called ADP-ribosylation factor 5 (ArfG). –

• Binding exposes its active site, allowing it to permanently ribosylate the Gs alpha subunit of the heterotrimeric G protein. This results in constitutive cAMP production, which in turn leads to secretion of H20, Na+,



K+, CI-, and HC03- into the lumen of the small intestine and rapid dehydration. Thus in the small intestine, cholera toxin acts by ADP - ribosylation of the G regulatory protein.

Reference: Harper's Biochemistry, 24th Edition, Pg. 514-515



11. Acetyl CoA can be converted into all of the following except

a. Glucose

b. Fatty acids

c. Cholesterol

d. Ketone bodies

Answer: A. Glucose

Ref" Harper's Biochemistry, 27th Edition Pfr 132-136

• Acetyl coenzyme A or acetyl-CoA is .*n important molecule in metabolism, used in many biochemical reactions. Its main function is to convey the carbon atoms -.vithin the acety! group to the citric acid cycle to be oxidized for energy production.

• In chemical structure, acetyi-CoA is the thioester between coenzyme A (a thiol) and acetic acid (an acyl group carrier). Acetyi-CoA is produced during the second step of aerobic cellular respiration pyruvate decarboxylation, which occurs in the matrix of the mitochondria. Acetyl-CoA then enters the citric acid cycle.

• Acetyl-CoA is also an important component in the biogenic synthesis of the neurotransmitter acetylcholine. Choline, in combination with acetyi-CoA, is catalyzed by the enzyme choline acetyitransferase to produce acetylcholine and a coenzyme a byproduct.

• In animals, acetyl-CoA is essential to the balance between carbohydrate metabolism and fat metabolism (see fatty acid synthesis). In normal circumstances, acetyl-CoA from fatty acid metabolism feeds into the citric acid cycle, contributing to the cell’s energy supply.

• In the liver, when levels of circulating fatty acid are high, the production of acetyl-CoA from fat breakdown exceeds the cellular energy requirements. To make use of the excess acetyl-CoA, ketone bodies are produced, which can then circulate in the blood

• In some circumstances, this can lead to the presence of very high levels of of ketone bodies in the blood, a condition called ketosis. Benign dietary ketosis can safety occur in people following low-carbohydrate diets, which cause fats to be metabolized as a major source of energy. This is different from ketosis brought on as a result of starvation, and from ketoacidosis, a dangerous condition that can affect diabetics

• Because of irrevarsible nature of pyruvate deydrogenase complex, acetyl CoA cannot be converted to pyruvate and therefore glucose cannot be synthesized





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MICROBIOLOGY

1. Most common organism associated with cystic fibrosi

a. Pseudomonas aeruginosa (non mucoid)

b. Burkholderia cepacia

c. Pleisomonas

d. Aeromonas - -

Ans- B. Burkholderia cepacia

Ref-Mandell, Douglas and Bennnet's Principles and Practice of Infectious diseases, 6th ed., pg 869-872

• Cystic fibrosis (CF) is a clinical syndrome that reflects an autosomal recessive genetic disorder characterized by a mutation in the CF gene located on the long arm of chromosome 7.

• It is a large gene that codes for a 1480-amino acid polypeptide known as cystic fibrosis transmembrane regulator (CFTR) which is a cyclic AMP - regulated chloride channel in the plasma membrane that also regulates the activity of other ion channels in the plasma membrane.

• The most common gene mutation is a 3-base pair deletion that leads to absence of phenylalanine in the CFTR protein at position 508.

• This leads to abnormal folding of the protein in the ER followed by its degradation, reflected as absence of protein at the relevant site in the plasma membrane. Other less common mutations allow the transport of CFTR to the plasma membrane but lead to abnormal channel regulation.



Two major defects occur at the cellular level in CF:

A. Defective CFTR Chloride channel function has been detected in the airways, sweat ducts and small intestine.

B. Ion transport defect in the airways- rate of absorption'of sodium ions from the airway lumen to the interstitium is raised three-fold.



Ion transport abnormalities appear to deplete the amount of water on airway surfaces which leads to:

A. Periciliary liquid layer is depleted, hence failure of cilia dependent mucus clearance and decrease in the lubricant that prevents the mucus layer from adhering to the airway surface

B. Mucins in the mucus are concentrated, making it adhere more tenaciously to airway surfaces.



The thickened, adherent mucus and plugs are not cleared by cough mechanisms and become the nidi for initial airway infection that characterize lung disease in CF. The most common bacteria associated are S. aureus (-30%), P. aeruginosa (-80%) and Burkholderia cepacia (-10%). The reason for the selective selection of these bacteria is not known.

A. Small-colony variants of S. aureus are increasingly been recognized in CF patients. These auxotrophic (thymidine-dependent), slow-growing and antimicrobial resistant are believed to evolve in the CF. airway following long term antibiotic therapy and are believed to play a role in persistence of S. aureus. These strains grow well only on rpannitoi salt agar and poorly on routine bacteriological media.

B. In childhood or early adolescence, CF patients become chronically infected with P. aeruginosa, either by environmental strains or cross- infections from CF/ non-CF individuals. As this infection evolves., isolates produce large amounts of extracellular mucoid polysaccharide called alginate. The thickened mucus coat overlying the CF airway contains hypoxic regions (hostile for the bacterium), leading to adaptation of the strains to nonmotile, anaerobicaliy respiring, mucoid variants growing as a biofilm that leads to formation of microcolonies. These are highly resistant to antimicrobials and immunological clearance. Mucoid colonies are rarely seen in P. areuginosa isolates with other airway diseases except older patients with primary ciliary dyskinesia.

C. As life expectancy of CF patients has increased, Burkholderia cepacia has emerged as an important pathogen and is recovered from -10% of adults with CF. Some infected patients develop what is described as cepacia syndrome. In this, young adults with CF and relatively mild pulmonary disease become infected, have rapid deterioration of function and die within 6 months.



Other bacteria such as Hemophilus infiuenzae, Moraxella catarrhalis, NTM, Stenotrophomonas maltophila and Aikaligenes sp. are also recovered from the respiratory tract of CF patients.



Plesiomonas is a gram negative motile bacillus in the family Vibrionaceae but more closely related to the genus Proteus. P. shigeiloides is the only species in the genus. It is facultatively anaerobic, oxidase positive, readily isolated on enteric agars like MacConkey's agar but does not grow on TCBS. It is a water- and soil-associated organism and the usual vehicles of transmission to humans are water, food such as oysters, shrimps, or chicken and a variety of other animals that may be colonized with the bacterium. It is implicated as a cause of diarrhea and rarely serious exttaintestinal disease like osteomyelitis, septic arthritis, spontaneous bacterial peritonitis and neonatal sepsis. Usually susceptible to chloramphenicol, quinoiones, cephalosporins and imipenem.



2. Streptococcus all are true,

a. Streptodornase cleaves DNA

b. Streptolysin 0 is active in reduced state

c. Streptokinase is produced from serotype A, C, K

d. Pyrogenic toxin A is plasmid mediated

Ans. D. Pyrogenic toxin A is plasmid mediated

Ref- Ananthanarayan and Paniker's Textbook of microbiology, 8th ed., pg 204-16.

• Beta hemolytic streptococci are classified on the basis of C carbohydrate antigen into 20 groups, A to W. Group A (S.pyogenes) are responsible for almost 90% of human infections due to streptococci. S.pyogenes forms several exotoxins and enzymes which contribute to its virulence, along with the M protein, C polysaccharide, hyaluronic acid capsule and teichoic acids.

• Hemolysin 0 and S: Streptolysin 0 is oxygen labile which is inactive in the oxidised state not in reduced state. Hemolysis produced by it is evident only in pour plates not in surface cultures. It is antigenic and ASO titers are most commonly used for the retrospective diagnosis of streptococcal infections. Streptotysin S is an oxygen stable hemolysin and so responsible for hemolysis seen around surface colonies of S.pyogenes. Hemolysin 0 and S are produced by streptococcal groups C and G also.

• Pyrogenic toxin is also called Erythrogenic or Dick or scadatiniform toxin. Primary effect of this toxin is induction of fever. Streptococcal pyrogenic toxins ( SPE) A,B and C are superantigens which have the ability to stimulate large no. of T cells by nonspecific binding to the Vp region of T cell receptor, inducing massive release of inflammatory cytokines. Types A and C are bacteriophage coded and type B gene is chromosomal.

• Deoxyribonucleases produced by Streptococcus are called streptodornase. This enzyme depolymerises DNA and helps to liquefy the thick pus of pyogenic exudates and may be responsible for the thin serous character of streptococcal exudates. A preparation of streptodornase and Streptokinase is available for this application of this ability in liquefying localised collections of thick exudates such as empyema. 4 antigenically distinct DNAases have been recognised, of which type B is most antigenic. Demonstration of anti-DNAase B has been used for retrospective diagnosis of S. pyogenes "infection, especially skin infections, where ASO titers may be low.

• Streptokinase or fibrinolysin promotes the lysis of human fibrin clots by activation of plasminogen. It is believed to play a role in spread of streptococcal infections by breaking down fibrin barrier around the lesions. It is also produced by streptococcal groups C and K. S.equisimilis is the source of Streptokinase used for thrombolytic therapy in patients,

• Other enzymes produced include hyaluronidase, NADase, serum opacity factor, proteinase, phosphatase, esterase, amylase and neuraminidase. "



3. Lymes disease, all are true, except

a. Borrelia burgdorferi replicates locally and invades locally

b. Infection progresses inspite of good humoral immunity

c. Polymorphonuclear leukocyrosis in CSF suggest meningeal involvement]

d. lgA intrathecally confirms meningitis

Ans. C. Polymorphonuclear leukocytosis in CSF suggest meningeal involvement

Ref- Mandell, Douglas and Bennnei's Principles and Practice of Infectious diseases, 6th ed.3 pg 2798-280?

Koneman's Color atlas and Textbook of Diagnostic Microbiology, 6th ed., pg 1135-43



Lyme's disease or Lyme borreliosis is caused by the spirochete Borrelia burgdorferi sensu stricto, 8, garinii and B.afzelii, transmitted to humans by the bite of an infected tick (nympha! stage). It is the most common vector borne disease in the northern hemisphere and its distribution matches the distribution of the Ixodid ticks. The cycle is



maintained in nature by a number of small rodents especially white-footed mouse, which act as asymptomatic reservoirs. Although deer are not directly involved in transmission, they are important for survival of ticks. The tick needs to be attached for at least 24 hrs to transmit disease.



After injection into human skin, the borreliae multiply locally and migrate outwards, producing the primary lesion and may spread hematogenously. Spread through the skin and other tissue matrices is aided by binding to certain host integrins, giycosaminoglycans and extracellular matrix proteins. ' - . .



Due to its protean manifestations Lyme's disease is called *ths new great imitator'. As in -syphilis, the manifestations can be cataloged into 3 stages:



• Stage I is the stage in which the tick bite elicits the classic lesion, erythema chronicum migrans (EM). This is seen after an incubation period of 3-32 days, during which the spirochete multiplies locally and then spreads peripherally.

• The lesion is red, and may be warm, but is generally painless. Classically, the innermost portion remains dark red and becomes indurated; the outer edge remains red; and the portion in between clears, giving the appearance of a bull's eye. Regional lymphadenopathy, malaise and fatigue may accompany the EM lesion.

• Stage II is the stage of disseminated disease due to iiernaiogenous dissemination. vViihin several days 10 weeKo of EM, patients develop multiple secondary annular skin lesions which resemble the EM lesion along with generalized lymphadenopathy and intermittent migrating arthralgias and myalgias. About 15-20% of untreated patients develop meningitis, encephalitis, cranial neuritis, motor and sensory radiculoneuritis, cerebellar ataxia- alone or in combinations.

• Patients with meningitis show a lymphocytic pleocytosis of about 100 cells/cumm with an elevated protein and normal glucose level in the CSF. Specific IgG, IgM or IgA antibodies are produced intrathecally.

• About 5% of patients show fluctuating degrees of atrio-ventricular blocks and acute myopericarditis.

• Conjunctivitis is the most common eye abnormality, though deeper tissues of eye may be involved.

• Stage III starts months after the onset, manifesting most commonly as intermittent attacks of joint swelling and pain, primarily in large joints, especially knee. Attacks of arthritis last from few weeks to months separated by periods of complete remission. Joint fluid contains primarily PMN's. About 10% of untreated develop chronic arthritis (1 yr or more of continuous inflammation). However, even untreated, arthritis resolves completely in several yrs.

• 5% of patients develop chronic axonal polyneuropathy (radicular pain or paresthesia) and chronic encephalomyelitis (spastic paraparesis, ataxia, cognitive impairment or crania! neuropathy). There are no inflammatory changes in the CSF but intratheca! antibody production to the spirochete can often be demonstrated.

• Acrodermatitis chronic atrophicans are red, violaceous lesions which may last for several yrs.



During disseminated infection, antibodies are produced against many components of the organism especially plasmid-coded outer-surface proteins (Osp) A through F. Despite an active immune response, the organism can survive for several years in joints, skin or nervous system. This is due to its ability to downregulate the expression of surface protein antigens and antigenic variation in a surface lipoprotein V1sE



Diagnosis-

• It mainly clinical if characteristic EM lesion is present. B.burgdorferi can be cultured in a cell free liquid medium - Barbour-Stoenner-Kelly medium from early lesions. Demonstration of spirochetes by silver stains and by amplification techniques in skin lesions, peripheral blood and joint fluid can also be used.

• The diagnostic method of choice is serologic analysis. An enzyme immunoassay or immunofluorescence assay is used as the initial test. Positive results should be confirmed with immunoblot assay for IgM and IgG. Serodiagnosis is insensitive during first one or two weeks of infection.

• IgM is the first antibody to appear. After one month, almost all patients with active infection have positive IgG antibody.

• A positive IgM test alone after month of illness is likely to be a false positive result. Acute neuroborreliosis can be demonstrated by intra-thecal production of IgM, IgG and IgA antibodies but this test is less often positive in chronic neuroborreliosis.

• After antibiotic treatment antibody titers decline slowly and IgG and even IgM may persist for many yrs.



4. Which of the following statement is true about bacteriophage

a. It is a bacterium

b. It helps in transformation

c. It imparts toxigenicity to bacteria

d. It transfers only chromosomal gene

Ans. C. It imparts toxigenicity to bacteria

Ref-Topley & Wilson's Microbiology and Microbial infections, 10th ed; pg 139-143 Ananthanarayan and Paniker's Textbook of microbiology, 8th ed., pg 63-64,455-60

• Bacteriophages are viruses that grow in bacterial cells utilizing their biosynthetic systems for reproduction. Their effects were first observed by Twort, who described an infectious agent that distorted the morphology of staphylococcal colonies. ?

• They are readily detectable for most bacterial species and probably all bacteria are sensitive to one or more phage. Most phages show host specificity- specific to a genus/species/strain/biotype. Host specificity is determined at the step of adsorption of phage on to the susceptible bacterium, depending on the presence of complementary chemical groups on the receptor sites of the bacterial surface and attachment site on the phage.

• Phages occur widely in nature in association with bacteria, readily isolated from feces, sewage, water and soil. The population density of the host bacterium is a major determinant of density and distribution of phage. Bacterial mortality due to -phage reproduction suggests they may have a role in control of bacterial populations.

• Show considerable morphological diversity. Some are filamentous, isometric, and superficially resemble animal viruses, while others show complex morphologies. Majority of the phages have a double stranded DNA, though a few may have single-stranded DNA or RNA.



Exhibit two different life cycles:

• Virulent life cycle- following adsorption, penetration and multiplication in host bacterium, the host cell lysis culminating in the release of progeny phages. This is called lysis from within. During this cycle, the bacterial metabolism ceases. Eclipse phase interval oetween enny dnu appearance oijirsi iniectious pnage particle intraceliuiariy. Latent period: interval between infection and first release of infectious phage particles. Burst size: average yield of progeny phages per infected bacterial cell. f If large number of phages are mixed with relatively lesser number of bacteria, multiple holes may be produced at the site of penetration of phages leading to leakage of cell contents. Lysis occurs without viral multipfication. This is called lysis from without.

• Lysogenic or temperate life cycle- the host bacterium remains unharmed and the phage DNA becomes integrated with the bacterial chromosome as a prophage, behaves like a segment of host chromosome and replicates synchronously with it. The bacterium that carries a prophage in its genome is called a lysogenic bacterium. The phage genes expressed in this dormant state code for proteins that repress the expression of other phage genes (structural and lysis genes) in order to prevent entry into the lytic cycle.

• The prophage confers some new properties on its iysogenic bacterium due to the synthesis of new proteins coded for by the prophage DNA. An example is the lysogenic conversion in diphtheria bacilli, which acquire toxigenicity by lysogenisation with the phage beta. A lysogenic bacterium is resistant to reinfection by the same or related phages. This is called superinfection immunity. Lysogeny is extremely frequent in nature.

• During multiplication of lysogenic bacteria, the prophage may get excised which then initiates lytic replication and the daughter phage particles are released. These then infect other bacterial cells and r-ender them lysogenic. This is called spontaneous induction of prophage. Though rare in nature, a lysogenic phage can be induced to shift to the lytic cycle by exposure to physical and chemical agents like UV rays, hydrogen peroxide and nitrogen mustard. In these conditions, the host cell is stressed, resulting in expression of repressed phage genes.

• Packaging errors may occur occasionally during assembly of progeny phages. A phage may have in its core a segment of host DNA (Chromosomal or plasmid DNA) along with its own nucleic acid. When this phage infects another bacterium, DNA transfer is effected and the recipient cell acquires new characteristics coded by the donor DNA. This is called transduction. Transduction may be generalized when it involves any segment of the donor DNA at random or may be restricted, when only a specific segment is transduced.



5. Lambda phage which is true

a. It causes madcow disease

b. Lytic & lysogenic conversion can not occur together

c. In Lysogenic phase host chromosome and remains dormant

d. Lytic phase incorporates in host DNA, proliferate & causes rupture of cell

Ans- B. Lytic & lysogenic. conversion can not occur together

Ret- Topley & Wilson's Microbiology and Microbial Infections, 10th ed; pg 104-106

• Lambda phage is dsDNA phage of E.coli discovered by Lederberg in 1950, It shows 2 types of cycles- lytic or temperate.

• In lysogenic cycle it gets inserted only between the genes determining galactose utilization and biotin utilization due to the presence of site specific recombinase. On induction of the lytic cycle, as discussed in Ques 4, the integration is reversed and the phage genome is excised at the same site as the integration.

• Occasionally, however, excision process occurs between two sites other than the normal attachment regions of the phage and host DNA, usually one within the prophage and one just outside,

• The consequence is that a ring of DNA is excised that contains primarily of lambda genes and a few host genes from either side of the attachment site.

• This hybrid DNA can be packaged in a lambda head and released, where it is able to infect a further eel! and inject into it DNA that contains some host genes. This is an example of specialized transduction.



6. All are true about brucella excep

a. B. abortus is capnophiiic

b. Transmission by aerosol can occur occasionally

c. Pasteurisation destroys it

d. 2 ME is used to detect IgA

Ans- D. 2 ME is used to detect IgA

Ref- Ananthanarayan jnd Paniker's Textbook of microbiology, 8th ed., pg 341-45

• Brucellosis is also called Mediterranean/Malta'undulant/Cyprus fever/Bang's disease. It is a zoonotic disease caused by B. melitensis, B.aborts and B.suis: reservoir hosts of which are sheep/goats, cattle and pigs; respectively.

• Brucella melitensis is the most prevalent worldwide, and it is felt to cause the most severe cases of brucellosis.

• The species identification is very complex and is based on the relative proportions of 2 antigens, A and M, along with C02 requirement, H2S production, urease enzyme, phage lysis (Tblisi phage) and sensitivity to dyes. Many strains of Brucella abortus are capnophiiic (grow better in the presence of 5-10% carbon dioxide).

• Brucella possesses a number of antigens which cross react with Yersinia emerocoHiica, Vibrio choleras, E. coll, Strenotrophomonas maltophiia and group N Salmonella.

• Bruceilae are destroyed by heat at 60C in 10 min. They are killed by pasteurization. They resist drying and may survive in soil for long periods. They survive for many weeks in meat

• Transmitted via skin by direct contact with infected tissues, inhalation of aerosolised bacferta, ingestion of contaminated meat, unpasteurized milk or milk products.

• Bruceila is primarily an intracelluiar pathogen affecting the rqjiculoendothelial system. They spread from the initial site of infection to the local lymph nodes, where they multiply, spill over to the- blood stream and disseminate throughout the body. Tissue reaction to brucelia consists of granuloma formation.

• Diagnosis depends either on isolation of the organism or on aerology. Blood culture is the most definitive meinccl for diagnosis.

• The Castaneda's method (biphasic) has several advantages and is recommended. Blood cultures are positive only in 30-50% cases. Bone marrow, lymph nodes, CSF, urine and abscesses can also be used for culture.

• Cultures are often unsuccessful. Several serological tests are used in diagnosis. In brucellosis, both IgM and IgG antibodies appear in 7-10 days after onset. As disease progresses, IgM antibodies decline, while IgG antibodies persist or increase in titre.

• Standard agglutination test (SAT) is a tube agglutination test in which a titre more than 160 or more is considered significant. It detects IgM antibodies effectively, which tend to decline after the acute phase of illness. As the prozone phenomenon is very frequent in brucellosis, it is essential to test several serum dilutions,

• 2-mercapto ethanol selectively destroys IgM by breaking the disulfide bonds and hence 2-ME agglutination test is used to detect IgG antibodies, as they are the best indicators of active infection especially in patients with a long history of symptoms and also prognostic indicator following therapy. It can also be used for diagnosis of relapse. This test also is used to diagnose cross-reacting antibodies produced in cholera infections and Y. enterocolitica infections.

• IgG antibodies may act as blocking or incomplete antibodies. These can be detected by prior heating of serum at 55C for 30 min or by using 4% saline as diluent or by the direct Coomb's test.

• ELISA and complement fixation tests can detect IgM and IgG antibodies and therefore useful for differentiation between acute and chronic brucellosis.



7. All are true about non typhoid salmonella except

a. Poultry is source

b. Can cause invasive disease in neonates

c. Blood culture is more sensitive than stool culture in gastroenteritis in adults

d. Resistance to FQ has emerged

Ans- C. Blood culture is more sensitive than stool culture in gastroenteritis in adults

Ref-Mandell, Douglas and Bennnet's Principles and Practice of Infectious diseases, 6th ed., pg 2637-50

Ananthanarayan and Paniker's Textbook of microbiology, 8th ed., pg 299-300

Salmonella is a genus of the family Enterobacteriaceae. It is divided into 2 species: Salmonella enterica (subsp-enterica, salmae, arizonae, diarizonae, houtenae and indica) and Salmonella bongori. Members of the subspecies are serotyped into almost 3000 serotypes according to somatic (0), surface (Vi), and flagellar antigens.



Some salmonella serotypes such as S.Typhi and S.Paratyphi that cause enteric fever are highly adapted to humans and have no other known natural hosts. Hence infection occurs only by ingestion of food or water contaminated with human feces.



Other serotypes (also called nontyphoidal salmonella) are commensals or pathogens in wide spectrum of animals like reptiles, birds, and domestic animals. Some like S.Typhimuriurn have a wide host range while others like S.Dublin are restricted to cattle. All these serotypes are potentially pathogenic to humans and can cause gastroenteritis, septicemia with localized suppurative infections.



Salmonella gastroenteritis (GE) or food poisoning is generally a zoonoses, the source of infection" being animal products. Most common serotypes implicated are S.Typhimurium and S. Cholerasuis. The most frequent sources are poultry, meat, contaminated raw salads/ vegetables, unpasteurized milk and milk products. Salmonellae can enter egg shells if eggs are left on contaminated chicken feed or feces, and grow inside. Role of human carriers is minimal.



Following infection, Salmonella express an array of fimbriae that help to adhere tightly to intestinal mucosa following which there is an invasive enterocolitis. Within 6-48 hrs, disease manifests with diarrhea, vomiting, abdominal pain and fever that is usually self limited in 2-4 days, Bacteremia occurs occasionally in serotypes S.Cholerasuis and S.Dublin, though any serotype can cause it. From 1-4% of immunocompetent individuals with salmonella GE have positive biood cultures, Risk is greater in infants, elderly and immunocompromized.



Lab diagnosis depends on the isolation of salmonella from the feces by using selective media like xylose lysine deoxycholate agar or Hoektoen enteric agar or Salmonella shigella agar. In addition to plating the stool onto primary media, ietrathionaie-based or selenite-based enrichment broths can be used to facilitate recovery of small numbers of organisms. Isolation of the causative organism form the article of food confirms the diagnosis.



Antimicrobial resistance among non-typhoidal salmonella isolates is increasing worldwide. Multidrug-resistant strains have also emerged conferring resistance to at least 5 antimicrobials- ampiciliin, chioramphenicoK streptomycin, sulfonamides and tetracyclines. Quinolone-resistant strains have emerged due to intracellular mutations of intracellular targets DNA gyrase or topoisomerase IV or to overproduction of efflux pumps. Non-typhoidal Salmonella resistant to 3rd generation cephalosporins have also been reported.



8. Which of the following statements about vaccines is false

a. Thiomersal is preservative in DPT vaccine

b. Magnesium chloride is stabilizer used in OPV

c. Kanamycin is preservative in measles

d. Neomycin is preservative in BCG vaccine

Ans- D. Neomycin is preservative in BCG vaccine Ref-www. merck.com/product/ http://www.seruminstitute.com/content/products

www.panaceabiotec.com/product .



DPT vaccine- Diphtheria, Tetanus and Pertussis Vaccine (Adsorbed) is a sterile, whitish turbid, uniform suspension of diphtheria and tetanus toxoids and pertussis vaccine adsorbed on aluminium phosphate and suspended in isotonic sodium chloride solution. Each dose of 0.5 ml contains:



Diphtheria Toxoid . < 25 Lf.

Tetanus Toxoid > 5 Lf.

B. Pertussis > 4IU

Adsorbed on Aluminium Phosphate > 1.5 mg.

Thiomersal . 0.01% as preservative.



For the purpose of primary immunization it is recommended that 3 doses each of 0.5 ml should be inoculated on 3 separate occasions at 4 weeks interval. The first dose should be given at approximately 6 weeks of age. Reinforcing injections of 0.5 ml should be given 12 months after the primary immunization and also between the ages of 4 to 6 years. DPT vaccine should be administered by deep intramuscular injection. The preferred site for injection is the anterolateral aspect of the upper thigh.



OPV vaccine- is a trivalent vaccine containing suspensions of types 1 , 2 and 3 attenuated poliomyelitis viruses (Sabin strains)



prepared in monkey kidney cells. Each dose contains not less than virus concentration per dose 106 TCID50 of type



type 2 and 106 TCID50 of type 3. MCI2 is used as a stabilizer and phenol red as indicator. During formulation of OPV trace



amounts of antibiotics: Kanamycin and Neomycin sulphate are added.

WHO recommends the following schedule in endemic countries: Birth, 6, 10, 14 weeks. The vaccine comes in vials of 20 doses. Two drops are delivered directly into the mouth of vaccinee from the multjdose vial by dropper or dispenser

Measles vaccine is a sterile lyophilized preparation of live attenuated measles virus, derived from Enders1 attenuated Edmonston strain and propagated in chick embryo cell culture; it contains SPGA (sucrose, phosphate, glutamate, and recombinant human albumin) as stabilizer and 50 meg of neomycin and kanamycin. The diluent is sterile water (0.5 ml). The reconstituted vaccine is to be used immediately. Given subcutaneously, preferably in

the outer aspect of upper arm. Recommended age is 12-15 months.



BCG vaccine- BCG Vaccine is a live freeze-dried vaccine derived from live attenuated strain of Mycobacterium bovis (Bacillus Calmette Guerin). BCG Vaccine vial is reconstituted with 0.5 ml of sodium chloride injection. After reconstitution it should be used immediately. If the vaccine is not used immediately then it should be stored in the dark at 2° to B" C for no longer 6 hours. The vaccination dose is 0.05 ml for children under one year of age including the new bom, of the reconstituted vaccine given intradermally. The skin should not be cleaned with antiseptic. The vaccine should be preferably given with a tuberculin syringe. The vaccine can be given simultaneously with DTP. DT, TT, Measles, Polio and Hepatitis B vaccines^ but at a separate site.



9. All are true regarding disinfectants except

a. Glutaraldehyde is sporicidal

b. Hypochlorites are virucidal

c. Ethylene oxide is intermediate disinfectant

d. Phenol acts in the presence of organic matter

Ans- C. Ethylene oxide is intermediate disinfectant

Ref- CDC's Guideline for Disinfection and Sterilization in Healthcare Facilities, 2008



High-level disinfectants -destroy all microorganisms, with the exception of high numbers of bacterial spores. Eg. Ethylene oxide, aldehydes and plasma



Intermediate-level disinfectants - inactivate even resistant organisms such as Mycobacterium tuberculosis, as well as vegetative bacteria, most viruses, and most fungi, but do not necessarily kill bacterial spores. Phenols and halogens.

Low-level disinfectants - kill most bacteria, some viruses, and some fungi; but cannot be relied on to kill resistant microorganisms such as tubercle bacilli or bacterial spores. Eg. Alcohols, dyes and quarternary ammonium compounds.

Of the commonly used chemical disinfectants, phenols and aldehydes are active in the presence of organic matter.

10. AcelMar pertusis vaccine contains

a. Pertactin, fimbria! hemagglutinin, cytotoxin, endotoxin

b. Pertactin, fimbria! hemagglutinin, fimbriae, pertussis toxin

c. Pertactin, cytotoxin, fimbriae, pertactin

d. Cytotoxin, fimbrial hemagglutinin, pertussis toxin

Ans- B. Pertactin, fimbrial hemagglutinin, fimbriae, pertussis toxin

Ref- Mandetl, Douglas and Bennnet's Principles and Practice of Infectious diseases, 6tt! ed., pg 2701-06

Ananthanarayan and Paniker's Textbook of microbiology, 8th ed., pg 335-39

• B.pertussis produces a number of biologically active substances that are postulated to play a role in disease. These include surface components such as filamentous haemagglutinin (FHA), pertactin and fimbriae; toxins such as pertussis toxin (PT), adenylate cyclase toxin (ACT), tracheal cytotoxin(TCT) and dermonecrotoxin (DNT).

• Roles for these factors can be considered in the context of a generic sequence of events for an infectious disease: entry and attachment to a specific target tissue, production of local damage, and development of systemic disease.

• FHA, pertactin, surface agglutinogens on fimbriae and possibly PT participate in attachment of B.pertussis to the respiratory epithelium. Ciliostasis and damage to the epithelium by TCT and DNT disturb mucociliary clearance, the first line of defense. The inhibition of function of phagocytes by ACT and PT represent an acute but reversible disruption of the protection conferred by immune effector cells.

• Specific immunization with killed B.pertussis has been found very effective, usually administered as an alum adsorbed vaccine combined with diphtheria and tetanus toxoid. A major limitation to whole-cell vaccine has been the associated reactogenicity. When compared with DT and TT, DPT vaccines produce significantly more local and systemic reactions such as pain, swelling, fever, anorexia, vomiting, convulsions, hypotonic-hyporesponsive episodes and encephalopathy with permanent neurological sequelae. These adverse effects are more often when given to older children and hence routine pertussis vaccination is not advisable in chidren over the age of 7 yrs.

• Acellular pertussis vaccine containing two or more protective components (FHA, PT, pertactin, Fimbiael agglutinins) are now used in several countries as they cause fewer reactions especially when give to older children.







RE\IE\\ OP .4/W5 \UY2W1

Pathology

1. All of the following genes may be involved in development of carcinoma of colon exce

a. APC

b. Beta – catenin

c. K-ras

d. Mismatch repair

Ans. None (all above genes may be involved) > Beta - catenin

Ret. 'Gastrointestinal and Liver disease1 by Feldman 8th 12768 'Neoplasms of the Colon, Rectum andAnus'2nd/58

APC, K- ras and mismatch repair genes are characteristically involved in generation of cancer of colon.

p Catenin mutations are uncommon / infrequent mutation seen in a subset of patients who have normal APC. Tumor lacking APC action mutation may have activating mutation in (3 catenin which is the main downstream target of APC action.

Genes involved in development of colorectal cancer



Extra Edge:

Beta-catenin is signal transducing protein which .-acts bn rjrotOrdtidbgehe, c-rnyc causing cell proliferation. APC is a tumour suppressor gene & has an inhibitory control on the action of beta-catenin. The proteins; from K-ras gene along with GTP-GDP act ^s irnporiant signal transducing pathway.



Important Points

i. P Catenin is the main downstream target of APC actin,

ii. APC functions to modulate extracellular signals that are transmitted to the nucleus through a cytokeleta! protein p -catenin' which then regulates transcription and other target genes.

iii. APC is a tumor suppressor gene that bind to p- catenin and causes its degradation unopposed stimulation of various pathways that lead to tumor genesis

iv. Besides inactivating mutations of APC gene, tumor genesis can also occur directly though dominant stimulatory mutations of the p- catenin gene. Such mutation are found in 15-20% of Microsateilite Instability colon cancers.



2. 45 year old male had severe chest pain and was admitted to the hospital a diagnosis of acute myocardia! infarction. Four days later he died and autopsy showed transmural coagulative necrosis. Which of the following microscopic features wiii be seen on further examination

a. Fibroblasts and collagen

b. Granulation tissue

c. Neutrophilic infiltration surrounding coagulative necrosis

d. Granuiomatous inflammation

Ans, C. Neutrophilic infiltration surrounding coagulative necrosis

Ref. Robbins 8th sdition Chapter 11 Table 11-2

Table 11-2. Evolution of Morphologic Changes in Myocardial infarction





Time Gross Features Light Microscopic Finding

Reversible injury

0-1/2 hr None None

1/2 -4 hr None Usually none; variable waviness of fibers at border





Irreversible Injury

4-12hr Occasionall dark mottling Beginning coagulation necrosis; edema; hemorrhage

12-24hr Dark mottling Ongoing coagulation necrosis; pyknosis of nuclei; myocyto hypereosinophilia; marginal contraction band necrosis; beginning neutrophilic infiltrate

1 -3 days Mottling with yellow-tan infarct center

Coagulation necrosis, with loss of nuclei and striations; interstitial infiltrate of neutrophils

3-7 days Hyperemic border; central yellow-tan softening

Beginning disintegration of dead myofibers, with dying neutrophils; early phagocytosis of dead celis by macrophages at infarct border

7-10 days Maximally yellow-tan and soft, with depressed red-tan margins

Well-developed phagocytosis of dead cells; early formation of fibrovascular granulation tissue at margins

10-14 days Red-gray depressed infarct borders

Well-established granulation tissue with new blood vessels and collagen deposition

2-8wk Gray-white scar, progressive from border toward core of infarct Increased collagen deposition, with decreased cellularity



>2mo Scarring complete

Dense colla'genous scar























3. Which of the following markers is specific for gastro intestinal stromal /tumors (GIST) .

a. CD 117

b. CD34

c. CD23

d. S-100 ,-. -

Ans.A. CD117

Ref, Robbin$,8th ed., page 789

GIST arise from cells of caja!. The common variety of GIST are with smooth muscle differentiation & are associated with mutations of C-kit with expression of CD117 on the surface, which is used as a irnrnunohistochemistry marker for identification for these tumours in biopsy. Marker in GIST

• CD1l7-(c-kit)-95%

• CD34-70%

• Smooth muscle Actin-5%

GIST originates from Interstitials cells of cajal. Which control gastrointestinal peristalsis.

Most common site for GIST is stomach followed by-small bowel. Anti DOG antibody is even fi.ore specific than CD 117,





















































.













4. In congenital dystrophic variety of epidermolysis bullosa, mutation is seen in the gene coding for

a. Laminin 4

b. Collagen type 7

c. Alpha 6 integerin

d. Keratin 14

Ans. B. Collagen type 7

Ref: Robbins.Sth ed, page 1196, Harper 27th ed, chapter 47

















Type Tissues Genetic Disorders

I. This is the most abundant collagen of the human body found in most connective tissues includina bone

Osteogenesis impertecta

type 1, Ehlers Danlos syndrome type-7



II. Cartilage, Vitreous humor Coljagenopathy, types II & XI

III. Frequently found with type I in skin, muscles, and blood vessels, strengthens the walls of hollow extensible structures like arteries, the intestine, and the uterus. This is the collagen of granulation tissue, and is produced quickly by young fibroblasts before the tougher type I colladen is synthesized

Ehlers -Danlos syndrome type -4



IV. Basement membrane (serves as part of the filtration system in capillaries and the llpmeruli of nephron in the kidney lens. Alport syndrome



V. Most interstitial tissue, assoc. with type I, associated with placenta

Ehlers - Danlos syndrome (Classical)



VI. Most interstitial tissue, assoc. with type I

Ulrich myopathy and bethlem myopathy

VII. Forms anchoring fibrils in dermal epidermal junctions

Eoidermolysis bullosa





5. Infraclavicular lesion of tuberculosis is known as

a. Ghon's focus

b. B. Puhl's focus

c. Assman's focus

d. Simmon's-focus

Ans. A, Ghon's focus

Re.. Robbins,8th ed., page 370

Primary TB:

Usually occurs in childhood, and the lungs are the most frequent site of initial contact with the tubercle bacilli. Transmission of TB is via inhalation.



Primary Focus: (aka Gohn focus)

Almost always found just beneath the pieura in the basal segment of the upper lobe or apical segment of lower lobe, (where there is greatest volume of inspired air.) The focus is usually small (<1cm). Microscopically, typical caseating granulomas are seen. Organisms drain to hilar nodes, again with formation of granulomas.



Primary (Ghon) Focus

Primary (Ghon) Complex = Primary focus + involvement of regional lymph nodes



Primary foci are usually entirely asymptomatic.

The old sites of the healed primary TB infection may be marked by a pulmonary nodule or granuioma in the lung, which over time may become calcified. These nodules are known as "Ghon lesions"



When seen together with ipsiiateral calcified hiiar adenopathy.. the finding is termed a "Ranke's complex",



Apical scarring with the appearance of a fibronodular patch or ill-defined reticular shadow in the upper lung fields on chest x-ray is

known as "Simon's focus" and in a patient with a positive tuberculin skin test identifies a patient with a markedly increased risk for active TB.



PURL'S LESION - Lesion at the apex of lung in chronic TB - commonest site of isolated lesion in chronic TB



Assmann's Focus –

Site:

Typically apical (site of highest oxygen tension) Known as Secondary or 'Assrnari focus.



Secondary (Assman) focus:

TB SIMON'S FOCUS - Early hematogenous seedling in apex of lungs

GHON'S COMPLEX - parenchyma! subpleural lesion + draining lymphatics + enlarged caseous lymph nodes in primary tuberculosis



RANKE COMPLEX - healed lesions in lung parenchyma and hilar lymph nodes undergoing calcification due to TB RICH FOCUS - tuberculous caseous foci in brain, meninges and spinal cord

Epituberculosis

• In young children with a positive tuberculin test extensive physical changes were found in the chest, consisting of an impaired

• percussion note with diminished or tubular breathing, mostly localized in the upper lobe, especially on the right side. Rales were only rarely heard.

• The most striking feature being that in the majority of cases the physical signs, after remaining unchanged for some months,



Completey disappeared

• The extensive physical changes appearing on the skiagram as a dense diffuse shadow were. not due to specific tuberculous tissue changes.

• They suggested that these pathological alterations were a reaction in the adjacent lung Tissue to toxins produced by a tuberculous focus, if the activity of the focus ceased these alterations might completely disappear.

• The infiltration should be put on the same level with the perifocal inflammation (Tendeloo) which may occur in the



proximity of any inflammatory focus (e.g. the inflammatory swelling round a boil).

Hence onlv Ghon's complex found below clavicle, apex of lunq found above clavicle



6. About mesothelioma all are true except

a. Develop in late middle age

b. It is bilateral and symmetrical

c. It is due to chronic exposure to asbestosis

d. It shows biphasic pattern



Ans, b. It is bilateral and symmetrical

Ref. Harrison ,17th ed., page 1613-1617

• Mesotheliomas both pleural and peritoneal, are also associated with asbestos exposure.

• In contrast to lung cancers, these tumors do not appear to.be associated with smoking.

• Relatively short-term asbestos exposures of <1-2 years or less, occurring up to 40 years in the past, have been associated with the development of mesotheliomas

• Although -50% of mesotheliomas metastasize, the tumor generally is locally invasive, and death usually results from local extension.

• Most patients present with effusions that may obscure the underlying pleural tumor

• In contrast to the findings in effusion due to other causes, because of the restriction placed on the chest wall, no shift of mediastinal structures toward the opposite side of the chest will be seen.

• The major diagnostic problem is differentiation from peripherally spreading pulmonary adenocarcinoma or from adenocarcinoma metastasized to pleura from an extrathoracic primary site.

• Although cytologic examination of pleura! fluid may suggest the diagnosis, biopsy of pleural tissue, generally with video-assisted thoracic surgery, and special immundhistochemical staining is usually required.

• Microscopically Malignant mesothelioma may be epithelioid (60%) ,$arcomatoid (20%) or can be mixed Le btphasic histology seen.

• There is no effective therapy. . .



7. A 7 yrs old girl is brought with complaints of generalized swelling of the body. Urinary examination reveals grade 3 proteinuria and the presence of hyaline and fatty casts. She has no history of hematuria. Which of the following statements about her condition is true-

a. No IgG deposits or C3 deposition on renal biopsy

b. Her C3 levels will be low

c. IgA nephropathy is the likely diagnosis

d. Alport's syndrome is the likeiy diagnosis

Ans. A. No IgG deposits or C3 deposition on renal biopsy

Ref, Robbins,8th ed.fpage 925,926

History indicates that the child is suffering from nephrotic syndrome. The most common cause of nephrotic syndrome in children is

minimal change disease. Minimal change disease is characteristic used by

i. Diffuse effacement of foot processes of viscera! epithelial cells (Podocytes) in the glomeruii that appear virtually normal by light microscopy

ii. Immunofluorescence studies show No Ig or complement deposits

iii. The glomeruii are normal by light microscopy. The cells of the PCT are often laden with lipid and protein, reflecting tubular reabsorption of lipoproteins, passing through diseased glomeruii (thus the historical name lipoid nephrosis for this disease)

iv. Clinically the child presents with aggressive proteinuria and there is commonly no hypertension or hematuria

v. The proteinuria is highly selective, most of protein-having albumin .

vi. Most children (90%)with minima! change disease respond rapidly to corticosteroid therapy



























8. Commonest histoiogicai finding in benign hypertension is

a. Proliferate endanentis

b. Necrotizmg arteriolitis

c. Hyaline arteriosclerosis

d. Cystic medial necrosis

i

Ans. C. Hyaline arteriosclerosis

Pet: Robbins.Sth ed., page 495,496

-"Hypertension is associated with two forms of small bloods vessel disease.

Hyaline arteriosclerosis " .

Hyperplastic arteriosclerosis



Hyaline arteriosclerosis is seen is benign hypertension. Arterioles shows homogenous pink hyaline thickening with associated luminai narrowing. These changes stem from plasma protein leakage across injured endothelial cells & increased smooth muscle cell matrix synthesis in response to chronic hemodynamic stress.

Being nephrosclerosis

Malignant nephrosclerosis



This term is used to describe the changes in kidney associated

with benign phase of hypertension

This term is used to desribe the changes in kidney associated

with malignant or accelerated hypertension



Gross

Gross

Kidney size is either normal or may be moderately reduced

Grain leather appearance

:The cortical surface has a fine even granularity



Kidney size is variable may be smaller in size (when

superimposed on benign nephrosclerosis) or larger in size

(enlarged) than normal (patients" who develop malignant

hypertension in pure form)

Flea bitten appearance

The cortical surface may show multiple small petechial

hemorrhages from rupture of arterioles or glomerular capillaries



Microscopic (vascular changes & parenchymal changes Microscopic (Vascular changes & parenchymal changes

Hyaline arteriosclerosis



Narrowing of the lumens of arterioles and small arteries caused by thickening and hyalinization of the walls



Fibroelastic hyperplasia in the intima (intima! thickening), duplication of elastic lamina and hypertrophy of the 'media’



Parenchymal changes (due to ischaemic) variable degree of atrophy of parenchyma due to ischemia

Fibrinoid necrosis of arterioles (necrotizing arteriolitis



The vessel wall shows fibrinoid necrosis. Represents an acute event and necrosis is usually not accompanied by intense inflammation



Hyperplastic intimal sclerosis / onion skinning





Concentric laminae of proliferated smooth muscle cells, collagen and basement membrane (producing intimal thickening) Parenchymal changes (due to ischaemia) Variable degree of atrophy of parenchyma due to ischaemia. Infarction necrosis distal to abnormal vessels may be seen_____



9. All of the following are true about Hashimoto's thyroiditis, except

a. Foliicuiar destruction

b. Increase in lymphocytes

c. Oncocytic metaplasia

d. Orphan Annie eye nuclei

Ans. D. Orphan Annie eye nuclei Ref Robbin$,8th ed. ,page 1112,1122 Ref: Harrison 17th edition page 2239

I. Hashimoto's thyroiditis is the most common cause of goitrous autoimmune hypothyroidism.

II. The thyroid gland is often diffusely enlarged with an intact capsule. The gland is enlarge from to hard.

III. Microscopic examination shows extensive infiltration of parenchyma by a mononuclear inflammatory infiltrate containing small lymphocytes, plasma cells and well developed germinal centre,

IV. The thyroid follicular cells are atrophic and are lined in many areas by epithelial cells distinguished by the presence of abundant eosinophilic granu4Ir cytoplasm termed Hurthle cell (oncocytic cells).

V. This is a metaplastic response of the normally low cuboidal follicular epithelium to ongoing injury.

VI. Orphan Annie eye nucleus is a feature of cells in papillary carcinoma of thyroid,

VII. The nuclei of papillary carcinoma cells contain finely dispersed chromatin, which imparts an optically clear or empty appearance giving rise to ground glass or orphan Annie Eye nuclei

VIII. In addition, invagination of the cytoplasm may in cross reactions give the appearance of intranuclear inclusions ("Pseudo inclusion" or intranuclear grooms)

IX. The diagnosis of papillary carcinoma is based on these nuclear feature even in the absence of papillary architecture.

Extra Edge:



Table 335-8 Causes of Thyroiditis

Acute



Bacterial infection; especially Staphylococcus, Streptococcus, and Enterobacter Fungal infection: Aspergitlus, Candida, Cocctdioides, Histoplasma, and Pneumocystis Radiation thyroiditis after 131I treatment Amiodarone (may also be subacute or chronic)



Subacute

Virai (or granulomatous) thyroidiiis

Silent thyroiditis (including postpartum thyroiditis)

Mycobacteriai infection



Chronic



Autoimmunity: focal thyroiditis, Hashimoto's thyroiditis, atrophic thyroiditis Riedel's thyroiditis

Parasitic thyroiditis: echinococcosis, strongyloidiasis, cysticercosis Traumatic: after palpation







10. CD4 - is not important for which of the following

a. Antibody production

b. Cytotoxicity of T cells

c. Memory B cells

d. Opsonization

Ans. D. Opsonization

Ref.. Robbins,8th ed., page 395-397

Ref-Ananthanarayan and Pan/Acer's Textbook of Microbiology, 8th ed, pg 140

• CD4 cells are helper T cells that are activated when the antigen is presented to them complexed with MHC class II.

• The activated helper T cell forms IL-2, IL-4, IL-5 and IL-6 which act as B cell activating factor and B cell differentiation factor so that B cells differentiate into antibody secreting plasma cells.

• A small proportion of B ceils instead of forming plasma cells become long-lived memory cells.

• Cytotoxic T cells are activated when they contact antigens presented with MHC Class I molecules. They also need a second signal IL-2, which is secreted by activated helper T cells.

Extra Edqe

CD4 (cluster of differentiation 4) is a glycoprotein expressed on the surface of T helper cells, regulatory T cells, monocytes,macophages, and dendritic cells.



Hi V infection

• HIV-1 uses CD4 to gain entry into host T-cells and achieves this by binding of the viral envelope protein known as gp120 to.

• The-irTcTing to CD4 creates a shift in the conformation of gpl 20 allowing HiV-1 to bind to a co-receptor expressed on the host cell.

• These co-receptors are chempkine receptors CCR5 or CXCR4, which of these co-receptor is used during infection is dependent on whether the virus is infecting a macrophage or T-helper cell

• Following a structural change in another viral protein (gp4i), HIV inserts a fusion peptide into the host cell that allows the outer membrane of the virus to fuse with the cell membrane,

HIV pathology

• HIV infection leads to a progressive reduction in .the number of T cdlis'expressing CD4. Medical professionals refer to the CD4 count to decide when to begin treatment during HIV infection. "

• Normal blood values are 500-1200x1i Q6/L. CD4 count test measures the number of T cells expressing CD4. Results are usually - expressed in the number of ceiis per microliter (or cubic ^millimeter, mm3) of blood.

• While CD4 tests are riot a direct HfV test e.g; does not check the presence of viral DNA, or specific antibodies against HIV, the CD4 count is used to assess the immune system of patients.

• Patients often undergo treatments when the CD4 count reach a level of 350 ceils per microliter; less than 200 ceils per microiiter in an HIV positive individual is diagnosed as AIDS,

• CD4 count is used to determine efficacy of treatment



11. What does "cardiac polyp" mean?

a. Acute infarct

b. Cardiac aneurysm

c. Benign tumour

d. Fibrinous clot

Ans. D. Fibrinous clot

Ref:-Text below Post Mortem clots:*

Definitions:

1. Usually a rounded thrombus attached to the endocardium

I. When blood clots rapidly a soft, lumpy, uniformly dark - red, slippery, moist clot is produced (black current jelly),

II. When red cells sediment before blood coagulates the red cells produce a clot similar to the first type - Above this, a pale or bright yellow layer of serum and fibrin is seen (chicken fat).Both of them are moist, smooth shiny rubbery, homogenous, loosely or not at all attached to the underlying wall. They are called cardiac polyp bright or not at



12. International prognostic index lor lympnomas includes the following prognostic factors except

a. Stage of disease

b. Number of extralymphatic sites involved

c. LDH

d. Hb and albumin

Answer. D. Hb and albumin

The Hb and albumin status is not included amongst the parameters to calculate the prognostic index

International Prognostic Index

One point is assigned for each of the following risk factors:

• Age greater than 60 years

• Stage III or IV disease

• Elevated serum LDH

• ECOG/Zubrod performance status of 2, 3, or 4

• More than 1 extranodal site



The sum of the points allotted correlates with the following risk groups:

• Low risk (0-1 points) - 5-year survival of 73%

• Low-intermediate risk (2 points) - 5-year survival of 51 %

• High-intermediate risk (3 points) - 5-year survival of 43%

• High .risk (4-5 points) - 5-year survival of 26%

ECOG/WHO/Zubrod score

• 0 - Asymptomatic (Fully active, able to carry on al! predisease activities without restriction)

• 1 - Symptomatic but completely ambulatory (Restricted in physically strenuous activity but ambulatory and able to carry out work of a light or sedentary nature. For examp!e; light housework, office work)

• 2 - Symptomatic, <50% in bed during the day (Ambulatory and capable of all self care but unable to carry out any work activities. Up and about more than 50% of waking hours)

• 3 - Symptomatic, >50% in bed, but not bedbound (Capable of only limited self-care, confined to bed or chair 50% or more of waking hours)

• 4 - Bedbound (Completely disabled. Cannot carry on any self-care. Totally confined to bed or chair)

• 5 – Death



13. Mucinous cyst of pancreas, which is false among the following

a. Struma ovarii

b. Premalignant lesion

c. Columnar epithelium lesion

d. Microcystic adenoma

Answer - A. Struma ovarii .

• Struma ovarii is an example of monodermal teratoma in ovary, where the germ cells have differentiated towards one particular type of tissue, that is thyroid. Hence this is the wrong choice.

• Serous cystedenoms are microcystic adenomas. Mucinous cysts are lined by coiumner epithelium. Have ovarian like stroma and have more malignant potential than serous cyst

• Cystic turno UTS of the pancreas may be serous or mucinous.

• Serous cystadenomas

o Typically found in older women

o Large aggregations of multiple small cysts, almost like bubble wrap.

o They are benign.

• Mucinous

o Have the potential for malignant transformation.

o They include

i. Mucinous cystic neoplasms (MCNs)

• MCNs are seen in perimenopausal women,

• Show up as multilocular thick-wailed cysts in the pancreatic body or tail

• Historically, contain an ovarian-type stroma.

ii. Intraductal papillary mucinous neoplasms (IPMNs).

IPMNs

a. More common in the pancreatic head

b. In older men, but an tPMN arising from a branch duct can be difficult to distinguish from an MCN.

c. IPMNs arising within the main duct are often multifocal and have a greater tendency to prove malignant.



14. All of the following are true about sickle cell disease, except

a. Single nucleotide change results in change of glutamine to valine

b. RFLP results from a single base change

c. 'Sticky patch' is generated as a result of replacement of a non polar residue with a polar residue

d. HbS confers resistance against malaria in heterozygotes

Answer - B. RFLP results from a single base change

• Sickle cell anemia, is caused by a point mutation in the beta globin gene. As a result of this mutation, valine (a non-polar amino acid) is inserted into the beta globin chain instead of glutamic acid (an electrically charged amino acid).

• The mutation causes the RBCs to become stiff and sometimes sickle-shaped when they release their load of oxygen.

• The sickle cell mutation produces a "sticky" patch on the surface of they chains when they are not complexed with oxygen.

• Because other molecules of sickle cell hemoglobin also develop the sticky patch, they adhere to each other and polymerize into long fibers that distort the RBC into a sickle shape.

• When malarial parasites invade the bloodstream, the red cells that contain defective hemoglobin become sickled and die, trapping the parasites inside them and reducing infection.

• DNA obviously differs from one individual to another. Areas of DNA containing sequence variation due to point mutations, deletions, insertions, and repetitions are often referred to as polymorphic regions. However, polymorphic regions usually do not code for peptide products.

• When human DNA is digested with a particular restriction enzyme, a polymorphic region yields fragments of different sizes, called RFLPs.

• The fragments are separated by gel electrophoresis.

• Thus RFLP does not always result from a single base change,





15. A male child with Fanconi syndrome with nephrocalcinosis has a variant of dent disease. All are true except

a. Hypercalcuria

b. Proteinuria

c. Similar presentation in father

d. Rickets

Answer - C. Similar presentation in father.

• Dent's disease is a rare X-linked recessive inherited condition that affects the proximal renal tubules of the kidney,

• It is one cause of Fanconi syndrome, and is characterized by tubular proteinuria, hypercalciuria, calcium nephrolithiasis, nephrocalcinosis and chronic renal failure.

• "Dent's disease" is often used to describe an entire group of familial disorders, including X-linked recessive nephrotithiasis with renal failure, X-linked recessive hypophosphatemic rickets, and both Japanese and idiopathic low molecular weight proteinuria.





16. Antiphospholipid syndrome is associated with all except .

a. Recurrent abortion

b. Venous thrombosis

c. Pancytopenia

d. Antibody to lupus

Answer - None (Because all of them may be associated) -Antiphospholipid antibody syndrome

• This syndrome occurs in 5% of the general population, but is associated with 50% cases of SLE.

• Patients have anti phospholipid antibodies such as lupus anticoagulant, anticardioiipin antibody or anti beta 2 giyaoprotein (AIPG2011)

• Because phospholipids are integral parts of the control of coagulation, these antibodies can lead to a hypercoagulabie state, i.e., anti phospholipid antibody syndrome.



Patients with antiphospholipid antibody syndrome fall into two categories,

1. Primary antiphospholipid antibody syndrome

in these cases there is no evidence of other autoimmune disease, the patient exhibit only the manifestations of antiphospholipid antibody syndrome.

2. Secondary antiphospholipid antibody syndrome i !n this cases antiphospholipid antibody syndrome is associated with an autoimmune disease usually SLE.



Clinical manifestations of antiphospholipid antibody syndrome:

I. Asymptomatic.

II. Arterial and venous thromboembolism, avascular osteonecrosis.

III. Hematologic

• Cytopenia: Thrombocytopenia, autoimmune hemolytic anemia, leukopenia. Pancytopenia can occur.

• Coaguiopathy: Platelet dysfunction, prothrombin deficiency,

IV. Neurologic

• Acute ischemia (CVA, TIA, encephalopathy); severe migraine: multiple infarct dementia, seizure, peripheral neuropathy, myasthenia gravis.

V. Dermatologic

• Livedo reticularis, acrocyanosis (distal cutaneous ischemia, ulceration, gangrene), wide spread cutaneous necrosis, pyoderma gangrenosum-like skin lesions.

VI. Cardiopulmonary

• Marantic endocarditis, myocardial ischemia and infarction, intraca^diac thrombotic mass, peripheral arterial disease, Thrombopiastic and nonthrombotic pulmonary hypertension.

VII. Obstetric

• Recurrent spontaneous abortion predominantly second trimester IUGR, preeclampsia, chorea gravidarurn, low APGA score, prematurity.

VIII. Catastrophic antiphospholipid syndromes



Important Points::

In lupus anticoagulant thrombosis occurs (there is no increase in thrombocytes). Coagulation tests in lupus anticoagulant

PTT -> Prolonged

PT -> Normal

Fibrinogen -> Normal



Important Points:

a. Antiphospholipid antibodies are present in 40% to 50% of lupus patients and react with a wide variety of proteins in complex with phosphplipids.

b. Some bind to cardiolipin antigen, used in serologic tests for syphilis, and therefore lupus patients may have a false-positive test result for syphilis.

c. Thrombocytopenia occurs.

d. Sterility is not a feature



Laboratory Diagnosis

Antiphospholipid antibody test .

a) False positive test for syphilis

The FP-RPR is an antiphospholipid antibody.

b) Lupus anticoagulant

The name lupus anticoagulant is a paradox because only 50% of patients with the LA have lupus and because it is procoagulant not anticoagulant, in vivo. In vitro, though, the LA prolongs clotting time. PTTis increase but PT is normal

c) Anticardiolipin



I. In SLE there is no bleeding tendency rather there are thrombotic-episode due to anticardiolipin and lupus anticoagulant.

II. Despite thrombotic episodes, PTT is prolonged.

III. So in the above question the patient is a middle age female with normal PT and prolonged PTT without any history of excessive bleeding, It indicate she has anticardioiipin and the lupus anticoagulant.

IV. There are two tests that measure anticardiofipin and the lupus anticoagulant:

1) ELISA for anticardiolipin

2) A sensitive phospholipid-based activated prothrombin time such as the dilute Russell venom viper test.



Important Points:; (Ref.H 17H'Pg 2079) .

 Some centers also recommend measurement of antibodies to beta 2 glycoprotein 1 (AIPG 2011), a serum.protein cojactor that is the target of mostantibodies to canjipiipin and some lupus anticoagulants.

 High titers of IgG anticardiolipin (>50lO)^ indicate high risk for a clinical episode of clottfng,



Dilute Russell's viper venom time (dRVVT) is a lab test often used for detection of lupus anticoagulant (LA,),



Mechanism

1. This in vitro diagnostic test is based on the ability of the venom of the Russell's viper to induce thrombosis.

2. The coagulant in the venom directly activates factor X, which turns prothrombin into thrombin in the presence of factor V and phospholipid.

3. In the dRVVT assay, low. rate-limiting concentrations of both Russell's viper venom and phospholipid are used to give a clotting time of 23 to 27 seconds.

4. This makes the test sensitive to the presence of lupus anticoagulants, since these antibodies interfere with the clot-promoting role of phospholipid in vitro.

5. The dRVVT test is more sensitive than the a PTT test for the detection of lupus anticoagulant, because it is not influenced by deficiencies or inhibitors of clotting factors VII}, IX or XI.



Important Points:

a. An additional autoantibody test with predictive value (not used for diagnosis) detects anti-Ro, which indicates increased risk for. neonatal lupus, sicca syndrome, and Sub acute cutaneous lupus erythematosus (SCLE)

b. Women with child-bearing potential and SLE should be screened for aPL and anti-Ro









Physiology

1. The primary direct stimulates for excitation of central chemoreceptors is

a. Increase H+

b. Increase CO2

c. Increase 02

d. Decrease C02



Ans. A Increase H+ .

Ref: Ganong- Review of medical physiology 23rd Ed page 574

• Central chemoreceptors : The chemoreceptors that mediate the hyperventilation produced by increases in arterial PCC>2 after the carotid and aortic bodies are denervated are located in the medulla oblongata and consequently are called medullary chemoreceptors.

• They are separate from the dorsal and ventral respiratory neurons and are located on the ventral surface of the medulla. The chemoreceptors monitor the rf concentration of CSF, including the brain interstitial fluid.

• CO2 readily penetrates membranes, including the blood-brain barrier, whereas H* and HCOj penetrate slowly. The CO2 that enters the brain and CSF is promptly hydrated. The H2C03 dissociates, so that the local HT concentration rises.

• The H concentration in brain interstitial fluid parallels the arterial PCOg. Experimentally produced changes in the PCOa of CSF have minor, variable effects on respiration as long as the H+ concentration is held constant, but any increase in spinal fluid H+ concentration stimulates respiration.

• The magnitude of the stimulation is proportionate to the rise in H+ concentration. Thus, the effects of C02 on respiration are mainly due to its movement into the CSF and brain interstitial fluid, where it increases the H+ concentration and stimulates receptors sensitive to H*.

• So COa acts indirectly via H+ therefore the primary direct stimulus for them is increase in H-f levels in CSF





2. Which of the following statements about vasomotor centre (VMC) is true

a. Independent of corticohypothalamic inputs

b. Influenced by baroceptor signals but not by chemoreceptors

c. Acts along with the cardiovagal centre (CVC) to maintain blood pressure

d. Essentially silent in sleep



Ans. C. Acts along with the cardiovagal centre (CVC) to maintain blood pressure

Ref: Ganong - Review of Medfcal Physiology 23nd Ed page 478

• The main control of blood pressure is exerted by groups of neurons in the medulla obiongats that are, sometimes called collectively the vasomotor area or vasomotor center.

• As we can see from the table listed below (from Ganong) the VMC can be excited by Cortical signals (example increased HR & BP during sexual excitement and anger) or inhibited,

• Also the Baroreceptors are inhibitory to VMC but chemoreceptors are stimulatory.

• In sleep these centre are working to maintain BP just like respiratory centres are maintaining respiration. « The Cardio Vagal Centre (CVC) inhibits the VMC pressor area. And there is a functional interaction between the CVC and VMC. The pattern of discharge from CVC is not tonic but together they both maintain a normal BP.







Factors Affecting the Activity of the Vasomotor Area in the Medulla,

Direct stimulation

CO2

Hypoxia

Excitatory inputs

From cortex via hypothalamus

Pain pathways and muscles

From carotid and aortic chemoreceptors

Inhibitory inputs

From cortex via hypothalamus

From lungs

From carotid, aortic, and cardiopulmonary baroreceptors





3. Angiotensin II causes all of the following, except

a. Stimulation of thirst

b. Increased ADH secretion

c. Vasodilation

d. D. Atdosterone secretion

Ans. C. Ref: Ganong - Review of Medical Physiology 23"d Ed page 612

Actions of Angiotensin II

• Angiotensin II binds to AT1 receptors in the zona glomerulosa which act via a G protein to activate phospholipase C.

• The resulting increase in protein kinase C fosters the conversion of cholesterol to pregnenolone and facilitates the action of aldosterone synthase, resulting in increased secretion of aldosterone.

• Anqiotensin II is one of the most potent vasoconstrictors in body,

• Angiotensin II increases thirst sensation through the subfornical organ (SFO) of the brain, decreases the response of the baroreceptor reflex, and increases the desire for salt.

• It increases secretion of ADH in the posterior pituitary and secretion of ACTH in the anterior pituitary.

• It also potentiates the release of norepinephrine by direct action on postganglionic sympathetic fibers.



4. Which of the following statements about cutaneous shunt vessels is true

a. Perform nutritive function

b. Have roie in thennoregulation

c. Not under the control of autonornic nervous system

d. These vessels are evenly distributed throughout the skin

Ans. B. Have roie in thei moregulation

Ref: Ganong - Revww of Medical Physiology 2tfld Ed page 524

ARTERIOVENOUS ANASTOMOSES

• In the fingers, palms, and ear lobes, short channels connect arterioles to venules, bypassing the capillaries. These arteriovenous (A-V) anastomoses, or shunts, have thick, muscular walls and are abundantly innervated, presumably by vasoconstrictor nerve fibers.

• The amount ot heat lost from the body is regulated to a iarge extent by varying the amouiu skin.

• Blood flow in response to ihermoregulatory stimuli can vary from 1 to as much as 150 mL/10Q g of skin/min, and it has been postulated thai these variations are possible because blood can be shunted through the anastomoses. Therefore they play an important role in regulation of body temperature and one of the earliest changes in Hot climate is cutaneous vasodilation due to opening of shunt vessels and the reverse occurs in cold weather.



5. Maximum postprandial motility is seen in

a. Ascending colon

b. Transverse colon

c. Descending colon

d. Sigmoid colon

Ans. D. Sigmoid colon

Ref: Ganong - Review of Medical Physiology 2^ Ed page 386

• Gl Motiiity is due to some cells in the smooth muscle of Gl mucosa called as interstitial cell of cajal which generate basic electrical rhythm (BER) and act as a pacemaker and regulate the motility.

• These BERs rarely cause muscle contraction but spike potential superimposed on the most depolarizing portion increases muscle tension.

• Acetyi choline increase the no. of spikes and tension developed in smooth muscles, hence increases motility.

Rate of BER is:



1.4/min in stomach . 2.12/min in duodenum

3. 8/min in distal ileum 4. 9/ min in caecum

5.16/min in Sigmoid colon

So, maximum motility develops in sigmoid colon.



6. True about myocardial 02 demand is

a. Directly proportional to duration of systole

b. Inversely proportional to heart rate

c. Negligible in quiescent heart

d. Has a constant relation to the external work done by heart

Ans. A, Directly proportional to duration of systole

Ref: Ganong - Review of Medical Physiology 2?* Ed page 516

• The Da consumption by the heart is determined primarily by the intramyocai'diai tension, the contrauite state myocardium, the heart rate duration of systole.

• We also use tension-time index developed as 'a measure of the work done of the left ventricle and is a-product of the mean systolic pressure, times the duration of systole, times the heart rate.

• Quiescent heart is an alive but non beating heart example conduction block: hypothermia, vaga! inhibition of heart. So It does consume oxygen as it is still alive although very less in amounts.

• Ventricular work per beat correlates with Go consumption. The work is the product of stroke volume and mean arterial pressure in the pulmonary artery (for the right ventricle) or the aorta (for the left ventricle).

• Since aortic pressure is seven times greater than pulmonary artery pressure, the stroke work of the left ventricle is approximately seven times the stroke work of the right ventricle

• Pressure work produces a greater increase in 0? consumption than volume work. In other words, an - crease in afterload causes a greater increase in cardiac Q2 consumption than an increase in preload does.

• This is why angina pectoris due to deficient delivery of O2 to the myocardium is more common in ao.tic stenosis than in aortic insufficiency, in aortic stenosis, intraventricular pressure must be increased to force biood trough tos stenotic valve, whereas in aortic insufficiency, regurgitation of blood produces an increase in stroke volume '-vith little change in aortic impedance. So the relation between work done and Os demand is no! linear.



7. In animals with chronic exposure to cold what is true

a. Sympathetic tone to heart is not much affected

b. Free insulin is increased

c. Vagal inhibition of heart is reduced

d. Perfusion of adipose tissue is decreased

Ans. C. Vagal inhibition of heart is reduced

Ref: Animal adaptation to cold. Lawrence C. H. Wang, J. A. Boulant 1st ed. Page 25,36,102-197



• Several studies indicate that chronic exposure to cold activate some adaptive mechanisms characterized by a admonition of the sympathetic response and a concomitant enhancement of the vagal activation. As a result the heart rate decreases.

• The various other studies and their results suggest that cold depresses blood insulin levels through activation of the a-adrenergic inhibition of the pancreatic insulin response.

• There is a increased blood flow to adipose tissue to increase thermogenesis in adipose tissue (primarity in brown fat through UCP 1



Mechanisms activated by cold in body

a.Shivering b. Hunger

c.increased voluntary activity d. increased secretion of norepineprine and epinephrine

e. decreased heat loss f. cutaneous vasoconstriction

g. curling up h. horripilation



8. CSF pressure is mainly regulated by

a. Rate of CSF formation

b. Rate of CSF absorption

c. Cerebral blood flow

d. Venous pressure

Ans. B. Rate of absorption

Re1: Ganong - Review of Medical Physiology 2$ld Ed

Normal CSF pressure is mainly regulated by rate of absorption by arachnoid villi

• The normal rate of CSF formation remains nearly very constant. It is independent of the CSF press ure.

• Absorption by arachnoid villi is proportionate to the CSF pressure (Arachnoid villi act like valves and allow CSF fluid to flow into venous sinuses when CSF pressure is about 1.5mm Hg greater than the pressure of blood in the venous sinuses. If the CSF pressure rises further, the valves open more widely, so that under normal conditions, the CSF pressure almost never rises more than a few mm of Hg higher than the pressure in the cerebral venous sinuses)



9. Maximum 02 consumption at rest is by

a. Lean body mass

b. Adipose tissue

c. Resting heart rate

d. Exercise

Ans, A. Lean body mass

Re1: Ganong - Review of Medical Physiology 23^ Ed page 456

• Energy expenditure in resting state is given by RMR or the Resting Metabolic Rate. The metabolic rate determined at rest in a room at a comfortable temperature in the thermoneutral zone 12-14 hours after the last meal is called the basal metabolic rate (BMR).

• It is directly proportional to amount of oxygen consumed. The rate during normal daytime activities is, of course, higher than the BMR because of muscular activity and food intake.

• The maximum metabolic rate reached during exercise is often said to be 10 times the BMR, but trained athletes can increase their metabolic rate as much as 20-fold. The BMR of a man of average" size is about 2000 kcai/d. Large animals have higher absolute BMRs, but the ratio of BMR to body weight in small animals is much greater. The relation of BMR to body weight (W) is BMR= 3.52W0.67

However, repeated measurements by numerous investigators have come up with a higher exponent, averaging 0.75. BMR= 3.52W0.67



So Energy expenditure in resting state would depend very much on body weight, thereby lean body mass which is around 80-85% of total body weight is the correct answer. Adipose tissue are metabolicaliy very much inert so not much effect on 8MR.

Factors Affecting the Metabolic Rate.

1.Muscular exertion during or just before measurement 2. Recent ingestion of food

3. High or low environmental temperature 4. Height, weight, and surface area

5. Sex 6. Age

7. Growth 8. Reproduction

9. Lactation 10. Emotional state

11. Body temperature 13. Circulating epinephrine and norepinephrine levels

12. Circulating levels of thyroid hormones



10. Which of the following statement is true ?

a. Fluid coming from the descending limb of loop of henle is hypotonic

b. Descending limb of loop of henle is permeable to solutes

c. If clearance of substance is greater than GFR, then tubular secretion must be present

d. Clearance of a substance is always less than GFR if there is tubular secretion

Ans. C. If clearance of substance is greater than GFR, then tubular secretion must be present

Ref: Ganong - Review of Medical Physiology 22nd Ed page 631

• The explanation is based on the basic definition and the concept of clearance.

• The clearance of a substance which is freely filtered and neither secreted nor reabsorbed (e.g. inulin clearance) gives the value of GFR.

• Any substance which has a clearance greater than that of inulin must be getting secreted in addition to being freely filtered

• One of the most important aspects of counter-current multiplier system is the differential permeability characteristic of descending thin segment (DTS) and the ascending thin segment of the loop of Henle (ATS):

o DTS : is permeable to water but not solutes

o ATS : is permeable to sodium but not water

• Due to this, the tubular fluid in the descending loop gets hypertonic whereas in the ascending limb, the tubular fluid becomes dilute.

11. Nitrogen narcosis is caused due to '

a. Nitrogen inhibits dismutase enzyme

b. Increase production of nitrous oxide

c. Increased solubility of nitrogen in nerve cell membrane

d. Decrease in oxygen free radicals

Ans. C. Increased solubility of nitrogen in nerve cell membrane

• Nitrogen narcosis( inert gas narcosis, raptures of the deep, Martini effect) is a reversible alteration in consciousness that occurs while scuba diving at depth as under high pressure nitrogen becomes soluble in blood and reaches the brain.

• Apart from helium, and probably neon, all gases that can be breathed have a narcotic effect, which is greater as the lipid . solubility of the gas increases.

• The precise mechanism is not well understood, but it appear-, to be the direct effect of gas dissolving into nerve membranes and causing temporary disruption in nerve transmissions. » Some of these effects may be due to antagonism at NMDA receptors and potentiation of GABAA receptors. Similar to the mechanism of ethanol's effect, the increase of gas dissolved in nerve cell membranes may cause altered ion permeability properties of the neural cells' lipid bilayers.

• An early theory, the Meyer-Overton hypothesis suggested that narcosis happens when the gas penetrates the lipids of the brain's nerve cells, causing direct mechanical interference with the transmission of signals from one nerve cell to another.