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Block A > Gastroenterology > Flashcards

Gastroenterology Flashcards

1
Q

2 regulatory sequences within HBV gene

A
  • GRE glucocorticoid responsive element
  • enhancer
    GRE regulates enhancer
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2
Q

which gene produces HBsAg?

A

Gene S

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3
Q

Function of HBV enhancer I

A

stimulates protein expression esp.

the core protein

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4
Q

Function of HBV region X

A

encodes products for transactivation (integrating genome into host genome),
? related to carcinogenesis

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5
Q

Function of HBV Enhancer II

A

stimulates surface gene promoters

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6
Q

Function of HBV Direct repeat II DRII

A

initiates short +ve strand synthesis, preferential sites for integration

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7
Q

Function of HBV DRI direct repeat I

A

initiates long -ve strand synthesis,

preferential sites for integration

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8
Q

Where is HBcAg found? Which gene encodes it?

A

found in virus or hepatocytes

GeneC

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9
Q

Where is HBeAg found?

A

Serum

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10
Q

clinical significance of pre-C protein in HBV

A

Mutant strain with stop codon (TAG) causes
inability to produce HBeAg even if virus is still rapidly replicating
Mutation detected around e-seroconversion,
probably because immune factors
selecting against HBeAg-producing virus,
so HBeAg-deficient mutants emerge.
These pts will be HBeAg -ve, anti-HBe +ve,
HBV DNA +ve

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11
Q

Function of HBV Gene P

A

Encodes polymerase and reverse transcriptase

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12
Q

Steps of HBV replication

A
  1. adsorption
  2. release of relaxed circular partially dsDNA
  3. completion of +ve strand DNA
  4. transport to nucleus
  5. conversion to supercoiled cccDNA
  6. transcription of mRNA
  7. transportation of mRNA to cytoplasm
    8a. translation of mRNA to viral proteins

8b. translation of pregenomic RNA to DNA pol/RT
9b. encapsidation of DNA pol bound to pregenomic RNA
10b. RT of pregenomic RNA to full length -ve strand DNA
11b. +ve strand DNA synthesis by DNA pol into relaxed circular partial dsDNA
12b. amplification and replenishment of cccDNA

Common pathway after 8a/11b:

9a. migration to ER
10a. acquisition of envelopes
11a. exocytosis

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13
Q

2 types of jaundice

A

unconjugated/indirect hyperbilirubinemia (prehepatic)

conjugated/direct hyperbilirubinemia (hepatic or post-hepatic)

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14
Q

Causes of unconjugated hyperbilirubinemia/ prehepatic jaundice

A
  1. increased bilirubin production - hemolysis (G6PD deficiency, thalassemia)
  2. decreased hepatic uptake - drugs (rifampicin)
  3. decreased conjugation - congenital (Gilbert’s syndrome, Criggler-Najjar syndrome)
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15
Q

Raised ALP and GGT

A
  • cholestatic conditions

- SOL in liver except polycystic liver

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16
Q

Isolated GGT elevation

A
  • alcohol
  • Fatty liver
  • drugs (rifampicin, antiepileptics - phenytoin carbamazepine barbituates)
17
Q

Isolated ALP elevation

A
  • bone conditions (bone CA, Pagets, osteomalacia, MM)
  • puberty
  • pregnancy
18
Q

Causes of conjugated hyperbilirubinemia

A

hepatic: (diffuse hepatic injury)
- hepatitis
- late stage cirrhosis
post-hepatic:
intrahepatic - hepatocyte secretory defect eg cholestatic phase of viral hepA and E; bile canaliculi eg PBC PSC
extrahepatic obstruction - CBD stones, cholangitis, malignancy

19
Q

reasons for elevated globulin in cirrhosis

A
  • portosystemic shunting
  • not degraded properly in the liver
  • abnormal antigen produced in cirrhotic liver
20
Q

reversed A:G (>42:<36)

A
  • MM
  • cirrhosis
  • nephrotic syndrome
  • SLE
21
Q

What exceptional liver disease gives AST>ALT

A 
AST 2x> ALT
1. alcoholic liver disease 
2. CA/met liver 
AST not 2X> ALT
2.5 NASH progressed to cirrhosis
22
Q

Etiology of acute hepatitis

A
  • hepatitic virus
  • drugs
  • alcoholic
  • obesity
  • autoimmune
  • metabolic
  • nonhepatitic virus
23
Q

Serological markers for HCV

A

anti-HCV

HCV RNA

24
Q

Etiology of chronic hepatitis

A
  • HBV, HCV, HDV
  • drugs
  • alcoholic
  • NASH
  • autoimmune
25
Q

what is Gilbert’s syndrome

A

reduction in hepatic bilirubin glucuronyl transferace activity

26
Q

isolated bilirubinemia what to investigate next

A

MCV Hb for hemoglobinopathy
G6PD for g6pd deficiency
Reticulocyte count for hemolysis

27
Q

which autoantibody is associated with PBC

A

AMA - antimitochondrial antibodies

28
Q

Reasons for HBV chronicity in neonates

A

Host factors
- failure of host to recognize infected hepatocytes cuz antigen is covered by maternal antiHBc
Viral factors
- excessive production of HBsAg –> modulation of immune signalling pathways
- HBx proteins inhibit degradation of viral protein –> reduce antigen presentation
- polymerase protein suppress immunity
- precore/HBeAg downregulates immunity

29
Q

HBsAg +
AntiHBs -
AntiHBc +

A 
acute infection (IgM anti-HBc +)
chronic carriers (IgM anti-HBc -)
30
Q

HBsAg +
AntiHBs -
AntiHBc -

A

very early phase of incubation period of acute infection

31
Q

HBsAg -
AntiHBs +
AntiHBc -

A

past infection

post vaccination

32
Q

HBsAg -
AntiHBs -
AntiHBc +

A

acute infection (IgM antiHBc +)
past infection
occult infection

33
Q

HBsAg -
AntiHBs +
AntiHBc +

A

Past infection

occult infection

Block A (11 decks)

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