Deck XIV

Question 1

In a-fib, what regulates the number of atrial impulses that reach the ventricle?

Answer 1

The AV node refractory period determines the number of impulses that reach the ventricle and determines ventricular contraction rate.

Question 2

What is hepcidin?

Answer 2

An acute phase reactant synthesized by the liver that acts as the central regulator of iron homeostasis

Question 3

What is ferroportin?

Answer 3

A transmembrane protein responsible for transferring intracellular iron to circulation.

Question 4

Describe the two paths for iron once inside the intestinal cells.

Answer 4

1. it may bind to ferritin to be stored within an enterocyte. It is excreted in the stool as enterocytes slough off and are replaced; 2. It may enter circulation through ferroportin; free iron in circulation is transported by transferrin.

Question 5

How is hepcidin synthesized?

Answer 5

By hepatic parenchymal cells. Synthesis is increased in inflammatory conditions and is lowered in states of hypoxia and erythropoiesis.

Question 6

How do low hepcidin concentrations affect iron absorption?

Answer 6

Low hepcidin levels increase intestinal iron absorption and stimulate iron release by macrophages.

Question 7

In Burkitts lymphoma, what gene is translocated and what is its function?

Answer 7

Translocation of the c-myc oncogene on the long arm of chromosome 8 with the Ig heavy chain region on chromosome 14. C-myc is a nuclear phosphoprotein that functions as a transcription factor which controls cell proliferation, differentiation, and apoptosis.

Question 8

What is deficient in a patient with acute intermittent porphyria?

Answer 8

Porphobilinogen (PBG) deaminase deficiency

Question 9

How does acute intermittent porphyria present?

Answer 9

Acutely with GI and neurologic symptoms, most commonly abdominal pain, vomiting, peripheral neuropathy, neuropsych derangements. Key feature is reddish urine that darkens on exposure to light and air due to oxidation of excess PBG.

Question 10

What is the target of treatment and prevention of acute porphyria attacks?

Answer 10

Inhibition of ALA synthase (rate limiting enzyme of heme synthesis) to reduce formation of toxic intermediate metabolites. Avoid CYP450 inducers, alcohol, smoking; tx with IV heme administartion and carbohydrate loading such as dextrose infusion.

Question 11

How does CO affect PaO2?

Answer 11

It does not affect this value. It only affects the amount of oxygen that can bind to hemoglobin and PaO2 in CO poisioning is typically normal.

Question 12

What side effects are associated with ticlopidine?

Answer 12

Neutropenia, fever, mouth ulcers.

Question 13

Auer rods are found in what type of cells?

Answer 13

Myeloblasts in AML

Question 14

What is the mechanism of Heparin?

Answer 14

It increases the effect of antithrombin III.

Question 15

What is measured to monitor the therapeutic effect of heparin?

Answer 15

aPTT (activated partial thromboplastin time).

Question 16

What is protamine sulfate used to treat?

Answer 16

Heparin toxicity (not effective in LMW heparins)

Question 17

What is the function of aminocaproic acid treatment?

Answer 17

To inhibit fibrinolysis.

Question 18

To what drug class does enoxaparin belong?

Answer 18

Low molecular weight heparin. It functions by binding and activating antithrombin III.

Question 19

How does antithrombin III produce an anticoagulant effect?

Answer 19

By reducing thrombin production through binding to factor Xa to stop the conversion of prothrombin to thrombin.

Question 20

What adverse effects are associated with Non-nucleotide RT inhibitors?

Answer 20

Abrupt flulike symptoms, abdominal pain, jaundice, fever may indicate hepatic failure and encephalopathy. These effects are most common within the first 6 weeks of therapy. Stevens- Johnson syndrome has also been observed.

Question 21

How are nonnucleoside reverse transcriptase inhibitors (NNRTIs) activated?

Answer 21

They do not require activation via intracellular phosphorylation.

Question 22

Name the three most common NNRTI drugs.

Answer 22

Nevirapine, efavirenz, delavirdine.

Question 23

HIV fusion inhibitor drugs function by what mechanism?

Answer 23

Selective binding to HIVs transmembrane envelope protein gp41

Question 24

What is the mechanism of action of enfuvirtide?

Answer 24

Binds to the heptad repeat 1 (HR1) of gp41 preventing gp41 from undergoing conformational changes necessary for viral membrane fusion with the target cellular membrane. This denies HIV genome entry into uninfected CD4+ T cells.

Question 25

What is the mechanism of action of aspirin?

Answer 25

Irreversible inhibition of COX1 and COX2 through acetylation of the COX enzymes. At low doses, aspirin inhibits COX1 alone but at high doses it inhibits both COX 1 and COX2.

Question 26

What drug is used to terminate early (<6 weeks gestational age) ectopic pregnancies?

Answer 26

Methotrexate

Question 27

What does methotrexate inhibit?

Answer 27

Competitive and irreversible inhibition of dihydrofolate (DHF) reductase. This causes accumulation of dihydrofolic acid polyglutamate within treated cells.

Question 28

Where in the prostate does prostate adenocarcinoma typically originate?

Answer 28

The peripheral zone of the prostate and can thus be detected on digital rectal examination as an asymmetric nodular enlargement of the prostate.

Question 29

What is characteristic of a peripheral blood smear in a patient with lead poisioning?

Answer 29

Coarse basophilic stippling on the background of hypochromic microcytic anemia. Basophilic stippling is the result of ribosome aggregation.

Question 30

What is inhibited in lead poisioning?

Answer 30

delta-ALA dehydratase. This causes reduced incorporation of iron into heme and decreased hemoglobin synthesis.