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NBME 7 block 2 q 1 to 50 - maryam2009
#51
37.E
Transcytosis is the process by which various macromolecules are transported across the interior of a cell. Vesicles are employed to intake the macromolecules on one side of the cell, draw them across the cell, and eject them on the other side. While transcytosis is most commonly observed in cells of an epithelium, the process is also present elsewhere. Blood capillaries are a well-known site for transcytosis, though it occurs in other cells, including neurons, osteoclasts and intestinal cells.
Eg : Insulin and Antibodies.
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#52
38. D
Peripheral neuropathy and CNS effects are associated with the use of isoniazid and are due to pyridoxine (vitamin B6) depletion, but are uncommon at doses of 5 mg/kg. Persons with conditions in which neuropathy is common (e.g., diabetes, uremia, alcoholism, malnutrition, HIV-infection), as well as pregnant women and persons with a seizure disorder, may be given pyridoxine (vitamin B6) (10–50 mg/day) with isoniazid.
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#53
39.AA

FF=GFR/RPF.......Angiotrensine II constricts the efferent a. ....>.inc GFR....>inc FF
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#54
40.AA

The normal PR interval is from 120 ms to 200 ms in length.

The drugs that most commonly cause first-degree heart block are those that increase the refractory time of the AV node, thereby slowing AV conduction.
These include calcium channel blockers, beta-blockers, cardiac glycosides, and anything that increases cholinergic activity such as cholinesterase inhibitors.

***CCB***
The calcium channel blockers known as
1. Non-dihydropyridines decrease the force of contraction of the myocardium
such as verapamil or diltiazem, may be avoided (or used with caution) in individuals with cardiomyopathy.
2.Dihydropyridine calcium channel blockers are often used to reduce systemic vascular resistance and arterial pressure, but are not used to treat angina...such as Nefidipin

Many calcium channel blockers also slow down the conduction of electrical activity within the heart, by blocking the calcium channel during the plateau phase of the action potential of the heart.
This results in a negative chronotropic effect, or a lowering of heart rate. This can increase the potential for heart block.This results in a negative chronotropic effect, or a lowering of heart rate. This can increase the potential for heart block.

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#55
41.BB

Anti-dig Fab fragments is an antidote for Cardiac glycosides toxicity

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#56
42.DD

Changes in the variables in Starling's equation can contribute to the formation of edema either by an increase in hydrostatic pressure within the blood vessel, a decrease in the oncotic pressure within the blood vessel or an increase in vessel wall permeability. The latter has two effects. It allows water to flow more freely and it reduces the oncotic pressure difference by allowing protein to leave the vessel more easily.
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#57
43.CC

P pili mediate the binding of uropathogenic E. coli to a digalactoside receptor determinant present in the urinary tract epithelium.
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#58
44.DD

No visible change by light microscopy in first 2-4 hours
contraction bands visible after 1-2 hours ..early coagulative necrosis after 4 hours.release of contents of necrotic cells into blood stream and the beginnig of neutrophil emigration
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#59
45.BB

Normal portal pressure is generally defined between 5 and 10 mm Hg. However, once the portal pressure rises to 12 mm Hg or greater, complications can arise, such as varices and ascites.
Treathment is

1.by diuretic drugs

2.by surgery to join the portal vein to the inferior vena cava (bypassing the liver)

3.implanting a stent within the liver to join portal tract veins to a hepatic vein tributary (TIPSS - transcutaneous intrahepatic porto-systemic shunt)




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#60
46.CC

Cohort study
It is observational and prospective.....compares between a group with a given risk factors.(Bus driveres......driving in seated position during 20 years) to a group without to assess (Bus condactors ...walking...)whether the risk factor increase the liklihood(MI) of disease.
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