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NBME 7 block 3 q 1 to 50 - maryam2009
#41
34. A
A complete mole is caused by a single sperm combining with an egg which has lost its DNA (the sperm then redupplicates forming a "complete" 46 chromosome set) The genotype is typically 46,XX (diploid) due to subsequent mitosis of the fertilizing sperm, but can also be 46,XY (diploid).
In contrast, a partial mole occurs when an egg is fertilized by two sperm or by one sperm which reduplicates itself yielding the genotypes of 69,XXY (triploid) or 92,XXXY (quadraploid). Complete hydatidiform moles have a higher risk of developing into choriocarcinoma -- a malignant tumor of trophoblast cells -- than do partial moles.
Choriocarcinoma is a malignant, trophoblastic and aggressive cancer, usually of the placenta. It is characterized by early hematogenous spread to the lungs. It belongs to the far end of the spectrum of gestational trophoblastic disease (GTD), a subset of germ cell tumors.
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#42
Hi there,you are so fast...thank you Smile
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#43
35.D
Pyelonephritis is an ascending urinary tract infection that has reached the pyelum (pelvis) of the kidney. If the infection is severe, the term "urosepsis" is used interchangeably (sepsis being a systemic inflammatory response syndrome due to infection). It requires antibiotics as therapy, and treatment of any underlying causes to prevent recurrence. It is a form of nephritis. It can also be called pyelitis.
Severe cases of pyelonephritis lead to sepsis, a systemic response to infection characterized by fever, a raised heart rate, rapid breathing and decreased blood pressure (occasionally leading to septic shock). When pyelonephritis or other urinary tract infections lead to sepsis, it is termed urosepsis.
Most cases of "community-acquired" pyelonephritis are due to bowel organisms that enter the urinary tract. Common organisms are E. coli (70-80%) and Enterococcus faecalis. Hospital-acquired infections may be due to coliforms and enterococci, as well as other organisms uncommon in the community (e.g. Klebsiella spp., Pseudomonas aeruginosa). Most cases of pyelonephritis start off as lower urinary tract infections, mainly cystitis and prostatitis.
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#44
U well come ...
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#45
36.D
The posterior inferior cerebellar artery (PICA), the largest branch of the vertebral artery, is one of the three main arterial blood supplies for the cerebellum.

It winds backward around the upper part of the medulla oblongata, passing between the origins of the vagus and accessory nerves, over the inferior cerebellar peduncle to the undersurface of the cerebellum, where it divides into two branches.
The medial branch continues backward to the notch between the two hemispheres of the cerebellum; while the lateral supplies the under surface of the cerebellum, as far as its lateral border, where it anastomoses with the anterior inferior cerebellar and the superior cerebellar branches of the basilar artery.
Branches from this artery supply the choroid plexus of the fourth ventricle.
Diseases

Infarction of this artery due to thrombosis or a stroke leads to lateral medullary syndrome, also known as PICA syndrome or Wallenberg syndrome. Severe occlusion of this or vertebral arteries could lead to Horner's Syndrome as well.
http://upload.wikimedia.org/wikipedia/co...lis_en.svg
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#46
35.DD

Acute pyelonephritis is a potentially organ- and/or life-threatening infection that characteristically causes some scarring of the kidney with each infection and may lead to significant damage to the kidney (any given episode), kidney failure, abscess formation (eg, nephric, perinephric), sepsis, or sepsis syndrome/shock/multiorgan system failure.

Most cases of "community-acquired" pyelonephritis are due to bowel organisms that enter the urinary tract. Common organisms are E. coli (70-80%) and Enterococcus faecalis.

Antibiotics are the mainstay of treatment. Mild cases may be treated with oral therapy, but generally intravenous antibiotics are required for the initial stages of treatment. The type of antibiotic depends on local practice, and may include fluoroquinolones (e.g. ciprofloxacin), beta-lactam antibiotics (e.g. amoxicillin or a cephalosporin), trimethoprim (alone or in combination with sulfamethoxazole). Aminoglycosides are generally avoided due to their toxicity, but may be added for a short duration.

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#47
37.A
Lambert-Eaton myasthenic syndrome (LEMS) main causal cancer small-cell lung cancer
In LEMS, antibodies against VGCC, particularly the P/Q-type VGCC, decrease the amount of calcium that can enter the nerve ending, hence less acetylcholine can be mobilized to the neuromuscular junction. Apart from skeletal muscle, the autonomic nervous system also requires acetylcholine neurotransmission; this explains the occurrence of autonomic symptoms in LEMS. P/Q voltage-gated calcium channels are also found in the cerebellum, explaining why some experience problems with coordination. Antibodies may also bind other VGCCs. Many people with LEMS, both with and without VGCC antibodies, have detectable antibodies against the M1 subtype of the acetylcholine receptor; it is thought that their presence participates in a lack of compensation for the slow calcium influx.
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#48
38.C
Glycogen storage disease type I (GSD I) or von Gierke's disease, is the most common of the glycogen storage diseases. This genetic disease results from deficiency of the enzyme glucose-6-phosphatase. This deficiency impairs the ability of the liver to produce free glucose from glycogen and from gluconeogenesis. Since these are the two principal metabolic mechanisms by which the liver supplies glucose to the rest of the body during periods of fasting, it causes severe hypoglycemia. Reduced glycogen breakdown results in increased glycogen storage in liver and kidneys, causing enlargement of both. Both organs function normally in childhood but are susceptible to a variety of problems in the adult years. Other metabolic derangements include lactic acidosis and hyperlipidemia. Frequent or continuous feedings of cornstarch or other carbohydrates are the principal treatment. Other therapeutic measures may be needed for associated problems.
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#49
39.AA

ACE inhibitors reduce the progress of diabetic nephropathy independently from their blood pressure-lowering effect.This action of ACE inhibitors is used in the prevention of diabetic renal failure.
ACE inhibitors block the conversion of angiotensin I to angiotensin II.
Under normal conditions, angiotensin II will constrict the efferent arterioles of the kidney leads to increased perfusion pressure in the glomeruli....>inc GFR.

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#50
40.EE

Thromboxane A2 (TXA2), produced by activated platelets, has prothrombotic properties, stimulating activation of new platelets as well as increasing platelet aggregation.

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