2015.04.08

Question 1

Linkage disequilibrium

Answer 1

two allele loci are in linkage disequilibrium when a pair of alleles are inherited together in the same gamete more ore less often than would be expected given random chance.

Can occur even if genes are on different chromosomes.

Question 2

Contralateral homonymous hemianopia with macular sparing

Answer 2

Lesions of occipital cortex (eg, posterior cerebral artery occlusion)

Question 3

When are alpha-fetoprotein levels changed?

Answer 3

Elevated: multiple gestation, neural tube defects (spina bifida, anencephaly), abdominal wall defects (omphalocele).

Lowered: Down syndrome.

Question 4

Junctional Complex

Answer 4

1. Tight junctions (zonula occludens) at apices of glandular cells and consist of 2 closely adherent cytoplasmic membranes without an intervening space.
2. Intermediate junctions (zonula adherens) are a delicate network of cytoplasmic filaments that radiate from the cell membrane to hold adjacent cells together.
3. Desmosomes are samll, circular, adherent patches circumferentially placed around cells.

Question 5

Non-polar, hydrophobic amino acids

Answer 5

Valine, alanine, isoleucine, methionine, phenylalanine

Question 6

Aspiration of hydatid cysts

Answer 6

Inadvisable since the spilling of cyst contents within peritoneum can cause anaphylactic shock.

Surgery and chemotherapy (mebendazole or albendazole) is treatment of choice.

Question 7

Superior orbital fissure

Answer 7

CN III, V1 branches (nasociliary branch), CN VI, and superior ophthalmic vein enter the orbit via this fissure.

Question 8

Organophosphate poisoning

Answer 8

irreversibily inhibit cholinesterase in both muscarinic and nicotinic cholinergic synapses.

Pralidoxime is the only medication that reverses both muscarinic and nicotinic effects by “restoring” cholinesterase from its bond with organophosphates.

Atropine reverses muscarinic effects.

Question 9

Hawthorne Effect (Observer Effect)

Answer 9

Tendency of study subjects to change their behavior as a result of their awareness that they are being studied.

Question 10

Berkson’s bias

Answer 10

selection bias created by choosing hospitalized patients as the control group

Question 11

Pygmalion effect

Answer 11

Researcher’s beliefs in the efficacy of treatment can potentially affect the outcome.

Question 12

Screening vs. Diagnosing Treponema pallidum

Answer 12

RPR or VDRL are for screening. Patient’s serum is mixed with solution of cardiolipin, cholesterol and lecithin to detect presence of anti-cardiolipin in patients serum.

Confirmation: FTA-ABS. Detects antibodies directed against Treponema though indirect IF.

Question 13

Wolff-Parkinson-White Syndrome

Answer 13

Accessory AV conduction pathway that can manifeset clinically as recurrent paroxysmal supraventricular tachycardia.

ECG shows triad of abnormalities corresponding to ventricular pre-excitation: shortened PR-interval, delta wave at start of QRS complex, and widened QRS interval.

Question 14

Inulin vs. PAH

Answer 14

Inulin is filtered only - estimates GFR

PAH is filtered and secreted - estimates RPF

Question 15

Leydig cells

Answer 15

Produce testosterone in response to stimulation by luteinizing hormone (LH). LH is released from the anterior pituitary in response to GnRH from the hypothalamus.

Through a negative feedback, testosterone inhibits both LH and GnRH release.

Analogous to female thecal cells.

Question 16

Sertoli Cells

Answer 16

Produce inhibin in response to FSH from the anterior pituitary. Inhibin suppresses FSH production by the anterior pituitary, but does not feedback on the hypothalamus.

Main spermatogenesis, secrete Mullerian inhibiting factor during male embryogenesis.

Analagous to female granulosa cells.

Question 17

Antiphospholipid Antibody Syndrome

Answer 17

30% of patients with SLE (glomerulonephritis, photosensitive skin rash, arthralgias in young woman) have antiphosopholipid antibodies.

Venous or arterial thromboembolic disease - DVT, PE, IS/TIA

Adverse pregnancy outcomes - unexplained fetal loss, premature birth due to placental insufficiency or preeclampsia.

Labs: Lupus anticoagulant effect; paradoxical aPTT prolongation. Presence of anticardiolpin and beta-2-glycoprotein-I antibody.

Question 18

MEN type 2B

Answer 18

Medullary carcinoma of thyroid (calcitonin), pheochromocytoma, Marfanoid habitus/Mucosal neuromas.

Question 19

MEN 1

Answer 19

Parathyroid tumor (hypercalcemia)

Pancreatic tumor (gastrin)

Pituitary adenoma (prolactin, ACTH)

Question 20

Wilson’s Disease

Answer 20

cystic degeneration of the putamen as well as other basal ganglia structures.

Question 21

RBCs filled with multiple, smaller round nucleated cells suggests?

Answer 21

Plasmodia (malaria) infection.

Erythrocytic forms of this paracyte can be treated with: Chloroquine or mefloquine.

Primaquine is required for P. vivax and P. ovale liver schizonts.

Question 22

K excretion/reabsorption

Answer 22

K depletion stimulates alpha-intercalated cells to reabsorb extra potassium.

Principle cells secrete K under condtions of normal or increased K load.

Question 23

Entacapone vs. Tolcapone

Answer 23

COMT inhibitors

Entacapone - inhibits peripheral methylation.

Tolcapone - inhibits both peripheral and central methylation. Associated with hepatotoxicity.

Question 24

Arnold-Chiari malformation

Answer 24

Congential disease due to underdevelopment of the posterior fossa.

Causes cerebellum and medulla to hermiate through the foramen magnum.

Type I: low-lying cerebellar tonsils extend below the foramen magnum into the vertebral canal. Headaches and cerebellar symptoms.

Type II: compression of medulla - difficulty swallowing, dysphonia, stridor, and apnea. Severe and evident in newborn.

Question 25

Wegener’s (Granulomatosis with polyangiitis)

Answer 25

1. Pulmonary symptoms - cough/hemoptysis due to focal necrotizing granulomas in the lung.
2. Involvement of the URT.
3. Renal disease - rapidly progressive (crescentic) glomerulonephritis (RPGN).

Positive for c-ANCA (cytoplasmic antineutrophil cytoplasmic antibody) - autoantibody against lysosomal enzymes of human neutrophils and monocytes.

Question 26

How do thiazides increase Ca2+ reabsorption?

Answer 26

1. Inhibition of Na/Cl cotransporter on the apical side of DCT decreases intracellular Na concentrations and activates the Na/Ca2+ antiporter resulting in decrease of intracellular Ca2+ concentration and enhanced luminal Ca2+ reabsorption.
2. Hypovolemia induced by thiazides increases Na+ and H2O reabsorption in the proximal tubule, leading to passive increase in paracellular Ca2+ reabsorption.

Question 27

Saddle Embolus

Answer 27

Straddles the bifurcation of the main pulmonary artery. Cause is DVT.

Arises from Virchow’s triad of endothelial injury, venous stasis, and hypercoagulable state.

Question 28

Pancoast Tumors

Answer 28

Located in lung apex (superior sulcus).

Characterized by ispilateral Horner’s syndrome (ipsilateral ptosis, miosis, and anhydrosis), rib destruction, atrophy of hand muscles, and pain in the distribution of C8, T1 and T2 nerve roots.

Question 29

Measles vs. Rubella

Answer 29

Both have maculopapular rash that begins on face and spreads to trunk and extremeities.

Rubeola (measoles) - Paramyxovirus.

Rubella - Togavirus. Has postauricular and occipital lymphadenopathy.