5/25 Mixed

Question 1

Pufferfish poisoning

Answer 1

Caused by TETRODOTOXIN, a neurotoxin produced by microorganisms associated with the fish
Tetrodotoxin binds to voltage-gated SODIUM channels in nerve and cardiac tissue, preventing sodium influx and depolarization

Question 2

Obstructive lesion in a mainstem bronchus

Answer 2

Can prevent ventilation of an entire lung, leading to obstructive atelectasis and complete lung collapse
Characteristic findings on chest x-ray include unilateral pulmonary opacification and deviation of the mediastinum toward the opacified lung
Ex. central lung tumors in chronic smokers

Question 3

Leukocyte adhesion deficiency

Answer 3

Absence of CD18 antigens necessary for the formation of integrins, which are essential for leukocyte adhesion to endothelial surfaces and migration to peripheral tissues
Clinical features are caused by failure of leukocyte chemotaxis and include recurrent skin and mucosal infections WITHOUT PURULENCE, delayed separation of the umbilical cord, PERSISTENT LEUKOCYTOSIS

Question 4

Aortic regurgitation

Answer 4

High-pitched, blowing descrescendo diastolic murmur that begins immediately after closure of the aortic valve and is best heart along the left sternal border at the third and fourth intercostal spaces while the patient is sitting up and leading forward with the breath held in end expiration

Question 5

Aminoglycosides

Answer 5

Inhibit genetic code reading and protein synthesis by binding to the prokaryotic 30S ribosomal subunit
Can be used to Rx enterococcal endocarditis
Can cause ototoxicity and nephrotoxicity

Question 6

Malabsorption

Answer 6

Syndrome of impaired intestinal digestion and absorption
Fats are typically the most severely affected macronutrient in generalized malabsorption, and testing the stool for fat (eg, with Sudan III stain) is the most sensitive strategy to screen for malabsorptive disorders

Question 7

A method to reduce the worldwide incidence of hepatocellular carcinoma

Answer 7

Universal vaccination of children against HBV

Question 8

B-hCG

Answer 8

Produced by the syncytiotrophoblast after implantation, generally occurs 6-7 days after fertilization at the earliest
B-hCG typically is detectable in the maternal serum 8 DAYS AFTER FERTILIZATION, whereas it is detectable in the urine 14 DAYS after ferililization

Question 9

Vibrio cholerae

Answer 9

Causes a purely toxin-mediated watery diarrhea
Toxin secreted by these organisms modify electrolyte handling by enterocytes but do not cause cell death; therefore no erythrocytes or leukocytes are typically noted on stool microscopy
MUCUS AND SOME SLOUGHED EPITHELIAL CELLS

Question 10

Acute hepatitis B

Answer 10

Can cause a serum sickness-like syndrome with joint pain, lymphadenopathy and a pruritic urticarial rash, RUQ pain, hepatomegaly, elevated hepatic transaminase levels

Question 11

Breast milk contains all vitamins and trace minerals in adequate amounts except

Answer 11

Vitamins D and K
Vitamin K is given parenterally to all newborns at birth to prevent hemorrhagic disease of the newborn
Exclusively breastfed infants require Vitamin D supplementation due to lack of sunlight exposure and to prevent rickets

Question 12

Patients with adult type coarctation of the aorta commonly die of…

Answer 12

HTN associated complications, including left ventricular failure, ruptured dissecting aortic aneurysm, and intracranial hemorrhage.
These patients are at increased risk for ruptured intracranial aneurysms because of the increased incidence of congenital berry aneurysms of the Circle of Wills as well as aortic arch hypertension

Question 13

Peroxisomal disease

Answer 13

Rare inborn errors of metabolism where peroxisomes are either absent or nonfunctional
VERY LONG CHAIN FATTY ACIDS OR FATTY ACIDS WITH BRANCH POINTS AT ODD-NUMBERED CARBONS can not undergo mitochondrial beta-oxidation; these fatty acids are metabolized by a special form of beta oxidation (VLCFA) or by alpha oxidation (BCFA such as phytanic acid) within peroxisomes.
These disease commonly lead to neurologic defects from improper CNS myelination

Question 14

Vasovagal syncope after stimulation of the posterior external auditory canal by an otoscope speculum

Answer 14

Parasympathetic outflow via the vagus nerve leads to decreased heart rate and BP
Vagus nerve provides cutaneous sensation to the posterior external auditory canal via its small auricular branch
Sensation to the rest of the canal is from the mandibular division of the trigeminal nerve

Question 15

WHAT IS THE SINGLE MOST IMPORTANT RISK FACTOR FOR THE DEVELOPMENT OF INTIMAL TEARS LEADING TO AORTIC DISSECTION??

Answer 15

HYPERTENSION!!!!

Smoking, diabetes, and hypercholesterolemia are other major risk factors for atherosclerosis which predisposes more to aortic aneurysm formation that aortic dissection

Question 16

X-inactivation

Answer 16

Occurs in genetically normal females and results in conversion of the inactivated X chromosome into compact heterchromatin (Barr body)
Heterochromatin is condensed chromatin composed of heavily methylated DNA in tight association with deacetylated histones
It has a low level of transcriptional activity
In contrast, euchromatin is loosely arranged and exhibits a high levels of transcriptional activity

Question 17

Essential fructosuria (Fructokinase deficiency)

Answer 17

Benign Disorder
Affected patients are asymptomatic, but their urine will test positive for a reducing sugar due to the presence of unmetabolized fructose

Repeatedly positive copper reduction test

Question 18

Leuprolide

Answer 18

GnRH analog - given continuously will suppress pituitary LH release and lead to reduced production of testosterone
(5 a reductase converts testosterone to DHT, so as levels of T fall, DHT will fall too)
Will cause a transient increase in pituitary LH secretion and a rise in testosterone

Question 19

Vomiting reflex

Answer 19

Regulated mainly by 5 receptors: M1 muscarinic, D2 dopaminergic, H1 histaminic, 5-HT3 serotonergic, and neurokinin 1 (NK1) receptors
5-HT3 and NK1 receptor antagonists are particularly useful for chemo induced vomiting

Question 20

Gas anesthetics

Answer 20

Onset of action depends on its solubility in the blood (blood/gas partition coefficient)
Drugs with high blood/gas partition coefficients are more soluble in the blood, demonstrate slower equilibrium with the brain and have longer onset times

Question 21

Enterococcus mechanism of resistance against aminoglycosides

Answer 21

Enterococci produce aminoglycoside-modifying enzymes that transfer different chemical groups (acetyl groups, adenyl groups, phosphate groups) to the aminoglycoside molecule and therefore impair antibiotic binding to ribosomal subunits

Question 22

Injury to the posterior urethra is associated with pelvic fractures
Anterior urethra is most commonly damaged in straddle injuries

Answer 22

Inability to void with a full bladder sensation, a high-riding boggy prostate and blood at the urethral meatus are suggestive of urethral injury, particularly in the presence of pelvic fracture
If urethral injury is suspected, placement of a Foley catheter is contraindicated
Membranous segment is relatively unsupported by adjacent tissues and is the weakest point of the posterior urethra

Question 23

Succinylcholine

Answer 23

Fast acting, DEPOLARIZING neuromuscular blocking agent used for rapid-sequence intubation that causes equal reduction of all 4 twitches during train of four stimulation (phase I blockade).
Prolonged administration of succinylcholine or use in patients with abnormal plasma cholinesterase activity causes transition to phase II (nondepolarizing) block, seen as a progressive reduction in each of the 4 twitches

Question 24

EBV

Answer 24

Commonly infects B cells, stimulating them to proliferate continuously (“transformation” or “immortalization”.
EBV is an oncogenic virus that promotes polyclonal B cell proliferation and heterophile antibody production
The heterophile antibody test is sensitive and highly specific for EBV infection

Question 25

Normal morphological changes in the aging heart

Answer 25

Decrease in left ventricular chamber apex-to-base dimension, development of sigmoid-shaped ventricular septum, myocardial atrophy with increased collagen deposition, and accumulation of cytoplasmic lipofuscin pigment within cardiomyocytes

Question 26

Increased laxity of the knee with the valgus stress test indicates

Answer 26

Injury to the medial collateral ligament