UWorld Test Review 5

Question 1

almost all aminotransferases use ______ as the amino group acceptor, so that amino groups can be funneled into glutamate during protein catabolism

Answer 1

almost all aminotransferases use alpha-ketoglutarate as the amino group acceptor, so that amino groups can be funneled into glutamate during protein catabolism

glutamate is then metabolized in the liver to form urea, the primary form of nitrogen disposal

Question 2

____ is the major amino acid responsible for transferring nitrogen to the liver for disposal

Answer 2

alanine - combines with alpha-ketoglutarate to form pyruvate + glutamate (via transamination, requiring B6)

glutamate then is broken down to NH3 (ammonia), which enters urea cycle (via glutamate dehydrogenase)

Question 3

the blood vessels supplying the ovary run through which ligament?

Answer 3

infundibulopelvic ligament (aka suspensory ligament) - at risk for occlusion by ovarian torsion

connects the ovaries to the pelvic sidewall

Question 4

F neonate with posterior neck mass composed of cystic spaces separated by connective tissue + bilateral non-pitting edema of hands and feet + low-set ears and high-arched palate + diminished femoral pulses = ?

Answer 4

Turner Syndrome (45,X)

neck mass = cystic hygroma, caused by obstruction of lymphatic system

non-pitting edema due to impaired lymphatic flow

diminished femoral pulses = aortic coarctation

other features/complications of TS = webbed neck, low hairline, broad chest with widely spaced nipples, horseshoe kidneys, streak ovaries, bicuspid aortic valve, aortic dissection

Question 5

what is the cause of atrial flutter and where does it typically occur anatomically?

Answer 5

caused by a large reentrant circuit in the area between the tricuspid valve and the inferior vena cava in the right atrium (cavotricuspid isthmus)

Question 6

explain why Haemophilus influenzae will only grow on sheep blood agar if cross-streaked with Staph. aureus

Answer 6

Haemophilus requires X factor (hematin) and V factor (NAD+) to grow - these are lacking in sheep blood agar

however, Staph. aureus secretes V factor (NAD+) and facilitates the release of X factor (hematin) from beta-hemolysis-induced erythrocyte lysis

this provides the needed nutrients for Haemophilus growth (“satellite phenomenon”)

Question 7

patients with cleft lip and palate often have recurrent otitis media due to dysfunction of which muscle?

Answer 7

levator veli palatini - responsible for opening the eustachian tube

Question 8

what does serology show in limited cutaneous (CREST) vs diffuse cutaneous systemic sclerosis?

Answer 8

CREST = anticentromere Abs

diffuse = anti-Scl-70 Abs (anti-topoisomerase type I)

Question 9

woman who recently gave birth presenting with decreased serum TSH and free thyroxine (T4) levels should raise suspicion of…

Answer 9

Sheehan syndrome: pituitary infarction due to ischemic necrosis (caused by systemic hypotension during delivery)

decreased TSH is important because it indicates the hypothyroidism is secondary, NOT primary (like postpartum thyroiditis - would see high TSH)

Question 10

which cause of pneumonia causes hyponatremia? what will Gram stain show?

Answer 10

Legionella pneumophilia: Gram neg. bacillus, facultatively intracellular —> staining shows many neutrophils but few organisms

most common lab abnormality is hyponatremia, distinguishing from other causes of pneumonia - likely due to ADH secretion or impaired renal Na+ reabsorption

Legionnaire’s disease (via contaminated water) - presents with pneumonia (patchy infiltrates), high fever, bradycardia, neuro symptoms (confusion, headache), GI symptoms (watery diarrhea)

Question 11

patient with mono-like symptoms, but serum fails to agglutinate horse erythrocytes… most likely dx?

Answer 11

horse erythrocyte agglutination = Monospot test (for EBV)
[can also use sheep erythrocytes in Paul-Bunnell test]

in immunocompetent patients with heterophile antibody-negative mononucleosis-like syndrome, most likely dx is cytomegalovirus (CMV) infection, which may be acquired via blood transfusion

[other less common causes = HHV6, HIV, toxoplasmosis]

Question 12

From which foramina do CN V-XII exit?

Answer 12

CN V1 = superior orbital fissure
CN V2 = foramen rotundum
CN V3 = foramen ovale
CN VII, VIII = internal acoustic meatus
CN IX, X, XI = jugular foramen
CN XII = hypoglossal canal

Question 13

what exits from foramen spinosum?

Answer 13

middle meningeal artery + vein

Question 14

57yo F w/ cough and hemoptysis. She also reports several months of fatigue and joint pain. PE shows crusting of nasal mucosa, lung crackles, and scattered palpable purpura over the lower extremities. CXR shows bilateral, diffuse alveolar infiltrates. Labs show normocytic anemia, and urine is positive for RBC casts and proteinuria. She is positive for c-ANCA. What is the dx?

Answer 14

granulomatosis with polyangiitis: c-ANCA positive inflammatory vasculitis that primarily attacks the upper and lower respiratory tract, kidneys, and skin

Question 15

what are the 2 phases of the PPP and their purposes?

Answer 15

oxidative/irreversible phase: glucose-6-phosphate —> 6-phosphogluconate (via glucose-6-phosphate dehydrogenase, rate-limiting) —> ribulose-5-phosphate (via another dehydrogenase)… both steps produce NADPH for glutathione and cholesterol/FA synthesis

non-oxidative/reversible phase: ribulose-5-phosphate used as a substrate for nucleotide synthesis; in addition, fructose-6-phosphate is generated for glycolysis

Question 16

give an anatomical description of where the AV node is

Answer 16

interatrial septum near the opening of the coronary sinus

Question 17

which bacteria produces lecithinase?

Answer 17

lecithinase = alpha toxin, produced by Clostridium perfringens

degrades lecithin (component of phospholipid membranes) —> membrane destruction, cell death, widespread necrosis + hemolysis

Question 18

which 2 molecules maintain coronary autoregulation?

Answer 18

allows coronary blood flow to be primarily driven by myocardial O2 demand over a wide range of perfusion pressures (60-140mmHg)

accomplished via alterations in vascular resistance mediated by adenosine and nitric oxide

Question 19

what is first-line treatment for Phthirus pubis (human pubic louse)?

Answer 19

topical permethrin: blocks parasite Na+ conduction in nerve cell membrane channels —> paralysis and death

Question 20

Vitamin K deficiency results in prolonged _____ time

Answer 20

Vitamin K activates coagulation factors II, VII, IX, and X, as well as proteins C and S

Vitamin K deficiency —> prolonged prothrombin time (PT) due to deficiency of factor VIIa (activated)

Question 21

what is the most important environmental risk factor for lung cancer, aside from cigarette smoke?

Answer 21

radon gas - found in soil and groundwater, emits highly ionizing alpha radiation —> DNA damage to respiratory tract epithelium when inhaled

Question 22

a patient with chronic HF w/ reduced ejection fraction is treated with a drug that works by inhibiting a metalloprotease to prolong the action of endogenous polypeptides… what drug is this?

Answer 22

neprilysin inhibitors (ex, sacubitril) —> enhanced activity of ANP and BNP (endogenous polypeptides)

[neprilysin = metalloprotease which breaks down ANP/BNP]

Question 23

explain how the following change with aging:
a. lung compliance
b. total respiratory system compliance
c. physiologic dead space

Answer 23

a. lung compliance - INCREASES due to loss of elastin (resembles mild emphysema)

b. total respiratory system compliance - DECREASES bc increased stiffness of chest wall dominates over increased compliance

c. physiologic dead space - INCREASES due to elastin degeneration + capillary dropout

Question 24

what makes Haemophilus influenzae type b (Hib) more invasive than other strains?

Answer 24

polyribosylribitol phosphate (PRP) capsule - inhibits complement mediated phagocytosis

[serotypes a-f are encapsulated, while nontypeable strains do not have a capsule - why they are nontypeable!!]

Question 25

on which cells are CD15 and CD16 found, respectively?

Answer 25

CD15 = granulocytes, also present on Reed-Sternberg cells (Hodgkin’s lymphoma) CD16 = low affinity Fc receptor on NK cells, neutrophils, and macrophages

Question 26

what murmur does a ventricular septal defect cause? include location

Answer 26

**holosystolic murmur** at the **lower left sternal border** (louder with small VSD due to more turbulence) small VSD will cause increase in RV SpO2, while large VSD allows for equalization between chamber pressures

Question 27

bifid carotid pulse with brisk upstroke =

Answer 27

**hypertrophic cardiomyopathy** - dynamic LV outflow tract obstruction during systole

Question 28

fixed splitting of S2 =

Answer 28

atrial septal defect (ASD)

Question 29

overlying skin retractions (puckering) caused by invasive breast carcinoma are due to involvement of…..

Answer 29

**suspensory ligaments** (Cooper ligaments) - extend out towards skin

Question 30

what is heard on cardiac auscultation in a patient with bicuspid aortic valve vs pulmonic stenosis?

Answer 30

bicuspid aortic valve - narrowed or paradoxical splitting of S2 pulmonic stenosis - widened splitting of S2

Question 31

horseshoe kidney is due to fusion of: a. mesonephric duct b. mesonephros c. metanephros d. pronephros e. urogenital ridge

Answer 31

c. **metanephros** *pronephros* = rudimentary nephric system, degenerates early in gestation *mesonephros* mostly degenerates, except *mesonephric duct* - persists as ureteric bud *urogenital ridge* - gives rise to nephric system + gonads/reproductive tract + and real cortex + kidney

Question 32

absence of CD40 ligand on CD4+ T cells =

Answer 32

**hyper-IgM syndrome**: CD4+ T cells cannot stimulate B cells to class switch/ differentiate into plasma and memory cells —> sinopulmonary infections, GI infections, failure to thrive (increased metabolic demands from being sick)

Question 33

HIV-1 vs HIV-2

Answer 33

HIV-1: worldwide, high viral load, 7-10 years progression to AIDs HIV-2: West Africa, low viral load (lower viremia), 10-25 years progression to AIDs

Question 34

describe the genital ulcers caused by: a. Haemophilus ducreyi b. Klebsiella granulomatis c. Chlamydia trachomatis (L serovars)

Answer 34

a. *Haemophilus ducreyi*: **chancroid** - deep, purulent, painful, progress from papule to ulcer, >1 present b. *Klebsiella granulomatis*: **granuloma inguinale** - painless, red, progressive, without lymphadenopathy c. *Chlamydia trachomatis* (L serovars): **lymphogranuloma venereum** - painless, but spreads to regional lymph nodes and causes painful lymphadenitis; rare in US, occurs in tropical/subtropical regions

Question 35

78yo M w/ progressive dyspnea, generalized weakness, palpitations, and tingling/numbness in lower limbs may have a deficiency of which vitamin?

Answer 35

**thiamine (B1)**: necessary for decarboxylation of alpha-keto acids (carbohydrate metabolism) dx: **beriberi**: peripheral neuropathy + heart failure [dry = just neuropathy, wet = neuropathy + cardiac]

Question 36

what is the most common site of blunt aortic injury (such as by high-speed motor accident), and why?

Answer 36

**aortic isthmus**, just distal to the attachment of the **ligamentum arteriosum** this section is relatively immobile compared to adjacent descending aorta - rapid deceleration can cause it to tear

Question 37

name 3 cancers that spread hematogenously

Answer 37

1. sarcomas 2. renal cell carcinoma 3. hepatocellular carcinoma

Question 38

which of the following is caused by a GOF mutation of a non-receptor tyrosine kinase protein in hematopoietic cells, leading to persistent activation of STAT proteins? a. acute promyelocytic leukemia b. chronic lymphocytic leukemia c. high-grade non-Hodgkin lymphoma d. mantle cell lymphoma e. primary myelofibrosis

Answer 38

e. **primary myelofibrosis**: mutation in **JAK2** (Janus kinase 2, non-receptor cytoplasmic tyrosine kinase) —> overactive tyrosine phosphorylation and activation of **STAT** pathway [same mutation causes essential thrombocytosis and polycythemia vera]

Question 39

child with hoarseness, respiratory distress, and polypoid growths in clusters on true vocal chords =

Answer 39

dx = *recurrent respiratory papillomatosis*: caused by **HPV serotypes 6 and 11** transmitted via sexual contact or reactivation of vertical transmission

Question 40

which hormone inhibits lactation during pregnancy despite high prolactin levels?

Answer 40

progesterone - drop following delivery allows lactation to occur

Question 41

what are the 3 actions of the recurrent branch of the median nerve?

Answer 41

1. thumb abduction (abductor pollicis brevis) 2. thumb flexion (flexor pollicis brevis) 3. thumb opposition (opponens pollicis) may be injured via lunate dislocation !

Question 42

recurrent focal impaired awareness seizures preceded by uneasy epigastric sensation or olfactory hallucination are characteristic of…

Answer 42

medial temporal lobe epilepsy - caused by hippocampal sclerosis, associated with childhood febrile illness

Question 43

what are the 2 metabolic fates of pyruvate? include enzymes required and end products

Answer 43

1. via **pyruvate carboxylase** —> oxaloacetate, substrate for gluconeogenesis 2. via **pyruvate dehydrogenase** —> acetyl-CoA, which enters TCA for ATP production

Question 44

16yo M presents with long/narrow face, prominent forehead/chin, large testes, hyperlaxity of the hand joints + developmental delay/ intellectual disability + ADHD/autism =

Answer 44

**fragile X syndrome**: X-linked TNR of **CGG** in *FMR1* gene —> hypermethylation

Question 45

describe how the concentrations of each of the following change along the length of the proximal tubule: a. creatinine b. bicarbonate c. urea d. glucose e. amino acids

Answer 45

**creatinine**: freely filtered + secreted, NOT reabsorbed —> rapidly increasing concentration in tubular fluid **urea**: freely filtered, poorly reabsorbed —> steady increase in concentration **bicarbonate**: actively reabsorbed (via carbonic anhydrase) —> steady decrease in concentration **glucose, amino acids**: avidly reabsorbed —> rapidly decreasing concentration CUBAG, or Creating Unnecessary Bigotry Gets Annoying

Question 46

most dangerous adverse effect of amphotericin B

Answer 46

**nephrotoxicity** - due to decrease in GFR and direct toxic effects on tubular epithelium watch out for anemia (decreased EPO production) and electrolyte imbalances (hypokalemia), which may cause weakness and arrhythmias

Question 47

which neurons of the CNS release serotonin? where are they located?

Answer 47

**Raphe nuclei** - disbursed throughout brainstem, axons project widely in CNS [if Ralphe had more serotonin, maybe he would be happier!]

Question 48

which neurons of the CNS produce norepinephrine? where are they located?

Answer 48

**Locus ceruleus** - located in dorsal pons [when LOCUS descended on the city, everyone got STRESSED (NE!) and ran]

Question 49

most common cause of eosinophilic meningitis

Answer 49

*Angiostrongylus cantonensis*: helminth in Southeast Asia and Pacific Islands transmitted via consumption of contaminated mollusks or snails

Question 50

what does imaging show in sporadic encephalitis caused by Herpes virus type 1?

Answer 50

inflammation/edema of temporal lobe

Question 51

GABA agonist used for anesthesia induction that is hemodynamically stable

Answer 51

**etomidate**: provides sedation and amnesia, does not cause changes in HR/BP/CO however, inhibits cortisol synthesis (adrenocortical suppression) - avoid in shock patients

Question 52

renal metabolism of which amino acid is most important for maximizing acid excretion?

Answer 52

**glutamine** - metabolism generates ammonium and bicarbonate bicarbonate is used to buffer acids in blood

Question 53

which antiarrhythmic preferentially binds to rapidly depolarizing myocardial fibers, with minimal effect on normal ventricular myocardium? a. adenosine b. diltiazem c. ibutilide d. lidocaine e. procainamide

Answer 53

**lidocaine**: class IB, weakest Na+ channel blockers (dissociate the fastest) - bind inactivated state, dissociate rapidly so they have negligible effect on QRS ischemic myocardium has less negative resting membrane potential, which delays recovery of Na+ channels from inactivated to resting… this allows for increased binding of IB agents therefore, Class IB anti-arrhythmics (lidocaine) are efficacious in inhibiting ischemia-induced ventricular arrhythmias

Question 54

when would you use procainamide vs lidocaine?

Answer 54

procainamide = Class IA anti-arrhythmic —> binds Na+ channels in open state, specific for suppressing arrhythmias from areas of normal automaticity lidocaine = Class IB anti-arrhythmic —> binds inactivated Na+ channels, specific for suppressing arrhythmias from areas of ischemic myocardium (having higher resting membrane potential)

Question 55

what is the treatment for warfarin vs heparin overdose?

Answer 55

warfarin overdose - Vitamin K (takes days) + **fresh frozen plasma** (contains all clotting factors) heparin overdose - **protamine** (binds heparin, forming inactive complex)

Question 56

why is fresh frozen plasma but not cryoprecipitate effective in treating warfarin overdose?

Answer 56

fresh frozen plasma (FFP): contains all clotting factors cryoprecipitate: precipitate obtained from FFP by centrifugation, contains factor VIII, factor XIII, vWF, and fibrinogen - does not replenish Vitamin K factors (II, VII, IX, X)

Question 57

for which hematological disorders is desmopressin used to treat?

Answer 57

increases plasma levels of vWF and factor VIII —> treats **hemophilia A** (VIII deficiency) and **von Willebrand disease**

Question 58

which of the following would be the most appropriate choice in an elderly patient? a. chlorpheniramine b. diphenhydramine c. hydroxyzine d. loratadine e. promethazine

Answer 58

d. **loratadine** = 2nd gen. antihistamine do not cause antimuscarinic/antiserotonergic/anti-alpha adrenergic side effects, less lipophilic and do not cross BBB (non-sedative) [all other options are first gen.]

Question 59

triad of fibrous dysplasia + endocrine abnormalities + cafe-au-lait spots =

Answer 59

**McCune-Albright syndrome**: mutation in GNAS gene (encodes alpha subunit of G protein) —> constitutive Gs activation and hormone overproduction

Question 60

which symptom of organophosphate poisoning will not resolve with atropine administration, and which therapy needs to be added to solve this?

Answer 60

organophosphates inhibit cholinesterase in both **muscarinic + nicotinic** synapses **atropine** is a competitive inhibitor of ACh at **muscarinic** synapses only —> will NOT treat MUSCLE WEAKNESS **pralidoxime** is a cholinesterase-reactivating agent —> treats **muscarinic + nicotinic**

Question 61

Pt presents w/ R leg pain, fever, confusion. Pt was injured while operating a motorized watercraft in Florida 2 days ago. Temp 102 (38.9), BP 90/50, pulse 120/min. PE shows a small laceration on the right foot w/ surrounding edema, erythema, and hemorrhagic bullae. Leukocyte count and lactic acid are elevated. Blood cultures reveal curved gram-negative rod. Which of the following is the greatest risk factor for this patient’s infection? a. condition causing iron overload b. exposure to infected rodent urine c. lack of booster immunization

Answer 61

dx = *Vibrio vulnificus*: curved Gram(-) rod, lives in salt water, ingested via raw oysters or wound infection; higher risk w/ **condition causing iron overload** (promotes growth) —> rapidly progressive septicemia and cellulitis (w/ hemorrhagic bullae and necrotizing fasciitis) b. exposure to infected rodent urine = Leptospira c. lack of booster immunization = Clostridium tetani

Question 62

how would you differentiate immune thrombocytopenia from von Willebrand factor deficiency?

Answer 62

both will have normal PT, normal PTT, and increased bleeding time **immune thrombocytopenia**: decreased platelet count, produces **episodic** mucocutaneous bleeding (petechiae, purpura, epistaxis), but NOT chronic **vWF deficiency**: normal platelet count, **lifelong history** of mucosal bleeding (gingival, epistaxis, menorrhagia)

Question 63

what does vWF bind to promote platelet adhesion?

Answer 63

binds/crosslinks **platelet glycoproteins (GpIb)** with exposed **collagen** underneath damaged endothelium

Question 64

Pt is a 42yo M, presents w/ recurrent syncope that is preceded by palpitations. PMH includes back injury, for which they take methadone. BP is 120/70 supine and 125/75 standing. What is the most likely cause of syncope in this patient?

Answer 64

**QT-prolongation** due to **methadone** - common adverse effect due to delayed rectifier K+ current… risk of triggering torsade de pointes other drug causes: macrolides, fluoroquinolones, antiemetics, azoles, antipsychotics/TCAs/SSRIs, methadone/oxycodone, Class IA and III anti-arrhythmic congenital causes: Romano-Ward (AD), Jervell & Lange-Nielsen (AR)

Question 65

serious side effects of statins include… (2)

Answer 65

1. myopathy 2. hepatitis - monitor liver transaminase levels

Question 66

29yo F presents w/ high fever and diffuse rash which began 5 days ago. She has also experienced headache, retroorbital pain, and joint/muscle pain. Pt returned from Brazil 10 days ago. PE shows diffuse maculopapular rash and scattered petechiae over her extremities. Labs show thrombocytopenia. What is the causative pathogen?

Answer 66

**dengue (Flavivirus)**: transmitted via *Aedes mosquitos*, prominent in tropical/subtropical regions of Asia and South America

Question 67

which infections are transmitted via *Aedes* mosquitos? (4)

Answer 67

1. dengue (Flavivirus) 2. yellow fever 3. Zika 4. chikungunya simultaneous outbreaks are common during rainy season

Question 68

when is finger clubbing observed?

Answer 68

cardiopulmonary diseases in which hypoxic-inflammatory pathways are activated —> release of growth factors (VEGF) including: lung adenocarcinoma (most common in adults), bronchiectasis (chronic infection), cyanotic heart defects

Question 69

in which patients are gallstones most likely?

Answer 69

“fat, fertile, female, forty” pregnancy/OC predisposes to gallstone formation due to estrogen-induced cholesterol hyper-secretion and progesterone induced hypomotility

Question 70

which of the following can improve survival in patients with congestive heart failure and reduced LV ejection fraction? a. acetazolamide b. furosemide c. hydrochlorothiazide d. spironolactone e. triamterene

Answer 70

d. spironolactone (mineralocorticoid receptor antagonists) note - should not be used in patients with hyperkalemia or renal failure (K+ sparing)

Question 71

polymyositis vs polymyalgia rheumatica

Answer 71

**polymyositis**: symmetric proximal muscle weakness, elevated CK and ANA Abs, biopsy shows endomysial mononuclear infiltrate w/ patchy necrosis **polymyalgia rheumatica**: myalgias (NOT weakness) of shoulder and pelvic girdle muscles, often w/ systemic symptoms (fever, weight loss), patients >50

Question 72

during orchiopexy (fixation of undescended testis in the scrotum), the testis are pulled through the superficial inguinal ring, a physiologic opening in the…

Answer 72

external oblique aponeurosis

Question 73

for which 4 enzymes is thiamine (B1) a cofactor?

Answer 73

1. **pyruvate dehydrogenase**: converts pyruvate into acetyl-CoA 2. **alpha-ketoglutarate dehydrogenase**: TCA cycle 3. **alpha-ketoacid dehydrogenase**: catabolism of branch-chained amino acids (leucine, isoleucine, valine) 4. **transketolase**: converts ribulose-5-phosphate to glyceraldehyde-3-phosphate (PPP)

Question 74

what is the cause of posterior urethral valves?

Answer 74

persistence of urogenital membrane (incomplete canalization) —> bladder outlet obstruction, vesicoureteral reflux, hydronephrosis

Question 75

a single temporal lobe abscess is usually a result of otitis media that spread to the ______, while frontal lobe abscess is usually due to ______ or _____ sinusitis

Answer 75

a single temporal lobe abscess is usually a result of otitis media that spread to the **mastoid air cells**, while frontal lobe abscess is usually due to **ethmoid** or **frontal** sinusitis

Question 76

what are 2 clinical uses of adenosine

Answer 76

1. vasodilator in chemical cardiac stress tests 2. fast acting anti-arrhythmic for stopping acute supra-ventricular tachycardias very short half-life

Question 77

which 5 drugs are associated with drug-induced lupus erythematosus?

Answer 77

1. **hydralazine** 2. **procainamide** 3. **isoniazid** 4. minocycline 5. quinidine will present with new onset lupus symptoms, ANA and anti-histone antibodies (NOT anti-dsDNA like in SLE)

Question 78

which 2 types of anti-diabetic medications promote weight loss?

Answer 78

1. GLP-1 agonists 2. SGLT-2 inhibitors

Question 79

for which 3 enzymes is tetrahydrobiopterin (BH4) an essential cofactor?

Answer 79

1. **phenylalanine hydroxylase**: converts phenylalanine to tyrosine 2. **tyrosine hydroxylase**: converts tyrosine to L-dopa 3. **tryptophan hydroxylase**: converts tryptophan to serotonin

Question 80

which 3 medications impair folate metabolism, and therefore are associated with neural tube defects?

Answer 80

1. valproate 2. methotrexate 3. trimethoprim-sulfamethoxazole (TMP-SMX)

Question 81

with what is subacute bacterial endocarditis (SBE) caused by *S. gallolyticus (S. bovis)* vs *S. viridans* associated?

Answer 81

*S. gallolyticus (S. bovis)*: normal flora of colon, bacteremia associated with **colon cancer**, also most cases of SBE occur in patients without pre-existing valvular abnormality *S. viridans*: SBE following **dental work**

Question 82

how do patients w/ restrictive vs obstructive lung disease compensate for the increased work of breathing?

Answer 82

restrictive —> rapid, shallow breathing (keep tidal volume low) obstructive —> slow, deep breathing (keep respiratory rate low)

Question 83

what are the 3 stages of acute tubular necrosis (ATN)?

Answer 83

may occur due to ischemia caused by hypotension (such as hemorrhage, for example) 1. **initiation** (24-36h): ischemic or toxic insult occurs 2. **maintenance** (1-2 weeks): tubular damage causes oliguria, fluid overload, electrolyte abnormalities, “muddy” casts 3. **recovery**: re-epithelialization of tubules, GFR recovers, transient polyuria and loss of electrolytes

Question 84

AD mutation in *TTN* gene encoding for titin protein =

Answer 84

**familial dilated cardiomyopathy** titin = sarcomere protein, anchors beta-myosin heavy chain to Z-discs [acquired causes = viral infection, alcohol, cocaine, infiltrative disease]

Question 85

name the cancers with the tumor marker: a. alpha-fetoprotein (2) b. beta-hCG (3) c. cancer antigen 125 (CA-125) d. estrogen e. lactate dehydrogenase

Answer 85

a. alpha-fetoprotein: hepatocellular carcinoma + ovarian germ cell tumors b. beta-hCG: hydatidiform mole, choriocarcinoma, dysgerminomas c. cancer antigen 125 (CA-125): epithelial ovarian cancer d. estrogen: granulosa cell tumors e. lactate dehydrogenase: dysgerminomas

Question 86

pt returning from South Africa w/ high fever, headache, severe myalgia, and joint pain =

Answer 86

**dengue** (*Flavivirus* infection): transmitted via *Aedes* mosquito, common in South America primary infection causes **breakbone fever**, secondary infection (w/ different viral serotype) causes **dengue shock syndrome** (hemorrhagic, stupor) [4 dengue virus serotypes, cross-reactive antibodies with repeat infection by different serotypes cause worse disease]

Question 87

crescent-shaped intracellular organism causing congenital triad of chorioretinitis + diffuse intracranial calcifications + hydrocephalus

Answer 87

congenital toxoplasmosis (*Toxoplasma gondii*)

Question 88

what is the order of mutation of the following genes in the adenoma-to-carcinoma sequence? K-RAS, APC, p53, DCC

Answer 88

**APC** tumor suppressor gene is typical first mutation followed by **K-RAS** + **DCC** (deleted in colon cancer) + **p53** [note K-RAS and DCC mutations are anti-apoptotic, and typically occur in larger adenomas]

Question 89

what is the treatment for scabies? (2)

Answer 89

1. **topical permethrin**: blocks voltage-gated Na+ channels 2. **oral ivermectin**: blocks Cl- channels, alternative medication or used in combination for crusted (sever) scabies

Question 90

what is topical mupirocin used to treat?

Answer 90

**impetigo** caused by Staph. aureus or Strep. pyogenes

Question 91

what is the clinical use of sevelamer in chronic kidney disease?

Answer 91

**sevelamer**: non-absorbable anion-exchange resin that binds intestinal phosphate to reduce absorption used if dietary phosphate restriction is not sufficient

Question 92

which 4 bacteria most commonly cause pulmonary exacerbations in patients with cystic fibrosis?

Answer 92

1. Staph. aureus 2. Pseudomonas aeruginosa 3. nontypeable Haemophilus influenzae 4. Burkholderia cepacia complex (Gram neg.)

Question 93

which classes of antibodies have hinge regions?

Answer 93

IgG, IgD, IgA hinge regions **increase avidity** by providing flexibility to reach multiple epitopes on an antigen [avidity proportional to number of Fab-antigen interactions]

Question 94

what is the most common CFTR gene mutation causing cystic fibrosis?

Answer 94

3-base pair deletion of **phenylalanine** at position 508 —> impaired **post-translational processing** transport protein is made, but targeted for proteosomal degradation instead of surface

Question 95

administration of which ion improves neuron survival in glutamate toxicity?

Answer 95

glutamate NMDA receptor is normally occupied by **magnesium** in resting state Mg2+ is displaced by either glutamate binding or loss of negative potential (in dying neuron, this can be caused by loss of ATP-dependent Na/K gradient) giving magnesium can block the NMDA channel, decreasing influx of Ca2+ and Na+ —> inhibited glutamate-mediated depolarization

Question 96

what is the primary anti-ischemic effect of nitrates?

Answer 96

VENOdilation —> decreased LV end-diastolic volume and wall stress, decreased myocardial oxygen demand

Question 97

what does histology of pancreatic islets show in Type 1 vs Type 2 diabetes?

Answer 97

Type 1: islet leukocytic infiltration (AUTOIMMUNE) Type 2: islet amyloid deposition

Question 98

contrast the MOA of zileuton vs montelukast

Answer 98

**zileuton**: 5-lipoxygenase enzyme inhibitor, reduces **production** of leukotrienes **montelukast**: leukotriene **receptor** antagonist

Question 99

which arteries are derived from each of the pharyngeal arches?

Answer 99

1. maxillary artery (CN V) 2. stapedial artery (CN VII) 3. **common carotid**, proximal internal carotid (CN IX) 4. true aortic arch, **subclavian arteries** (CN X - superior laryngeal) 5. obliterated 6. pulmonary arteries, ductus arteriosus (CN X - recurrent laryngeal)