Uworld: 5-25

Front 1

Osteogenesis imperfecta results in defect collagen type ____.

Back 1

1

Front 2

Substance A is freely filtered in the glomeruli and reabsorbed in the renal tubules. A healthy volunteer receiving substance A has the following findings:

Inulin clearance: 100 mL/min
PAH clearance: 500 mL/min
Plasma concentration of substance A: 0.5 mg/mL
Tubular reabsorption of substance A: 25 mg/min

What is the expected excretion rate for substance A in this volunteer?

Back 2

Total filtration rate of substance A = GFR x plasma concentration of A
GFR~Clearance of inulin (neither secreted nor reabsorbed)

Total filtration rate of substance A = (inulin clearance)(plasma concentration of substance A)

Net excretion rate of substance A= (inulin clearance)(plasma concentration of substance A) - (Tubular reabsorption of substance A)

=100x0.5 - 25 = 25 mg/min

Note that PAH clearance is irrelevant!

Front 3

What are potassium levels like in someone with DKA?

Why?

Back 3

Normal to increased serum potassium levels despite low intracellular potatssium.

Potassium loss occurs via osmotic diuresis induced by glycosuria.

Potassium replacement is a crucial step in management of pts with DKA.

Front 4

Draw a cardiac catheterization graph that shows mitral regurgitation.

Back 4

Front 5

Label

Back 5

A: Descending duodenum
B: Pancreas
C: IVC
D: Abdominal Aorta
E: Loop of jejunum

Front 6

Describe the mechanisms required for calcium influx and efflux of cardiac muscle cells.

Back 6

Influx: Voltage dependent calcium channels which then stimulate ryanodine receptors, which allow for release of a still larger pool of stored calcium within sarcoplasmic reticulum

Efflux: mediated by Ca2+-ATPase and Na+/Ca2+ exchange mechanisms

Front 7

Side effects of nitrates.

Back 7

HEADACHES
Cutaneous flushing

Most common at higher doses where nitrates can produce arteriolar dilation.

Front 8

What reaction does urease catalyze?

Back 8

Urea-->CO2 + Ammonia, causing a pH increase

Used to detect H. pylori infection

Front 9

How is vancomycin resistance achieved?

Back 9

Vancomycin binds D-alanyl-D-alanine termini in cell wall peptide precursors to prevent formation of peptidoglycan.

Mechanism of vancomycin resistance results from substitution of D-lactate for D-alanine in synthesis of proteoglycan precursors (altered vancomycin binding site)

Front 10

How is pseudomonas transmitted?

Back 10

Water!

HOT TUB FOLLICULITIS

Front 11

Women who have just delivered babies with neural tube defects are asked about their use of acetaminophen during the first three months of pregnancy.

Women who delivered healthy babies are also asked about their use of acetaminophen during the first three months of pregnancy.

What type of study is this?
What measure of association is most appropriate?

Back 11

Case-control study

People with dz of interest (cases) and people without the diseases (controls) are asked about previous exposure to variable being studied (acetaminophen use).

Main measure of assocn is exposure ODDS RATIO (odds of exposure of people with disease (cases))/(odds of exposure of people w/o the dz (controls))

Note: would only use relative risk if had incidence (which can't be measured in case-control studies bc people already have the dz!)

Front 12

How does anorexia result in amenorrhea?

Back 12

Loss of pulsatile secretion of GnRH from hypothalamus. Not due to defect in pituitary or ovaries.

This occurs when level of body fat falls below a certain critical level.

Front 13

Effects of carnitine deficiency.

Back 13

beta-oxidation of fatty acids requires removal of carbons from FA chain by oxidation at beta-carbon (occurs in mitochondria).

To transport fatty acyl-coA from cytosol into mitochondria, cell must first form fatty acyl-CARNITINE intermediate.

Reaction catalyzed by carnitine acyltransferase I on outer surface of inner mitochondrial membrane.

After molecule transported into mitcodhonria, carnitine acyltransferase II on inner surface of inner mitochondrial membrane catalyzes regeneration of fatty acyl-CoA and free carnitine.

KNOWN AS CARNITINE SHUTTLE.

Carnitine deficiency reduces ability of FA's to enter mitochondria for beta-oxidation.

Beta-oxidation of FA's produces acetyl CoA, a precursor of acetoacetate (a ketone!). Thus, carnitine deficiency causes dec'd formation of acetoacetate.

Front 14

Tumor cell expressing CD31:
Diagnosis
Exposure risks
Tumor type

Back 14

CD31 is PECAM1 (platelet endothelial cell adhesion molecule); functions in leukocyte migration through endothelium

Thus tumor arises from vascular endothelial cells. Most likely diagnosis is LIVER ANGIOSARCOMA (rare malignant vascular endothelial cell neoplasm)

Carcinogen exposure: arsenic, thorotrase (radioactive contrast medium), polyvinyl chloride (plastic widely used in industry)

Front 15

Papillary thyroid vs Follicular thyroid carcinomas:
Histologic differences

Back 15

Papillary: branchinc papillae, cuboidal epithelium, GROUND GLASS APPEARANCE, CONCENTRIC CALCIFIED STRUCTURES (psammoma bodies)

Follicular: consist of follicular cells or large cells with eosinophilic cytoplasm (Hurthle cells).

Front 16

Which biochemical processes occur exclusively in the mitochondria?

Back 16

beta-oxidation of FAs
TCA
Urea cycle (carbamoyl phosphate synthetase 1, ornithine transcarbamoylase)
Pyruvate carboxylation (pyruvate carboxylase)

Front 17

Which biochemical processes occur exclusively in the cytoplasm?

Back 17

All reaction of pentose pathway (transketolase)

Front 18

33 year-old female
Failure to conceive for 1 year
h/o purulent urethritis 5 years ago treated with ceftriaxone

Diagnosis
How could this have been prevented?

Back 18

Most common cause of tubal-factor infertility is PID--most commonly caused by Neisseria gonorrhoeae and Chlamydia trachomatis.

Need to treat for both! Not just ceftriaxone. Need to add azithromycin or doxycycline.

Since not treated correctly, chlamydia allowed to persist and cause asyx infection leading to fallopian tube scarring and subsequent infertility.

Front 19

A cohort study is conducted to assess association between smoking and SCC of esophagus. During 10 years of follow-up, smokers had five times the risk of esophageal carcinoma compared to non-smokers (RR=5.0, 95% CI = 2.9-7.1)

What percent of esophageal carcinoma can be attributed to smoking?

Back 19

Attributable risk percent = (risk in exposed - risk in unexposed)/risk in exposed

OR

ARP = (RR-1)/RR
=(5-1.0)/5.0=0.80

Front 20

Back 20

Filtration Fraction = fraction of plasma entering kidneys that filters into renal tubular lumen:
FF = GFR/RPF

RPF is amount of plasma that perfuses kidneys per unit time:
RPF = (1-HCT)(RBF)

Therefore:
FF = GFR/[(1-HCT)(RBF)]
=0.1/[(1-0.5)(1)]
=0.2

Front 21

8 year-old boy
1 week h/o fever, throat pain
Severe dyspnea, tachypnea, inspiratory stridor
Worsening dysphagia with solid foods
Labs reveal immature hematopoietic cells (blasts) in peripheral smear

Diagnosis
Pathophys of Syx

Back 21

Blast cells in periphery suggestive of leukemia.

Most common pediatric malignancy is ALL. Neoplastic cells of ALL cells arise from either pre-B or pre-T lineage.

T-cell ALL more likely to present with large anterior mediastinal mass that can compress great vessels, causing SVC syndrome. Mediastinal mass can also compress esophagus causing dysphagia, while compression of trachea leads to dyspnea, stridor.

Front 22

Effects of doxorubicin on heart function (specific).

Back 22

Cardiotoxicity leading to DILATED cardiomyopathy with SYSTOLIC DYSFN.

Front 23

What is alcoholic cardiomyopathy?

Back 23

LV dilation (CM)-->systolic dysfn

Front 24

Diagnosis
Pathophys
Presentation

Back 24

Oval focus of hyperdensity consistent with acute intraparenchymal hematoma.

Most commonly caused by HTN.
HTN iduces hyaline arteriosclerosis of arterioles, most commonly in basal ganglia. Vascular walls weaken, prone to dilation.

Expansion of arterioles form tiny CHARCOT-BOUCHARD PSEUDOANEURYSMS.

THese pseudoaneurysms may rupture and cause small amounts of bleeding or production of hematoma.

Presentation: sudden onset of focal deficits

Front 25

Cause of death?

Back 25

Ruptured LV free wall (complication of STEMI; generally occurs 3-7 days after onset of total ischemia, when coagulative necrosis, neutrophil infiltration, and enzymatic lysis of CT have weakened infarcted myocardium).

Free wall rupture causes cardiac tamponade-->limits diastolic filling-->venous return reduced

-->PROFOUND SYSTEMIC HYPOTENSION
-->pulseless electrical activity

Front 26

Osteoblasts vs Osteoclasts:
Serum markers

Back 26

Osteoblasts: alkaline phosphate

Osteoclasts: Tartrate-resistance acid phosphatase, urinary hydroxyproline, urinary deoxypyridinoline (urinary deoxypyridinoline is most reliable of the three)

Front 27

Symptoms of MEN syndromes.

Back 27

MEN1: parathyroid, pancreas, pituitary

MEN2A: medullary thyroid, pheo, parathyroid

MEN2B: medullary thyroid, pheo, mucosal neuromas

Note MEN2A/2B both have germ-line RET proto-oncogeneamll

Front 28

Diagnosis
What would these stain positively for?

Back 28

Auer rods-->AML M3

Auer rods indicate myeloid differentiation, they are deformed azurophilic granules and will stain positively for MYELOPEROXIDASE.

Front 29

Verapamil administration would have what effect?

Back 29

Phaso 0 depolarization (rapid upstroke following slow phase 4 depolarization) mediated by calcium ion influx into cells of the SA and AV nodes.

Verapamil is a CCB and will slow phage 0 depolarization, which decreases the rate of SA node firing and slows AV node conduction.

Impulse conduction from SA node through AV node to ventricular myocardium all occurs during diastole; thus, verapamil slows diastolic depolarization.

Front 30

65 year-old female
Progressive dyspnea and cardiomegaly
Occasional dysphagia

Enlargement of what heart structure accounts for her symptoms?

Back 30

Cardiovascular dysphagia can result from pressure on esophagus from dilated left atrium.

LA commonly enlarged in patients w/Mitral Stenosis and LV failure.

Front 31

What heart structures are most anterior/posterior?

Back 31

Most anterior: RV
Most posterior: LA

Front 32

Describe the steps by which chronic hypertension contributes to pulmonary hypertension.

Back 32

Chronic HTN-->LV diastolic dysfn

Dec'd LV diastolic compliance-->rise in LV fill pressure
-->Rise in LA pressure
-->Rise in Pulmonary venous pressure
-->Pulmonary venous congestion
-->Rise in hydrostatic pressures cause capillary leak and subsequent pulmonary edema
-->Alveolar collapse
-->Dec'd ventilation
-->REACTIVE VASOCONSTRICTION
-->Pulmonary arterial HTN
(-->Pulmonary arterial HTN-->increase in afterload-->RHF)

Front 33

Describe the events that occur once phospholipase C is activated.

Back 33

Phospholipase C takes phospholipids and converts them into IP3 and DAG

IP3 increases intracellular calcium which, along with DAG, activates Protein Kinase C

PKC then phosphorylates proteins to do its thang.

Front 34

What is the role of 16S rRNA in prokaryotic ribosomes?

Back 34

Prokaryotic 16 rRNA contains a sequence complementary to Shin-Dalgarno sequence on mRNA (located 10 bases upstream from AUG start codon)

This allows initiation of protein translation.

Front 35

Hypnotic drug with anxiolytic, muscle relaxant, and anticonvulsant actions

Drug class
Specific MOA

Back 35

Benzodiazepines
Modulate GABA-A receptor CHLORIDE channel in CNS, increasing its frequency of firing. This increase in Cl- permeability hyperpolarizes and stabilizes the membrane, rendering it less excitable.

Front 36

Diagnosis
Mode of Inheritance
Other symptoms

Back 36

Multiple small cutanoues lesions = Neurofibromas assocd w/NF1

Presents with:
Café-au-lait spots
Lisch nodules in iris (pigmented hamartomas; benign)
MENINGIOMAS

Front 37

Most common cause of pneumonia in ALL ADULTS.

Back 37

Step pneumo

Front 38

CSF shows:
Gram positive
Lancet shaped diplococci

Back 38

Strep pneumo

Front 39

CSF shows:
Gram positive
Cocci in clusters

Back 39

Staph aureus

Front 40

CSF shows:
Gram positive
Cocci in chains

Back 40

Strep agalactiae (Group B Strep)

Front 41

CSF shows:
Bean shaped diplococci

Back 41

Neisseria meningitidis

Front 42

Etoposide:
Specific MOA

Back 42

Specifically inhibit TOPOISOMERASE II's ability to seal strand breaks it induces, causing chromosomal breaks to accumulate and eventual cell death.

Used in testicular cancer and small cell lung cancer.

Front 43

Topoisomerase I vs II

Back 43

Topoisomerase I makes single-stranded nicks to relieve negative supercoiling

Topoisomerase II induces transient breaks in both DNA strands simultaneously to relieve both positive and negative supercoiling

Front 44

First-line treatment for patients with acute gouty arthritis

Back 44

NSAIDs--dec'd PG synthesis

Front 45

When are xanthine oxidase inhibitors and uricosuric drugs used in gout?

Back 45

to PREVENT future gouty arthritis attacks. not for use in acute gouty arthritis

Front 46

Hypoxemia
Petechial rash
Acute neurologic abnormalities
Long bone fracture

Back 46

Fat embolism syndrome

Front 47

Which cell cannot utilize ketones for energy? Why?

Back 47

RBCs--don't have mitochondria

Hepatocytes--don't have succinyl CoA-acetoacetate CoA transferase (thiophorase), which is required to convert acetoacetate to acetoacetyl CoA

Front 48

What is MCHC?
Diagnostic utility?

Back 48

MCHC = mean corpuscular hemoglobin concentration

In hereditary spherocytosis, MCHC is inc'd because of mild dehydration of the RBC

Front 49

3 year-old male
Jaundice, pallor
Anemia, reticulocytosis, increased indirect bilirubin
RBCs are dysmorphic without central pallor

Diagnosis

Back 49

Hereditary spherocytosis

Diagnosis is best confirmed by osmotic fragility testing

Front 50

45 year-old female
h/o pruritis, fatigue
Pale stool
Liver biopsy reveals granulomatous destruction of interlobular bile ducts

Diagnosis
Pathophys

Back 50

Primary biliary cirrhosis--autoimmune destruction of intrahepatic bile ducts and cholestasis

May also present with steatorrhea, portal HTN, osteopenia

Will see heavy portal tract infiltrate of macs, lymphocytes, plasma cells, and eosinophils

Front 51

Vertical diplopia:
When is it triggered?
Cause?

Back 51

When reading (eyes look toward nose) or walking downstairs

Trochlear Nerve Palsy (CN IV)

Front 52

CN innervations of the extraocular muscles.

Back 52

LR: CN6
SO: CN4
R: CN3

Front 53

30 year-old male
Neck lump
PMH pheochromocytoma
FMH of thyroid cancer

Diagnosis
Histologic Findings
Gene mutation involved

Back 53

Patient likely has MEN 2A/B syndrome

Expect medullary thyroid cancer (mutation to RET proto-oncogene); arises from parafollicular calcitonin-secreting C cells

Histology shows uniform polygonal or spindle-shaped cells w/extracellular amyloid deposits. Amyloid stains with Congo red.

Front 54

What step of the TCA provides a phosphate source for energy?

Back 54

GTP production occurs in SuccinylCoA-->Succinate

Energy sed to convert phosphoenolpyruvate to phosphoenolpyruvate carboxykinase

Front 55

Laparotomy reveals chalky white lesions in mesentery.

Histology reveals fat cell destruction and calcium deposition.

Diagnosis
Pathophys

Back 55

Acute pancreatitis:
Starts as acute interstitial pancreatitis (duct obstruction-->stasis-->digestions of adipose cells by lipase)
Areas of focal necrosis and calcium precipitation induce an inflammatory rxn

If inflammatory process continues, blood flow to pancreas is compromised as a result of edema and ischemia damages the acinar cells-->RELEASES TRYPSIN

Trypsin activates other proteolytic enzymes and initiates autodigestion of pancreatic tissue

Acute necrotic pancreatitis develops

Destruction of blood vessel walls can cause hemorrhage into necrotic areas.

Front 56

Neuroendocrine markers of small cell carcinoma.

Back 56

Chromogranin
Synaptophysin
Neurofilaments

Front 57

High Potency vs Low Potency Antipsychotics:
Examples
AE Differences

Back 57

High potency:
Haloperidol, fluphenazine, pimozide

Low potency: Chlorpromazine, thioridazine

High potency agents more likely to cause EPS and less likely to cause anticholinergic/antihistamine f/x

Low potency agents more likely to cause antichol/antihistamine side effects