Week of March 23

Question 1

What are the derivatives of the pharyngeal pouches

Answer 1

1: epithelium of middle ear and auditory tube
2: epithelium of palatine tonsil crypts
3: thymus, inferior parathyroid glands. Myasthenia graivs is associated with thymoma and thymic hyperplasia
4: superior parathyroid glands, ultimobranchila body

756

Question 2

What is the organism associated with hyponatremia

Answer 2

Legionella pneumonia. Gram-negative bacillus.

• Associated with recent exposure to contaminated water (cruise ships, spa, hospitals, air-conditioned hotels).
• Radiographic evidence of PN (patchy infiltrates that may progress to consolidation), high fever, bradycardia relative to high fever, HA and confusion, watery diarrhea.
• Lab: hyponatremia and suputum gram stain shows many neutrophils but few or no organism. Often diagnosed by urinary antigen testing; grows on selective medium (buffered charcoal yeast extract) 8257

Question 3

Describe the presentation of a patient with SCID

Answer 3

Present with recurrent infections caused by bacteria, viruses, fungi, and opportunistic pathogens as well as failure to thrive and chronic diarrhea within the 1st year of life. Hypoplasia of both B- and T-lymphcoyte tissues. Lab shows lymphopenia and hypogammaglobulinemia. 2078

Question 4

The candida skin test gauges what cell activity?

Answer 4

Guages the activity of the cell-mediated immune response. The active cells in cell-mediated response are macrophages, CD4 and CD8 T lymphocytes and NK cells. Failure to generate a response to this test is called anergy, which would be expected in SCID, where there is hypoplasia of both B and T cell lines. 2079

Question 5

A skull fracture in area of junction of frontal, parietal, temporal, and sphenoid bones causes damage to what artery?

Answer 5

Middle meningeal artery is a branch of the maxillary artery (which itself is a branch of external carotid) that enters the skull at the foramen spinosum and courses intracranially deep to the pterion. Can lead to epidural hematoma that can expand rapidly leading to transtentorial herniation adn palsy of oculmotor nerve. 1813

Question 6

64 y/o with persistent back pain, constipation and easy fatigability. Renal biopsy shows atrophic tubules, many large obstructing eosinophilic casts. Diagnosis?

Answer 6

Consider multiple myeloma in elderly patient with

• Easy fatigability (due to anemia)
• Constipation (Due to hypercalcemia)
• Bone pain, most commonly in back and ribs (due to production of osteoclast activating factor by myeloma cells and subsequent bone lysis)
• Renal failure
• Bence Jones protein (light chains) which precipitate with Tamm Horsfall protein and form eosinophil casts (NOT eosinophilic cell casts) that compress the tubular epithelium and cause atrophy 1054

Question 7

How do you calculate resistance in series vs. parallel

Answer 7

Total body circulation can be descirbed as a parallel circuit, whereas circulation in an indiviudal organ is often best described by a series arrangement.

Parallel: 1/RT = 1/R1 + 1/R2 ….

Series: RT = Rartery + Rarteriole + Rcapillary + Rvenule + Rvein

1616

Question 8

Fever, HA, photophobia, and painful extraocular movements with isolation of viral RNA from CSF are classic symptoms of what?

Answer 8

Aseptic menigitis. Enterovirus infection is the most common cause of aseptic meningitis; family of ssRNA viruses that include coxsackievirus, echovirus, poliovirus. Fecal-oral transmission.

1906

Question 9

What is the Kozak sequence and its relationship to Thalassemia Intermedia?

Answer 9

Kozak sequence plays a role in the initiation of translation (i.e. mRNA binding to ribosomes). A mutation three bases upstream from the start codon (AUG) in this sequence is associated with thalassemia intermedia –> hypochromic, microcytic anemia 2086

Question 10

What is the purpose of blinding in a research study

Answer 10

To prevent patient or reasearcher expectancy from interfering with the determination of an outcome (i.e. observer bias)

Question 11

Why would creating an anti-gonoccoccal vaccine against the pilus fail?

Answer 11

The gonococci use their pili to mediate adherence to the mucosal epithelium. An antibody against the specific pilus protein expressed by a gonococcus would prevent mucosal adherence and initiation of infection, but each gonoccocus posses the ability to modify the pilus protein that it expressed via **antigenic variation **1025

Question 12

MOA of Turbinafine, Capsofungin, Flucytosine

Answer 12

Terbinafine: inhibits synthesis of ergosterol of the fungal membrane by inhibiting squalene epoxidase

Capsofungin: blocks synthesis of B(1,3)-D-glucan (component of Candida and Aspergillus cell walls)

Flucytosine: transformed into 5-FU in fungal cell; inhibits fungal protein synthesis by replacing uracil with 5-FU in fungal mRNA. Used for systemic fungal infections. 836

Question 13

What is pantothenic acid necessary for?

Answer 13

The biologically active form of pantothenic acid is coenzyme A, which binds with oxaloacetate in the first step of the TCA cycle to form citrate and then succinyl-CoA. 1044

Question 14

What is the effect of prolonged exposure to loud noises?

Answer 14

Prolonged exposure to loud noises causes hearing loss d/t damage to stereociliated hair cells of organ of Corti. 1633

Question 15

What is the MOA of the ONLY drug that is used in hypertensive emergenices that can causes arteriolar dilation and also increases renal perfusion/promotes natriuresis?

Answer 15

Fenoldopam: selective dopamine-1 receptor agonist (activates AC –> increaed cAMP –> vasodilation). It causes arteriolar dilation and natriuresis leading to decreased systemic vascular resistance and BP reduction. 689

Question 16

What does incidence correspond to

Answer 16

The number of new cases of a disease in a certain population at risk over a given time period

Question 17

Describe the renal handeling of plasma glucose

Answer 17

Complete reabosprtion of low filterd loads at low plasma concentrations. Increasing fractional excretion of glucose is observed at higher plasma concentrations. 2010

Question 18

Where is H. pylori found?

Answer 18

Can only colonize areas of gastric metaplasia. Colonization of the gastric antrum is associated with increased gastric acid secretion, and teh duodenal bulb is the area most exposed to this increase in acid production –> dudoenal ulcers. Thus, found in greatest concentration in the **prepyloric area of the gastric antrum. **7710

Question 19

What is the most important risk factor for developing initimal tears leading to aortic dissection?

Answer 19

HTN is the single most important risk factor. HTN, smoking, DM, and hypercholesterolemia are all major risk factors for atherosclerosis, which predisposes more to aortic aneurysm formation than aortic dissection. 473

Question 20

What is damaged in a child that presents with injured arm held close to body with elbow extended (or slightly flexed) and forearm protonated?

Answer 20

Annular ligament displacement: MC elbow injury in children. Radial head subluxation (nursemaid’s elbow) results from sudden traction on the outstretched and pronated arm of a child. Affected children are usually in little distress unless attems are made to move elbow. 8579

Question 21

When can physicans provide emergency treatment to incapacited patients without obtaining consent

Answer 21

In abscence of an advance directive, designated health care proxy, or family member.

Question 22

What is it called when there is exchange of genetic information between two virus strains that have non-fragmented, double-stranded DNA genomes?

Answer 22

Recombination: exchange of genes between two chromosomes via crossing over within homologous regions. The resulting progeny will have traits not present simulatensouly in either parent virus. 1461

Question 23

What is the MCC of an elevated maternal serum AFP

Answer 23

Dating error (i.e. underestimation of the gestational age), which can be confirmed by fetal USG. AFP is synthesized by the fetal liver, GI tract, and yolk sac (early gestation only). Increased AFP is also associated with NTDs, anterior abdominal wall defects (omphalocele, gastroschisis), and multiple gestation. Down Syndrome is associated with decreased AFP. 342

Question 24

What type of damage results in nasal hemianopia

Answer 24

Aneurysm or atherosclerotic calcification of the internal carotid artery can laterally impinge on the optic chiasm producing nasal hemianopia by damaging uncrossed optic nerve fibers from the temporal portion of the ipsilateral retina.

8636

Question 25

What are the local cutaenous AEs of chronic topical corticosteroid administration?

Answer 25

Atrophy/thinning of the dermis that is associated with loss of dermal collagen, drying, cracking, and/or tightening of the skin, telangiectasias, and ecchymoses. 1214

Question 26

Describe the relationship betwen blood flow, resistance and vessel radius

Answer 26

Blood flow is directly proportional to the vssel raidus raised to the fourth power. Resistance ot blood flow is inversely proprtional to the vessel radius raised to the fourth power. 1621

Question 27

It is most important for a test to be used in all newborns to have a high….

Answer 27

Sensitivity: ability to correctly identify those with the disease. Most patietns with the disease will have a positive test result on a test with high sensitivity. Given a test with high sensitivity, a negative result would help to rule out a diagnosis (SnNout) 1300

Question 28

Arterial PaCO2 is a direct indicator of what?

Answer 28

Alveolar ventilation status. Hypocapnia implies ongoing alveolar hyperventilation; can result from V/Q mismatch that causes ddecreased O2 and CO2 exchange (e.g. PN or PE) –> resultant hypoxemia stimulates peripheral chemoreceptors and increases respiratory drive above noraml levels.

Upper airway obsturction, reduced ventilatory drive, respiratory muscle fatigue, and decreased chest wlal compliance are possible causes of alveolar hypoventilation and hypercapnia. 528

Question 29

Describe PAH in kidneys

Answer 29

PAH is freely filtered from the blood in the glomerular capillaries to the tubular fluid in Bowman’s space. It is also secreted from teh blood into the tubular fluid by the cells of the proximal tubule by a carrier protein-mediated process. The secretion of PAH can be satured at high blood concentrations. 1619

Question 30

What does the SM contain enzymes for?

Answer 30

Seroid and phospholipid biosynthesis. All steroid-producing cells (e.g. cells in the adrenals, gonads, and liver) contain a well-developed smooth ER.

Example: ACTH primarily stimulates the cells of adrenal cortex to produce glucocorticoids, but it also increases adrenal production of mineralocorticoids. These are all cholesterol-derived steroid hormones, and the cells that synthesize them contain promoninent SERs. 2016

Question 31

Why does lactic acidosis result in an increased anion gap?

Answer 31

Occurs in patients with septic shock becuase of tissue hypoxia, which result in impaired oxidative phosphorylation and the shunting of pyruvate to lactate following glycolysis. Hepatic hypoperfusion also contributes to the buildup of lactic acid, as the liver is the primary site of lactate clearence. 2101

Question 32

dsDNA fragments in neuron bodies of sacral sensory ganglia are strongly associated with what?

Answer 32

Recurring painful genital rash!

Viruses known to invade the dorsla root sensory ganglia include HSV-1/2 and VZV. Among these, HSV-2 produces a recurrent, painful genital rash when teh latent virus is reactivated in the sacral sensory ganliga. HSV-1 commonly infects sensory ganglia-innervating dermatomes above waist (e.g. trigeminal ganglia) 1549

Question 33

What are the lab values in patients with osteoporosis

Answer 33

Have low bone mass, resulting in increased susceptibility for fragility fractures. In primary osteoporosis, serum calcium, phosphorus, and PTH are typically normal. 982

Question 34

What type of anti-inflammatory drug would not have SE of bleeding and gastrointestinal ulceration

Answer 34

Selective COX-2 inhibitors (e.g. celecoxib), which do not impair platelet function becuase platelets predominatly express COX-1

715

Question 35

How do you treat a patient who has overdosed on a BB?

Answer 35

Glucagon, which increases HR and contracility independent of adrenergic receptors. Activates GPCRs on cardiac myoctes, causing activation of adenylate cyclase and raising intracellular cAMP –> calclium release from intracellular stores, increased SA node firing, HR and cardiac contracility. 1444

Question 36

Descirbe the effects of alpha vs. beta receptors

Answer 36

Alpha 1: targets peripheral vasculature (increase SBP), bladder (contraction of internal urethral sphincter), and eye (mydriasis). Drugs - Epi, NE, phenylephrine, methoxamine

Beta 1: targets heart (increase HR, contractility, conductance). Drugs - epi, DA, dobutamine, isoproterenol

Beta 2: targets peripheral vasculature (vasodilation, decrase DBP), bronchi (bronchodilation), uterus (relaxation/tocolysis). Drugs - isoproterenol, terbutaline, ritodrine.

1368

Question 37

What is “Garderner’s Mydriasis”

Answer 37

D/t toxins that possess strong anticholinergic properties. Mnemonic for clinical manifestations of atropine poisoning: “blind as a bat, mad as a hatter, red as a beet, hot as a hare, dry as a bone, the bowel and bladder lose their tone, and the heart runs alone.” Atropine is a reversible cholinergic antagonist that acts selectively on muscarinic recptors. It can be reversed by cholinesterase inhibitors (physostigmine) 1321

Question 38

What is the underlying biochemical feature of megaloblastosis?

Answer 38

Megaloblastic anemia: low hemoglobin, elevated MCV; alcoholics stems from folic acid deficiency

Defect in DNA synthesis. Folic acid is a single carbon donor required for the synthesis of purine and pyramidine base. RNA and protein synthesis may continue relatively unaltered, leading to a state of unbalanced cytoplasmic growth and impaired cell division. 1580

Question 39

What is the pathogenesis of alcohol-induced hepatic steatosis?

Answer 39

Alteration of hepatic NAD/NADH ratio in alcoholics induces fatty liver through inhibition of gluconeogenesis and fatty acid oxidation. 370

Question 40

What substance is added to stored blood that can result in hypocalcemia?

Answer 40

Citrate anticoagulant: chelates calcium and magnesium and may reduce thier plasma levels, causing parasthesias

Question 41

Describe the histological apperance of the adrenal gland divisions

Answer 41

• zona glomerulosa: cells arranged in rounded/arched clusters
• zona fasiculata: foamy-appearing cells in columns
• zona reticularis: basophilic cells in anastomosing cords
• medulla: sharply demarcated from cortex and composed of chromaffin cells with deeply basophilic cytopaslm. Chromaffin cells are modified postganglionic sympathetic neurons; stimulated by ACh released by symp preganglionic neurons and secrete catecholamines 8424

Question 42

What is the presentation of fibromyalgia?

Answer 42

Presents in 20-50 y/o F with diffuse MS pain, insomonia and emotional distrubances. Presence of multiple symmetrically distributed tender spots over the patients muscles, joints and tendons such as over the spine of teh scapula, the lateral epicondyle and the medial fat pad of knee. 867

Question 43

Describe differences in tracheal deviation

Answer 43

Trachea deviates toward opacified lung with lung volume loss (atelectasis; an obstructive lesion in a mainstem bronchus can prevent ventilation of an entire lung, leading to lung collapse) and away from opacified lung with large **pleural effusion. **2116

Question 44

Blunt trauma to lateral aspect of leg, fibular neck fracturs, and external pressure due to prolonged immobility (e.g. hospitalization, surgery, or casting) can injure what nerve?

Answer 44

Common peroneal nerve: begins in proximal popliteal fossa, where sciatic nerve divides into tibial and common peroneal nerve. Injury results in “fott drop” and characteristic “steppage gait.” 1742

Question 45

What is an ecological study ?

Answer 45

Frequency of a given characteristic and a given outcome are studied using population data. Useful to generate hypothesis but should not be used to make conclusions regarding indivudals within these populations (ecological fallacy). 10570

Question 46

How can non-capsule forming strains of Strep pneumoniae acquire genes that code for capsule and thus gain virulence?

Answer 46

By undergoing transformation, which allows the bacterium to take up exogenous DNA fragments and express the encoded proteins.

Conjugation (one-way tx of DNA between bacterial cells through direct physical contact; donor contains F factor that codes for sex pilus) and transduction (bacteriophage) are 2 additional mechanisms by which bacteria can obtain new genetic material. 736

Question 47

Describe local vs. systemic defense against Candida

Answer 47

Local defense is performed by T-cells, whereas systemic infection is prevented by neutrophils. For this reason, localized candidiasis is common in HIV-positive patietns, while neutropenic indiviudals are more likely to have systemic disease. 112

Question 48

Flattening of the deltoid muscle after a shoulder injury suggests what?

Answer 48

Anterior dislocation of humerus This injury most commonly results from forceful external rotation and abduction at the shoulder joint. Axillary nerve injury, resulting in deltoid paralysis and loss of sensation over lateral arm, is often associated. 1924

Question 49

Autopsy shows hyperinfated lungs, airway mucus plugging, and cellular infiltration of the bronchial wall. Which drug could have prevented the cellular rxn in patients airways?

Answer 49

Inhaled glucocorticoids are the most effective anti-inflamamtory agents for chronic preventative treatment of bronchial asthma. 169

Question 50

What is the most dangerous AE of amphotericin B

Answer 50

Nephrotoxicity –> anemia and electolyte abnormalities including hypokalemia and hypomagnesemia due to an increase in membrane permeability of distal tubule. 275

Question 51

Which types of drugs will slow K+ efflux from ventricular myocyte, prolong repolarization and prolong the refractory period

Answer 51

Class III antiarrhythmics such as amiodarone, sotalol, ibutilide and dofetilide. 901

Question 52

What do Southern, Western, Northern and Southwestern blot procedures analyze

Answer 52

Southern = DNA; Western = Proteins; Northern = mRNA; Southwestern = DNA-bound proteins.

Best method for determining whether a gene is being expressed is to analyze teh presence of its mRNA using a Northern blot.

Question 53

What is the defect in Enhlers-Danlos

Answer 53

Associated with abnormal collagen formation. Manifests clincally as over-flexible (hypermobile) joints, over-elastic (hyperelastic) skin, and fragile tissue susceptible to bruising, wounding, and hemarthrosis. 1244

Question 54

How does Crohn’s ileocolitis contribute to gallstones?

Answer 54

When the mucosa of the terminal ileum is inflamed (as in Crohn’s disease), bile acids are not reabosrbed, becoming lost with feces. As a result, a lesser amount of bile acid is present in bile, and the ratio of cholesterol/bile acids increases. Cholesterol precipitates in bile of the gallbladder and forms gallstones. 412

Question 55

What are the most common cancers (aside from skin cancer) in women in order of incidence and mortality

Answer 55

Incidence: breast > lung > colon

Mortality: lung > breast > colon

Question 56

How can you distinguish Hartnup

Answer 56

Result in niacin deficeincy d/t excess loss of dietary tryptophan, resulting from defective intestinal and renal tubular absorption of that amino acid.

Treatment: nicotinic acid or nicotinamide (niacin/vitain B3) and a high protein diet

Main lab finding in Hartnup is aminoaciduria, RESTRICTED to the neutral amino acids. The urinary excretion of proline, hydroxyproline, and arginine remains unchanged (differentiates from other causes of generalized aminoaciduria such as Fanconi). 1334

Question 57

What is a cutaneous necrotic disease that has a strong association with *Pseudomonas aeruginosa *bacteremia and septicemia?

Answer 57

Ecthyma gangrenosum. Occurs after P. aeruginosa invades perivascularly and releases tissue destructive exotoxins that cause vascular destruction and resultant insufficiency of blood flow to patches of skin which become edematous and subsequently necrose.

Pseudomonas infections are common in neutropenic patients, hospitalized patients, pts with burns and chronic indewlling caths. 973

Question 58

What is directly responsible for the wheal observed after an insect sting?

Answer 58

Results from an allergic, or Type I HSR. The allergens present in the insect venom result in antibody class switching to IgE on inital exposure, and subsequent exposure results in degranulation of mast cells and basophils with release of histamine and heparin –> increase local vascular permeability (wheal), but can also cause systemic vasodilation, bronchoconstriction and inflammation leading to anaphylactic shock. 556

Question 59

Where are parietal cells located and what results from their destruction?

Answer 59

Parietal cells are oxyntic (pale pink), round, plate-like cells found in the upper glandular layer that secrete gastric acid and IF. Because IF is required for absorption of B12 in the ileum, its abscence leads to B12 deficiency.

Pernicious anemia is d/t antibody-mediated destruction of parietal cells in gastric body and fundus –> chronic atrophic gastritis, which is characterized by loss of parietal cells with marked lymphocytic and plasma cell infiltration. 124

Question 60

Describe the aireway pressure-volume curve and describe what is located at the center

Answer 60

D/t elasticity of lungs, the alveolar transmural pressure is always positive, resulting in a collapsing force on lungs. Inversely, the chest wall tends to transmit an expanding force on the lungs, resulting in a negative transmural prssure across the chest wall most of the time, except during maximal inspiration. At the FRC, the airway pressure is zero and there is no tendency for air to flow either into or out of the lungs (i.e. the tendencies of the chest wall to expand and the lung to collapse oppose one another, creating a negative intrapleural pressure of -5 cm H₂0)

1519

Question 61

Describe how nitrites cause posioning via methemoglobinemia

Answer 61

Nitrites cause posioning by oxidizing the heme iron to the ferric state –> methemoglobin which is unable to bind oxygen and there is also a leftward shift of oxygen dissociation curve. Methemoglobin cannot bind to oxygen and therefore the oxygen content and oxygen carrying capacity of arterial blood will decrease. The bound fraction of oxygen and oxygen delivery to peripheral tissues will also decrease because of the inability of methemoglobin to carry and deliver O2.

Methemoglobinemia causes a dusky discoloration to the skin (simmilar to cyanosis), and because methemoglobin is unable to carry O2, a state of functional anemia is induced. The blood partial pressure of O2, however, will be unchanged because oxygen’s partial pressure is a measure of O2 dissolved in plasma and not related to hemoglobin function. 1416

Question 62

Describe the Gq pathway

Answer 62

Hormone binds to GPCR that activates PLC, causing degradation of membrane lipids into DAG and IP3. Protein kinase C is activated by DAG as well as calcium released from the sarcoplasmic reticulum under the influence of IP3.

Question 63

Describe twinning

Answer 63

Dizygotic twins results from fertilization of 2 oocytes by 2 different sperm and always have 2 amnions and 2 chorions.

In contrast, monozygotic twins arise from fertilization fo a single oocyte. Monozygotic twinning may occur at different stages of embryogenesis, which affect the organization fo fetal membranes: dichorionic/diamnionic (days 0-4), monochorionic diamniotic (day 4-8), monochorionic monoamniotic (days 8-12), and monochorionic monoamniotic conjoined twins (>13 days). 8406

Question 64

What is genomic imprinting?

Answer 64

Offisprings genes are expressed in a parent-specific manner. Genomic imprinting is produced by DNA methylation (carried out by DNA methyltransferases), which is an epigenetic process in which genes can be silenced by the attachment of methyl groups (such as S-adenosyl-methionine) to cytosine residues in the DNA molecule. 7791

Question 65

When can parent’s authority to make medical decisions for their children be challenged?

Answer 65

In cases in which a child is at signficant risk of harm. Physicians are justified in obtaining a court injunction to proceed with life-saving medical treatment of the child. 10533

Question 66

8 y/o presents with fever, abdominal pain and diarrhea. Reports patient’s puppy had diarrhea one week ago. Whats the cause?

Answer 66

Camylobacter infection (curved Gram negative rod with a filametn that allos it to move in a characteristic “corkscrew”) is a common cause of inflammatory gastroenteritis (fecal-oral route) and can be acquired from domestic animals (cattle, chicken, dogs) or from contaminated food. The diarrhea is inflammatory (initally watery, later bloody) and is acompanied by fever, abdominal pain (possibily mimicing appendicitis), tenesmus and leukocytes in stool. Infection is associated with Guillain-Barre syndrome. 1422

Question 67

Whats the characteristic histolgy of Pulmonary HTN and how do you treat this disorder?

Answer 67

Morphologic findings in branches of pulmonary artery, including increased arteriolar smooth musle thickness (medial hypertrophy), intimal fibrosis, and signficant luminal narrowing. In setting of severe HTN, lesions can progress to form interlacing tufts of small vascular chanells (plexiform lesions). Presents as a 20-40 y/o F with dyspnea and excercise intolerance.

Bosentan is an endothelin-receptor antagonist that blocks the effects of endothelin (potent vasoconstrictor that also stimulates endothelial proliferation). Therapy decreases pulmonary arterial pressure and lessens the progression of vascular and RVH. 903

Question 68

Describe the PK properties of thipental during induction of anesthesia

Answer 68

Short-acting barbiturate. After equilibration with the brain it rapidly redistributes into skeletal muscle and adipose tissue, which results in rapid recovery from anesthesia. 852

Question 69

What is the histological apperance of meningiomas?

Answer 69

Slowly growing, well circumscribed and benign tumors. Psammoma bodies are characteristic; composed of core of dense calcification with surrounding collagen-fiber bundles. 1151

Question 70

Maldevelopment of what leads to DiGeorge Syndrome?

Answer 70

T-lymphocyte immunodeficeincy that results form maldevelopment of the 3rd and 4th branchial (pharyngeal) pouches due to deletion on chromosome 22. 543

Question 71

What are the features of glucagonoma

Answer 71

Presentation: tumor arising from alpha-cells of pancreatic islets.

• Necrolytic migratory eryhtema: elevated painful and pruritc rash typically affecting face, groin, and extremities. Lesions enlarge and coalesce, leaving a bronze-colored central indurated area with peripheral blistering and scaling.
• Diabetes mellitus (hyperglycemia)
• GI Sx (diarhea, anorexia, abdominal pain)
• Normocytic normochromic anemia

Diagnosis: markedly elevated glucagon levels. 585

Question 72

How do thyroid hormones alter gene expression

Answer 72

By binding to nuclear receptors, which control gene expression by binding to DNA at hormone-responsive elements in the promoter region of target genes. Other molecules that act through nuclear receptors include retinoids, peroxisomal proliferating activated receptors, and fatty acids.

Receptors for several steroid hormones such as glucocorticoids, mineralocorticoids, androgens, and estrogens are usually initially present in cytoplasm, although they do migrate to nucleus once activated.

Question 73

What is effect modification and how does it differ from confounding?

Answer 73

Effect modification is present when the effect of the main exposure on the outcome is modified by the presence of another variable. Example: smoking status modified the effect of a new estrogen receptor agonist (exposure) on DVT incidence (outcome). It is NOT a bias.

Stratified analysis (analyzing the cohort as different subgroups) can help distinguish from confounding. With effect modification, the different strata will have different measures of association vs. confouding where teh stratifiation usually reveals no significant difference between strata. 1279

Question 74

Where does the serous fluid accumulate with testicular hydrocele?

Answer 74

Accumulates within the tunica vaginalis, which is embryologically derived from the peritoneum. When it remains in communication with the peritoneum, a communicating hydrocele results. 1827

Question 75

What cell types are predominant in Sarcoidosis

Answer 75

Accumulation of activated macrophages and formation of noncaseating granulomas. CXR will show bilateral hilar adenopathy. Sarcoid granulomas produce ACE and vitamin D, so patients often have elevated ACE levels and hypercalcemia.

CD4+ T helper cells are the predominant type of lymphocyte found in sarcoid granulomas. 796

Question 76

What does the diagnosis of SCZ require?

Answer 76

Requires 2 of the following 5 symptoms: delusions, hallucinations, disorganized speech, grossly disorganized behavior, and negative Sx. One of these must be delusions, hallucinations, or disorganized speech. The total illness duration must be at least 6m with at least 1m of active Sx. 2045

Question 77

What drugs are first-line for treatment of isolated systolic hypertension

Answer 77

Thiazide diuretics and dihydropyridine calcium channel antagonists (e.g. amlodipine; can lead to flushing and peripheral edema)are first-line drugs to treat in nondiabetic patients (where an ACE-I or ARB would be utilized first). 154

Question 78

What is an important property of carrier-mediated diffusion (facilitated diffusion)

Answer 78

Saturation: there is a finite number of carrier proteins in the cell membrane, and these carrier proteins require a discrete amount of time to pass a single molecule or ion through the membrane. Once all the carrier molecules are bound by substrate, no further diffusion can occur until a carrier protein is vacated (transport maximum or Tm). 1378

Question 79

What drug is capable of crossing the BBB and reversing both the CNS and peripheral Sx of severe atropine toxicity

Answer 79

The tertiary amine physostigmine! NOTE that the anticholinesterase agents neostigmine and edrophonium have a quaternary ammonium structure that limits CNS penetration.

Question 80

What is the main pulmonary effect of increased vagus nerve efferent activity?

Answer 80

Bronchoconstriction and increased bronchial mucus secretion (via ACh cting on M3 receptors). These effects increase airway resistance and the work of breathing. Anticholinergic agents such as tiotropium and ipratropium work to counteract these effects and are useful in treating obstructive lung diseases such as asthma and COPD.

Question 81

What enzymes are inactivated by lead?

Answer 81

The zinc-containing aminolevulinate dehydratase and ferrochelatase are enzymes in the heme biosynthetic pathway that are inactivated by lead. 1454

Question 82

What is the effect of chronic renal hypoperfusion

Answer 82

Significant renal artery stenosis causes renal hypoperfusion and activation of the RAAS. Modified smooth muscle (JG) cells of the affernt glomerular arterioles synthesize renin. Chronic renal hypoperfusion will cause hypertrophy and hyperplasia of the JG cells. 7569

Question 83

What is a complication of IBD that is seen much more often in UC than in Crohn’s disease?

Answer 83

Toxic megacolon: abd pain and distention, fever, diarrhea, adn signs of shock (decreasing BP, increasing HR). Complete cessation of neuromuscular activity in the intestinal wall is the first step in the pathogenesis of toxic megacolon. Plain abdominal X-ray should be used for diagnosis. Barium contrast studies and colonoscopy are CI d/t risk of perforation. 410

Question 84

Describe the formation of annular pancreas

Answer 84

Pancreas forms from the dorsal (tail, body, and most of head) and ventral (portion of head, uncinate process, and main pancreatic duct) buds, which are foregut invaginations that fuse.

Abnormal migration of the ventral pancreatic bud leads to formation of an annular pancreas, which encircles the descending part of duodenum and may lead to Sx of duodenal obstruction (recurrent bilious vomiting) soon after birth. 438

Question 85

What is the cause of isolated systolic HTN

Answer 85

Caused by age-related decrease in the compliance of the aorta and its proximal major braches.

Question 86

Which enzyme has 5’ to 3’ exonuclease activity?

Answer 86

DNA polymerase I has 5’ to 3’ exonuclease activity in addition to its 5’ to 3’ polymerase and 3’ to 5’ exonuclease activities. This 5’ to 3’ exonuclease activity is used to remove the RNA primer (which initiates DNA polymerization) and to remove damaged DNA. 1434

Question 87

Wilson’s disease causes cystic degeneration of what?

Answer 87

Cystic degeneration of the putamen as well as damage to other basal ganglia structures. The putamen is located medial to the insula and lateral to the globus pallidus on coronal sections. 1689

Question 88

How do triptans (e.g. sumatriptan) work?

Answer 88

5-HT 1B/1D agonists that directly counter the pathophysiologic mechanism of migraine HA by inhibiting the rlease of vasoactive peptides, promoting vasoconstrction and blocking pain pathways in the brainstem. BBs, antidepressants (e.g. amitriptyline and venlafaxine), and anticonvulsants (e.g. valproate and topiramate) are used for prophylaxis. 8476

Question 89

How can you treat nitroprusside toxicity

Answer 89

Nitroprusside is initially metabolized to cyanide, with subsequent conversion to thiocyanate by liver rhodanase. Thus, one major disadvantage of its use involves the risk for developing cyanide toxicity. Sodium thiosulfate is used to treat cyanide toxicity and works by donating sulfur to liver rhodanase to enhance conversion of cyanide to thiocyanate. 1254

Question 90

For an AR disease, an unaffected individual (with unaffected parents) who has a sibling affected by an AR condition has _____ chance of being a carrier for that condition

Answer 90

2/3 chance

See 1790

Question 91

What are the SE of chloramphenicol

Answer 91

Supresses bacterial protein synthesis by binding to the 50S RSU and inhibiting the peptidyl transferase enzyme.

SE: dose-related anemia, leukopenia, and/or thrombocytopenia that are reversible. Also causes dose-independent aplastic anemia, which is usually severe and fatal without treatment. 359

Question 92

What happens with Hyper-IgM syndrome

Answer 92

Inability of B-lymphocytes to undergo isotype switching from IgM to other immunoglobulin isotypes –> lymphoid hyperplasia and recurrent sinopulm infections. MC d/t genetic abscence of CD40 ligand on T-lymphocytes.

NOTE: the genes coding for constant region of heavy immunoglobulin chains lie next to one another in following order: IgM, IgD, IgG, IgE, IgA. IgM is the initial immunoglobulin synthesized by all B-lymphocytes prior to class switching. 541

Question 93

Describe Typhoid Fever

Answer 93

Salmonella Typhi or Paratyphi and presents with escalating fever (with inital diarrhea or constipation), followed by abd pain, formation of rose spots on the chest/abd, and hemorrhagic enteritis with possible bowel perforation. Usually occurs after traveling to an edemic region; fecal-oral following ingestion of contaminated food/water. 1138

Question 94

The finding of interstital PN in a transplant patient with intranuclear and cytoplasmic inclusion bodies histologically points to what?

Answer 94

Opportunistic infection with CMV, which is an enveloped virus that contains a dsDNA genome. 1576

Question 95

Why can’t atropine reverse all the effects of organophosphate toxicity

Answer 95

Organophosphates stimulate both muscarinic and nicotinic cholinergic receptors. Atropine reverses muscarinic effects but does not prevent the development of nicotinic effects such as muscle paralysis. Pralidoxime is the only medication tht reverses both muscarinic and nicotinic effects by “restoring” cholinesterase from its bond with these substances. 1323

Question 96

CN 3 (oculomoter) exits the midbrain and courses between which arteries?

Answer 96

Posterior cerebral and superior cerebellar arteries. An aneurysm arising from either artery can lead to a non-pupil-sparing third nerve palsy, which clinically presents with unilateral HA, eye pain, diplopia, dilated nonreactive pupil, and ptosis with the ipsilateral eye in a down and out position. 2126

Question 97

Whats a porcelain gallbladder and what does it increase your risk of

Answer 97

Calcium-laden gallbladder than can develop in some patients wiht chronic cholecystitis. Cholecycstectomy is recommended b/c of increased risk of gallbladder carcinoma

Question 98

Which regions are safe/not safe for intragluteal injections.

Answer 98

Superomedial: risk injury to superior gluteal nerve

Superomedial, Inferomedial, Inferolateral: risk injury to sciatic nerve

Superolateral quadrant is a relatively safe site for intragluteal injections, although the anterolateral gluteal region is preferred. 1640

Question 99

Which agent could have been administered with MTX and prevented fever, painful mouth ulcers, and pancytopenia

Answer 99

Folinic acid (leucovorin) can reverse the toxicity of methotrexate in non-cancerous cells in the GI mucosa and bone marrow if administered at the appropriate time. Leucovorin, a 5-formyl-derivative of THF acid, does not require the action of DHFR for its conversion to THF. 1818

Question 100

What regulates the number of atrial impulses that reach teh ventricle and determines the ventricular contraction rate in conditions where teh atria undergo rapid depolarization?

Answer 100

Atrioventricular node refractory period

AFib occurs d/t irregular electrical activity within the atria and presents with absent P waves, irregularly irregular R-R intervals and narrow QRS complexes. 1977

Question 101

Describe the S4 heart sound

Answer 101

Sign of diastolic dysfunction and occurs when there is a sudden rise in end-diastolic ventricular pressure caused by atrial contraction against a ventricle that has reachd its elastic limit. Present in any condition that cuases reduced ventricular compliance (e.g. hypertensive heart disease, aortic stensois, hypertrophic cardiomyopathy). It is heard as a low-frequency late diastolic sound that occurs just prior to S1. 246

Question 102

Why does pyruvate kinase deficeincy cause splenomegaly

Answer 102

Causes hemolytic anemia d/t failure of glycolysis and resultant failure to generate sufficent ATP to maintain erythrocyte structure. In this case, splenic hypertrophy results from increased work of the splenic parenchyma, which must remove these deformed RBCs from circulation. 1020

Question 103

Why do we get wrinkles?

Answer 103

Secondary to decreased synthesis and net loss of dermal collagen and elastin

Question 104

In healthy individuals, the difference in bone density curves for osteoporosis can be best explained by?

Answer 104

Genetic differences 627

Question 105

Patients with HIV are at greatest risk of developing what B-cell malignant proliferation

Answer 105

HIV+ pts often experience reactivation of latent EBV infections with a resulting incresed incidence of EBV-induced lymphoproliferative disorders, including the aggressive non-Hodgkin’s diffuse B-cell lymphomas. 1724

Question 106

Failure of which ducts to properly fuse can cause a bicornuate uterus or uterus didelphys

Answer 106

Paramesonephric ducts fuse to form the uterine tubes, uterus, cervix, and superior 1/3 of the vagina.

Uterus didelphys: occurs when there is total nonfusion of the paramesonephric ducts; seperate vagins, cervices and uterine horns. 1831

Question 107

Describe dystrophic calcification

Answer 107

Considered a hallmark of cell injury and death, occuring in all types of necrosis in the setting of normal calcium levels. Grossly, dystrophic calcium deposits are fine, gritty, white granules or clumps.

In aged (or damaged) cardiac valves, thought to be d/t endothelial and fibroblast death secondary to chronic hemodynamic stress or atherosclerotic inflammation. Subsequent release of cellular degradation products into valvular interstitum then promotes calcification and thickenign of valve leaflets. These changes are benign in elderly (aortic sclerosis); however, over time, progressive valvular stiffening can lead to outflow obstruction (calcific aortic stenosis). 296

Question 108

What form of rejection occurs immediately upon initial perfusion of the transplanted organ and is often diagnosed intraoperatively due to mottling and cyanosis of the organ?

Answer 108

Hyperacute rejection is an antibody-mediated reaction (Type II HSR) caused by preformed IgG antibodies within the recipient that are directed against donor antigens. Examples include anti-ABO and anti-HLA antibodies. Morphology: gross mottling and cyanosis; arterial fibrinoid necrosis & capillary thrombotic occlusion. 569

Question 109

What are the 4 basic methods that health insurance plans use to reimburse physicians

Answer 109

• Capitation: paid a fixed amount per enrollee, not per service. Have incentives to contain costs d/t fixed budged; MDs motivated to provide more preventative care (e.g. pap smears/mammo) and better health counseling.
• Fee-for-serve (FFS): **paid fixed amount for every service and diagnostic test; no incentive to avoid costly tests and procedures. **
• Discounted FFS: reimbursed a discounted amount; may be more conservative when ordering tets and providing services compared to FFS.
• Salary: fixed amount and pay is not tied to number of enrollees or services; no finanical incentive to change their treatment patterns, either in services provided or number of follow-up visits. 8456

Question 110

Extended consumption (for longer than 3 months) of appetite suppressants such as fenfluramine or phentermine is associated with what?

Answer 110

Increased incidence of pulmonary HTN, which manifests with dysnpea on exertion, and can progress to cor pulmonale with right ventricular hypertrophy, potentially leading to sudden cardiac death. 199

Question 111

What is an antihypertensive that would have minimal effect on AV conduction and would be useful for patients with bradycardia

Answer 111

Nifedipine: causes peripheral vasodilation (vasculature specific) which may result in reflex tachycardia; therefore this antihypertensive is useful for patients with bradycardia. 145

NOTE:

• Amlodipine, nimodipine, nifedipine (dihydropyridines; more specific for vascular smooth muscle). All (except nimodipine) are used for HTN, angina (including Prinzmetal), and Raynauds
• Diltiazem and Verapamil (non-dihydropyridine; more specific for heart; verapamil = ventricle): HTN, angina, afib/flutter; slow conduction through AV node.
• Nimodipine: subarachnoid hemorrhage (prevents cerebral vasospasm)

Question 112

What are the three variables that affect the total oxygen content of blood?

Answer 112

1. Hemoglobin concentration: 1g of hemoglobin can carry 1.34 mL of oxygen when fully oxygenated
2. Oxygen saturation of hemoglobin (SaO2)
3. Partial pressure of oxygen dissolved in blood (PaO2): dissolved oxygen is not bound to hemoglobin, and accounts for a very small proportion of the total oxygen content of blood.

Anemia: blood hemoglobin concentration is decreased. Thus, PaO2 (dissolved oxygen - independent of hemoglobin concentration) and SaO2 (% hemoglobin saturation with oxygen) can be normal, but total oxygen content of blood is decreased. 1527

Question 113

What does the CSF analysis show for bacterial meningitis and what is the most common cause in adults of all ages?

Answer 113

CSF: elevated opening pressure, increased neutrophils, decreased glucose, elevated protein

Strep pneumoniae: lancet-shaped, gram-positive cocci in pairs. Meningitis often follows a pulm infection or mild URI. Alcohols, sickle cell anemia patients, and asplenics are at greater risk. 735

Question 114

How can porphyrias be classified and how are acute attacks precipitated?

Answer 114

Deficiency of any enzymes responsible for porphyrin synthesis can result in porphyria, which can be classified as either hepatic or erythropoietic, dpending on site of enzymatic deficiency. Heme is synthesized in liver for use in CYP450 system, while in bone marrow is generated for Hb use.

Acute attacks of intermittent hepatic porphyria can be precipitated by drugs such as phenobarbital, griseofulvin, phenytoin. Additionally, alcohol, hypoxia, and a low caloric diet can induce an attack. All of these factors decrease hepatic concentration of heme, which causes an increase in hepatic ALA synthase activity and increased formation of aminolevulinic acid and porphobilinogen (heme normally serves to inhibit synthesis of ALA synthase) –> abd pain + neuro manifestation,s no photosenstivity, urine darkens upon standing. 1338

Question 115

Explain how bacterial mRNA can be polycistronic using the lac operon as an example

Answer 115

Polycistronic: one mRNA codes for several proteins. For example, all 3 proteins of the lac operon (beta-galactosidase, permease, and transacetylase) are synthesized from a single mRNA molecule containing z, y, and a gene sequences, respectively.

Bacterial lac operon codes for proteins necessary for lactose metabolism by E. coli. The transcription and translation of these bacterial proteins is regulated by a single promoter, operator, and set of regulatory elements. 1485

Question 116

What is the mechanism explaining the potentially beneficial effect of using drugs that inhibit fatty acid oxidation in treatment of stable angina?

Answer 116

In stable angina, atherosclerosis leads to reduced O2 delivery to cardiac mitochondria resulting in mismatch between myocardial oxygen demand and supply. Since glucose oxidation requires less oxygen, it is believed that shifting energy production from FA oxidation to glucose oxidation may be more oxygen efficient and beneficial in treating angina (i.e. less oxygen use per one ATP synthesized). This not only decreases the amount of oxygen needed to support cardiac fxn, but also decreases potentially toxic FA metabolite production. 950

Question 117

What is the morphology of craniopharyngiomas and what are they remnants of

Answer 117

Morphology: calcified cystic tumors that are lined by stratified squamous epithlelium. Keratin parls may also be seen. Filled with a yellow, viscous fluid that is rich in cholesterol.

Arise from remnants of Rathke’s pouch (an embryonic precursor of the anterior pituitary/adenohypophysis), which is an evagination fo ectoderm that lines the fetal oral cavity. NOTE: posterior pituitary (neurohypophysis) develops from neruoectoderm.

Sx: HA, growth failure, bitemporal hemianopia. 1152

Question 118

Describe the effects of BBs on renin, angiotension I and II, aldosterone and bradykinin

Answer 118

Beta-adrenergic pathway is mediated through sympathetic stimulation of beta-1 receptors on JGA cells; NE binds to beta-1 receptors and stimulates renin release. Thus BBs inhibit renin release, reduce angiotensin I and II, and aldosterone levels. No affect on ACE activity, and thsu do not affect bradykinin levels. 692

Question 119

Explain gonadotropin regulation in males

Answer 119

Leydig cells (analogues to female theca cells): produce testosterone in response to stimulation by LH. Through a negative feedback mechansim, testosterone inhibits both LH and GnRH.

Sertoli cells (analogues to female granulosa cells): produce hormone inhibin in respone to FSH, maintain spermatogenesis, and secrete mullerian inhibitory factor during male embryogenesis. Inhibin suppresses FSH production by AP but does not feedback on hypothalamus. Thus, selective impairment of Sertoli cell fxn would lead to decreased inhibin and increased FSH. 1902

Question 120

Intermittent respiratory symptoms in a patient with a normal CXR, occassional sputum eosinophils, and reduced FEV1 suggests what?

Answer 120

Asthma: bronchial biopsy typically demonstrates a thickened mucosa with eosinophilic infiltrates. Flares occur following exposure to airborn allergens that interact with IgE bound to pulmonary mast cells. Extrinsic allergic asthma provoked by inhaled allergens such as animal dander is the most common type. 1925

Question 121

Explain the findings in a patient with sickle cell trait

Answer 121

Patients who are heterozygous for sickle cell trait (Hb AS) have Hb composd of 35-40% HbS; they are generally protected from sickle cell crises, aplastic crises, and sequestration crises by presence of >50% normal hemoglobin (HbA). Usually have normal peripheral smears and indies, reticulate counts, and MHCH values. Also enjoy relative protection from Plasmodium falciparum. However, sickle cell trait RBCs will sickle when sodium metabisulfite is added. 895

Question 122

Contrast the layers of Zenker vs. Meckel Diverticulum

Answer 122

True diverticulum has all 3 gut wall layers outpouch (mucosa, submucosa, and muscularis) vs. False diverticulum where only mucosa and submucosa outpouch (occur esp. where vasa recta perforate muscularis externa). 328

Zenker: pharyngoesophageal false diverticulum. Herniation of mucosal tissue at Killian triangle b/w thyropharyngeal and cricopharyngeal parts of inferior pharyngeal constrictor. Dysphagia, obstruciton, halitosis; elderly males

Meckel: true diverticulum; persistence of the vitelline duct. May contain ectopic acid-secreting gastric mucosa and/or pancreatic tissue. Can cause melena, RLQ pain, intussuscpeption, voluvlus, or obstruction near terminal ileum; first 2 years of life.

Question 123

Describe the transport of ammonia by alanine and glutamate

Answer 123

Alanine is the major AA responsible for transferring nitrogen to the liver for disposal.

During the catabolism of proteins, alanine is transaminated by alanine aminotransferase to pyruvate with the amino acid group being transferred to alpha-ketoglutarate to form glutamate. Glutamate is further metabolized by glutamate dehydrogenase, which liberates free ammonia and regenerates alpha-ketoglutarate. Ammonia then enters urea cycle to form urea, the primary disposal form of nitrogen in humans. Free ammonia is also excreted into urine by kidney for regulation fo acid-base status. 1369

Question 124

Describe Friedreich ataxia

Answer 124

AR disorder d/t mutation of a gene that codes for protein frataxin, which is essential for normal mitochondrial fxn. An increased number of trinucleotide repeats is present in the mutated gene, causing diminished levels of frataxin. 5-15 y/o with gait ataxia (progressively slow and clumsy walking), wide-based gait, and dificulty maintaing balance. 672

• Ascending and descending spinocerebellar tract degeneration causes gait ataxia
• Degeneration of dorsal columns and DRG causes loss of position and vibration sense
• Kyphoscoliosis and foot abnormalities (pes cavus)
• Hypertrophic cardiomyopathy and CHF
• Diabetes mellitus

Question 125

Describe the full extent of patient confidentiality

Answer 125

Unethical to discuss any information regarding the patient’s diagnosis, treatment, prognosis, etc with a physician who is not involved in the patient’s care. Likewise, the physician should neither confirm nor deny whether the person of interest is, in fact, a patient. 7733

Question 126

Describe the MOA of Morphine

Answer 126

Binding of morphine to mu receptors results in G protein-coupled activation of K+ conductance. K+ eflux increases and causes hyperpolarization of postsynaptic neurons effectively blocking pain transmission. 776

Other possible secondary messenger pathways of mu opioid receptor activation include inhibition of AC, inhibition of Ca2+ conductance, and inhibition of transmitter release.

Question 127

Describe the MOA of Flutamide

Answer 127

Used in treatment of prostate cancer in combo with GnRH agonists. Non-steroid anti-androgen that competes with testosterone and DHT for testosterone receptors. Prevention fo androgen-receptor binding blocks the stimulatory effect of androgens on the primary tumor and metastases and leads to reduction in their size. 657

Question 128

What is digital clubbing (i.e. thickening of the distal phalanges; flattening of nail folds and shinniness of nail and distal portion of finger) associated with?

Answer 128

Prolonged hypoxia. It can be secondary to the following chronic conditions:

• Lung diseases: lung cancer (esp. large-cell), TB, CF, bronchiectasis, pulm HTN, empyema
• Heart diseases: cyanotic congenital heart diseases (esp. TOF) and bacterial endocarditis
• Other: IBD, hyperthyroidism, malabsorption

820

Question 129

Corynebacterium diphtheriae can acquire pathogenicity and thus the ability to cause severe pseudomembranous pharyngitis through which mechanism?

Answer 129

Acquires virulence via bacteriophage-mediated“infection” with the Tox gene, which codes for diphtheria AB exotoxin. This process, whereby a bacteriophage infects a host bacterium and integrates its genome into the host bacterium’s genome is termed lysogenization. 1389

Question 130

Where is low-frequency vs. high-frequency sound best detected?

Answer 130

Low-frequency sound is best detected at the apex of the cochlea near the helicotrema. High-frequency sound is best detected at the base of the cochlea near the oval and round windows. 1520

Question 131

Describe the metabolism of fructose and disorders resulting from enzyme deficiencies

Answer 131

Involves enzymes fructokinase, aldolase B and triokinase. 1067

Essential Fructosuria: AR asymptomatic disorder d/t fructokinase deficiency. Fructose (reducing sugar) from the diet is absorbed in gut and secreted in urine unchanged.

Fructose Intolerance: AR disorder of aldolase B (converts fructose-1-phosphate to DHAB and glyceraldehyde). Infants present after consumption of fruit, juice, or honey with hypoglycemia, jaundice, cirrhosis and vomitting. Tx: decrease intake of both fructose and sucrose (glucose + fructose).

Question 132

What is the cellular receptor for each of the following virions: CMV, EBV, HIV, Rabies, Rhinovirus

Answer 132

• CMV: cellular integrins
• EBV: CR2 (CD21)
• HIV: CD4 and CXCR4/CCR5
• Rabies: nicotinic ACh receptor
• Rhinovirus: ICAM1 (CD54)

Question 133

How does hepatitis B virus replicate?

Answer 133

dsDNA –> template +RNA –> progeny dsDNA

The HBV genome is a partially double stranded circular DNA molecule, and replication of this genome is accomplished through a reverse transcriptase DNA polymerase that creates an intermediate + single-stranded RNA template. The progeny of this process is dsDNA. 374

Question 134

Retroperitoneal hematoma in a stable patient is most likely to occur due to damage to what organ?

Answer 134

Pancreas! Pancreatic injury with formation of a retroperitoneal hematoma can occur d/t severe blunt or penetrating abdominal trauma. 838

Retroperitoneal Structures: SADPUCKER = Suprarenal (adrenal) glands, Aorta and IVC, Duodenum (2nd-4th parts), Pancreas (except tail), Ureters, Colon (descending and ascending), Kidneys, Esophagus (lower 2/3), Rectum (partially).

NOTE: rupture of intraperitoneal organs would lead to hemoperitoneum (free blood in peritoneal space).

Question 135

What is the drug of choice for mucormycosis?

Answer 135

Amphotericin B - binds ergosterol in fungal cell membranes to form holes. Toxicity: renal vasoconstriction and reduction in GFR. Hypokalemia and hypomagnesemia are the two most serious electrolyte distrubances.

Question 136

How does HUS present?

Answer 136

Affects young children and manifests with acute renal failure, MAHA, and thrombocytopenia. Labs include decreased RBC count, hematocrit and platelet count and increased bleeding time, LDH, BUN, and creatinine.

Shiga toxin (verotoxin) enters circulation from bowels and induces vascular damage leading to capillary thrombus formation –> consume platelets and cause mechanical damage to RBC –> hemolytic anemia causes pallor, weakness, and tachycardia. Thrombocytopenia may lead to petechaie and purpura. 1851

Question 137

What are the signs and causes of lithium toxicity

Answer 137

Sx of lithium toxicity: neuromuscular excitability, irregular coarse tremors, fasicular twitching, agitation, ataxia, and delirium. HD is the most effective way of acutely reducing blood lithium level. 519

Lithium is almost exclusively excreted by the kidneys, with filtraiton and reasorption in the proximal tubules following sodium reabsorption. Renal injury, toxins, and drugs that lead to increased proximal tubular absorption of sodium (e.g., NSAIDs, thiazides, ACE-I) also increase lithium levesl and elevate risk of toxicity.

Question 138

What is the MAO and one of the unique AE of ethambutol

Answer 138

Antimycobacterial agent that inhibits carbohydrate polymerization by inhibiting arabinosyl transferase, thereby preventing peptidoglycan cell wall synthesis. AE is optic neuritis, which typically presents in conjuction with decreased visual acuity, central scotoma and color blindness. 1311

Question 139

What will the Keq be if DeltaG is positive vs. negative

Answer 139

If deltaG is negative, Keq will be greater than 1, and the concentration of products at equilibrium will exceed that of substrates.

If deltaG is positive, Keq will be less than 1, and the formation of substrates will be favored.

An equilibrium constant of 1 would occur in a state where deltaG is zero.

Question 140

What do schistocytes suggest?

Answer 140

Either MAHA (e.g. TTP, HUS, DIC) or mechanical damage (e.g. prosthetic valve).

Both HUS and TTP come under same spectrum of dise with pentad: fever, neurologic manifestations, renal failure, thrombocytopenia, and microangiopathic hemolytic anemia. Usually TTP occurs in adults with predominant neuro sx vs. HUS in children with primarily renal involvement.

Question 141

When is myxomatous changes in the media of large arteries found?

Answer 141

Cystic medial degeneration, which predisposes to the development of aortic dissections and aortic aneurysms. Medial degeneration is frequently seen in younger individuals with Marfan syndrome. 462

Question 142

What type of adipose tissue is found in newborns and hibernating animals

Answer 142

Brown adipose tissue, which contains several intracytoplasmic fat droplets and many more mitochochondria (provides the tan color) than white adipose cells. They fxn to produce heat by uncoupling oxidative phosphorylation with the protein thermogenin. 821

Question 143

Compare/Contrast bacterial vaginosis vs. trichomoniasis

Answer 143

Bacterial vaginosis: thin, white discharge with fishy odor (positive “whiff” test on addition of KOH); clue cells at pH >4.5.

Trichomoniasis (trichomonas vaginalis): frothy, grey-green, foul-smelling discharge; strawberry cervix; motile trichomonads with pH >4.5

Question 144

What environmental and genetic factors cause insulin resistance?

Answer 144

FFA (act to decrease insulin secretion and may also be d/t serine phosphorylation of the insulin receptor –> serine kinase becomes activated instead of tyrosine kinase; mechanism of resistance induced by TNF alpha, glucagon, and glucocorticoids) and serum triglycerides are believed to increase insulin resistance in overweight individuals. 1328

Question 145

What maneuvers can be used for Paroxysmal Supraventricular Tachycardia

Answer 145

PSVT is d/t re-enterant circuit in the AV node. Episodes are usually treated with adenosine in the hospital setting, but vagal maneuvers (increase cardiac PNS tone, which functions to slow the HR by slowing conduction through the AV node which will abolish the re-enterant circuit) such as carotid sinus massage and Valsalva can also be used. 1515

Question 146

Describe villous adenomas

Answer 146

Adenomatous polyps: tubular, villous, and tubulovillous. Tubular tend to be smaller and pedunculated, while villous are larger and more commonly sessile. Sometimes villous adenomas can have velvety or cauliflower-like projections. Villous adenomas can cause bleeding, secretory diarrhea (villous adenomascan secrete large amounts of mucous), and partial intestinal obstruciton; high risk progression to adenocarcinoma. 430

Question 147

Describe the response generated by inactivated vs. live-attenuated vaccines, specifically influenza

Answer 147

Inactivated viral vaccines predominately generate a humoral immune response. Live-attenuated can generate a strong cell-mediated and humoral response.

Inactivated versions of influenza fxn by inducing neutralizing antibodies against the hemagglutinin antigen. Upon exposure to influenza virus through natural infection, these antibodies inhibit binding of hemagglutinin to sialylatd receptors on host cell –> prevents virus from entering cells via endocytosis. 1466

Question 148

Tissues supplied by which artery would most likely be affected by compression of the splenic artery?

Answer 148

Splenic artery originates from celiac artery and gives off several branches to stomach and pancreas (pancreatic, short gastric, and left gastroepiploic) before reaching spleen.

D/t poor anastomoses, the gastric tissue supplied by the short gastric arteries is vulnerable to ischemic injury following splenic artery blockage. 8574

Question 149

H. pylori antral gastritis is associated with formation of what kind of ulcers and why?

Answer 149

Duodenal ulcers d/t increased gastric acidity from unchecked gastric production secondary to destruction of somatostatin-secreting cells in the gastric antrum. H. pylori is also strongly associated with gastric adenocarcinoma and lymphoma. 1603

Question 150

Describe how intimal injury occurs

Answer 150

Can occur via atherosclerosis and chronic chemical and inflammatory exposures. Vascular reaction to injury, including endothelial injury, involves migration of medial smooth muscle cells (SMCs) across internal elastic lamina and into the intima followed by **SMC proliferation and collagen synthesis –> reactive intimal hyperplasia. **

Injured endothelial cells release PDGF which promotes SMC migration and proliferation. Also express surface vascular cell-adhesion molecules (VCAMs) that allow adherence of monocytes and lymphocytes as well as their diapedesis into intma. 443

Question 151

Substance produced by EHEC shares many properties with the toxin produced by…

Answer 151

Shiga-like toxin produced by EHEC are nearly identical to the shiga-toxin produced by Shigella dysenteriae. These toxins fxn to inhibit the 60S RSU in human cells, thereby blocking protein syntheis by preventing bindign of tRNA. This mechanism differs from that of diphtheria toxin and exotoxin A of Pseudomonas in that the latter toxins act on EF-2. 1098

Question 152

The combination of fixed segmental loss of upper extremity pain and temp sensation, upper extremity LMN signs, and/or lower extremity UMN signs in setting of scoliosis suggets…

Answer 152

Syringomyelia: cystic dilation in cervical spinal cord slowly enlarges, characteristically causing damage to ventral white commissure (decussation of lateral spinothalamic tract neurons) and anterior horns (site of LMN cell bodies). Most commonly above C8-T1 cord levels. Further expansion can produce lower extremity weakness and hyperreflexia (UMN defect) by affecting lateral corticospinal tract. 1904

Question 153

Explain the cause and presentation of a psoas abscess

Answer 153

Can occur as the result of hematogenous or lymphatic seeding from a distant site or by spread from an adjacent site. Patients can present with fever, back or flank pain, inguinal mass, and difficulty walking. Inflammation of psoas muscle causes pain when hip is extended (psoas sign). Patients typically position themselves to minimize psoas stretching and discomfort, with hip flexion and lumbar lordosis. 8710

Question 154

Describe what happens when conduction between SA and AV nodes is impaired

Answer 154

**AV nodal cells **can become pacemakers. In a complete (third-degree) AV block, the atria and ventricles depolarize independently of each other. QRS complexes are narrow since ventricular depolarization proceeds normally. AV node produces a HR of 45-55 bpm.

When electrical impulse is generated below the AV node and His bundle, the HR can slow to 20 bpm and the EKG will show prolonged abnormally shaped QRS complexes. 1976

Question 155

Describe the histological apperance of papillary carcinoma

Answer 155

Most common type of thyroid cancer. Cells are large with overlapping nuclei containing finely dispersed chromatin, given them a ground-glass appereance (Orphan Annie eye). Numerous intranuclear inclusions and grooves can be seen d/t invagination of nuclear membrane. Psammoma bodies are also found within tumor. 1658

Question 156

SCC of esophagus

Answer 156

Progressive dysphagia. Major risk factors include EtOH consumption and tobacco. Consists of solid nests of neoplastic squamous cells with abundant eosinophilic cytoplasm and distinct borders. Areas of keratinization are easily identified. 287

Question 157

Describe the law of conservation of mass as applied to fluid dynamics

Answer 157

Tells us that the total flow of mass into a contained system must be equal to the total flow of mass from the system in steady state. 245

Total Flow = Flow Velocity * Cross Sectional Area

e.g. Vol_in = A1 * V1 = Vol_out = A2 * V2

Question 158

What exits at foramen rotundum, ovale, spinosum and jugular foramen?

Answer 158

Rotundum: CN V2 (maxillary nerve)

Ovale: CN V3 (mandibular nerve), lesser petrosal nerve, accessory meningeal artery, emissary veins

Spinosum: middle meningeal artery and vein, meningeal (recurrent) branch of CN V3

Jugular Foramen: CN IX, X, and XI, the inferior petrosal and sigmoid sinuses, and posterior meningeal artery

Question 159

Drug induced lupus has been linked to drugs that are metabolized by…

Answer 159

**N-acetylation **in the liver. Patients who are slow acetylators are at greater risk for developing lupus-like syndrome.

Having Lupus is “SHIPP-E”: Sulfa drugs, Hydralazine, INH, Procainamide, Phenytoin, Etancercept

Question 160

What are two short acting benzodiazepines?

Answer 160

Triazolam or alprazolam

1352

Question 161

The net number of molecules diffusing across a semipermeable membrane per second is proportional and inversly proportional to…

Answer 161

Proportinal to the molecules concentration difference across the membrane, the total membrane surface area, and the solubility of the substance .

Inversely proportional to the total membrane thickness and MW of the molcule. 1988

Question 162

What would cardiac cath show for aortic regurgitation (AR)

Answer 162

High peaking LV and aortic pressures during systole and steep diastolic decline in aortic pressure, resulting in an increased pulse pressure.

The peak intensity of an AR murmur occurs after closure of the incompetent aortic valve, at the point when the pressure gradient between the aorta and LV is at its maximum. Murmur is typically best heard along left sternal border, with the patient leaning forward and at end expiration. 227

Question 163

Describe the effects of dopamine based on dose

Answer 163

Low doses: stimulate D1 receptors in renal and mesenteric vasculature resluting in vasodilation and increased blood flow to these sites

Higher doses: increase cardiac contractility by stimulating beta-1 adrenergic receptors

Higher Higher doses: generalized vasoconstriction by an alpha-1 adrenergic effect. 1365

Question 164

Describe the oxygenation of blood in the fetus

Answer 164

The most highly oxygenated blood is carried by the umbilical vein (forms ligamentum teres in adult) –> liver, where it bypasses the hepatic circulation via the ductus venosus and enters the IVC. From the IVC, blood goes to heart where it is either pumped into pulmonary circulation or crosses from R to L heart via FO. Fraction of blood pumped into pulmonary circulation may bypass lungs via ductus arterosus (ligamentum arteriosum) and pass directly into descending aorta –> fetal tissues –> umbilical arteries carry deoxygenated blood back to the placenta. 1833

Question 165

What is the genetic defect in fragile X syndrome

Answer 165

The Fragile X Mental Retardation 1 (FMR1) gene is located on the long arm of X chromosome. An increased number of CGG trinucleotide repeats lead to hypermethylation of cytosine bases and subseuent gene inactivation. 1421

Sx: mental retardation, long thin face with prominent forehead and jaw, post-pubertal macroorchidism, large protruding ears, tooth crowding, arched palate.

Question 166

Why is there a widened, negative transepithelial potential difference in CF?

Answer 166

CFTR protein normally secretes Cl- into the lumen, and also has a tonic inhibitory effect on opening of the apical Na+ channel (which absorbs Na+ into the cell). Impaired CFTR functioning directly reduces ductal epithelial Cl- secretion and indirectly increases Na+ absorption by releasing the inhibitory effect on apical Na+ channel. These changes occur in most exocrine glands (other than sweat glands). 804

Overall: reduced luminal Cl- secretion and increased Na+ and net H₂0 absorption –> dehydrated mucus.

Question 167

What are known host cell receptor - virion/virion protein binding specificities?

Answer 167

Many viruses bind to normal host cell plasma membrane receptors in order to enter host cells. 1375

CD4 and HIV gp120

C3d complement component (CR2 or CD21) and EBV gp350: CD21 is normally present on the surface of B cells and nasopharyngeal epithelial cells.

erythrocyte P antigen (globoside) and Parvovirus B19

Question 168

What does the Health Care Consent Act allow

Answer 168

Allows a physician to treat an incapacitated patient without consent in an emergency setting (i.e. patient is unresponsive and not carrying a blood refusal card, and communication with the next of kin surrogate decision maker is not possible). In an emergency situation in which the patient does not have capacity, consent is not required to provide life-saving treatment. In an emergency, the physician should always provide potentially life-saving therapy to a minor. 783

Question 169

An untreated, prolactin secreting pituitary adenoma puts a 40 y/o female at greatest risk of developing what?

Answer 169

High levels of prolactin supress GnRH secretion, leading to hypogonadism (can also cause galactorrhea in females) and thus low estrogen in females. Estrogen maintains bone mass in females, so any loss of estrogen - whether from menopause, hormone imbalances, or surgical removal of ovaries-leads to loss of bone density (osteoporosis). 233

Question 170

Treatment with which drug can most closely mimic Glanzmann Thrombasthenia

Answer 170

Abciximab is a blocker of GPIIb/IIIa receptor; useful for treatment of unstable angina and acute coronary syndrome, particuarly those undergoing percutaneous coronary intervention.

Glanzman thrombasthenia: deficient or defective GPIIb/IIIa. Present in childhood with mucocutaneous bleeding. Peripheral smear shows no platelet clumping. 1079

Question 171

What is the triad of Wernicke Syndrome and what can be a complication?

Answer 171

Oculomotor dysfunction (e.g. horizontal nystagmus and bilateral abducens palsy d/t damage of CN III and VI, and vestibular nuclei), ataxia, and confusion form the triad. Most of these symptoms usually resolve after thiamine (vitamin B1) administration. Commonly involve mammillary bodies.

Korsakoff syndrome is a complication of Wernicke encephalopathy associated wtih damage to anterior and dorsomedial thalamic nuclei, the hallmarks of which are permanent memory loss and confabulation. 63

Question 172

In the abscence of ADH, tubular fluid from which site is most likely to have the highest osmolarity

Answer 172

ADH acts primarily on the collecting ducts, increasing their permeability to water. In the abscence of ADH, the tubular fluid is more concentrated at the junction between the descending and ascending limbs of the loop of Henle and most dilute in the collecting ducts. 1607

Question 173

Describe the degree of water reabsorption along the different segments of the nephron (review of 1607)

Answer 173

• Proximal Tubule: H20 passively rebsorbed along with active transport of solutes; fluid in lumen is isoosmotic with plasma.
• Descening Limb: permeable to H20 but not solutes; H20 moves down its concentration gradient from lumen into highly osmotic medulla. Fluid in lumen becomes hypertonic. In abscence of ADH, tubular fluid is more concentrated at end of descending limb
• Thick Ascending: impermeable to H20. Electrolytes are reabsorbed by NK2Cl cotransporter, causing osmolarity of tubular fluid to decrease; tubular fluid becomes hypotonic
• DCT: reabsorption of solutues continues thru NaCl symporter. B/c the early DCT is impermeable to H20, tubular fluid increases in hypotonicity.
• Collecting Ducts: In abscence of ADH, collecting ducts are impermeable to water and tubular fluid can become as hypotonic as 50 mOsm/L while solutes continue to be removed.

Question 174

What is the major long-term hemodynamic compensatory response to the volume overload of aortic regurgitation?

Answer 174

Increase in LV preload (i.e. LVEDV) in association wtih eccentric LV hypertrophy (adaptation to volume overload; “in series” synthesis of new myocardial sarcomeres). 237

NOTE: concentric hypertrophy is the response to pressure overload (e.g. aortic stenosis or systemic HTN) and involves “in parallel” deposition of new sarcomeres, which produces net ventricular wall thickening and a reduction in ventricular chamber size (decreased EDV)

Question 175

What is nondisjucntion

Answer 175

Failure of chromosomes pairs to seperate properly during cell division. This could be d/t failure of homologous chromosomes to seperate in meiosis I or failure of sister chromatids to seperate during meosis II or mitosis. Monosomies or trisomies can result from nondisjunction in meosis I or II. 8328

On restrictrion fragment length polymorphism (RFLP) each band represents a homologous chromosome, thus the presence of an extra band indiciates extra homolgous chromsome (problem in meiosis I when homolgous chromsomes are seperated). Presence of a darker, thicker band significes inheritance of both sister chromaids, which produce equal-size restriction fragments (but twice the normal amount)

Question 176

What is the effect on thyroid hormones in a patient with osteoporosis (i.e. with a fragility vertebral fraxture) being treated with HRT containing estrogen and progesterone

Answer 176

Increase in levels of thyroid binding globulin (TBG) lead to increase in circulating total T4 and T3. However, the level of free thyroid hormones remains normal, so patients remain euthyroid and have normal TSH levels. Increase in TBG is typically seen in pregnancy, with use of oral contraceptives, or with HRT.

Question 177

What local factors are most important in coronary blood flow autoregulation?

Answer 177

**Nitric oxide (endothelium derived relaxation factor) **is the most important mediator of coronary vascular dilation in large arteries and pre-arteriolar vessels. It is synthesized from arginine and oxygen by endothelial cells and causes vascular smooth muscle relaxation by a guanylate cyclase-mediated cGMP second messenger system.

Adenosine, a product of ATP metabolism, acts as a vasodilatory elemetn in small coronary arterioles. 1516

Question 178

Define Delusional Disorder

Answer 178

One or more delusions for at least a month in the abscence of other psychotic symptoms. Apart from behavior relating to the delusions, the patient’s actions are not obviously bizarre or odd and general functioning is not significantly impaired. Subtypes (erotomanic, grandiose, jealous, persecutory, somatic). 2046

Question 179

How does EHEC 0157:H7 cause infection

Answer 179

Causes HUS and is a common cause of bloody diarrhea. Associated wtih consumption of undercooked ground beef and elaborates a shiga-like toxin (phage encoded) capable of inhibiting protein synthesis (inactivate 60S RSU) in colonic mucosal cells and renal endothelial cells (EHEC does NOT invade the intestinal mucosa) This strain is unable to ferment sorbitol and does not produce a glucuronidase. 1100.

Question 180

All cells can synthesize ribose from glycolysis intermediates fructose 6-phopshate and glyceraldehyde 3-phopshate (even if the oxidative rxns of the HMP pathway are not active) with the help of what enzymes

Answer 180

Transketolase and Transaldolase (involved in non-oxidative steps). 1035

NADPH (reduced form of NADP) is produced mainly when glucose is metabolized via the HMP. NADP, in contrast to NAD, is primarily used as a reducing equivalent in the cytosol rather than as a source of energy for ATP synthesis in ETC. The HMP shunt is also responsible for production of ribose 5-P needed for nucleotide synthesis. Conists of two types of reactions: oxidative (irreversible) and nonoxidative (reversible), both of which occur in the cytoplasm.

Question 181

What is seen on light microscopy in Guillain-Barre syndrome?

Answer 181

Segmental demyelination of peripheral nerves and an endoneural inflammatory infiltrate on LM.

Ascending flaccid paralysis and areflexia; affects young adults and starts a few weeks after a febrile illness; associated with camylobacter jejuni infection. 1058

Question 182

In prospective studies, disproportionate loss to follow-up between the exposed and unexposed groups creates the potential for what type of bias?

Answer 182

Attrition bias (if the lost subjects differ in thier risk of developing the outcome compared to the remaining subjects), which is a form of selection bias (i.e. systematic differences between groups in terms of treatment response or prognosis). 1188

Question 183

What drugs are known to cause acneiform eruptions?

Answer 183

Anabolic steroids (e.g. methytestosterone) are androgens. After conversion to dihydrotestosterone, androgens promote both follicular epidermal hyperproliferation and excessive sebum production –> acne development. 7585

Other drugs: epidermal growth factor receptor inhibitors and lithium

Question 184

Explain cause and pathophysiology of lactose intolerance

Answer 184

Lactose in the diet is catabolized into glucose and galactose by an intestinal brush-border disaccharidase called lactase (a type of beta-galactosidase).

Secondary lactase deficiency occurs in association with celiac sprue and viral gastroenteritis (i.e. diseases that damage the epithelial cells in the microvilli of the small intestine that contain lactase). Cause abdominal distention, flatulence, and diarrhea after lactose ingestion. 1072

Question 185

What drugs only reverse vagally-mediated bronchoconstriction?

Answer 185

Antimuscarinic agents (ipratropium). 170

NOTE: Methylxanthines like theophylline and aminophylline cause bronchial dilation by decreasing phosphodiesterase enzyme activity, thereby increasing intracellular cAMP.

Question 186

Explain how nitrate drugs mimic the action of endothelial derived relaxing factor (i.e. nitric oxide, NO)

Answer 186

Transformed to NO at the vascular smooth muscle cell membrane which leads to increased cGMP, decreased intracellular calcium, decreased activity of MLCK, and myosin dephopshorylation and smooth muscle relaxation. 136

Question 187

What muscles make up the rotator cuff and which tendon is most commonly injured?

Answer 187

Rotator cuff is made up of the tendons of the supraspinatus, infraspinatus, subscapularis, and **teres minor. **

Most commonly injured tendon is the supraspinatus (primarily an abductor of arm) because this tendon is prone to repeated impingement trauma between teh humeral head and the acromion. Thus, most commonly associated with pain during abduction of the humerus. 1733

Question 188

Explain how triglyceride stored in adipose tissue is metabolized

Answer 188

Metabolized to FFAs and glycerol by hormone sensitive lipase. Glycerol is then transported to the liver where it is phosphorylated to glycerol-3-phopshate by the liver-specific enzyme glycerol kinase. Subsequently, glycerol-3-phosphate is converted to DHAP by glycerol-3-phosphate dehydrogenase. DHAP can be used to produce ATP through glycolysis or glucose through gluconeogenesis. Glycerol in the liver can also be utilized for triglyceride synthesis. 1889

Question 189

How is glycogen degradation coupled with skeletal muscle contraction

Answer 189

Due to calcium-mediated myophosphorylase activation. Increasd calcium in the cytosol allosterically activates phosphorylase kinase, which then phosphorylates (Activates) muscle phosphorylase. 1028

Question 190

What are the acute effects of corticosteroids on the CBC

Answer 190

Increased neutrophil count and decreased lymphocyte, monocyte, basophil, and eosinophil counts. The increase in neutrophil count results from “demargination” of neutrophils previously attached to the vessel wall. 549

Question 191

Where does aspiration pneumonia typically develop

Answer 191

Due to gravity, supine patients typically aspirate into the posterior segments of the upper lobes and superior segments of the lower lobes. Patients who are upright tend to aspirate into the basilar segments of the lower lobes. Aspirated material is more likely to travel down the right main bronchus (mnemonic: “swallow a bite, goes down the right”). 1745

Question 192

Describe the clearence of particles from the respiratory tract based on size

Answer 192

Big particles (10-15um): trapped in URT

Medium (2.5-10um): enter trachea and bronchi and are cleared by mucociliary transport

Small (less than 2um): reach terminal bronchioli and alveoli and are phagocytized by macrophages –> activated alveolar macrophages release cytokines; also PDGF and IGF stimulate fibroblasts to proliferate and produce collagen –> inflammation + fibrosis –> pneumoconiosis (interstital lung fibrosis secondary to inhalation of inorganic dust). 536

Question 193

How can you remember where the actin and mysoin filaments are anchored?

Answer 193

Actin filaments are anchored into the Z-line of the sarcomere. The Z-line lies in the center of the lucent region referred to as the I-band.

Mnemonic: An Interesting Zoo Must Have Mammals (Actin in the I-band attaches at the Z-line, Myosin in the H-band attaches at the M-line). 1734

Question 194

Describe the steps involved in passage of circulating inflammatory leukocytes into inflamed tissue (review 8480)

Answer 194

1. Margination: neutrophils contact endothelial lining
2. Rolling: neutrophils roll on endothelium via loose binding of sialylated carbohydrate groups to L-selectin **on neutrophils or E-selectin/P-selectin on endothelial cells (cytokines induce endothelial expression of selectins)
3. Activation: slow rolloing allows leukocytes to sample chemokines secreted by inflammed tissue; this activates integrins resulting in a conformational change
4. Tight adhesion and crawling: neutrophils become firmly attached to endothelium via binding of CD18 beta 2 integrins (Mac-1 and LFA-1) to ICAM-1 on endothelial cells.
5. Transmigration: neutrophils migrate out of vasculature by squeezing b/w cells via integrin attachments and adherence to PECAM-1

Question 195

Describe the leukocyte adhesion deficiency (LAD) syndromes

Answer 195

AR disorders; leukocytes cannot leave the vasculature to migrate into tissues under conditions of inflammation. 8480

LAD type 1: abscence of CD18. Recurrent skin infections without pus formation, delayed detachment of umbilical cord, and poor wound healing.

Question 196

Pretreatment with which agents will decrease the effects of radiotherapy through competitive inhibiton of iodine transportation

Answer 196

Perchlorate and pertechnetate ions (as well as iodide isotopes) are absorbed in the thyroid gland via the sodium-iodide symporter. High levels of any one substance will signficiantly reduce the uptake of the others d/t competitive inhibition. 766

Question 197

Romantic and sexual relationship with which what type of patients are unethical

Answer 197

Relationship with current patients are unethical. Relationships between non-psychiatric physicians and former patietns may be ethically acceptable provided the physician-patient relationship is terminated prior to initiating a relationship with a patient. 10464

Question 198

Describe phenotypic mixing

Answer 198

Co-infection of a host cell by two viral strains, resulting in progeny virions that contain nucleocapsid proteins from one strain and the genome of the other strain. Since there is no change in the underlying viral genomes (no genetic exchange), the next generation of virions revert to thier original, unmixed phenotypes. 1462

Question 199

Improperly fitted crutches can cause what type of nerve injury?

Answer 199

Radial nerve injury (C5-T1) can occur d/t improperly fitting crutches (d/t its superficial location within the axilla). Can also be injured (along with the deep brachial artery) by **midshaft humerus fractures. **

Results in weakness of all forearm, wrist and finger extensors (“wristdrop”). 1685

Question 200

How is procainamide metabolized and how does this increase risk of drug-induced lupus

Answer 200

Metabolized via hepatic acetylation. Individuals who are “slow acetylators” are at greatest risk of drug-induced lupus, while those who metablize the drug more rapidly are less likely to experience this AE. 1505

Question 201

Glucose clerance will approximate the clearence of what substance when glucose transporters in the proximal tubule are inhibited

Answer 201

Glucose is normally freely filtered at the glomerulus and completely reabsorbed by the proximal tubule. Inhibition of sodium-coupled, carrier-mediated transport of glucose by the proximal tubule would cause the glucose clearence to approach the value of GFR (i.e. inulin which is also freely filterd at the glomerulus and is neither reabsorbed nor secreted by the renal tubules). 1559

Question 202

What is the S3 sound

Answer 202

Occurs just after S2 (best heard at cardiac apex in left lateral decubitus position) and is commonly associated with increased LVESV, which occurs in the setting of LV systolic failure.

2108 with audio

Question 203

How can you identify the cause of metabolic alkalosis

Answer 203

Characterized by high arterial blood pH, HCO3-, and pCO2. Determining volume status and measuring urinary Cl- concentration can help identify the cuase. 956

• Vomitting/nasogastic suctioning and thiazide/loop diuretic use cause volume and Cl- depletion (saline-responsive)
• Excess mineralocorticoid activity (e.g. primary hyperaldosteronism, cushing disease, ectopic ACTH production) as well as Barrter/Gitelman cause high urine chloride (saline-unresponsive)

Question 204

Presentation and predisposing conditions for central retinal artery occlusion (CRAO)

Answer 204

Sudden, painless, and permanent monocular blindness; fundoscopic exam shows pale retina and chery-red macula (macula has seperate blood supply from choroid artery, while rest of retina is supplied by central retinal artery).

CRA is a branch of the opthalamic artery, which arises from the internal carotid artery. Embolism is the MCC of CRAO. Predisposing conditions include AFib and carotid artery stenosis. 360

Question 205

What is the immediate source of nitrogen for urea in the urea cycle?

Answer 205

Urea’s nitrogen is derived from NH3 and aspartate in the urea cycle. CPS1 is the rate-limiting enzyme in the urea cycle and is activated by NAG (produced from glutamate and acetyl CoA in a reaction activated by arginine) –> produces carbamoyl phosphate within the mitochondria, which combines with ornithine to produce citrulline.

Question 206

Amino acids with 3 titratable protons include…

Answer 206

Histidine, arginine, lysine, aspartic acid, glutamic acid, cysteine and tyrosine. 2121

Question 207

Describe how long-standign ulcerative colitis-associated colorectal carcinomas differ from sporadic colorectal carcinomas

Answer 207

The duration and extent of colitis are the most significant risk factors. Unlike sporadic colorectal carcinomas, colitis-associated carcinomas are more likely to arise from non-polypoid dysplastic lesions, be multifocal in nature, develop early p53 mutations and late APC gene mutations **(opposite that of sporadic disease), and be of a higher grade. 411

Question 208

Describe the regulation of insulin secretion from pancreatic beta cells

Answer 208

• Glucose enters beta cells by faciltated diffusion using GLUT-2 –> oxidative metabolism through glycolysis –> CAC, which generates ATP
• High ATP/ADP ratio causes closure of K+ ATP channels, which are responsible for outward movement of K+ (closure occurs when ATP binds to regulatory subunit of KATP channel) –> depolarization
• Opening of voltage-dependent calcium channels –> insulin release

Defects of the KATP channel gene can result in T2DM. Sulfonylureas work by binding to regulatory subunits of KATP channels, causing them to close. 1009

Question 209

What increases the ESR

Answer 209

IL-1, IL-6 and TNF-alpha mediate systemic inflammatory response and stimulate hepatic secretion of acute-phase proteins (e.g. fibrinogen). High levels of circulatign fibrinogen increase ESR, which is a nonspecific marker of inflammation. 1801

Question 210

Distinguish between slow twich (Type I) and fast twitch (Type II) fiber types

Answer 210

Type I: red muscle fibers that generate low-level sustained force (e.g. postural maintenance). Fxn via aerobic metabolism, meaning they have high myoglobin (oxygen storage) and mitochondrial (aerobic respiration) concentrations. Include postural skeletal muscles such as the soleus and paraspinal muscles.

Type II: generate rapid forceful pulses of movement. Derive ATP energy through anaerobic glycogenolysis and subsequent glycolysis. 1858

Question 211

Distinguish benzos based on duration of action

Answer 211

Short (<10h): alprazolam, triazolam, oxazepam

Medium (10-20h): estrazolam, lorazepam, temazepam

Long (days): chlordiazepoxide, chlorazepate, diazepam, flurazepam

* Long acting benzos cause more severe drowsiness than short-acting ones. However, long-acting benzos are far less likely to cause depedence. 348

Question 212

What is the antibiotic of choice for treating lung abscesses?

Answer 212

**Clindamycin: **MOA simmiar to macrolides in binding to 50S RSU and disrupting protein synthesis. Alcoholics are more likely than the general population to develop pulmonary infections and abscesses (look for presence of air-fluid levels) involving a combination of anaerobic and aerobic bacteria. 1446

Question 213

After 12-18h of fasting, what is the principal source of blood glucose?

Answer 213

Gluconeogenesis:** pyruvate is first converted tooxaloacetatethrough biotin-dependent carboxylation by the enzyme pyruvate carboxylase in the mitochondria. Oxaloacetate is then converted tophosphoenolypyruvate** by phosphoenolpyruvate carboxykinase (PEPK). The other two enzymes differening enzymes in gluconeogensis are fructose 1,6-bisphosphatase (bypassing phosphofructokinase) and glucose-6-phosphtase (bypass hexokinase). 997

Question 214

Meningococcal pilli (fimbriae) are important for bacterial attachment to what?

Answer 214

Epithelial surfaces –> invade the epithelium and gain access to vasculature where they can spread hematogenously. Antibodies that successfuly impair the pili would inhibit pilus-mediated attachment of the meningococcus to the mucosal epithelium of the nasopharynx, preventing colonization and subsequent invasion. 1005

Question 215

What are quick clinical tests to assess attention and concentration?

Answer 215

Counting down from 100 by intervals of 3 or 7, reciting the months of the year in reverse order, and spelling “world” backwards. 8295

Question 216

What are the causes of necrotizing fasciitis

Answer 216

Strep pyogenes (Gram+ cocci that is coagulase negative, catalase negative, and pyrrolidonyl arylamidase [PYR] positive), Staph aureus, Clostridium perfringens

Sudden onset of severe pain (out of proportion to exam findings) and swelling at a site of trauma or recent surgery. Systemic symptoms (e.g. fever, hypotension –> septic shock). 8857

Question 217

What germ cell line do prolactinomas develop from?

Answer 217

Develop from lactotroph cells in the anterior pituitary, which is derived from surface ectoderm. 8702

Question 218

Describe the 3 main causes of HIV-associated esophagitis

Answer 218

All cause dysphagia and/or odynophagia. 283

• Candida: Endoscopic shows patches of adherent, grey/white pseudomembranes on erythematous mucosa. Microscopic shows yeast cells and pseudohyphae that invade mucosal cells.
• HSV-1: Endoscopic shows small vesicles that evolve into typical “punched out” ulcers. Microscopic shows eosinophilic intranuclear inclusions (Cowdry type A) in multinuclear squmous cells at hte margins of ulcers.
• CMV: Endoscopic shows linear ulceration. Microscopic shows both intranuclear and cytoplasmic inclusions

Question 219

Serum of a patient with Rheumatoid arthritis is most likely to contain

Answer 219

Autoimmune disease triggered by an unknown antigen. Cartilage components serve as autoantigens that activate CD4+ T cells, which in turn stimulate B-cells to secrete rheumatoid factor, an IgM antibody specific for the Fc component of self IgG. Rheumatoid factor binds IgG and forms immune complexes that circulate in the serum. Deposition of IC on the synovium and cartilage activates complement in those locations and contributes to chronic inflammation. 754

Question 220

What is the primary defect in Ehlers-Danlos Syndrome?

Answer 220

Caused by mutations affecting the collagen genes or enzymes involved in collagen synthesis, such as lysyl-hydroxylase or procollagen peptidase. In the case of procollgen peptidase deficiency, impaired cleavage of procollagen N- and C-termini causes the formation of more soluble collagen that does not properly corsslink with other collagen molecules –> joint laxity, loose skin, easy brusiability. 1246

Question 221

What would cause a rightward shift of the “ventricular filliing” porition of the pressure-volume loop?

Answer 221

Increased ventricular preload (i.e. a larger than normal volume is being placed into the ventricle during diastole). This can occur during any state of fluid overload: renal failure, CHF, or after infusion of IV fluids. 1511

Question 222

How can you determine the cuase of hypoxemia?

Answer 222

By using the alveolar-arterial oxygen gradient (A-a gradient); normally the A-a gradient doesn’t exceed 10-15mmHg. P_aO₂ is the partial pressure of oxygen in arterial blood; it is determined with an arterial blood gas analysis (usually >92 mmHg). P_AO₂ is the partial pressure of oxygen in alveolar air and is calculated using the aveolar gas equation (usually 100 mmHg).

P_AO₂ = 150 - (P_aCO₂ / 0.8)

1526

Question 223

What is responsible for the rapid decrease in cytoplasmic calcium level immediately preceding relaxation of cardiac muscle

Answer 223

Calcium efflux prior to myocyte relaxation is accomplished through the use of Ca²⁺-ATPase and Na⁺/Ca²⁺ exchange mechanisms. The Ca²⁺-ATPase uses active transport to sequester calcium within the SR and re-establish the ion gradient. The sarcolemmal Na⁺/Ca²⁺ transmembrane protein does not require ATP and accepts 3 extracellular Na⁺ in exchange for 1 intracellular Ca²⁺ ion. 1931

Question 224

What is a bilaterally symmetric structure that lies in close association to the vertebral body and vertebral transverse process?

Answer 224

Psoas muscle: originates from teh anterior surface of the transverse processes and lateral surface of correspondign vertebral bodies T12-L5. Acts primarily to flex the thigh at the hip. Contributes somewhat to lateral rotation and abduction of thigh as well. 1885

Question 225

What can you measure to diagnose thiamine deficency?

Answer 225

Chronic thiamine (B1) deficeincy leads to diminished ability of cerebral cells to utilize glucose. The mechanism is decrease function of the enzymes that use vitmain B1 as a cofactor (pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, and transketolase). An increase in erythrocyte transketolase levels after thiamine infusion is diagnostic for thiamine deficeincy. 598

Question 226

What is insulins MOA

Answer 226

Acts via tyrosine kinase second messenger system to stimulate synthesis of glycogen, proteins, FAs, and nucleic acids. Tyrosine kinase leads to activation of protein phosphatase within cells, which dephopshorylates glycogen synthase thereby activing that protein and promoting glycogen synthesis. Protein phosphotase also dephosphorylates fructose 1,6-bisphosphate thereby inacting that enzyme and inhibting gluconeogenesis. 1121

Question 227

What is the MCCs of death in patients with TCA (e.g. amitriptyline) overdose?

Answer 227

Refractory hypotension and cardiac arrhythmias. Inhibition of fast Na+ channels in cardiac myocytes (and His-Purkinje system) is thought to be the major underlying cellular event. Fluid resuscitation with normal saline and hypertonic sodium bicarbonate administration is crucial. 574

Question 228

Describe familial chylomicronemia syndrome (type 1 hyperlipoproteinemia)

Answer 228

AR d/t lipoprotein lipase deficeincy; without sufficient LPL activity, the body is unable to clear dietary lipid loads d/t defective hydrolysis of serum TGs (especially chylomicrons). Presents in childhood with recurrent episodes of acute pancreatitis. 782

Question 229

What are teh most effective agents for the treatment of hypertriglyceridemia

Answer 229

Fibrates, which work by activating peroxisome proliferator-activated receptor alpha (PPAR-a) which increases LPL activity. Since these meds decrease triglycerides, they will decrease the risk of acute pancreatitis! 166

Question 230

MOA of Thionamides

Answer 230

Include methimazole and propylthiouracil; act as antithyroid meds by decreasing the formation of thyroid hormones via inhibiton of the enzyme thyroid peroxidase (responsible for organification and coupling). PTU also decreases peripheral conversion of T4 to T3. 626

Question 231

How can patients with PCOS who desire fertility be treated?

Answer 231

Clomiphene: estrogen receptor modulator that decreases negative feedback inhibition on the hypothalamus by circulating estrogen and thereby increases gonadotropin production and ovulation. 2094

Sx: persistently elevated estrogen, androgen, and LH levels resulting in hyperandrogenism, chronic anovulation, oligomenorrhea, and multiple ovarian cysts. Theca cell hyperplasia can result in excess androgen production. Obesity, insulin resistance, and dyslipidemia –> increased risk of diabetes and CVD.

Question 232

What are the first microscopic changes of ischemic stroke

Answer 232

Inadequate blood supply to brain leads to ischemic stroke; MCC is arterial thrombosis or embolism. First microscopic changes occur 12-24h after cessation of blood supply and are described as “red neurons” (eosinophilic cytoplasm, pyknotic nuclei, loss of Nissl substance). 19

Question 233

What is the agent of choice for prevention and treatment of post-myocardial infarction arrythmias?

Answer 233

Lidocaine is a class IB antiarrhythmic agent which specifically binds rapidly depolarizing and depolarized cells. Ischemic myocardium is depolarized tissue; this is why lidocaine is specific for ischemic tissue and is the agent of choice for prevention and treatment of post-MI arrythmias. Amiodarone has replaced lidocaine in mangement of Vtach. 900