2015.04.09

Question 1

Rough endoplasmic reticulum functions

Answer 1

protein modification, folding, and transfer.

Synthesis of secretory proteins.

Question 2

Smooth Endoplasmic Reticulum

Answer 2

Lacks surface ribosomes, and functions in lipid synthesis, carbohydrate metabolism, and detoxification of harmful substances.

Question 3

Malignant Mesothelioma

Answer 3

Neoplasm that arises from the pleura or peritoneum.

Associated with asbestos exposure.

Hemorrhagic pleural effusions and pleural thickening are characteristic.

EM = gold standard: numerous, long, slender microvilli and abundant tonofilaments.

Question 4

Prostacyclin (Prostaglandin I2)

Answer 4

Produced from prostaglandin H2 by prostacyclin synthase in vascular endothelial cells

It vasodilates, inhibits platelet aggregation, and increases vascular permeability.

Opposes thromboxane A2.

Question 5

Thromboxane A2 (TXA2)

Answer 5

Prostaglandin that enhances platelet aggregation and causes vasoconstriction.

Question 6

Meyer’s Loop

Answer 6

Contains lower fibers of the optic radiation that carry information from the lower retin (upper/superior contralateral visual field)

Question 7

Lesions in Temporal Lobe

Answer 7

Disrupt Meyer’s loop - contralateral superior quadrantanopia.

Aphasia (dominant hemisphere lesions)

Memory deficits

Seizures (complex partial and tonic-clonic)

Hallucinations (auditory, olfactory, and visual)

Question 8

Delayed-type Hypersensitivity Reactions (DTH)

Answer 8

Include: contact dermatitis, granulomatous inflammation, tuberculin skin test and Candida extract skin reaction.

Mediated by T-lymphocytes.

Antigen is taken up by dendritic cells and presented to CD4 Th1-lymphocytes on MHC Class II. Th lymphocytes secrete IFN-r which recruit macrophages, leading to monocytic infiltration of the area where the antigen is introduced.

Takes 1 -2 days following antigen exposure.

Question 9

Hypersensitivity Types

Answer 9

Type I - IgE mediated (asthma, anaphylaxis)

Type II - Antibody mediated (ABO incompatibility hemolysis)

Type III - Immune complex (PSGN)

B-lymphocytes are involved. Stimulated by IL-4 release from Th2-lymphocytes.

Question 10

Alcohol Withdrawl Syndromes

Answer 10

Symptoms: Tremors, agitation, anxiety, delirium, psychosis

Exam findings: Seizures, tachycardia, palpitations.

Question 11

Benzodiazepine Withdrawal Syndromes

Answer 11

Symptoms: Tremors, anxiety, perceptual disturbances, psychosis, insomnia

Exam findings: Seizures, tachycardia, palpitations (same as alcohol ws)

Question 12

Opioid/Heroin Withdrawal Syndromes

Answer 12

Symptoms: NV, abdominal cramping, muscle aches

Exam findings: Dilated pupils, yawning, piloerection, lacrimation, hyperactive bowel sounds

Question 13

Stimulants (Cocaine, Amphetamines) Withdrawal Syndromes

Answer 13

Symptoms: Increased appetite, hypersomnia, intense psychomotor retardation, severe depression (“crash”)

Question 14

Nictoine Withdrawal Symptoms

Answer 14

Dysphoria, irritiability, anxiety, increased appetite/weight gain.

Question 15

Generalized Anxiety Disorder

Answer 15

Excessive worry over several different issues lasting at least 6 months.

Treated with antidepressants (SSRIs - paroxetine, sertraline; buspirone, venlafaxine) and benzodiazepines (short-term use)

Question 16

HIV Entry into Cells

Answer 16

HIV viruse uses CD4 protein as primary receptor and chemokine receptor CCR5 as a coreceptor.

CD4 and CCR5 are bound by the viral outer envelope protein gp120.

Deletion of both genes that code CCR5 results in resistance to HIV infection; one gene deletion leads to delayed manifestations.

Question 17

Cricopharyngeal Muscle Dysfunction

Answer 17

Due to diminished relaxation of pharyngeal muscles during swallowing.

More force is required to move the food bolus down, thus increasing contractions which increase oropharyngeal intraluminal pressure.

Pharyngeal mucosa will herniate through muscle fibers in the zone of weakness and create a Zenker Diverticulum (false diverticulum).

Oropharyngeal dysphagia, coughing, choking, and recurrent aspiration.

Question 18

Duodenal S-cells

Answer 18

Secrete secretin in response to increasing H+ concentrations.

Increases pancreatic bicarbonate secretion.

The chloride content of pancreatic secretions decreases in proportion to bicarbonate concentration increases.

Question 19

Vasopressin (ADH)

Answer 19

V2 receptor-mediated increase in permeability to water and urea at the luminal membrane of the inner medullary collecting duct.

Question 20

Coagulopathies vs. Platelet Defects

Answer 20

Coagulopathies present with deep-tissue bleeding (joints, muscles, subcutaneous tissue).

Platelet defects present with mucocutaneous bleeding (epistaxis, petechiae).

Question 21

DNA Polymerases Proof reading activity

Answer 21

All 3 prokaryotic DNA polymerases have proof reading activity and remove mismatched nucleotides via 3’ to 5’ exonuclease activity.

DNA polymerase I has 5’ to 3’ exonuclease activity which is used to excise and replace RNA primers and damaged DNA sequences.

Question 22

Rb gene

Answer 22

Tumor suppressor gene whose protein product regulates the cell cycle at the G1-S phase transition.

Inactivation mutations are found in retinoblastomas, osteosarcomas, and cancers of the breast, lung and colon.

Question 23

RAS gene

Answer 23

Works with MAP kinase pathway to control cell proliferation.

Mutations found in follicular thyroid cancer and follicular adenomas.

Question 24

Bcl-2

Answer 24

Anti-apoptotic gene that enhances cell survivial.

Expression is upregulated in many cancer cells.

Common in follicular lymphomas.

Question 25

p53

Answer 25

Tumor suppressor gene like Rb.

Inactivating mutations seen in anaplastic thyroid cancer.

Question 26

RET proto-oncogene

Answer 26

Membrane-bound tyrosine kinase receptor involved in cell cycle regulation.

RET mutations are common in sporadic medullary thyroid cancers.

Question 27

Stages of Acute Tubular Necrosis

Answer 27

1. Initiation stage - ischemic injury to renal tubules precipitated by hemorrhage, acute MI, sepsis, surgery.
2. Maintenance stage - Decreased urine output, fluid overload, increasing creatinine/BUN, hyperkalemia. High anion gap metabolic acidosis.
3. Recovery phase: Gradual increase in urine output leading to high volume diuresis. Electrolyte abnormalities may include decreased concentrations of K, Mg, PO4, and Ca due to slowly recovering tubular function.

Question 28

Methylmalonic Acidemia (Methylmalonic aciduria)

Answer 28

Defect in isomerization reaction (methylmalonyl CoA mutase + Vitamin B12) that transforms methylmalonyl CoA to succinyl CoA, prior to succinyl CoA entering the TCA cycle.

Question 29

Lactic ACidosis in patients with septic shock

Answer 29

Tissue hypoxia results in impaired oxidative phosphorylation and 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 clearance.

Question 30

Cystic Fibrosis and Steatorrhea/Failure to Thrive

Answer 30

Due to malabsorption secondary to pancreatic insufficiency, which can be corrected by pancreatic enzyme supplementation.

Question 31

Nitroglycerin

Answer 31

Acts as a venodilator. Decreases preload which decreases myocardial oxygen demand and thereby treats angina pectoris.

Question 32

Streptococcus Bovis

Answer 32

Nonenterococcal Group D streptococci

Part of normal flora. Bacteremia or endocarditis is associated with colon cancer.

S. bovis endocarditis occur do so in patients with no preexisting valvular abnormality.

Question 33

Ethambutol

Answer 33

Effective component of the multi-agent antibiotic regimen used in the treatment of M. tuberculosis and atypical mycobacterial infections.

Side effect: optic neuritis. Decreased visual acuity, central scotoma, or color-blindness. (Reversible with discontinuation)

Question 34

Isoniazid

Answer 34

Antimycobacterial agent that specifically inhibits the synthesis of mycolic acids.

Mycolic acids are essential components of the unique mycobacterial peptidoglycan cell wall. Without mycolic acids, they lose their acid-fastness and become unable to synthesize new cell walls or multiply.

Question 35

Isoniazid and Pyridoxine (Vitamin B6)

Answer 35

Chemically similar. Isoniazid can compete with vitamin B6 in the synthesis of multiple neurotransmitters, resulting in defective end products.

Clinically manifests as peripheral neuropathy.

Vitamin B6 needed in conjunction in elderly, alcoholics, or kidney/liver dysfunction.

Question 36

Fragile X Syndrome

Answer 36

Second most common cause of genetic mental retardation in males after Down syndrome.

Dysmorphic face (long, thin, prominent forehead and jaw), large testes, large protruding ears, tooth crwoding, arched palate.

Mutation in FMR1 gene on X-chromosome.

>200 CGGG repeats leads to hypermethylation of cytosine bases and gene inactivation.

Question 37

Acanthosis Nigricans (AN)

Answer 37

Hyperkeratotic, hyperpigmented plaques with a classic “velvety” texture in flexural areas.

Skin tags (acrochordons) are pedunculated outgrowths of normal skin that are commonly present.

Associated with insulin-resistant states (diabetes mellitus, acromegaly, obesity) and GI malignancies.