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Clomiphene citrate, follicle-stimulating hormone, and menopausal gonadotropins are administered to a 32-year-old woman to induce folliculogenesis for an in vitro fertilization procedure. The oocytes within responding antral follicles reinitiate meiotic development as they are released from which of the following stages of meiotic arrest?
A ) 1st meiotic prophase
B ) 1st meiotic metaphase
C ) 1st meiotic telophase
D ) 2nd meiotic prophase
E ) 2nd meiotic metaphase
F ) 2nd meiotic telophase
Which of the following is the most likely explanation for the emergence of HIV variants resistant to antiviral drugs?
A ) CD4 is expressed on many cells
B ) HIV can bind many co-receptors
C ) HIV reverse transcriptase is error prone
D ) Nef is capable of decreasing cell-surface expression of many proteins
E ) Rev efficiently exports viral mRNAs from the nucleus
A 20-year-old man is brought to the emergency department by a friend because of confusion, abdominal pain, and diarrhea for 4 hours. The symptoms began during a party. The friend says that the patient most likely took 3,4-methylenedioxymethamphetamine (MDMA) and LSD. Current medications include paroxetine for panic disorder. His temperature is 39Â°C (102.2Â°F). Physical examination shows myoclonus and hyperreflexia. An excess of which of the following neurotransmitters in the synaptic cleft is the most likely cause of this patient's symptoms?
A ) γ-Aminobutyric acid (GABA)
B ) Dopamine
C ) Epinephrine
D ) Norepinephrine
E ) Serotonin
A 67-year-old man develops hypertension in the recovery room 1 hour after a hip replacement. He has a history of angina pectoris. The most appropriate therapy to decrease his blood pressure without causing a reflex increase in heart rate is a drug that antagonizes which of the following receptors?
A ) α1-Adrenergic
B ) α2-Adrenergic
C ) α-Adrenergic and β-adrenergic
D ) α-Adrenergic and dopaminergic
E ) β-Adrenergic and dopaminergic
A 23-year-old man with sickle cell disease is admitted to the hospital because of acute vaso-occlusive crisis and acute sickle chest syndrome. Oxygen and intravenous fluids are started, and a blood transfusion and an analgesic are administered. Five days later, leukocyte count is 6500/mm3 and a platelet count is 120,000/mm3, and he is discharged with a prescription for a drug to decrease the frequency of acute crises. Six weeks later, leukocyte count is 1800/mm3 and platelet count is 60,000/mm3. Which of the following drugs is most likely responsible for the decreased leukocyte and platelet counts in this patient?
A ) Erythropoietin
B ) Folic acid
C ) Hydroxyurea
D ) Interferon-α
E ) Meperidine
Which of the following agents inhibits both the production of interleukin-2 (IL-2) in resting T lymphocytes and the production of γ-interferon in activated T lymphocytes?
A ) Azathioprine
B ) Cisplatin
C ) Cyclophosphamide
D ) Cyclosporine
E ) Mercaptopurine
A 52-year-old man is admitted to the hospital because of an acute myocardial infarction. Coronary catheterization shows a lesion in the left anterior descending coronary artery. After a balloon angioplasty is performed, abciximab is administered. Blockade of which of the following is most likely to occur in this patient?
A ) γ-Carboxylation of clotting factors
B ) Factor Xa (activated Stuart factor) formation
C ) Fibrinogen to fibrin conversion
D ) Platelet glycoprotein IIb/IIIa receptor function
E ) Platelet thromboxane A2 production