06-09-2006, 03:07 PM
1. Which of the following most affects expression of specific cellular RNAs in the fast-growing liver cells of an infant?
A. Mitochondrial proteins
B. Nuclear transcription factors
C. Peroxisomal proteins
D. Ribosomes
E. Vitamins
2. Oxidation of which of the following compounds requires carnitine?
A. Acetoacetate
B. Ethanol
C. Oxaloacetate
D. Palmitate
E. Pyruvate
3. A newborn with phenylketonuria is started on a strict phenylalanine-restricted diet. Which of the following amino acids must be supplemented to avoid negative nitrogen balance?
A. Arginine
B. Isoleucine
C. Lysine
D. Tryptophan
E. Tyrosine
4. The graph shows changes in the volume of an erythrocyte after it is added to an NaCl solution. Which of the following is the most likely concentration (in mM) of NaCl in the solution?
A. 75
B. 150
C. 300
D. 500
E. 1500
5. Which of the following is vascularized by the artery of the foregut but is not itself a foregut derivative?
A. Duodenum
B. Gallbladder
C. Liver
D. Pancreas
E. Spleen
6. A 75-year-old woman with metastatic small cell carcinoma of the lung is brought to the emergency department after collapsing. On arrival, she is pale, sweating, and lethargic. Her temperature is 37.2°C (99°F), pulse is 130/min and weak, respirations are 25/min, and blood pressure is 90/60 mm Hg. Breath sounds are decreased bilaterally. An x-ray of the chest shows a tumor mass in the hilar area and an additional radiodensity in the left lower lobe of the lung. She dies within a few hours despite supportive care and antimicrobial therapy. Cultures of blood collected at the time of admission grow Klebsiella pneumoniae. Which of the following is the most likely mediator released from macrophages that initiated the process that led to her death?
A. Alpha-1-Antitrypsin
B. Complement C3b
C. C-reactive protein
D. Factor XII (Hageman factor)
E. Interferon-gamma
F. Interleukin-8 (IL-8)
G. Platelet-activating factor
H. Tumor necrosis factor
I. Interferon-alpha
7. A 45-year-old woman has the recent onset of shortness of breath. She has had a cough and a 14-kg (30-lb) weight loss over the past 6 months. An x-ray of the chest shows a 4-cm mass in the middle lobe of the right lung. Examination of tissue obtained on biopsy shows a small cell, neuroendocrine lung carcinoma. Which of the following abnormalities is most likely to develop in this patient?
A. Hypocalcemia
B. Hypoglycemia
C. Hyponatremia
D. Polycythemia
8. A 45-year-old woman has increasing dyspnea and fatigue. She is pale. Hemoglobin concentration is 7.5 g/dL, leukocyte count is 4500/mm3, and platelet count is 89,000/mm3. A peripheral blood smear is shown. Based on these findings, which of the following additional findings is most likely?
A. Antiparietal cell antibodies in serum
B. Decreased serum concentration of iron
C. Increased hemoglobin A2 on hemoglobin electrophoresis
D. Increased osmotic fragility of the erythrocytes
E. Positive direct antiglobulin test
9. The epidermal growth factor receptor and the platelet-derived growth factor receptor are both classified as which of the following?
A. Calcium-dependent protein kinases
B. cGMP receptors
C. JAK/STAT kinases
D. Receptor guanylyl cyclases
E. Receptor serine/threonine kinases
F. Receptor tyrosine kinases
10. A 20-year-old woman ingests 100 tablets (500 mg per tablet) of acetaminophen in a suicide attempt; she does not lose consciousness. She seems healthy for the next 2 days and then develops massive hepatic failure. Which of the following is the primary mechanism responsible for the hepatic failure?
A. Depletion of intracellular reduced glutathione
B. Formation of excessive superoxide in the hepatocytes
C. Inhibition of adenylyl cyclase
D. Inhibition of ATPase-dependent transport
E. Stimulation of cytochrome oxidase
11. A 27-year-old woman who is seropositive for HIV is taking two different reverse transcriptase inhibitors and a protease inhibitor. Which of the following best explains the beneficial action of the protease inhibitor in this combination?
A. Antagonizing the stimulation of DNA replication by the reverse transcriptase inhibitors
B. Blocking the cleavage step in active virion production
C. Disrupting the catalytic site on reverse transcriptase synthetase
D. Inhibiting the protein that permits DNA chain elongation
E. Preventing the proteolytic cleavage of reverse transcriptase
12. Bacterial strain X is resistant to ampicillin and sensitive to gentamicin. Bacterial strain Y is resistant to gentamicin and sensitive to ampicillin. Bacterial strains X and Y are grown in mixed culture in medium without antibiotics, then the culture is plated on medium containing both ampicillin and gentamicin. Bacterial colonies grow on the plates. In a second experiment, DNase is added to the mixed culture medium. When this mixed culture is plated on medium containing both antibiotics, no colonies grow. Assuming that bacterial cells are impermeable to DNase, which of the following processes best explains these observations?
A. Conjugation
B. Mutation
C. Transduction
D. Transformation
E. Transposition
13. An unimmunized 1-year-old boy from Africa has had photophobia and nuchal rigidity for 2 days. Subsequently, he develops flaccid paralysis of the right lower extremity. Stool culture grows a pathogenic virus. Which of the following characterizes the genetic information of the infectious agent responsible for his illness?
A. Single-stranded DNA
B. Double-stranded DNA
C. Single-stranded RNA
D. Double-stranded RNA
E. Neither RNA nor DNA
F. Protein
14. Which of the following contaminants will be removed from a fluid passed through a 0.45 μ filter?
A. Herpes simplex virus
B. HIV protease
C. Lipopolysaccharide
D. Mycoplasma hominis
E. Staphylococcus aureus
15. Two inbred mouse strains, A and B, express different alleles only at a minor histocompatibility locus on the Y chromosome. Which of the following mice would accept a skin graft from a male (AxB)F1 mouse with a strain A father and a strain B mother?
A. (AxB)F1 female (A mother, B father)
B. (AxB)F1 female (A father, B mother)
C. (AxB)F1 male (A mother, B father)
D. (AxB)F1 male (A father, B mother)
16. If 1 person in 10,000 with a negative PPD skin test has active tuberculosis (TB), and 1 person in 100 with a positive PPD skin test has active TB, which of the following is the estimated relative risk of active tuberculosis in persons with a positive PPD skin test?
A. 1
B. 9.9
C. 100
D. 1000
E. 10,000
17. Two experimental drugs, drug X and drug Y, are being evaluated for treatment of congestive heart failure. Patients receiving drug X have a cardiac index of 2.5 L/m2 with a 95% confidence interval of 1.5 to 3.5. Patients receiving drug Y have a cardiac index of 1.7 L/m2 with a 95% confidence interval of 0.7 to 2.7. A test of the significance of difference shows a p-value of 0.1. Which of the following is the likelihood that the difference in mean cardiac index of patients receiving drug X and drug Y is due to chance?
A. 0%
B. 2.5%
C. 5%
D. 7.5%
E. 10%
F. 66.7%
G. 95%
18. An 85-year-old woman has a malignant neoplasm in the wall of the sigmoid colon. To which of the following groups of lymph nodes is the neoplasm most likely to metastasize initially?
A. Celiac
B. Inferior mesenteric
C. Inguinal
D. Internal iliac
E. Lateral lumbar (aortic)
F. Superior mesenteric
19. A 16-year-old girl is brought to the physician because of sore throat, fever, and malaise. She has cervical lymphadenopathy and a tender, slightly enlarged spleen. Laboratory studies show:
Hemoglobin 14.4 g/dL
Hematocrit 33.2%
Leukocyte count 12,000/ mm3
A. A peripheral blood smear is shown. Which of the following is the most likely diagnosis?
B. Acute lymphocytic leukemia
C. Acute myelogenous leukemia
D. Bacterial sepsis
E. Chronic lymphocytic leukemia
F. Infectious mononucleosis
20. A 59-year-old man comes to the emergency department because of fever and shaking chills for 24 hours. He completed a course of fluorouracil for a neoplasm 1 week ago. His temperature is 39°C (102.2°F), and blood pressure is 85/60 mm Hg. Physical examination shows no other abnormalities. His hematocrit is 30%, leukocyte count is 400/mm3, and platelet count is 100,000/mm3. Which of the following agents will most specifically complement antibiotic therapy in this patient?
A. Erythropoietin
B. Granulocyte colony-stimulating factor
C. Interleukin-1 (IL-1)
D. IL-2
E. Leucovorin
21. An acute extensive bilateral lesion in the reticular formation of the tegmentum of the midbrain is most likely to result in which of the following?
A. Insomnia
B. Intractable pain
C. Loss of consciousness
D. Narcolepsy
E. Rapid eye movements
22. Following a traumatic injury, a 25-year-old man has loss of abduction, lateral rotation, and flexion of the arm; loss of flexion at the elbow; and loss of supination of the forearm. X-rays show no fractures. A lesion of which of the following labeled structures on the diagram best explains these findings?
A. A
B. B
C. C
D. D
E. E
23. A 10-year-old boy is sent to the principal's office by his teacher. While waiting outside the office, he becomes very anxious, starts to hyperventilate, and faints. A decrease in which of the following is the most likely cause of the decrease in cerebral blood flow?
A. Arterial PCO2
B. Arterial pH
C. Arterial PO2
D. Cardiac output
E. Pulse
24. A 4366-g (9 lb 10 oz) male newborn is delivered at term. The cephalic vaginal delivery was difficult and complicated by severe depression of the right shoulder. An MRI shows avulsion of a single root of the brachial plexus. The ventral ramus of which of the following spinal nerves has most likely been injured?
A. C5
B. C6
C. C7
D. C8
E. T1
25. A normal brain is shown. An 80% loss of neurons in the structure labeled X will create a state of disinhibition in which of the following areas of the brain?
A. Basal forebrain
B. Dentate nucleus
C. Hippocampus
D. Hypothalamus
E. Striatum
26. A 45-year-old homeless man is brought to the emergency department 1 hour after the sudden onset of blindness. He has alcoholism and drank approximately 2 liters of a substance he thought was ethanol. Physical examination shows sweet-smelling breath. Serum toxicology screening is positive for methanol. Which of the following substances is most likely to be the cause of the blindness?
A. Acetone
B. Ethanol
C. Formic acid
D. Isopropanol
E. Xylene
27. A 78-year-old man who lives in a nursing home has a fever and muscle rigidity after receiving a drug for treatment of a psychotic episode. Serum creatine kinase activity is increased. Which of the following drugs is the most likely cause of these adverse effects?
A. Clozapine
B. Diazepam
C. Haloperidol
D. Lithium carbonate
E. Olanzapine
F. Risperidone
28. Viremia is an essential feature of which of the following disorders?
A. Bronchiolitis caused by respiratory syncytial virus
B. Herpes zoster infection
C. Primary genital herpes infection
D. Primary varicella infection
E. Rhinovirus infection
29. Which of the following actions is most likely to be severely impaired if a nerve is injured by a fracture at site X in the x-ray?
A. Dorsiflexion of the foot
B. Extension of the leg
C. Flexion of the leg
D. Inversion of the foot
E. Plantar flexion of the foot
30. Two brothers, aged 26 and 28 years, have similar disorders. Both of their histories include blue sclerae at birth, joint hypermobility, easy bruising, and moderate bilateral hearing loss. Each has had about 20 fractures since birth, all of which have healed rapidly and without deformity. Their symptoms are most likely caused by a defect in the synthesis of which of the following compounds?
A. Hydroxyapatite
B. Hydroxyproline
C. Procollagen
D. Prothrombin
31. A 66-year-old woman has fluid in the pleural cavity. To obtain a sample of fluid, a needle is inserted at the midaxillary line in the sixth intercostal space. After piercing the skin, which of the following is the correct order (superficial to deep) of structures that will be pierced in order to enter the pleural cavity?
A. Costal pleura, visceral pleura
B. Intercostal muscles, costal pleura
C. Intercostal muscles, mediastinal pleura
D. Intercostal muscles, visceral pleura
E. Visceral pleura, costal pleura
32. A 28-year-old man comes to the physician because of a 1-month history of severe shortness of breath with exertion. He has smoked 1 pack of cigarettes daily for 10 years. His father and his uncle died in their 40s of lung disease. The lungs are hyperresonant to percussion. Breath sounds are diffusely decreased. Pulse oximetry on room air while the patient is at rest shows a normal oxygen saturation that decreases to less than 86% when the patient climbs one flight of stairs. Pulmonary function tests show an FEV1 of 1.0 L/min (25% of predicted) and an FVC of 3.3 L/min (70% of predicted). Five years ago, his lung function was normal. Histologic examination of tissue obtained on biopsy is most likely to show which of the following?
A. Bronchopulmonary dysplasia
B. Chronic bronchitis
C. Interstitial fibrosis
D. Obliterative bronchiolitis
E. Panacinar emphysema
33. An 8-year-old boy is brought to the physician by his parents because of episodes of shortness of breath, nonproductive cough, and wheezing that last 5 to 10 minutes and occur more frequently during the winter. The incidence and severity of these episodes is most likely to be decreased by selective inhibition of which of the following enzymes?
A. Cyclooxygenase-1
B. Cyclooxygenase-2
C. Epoxygenase
D. 5-Lipoxygenase
E. Phospholipase A1
F. Thromboxane synthase
34. Under control conditions, flow through a blood vessel is 100 mL/min under a pressure gradient of 100 mm Hg. The diameter of the vessel is increased twofold and the pressure gradient is maintained at 100 mm Hg. Which of the following is the current flow (in mL/min)?
A. 100
B. 200
C. 400
D. 800
E. 1600
35. A 17-year-old girl comes to the physician because of shortness of breath. A systolic murmur is heard best in the left fifth intercostal space in the midclavicular line. Which of the following valvular abnormalities is the most likely cause of the murmur?
A. Aortic insufficiency
B. Aortic stenosis
C. Mitral insufficiency
D. Mitral stenosis
E. Pulmonary insufficiency
F. Pulmonary stenosis
G. Tricuspid insufficiency
H. Tricuspid stenosis
36. A 61-year-old woman with a long history of poorly controlled hypertension suddenly has excruciating anterior upper sternal pain radiating to the neck and back. On admission to the emergency department, her blood pressure is 210/110 mm Hg. Fifteen minutes later, while lying down, it is 110/64 mm Hg. Transesophageal echocardiography shows aortic insufficiency, a suggestion of a double lumen of the ascending aorta, and a pericardial effusion. She dies suddenly while awaiting an operation. Which of the following is the most likely cause of death?
A. Acute hemopericardium
B. Acute myocardial infarct
C. Cerebral infarct
D. Congestive heart failure
E. Massive retroperitoneal hemorrhage
37. A 45-year-old man with increased serum LDL concentrations is treated with cholestyramine, which binds bile salts in the small intestine. The most likely result is prevention of which of the following?
A. Conversion of IDLs to LDLs in the bloodstream
B. Formation of chylomicrons in intestinal epithelial cells
C. Resorption and redistribution of bile salts to the liver
D. Synthesis of cholesterol in the liver
38. During a physiological study of pancreatic function, a researcher studies a fasted experimental animal with a chronic pancreatic fistula. The researcher administers a variety of substances intravenously to mimic postprandial levels. The volume and composition of pancreatic secretions are then measured. The results from two such experiments are shown in the graph. Which of the following substances was most likely administered to obtain the results shown?
A. Acetylcholine
B. Cholecystokinin
C. Gastrin-releasing peptide
D. Secretin
E. Somatostatin
F. Vasoactive intestinal polypeptide
39. A 32-year-old man has dysphagia and odynophagia after ingesting a drain cleaner containing sodium hydroxide pellets. Which of the following is the most likely associated finding 3 months later?
A. Aspiration pneumonia
B. Blindness
C. Esophageal stricture
D. Gastric perforation
E. Hemolytic anemia
F. Renal failure
G. Systemic acid-base imbalance
40. A 49-year-old man comes to the physician because of fatigue, lightheadedness on standing or sitting up rapidly, and dark-colored stools for the past 4 days. He moved to the USA from southeastern Asia 2 years ago. His history includes chronic hepatitis B infection. Examination shows pale mucous membranes, an enlarged liver, a prominent periumbilical venous pattern, and nonbleeding internal hemorrhoids. Hemoglobin concentration is 7.8 g/dL. Upper endoscopy shows circumferentially prominent tortuous veins with an adherent clot at the gastroesophageal junction. Which of the following mechanisms best explains the blood loss in this patient?
A. Acute inflammation of the gastroesophageal mucosa
B. Arteriovenous fistulae at the gastroesophageal junction
C. Hepatic artery obstruction with increased celiac pressure
D. Increased flow through collateral hepatic veins
E. Increased pressure in submucosal esophageal veins
41. During normal micturition, pressure within the bladder increases in response to which of the following changes?
A. Contraction of the external sphincter
B. Parasympathetic outflow from the sacral spinal cord
C. Somatic efferent outflow from the sacral spinal cord
D. Sympathetic outflow from the lumbar spinal cord
E. Voluntary relaxation of the external sphincter
42. A 45-year-old woman comes to the physician because of a mass in her left flank. Two months ago she had a hysterectomy for cervical cancer that had invaded beyond the serosa of the uterus. The mass is largely comprised of a markedly dilated renal pelvic and calyceal system. Which of the following is the most likely diagnosis?
A. Hydronephrosis
B. Hypernephroma
C. Nephrosclerosis
D. Pyelonephrosis
E. Vesicoureteral reflux
43. A 17-year-old girl with chronic renal insufficiency undergoes a unilateral nephrectomy. A photograph of the resected kidney is shown. Which of the following is the most likely cause of this patient's renal insufficiency?
A. Cervical cancer
B. Disseminated intravascular coagulation
C. Endometriosis
D. Essential hypertension
E. Fibromuscular dysplasia of the renal artery
F. IgA nephropathy
G. Poststreptococcal glomerulonephritis
H. Preeclampsia
I. Type 1 diabetes mellitus
J. Vesicoureteral reflux
44. A 35-year-old man comes to the physician because of a 3-week history of pain with urination and blood in his urine at the end of urination. He is a fishery consultant with the Peace Corps and returned to the USA 1 month ago following a 2-year assignment in Africa. He frequently came in contact with lake water while in Africa, ate locally prepared foods, and was sexually active with two women while using condoms consistently. Physical examination shows no abnormalities. Ultrasonography of the urinary tract shows bilateral mild hydronephrosis and nodules in the bladder. Exposure to which of the following types of organisms is the most likely cause of this patient's condition?
A. Bacteria
B. Fungus
C. Mycobacterium
D. Parasite
E. Virus
45. A 23-year-old woman comes to the physician because of heavy watery vaginal discharge, itching, and burning for 2 weeks. She is sexually active with one partner. Speculum examination shows profuse, foamy, yellow discharge. A wet mount preparation shows motile organisms and numerous leukocytes. Which of the following is the most likely diagnosis?
A. Bacterial vaginosis
B. Chancroid
C. Chlamydia trachomatis infection
D. Trichomoniasis
46. A previously healthy 29-year-old woman has the sudden onset of dyspnea and becomes unresponsive after the vaginal delivery of a male newborn who weighs 3570 g (7 lb 14 oz). Pregnancy was uneventful. Oxytocin was administered during labor to augment contractions. Examination shows no pulse and no spontaneous respirations. Which of the following is the most likely diagnosis?
A. Acute myocardial infarction
B. Amniotic fluid embolism
C. Eclampsia
D. Hemorrhagic cerebral stroke
E. Oxytocin overdose
47. A 22-year-old man with a nonseminomatous germ cell tumor is scheduled to undergo a course of chemotherapy with ifosfamide, carboplatin, and etoposide. Mesna should be added to his regimen to prevent which of the following potential toxic effects of the antineoplastic drugs?
A. Cardiomyopathy
B. Drug-induced leukemia
C. Hemorrhagic cystitis
D. Hyperglycemia
E. Pulmonary fibrosis
48. A 28-year-old woman is brought to the emergency department after being involved in an automobile collision. She has lost an estimated 400 mL of blood. Plasma renin activity is five times greater than the reference range. The most likely explanation for this increase is an increase in which of the following?
A. Arterial pressure
B. Renal sympathetic nerve activity
C. Serum angiotensin II concentration
D. Serum atrial natriuretic peptide concentration
E. Sodium delivery to the macula densa
49. A 22-year-old man comes to the physician's office because of fatigue, blurred vision, and increased thirst for the past 2 months. During this time, he has awakened several times a night to urinate, and urinates 8 to 10 times daily. He takes no medications. Serum sodium concentration is 160 mEq/L and urine osmolality is 165 mOsmol/kg H2O. Which of the following is the most likely diagnosis?
A. Acute renal failure
B. Aldosterone-secreting neoplasm
C. Congestive heart failure
D. Diabetes insipidus
E. Syndrome of inappropriate ADH (vasopressin)
50. A 60-year-old woman develops anemia several years after a subtotal gastrectomy. Which of the following is the most likely finding on a peripheral blood smear?
A. Basophilic stippling
B. Helmet cells
C. Macrocytosis of erythrocytes
D. Microcytosis of erythrocytes
E. Reticulocytosis
A. Mitochondrial proteins
B. Nuclear transcription factors
C. Peroxisomal proteins
D. Ribosomes
E. Vitamins
2. Oxidation of which of the following compounds requires carnitine?
A. Acetoacetate
B. Ethanol
C. Oxaloacetate
D. Palmitate
E. Pyruvate
3. A newborn with phenylketonuria is started on a strict phenylalanine-restricted diet. Which of the following amino acids must be supplemented to avoid negative nitrogen balance?
A. Arginine
B. Isoleucine
C. Lysine
D. Tryptophan
E. Tyrosine
4. The graph shows changes in the volume of an erythrocyte after it is added to an NaCl solution. Which of the following is the most likely concentration (in mM) of NaCl in the solution?
A. 75
B. 150
C. 300
D. 500
E. 1500
5. Which of the following is vascularized by the artery of the foregut but is not itself a foregut derivative?
A. Duodenum
B. Gallbladder
C. Liver
D. Pancreas
E. Spleen
6. A 75-year-old woman with metastatic small cell carcinoma of the lung is brought to the emergency department after collapsing. On arrival, she is pale, sweating, and lethargic. Her temperature is 37.2°C (99°F), pulse is 130/min and weak, respirations are 25/min, and blood pressure is 90/60 mm Hg. Breath sounds are decreased bilaterally. An x-ray of the chest shows a tumor mass in the hilar area and an additional radiodensity in the left lower lobe of the lung. She dies within a few hours despite supportive care and antimicrobial therapy. Cultures of blood collected at the time of admission grow Klebsiella pneumoniae. Which of the following is the most likely mediator released from macrophages that initiated the process that led to her death?
A. Alpha-1-Antitrypsin
B. Complement C3b
C. C-reactive protein
D. Factor XII (Hageman factor)
E. Interferon-gamma
F. Interleukin-8 (IL-8)
G. Platelet-activating factor
H. Tumor necrosis factor
I. Interferon-alpha
7. A 45-year-old woman has the recent onset of shortness of breath. She has had a cough and a 14-kg (30-lb) weight loss over the past 6 months. An x-ray of the chest shows a 4-cm mass in the middle lobe of the right lung. Examination of tissue obtained on biopsy shows a small cell, neuroendocrine lung carcinoma. Which of the following abnormalities is most likely to develop in this patient?
A. Hypocalcemia
B. Hypoglycemia
C. Hyponatremia
D. Polycythemia
8. A 45-year-old woman has increasing dyspnea and fatigue. She is pale. Hemoglobin concentration is 7.5 g/dL, leukocyte count is 4500/mm3, and platelet count is 89,000/mm3. A peripheral blood smear is shown. Based on these findings, which of the following additional findings is most likely?
A. Antiparietal cell antibodies in serum
B. Decreased serum concentration of iron
C. Increased hemoglobin A2 on hemoglobin electrophoresis
D. Increased osmotic fragility of the erythrocytes
E. Positive direct antiglobulin test
9. The epidermal growth factor receptor and the platelet-derived growth factor receptor are both classified as which of the following?
A. Calcium-dependent protein kinases
B. cGMP receptors
C. JAK/STAT kinases
D. Receptor guanylyl cyclases
E. Receptor serine/threonine kinases
F. Receptor tyrosine kinases
10. A 20-year-old woman ingests 100 tablets (500 mg per tablet) of acetaminophen in a suicide attempt; she does not lose consciousness. She seems healthy for the next 2 days and then develops massive hepatic failure. Which of the following is the primary mechanism responsible for the hepatic failure?
A. Depletion of intracellular reduced glutathione
B. Formation of excessive superoxide in the hepatocytes
C. Inhibition of adenylyl cyclase
D. Inhibition of ATPase-dependent transport
E. Stimulation of cytochrome oxidase
11. A 27-year-old woman who is seropositive for HIV is taking two different reverse transcriptase inhibitors and a protease inhibitor. Which of the following best explains the beneficial action of the protease inhibitor in this combination?
A. Antagonizing the stimulation of DNA replication by the reverse transcriptase inhibitors
B. Blocking the cleavage step in active virion production
C. Disrupting the catalytic site on reverse transcriptase synthetase
D. Inhibiting the protein that permits DNA chain elongation
E. Preventing the proteolytic cleavage of reverse transcriptase
12. Bacterial strain X is resistant to ampicillin and sensitive to gentamicin. Bacterial strain Y is resistant to gentamicin and sensitive to ampicillin. Bacterial strains X and Y are grown in mixed culture in medium without antibiotics, then the culture is plated on medium containing both ampicillin and gentamicin. Bacterial colonies grow on the plates. In a second experiment, DNase is added to the mixed culture medium. When this mixed culture is plated on medium containing both antibiotics, no colonies grow. Assuming that bacterial cells are impermeable to DNase, which of the following processes best explains these observations?
A. Conjugation
B. Mutation
C. Transduction
D. Transformation
E. Transposition
13. An unimmunized 1-year-old boy from Africa has had photophobia and nuchal rigidity for 2 days. Subsequently, he develops flaccid paralysis of the right lower extremity. Stool culture grows a pathogenic virus. Which of the following characterizes the genetic information of the infectious agent responsible for his illness?
A. Single-stranded DNA
B. Double-stranded DNA
C. Single-stranded RNA
D. Double-stranded RNA
E. Neither RNA nor DNA
F. Protein
14. Which of the following contaminants will be removed from a fluid passed through a 0.45 μ filter?
A. Herpes simplex virus
B. HIV protease
C. Lipopolysaccharide
D. Mycoplasma hominis
E. Staphylococcus aureus
15. Two inbred mouse strains, A and B, express different alleles only at a minor histocompatibility locus on the Y chromosome. Which of the following mice would accept a skin graft from a male (AxB)F1 mouse with a strain A father and a strain B mother?
A. (AxB)F1 female (A mother, B father)
B. (AxB)F1 female (A father, B mother)
C. (AxB)F1 male (A mother, B father)
D. (AxB)F1 male (A father, B mother)
16. If 1 person in 10,000 with a negative PPD skin test has active tuberculosis (TB), and 1 person in 100 with a positive PPD skin test has active TB, which of the following is the estimated relative risk of active tuberculosis in persons with a positive PPD skin test?
A. 1
B. 9.9
C. 100
D. 1000
E. 10,000
17. Two experimental drugs, drug X and drug Y, are being evaluated for treatment of congestive heart failure. Patients receiving drug X have a cardiac index of 2.5 L/m2 with a 95% confidence interval of 1.5 to 3.5. Patients receiving drug Y have a cardiac index of 1.7 L/m2 with a 95% confidence interval of 0.7 to 2.7. A test of the significance of difference shows a p-value of 0.1. Which of the following is the likelihood that the difference in mean cardiac index of patients receiving drug X and drug Y is due to chance?
A. 0%
B. 2.5%
C. 5%
D. 7.5%
E. 10%
F. 66.7%
G. 95%
18. An 85-year-old woman has a malignant neoplasm in the wall of the sigmoid colon. To which of the following groups of lymph nodes is the neoplasm most likely to metastasize initially?
A. Celiac
B. Inferior mesenteric
C. Inguinal
D. Internal iliac
E. Lateral lumbar (aortic)
F. Superior mesenteric
19. A 16-year-old girl is brought to the physician because of sore throat, fever, and malaise. She has cervical lymphadenopathy and a tender, slightly enlarged spleen. Laboratory studies show:
Hemoglobin 14.4 g/dL
Hematocrit 33.2%
Leukocyte count 12,000/ mm3
A. A peripheral blood smear is shown. Which of the following is the most likely diagnosis?
B. Acute lymphocytic leukemia
C. Acute myelogenous leukemia
D. Bacterial sepsis
E. Chronic lymphocytic leukemia
F. Infectious mononucleosis
20. A 59-year-old man comes to the emergency department because of fever and shaking chills for 24 hours. He completed a course of fluorouracil for a neoplasm 1 week ago. His temperature is 39°C (102.2°F), and blood pressure is 85/60 mm Hg. Physical examination shows no other abnormalities. His hematocrit is 30%, leukocyte count is 400/mm3, and platelet count is 100,000/mm3. Which of the following agents will most specifically complement antibiotic therapy in this patient?
A. Erythropoietin
B. Granulocyte colony-stimulating factor
C. Interleukin-1 (IL-1)
D. IL-2
E. Leucovorin
21. An acute extensive bilateral lesion in the reticular formation of the tegmentum of the midbrain is most likely to result in which of the following?
A. Insomnia
B. Intractable pain
C. Loss of consciousness
D. Narcolepsy
E. Rapid eye movements
22. Following a traumatic injury, a 25-year-old man has loss of abduction, lateral rotation, and flexion of the arm; loss of flexion at the elbow; and loss of supination of the forearm. X-rays show no fractures. A lesion of which of the following labeled structures on the diagram best explains these findings?
A. A
B. B
C. C
D. D
E. E
23. A 10-year-old boy is sent to the principal's office by his teacher. While waiting outside the office, he becomes very anxious, starts to hyperventilate, and faints. A decrease in which of the following is the most likely cause of the decrease in cerebral blood flow?
A. Arterial PCO2
B. Arterial pH
C. Arterial PO2
D. Cardiac output
E. Pulse
24. A 4366-g (9 lb 10 oz) male newborn is delivered at term. The cephalic vaginal delivery was difficult and complicated by severe depression of the right shoulder. An MRI shows avulsion of a single root of the brachial plexus. The ventral ramus of which of the following spinal nerves has most likely been injured?
A. C5
B. C6
C. C7
D. C8
E. T1
25. A normal brain is shown. An 80% loss of neurons in the structure labeled X will create a state of disinhibition in which of the following areas of the brain?
A. Basal forebrain
B. Dentate nucleus
C. Hippocampus
D. Hypothalamus
E. Striatum
26. A 45-year-old homeless man is brought to the emergency department 1 hour after the sudden onset of blindness. He has alcoholism and drank approximately 2 liters of a substance he thought was ethanol. Physical examination shows sweet-smelling breath. Serum toxicology screening is positive for methanol. Which of the following substances is most likely to be the cause of the blindness?
A. Acetone
B. Ethanol
C. Formic acid
D. Isopropanol
E. Xylene
27. A 78-year-old man who lives in a nursing home has a fever and muscle rigidity after receiving a drug for treatment of a psychotic episode. Serum creatine kinase activity is increased. Which of the following drugs is the most likely cause of these adverse effects?
A. Clozapine
B. Diazepam
C. Haloperidol
D. Lithium carbonate
E. Olanzapine
F. Risperidone
28. Viremia is an essential feature of which of the following disorders?
A. Bronchiolitis caused by respiratory syncytial virus
B. Herpes zoster infection
C. Primary genital herpes infection
D. Primary varicella infection
E. Rhinovirus infection
29. Which of the following actions is most likely to be severely impaired if a nerve is injured by a fracture at site X in the x-ray?
A. Dorsiflexion of the foot
B. Extension of the leg
C. Flexion of the leg
D. Inversion of the foot
E. Plantar flexion of the foot
30. Two brothers, aged 26 and 28 years, have similar disorders. Both of their histories include blue sclerae at birth, joint hypermobility, easy bruising, and moderate bilateral hearing loss. Each has had about 20 fractures since birth, all of which have healed rapidly and without deformity. Their symptoms are most likely caused by a defect in the synthesis of which of the following compounds?
A. Hydroxyapatite
B. Hydroxyproline
C. Procollagen
D. Prothrombin
31. A 66-year-old woman has fluid in the pleural cavity. To obtain a sample of fluid, a needle is inserted at the midaxillary line in the sixth intercostal space. After piercing the skin, which of the following is the correct order (superficial to deep) of structures that will be pierced in order to enter the pleural cavity?
A. Costal pleura, visceral pleura
B. Intercostal muscles, costal pleura
C. Intercostal muscles, mediastinal pleura
D. Intercostal muscles, visceral pleura
E. Visceral pleura, costal pleura
32. A 28-year-old man comes to the physician because of a 1-month history of severe shortness of breath with exertion. He has smoked 1 pack of cigarettes daily for 10 years. His father and his uncle died in their 40s of lung disease. The lungs are hyperresonant to percussion. Breath sounds are diffusely decreased. Pulse oximetry on room air while the patient is at rest shows a normal oxygen saturation that decreases to less than 86% when the patient climbs one flight of stairs. Pulmonary function tests show an FEV1 of 1.0 L/min (25% of predicted) and an FVC of 3.3 L/min (70% of predicted). Five years ago, his lung function was normal. Histologic examination of tissue obtained on biopsy is most likely to show which of the following?
A. Bronchopulmonary dysplasia
B. Chronic bronchitis
C. Interstitial fibrosis
D. Obliterative bronchiolitis
E. Panacinar emphysema
33. An 8-year-old boy is brought to the physician by his parents because of episodes of shortness of breath, nonproductive cough, and wheezing that last 5 to 10 minutes and occur more frequently during the winter. The incidence and severity of these episodes is most likely to be decreased by selective inhibition of which of the following enzymes?
A. Cyclooxygenase-1
B. Cyclooxygenase-2
C. Epoxygenase
D. 5-Lipoxygenase
E. Phospholipase A1
F. Thromboxane synthase
34. Under control conditions, flow through a blood vessel is 100 mL/min under a pressure gradient of 100 mm Hg. The diameter of the vessel is increased twofold and the pressure gradient is maintained at 100 mm Hg. Which of the following is the current flow (in mL/min)?
A. 100
B. 200
C. 400
D. 800
E. 1600
35. A 17-year-old girl comes to the physician because of shortness of breath. A systolic murmur is heard best in the left fifth intercostal space in the midclavicular line. Which of the following valvular abnormalities is the most likely cause of the murmur?
A. Aortic insufficiency
B. Aortic stenosis
C. Mitral insufficiency
D. Mitral stenosis
E. Pulmonary insufficiency
F. Pulmonary stenosis
G. Tricuspid insufficiency
H. Tricuspid stenosis
36. A 61-year-old woman with a long history of poorly controlled hypertension suddenly has excruciating anterior upper sternal pain radiating to the neck and back. On admission to the emergency department, her blood pressure is 210/110 mm Hg. Fifteen minutes later, while lying down, it is 110/64 mm Hg. Transesophageal echocardiography shows aortic insufficiency, a suggestion of a double lumen of the ascending aorta, and a pericardial effusion. She dies suddenly while awaiting an operation. Which of the following is the most likely cause of death?
A. Acute hemopericardium
B. Acute myocardial infarct
C. Cerebral infarct
D. Congestive heart failure
E. Massive retroperitoneal hemorrhage
37. A 45-year-old man with increased serum LDL concentrations is treated with cholestyramine, which binds bile salts in the small intestine. The most likely result is prevention of which of the following?
A. Conversion of IDLs to LDLs in the bloodstream
B. Formation of chylomicrons in intestinal epithelial cells
C. Resorption and redistribution of bile salts to the liver
D. Synthesis of cholesterol in the liver
38. During a physiological study of pancreatic function, a researcher studies a fasted experimental animal with a chronic pancreatic fistula. The researcher administers a variety of substances intravenously to mimic postprandial levels. The volume and composition of pancreatic secretions are then measured. The results from two such experiments are shown in the graph. Which of the following substances was most likely administered to obtain the results shown?
A. Acetylcholine
B. Cholecystokinin
C. Gastrin-releasing peptide
D. Secretin
E. Somatostatin
F. Vasoactive intestinal polypeptide
39. A 32-year-old man has dysphagia and odynophagia after ingesting a drain cleaner containing sodium hydroxide pellets. Which of the following is the most likely associated finding 3 months later?
A. Aspiration pneumonia
B. Blindness
C. Esophageal stricture
D. Gastric perforation
E. Hemolytic anemia
F. Renal failure
G. Systemic acid-base imbalance
40. A 49-year-old man comes to the physician because of fatigue, lightheadedness on standing or sitting up rapidly, and dark-colored stools for the past 4 days. He moved to the USA from southeastern Asia 2 years ago. His history includes chronic hepatitis B infection. Examination shows pale mucous membranes, an enlarged liver, a prominent periumbilical venous pattern, and nonbleeding internal hemorrhoids. Hemoglobin concentration is 7.8 g/dL. Upper endoscopy shows circumferentially prominent tortuous veins with an adherent clot at the gastroesophageal junction. Which of the following mechanisms best explains the blood loss in this patient?
A. Acute inflammation of the gastroesophageal mucosa
B. Arteriovenous fistulae at the gastroesophageal junction
C. Hepatic artery obstruction with increased celiac pressure
D. Increased flow through collateral hepatic veins
E. Increased pressure in submucosal esophageal veins
41. During normal micturition, pressure within the bladder increases in response to which of the following changes?
A. Contraction of the external sphincter
B. Parasympathetic outflow from the sacral spinal cord
C. Somatic efferent outflow from the sacral spinal cord
D. Sympathetic outflow from the lumbar spinal cord
E. Voluntary relaxation of the external sphincter
42. A 45-year-old woman comes to the physician because of a mass in her left flank. Two months ago she had a hysterectomy for cervical cancer that had invaded beyond the serosa of the uterus. The mass is largely comprised of a markedly dilated renal pelvic and calyceal system. Which of the following is the most likely diagnosis?
A. Hydronephrosis
B. Hypernephroma
C. Nephrosclerosis
D. Pyelonephrosis
E. Vesicoureteral reflux
43. A 17-year-old girl with chronic renal insufficiency undergoes a unilateral nephrectomy. A photograph of the resected kidney is shown. Which of the following is the most likely cause of this patient's renal insufficiency?
A. Cervical cancer
B. Disseminated intravascular coagulation
C. Endometriosis
D. Essential hypertension
E. Fibromuscular dysplasia of the renal artery
F. IgA nephropathy
G. Poststreptococcal glomerulonephritis
H. Preeclampsia
I. Type 1 diabetes mellitus
J. Vesicoureteral reflux
44. A 35-year-old man comes to the physician because of a 3-week history of pain with urination and blood in his urine at the end of urination. He is a fishery consultant with the Peace Corps and returned to the USA 1 month ago following a 2-year assignment in Africa. He frequently came in contact with lake water while in Africa, ate locally prepared foods, and was sexually active with two women while using condoms consistently. Physical examination shows no abnormalities. Ultrasonography of the urinary tract shows bilateral mild hydronephrosis and nodules in the bladder. Exposure to which of the following types of organisms is the most likely cause of this patient's condition?
A. Bacteria
B. Fungus
C. Mycobacterium
D. Parasite
E. Virus
45. A 23-year-old woman comes to the physician because of heavy watery vaginal discharge, itching, and burning for 2 weeks. She is sexually active with one partner. Speculum examination shows profuse, foamy, yellow discharge. A wet mount preparation shows motile organisms and numerous leukocytes. Which of the following is the most likely diagnosis?
A. Bacterial vaginosis
B. Chancroid
C. Chlamydia trachomatis infection
D. Trichomoniasis
46. A previously healthy 29-year-old woman has the sudden onset of dyspnea and becomes unresponsive after the vaginal delivery of a male newborn who weighs 3570 g (7 lb 14 oz). Pregnancy was uneventful. Oxytocin was administered during labor to augment contractions. Examination shows no pulse and no spontaneous respirations. Which of the following is the most likely diagnosis?
A. Acute myocardial infarction
B. Amniotic fluid embolism
C. Eclampsia
D. Hemorrhagic cerebral stroke
E. Oxytocin overdose
47. A 22-year-old man with a nonseminomatous germ cell tumor is scheduled to undergo a course of chemotherapy with ifosfamide, carboplatin, and etoposide. Mesna should be added to his regimen to prevent which of the following potential toxic effects of the antineoplastic drugs?
A. Cardiomyopathy
B. Drug-induced leukemia
C. Hemorrhagic cystitis
D. Hyperglycemia
E. Pulmonary fibrosis
48. A 28-year-old woman is brought to the emergency department after being involved in an automobile collision. She has lost an estimated 400 mL of blood. Plasma renin activity is five times greater than the reference range. The most likely explanation for this increase is an increase in which of the following?
A. Arterial pressure
B. Renal sympathetic nerve activity
C. Serum angiotensin II concentration
D. Serum atrial natriuretic peptide concentration
E. Sodium delivery to the macula densa
49. A 22-year-old man comes to the physician's office because of fatigue, blurred vision, and increased thirst for the past 2 months. During this time, he has awakened several times a night to urinate, and urinates 8 to 10 times daily. He takes no medications. Serum sodium concentration is 160 mEq/L and urine osmolality is 165 mOsmol/kg H2O. Which of the following is the most likely diagnosis?
A. Acute renal failure
B. Aldosterone-secreting neoplasm
C. Congestive heart failure
D. Diabetes insipidus
E. Syndrome of inappropriate ADH (vasopressin)
50. A 60-year-old woman develops anemia several years after a subtotal gastrectomy. Which of the following is the most likely finding on a peripheral blood smear?
A. Basophilic stippling
B. Helmet cells
C. Macrocytosis of erythrocytes
D. Microcytosis of erythrocytes
E. Reticulocytosis