An obese 39-year-old woman with hirsutism and a long-standing history of anovulation is found to have endometrial hyperplasia and enlarged ovaries with multiple small cysts. The adipose tissue in this woman is most likely producing which of the following hormones?

An 18-year-old woman comes to the physician because of frequent, loose stools since the age of 3 years. Her 42-year-old mother and her 67-year-old maternal grandfather have similar symptoms. She is 163 cm (5 ft 4 in) tall and weighs 53 kg (116 lb); BMI is 20 kg/m2. Physical examination shows no other abnormalities. Serum studies show:

Stool analysis shows an increased fat concentration. Her affected family members have had similar laboratory findings. This patient most likely has a mutation in which of the following genes?

A 56-year-old man comes to the physician because of a 1-week history of fever, headache, and painful sores on his penis. Two weeks ago, he had unprotected sexual intercourse with a new female partner. His temperature is 38.2°C (100.8°F), pulse is 85/min, respirations are 15/min, and blood pressure is 128/72 mm Hg. Physical examination shows inguinal lymphadenopathy. Genital examination shows shallow, vesicular lesions on the shaft of the penis. Which of the following is the most likely diagnosis?

During a study of digestion, a healthy 25-year-old woman volunteers to eat a large meal consisting of turkey, dressing, sweet potatoes, mashed potatoes, peas, and rolls. She then has pecan pie and coffee. Pancreatic secretions show an immediate response in this subject with the secretion of fluid and pancreatic proenzymes, including trypsinogen. Which of the following substances is the most likely cause of trypsinogen activation in this woman’s intestine?

In some inherited disorders of collagen, lysyl oxidase activity is deficient. This enzyme deaminates the e-amino group of a lysyl residue in collagen and forms a reactive aldehyde. In turn, this aldehyde interacts with which of the following amino acid residues of another collagen molecule to cause cross-linking?

An investigator is recording the amplitude of the endplate potential (EPP) in a single striated muscle fiber on stimulation of the motor nerve. The graph shows the frequency distribution for EPPs of various amplitudes for all stimuli that produce a response. Which of the following shows the correct rank order for mode, median, and mean values from smallest to largest?

A 23-year-old woman is brought to the emergency department by her roommate because she was found unresponsive on the living room floor. Examination shows constricted pupils and stupor. Which of the following substances is most likely responsible for these effects?

The initial therapeutic effect of hydrochlorothiazide in patients with hypertension is a result of decreased sodium reabsorption in which of the following parts of the nephron?

An animal study is conducted to assess the effects of smoking on pulmonary defense and maintenance mechanisms. For 1 week, normal male rats are exposed to levels of cigarette smoke comparable to those encountered by humans who smoke cigarettes. Results of pulmonary testing are compared with baseline levels obtained the week before the smoke exposure. Which of the following sets of changes is most likely to be observed?

A feature of the host response to malaria in experimental animals is the activation of CD8+ T lymphocytes with specificity for malaria antigens. Which of the following is the best explanation for this response?

The graphs depict experiments in which cells of a murine sarcoma were injected subcutaneously into a histocompatible mouse, and the diameter of tumors in the recipient mouse was measured 10 days later. Graph A shows the results obtained with sarcoma cells. Graph B shows the results obtained with a variant of the tumor that fails to express class I MHC molecules. The difference in growth of the variant tumor is best explained by the action of which of the following cell types in the tumor cell recipient?

Norepinephrine is the primary neurotransmitter for which of the following nerves?

An investigator is studying the selective loss of neurons of an experimental animal model of Wernicke encephalopathy. It is found that a vitamin E31 (thiamine) deficiency in the animal causes downregulation of the glial high-affinity glutamate transporter before neurons are lost. Based on these findings, which of the following cells is most likely initially affected by this disease process?

A previously healthy 32-year-old woman comes to the physician because of a 3-month history of heavy menstrual bleeding, intermittent nosebleeds, and blood in her urine and stools. She says, “I’ve had to stop flossing because my gums bleed for an hour afterwards.” Physical examination shows numerous ecchymoses and petechiae over the lower extremities. A test result for circulating antiplatelet antibodies is positive. A photomicrograph of a biopsy specimen of bone marrow is shown. Which of the following is the most likely pathogenesis of this patient’s disease?

During an experiment, a strain of knockout mouse is developed that has an isolated deficiency of carbonic anhydrase in erythrocytes. No other type of cell or tissue is deficient in this enzyme. Compared with normal mice, venous blood in the knockout mouse will most likely have a higher concentration of which of the following substances?

A 50-year-old woman is admitted to the hospital for treatment of injuries sustained in a motor vehicle collision. Intubation and mechanical ventilation are initiated. The ventilator has adjustments for frequency, tidal volume, inspiratory and expiratory duration, and positive end-expiratory pressure (PEEP). The most effective way to decrease arterial Pco2 in this patient is to increase which of the following?

A 75-year-old man has the painless lesions shown. He worked outside for 30 years maintaining the grounds of a golf course. The lesions are rough to the touch. Which of the following is the most likely diagnosis?

A 47-year-old woman comes to the emergency department because of the recent onset of acute asthma-like breathing difficulty. She has had diarrhea and intermittent flushing for 4 months. An x-ray of the chest shows a well-circumscribed 2.3-cm mass in the central part of the lower lobe of the right lung. Urine 5-hydroxyindoleacetic acid concentration is increased. Which of the following is the most likely diagnosis?

A 20-year-old man comes to the emergency department because of a 2-day history of profuse watery diarrhea that began shortly after he returned from a trip to Central America. He appears alert. His temperature is 38.1 °C (100.6°F), pulse is 120/min, respirations are 24/min, and blood pressure is 90/60 mm Hg. Physical examination shows dry mucous membranes and poor peripheral perfusion. Compared with a healthy individual, laboratory studies are most likely to show which of the following sets of findings in this patient?

In a historical study, 4753 nulliparous women with confirmed pregnancies were randomized to either folic acid supplementation or trace element supplementation. In both the folic acid and trace element groups, 88% of the women had pregnancies ending in live birth, late fetal death, stillbirth, or termination of pregnancy after prenatal diagnosis of a defect. The following pregnancy outcomes were found:

Based on these data, using the trace element group as a control group, which of the following best represents how many nulliparous women with confirmed pregnancies would have to be treated with folic acid to prevent one congenital abnormality?

A 13-year-old girl is brought to the physician by her mother because of several blemishes on her face and back for 8 months. Physical examination shows scattered comedones and papules on the face and back. Treatment with a medication that decreases cohesion between epidermal cells and increases epidermal cell turnover is initiated. Which of the following drugs was most likely prescribed?

A 45-year-old man with Li-Fraumeni syndrome agrees to participate in an investigational study of tumor suppressor gene disorders. A mutation is found in his p53 tumor suppressor gene that converts an arginine to a proline at amino acid position 248 (R248P). This change alters hydrogen bonding between the mutant p53 tumor suppressor gene protein and the thymidine oxygen and adenine ring nitrogen of DNA. Which of the following is the most likely result of this mutation on the transcription of genes that inhibit cell division and contain the consensus sequence TATA (A/T) (A/T) at -30 bp 5′ to the transcription start site?

The graph shows the plasma concentration of an antibiotic as a function of time after an intravenous bolus. If the antibiotic is administered continuously by intravenous infusion, approximately how many hours will it take for the plasma concentration of the drug to first achieve almost 97% of its steady-state concentration?

An investigator is studying the human immune response to tumor cell antigens in malignancies. Which of the following sets of cancer types and tumor antigens is most likely to produce the highest antibody titer?

A 66-year-old man is brought to the emergency department 30 minutes after sustaining injuries in a motor vehicle collision. He is pronounced dead on arrival. A photograph of the left kidney and a photomicrograph of a section of the distal left ureter taken at autopsy are shown. Examination of the right kidney and ureter shows no abnormalities. Which of the following was the most likely predisposing factor in the development of the ureteral lesion in this patient?

A 79-year-old woman with a history of severe dementia, type 2 diabetes mellitus, and hypertension is brought to the emergency department by her son because of chest pain and agitation for 4 hours. She had smoked 2 packs of cigarettes daily until the age of 70 years, when she quit. The son is not aware of the patient’s medication regimen. Her pulse is 120/min, respirations are 32/min, and blood pressure is 180/100 mm Hg. Crackles are heard in both lung bases on auscultation of the chest. Cardiac examination shows a systolic ejection murmur at the apex and a regular rhythm. An ECG shows ST-segment elevation in the anterolateral leads. A chest x-ray shows a mildly enlarged cardiac silhouette. Which of the following is the most likely diagnosis?

A 16-year-old girl with a medulloblastoma is scheduled to begin chemotherapy with a combination of agents, including cisplatin. Addition of ondansetron may decrease emesis by blocking which of the following receptors?

A 35-year-old woman with HIV infection has a first generalized tonic-clonic seizure. An MRI shows a small, solitary, enhancing lesion in the right frontal lobe. If stereotactic biopsy of this lesion were performed, it would show intense infiltration of lymphocytes, plasma cells, and macrophages and numerous 3 x 7-mm crescent-shaped organisms with central nuclei. The lesion regresses slowly after treatment with sulfonamide and pyrimethamine. Which of the following is the most likely mode of transmission of this infection?

A 30-year-old woman has excessive gingival bleeding 8 hours after a tooth extraction. She has taken 400 mg of acetaminophen every 3 hours since the procedure. Laboratory studies show:

Which of the following is the most likely diagnosis?

A 57-year-old man with a 4-year history of type 2 diabetes mellitus has increased skin pigmentation, moderate ascites, and esophagogastric varices. Tissue obtained from biopsy of the liver is shown. Which of the following substances is most likely to be markedly increased in hepatocytes?

A 52-year-old man comes to the emergency department 2 hours after developing shortness of breath and nearly fainting while exercising. He is currently asymptomatic. He has a 6-month history of similar episodes that are becoming increasingly severe. He also has a 2-month history of intermittent chest pain with exertion. He last experienced this pain 3 days ago. He has no history of major medical illness and takes no medications. His father has hypertension. His temperature is 36.9°C (98.4°F), pulse is 76/min, respirations are 12/min, and blood pressure is 108/88 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 97%. Cardiac examination shows a systolic murmur that is heard best at the upper right sternal border. An ECG and intracardiac pressure tracings from this patient are shown. Which of the following is the most likely underlying cause of this patient’s condition?

A41-year-old man comes to the physician because of a 6-week history of numbness of his right hand. He works in construction. Sensation to pinprick is decreased in the thumb and over a portion of the anterior forearm. The physician suspects that there is compression of the C5 and C6 spinal nerves as they exit the spinal canal. Weakness of which of the following movements on the right is most likely to confirm the diagnosis?

A 22-year-old woman is brought to the emergency department 30 minutes after stepping on a piece of glass while jogging on the beach. Physical examination shows a 1-cm laceration of the right foot with a deeply embedded glass shard. The shard is removed, and the wound is cleaned and sutured. After 3 days, the pain at the injury site has subsided, but the patient has numbness of the surrounding area within 4 mm of the sutures. Three weeks later, sensation is normal. Which of the following cell types most likely facilitated the reinnervation of the skin of this patient’s foot?

A 35-year-old man comes to the physician because of a tremor for 6 weeks. He has a 15-year history of schizophrenia treated with haloperidol. Physical examination shows bradykinesia, tremor, and cogwheel rigidity. Haloperidol is discontinued, and treatment with aripiprazole is started because it has a decreased likelihood of causing the same adverse effects. Which of the following types of interaction with the dopamine receptor best explains this decreased likelihood?

A 16-year-old girl with type 1 diabetes mellitus is brought to the physician because of a 10-kg (22-lb) weight loss during the past 6 months. The patient reports that she is feeling fine, and she does not think that anything is wrong. She says that she is happy to have lost the weight, and she would like to lose more weight. She says that her diabetes has been in good control, and she is not aware of any insulin reactions. She is 165 cm (5 ft 5 in) tall and now weighs 46 kg (102 lb); BMI is 17 kg/m2. Physical examination shows no other abnormalities. Laboratory studies show a hemoglobin A1c of 8.4%; 6 months ago, it was 5.8%. Which of the following patient behaviors most likely led to her weight loss?

A 45-year-old man receives the diagnosis of Achilles tendon rupture. He is a long-distance runner. He has had an upper respiratory tract infection for 3 weeks and was treated with antibiotics. Which of the following agents is the most likely cause of the Achilles tendon rupture?

An investigator studying the energy requirements for acid secretion in gastric mucosa cells observes that the energy needed to secrete 1.0 nmol of H+is 7 x10^-9 kcal. Given this result, how many ATP molecules must be hydrolyzed during the secretion of one H ion?

A 25-year-old woman, gravida 2, para 1, at 20 weeks’ gestation comes to the physician for a routine prenatal visit. She has no history of any major medical illness. She says that she feels healthy, but her 2-year-old daughter recently had pneumonia. Her respirations before the pregnancy were 16/min. Her pulse is 80/min, respirations now are 22/min, and blood pressure is 100/60 mm Hg. Physical examination shows a uterine fundal height at the level of the umbilicus, consistent with a 20-week gestation. Which of the following best explains the increased respirations in this patient?

A 47-year-old man comes to the physician because of a 2-day history of yellow eyes and skin. He has undergone a total colectomy and reanastomosis at the age of 20 years because of the presence of numerous colon polyps, and he has a family history of colon cancer. Physical examination shows scleral icterus, generalized jaundice, and a nontender mass that is palpable in the right upper quadrant of the abdomen. Upper endoscopy shows four duodenal polyps; a 4-cm mass is seen arising from one of them. A CT scan of the abdomen shows extension of the duodenal mass into the head of the pancreas. Histopathologic examination of the resected mass shows an adenocarcinoma arising from a duodenal adenoma. Molecular analysis of the adenocarcinoma is most likely to show which of the following?

A 25-year-old woman comes to the physician because of a 3-year history of irregular menses. Menarche was at the age of 14 years. Puberty began at the age of 12 years and progressed normally. Her blood pressure is 116/62 mm Hg. Physical examination shows increased hair growth on the face and chest. Pelvic examination shows clitoromegaly and a normal-appearing uterus. Serum studies show increased concentrations of 17-hydroxyprogesterone and androstenedione. This patient most likely has a deficiency of which of the following enzyme activities?

A 13-year-old girl is brought to the physician by her mother because of a 5-month history of behavioral problems. The mother states that her daughter alternates from being sad and socially withdrawn to being extremely angry and aggressive. After further evaluation, a diagnosis of bipolar disorder is made. Treatment with valproic acid, which inhibits histone deacetylase, is started. This drug is most likely to affect which of the following processes in this patient?

An investigator wants to determine if coffee drinking is associated with pancreatic cancer. Coffee drinking histories of persons with cancer were compared with those of healthy persons. Which of the following best describes this type of study?

A 38-year-old woman comes to the physician because of nasal congestion, cough, and shortness of breath for 5 days. She has asthma and allergic rhinitis currently treated with montelukast, an inhaled β2-adrenergic agonist, and nasal and inhaled corticosteroids. Physical examination shows an erythematous nasal mucosa. Bilateral crackles are heard at the lung bases posteriorly. Laboratory studies show peripheral blood eosinophilia. A chest x-ray shows peripheral infiltrates in the mid lungs bilaterally with a right¬sided pleural effusion. A lung biopsy specimen shows necrotizing vasculitis, granulomas, and eosinophilic necrosis. Which of the following is the most likely diagnosis?

A 16-year-old boy comes to the physician because of wrist pain for 1 week. X-rays of the upper extremities from 4 years ago (Figure A) and today (Figure B) are shown. The x- rays are read as normal. Which of the following hormones most likely mediated the change observed in the x-rays?

A 70-year-old man comes to the physician because of difficulty sleeping since his wife died 8 months ago. He states that he sometimes wakes up an hour earlier than usual without being able to go back to sleep. He also often cries when he thinks about his wife. He tells the physician that he once briefly followed a woman down the street who resembled her. The patient continues to enjoy visits with his grandchildren and remains an active member of his bowling team. He does not have any other depressive symptoms or suicidal ideation. Physical examination shows no abnormalities. Which of the following is the most appropriate initial action by the physician?

A 58-year-old woman comes to the physician because of a 3-month history of mild urine leakage when she washes her hands or when she hears water running. The leakage does not occur with coughing or sneezing. There is no nocturia, urinary hesitancy, or straining with urination. Her vital signs are within normal limits. Physical examination shows no abnormalities. Which of the following is the most likely cause of this patient’s incontinence?

A 2-month-old boy is brought to the physician because of hypotonia and poor feeding since birth. Physical examination shows large fontanels, midface hypoplasia, hepatomegaly, and cryptorchidism. Serum studies show increased concentrations of very-long-chain fatty acids, phytanic acid, and pipecolic acid. If this patient’s hepatocytes were analyzed using electron microscopy, results would most likely show the absence of which of the following organelles?

A 70-year-old man has coronary artery bypass grafting and aortic valve replacement. Immediately after the operation, his blood pressure is 8 0/40 mm Hg, and he requires an intra-aortic balloon pump and intravenous infusion of dopamine. After 24 hours of treatment, his blood pressure is 140/80 mm Hg. Serum creatinine concentration is 4.5 mg/dL (preoperative value 1 mg/dL). Urine output is 15 mL/h. Which of the following best explains these findings?

An investigator is studying a respiratory epithelial cell line. The cell line is infected with a newly discovered coronavirus. Which of the following steps is essential for the reproduction of this new virus?

An 82-year-old woman is brought to the physician because of a 1-week history of episodes of light-headedness and fainting. She has hypertension currently treated with propranolol. Her pulse is 45/min, and blood pressure is 90/50 mm Hg. Physical examination shows no other abnormalities. An ECG shows normal, regular P waves followed by normal QRS complexes. The physician decreases the dose of propranolol. Five days later, the patient’s pulse is 80/min, and her symptoms have resolved. Which of the following is the most likely explanation for this patient’s low pulse while taking the higher dose of propranolol?