Lectus

A scientist is studying the development of CD8+ T cells. In his experiments, he uses a radioactive isotope to mark a population of T cells. Once injected into the thymus, these cells bind tightly to MHC I self-antigen complexes. Later in the experiment, the scientist cannot find any marked cells in the peripheral blood. Which of the following processes is responsible for the loss of these marked CD8+ cells?Deselect Answer

A 36-year-old man presents to his physician to discuss his concerns about developing heart disease. His father, grandfather, and older brother had heart problems, and the patient has become increasingly worried he might be at risk. He takes no medications, and his past medical history is only significant for an appendectomy 20 years ago. He is married with 2 young children, works as a hotel manager, and exercises occasionally in the hotel gym. He drinks 3–5 alcoholic beverages per week but denies smoking and illicit drug use. Today his blood pressure is 146/96 mm Hg, the pulse rate is 80/min, and the respiratory rate is 16/min. He has a body mass index of 26.8 kg/m2. His physical examination is otherwise unremarkable. Laboratory studies show:

Besides appropriate medications for his cholesterol and a follow-up for his hypertension, which of the following supplements is thought to provide a protective cardiovascular effect?Deselect Answer

A 1-month-old girl is brought to the pediatrician by her parents. They are concerned because she becomes lethargic and irritated between meals. They found that feeding her often with small servings helps. She was born at 39 weeks via spontaneous vaginal delivery and is meeting all developmental milestones. Her mother has 1 brother who occasionally requires blood transfusions. The child's blood pressure is 55/33 mm Hg, heart rate is 120/min, respiratory rate is 40/min, and temperature is 37.0°C (98.6°F). On physical exam, she is slightly jaundiced and appears irritated. Her heart has a regular rate and rhythm, with no abnormal sounds or murmurs, and her lungs are clear to auscultation bilaterally. Her blood work shows normocytic anemia with an elevated reticulocyte count and decreased haptoglobin. Sickle cell anemia and other hemoglobinopathies are also ruled out. A Coombs test is negative. The red blood cell osmotic fragility gap is normal. The physician determined that these findings are related to an enzyme deficiency. Which of the following allosterically inhibits this enzyme?Deselect Answer

A 43-year-old man with a history of HIV presents with a gradual onset of fever, shortness of breath, and a nonproductive cough for the past week. Past medical history is significant for HIV infection diagnosed ten years ago that was never treated with antiretroviral medication. Temperature is 39.0°C (102.2°F), heart rate is 104/min, respiratory rate is 20/min, and blood pressure is 120/80 mm Hg. Physical examination reveals bilateral crepitus over each lobe. No lymphadenopathy is present. A chest radiograph reveals diffuse bilateral interstitial infiltrates. His CD4⁺ T cell count is 105/µL. What is the preferred treatment for the most likely cause of this patient's current pulmonary condition?Deselect Answer