Tüm alıştırma soruları

A 24-year-old medical resident presents to the occupational health clinic in late January with sudden-onset high fever, severe myalgias, dry cough, and profound fatigue. She notes several of her patients had similar symptoms over the past week. A rapid point-of-care test confirms infection with an enveloped, negative-sense, single-stranded RNA virus with a segmented genome. The pathogen relies on a specific sequence of molecular events to successfully invade respiratory epithelial cells. Arrange the following steps of this virus's early entry and uncoating mechanism in the correct chronological order, from initial host cell contact to the delivery of its genetic material for replication.

A 72-year-old woman with a history of persistent atrial fibrillation presents to the emergency department 45 minutes after the sudden onset of right-sided hemiparesis and global aphasia. A non-contrast head CT shows no evidence of intracranial hemorrhage. She is diagnosed with an acute ischemic stroke in the territory of the left middle cerebral artery and is urgently evaluated for reperfusion therapy. At the cellular level, the sudden interruption of blood flow initiates a profound cascade of events in the ischemic penumbra that will ultimately lead to neuronal cell death if perfusion is not restored.

Arrange the following subcellular events in the chronological sequence they occur during the pathogenesis of excitotoxic neuronal injury in this patient, from the earliest initial event to the final terminal event.

A 68-year-old man with a history of ischemic cardiomyopathy (ejection fraction 35%) and osteoarthritis presents to the clinic with progressive shortness of breath and bilateral lower extremity edema over the past week. He states he has been taking his prescribed furosemide, lisinopril, and carvedilol daily. His blood pressure is 155/92 mmHg, and his heart rate is 78/min. Physical examination reveals jugular venous distention and bilateral crackles at the lung bases. When obtaining a targeted medical history to evaluate the cause of his decompensation, which of the following patient reports would be most directly responsible for his current presentation? (Select all that apply)

A 72-year-old man is evaluated in the emergency department for a massive hematoma on his right thigh that developed after a minor mechanical trauma. He has no prior personal or family history of bleeding disorders and has undergone multiple surgical procedures, including a cholecystectomy and prostatectomy, without excessive hemorrhage. His medical history includes hypertension, for which he takes lisinopril. Vital signs are within normal limits.

Laboratory studies show:
- Hemoglobin: $9.2 \text{ g/dL}$
- Platelet count: $250,000/\mu\text{L}$
- Prothrombin time (PT): $12 \text{ seconds}$ (Normal: $11-14 \text{ seconds}$)
- Activated partial thromboplastin time (aPTT): $78 \text{ seconds}$ (Normal: $25-35 \text{ seconds}$)

A mixing study is performed using normal pooled plasma. Immediately after mixing, the patient's aPTT corrects to $32 \text{ seconds}$. However, after incubating the mixture for $2 \text{ hours}$ at $37^\circ\text{C}$, the aPTT prolongs again to $68 \text{ seconds}$.

Which of the following is the most likely primary mechanism underlying this patient's bleeding diathesis?

A 62-year-old woman presents to the urgent care clinic with sudden-onset, severe right posterior calf pain that began while she was walking her dog in a park. The pain was followed rapidly by diffuse swelling of the lower leg. She has a history of advanced osteoarthritis in both knees and hypertension. Her current medications include amlodipine and as-needed ibuprofen. Vital signs are within normal limits. On physical examination, the right calf is visibly swollen, tense, and diffusely tender to palpation. The physician suspects a ruptured popliteal (Baker) cyst but wants to clinically differentiate this condition from an acute deep vein thrombosis prior to ordering ultrasonography. Which of the following physical examination findings is most specific for confirming a ruptured popliteal cyst in this patient?

A 54-year-old man is maintained on an oral lipophilic beta-blocker for heart failure. The drug is eliminated exclusively via hepatic metabolism. It is completely absorbed across the gastrointestinal epithelium ($f_a = 1.0$) with no intestinal wall metabolism. Pharmacokinetic profiling reveals the drug has a baseline hepatic extraction ratio ($E_H$) of $0.80$. The patient's hepatic blood flow ($Q$) is estimated at $1,500 \text{ mL/min}$.

The patient is subsequently diagnosed with latent tuberculosis and started on rifampin, a potent cytochrome P450 inducer. This induction increases the beta-blocker's hepatic intrinsic clearance ($CL_{int}$) by exactly $50\%$. Assuming the well-stirred model of hepatic clearance and that hepatic blood flow remains constant, what is the patient's new absolute oral bioavailability of the beta-blocker? Express your answer as a percentage rounded to one decimal place.

A 61-year-old man is admitted to the intensive care unit following an emergent exploratory laparotomy for a ruptured appendix. During the surgery, he experienced profound hemorrhagic shock, requiring massive fluid resuscitation and vasopressor support. On postoperative day 2, his urine output declines to 150 mL over 24 hours. Laboratory evaluation reveals a blood urea nitrogen of 72 mg/dL and a serum creatinine level of 4.3 mg/dL, elevated from a baseline of 0.9 mg/dL. Urinalysis is significant for the presence of numerous muddy brown granular casts, and the fractional excretion of sodium (FENa) is calculated at 2.8%. Renal ultrasonography reveals no evidence of urinary tract obstruction. The patient's acute renal dysfunction is primarily mediated by epithelial cell death. Which of the following subcellular mechanisms represents the critical point of transition to irreversible injury in these affected cells?

A $34$-year-old man with a history of Marfan syndrome is brought to the emergency department after the sudden onset of severe, tearing chest pain radiating to his back. He appears pale, diaphoretic, and in acute respiratory distress. His blood pressure is $90/50 \text{ mmHg}$, heart rate is $122 \text{ /min}$, and respiratory rate is $26 \text{ /min}$. A bedside echocardiogram reveals an ascending aortic intimal flap and a new, severe regurgitant jet across the aortic valve. Which of the following physical examination findings are most likely to be present in this patient? (Select all that apply)

A 62-year-old man is evaluated in the surgical intensive care unit for worsening clinical status. Seven days ago, he underwent an exploratory laparotomy for a perforated appendix with peritonitis. Intra-abdominal fluid cultures obtained at the time of surgery grew *Enterobacter cloacae*. He was started on intravenous ceftriaxone based on the following initial susceptibility report:

Over the past 24 hours, the patient has developed recurrent fever, tachycardia, and increased vasopressor requirements. His temperature is 39.1°C (102.4°F). Physical examination shows a rigid, tender abdomen. A computed tomography scan of the abdomen reveals a new intra-abdominal fluid collection. The fluid is aspirated, and cultures again grow *Enterobacter cloacae*. Susceptibility testing of this new isolate reveals the following:

Which of the following is the most likely molecular mechanism responsible for this patient's treatment failure?

Match each of the following classic physical examination maneuvers or signs with its most strongly associated clinical condition or diagnosis.

An infection control consultation is requested for a 55-year-old male patient in the surgical intensive care unit who recently developed a catheter-related bloodstream infection. The patient was admitted three weeks ago following a high-speed motor vehicle collision that required multiple exploratory laparotomies and bowel resections. During his hospitalization, he received prolonged courses of empiric broad-spectrum antibiotics. Today, blood cultures drawn from his central venous catheter are positive for Gram-positive cocci arranged in pairs and short chains. The pathogen is confirmed to be highly resistant to both ampicillin and vancomycin. Which of the following molecular mechanisms most likely explains this pathogen's resistance to the glycopeptide antibiotic?

A 65-year-old male with a history of symptomatic atrial fibrillation presents to the cardiology clinic to optimize his medical regimen. The physician decides to start an oral antiarrhythmic agent to maintain normal sinus rhythm. The selected drug has the following known pharmacokinetic parameters in this patient demographic:

* Volume of distribution ($V_d$): $40$ L
* Systemic clearance ($CL$): $2.5$ L/hr
* Oral bioavailability ($F$): $0.80$ ($80\%$)
* Half-life ($t_{1/2}$): $11.1$ hours

The target average steady-state plasma concentration ($C_{ss}$) for optimal efficacy without toxicity is $4.0$ mg/L. The physician plans to prescribe the medication to be taken orally every $12$ hours.

Based on these pharmacokinetic parameters, what is the appropriate single oral maintenance dose that should be administered every $12$ hours?

During morning rounds on the oncology service, a 71-year-old hospitalized individual is found profoundly lethargic and diaphoric. The patient was admitted two days ago for a core needle biopsy of a massive right-sided pleural mass that occupies the lower two-thirds of the hemithorax. Point-of-care capillary blood glucose is 32 mg/dL. A stat venous blood draw is obtained before the administration of intravenous dextrose, which rapidly restores the patient's normal sensorium. The laboratory results from the hypoglycemic episode return as follows:

Plasma glucose: 35 mg/dL
Serum insulin: < 1.0 µU/mL (Normal: 3-25 µU/mL)
Serum C-peptide: 0.1 ng/mL (Normal: 1.1-4.4 ng/mL)
Serum beta-hydroxybutyrate: 0.1 mmol/L (Normal: < 0.4 mmol/L)
Serum growth hormone (GH): < 0.1 ng/mL (Normal: 0.4-10 ng/mL)
Serum insulin-like growth factor 1 (IGF-1): 22 ng/mL (Normal: 70-250 ng/mL)

Which of the following cellular or biochemical mechanisms best explains this patient's clinical presentation and laboratory profile?

Match each clinical presentation with the most appropriate next step in diagnostic testing.

While participating in a high-intensity interval training class, a previously healthy 44-year-old man collapses after yelling about an explosive, agonizing pain in the back of his head. Emergency medical services transport him to the trauma bay. Upon arrival, he is conscious but lethargic, photophobic, and clutching his neck. Vital signs are significant for a blood pressure of 192/110 mmHg. Given the classic presentation for a spontaneous subarachnoid hemorrhage, the clinical team initiates a step-wise diagnostic and imaging pathway.

Assuming the first test is equivocal and the sequence must be followed to completion to identify the exact vascular source, arrange the following modalities in the correct chronological order of standard management, from the first initial step to the final definitive step.

During the physical examination of a patient presenting with acute abdominal symptoms, specific signs and maneuvers can provide critical diagnostic clues. Match each elicited abdominal examination finding with its most likely associated underlying pathology or clinical condition.

Match each patient's clinical presentation with the specific host cell receptor targeted by the responsible viral pathogen.

Following a recent medical mission in Southeast Asia where she sustained an accidental needlestick injury, a 24-year-old woman develops progressive fatigue, right upper quadrant abdominal pain, and dark urine. Physical examination confirms marked scleral icterus and a tender, palpable liver edge. Laboratory studies reveal severely elevated aspartate aminotransferase (AST) and alanine aminotransferase (ALT), alongside positive serologies for Hepatitis B surface antigen (HBsAg) and IgM anti-HBc. A liver biopsy is obtained to evaluate the extent of injury, demonstrating scattered shrunken, intensely eosinophilic cells with fragmented nuclei, known as Councilman bodies. The targeted elimination of these infected hepatocytes is primarily driven by cytotoxic T lymphocytes.

Arrange the following subcellular events in the correct chronological sequence that leads to the specific histological findings described in this patient's liver biopsy.

A thorough occupational and environmental history is a critical component of medical history evaluation. Different vocational exposures strongly predispose patients to specific pulmonary pathologies. Match each patient's key occupational history element with the most likely corresponding diagnostic consideration.

A 42-year-old woman is evaluated for a recurrence of high-grade serous ovarian carcinoma. She has a strong family history of breast and ovarian malignancies and is known to carry a deleterious germline mutation in the BRCA1 gene. Her oncologist initiates therapy with olaparib, an oral targeted agent that exploits the principle of synthetic lethality. Arrange the following molecular and cellular events in the correct chronological sequence that mediates the antineoplastic efficacy of this pharmacological intervention.