Cell Injury - WebPath

In an experiment, a series of immunohistochemical stains are employed to identify different cellular components. One particular stain identifies the presence of intermediate filaments within cells. This cytokeratin stain is most likely to be useful for which of the following diagnostic purposes? a. cytoskeletal alterations indicate impending cell death b. a neoplasm is determined to be a carcinoma c. contractile properties of the cells can be assessed d. a history of chronic alcoholism can be confirmed e. the degree of metaplasia or dysplasia can be assessed

A NEOPLASM IS DETERMINED TO BE A CARCINOMA

A cellular mutation results in transcription with translation of a protein that does not fold properly. The misfolded protein remains within the cell and is not excreted. Activation of which of the following cytoplasmic enzymes is most likely to occur? a. caspase b. glutathione peroxidase c. NADPH oxidase d. ribonuclease e. terolmerase

CASPASE

A 65-year-old woman has the sudden inability to move her right arm and to speak. MR angiography shows occlusion of a cerebral artery. She is given tissue plasminogen activator (tPA). Over the next week she regains some ability to move her arm and to speak. Which of the following cellular changes most likely subsided upon tPA therapy? a. cell fragmentation b. cell swelling c. cytoplasmic eosinophilia d. membrane disruption e. nuclear karyorrhexis f. nuclear pyknosis

CELL SWELLING

A 73-year-old man suffers a 'stroke.' On physical examination he cannot move his right arm. A cerebral angiogram demonstrates occlusion of the left middle cerebral artery. An echocardiogram reveals a thrombus within a dilated left atrium. Which of the following is the most likely pathologic alteration from this event that has occurred in his brain? a. cerebral softening from liquefactive necrosis b. pale infarction with coagulative necrosis c. predominantly the loss of glial cells d. recovery of damaged neurons if the vascular supply is reestablished e. wet gangrene with secondary bacterial infection

CEREBRAL SOFTENING FROM LIQUEFACTIVE NECROSIS

A 12-year-old boy has had multiple episodes of ear pain accompanied by fever. On examination his right tympanic membrane is red and bulging with yellow exudate. Laboratory studies of the exudate show culture positive for Hemophilus influenzae. A year later he has conductive hearing loss on the right, and a head CT scan shows a mass in the right middle ear. Which of the following materials is most likely to be seen in the tissue curetted from his middle ear? a. lipofuscin pigment b. russell bodies c. neutrophil granules d. cholesterol crystals e. anthracitic pigment

CHOLESTEROL CRYSTALS

A 26-year-old man has had a high fever for the past 2 days. On exam he has a heart murmur. Echocardiography shows destruction of the aortic valve by large, irregular vegetations. Staphylococcus aureus is cultured from his blood. He develops left upper quadrant pain. Abdominal CT shows a wedge-shaped 1.5 x 3 cm splenic lesion with base on the capsule. The splenic lesion is most likely to result from which of the following cellular abnormalities? a. coagulative necrosis b. abscess formation c. metaplasia d. caseous necrosis e. liquefactive necrosis

COAGULATIVE NECROSIS

A morbidly obese 51-year-old woman dies from complications of heart disease. At autopsy, her heart weighs 600 gm (normal up to 300 gm) with all the chambers enlarged. Microscopically, there is increased fibrous connective tissue seen in the interstitium between myocardial fibers. The fibers are increased in size. Beneath the epicardium can be seen adipocytes interdigitating with the myocardial fibers. Which of the following terms best describes the presence of the adipocytes in her myocardium? a. steatosis b. lipid degeneration c. fatty infiltration d. cholesterolosis e. xanthomatosis

FATTY INFILTRATION

An experiment is conducted to determine if cell membrane injury is lessened by the effects of vitamin E ingestion. Which of the following cellular components is primarily involved in generation of lipid peroxides, the formation of which is inhibited by the vitamin E? a. glutathione b. ionized calcium c. lactate d. ferric iron e. lipase

FERRIC IRON

A 53-year-old man suffers a cardiac arrest and his wife calls emergency services. The paramedics arrive a few minutes later and begin life support measures. A regular heart rate is established after 40 minutes of resuscitative efforts as he is being transported to the hospital. A thrombolytic agent (tPA) is administered. Which of the following cellular processes is most likely to occur in his myocardium following administration of the tPA? a. apoptosis b. free radical injury c. heterophagocytosis d. squamous metaplasia e. accumulation of cytokeratines

FREE RADICAL INJURY

A 55-year-old man has a 30-year history of poorly controlled diabetes mellitus. He has had extensive black discoloration of skin and soft tissue of his right foot, with areas of yellowish exudate, for the past 2 months. Staphylococcus aureus is cultured from this exudate. A below-the-knee amputation is performed. The amputation specimen received in the surgical pathology laboratory is most likely to demonstrate which of the following pathologic abnormalities? a. neoplasia b. gangrene c. vasculitis d. hemosiderosis e. caseation

GANGRENE

In an experiment, a tissue preparation is subjected to oxidant stress. There are increased numbers of free radicals generated within the cells. Generation of which of the following enzymes within these cells is the most likely protective mechanism to reduce the number of free radicals? a. glutathione peroxidase b. catalase c. hydrogen peroxide d. NADPH oxidase e. myeloperoxidase

GLUTATHIONE PEROXIDASE

While in a home improvement center warehouse buying paint, a 35-year-old man hears 'Look out below!' and is then struck on the leg by a falling pallet rack, which strikes him on his left leg in the region of his thigh. The skin is not broken. Within 2 days there is a 5 x 7 cm purple colour to the site of injury. Which of the following substances has most likely accumulated at the site of injury to produce a yellow-brown colour at the site of injury 16 days later? a. lipofuscin b. bilirubin c. melanin d. hemosiderin e. glycogen

HEMOSIDERIN

A 22-year-old woman has a congenital anemia. She has required multiple transfusions of red blood cells for many years. She now has no significant findings on physical examination. Which of the following microscopic findings would most likely present in her liver? a. steatosis in hepatocytes b. bilirubin in canaliculi c. hemosiderin in hepatocytes d. glycogen in hepatocytes e. amyloid in portal triads

HEMOSIDERIN IN HEPATOCYTES

A 3-year-old child has been diagnosed with ornithine transcarbamylase deficiency and has developed hepatic failure. The left lobe of an adult donor liver is used as an orthotopic transplant. A year later, the size of each liver in donor and recipient is greater than at the time of transplantation. Which of the following cellular alterations is most likely to explain this phenomenon? a. metaplasia b. dysplasia c. hyperplasia d. anaplasia e. neoplasia

HYPERPLASIA

A 71-year-old man has difficulty with urination. His urinary retention leads to numerous trips to the restroom per day. On digital rectal examination is prostate is diffusely enlarged. Which of the following represents a pathologic change leading to this man's problem? a. dysplasia b. hypertrophy c. hyperplasia d. metaplasia e. neoplasia

HYPERPLASIA

A 20-year-old woman had Goodpasture syndrome which progressed to chronic renal failure. She is 165 cm tall and weighs 55 kg. She now has blood pressure measurements in the range of 150/90 to 180/110 mm Hg, but does not regularly take medications. Laboratory studies show her blood urea nitrogen is over 100 mg/dL and she requires chronic dialysis. A chest x-ray shows an enlarged heart. The size of her heart is most likely to be the result of which of the following processes involving the myocardial fibers? a. hypertrophy b. fatty infiltration c. hyperplasia d. fatty degeneration e. edema

HYPERTROPHY

The lifestyle patterns of healthy persons from 20 to 30 years of age are studied. A subset of these persons have a lifestyle characterized by consumption of a lot of pizza and very little physical exercise. Which of the following tissue changes is most likely to develop in this subset of persons as a consequence of this lifestyle? a. fatty metamorphosis of liver b. pancreatic fat necrosis c. fatty degeneration of myocardium d. hypertrophy of steatocytes e. metaplasia of muscle to adipose tissue

HYPERTROPHY OF STEATOCYTES

A 44-year-old woman has had episodes of right upper quadrant pain during the past 2 weeks. Her stools have become pale in colour over the past 3 days. Laboratory studies show a serum total bilirubin of 9.7 mg/dL. A cholangiogram shows that a gallstone has passed into the common bile duct, resulting in obstruction of the biliary tract. Which of the following tissue accumulations is most likely to be visualized on her skin surfaces? a. hemosiderosis b. calcification c. lipofuscin deposition d. icterus e. steatosis

ICTERUS

A 50-year-old woman with a history of unstable angina suffers an acute myocardial infarction. Thrombolytic therapy with tissue plasminogen activator (tPA) is administered to restore coronary blood flow. In spite of this therapy, the degree of myocardial fiber injury may increase because of which of the following cellular abnormalities? a. cytoskeletal intermediate filament loss b. decreased intracellular pH from anaerobic glycolysis c. increased free radio formation d. mitochondrial swelling e. nuclear chromatin clumping f. reduced protein synthesis

INCREASED FREE RADICAL FORMATION

A 49-year-old man with a history of alcohol abuse has increasing abdominal girth. On examination his liver edge is firm. A liver biopsy shows cirrhosis, and individual hepatocytes contain red, globular inclusions positive for cytokeratin with immunohistochemical staining. Which of the following structural elements are these intracellular globules most likely to contain? a. actin and myosin b. cholesterol esters c. fatty acids d. fibronectin e. intermediate filaments f. microtubules

INTERMEDIATE FILAMENTS

A 45-year-old man has noted scleral icterus for the past 4 days. He has been feeling tired and 'run down' for about a month. On physical examination, other than mild tachycardia, his vital signs are normal. No other physical examination findings are of noted other than scleral icterus. Laboratory studies show a hematocrit of 25%. Which of the following conditions is most likely to account for these findings? a. systemic hypertension b. excessive iron absorption c. diabetes mellitus, type I d. intravascular hemolysis e. pulmonary squamous cell carcinoma

INTRAVASCULAR HEMOLYSIS

A 46-year-old man has smoked 2 packs of cigarettes per day for the past 30 years. He has had a chronic cough for the past 3 years, worsening over the last 2 weeks. A suspicious left pulmonary parenchymal lesion is seen on a chest x-ray. He has a bronchoscopy performed. A biopsy of a segmental bronchus shows squamous metaplasia. Which of the following is the most appropriate interpretation of this finding? a. ischemic tissue damage b. irritant effect c. early stage of cancer d. viral infection e. congenital anomaly

IRRITANT EFFECT

A 35-year-old woman has had headaches and abdominal pain worsening for 3 months. There are no remarkable physical examination findings. On radionucleide scanning of the neck, she is found to have a mass involving one of her parathyroid glands. An abdominal CT scan suggests extensive nephrocalcinosis along with urinary tract calculi. Which of the following laboratory test findings is most likely to accompany her disease? a. CO2 of 30 mmol/L b. Phosphorus of 2.2 mg/dL c. Uric acid of 15.1 mg/dL d. Sodium of 121 mmol/L e. Calcium of 4.5 mg/dL

PHOSPHOROUS OF 2.2 mg/dL

A study is performed involving the microscopic analysis of tissues obtained from surgical procedures. Some of these tissues have the microscopic appearance of an increased cell size of multiple cells within the tissue, due to an increase in the amount of cell cytoplasm, with nuclei remaining uniform in size. Which of the following conditions is most likely to have resulted in this finding? a. uterine myometrium in pregnancy b. female breast at puberty c. liver following partial resection d. ovary following menopause e. cervix with chronic inflammation

UTERINE MYOMETRIUM IN PREGNANCY

A 42-year-old previously healthy woman notes that over the past week her eyes have developed a yellowish appearance. She has had mild nausea and vomiting over the past week. On physical examination she has scleral icterus. She has no other major physical examination findings except for mild right upper quadrant tenderness. Which of the following underlying conditions is most likely to contribute to development of her icterus? a. hypercholesterolemia b. thrombocytopenia c. metastatic carcinoma d. viral hepatitis e. diabetes mellitus

VIRAL HEPATITIS

In an experiment, a disease process is found which leads to scattered loss of individual cells, with the microscopic appearance of karyorrhexis and cell fragmentation. The overall tissue structure remains intact. This process is most typical for which of the following diseases? a. viral hepatitis b. brown atrophy of the heart c. renal transplant rejection d. chronic alcoholic liver disease e. barbiturate overdose

VIRAL HEPATITIS

A study is performed to identify predisposing risks for tissue cellular changes. In some persons epithelial metaplasia occurs. In which of the following situations is the process of epithelial metaplasia most likely to take place? a. tanning of the skin following sunlight exposure b. lactation following pregnancy c. vitamin A deficiency d. acute myocardial infarction e. urinary obstruction from an enlarged prostate

VITAMIN A DEFICIENCY

An 18-year old G2 P1 woman has an amniocentesis performed at 17 weeks gestation. Fibroblasts recovered from amniocentesis are grown in culture to assess the karyotype of fetal cells. These cells are subcultured for additional experimental work, but the culture is lost after 50 doublings of the cells has occurred, and the fibroblasts no longer grow. Which of the following factors affecting these cells is most likely demonstrated by this phenomenon? a. nutrition b. mutation c. apoptosis d. aging e. oxidation

AGING

A 35-year-old woman has developed increasing icterus over the last week. On exam her liver span is increased. Laboratory studies show hyperammonemia. Abdominal CT scan shows a liver twice normal size with markedly reduced attenuation. These changes in her liver most likely resulted from which of the following conditions? a. galactosemia b. hemochromatosis c. tuberculosis d. alcoholism e. hypoxemia

ALCOHOLISM

A 54-year-old man with a chronic cough has a squamous cell carcinoma diagnosed in his right lung. While performing a pneumonectomy, the thoracic surgeon notes that the hilar lymph nodes are small, 0.5 to 1.0 cm in size, and jet black in colour throughout. Which of the following is the most likely cause for this appearance to the hilar nodes? a. anthracitic pigment b. lipochrome deposits c. melanin accumulation d. hemosiderosis e. metastatic carcinoma

ANTHRACITIC PIGMENT

A 48 year old woman has a malignant lymphoma involving lymph nodes in the para-aortic region. She is treated with a chemotherapeutic agent which results in the loss of individual neoplastic cells through fragmentation of individual cell nuclei and cytoplasm. Over the next 2 months, the lymphoma decreases in size, as documented on abdominal CT scans. By which of the following mechanism has her neoplasm primarily responded to therapy? a. coagulative necrosis b. mitochondrial poisoning c. phagocytosis d. acute inflammation e. apoptosis

APOPTOSIS

A 31-year-old primigravida has a difficult delivery of a term infant, with loss of 1500 cc of blood. She has hypotension for 6 hours. Over the next month, her ACTH level decreases. Within the next 3 months, her adrenal glands become decreased in size. This alteration of the adrenals is primarily due to which of the following cellular processes? a. metaplasia b. gene mutation c. apoptosis d. autophagocytosis e. coagulative necrosis

AUTOPHAGOCYTOSIS

A 30-year-old woman is claiming in a civil lawsuit that her husband has abused her for the past year. A workup by her physician reveals a 2 cm left breast mass. There is no lymphadenopathy. No skin lesions are seen, other than a bruise to her upper arm. A needle biopsy of the breast mass is performed. On microscopic examination, the biopsy shows fat necrosis. This biopsy result is most consistent with which of the following etiologies? a. physiologic atrophy b. breast trauma c. lactation d. radiation injury e. hypoxic injury

BREAST TRAUMA

At the end of a normal menstrual cycle, the endometrium sloughs. Examination of the endometrium microscopically shows cellular fragmentation. Which of the following is most likely to trigger apoptosis in these endometrial cells? a. acute inflammation b. hypoxia c. p53 protein accumulation d. decreased estrogen e. anaerobic glycolysis

DECREASED ESTROGEN

A 60-year-old woman has noted a dark red-black appearance to her great toe and second and third toes of her left foot for the past month. On physical examination, the toes are cold and have no sensation to touch. The dorsalis pedis and posterior tibial pulses are not palpable on the left. A transmetatarsal amputation is performed. These findings are most typical for a patient with which of the following conditions? a. diabetes mellitus b. gout c. blunt force trauma d. AIDS e. rheumatoid arthritis

DIABETES MELLITUS

A 21-year-old woman has a routine Pap smear performed for a health screening examination. The pathology report indicates that some cells are found cytologically to have larger, more irregular nuclei. A follow-up cervical biopsy microscopically demonstrates disordered maturation of the squamous epithelium, with hyperchromatic and pleomorphic nuclei extending nearly the full thickness of the epithelial surface. No inflammatory cells are present. Which of the following descriptive terms is best applied to these Pap smear and biopsy findings? a. dysplasia b. metaplasia c. anaplasia d. hyperplasia e. aplasia

DYSPLASIA

A 38-year-old man has a health screening examination. He has a routine chest x-ray that shows a 2 cm nodule in the right lower lobe. The nodule has focal calcifications. A wedge resection of the nodule is done. On microscopic examination the nodule shows caseous necrosis and calcification. Which of the following processes explains the appearance of the calcium deposition: a. dystrophic calcification b. apoptosis c. hypercalcemia d. metastatic calcification e. excessive ingestion of calcium

DYSTROPHIC CALCIFICATION

A 79-year-old man has a large myocardial infarction involving much of the left ventricular free wall. He develops congestive heart failure (CHF) with decreased cardiac output. Now, a year later, his CHF is worsening. By echocardiography there is a large, bulging akinetic area typical for a left ventricular aneurysm. Which of the following laboratory tests on serum would best indicate poor peripheral tissue perfusion in this patient? a. elevated troponin I b. increased sodium c. elevated lactate d. increased hematocrit e. increased sedimentation rate

ELEVATED LACTATE

A 40-year-old woman has the sudden onset of severe abdominal pain. On physical examination she has diffuse tenderness in all abdominal quadrants, with marked guarding and muscular rigidity. She has laboratory findings that include serum AST of 43 U/L, ALT of 30 U/L, LDH 630 U/L, and lipase 415 U/L. An abdominal CT scan reveals peritoneal fluid collections and decreased attenuation along with enlargement of the pancreas. Which of the following cellular changes is most likely to accompany these findings? a. coagulative necrosis b. dry gangrene c. fat necrosis d. apoptosis e. liquefactive necrosis

FAT NECROSIS

A 48-year-old man has a history of chronic alcohol abuse. He is still able to perform work at his job. He has had no major illnesses. On physical examination, there are no significant findings. Laboratory studies show a serum albumin of 4.1 g/dL, ALT 30 U/L, AST 33 U/L, and total bilirubin 1.1 mg/dL. Which of the following microscopic findings in his liver is most likely to be present? a. cholestasis b. fatty change c. hemochromatosis d. hypertrophy of smooth endoplasmic reticulum e. coagulative necrosis

FATTY CHANGE

A 45-year-old man has a traumatic injury to his forearm and incurs extensive blood loss. On physical examination in the emergency department his blood pressure is 70/30 mm Hg. Which of the following cellular changes is most likely to represent irreversible cellular injury as a result of this injury? a. epithelial dysplasia b. cytoplasmic fatty metamorphosis c. nuclear pyknosis d. atrophy e. anaerobic glycolysis f. autophagocytosis

NUCLEAR PYKNOSIS

A 38-year-old woman has severe abdominal pain with hypotension and shock that has developed over the past 36 hours. On physical examination, her abdominal muscles are rigid and her abdomen is extremely tender. An abdominal CT scan reveals fluid density in the region of the pancreas, which appears to be enlarged. Which of the following laboratory test findings in her serum is most likely to be present? a. alanine aminotransferase of 1123 U/L b. total cholesterol of 324 mg/dL c. creatine kinase of 869 U/L d. urea nitrogen of 110 mg/dL e. lipase of 1134 U/L

LIPASE OF 1134 U/L

An 84-year-old man dies from complications of Alzheimer disease. At autopsy, his heart is small (250 gm) and dark brown on sectioning. Microscopically, there is light brown perinuclear pigment with H&E staining of the cardiac muscle fibers. Which of the following substances is most likely increased in the myocardial fibers to produce this appearance of his heart? a. hemosiderin from iron overload b. lipochrome from "Wear and tear" c. glycogen form a storage disease d. cholesterol from atherosclerosis e. calcium deposition following necrosis

LIPOCHROME FROM "WEAR AND TEAR"

A 71-year-old woman had the loss of consciousness that persisted for over an hour. When she becomes arousable, she cannot speak nor move her right arm. A cerebral angiogram revealed an occlusion to her left middle cerebral artery. Months later, a computed tomographic (CT) scan shows a large 5 cm cystic area in her left parietal lobe cortex. This CT finding is most likely the consequence of resolution from which of the following cellular events? a. liquefactive necrosis b. atrophy c. coagulative necrosis d. caseous necrosis e. apoptosis

LIQUEFACTIVE NECROSIS

A 19-year-old woman gives birth to her first child. She begins breast feeding the infant. She continues breast feeding for almost a year with no difficulties and no complications. Which of the following cellular processes that began in the breast during pregnancy allowed her to nurse the infant for this period of time? a. stromal hypertrophy b. epithelial dysplasia c. steatocyte atrophy d. ductal epithelial metaplasia e. lobular hyperplasia

LOBULAR HYPERPLASIA

A 31-year-old woman has been previously diagnosed with systemic lupus erythematosus. She has had chest pain for the past 6 months. A chest radiograph shows bilateral pleural effusions. Thoracentesis on the right yields 400 mL of clear yellow serous fluid, and a cell count shows only a few cells present. What type of cell is most likely to be most numerous in this fluid? a. basophil b. ciliated columnar cell c. eosinophil d. fibroblast e. langhans giant cell f. lymphocyte g. neutrophil

LYMPHOCYTE

A 53 year old man has experienced severe chest pain for the past 6 hours. On physical examination he is afebrile, but has tachycardia. Laboratory studies show a serum troponin l of 10 ng/mL. A coronary angiogram is performed emergently and reveals >90% occlusion of the anterior inter ventricular (left anterior descending) artery. In this setting, an irreversible injury to myocardial fibers will have occurred when which of the following cellular changes occurs? a. glycogen stores are depleted b. cytoplasmic sodium increases c. nuclei undergo kayorrhexis d. intracellular pH diminishes e. blebs form on cell membrane

NUCLEI UNDERGO KARYORRHEXIS

A 38-year-old man incurs a traumatic blow to his upper left arm. He continues to have pain and tenderness even after 3 months have passed. A plain film radiograph reveals a 4 cm circumscribed mass in the soft tissue adjacent to the humerus. The mass contains peripheral areas of brightness on the x-ray. Over the next year this mass gradually resolves. Which of the following terms best describes the changes described? a. dysplasia b. hyperplasia c. hypertrophy d. metaplasia e. neoplasia

METAPLASIA

A 43-year-old man has complained of mild burning substernal pain following meals for the past 3 years. Upper GI endoscopy is performed and biopsies are taken of an erythematous area of the lower esophageal mucosa 3 cm above the gastroesophageal junction. There is no mass lesion, no ulceration, and no hemorrhage noted. The biopsies show the presence of columnar epithelium with goblet cells. Which of the following mucosal alterations is most likely represented by these findings? a. dysplasia b. hyperplasia c. carcinoma d. ischemia e. metaplasia

METAPLASIA

A 44-year-old woman has had congestive heart failure for the past 4 years. She develops a fever that persists for over a week. On physical examination, a heart murmur is present. Her temperature is 38.4°C. Laboratory studies show a blood culture positive for Streptococcus, viridans group. An echocardiogram reveals a 1 cm vegetation on the superior aspect of her mitral valve. Which of the following pathologic changes is most likely present in her mitral valve? a. passive congestion b. necrosis c. extensive edema d. granulomatous inflammation e. dystrophic calcification

NECROSIS

A 17-year-old adolescent receives whole body radiation as part of a preparatory regimen for bone marrow transplantation to treat acute lymphocytic leukemia. Which of the following cells and tissues in the body is most likely to remain unaltered by the effects of this therapeutic radiation? a. primary follicles of ovary b. small intestinal epithelium c. erythropoietic cells of bone marrow d. spermatogonia of testicular tubules e. neurons of cerebral cortex

NEURONS OF CEREBRAL CORTEX

A 56-year-old woman has smoked 2 packs of cigarettes per day for the past 35 years. She has had a chronic cough for the past 8 years, but recently has noted increased sputum production. On physical examination she has a few crackles auscultated best over the lung bases. Bronchoscopy with biopsy is performed. The biopsy reveals bronchial epithelium with squamous metaplasia. Which of the following statements represents the best interpretation of these findings? a. physiologic process of aging b. irreversible, even if she stops smoking c. metastases to the lung d. risk for infection e. thromboembolism with infarction

RISK FOR INFECTION

A 20-year-old man is involved in a motor vehicle accident which results in multiple blunt trauma and lacerations to his lower extremities. The left femoral artery is lacerated, and he incurs extensive blood loss and remains hypotensive for hours during transport to the emergency department. On admission, his hematocrit is 12%. Which of the following tissues is most likely to withstand the impact of these events with the least damage? a. skeletal muscle b. intestinal epithelium c. retina d. cerebral cortex e. renal tubules

SKELETAL MUSCLE

A 54-year-old man has sudden onset of severe, sharp chest pain with diaphoresis and dyspnea. On physical examination he has tachycardia with an irregular heart rhythm. Electrocardiographic changes suggest the possibility of focal myocardial damage involving the left lateral ventricular wall. Which of the following laboratory tests on the patient's serum is most useful in this situation? a. total cholesterol b. troponin I c. triglyceride d. lipase e. sedimentation rate

TROPONIN I

A 29-year-old man goes on a snorkeling trip to Looe Key Marine Sanctuary and later spends time on the beach at Bahia Honda State Park. The next day he has a darker complexion. His skin does not show warmth, erythema, or tenderness. His skin tone fades to its original appearance within a month. Which of the following substances contributes the most to the biochemical process leading to these skin changes? a. iron oxide b. lipofuscin c. tyrosine d. homogentisic acid e. glycogen

TYROSINE