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Digestive System—Gastroenterology and Nutrition (23 test)
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1. A 2-year-old African American girl has been healthy until she developed a severe gastroenteritis with progressive sleepiness and On presentation to her pediatrician, she has obvious signs of dehydration with no tears on crying, dry mucous membranes, tenting of her skin (retention of a skin fold when pinched), and lack of urination. Her respiratory rate is normal and her lips pink, suggestive of good aeration. Initial laboratory values indicate a low glucose with normal electrolyte values in mEq/L (sodium 140, potassium 4.5, chloride 110) except for bicarbonate (8, normal 20-28) and pH (7.1). She does not have glucose or ketones in her urine by color tests. The clinical scenario and electrolyte values are most consistent with which of the following?
- A first episode of diabetes mellitus
- Respiratory acidosis due to lethargy and poor breathing
- Respiratory acidosis suggestive of a toxic ingestion
- Metabolic acidosis with increased anion gap suggesting buildup of a negatively charged metabolite
- Metabolic acidosis without increased anion gap suggesting high ammonium ion
2. A firstborn Caucasian male infant does well in the nursery but seems to have a reaction to cereal, introduced at age 6 weeks. The infant begins vomiting severely, often spewing vomitus across the crib (projectile vomiting). Concern about food allergy persists until an experienced surgeon sits with her hand over the infant’s stomach for 20 minutes at the bedside, feeling a small oval shape that has been described as an olive. The surgeon obtains electrolytes and blood gases preparatory to Which of the combinations of laboratory results below and their interpretations are most likely for this infant?
- ↓ Pco2, normal bicarbonate, normal chloride, ↑ pH—pure respiratory alkalosis
- ↓ Low Pco2, ↓ low bicarbonate, ↓ low pH, ↓ low chloride—compensated metabolic acidosis
- Normal Pco2, ↓ low bicarbonate, ↓ low pH, normal chloride—pure metabolic acidosis
- ↑ High Pco2, normal bicarbonate, low pH, normal chloride—pure respiratory acidosis
- Normal Pco2, high bicarbonate, ↑ high pH, ↓ low chloride—pure metabolic alkalosis
3. A 2-year-old Arabic boy presents with a large liver and slow growth. His development is normal, and a fasting glucose level is 45 mg/dL (normal 60-100). A mild form of glycogen storage disease is suspected and liver biopsy obtained that shows increased Assay of glycogen phosphorylase, deficiency of which can cause one form of glycogen storage disease (MIM*232700), is performed. The specific activity of glycogen phosphorylase is 2.5 units/mg homogenate protein in the patient compared to 24 units/mg homogenate protein in control liver. Which of the following indicates the correct inheritance and is the correct conclusion based on this information?
- Autosomal dominant, the yield of enzyme from liver tissue is greater than 80%.
- Autosomal recessive, the enzyme is deficient in this patient’s
- Autosomal recessive, the enzyme is purified almost 10-fold in the
- Autosomal dominant, the enzyme has undergone structural alteration in the
- Autosomal recessive, the enzyme has been activated in the
4. A 2-year-old caucasian girl presents with mildly enlarged liver, history of low blood sugar (hypoglycemia) on several occasions, and growth just below the third percentile for Evaluation for glycogen storage disease includes glycogen phosphorylase enzyme assay, which is low-normal and does not increase with addition of cyclic AMP. Which of the following is most likely?
- Glycogen phosphorylase is activated by a cyclic AMP-regulated enzyme that is deficient in the
- Glycogen phosphorylase is an allosteric enzyme regulated by a cyclic AMP binding site that is mutated in the
- Glycogen phosphorylase gave a false normal value in the patient because it was not properly diluted to give excess
- Glycogen phosphorylase is subject to feedback inhibition by its product cyclic AMP
- Glycogen is a complex substrate, so a linear relation of enzyme amount and activity cannot be
5. Digestive enzymes such as pepsin, trypsin, and chymotrypsin are synthesized as inactive precursors. What are the preproteins of the active enzymes termed?
6. A previously normal 2-month-old caucasian girl is evaluated because of jittery spells (trembling, irritability) several hours after A low blood glucose value is noted, and physical examination demonstrates a liver edge some two finger-breadths below the right costal margin. Percussion of the right chest and abdomen confirms that the liver width is slightly enlarged. Hospital testing reveals that the infant can increase her blood glucose after breast-feeding but that it is not maintained at normal levels 3 to 4 hours after feeding. Which of the following is the most likely diagnosis?
- Intestinal malabsorption of lactose
- Galactosemia with inability to convert lactose to glucose
- Fructosemia with inability to liberate sucrose from glucose
- Glycogen storage disease
- Diabetes mellitus with inability to maintain glucose
7. Following a fad diet meal of skim milk and yogurt, a 15-year-old African American adolescent experiences abdominal distention, nausea, cramping, and pain followed by a watery This set of symptoms is observed each time the meal is consumed. Which of the following is the most likely diagnosis?
- Lactase deficiency
- Maltose deficiency
- Sialidase deficiency
- Lipoprotein lipase deficiency
8. A 2-day-old caucasian girl begins vomiting after feeding, becomes severely jaundiced, has liver disease, and cloudy lenses of the eyes suggestive of cataracts. Treatment for possible sepsis is initiated, and the urine is found to have reducing substances. A blood screen for galactosemia (MIM*230400) is positive, and lactose- containing substances are removed from the Lactose is toxic in this case because of which of the following?
- Excess glucose accumulates in the
- Galactose is converted to the toxic substance galactitol (dulcitol).
- Galactose competes for glucose during hepatic glycogen
- Galactose is itself toxic in even small
- Glucose metabolism is shut down by excess
9. A 6-month-old Hispanic female infant begins having trembling with irritability (jittery spells) and vomiting after certain meals including baby food containing fruits. She showed a falloff in growth when pureed fruits and vegetables were introduced at age 4 months. She is hospitalized for evaluation, and blood obtained for testing when she exhibits tremors and irritability after a typical Serum glucose is 40 g/dL (normal 60-100) and plasma lactate 35 g/dL (normal 5-20), causing her physician to suspect hereditary fructose intolerance (MIM*229600—a deficiency of the enzyme aldolase B). The symptoms and serum abnormalities of this disease are due to which of the following?
- Accumulation of hexose phosphates, phosphate and ATP depletion, defective electron transport, and glycogen phosphorylase inhibition
- Accumulation of triose phosphates, phosphate and ATP excess, defective glycolysis, and glycogen synthase inhibition
- Accumulation of triose phosphates, phosphate and ATP depletion, defective electron transport, and glycogen synthase inhibition
- Accumulation of hexose phosphates, phosphate and ATP depletion, defective electron transport, and glycogen phosphorylase stimulation
- Accumulation of hexose phosphates, phosphate and ATP excess, defective electron transport, and glycogen phosphorylase stimulation
10. A 6-month-old Caucasian boy becomes ill after fruits and vegetables are added to his diet of breast Mother feels that he used to become colicky when she ate fruit, although her pediatrician did not think this was significant. After 1 month of these new foods, the child has stopped gaining weight and the pediatrician feels an enlarged liver. Initial blood tests show a mild acidosis (pH 7.2) with increased lactic acid and low blood glucose. The urine reagent strip test reaction is positive for reducing substances in the urine, but the glucose oxidase test is negative for glucosuria. A glycogen storage disease is suspected, and a liver biopsy dose shows mildly increased glycogen with marked cellular damage suggestive of early cirrhosis. Assays for type IV glycogen storage disease are negative, and the initial frozen urine sample is reanalyzed and found to contain fructose. The most likely diagnosis and the reasons for hypoglycemia and glycogen accumulation is which of the following?
- Hereditary fructose intolerance with inhibition of liver phosphorylase
- Hereditary fructose intolerance with inhibition of glycogen synthase
- Essential fructosuria with inhibition of glycogen synthase
- Essential pentosuria with inhibition of liver phosphorylase
- Essential fructosuria with allosteric stimulation of glycogen synthase
11. Fasting is observed in many religions and occurs with food shortages or fad diets. A man goes on a hunger strike and confines himself to a liquid diet with minimal Which of the following would occur after 4 to 5 hours?
- Decreased cyclic AMP and increased liver glycogen synthesis
- Increased cyclic AMP and increased liver glycogenolysis
- Decreased epinephrine levels and increased liver glycogenolysis
- Increased Ca2+ in muscle and decreased glycogenolysis
- Decreased Ca2+ in muscle and decreased glycogenolysis
12. Hurricane survivors are evacuated from a back alley where they have been trapped for 4 days by Three adults have diarrhea with bloody stools, and a 5- month-old female infant is comatose with severe diarrhea and dehydration. Stool cultures reveal cholera; the adults were treated with tetracycline, and the infant with erythromycin to avoid injury to developing teeth. cholera toxin causes massive and often fatal diarrhea by which of the following mechanisms?
- Inactivating Giprotein
- Irreversibly activating adenylate cyclase
- Locking Gs protein into an inactive form
- Rapidly hydrolyzing G protein GTP to GDP
- Preventing GTP from interacting with G protein
13. A 2-year-old Caucasian girl presents to her pediatrician with a flulike She has sparse hair and a mild falloff in growth attributed to picky eating characteristic for this age. The pediatrician is concerned about her extreme lethargy with signs of dehydration and admits her to the hospital. Blood tests show a pH of 7.1, glucose of 40 mg/dL (normal 60-100), bicarbonate of 12 mEq/L (normal 16-24), and a white blood cell count of 4500 cells per cubic millimeter (normal 6-17,000). The metabolic acidosis and low white count raise concern for a metabolic disease, and a plasma acylcarnitine profile with total and free carnitine levels are ordered. Because children with organic acidemias or fatty acid oxidation disorder can have abnormal acylcarnitines that deplete free carnitine, intravenous carnitine is started at 100 mg/kg per day. Carnitine deficiency with decreased translocation of fatty acids into mitochondria will cause which of the following?
- Inhibition of ATP synthase
- Depletion of NADH needed for oxidation
- Inhibition of cytochrome oxidase
- Inhibition of electron transfer from cytochromes to coenzyme Q
- Uncoupling of oxidation from phosphorylation
14. A 40-year-old Caucasian female of fair complexion is admitted for evaluation of acute vomiting with abdominal The episode began the night before, after a fatty meal, and she has noted her stools are a peculiar gray white color. Abdominal examination is difficult because she is obese, but she exhibits acute tenderness in the right upper quadrant and has pain just below her left shoulder blade. Interference with which aspect of porphyrin metabolism best accounts for the white stools?
- Sterile gut syndrome with defective bilirubin oxidation
- Excess oxidation of bilirubin to urobilinogen
- Heme synthesis defect, causing increased bilirubin clearance
- Bile duct excretion of bilirubin with oxidation to stercobilin
- Excess reabsorption of urobilinogen with excess urobilin
15. A 2-year-old Caucasian boy presents with neonatal meconium ileus, chronic cough and bronchitis, growth failure, and chronic diarrhea with light-colored, foul- smelling A deficiency of which of the following vitamins should be considered?
- Vitamin A
- Vitamin C
- Vitamin B1
- Vitamin B2
- Vitamin B6
16. A 35-year-old Caucasian male is evaluated for epilepsy that appeared in his teenage He has had reasonable control with antiepileptic medications but recently has had seizures in the late evening. He also has chronic indigestion that requires daily proton pump inhibitors and was noted to have calcium deposits in his lungs when recently evaluated for a respiratory infection. His physician recognizes symptoms of multiple endocrine neoplasia type I (MIM*131100) that involves hypersecretion of multiple pancreatic hormones plus hyperparathyroidism. Which of the following options describes the peptide hormone that regulates stomach acid and the hormone that opposes its secretion?
- Cholecystokinin, gastrin
- Gastrin, insulin
- Insulin, secretin
- Secretin, insulin
- Gastrin, secretin
17. A 5-day-old Caucasian boy is kept in the nursery because of persisting neonatal jaundice with atypical elevation of direct-reacting, conjugated bilirubin. Further investigation indicates that the infant has liver disease with simultaneous elevation of liver A sibling died with similar symptoms, and an inborn error of bile acid metabolism is suspected (eg, intrahepatic cholestasis with defective conversion of trihydroxycoprostanic bile acid to cholic acid—MIM*214950). Which of the following compounds is normally used to conjugate bile acids?
- Glucuronic acid
18. An 8-year-old Caucasian boy is evaluated for mild short stature and night-time awakening feeling irritable and His mother’s brother is said to have a storage disease that made him short. Physical examination reveals a palpable liver edge about two finger-breadths below the right costal margin and a span of 7 cm by percussion—evidence of hepatomegaly. Fasting values are obtained for glucose (50 mg/dL; 60-100 normal, cholesterol 220 mg/dL; <199 normal for age, uric acid 7.5 mg/dL; 2.5-6 normal) and a diagnosis of X-linked glycogen storage disease is considered (type IXa-MIM*306000-involving liver phosphorylase kinase deficiency). Nighttime cornstarch infusion feedings are begun based on knowledge that which of the following is the major source of blood glucose during fasting?
- Dietary glucose from the intestine
- Hepatic glycogenolysis
- Muscle glycogenolysis
- Glycerol from lipolysis
19. A 14-year-old African American adolescent presents with abdominal discomfort, abdominal fullness, excess gas, and weight Blood glucose, cholesterol, and alkaline phosphatase levels are normal. There is no jaundice or elevations of liver transaminases. The stool tests positive for reducing substances. Which of the following is the most likely diagnosis?
- Diabetes mellitus
- Nontropical sprue
- Milk intolerance
20. A couple has three girls, the last of whom is affected with cystic The first-born daughter marries her first cousin—that is, the son of her mother’s sister—and they have a son with cystic fibrosis. The father has a female cousin with cystic fibrosis on his mother’s side. Which of the following pedigrees represents this family history?
- Diagram A
- Diagram B
- Diagram C
- Diagram D
- Diagram E
- Diagram F
- Diagram G
- Diagram H
21. A couple present for genetic counseling because three of their first four children have had pyloric stenosis, a narrowing of the valve between stomach and duodenum that presents with severe vomiting and loss of gastric hydrochloric acid (hypochloremic alkalosis). When parents with three affected children have a higher recurrence risk than parents with one affected child, the disease in question is likely to exhibit which of the following modes of inheritance?
- Autosomal dominant inheritance
- Autosomal recessive inheritance
- X-linked recessive inheritance
- X-linked dominant inheritance
- Multifactorial determination
22. A newborn Caucasian girl presents with poor feeding, vomiting, jaundice, and an enlarged The urine tests positive for reducing substances, indicating the presence of sugars with aldehyde groups. Which of the following processes is most likely to be abnormal?
- Conversion of glucose to galactose
- Conversion of lactose to galactose
- Conversion of activated galactose to activated glucose
- Excretion of glucose by the kidney
- Excretion of galactose by the kidney
23. The frequency of galactosemia is approximately 1 in 40,000 live The frequency of the carrier state can be calculated as which of the following?
- 1 in 50 live births
- 1 in 100 live births
- 1 in 200 live births
- 1 in 500 live births
- 1 in 1000 live births