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Biomedical subjects

J N Isenberg

Publications and source records attributed to J N Isenberg.

At least 19 recordsLinked to original sources
PubMed1994

Determinants of free-living energy expenditure in normal weight and obese women measured by doubly labeled water.

Total free-living energy expenditure (TEE) was measured in 9 normal weight controls and 5 obese women using the doubly labeled water (DLW) method. Resting energy expenditure (REE) and the thermic effect of food (TEF) were measured by indirect calorimetry and the energy cost of physical activity (PA) calculated by deduction, in order to quantify the components and identify determinants of free-living TEE. Although REE was quantitatively the major component of TEE in both groups, PA best explained the variability, contributing 76% to the variance in free-living TEE. The obese women had elevated values for TEE (12397 +/- 2565 vs. 8339 +/- 1787 kJ/d, mean +/- SD; p < 0.005), compared with the control women. PA (5071 +/- 2385 vs. 2552 +/- 1452; p < 0.05) and REE (6393 +/- 678 vs. 5084 +/- 259; p < 0.0005) were also raised in the obese, whereas TEF was not significantly different between the groups, accounting for 7.6% of energy expenditure for the obese and 8% for the control subjects. Body weight was the single best determinant of mean daily free-living TEE across both groups. We conclude that PA and body weight are the main determinants of free-living TEE.

Adult↗
PubMed1988

Gastroesophageal reflux: how much imaging is required?

The authors present a protocol for the selection of imaging studies for infants suspected of gastroesophageal reflux. In most cases, only a single imaging procedure is required. Three groups of patients are considered: those suspected of an esophageal or postgastric obstruction who require a barium GI series; those who appear to have reflux and a possible gastric obstruction in whom sonographic study of the gastric outlet is advised; and those suspected of aspirating in whom the possibility of reflux is studied by scintigraphy. Esophagoscopy and other studies are reserved for those refractory to therapy.

Gastroesophageal Reflux↗
PubMed1987

Application of a new test for vitamin E deficiency to cystic fibrosis.

Cystic fibrosis patients with pancreatic insufficiency are at risk for the development of vitamin E deficiency. We report here the outcome of screening 13 cystic fibrosis patients with conventional descriptive measures of vitamin E status and a new functional test. The results were compared with those from age appropriate controls. Nine patients were found to be vitamin E sufficient based upon normal plasma vitamin E levels, the ratio of plasma vitamin E to total plasma lipids, and normal levels of in vitro erythrocyte malondialdehyde formation, the new functional measure of vitamin E status. Four patients considered vitamin E deficient, based upon low plasma vitamin E levels and plasma vitamin E to total plasma lipid ratios, demonstrated increased erythrocyte malondialdehyde formation in vitro when compared to age-matched controls. Since limited reference data in children are available to define normal plasma vitamin E levels and plasma vitamin E to total plasma lipid ratios, we suggest that for cystic fibrosis patients the functional in vitro malondialdehyde formation test may be a better measure of vitamin E status than static plasma levels.

Adolescent↗
PubMed1987

Carbohydrate malabsorption is minimal in school-age cystic fibrosis children.

Fifteen school-age cystic fibrosis children, participating in a year-long nutritional management study, were hospitalized at six-month intervals for balance studies during which they continued "free-choice" diets and their usual enzyme supplementation. Stools were analyzed for fat and protein by conventional methods and for carbohydrate using a recently validated anthrone method. Despite persistent fat and protein malabsorption, less than 1% of ingested carbohydrate was lost intact in the stools. Comparison of baseline and placebo balance studies showed fecal excretion of carbohydrate to be independent of intake, in contrast to the fat and protein results. Using a thin-layer chromatography method capable of detecting microgram quantities of urinary organic acids, no short-chain fatty acids were detected in the stool. Further exploration of carbohydrate as a dietary energy source for this patient group with increased energy demands should be pursued.

Adolescent↗
PubMed1986

A cobalamin metabolic defect with homocystinuria, methylmalonic aciduria and macrocytic anemia.

We have identified a patient with methylmalonic aciduria and homocystinuria due to a defect in cobalamin metabolism of the cb1C type mutant. At the time of admission at eight months of age the patient was malnourished, hypotonic and had macrocytic anemia. Neonatal screening for hypermethioninemia associated with homocystinuria had been normal. Serum vitamin B12 was markedly increased and folate concentration was above normal, as were urinary homocystine and methylmalonic acid. The patient had abnormal brain stem auditory and visual evoked potentials. Fibroblast activity of N5-methyltetrahydrofolate: homocysteine methyltransferase was reduced to approximately 10% of concurrent controls. A course of therapy with hydroxocobalamin resulted in a 90% reduction in excretion of methylmalonic acid and normalization of the evoked potentials. These studies support the efficacy of hydroxocobalamin therapy in this disease, suggest that methylmalonic acid may be the most appropriate metabolite to monitor for therapeutic response, and in importance of electrophysiologic studies in character in objectively monitoring the response to treatment metabolic disease.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1986

Erythrocyte lipid alterations in pediatric cholestatic liver disease: relationship to serum bile acids.

Chronic pediatric cholestatic liver disease is accompanied by an elevated erythrocyte membrane cholesterol/phospholipid molar ratio. Since bile acids are known to affect erythrocyte membrane integrity, we sought to determine what relationship existed between serum bile acid concentrations and the observed alterations in erythrocyte membrane lipids. Ten children with chronic cholestasis (2 months-3 1/2 yrs) were evaluated a total of twenty-two times. For all studies a reliable correlation between erythrocyte membrane cholesterol and phospholipid was noted (r = 0.88, p less than 0.001). When total serum bile acids exceeding 100 mumol/L were excluded, a strong relationship between serum bile acids and erythrocyte cholesterol/phospholipid molar ratio was noted (r = 0.61, p less than 0.03). The results suggest that with mild to moderate cholestasis changes in serum bile acids influence erythrocyte membrane lipid composition with parallel increases in cholesterol and phospholipid.

Bile Acids and Salts↗
PubMed1985

Erythrocyte malondialdehyde release in vitro: a functional measure of vitamin E status.

The definition for a sufficient vitamin E level has often been based on population studies that established the normal range of values for fasting plasma or serum vitamin E and more recently for vitamin E to total lipid ratios. These endpoints for vitamin E replacement strategies may not be readily achievable, particularly in the cholestatic patient for whom it is often impossible to reach and sustain normal levels even with massive doses of vitamin E. Vitamin E is believed to function as an antioxidant in vivo protecting membranes from lipid peroxidation. Malondialdehyde (MDA), a product of polyunsaturated fat peroxidation, was measured as the thiobarbiturate derivative in the supernatant following incubation of erythrocytes in hydrogen peroxide. The two different incubation conditions described here and the subsequent measurement of MDA appear to provide a sensitive functional assessment of vitamin E status. The clinical utility of this assay, which requires just 1.5 to 2.0 ml of whole blood, was demonstrated by comparing the percent of total MDA released from individuals regarded as vitamin E sufficient by conventional methods with vitamin E deficient subjects. The release of MDA from erythrocytes from vitamin E deficient subjects was clearly greater (44.1 +/- 18.8% vs 2.0 +/- 1.8%) than for control subjects (p less than 0.001).

Adolescent↗
PubMed1985

Erythrocyte lipid alterations in pediatric cholestatic liver disease: spur cell anemia of infancy.

Spur cell anemia of liver disease is a hemolytic process characterized by spiculated erythrocytes and an elevated red cell membrane cholesterol/phospholipid (C/PL) molar ratio. This form of anemia is associated almost exclusively with adults in the advanced stages of alcoholic cirrhosis. We were therefore surprised to identify two unrelated infants with cholestatic liver disease and hemolytic anemia who had spiculated erythrocytes as the major abnormal cell form on peripheral smear. Erythrocyte membrane cholesterol and phospholipid determinations from these patients were compared with six infants with extrahepatic biliary atresia and target-shaped erythrocytes and with five normal adults. Erythrocyte C/PL molar ratio distinguished target cells from normal erythrocytes (p less than 0.01). The spur cell patients' erythrocyte C/PL molar ratios were clearly greater than either target cell patients or normal controls (1.30 vs. 1.02 vs. 0.84). Both patients' spur cell anemia resolved and target cells became the major abnormal erythrocyte form. These studies identify a transient form of spur cell anemia associated with infantile cholestatic liver disease. The factors leading to the formation of spur cell anemia in infancy require further investigation.

Acanthocytes↗
PubMed1984

Stimulation of bile output by gastrointestinal hormones following portoenterostomy for biliary atresia.

For biliary atresia portoenterostomy with externally draining conduit provides a model for quantitation of hepatic excretory function and for assessment of the physiologic response of the intrahepatic biliary system to gastrointestinal hormones in a human hepatopathologic condition. Four patients with biliary atresia were serially evaluated from 2 weeks to 43 months following total bile diverting portoenterostomy. A fifth patient with no bile flow provided a control for these studies. The pattern of Rose Bengal excretion for three patients with a satisfactory clinical course was different from that of a fourth patient with highly variable flow and persistent cholestasis. Marked volume and bicarbonate concentration increases in bile were noted 30 to 45 minutes after secretin infusion but only in the four patients with bile flow. The volume response to glucagon was more diffuse. Bilirubin and bile acid concentrations decreased in the stimulated bile flow periods and hourly outputs of these cholephils were not increased above basal. During two intervals of low bile output, secretin markedly increased bile flow in the patient with persistent cholestasis establishing the patency of the hepatoenteric anastomosis (functional obstruction) in contrast to the lack of secretin response in the control (structural obstruction).

Bile↗
PubMed1983

Effect of short-term cimetidine administration on fecal bile acid losses in cystic fibrosis.

Eight children with cystic fibrosis and exocrine pancreatic insufficiency were voluntarily hospitalized in a clinical research setting so that diet and enzyme supplements could be well controlled for consecutive 72-h balance studies. We previously reported on these patients, as part of a larger study group, because they showed significantly reduced fecal losses of fat and nitrogen at the highest dose of cimetidine added to the otherwise constant regimen. Analysis of specimens from this same study shows a cimetidine-related reduction in fecal bile acid loss. Numerous variables thought to influence fecal bile acid loss were closely controlled and/or measured in this clinical study setting. In order to potentially learn more about this complex phenomenon, we carried out a stepwise regression analysis of the data which indicated that half of the variance in fecal bile acid loss is still unaccounted for by the five "independent" variables tested in the regression. However, in this variance analysis system cimetidine assumes a larger relative role in modulating bile acid loss than it does in fecal losses of fat and nitrogen.

Adolescent↗
PubMed1982

Gastric acid hypersecretion in cystic fibrosis.

Increased basal and/or pentagastrin-stimulated gastric acid secretion was observed in 31 of 40 cystic fibrosis (CF) patients as compared to 13 age-matched control volunteers. Fasting serum gastrin level for 20 CF patients of 67.7 +/- 11.1 pg/ml (ranging from 10 to 145 pg/ml) was normal. Meal-stimulated serum gastrin concentrations were not significantly higher for seven CF patients as compared to nine normal subjects. In a rat bioassay, serum extracts from six CF patients produced gastric acid secretion comparable to 250 ng/ml of pentagastrin; significantly (p less than 0.01) greater than the responses produced by serum extracts from six normal subjects. There was no significant correlation of severity of pulmonary disease or steatorrhea with acid secretory results. Fourteen of 16 CF patients biopsied had evidence of proximal small intestinal injury which correlated with basal acid output elevation. Gastric acid hypersecretion in CF patients is due to nongastrin secretagogues and is a cause of proximal small intestinal injury.

Adolescent↗
PubMed1979

The effect of cimetidine on maldigestion in cystic fibrosis.

Ten patients (6 to 27 years of age) who had severe pancreatic exocrine insufficiency due to cystic fibrosis were studied to determine whether cimetidine would improve dietary fat and nitrogen absorption. When a constant diet was consumed and oral pancreatic enzymes were administered, the addition of cimetidine (150 or 200 mg taken orally one-half hour before meals) signficantly reduced fecal fat excretion from 25.3 +/- 2.9 to 17.3 +/- 2.1 gm/24 hours and fecal nitrogen excretion from 4.5 +/- 0.6 to 3.4 +/- 0.5 gm/24 hours (P less than 0.05). Lower doses of cimetidine resulted in less significant reductions of steatorrhea and azotorrhea. Cimetidine may be a useful adjunct to oral pancreatic enzyme therapy in patients with cystic fibrosis who continue to have steatorrhea and azotorrhea with enzyme therapy alone.

Adolescent↗