Search PubMed⌕ Search

Biomedical subjects

C H Halsted

Publications and source records attributed to C H Halsted.

At least 37 records · Page 2Linked to original sources
PubMed1994

Development of malabsorption and nutritional complications in simian immunodeficiency virus-infected rhesus macaques.

OBJECTIVE: To assess the development and cause of malabsorption in rhesus macaques following experimental simian immunodeficiency virus (SIV) infection and to evaluate its impact on nutritional status. DESIGN: Clinical malabsorption tests and serial jejunal aspirates and biopsies were obtained from nine SIV-infected and three uninfected animals prior to infection and at 1, 2, 4, 8, 12, 24, 40 and 52 weeks postinoculation. METHODS: Malabsorption was measured by sucrose breath hydrogen (H2) analysis and blood assay of D-xylose. Digestive enzyme activity was determined in jejunal mucosal homogenates. Bacterial and protozoal flora were determined in jejunal aspirates. Nutritional assessment was evaluated using specific blood micronutrient values. Cellular targets of SIV in the jejunum were determined by combined in situ hybridization and immunohistochemistry. RESULTS: Eight out of nine SIV-infected monkeys, including asymptomatic animals, exhibited malabsorption by either increased breath H2 and/or decreased blood D-xylose. All animals that died of AIDS had diarrhea, D-xylose malabsorption and decreased sucrase activity. Significant changes in nutritional status were associated with malabsorption. Bacterial overgrowth was not considered to be a cause of malabsorption. Histopathological biopsy findings included dilated villus lacteals, excessive cellular debris, lymphoplasmocytic infiltrates and cytoplasmic vacuoles in crypt epithelial cells. SIV-infected T cells and macrophages were detected as early as 1 week postinoculation. CONCLUSIONS: SIV-associated malabsorption can occur prior to clinical complications of disease. Severe intestinal complications are associated with malabsorption and malnutrition in the terminal stages of AIDS. The high proportion of macaques experiencing malabsorption without detectable pathogens, suggests an enteropathogenic role for SIV.

Animals↗
PubMed1994

Selective reduction of delta 6 and delta 5 desaturase activities but not delta 9 desaturase in micropigs chronically fed ethanol.

This study investigated the mechanism by which chronic ethanol feeding reduces arachidonate and other highly unsaturated fatty acids in pig liver phospholipids. Five micropigs were fed a diet providing 89 kcal/kg body wt for 12 mo, with ethanol and fat as 40 and 34% of energy, respectively. Five control pigs were pairfed corn starch instead of ethanol. The activities of delta 6 and delta 5 desaturases (expressed as microsomal conversion of precursor to product) in liver from ethanol-fed pigs were reduced to less than half that of controls, whereas the activity of delta 9 desaturase was unaffected in the ethanol group. delta 5 Desaturase activity showed positive correlation with the abundance of its products in liver total phospholipids and microsomes in the ethanol group, but not in the controls. Correlation between delta 6 desaturase activity and its products showed similar pattern to that of delta 5 desaturase, but did not reach statistical significance. No difference was observed between the two groups in coenzyme A concentration in the liver. These results suggest that the selective reduction of delta 6 and delta 5 desaturase activities, not the microsomal electron transport system, are directly responsible for the altered profile of liver phospholipids.

Alcoholism↗
PubMed1994

Effects of ethanol feeding on liver, kidney and jejunal membranes of micropigs.

The micropig model of chronic alcoholism was used to study the relationship of lipid composition and physical properties in three different tissue membranes from the same animals. Ethanol feeding reduced membrane anisotropy, as measured with the diphenylhexatriene probe, in liver plasma and kidney brush-border membranes but not in jejunal brush-border membranes. Preincubation with ethanol reduced anisotropy in each of the three control membranes, whereas all three membranes from the ethanol-fed group were relatively tolerant to the acute effect of ethanol. In liver and kidney membranes, ethanol feeding increased levels of linoleic (18:2 omega 6) acid and decreased levels of arachidonic (20:4 omega 6) and docosahexaenoic (22:6 omega 3) acids and their specific double-bond positions, consistent with reduced activities of delta 6 and delta 5 fatty acid desaturases. In liver and kidney membranes, anisotropy parameters and the acute effect of ethanol correlated inversely with levels of linoleic acid and directly with levels of arachidonic and docosahexaenoic acids and their specific double bonds. Levels of docosahexaenoic acid correlated with the acute effect of ethanol in all three membranes. Phospholipid fatty acid profiles were similar in jejunal brush-border membranes and terminal bile samples, suggesting that the effects of ethanol on jejunal fatty acids and physical properties are modulated by intraluminal biliary phospholipids. The effect of ethanol on anisotropy could not be attributed to changes in membrane cholesterol/phospholipid ratios. These studies affirm the value of this new animal model of chronic alcoholism and provide comprehensive evidence for the central role of fatty acid desaturation in the membrane-associated effects of ethanol exposure.

Administration, Oral↗
PubMed1993

Centrilobular distribution of acetaldehyde and collagen in the ethanol-fed micropig.

We established a new animal model of alcoholic liver disease in the micropig, a species that consumes ethanol voluntarily in the diet. Ten micropigs were pair-fed diets containing 40% of calories as ethanol or cornstarch with identical amounts of fat, protein and micronutrients for 12 mo. Liver histopathology in the ethanol-fed pigs included steatonecrosis in all five and interstitial and perivenous fibrosis in three. Electron microscopy showed Ito-cell transformation with perisinusoidal collagen accumulation. Acetaldehyde adducts were found by immunofluorescence in the centrilobular region and were focused in perivenous zone 3 of all ethanol-fed animals. Protein and triglyceride levels were increased, whereas vitamin A and iron levels were decreased in liver homogenates from ethanol-fed animals. Thus, in this new animal model of alcoholism, ethanol feeding produced the features of alcoholic liver disease concurrent with hepatic deficiency of selected nutrients. Histological and immunofluorescent studies provide in vivo evidence that perivenous collagen deposition is linked to ethanol metabolism and acetaldehyde production.

Acetaldehyde↗
PubMed1993

The body composition and lipid metabolic effects of long-term ethanol feeding during a high omega 6 polyunsaturated fatty acid diet in micropigs.

Our previous research with miniature pigs has shown that long-term ethanol feeding with a low-fat diet decreases arachidonic acid (20:4 omega 6) levels in multiple tissues, but we did not find significant liver pathology. In this study, we investigated the effect of ethanol feeding with high dietary linoleic acid (18:2 omega 6) on tissue fatty acid (FA) profiles and body composition. Five Yucatan micropigs were fed 370 kJ (89 kcal)/kg body weight of a diet containing ethanol and fat as 40% and 34% of energy, respectively; five control pigs were pair-fed corn starch in place of ethanol. Corn oil, 61% 18:2 omega 6, supplied most of the dietary fat. Liver biopsies were performed at baseline (n = 2 per group) and at three other time points (n = 5 per group). Phospholipid (PL) FA levels were measured by thin-layer and gas chromatography. Body composition was analyzed by underwater weighing of carcasses. Body composition analysis demonstrated a marked reduction of carcass fat in the ethanol group, but no significant reduction of carcass lean weight after 12 months. In liver PLs, the ethanol group showed decreased 20:4 omega 6 and docosahexaenoic acid (22:6 omega 3) after 1 month. While the decreased 20:4 omega 6 remained constant after 1 month, 22:6 omega 3 showed a progressive decrease up to 12-months, resulting in a continuous decrease of the omega 3/omega 6 FA ratio. This slowly progressive decrease in the omega 3/omega 6 ratio in liver PLs with ethanol feeding may have enhanced the inflammatory response in the liver, contributing to liver pathology. Body composition results indicate marked wasting of energy in the ethanol group.

Analysis of Variance↗
PubMed1993

Biennial survey of physician clinical-nutrition training programs.

This is the fourth survey of physician clinical-nutrition training programs. As in previous reports, current fellowship training programs were identified, descriptive information obtained, and program content surveyed. In addition, a questionnaire developed by the American Board of Nutrition Committee on Fellowship Training Programs was used to determine the degree of emphasis given to content in the areas of basic nutrition science, clinical applications, and research training. Among the 38 programs identified, uniform ratings of importance were found in all major topic areas. There was also uniformity in most subtopics, with minor exceptions. As expected, in the area of nutrition in the life cycle, pediatric training programs emphasized infancy and childhood whereas medical-surgical programs emphasized adulthood and aging. Alcoholism was emphasized in medical-surgical training programs whereas cystic fibrosis and inborn errors of metabolism were emphasized in pediatric programs. Nutrition in burn patients received minor emphasis in all programs. The overall uniformity of curricular content in training programs confirms the contention that clinical nutrition has a defined clinical scope and should be considered for establishment as a recognized subspecialty in American medicine.

Education↗
PubMed1993

Simian immunodeficiency virus infection of the gastrointestinal tract of rhesus macaques. Functional, pathological, and morphological changes.

Gastrointestinal dysfunction and wasting are frequent complications of human immunodeficiency virus (HIV) infection. Nutrient malabsorption, decreased digestive enzymes and HIV transcripts have been documented in jejunal mucosa of HIV-infected patients; however, the pathogenesis of this enteropathy is not understood. Rhesus macaques infected with simian immunodeficiency virus (SIV) also exhibit diarrhea and weight loss; therefore, we investigated the use of this animal model to study HIV-associated intestinal abnormalities. A retrospective study of intestinal tissues from 15 SIV-infected macaques was performed to determine the cellular targets of the virus and examine the effect of SIV infection on jejunal mucosal morphology and function. Pathological and morphological changes included inflammatory infiltrates, villus blunting, and crypt hyperplasia. SIV-infected cells were detected by in situ hybridization in stomach, duodenum, jejunum, ileum, cecum, and colon. Using combined immunohistochemistry and in situ hybridization, the cellular targets were identified as T lymphocytes and macrophages. The jejunum of SIV-infected animals had depressed digestive enzyme activities and abnormal morphometry, suggestive of a maturational defect in proliferating epithelial cells. Our results suggest that SIV infection of mononuclear inflammatory cells in intestinal mucosa may alter development and function of absorptive epithelial cells and lead to jejunal dysfunction.

Animals↗
PubMed1992

Reduced tissue arachidonic acid concentration with chronic ethanol feeding in miniature pigs.

The effect of ethanol feeding on the essential fatty acid content of tissues has been contradictory. To define the effect, we analyzed fatty acid profiles in various tissues from five miniature pigs fed daily 105 kJ basal diet/kg body wt and 146 kJ ethanol/kg body wt, and also five control pigs pair-fed the same amount of basal diet but with corn starch substituted for ethanol. After 12 mo, biopsy samples were taken, and tissue fatty acid profiles were analyzed. In the phospholipid fraction from the ethanol group there was a uniform decrease in arachidonic acid (AA) and an increase in oleic acid in liver, serum, and muscle. AA was consistently decreased in the triglyceride fractions of liver, serum and subcutaneous adipose of the ethanol group. Possible explanations for this general reduction in tissue AA with ethanol feeding include decreased activities of delta 6 and delta 5 desaturases, and a displacement of AA from lipid fractions by other fatty acids.

Adipose Tissue↗
PubMed1991

Human immunodeficiency virus infection of enterocytes and mononuclear cells in human jejunal mucosa.

Intestinal malabsorption is a recognized cause of malnutrition in patients infected with human immunodeficiency virus. However, the relationships among human immunodeficiency virus infection, morphological changes in the intestine, and development of intestinal malabsorption are not well established. Nine patients infected with human immunodeficiency virus underwent tests of intestinal absorption and jejunal biopsies for morphometric measurements, enzyme assays, and virus detection by in situ hybridization. Steatorrhea and low lactase activities were found in more than 85% of the patients. All biopsy specimens were abnormal with reversal of the ratio of villus length to crypt depth in seven and enlarged enterocyte nuclear size in nine. Human immunodeficiency virus was detected in five jejunal biopsy specimens, within villus enterocytes of one patient who had the most severe malabsorption of the group and in four other biopsy specimens in mononuclear infiltrating cells of the lamina propria. These results suggest that human immunodeficiency virus infection of the small intestinal mucosa is an early event that is associated with altered enterocyte differentiation and function.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Functional specificity of jejunal brush-border pteroylpolyglutamate hydrolase in pig.

To determine the functional specificity of intestinal brush-border pteroylpolyglutamate hydrolase (PPH), we compared the regional location of in vivo hydrolysis of pteroyltriglutamate (PteGlu3) with the location of activity and immunoreactivity of the enzyme in the pig. After in vivo incubations, PteGlu3 hydrolytic products were recovered from intestinal segments in the jejunum but not from the ileum. Brush-border PPH activity in fractionated mucosa was 10-fold greater in the jejunum than in the ileum, whereas the activity of intracellular PPH was increased in the distal ileum. Antibodies to purified brush-border PPH identified a major protein band at 120 kDa and a minor protein band at 195 kDa in solubilized jejunal brush border. Immunohistochemistry identified the enzyme only on the brush-border surface of the jejunum, whereas an immunoblot of solubilized brush-border membranes identified brush-border PPH in the jejunum but not in the ileum. The parallel of the regional location of in vivo hydrolysis of PteGlu3 with the location of brush-border PPH activity and immunoreactivity demonstrates the functional specificity of this enzyme in folate digestion.

Animals↗
PubMed1991

Jejunal brush-border folate hydrolase. A novel enzyme.

Dietary folate, a vitamin required for DNA synthesis and cell regeneration, occurs as pteroylpolyglutamates that are hydrolyzed to pteroylglutamate during the process of intestinal absorption. Studies from our laboratory over the past 15 years have shown that jejunal brush-border folate hydrolase is essential and rate-limiting in folate absorption. Brush-border folate hydrolase activity and pteroylpolyglutamate hydrolysis are inhibited in disease and conditions associated with folate deficiency, including celiac and tropical sprue, the use of sulfasalazine to treat inflammatory bowel disease, and chronic alcoholism. Brush-border folate hydrolase is an exopeptidase located on the jejunal brush-border surface that liberates hydrolytic products of pteroylpolyglutamates in a progressive fashion, with a final release of pteroylglutamate. Subsequent steps in folate absorption include uptake by a brush-border folate-binding-protein receptor and transport across the brush-border membrane into the enterocyte. These steps are probably followed by an intracellular synthesis of pteroylglutamates for folate-dependent reactions and intracellular hydrolysis to pteroylglutamate for transport across the basolateral membrane to the portal circulation. In pigs, the active form of jejunal brush-border folate hydrolase has a molecular weight of 240 kd and is probably a homodimer of the 120-kd protein found after immunoprecipitation with specific antibody. Regulating the synthesis and expression of brush-border folate hydrolase may be critical to the availability of dietary folate.

Alcoholism↗
PubMed1991

Ethanol-induced changes in hepatic free radical defense mechanisms and fatty-acid composition in the miniature pig.

In the miniature pig, ethanol consumption has been reported to induce alterations in hepatic antioxidant defense capacity, which could result in increased risk of peroxidative damage. However, ethanol may also induce changes in membrane fatty acid composition, which could reduce the risk of peroxidative damage. This study examined lipid peroxidation, antioxidant defense and fatty acid composition in livers from miniature pigs fed ethanol in diets containing 12% of their calories as fat for 20 mo. After 12 and 20 mo of feeding, ethanol-fed pigs had higher hepatic manganese-superoxide dismutase activity, lower hepatic copper concentrations and low hepatic copper-zinc-superoxide dismutase and glutathione peroxidase activities compared with controls. Lipid peroxidation as assessed by thiobarbituric acid reacting substance assay was lower in liver homogenate and mitochondrial and microsomal fractions from ethanol-fed pigs than in controls. The percentage contribution of highly unsaturated fatty acids to total fatty acids in liver homogenates (after 12 mo of feeding) and microsome fractions (after 20 mo of feeding) was lower in the ethanol-fed pigs than in the controls, resulting in a lower peroxidizability index. Ethanol-fed pigs had minimal or no hepatic damage as assessed by histological methods. We suggest that the relative resistance of microsomes to lipid peroxidation is due to the lower peroxidizability index in the ethanol-fed pigs and may account in part for the absence of significant histopathological findings after 20 mo of ethanol feeding.

Animals↗
PubMed1990

The effect of chronic alcohol ingestion on free radical defense in the miniature pig.

Cellular protection from free radical reactions was measured in hepatic tissue from controls and miniature pigs fed ethanol. The activities of copper-zinc superoxide dismutase (CuZnSOD) and glutathione peroxidase were lower and the activity of manganese superoxide dismutase (MnSOD) was higher in the pigs fed ethanol than in controls. Glutathione concentration was lower in the pigs fed ethanol than in controls. Ethanol consumption did not result in increased lipid peroxidation as assessed by thiobarbituric acid-reactive substances. The ethanol-induced effects on the activities of the superoxide dismutases may be a reflection of available metals and/or a response to increased hepatic concentration of oxygen radicals. Because the protection afforded by the glutathione system was altered, pigs fed ethanol may be at risk of peroxidative damage with continued ethanol exposure.

Alcoholism↗
PubMed1989

The intestinal absorption of dietary folates in health and disease.

Dietary folates exist as pteroylpolyglutamates (PteGlun) that undergo hydrolysis to pteroylmonoglutamate (PteGlu) forms during the process of intestinal absorption. Using the technique of jejunal perfusion of separately labeled folates, our laboratory has demonstrated that hydrolysis of PteGlun occurs on the surface of the jejunum and is a prerequisite for folate absorption. An intestinal brush border pteroylpolyglutamate hydrolase (BB-PPH) has been identified in human and pig jejunum with characteristics that are distinct from those of an intracellular hydrolase (IC-PPH). Functional parallels of BB-PPH with in vivo hydrolysis of PteGlun in human and pig intestine and the clinical responsiveness of BB-PPH to different disease states indicate that this enzyme plays the major physiological role in folate absorption. Folate malabsorption is found in diseases which affect the jejunal mucosa and in response to various drugs. In most of these clinical conditions, folate malabsorption results from suppression of both of the processes of hydrolysis of PteGlun and jejunal uptake of PteGlu. Ongoing studies in miniature pigs are aimed at definition of the sequence of development of folate malabsorption in chronic alcoholism.

Animals↗
PubMed1989

Folate absorption in alcoholic pigs: in vivo intestinal perfusion studies.

To determine if impaired intestinal absorption contributes to the folate deficiency observed in chronic alcoholics, we assessed in vivo folate absorption in Hanford mini-pigs fed ethanol with an adequate diet. Sixteen minipigs were pair-fed diets supplemented with ethanol or sucrose to 60% of total calories for 11 mo. In the ethanol-fed pigs peak blood alcohol concentrations averaged 28 mmol/L, serum alanine transaminase and aspartate transaminase activities were elevated, and liver histology showed a centrilobular distribution of succinate dehydrogenase. Tissue folate concentrations were comparable in both groups. The jejunal uptake of folic acid, measured by intestinal perfusion, was similar in both groups of animals and was not affected by acute exposure to 445 mmol/L ethanol. The in vivo hydrolysis of polyglutamyl folate was reduced by 35% in one ethanol-fed minipig. Decreased hydrolysis of polyglutamyl folate may represent an early step in the development of folate deficiency in chronic alcoholics.

Alanine Transaminase↗