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Biomedical subjects

R A Wapnir

Publications and source records attributed to R A Wapnir.

At least 109 records · Page 6Linked to original sources
PubMed1978

The effects of small intestinal colonization by fecal and colonic bacteria on intestinal function in rats.

The effects of colonic and fecal bacterial proliferation on jejunal function were studied in normal rats and in low-germ rats after intraperitoneal injections of mecamylamine HCl. Jejunal bacteriology, bile salts, ultrastructure, and transport capacity were assessed. Normal rats given mecamylamine for 3 days had increased anaerobic bacteria in the intestinal fluid, and had high concentrations of deconjugated bile salts in the intraluminal contents. Jejunal bacteria were lodged between microvilli without penetrating the cell cytoplasm. However, there was focal cellular damage, including fused microvilli, dilated endoplasmic reticulum, and secondary lysosomes. In the mecamylamine treated normal rats intestinal glucose transport was reduced with an alteration compatible with noncompetitive inhibition. The absorption rates of galactose, fructose, 3-0-methyl-D-glucose, tyrosine, Na, and K were also decreased. In contrast, low-germ mecamylamine-treated rats showed no evidence of either increased anaerobic bacterial proliferation or deconjugation of bile salts, and had none of the fine structural alterations seen in regularly raised rats. Also, the transport of carbohydrates was unaltered. The findings suggest that non-invasive enteric proliferation of colonic and fecal bacterial anaerobes in rats may be associated with deconjugation of bile salts, ultrastructural alterations of the intestinal epithelial cells, and a diminished jejunal transport capacity of carbohydrates and other solutes.

Anaerobiosis↗
PubMed1978

Response of rat intestine to a hyperosmotic feeding.

After a single force-feeding of hypertonic (1300 mOsm) mannitol to rats there is rapid osmotic equilibration of the jejunal fluid, a sharp drop in luminal mannitol concentration and large influxes of water and sodium. During osmotic equilibration there was a significant loss of cells from the jejunal mucosa. In hypertonically fed rats there was an accumulation of protein, DNA, [3H]thymidine-labeled DNA, and disaccharidases in intestinal washings. Brush border disaccharidase specific activities on the jejunal mucosa were unaltered. Under the light microscope jejunal villi from hypertonic mannitol rats were comparable to controls. Some epithelial cells from rats force-fed hypertonic mannitol showed transient ultrastructural damage. Microvilli of some cells were shortened and fused at their bases 20 and 40 min after the force-feeding. By 120 min epithelial cell microvilli were all normal in appearance. In hypertonically fed rats the lateral interdigitating plasma membranes became disorganized. Large fragments budded off into one cell and fused to form larger stuctures. By 120 min many lysosomal autophagic vacuoles and residual bodies were seen. A single hypertonic force feeding produced jejunal cell loss associated with loss of brush border disaccharidases and focal ultrastructural damage.

Animals↗
PubMed1978

Experimental acute hypothermia and intestinal cellular integrity.

Shaven and unshaven rats were exposed to a cold stress at 4 degrees C for 6 hr (SE and UE). Control animals remained at room temperature (SC and UC). Hypothermia was induced in group SE, with mean rectal temperature of 22.0 +/- 2.0 degrees C (+/- S.E.M.). All other groups were normothermic, had similar arterial pO2 and hepatic tryptophan oxygenase levels. Acute hypothermia induced a sloughing of cells from the villi into the lumen of the gut, as indicated by an increased DNA in luminal washings. However, there was an unimpaired 3H-thymidine incorporation into the DNA of the intestinal mucosal cells and those present in lumina washes. Intestinal disaccharidases and alkaline phosphatase were not altered. This suggests that more severe cellular alterations reported earlier in hypothermia may have been caused by associated factors other than a decreased body temperature.

Alkaline Phosphatase↗
PubMed1977

Interaction between dietary carbohydrates and intestinal disaccharidases in experimental diarrhea.

The effects of carbohydrate intake on jejunal disaccharidases in rats with chronic mannitol-induced, osmotic diarrhea were studied. Weanling rats were force-fed 5 ml/100 g of body weight of water of 20% mannitol (w/v 1300 mOsm) daily for up to 14 days. Diets containing 70% of either starch, sucrose, glucose, or 20% lactose with 50% starch were fed ad libitum. Mannitol-fed rats had increased water intake and diarrhea. They gained weight, but less than controls. The levels of intestinal disaccharidases in mannitol-fed rats were related to dietary carbohydrate intake. Seven days of mannitol treatment led to lactase and sucrase deficiencies in rats fed starch whereas jejunal maltase and alkaline phosphatase were unchanged. Deficiencies in lactase and maltase but not in sucrase were induced when rats were fed a sucrose diet, while a decrease only in sucrase occurred in rats fed a lactose-starch diet. Rats with mannitol-induced diarrhea fed a glucose diet had reduced levels of all disaccharidases. The changes in intestinal disaccharidases were not associated with alterations in the number of epithelial cells or ultrastructural abnormalities. 3H-thymidine incorporation into DNA following 7 days of mannitol treatment was similar to water-fed controls. Absorptive epithelial cells were not damaged and the microvilli were normal in height and appearance. These data suggest that the levels of specific disaccharidases show and enhanced dependence upon the corresponding dietary substrates during diarrhea induced by an osmotic load.

Alkaline Phosphatase↗
PubMed1977

Fasting-induced hypoglycemia in experimentally malnourished rats.

The ability to withstand a fasting stress as related to glucose homeostasis was studied in malnourished rats. Young male Wistar rats were fed a low-protein (D), or a low-protein, low-energy diet (M) containing, respectively, 4% protein with 70% carbohydrate (D) and 4% protein and 45% carbohydrate (M). They were compared with rats fed a control diet with 18% protein and 70% carbohydrate (C). All diets contained 8% fat. After consuming the respective diets for 4 weeks, the rats were either killed or fasted for 24 or 48 hours. Hypoglycemia developed in the malnourished rats upon fasting, but not in those receiving a complete diet. Malnourished rats had a higher blood glycine level after 4 weeks of dietary treatment. There was a marked decrease of circulating alanine and glutamate-glutamine after 48 hours of fasting in all rats. There were no differences in lysine, histidine, glycine and serine-valine. Protein malnutrition produced an increase in brain lysine, gamma-aminobutyric acid, glycine and alanine, and of glycine and alanine in liver. In contrast, D and M rats showed a depletion in muscle lysine, alanine, serine-valine and glutamate-glutamine. The fasting stress produced no changes in brain or muscle glycogen. However, liver glycogen of rats fed the D and M diets was below that of rats fed the C diet for 4 weeks. In addition, after 48 hours of fasting the C rats mobilized more exhaustively their glycogen stores that the M rats. These data suggest that in chronic malnutrition, rats may maintain their glucose homeostasis by mobilization of muscular gluconeogenic amino acids through proteolysis or de novo synthesis. Rats which were fed protein and protein-energy-deficient diets lacked adequate liver glycogen stores and their overall gluconeogenic capacity was exceeded during fasting with resultant hypoglycemia.

Adaptation, Physiological↗
PubMed1977

Experimental lead poisoning and intestinal transport of glucose, amino acids, and sodium.

Juvenile rats fed a diet containing 1% lead acetate for 7 weeks, in addition to an impaired growth rate and renal function derangements, suffered malabsorption of glucose and certain amino acids, as assessed by an in vivo perfusion technique. The reduction in glucose absorption ranged between 10% and 31% when the carbohydrate was pumped in concentrations of 2-80 mM. This alteration was compatible with a noncompetitive type of transport inhibition. The intestinal absorption of glycine, lysine, and phenylalanine were, respectively, decreased 22, 18, and 15% when these amino acids were present at 1 mM levels. Sodium transport was severely reduced (57.6 +/- 17.9 (SEM) vs. 124.2 +/- 17.4 muEq/min-cm) and intestinal mucosa (Na+-K+)-ATPase was concomitantly lower in the lead-intoxicated rats (186.4 +/- 19.0 vs 268.4 +/- 29.8 nmol P/min-mg protein). However, this enzyme was not altered in liver and kidney. Furthermore, intestinal mucosa fructose-1,6-diphosphatase, succinic dehydrogenase, pyruvate kinase, and tryptophan hydroxylase were not different in experimental and control animals. These studies substantiate the presence of functional and biochemical abnormalities in the intestinal mucosa of young rats when fed substantial amounts of a soluble lead salt. It is, therefore, reasonable to accept the possibility that physiologic damage occurs in tissues directly subjected to high and persistent levels of a toxic agents, as it occurs in other organs, underscoring the parallelism between transport mechanisms at the renal and intestinal levels.

Adenosine Triphosphatases↗
PubMed1975

Inhibition of sodium intestinal transport and mucosal (Na+-K+)-ATPase in experimental Fanconi syndrome.

The administration of 1.5 or 9.0 mmoles/kg ip of maleate to rats induced, in addition to renal alterations similar to those occurring in the Fanconi syndrome, a decline in the intestinal mucosa (Na+-K+)-ATPase with a simultaneous decrease in sodium intestinal transport and an increase in potassium absorption. Further differences in the behavior of the two electrolytes were observed when the concentration of sodium in the perfusates was altered. No changes occurred in amino acid or glucose transport in experimental animals.

Adenosine Triphosphatases↗