Search PubMed⌕ Search

Biomedical subjects

R M Batt

Publications and source records attributed to R M Batt.

At least 127 records · Page 7Linked to original sources
PubMed1981

Differential effect of glucocorticoids on structure and function of adult rat jejunum.

The long-term (28 days) effects of feeding two glucocorticoids, prednisolone and betamethasone 17-valerate, on the adult rat jejunum were examined. Both steroids increased the activities of microvillus enzymes, alpha-glucosidase, aminopeptidase, and gamma-glutamyltransferase, measured in isolated epithelial cells by 46-83%. However, betamethasone 17-valerate caused striking epithelial hypoplasia such that microvillus enzyme activity per centimeter of intestine was similar to that of control rats. Prednisolone produced a trivial epithelial hypoplasia, and therefore microvillus enzyme activity per centimeter of intestine was increased. D-Galactose absorption measured in vivo was similarly affected by the two steroids. D-Galactose absorption per centimeter of intestine was increased after prednisolone but unchanged after betamethasone 17-valerate. Thus, glucocorticoids have separate and opposing actions on the function and structure of the adult rat small intestine: a) to increase the digestive-absorptive function of the mature epithelial cell and b) to decrease the epithelial cell population. These findings suggest that the effect of any particular glucocorticoid on intestinal function will depend on the extent to which these opposing actions predominate.

Aminopeptidases↗
PubMed1979

Enhancement of ileal adaptation by prednisolone after proximal small bowel resection in the rat.

The effect of prednisolone on the adapted ileum of the rat after jejunal resection was examined. Three weeks after 50% proximal small bowel resection animals were fed pharmacological doses of soluble prednisolone (0.75 mg/kg/day) over a one week period, and killed at four weeks. Animals treated with prednisolone showed significant increases in brush border alpha-glucosidase, leucyl-2-napththylamidase and gamma-glutamyl transferase (P less than 0.01) per unit length of intestine compared with resection alone and transection reanastomosis control groups. This increase was the result of a significant enhancement (P less than 0.01) of brush border digestive enzyme activity per milligram of epithelial cell DNA-that is, per enterocyte-and was associated with a similar increase in enterocyte RNA content. In contrast, the activities of lysosomal and mitochondrial marker enzymes per milligran of DNA were similar in each group. Cell proliferation was not further stimulated by prednisolone. Thus prednisolone can selectively enhance brush border digestive capacity after intestinal resection without increasing cell proliferation. The increase in enterocyte RNA suggests that enzyme induction may be the mechanism of this effect.

Adaptation, Physiological↗
PubMed1979

Biochemical changes in the jejunal mucosa of dogs with naturally occurring exocrine pancreatic insufficiency.

The roles of extracellular and intracellular mechanisms in the degradation of brush border proteins have been investigated by studying the small intestinal mucosa of dogs with naturally occurring exocrine pancreatic insufficiency. Peroral jejunal biopsies were homogenised and the organelles separated by isopycnic centrifugation on continuous sucrose density gradients. The distributions of marker enzymes for the principal subcellular organelles were determined in the gradients and related to the specific activities in the homogenates. There were increased activities of the brush border carbohydrases zinc-resistant alpha-glucosidase, maltase and sucrase in the pancreatic insufficient animals, but no change in lactase activity. The activity of gamma-glutamyl transferase was also higher in the affected group; the activities of two other brush border enzymes, alkaline phosphatase and leucyl-beta-naphthylamidase, however, were unaltered. These findings with an increase in the modal density of the brush border from 1.20 to 1.22 are consistent with an enhanced glycoprotein content of the microvillus membrane. There were also rises in the activities of lysosomal enzymes. N-Acetyl-beta-glucosaminidase activity was increased in the soluble fractions and the percentage latent enzyme activity was reduced, findings indicative of an increased fragility of the lysosomal membrane. There were no marked alterations in the activities or density gradient distributions of marker enzymes for the other organelles, stressing the specificity of the changes in the brush borders and lysosomes. These findings are compatible with the degradation of certain exposed brush border proteins by pancreatic proteases and suggest that when this is defective, intracellular degradative mechanisms may be stimulated.

Acetylglucosaminidase↗
PubMed1978

Analytical subcellular fractionation studies on enterocytes from the jejunum and ileum of the rat and some properties of brush-border alkaline phosphatase.

1. Enterocytes, isolated from the proximal jejinum and distal ileum of the rat, were homogenized and their organelles separated by isopycnic centrifugation on continuous sucrose density gradients. The distributions of marker enzymes for the principal organelles, RNA and protein were determined in the sucrose gradients and related to the activities per entercocyte. 2. In the jejunum the modal equilibrium densities of the various organelles were: brush borders (1.20), lysosomes (1.20), peroxisomes (1.19), mitochondria (1.17) and basal-lateral membranes (1.13). The values were not significantly different in the ileum. The activities of brush-border enzymes, soluble and mitochondrial malate dehydrogenase, soluble and membrane-associated lactate dehydrogenase and particulate protein content, however, were greater in the jejunal than the ileal enterocytes. 3. Detergent exposed latent alkaline phosphatase activity in jejunal enterocytes and indicated that this enzyme is present not only in the brush border but also in the basal-lateral membrane and soluble fractions of the cell. 4. Isolated jejunal brush-border preprations showed latent activities of both alkaline phosphatase and gamma-glutamyltransferase whereas the activities of alpha-glucosidase and leucyl-beta-naphylamidase were not affected by detergent. Mechanical disruption of these preparations suggested the presence of two forms of alkaline phosphatase in the brush border and provides a technique to assess membrane fragility.

Alkaline Phosphatase↗
PubMed1978

The effects of prednisolone on the rat enterocyte at a subcellular level.

1. Enterocytes, isolated from the proximal jejunum and distal ileum of normal and prednisolone-treated rats, were homogenized and fractionated by isopycnic centrifugation on sucrose density gradients. The distributions of marker enzymes for the principal subcellular organelles, RNA and protein were determined and related to the activities per enterocyte. 2. In enterocytes fromthe jejunum and ileum of prednisolone-treated animals the activities of particulate brush-border enzymes and of both soluble and mitochondrial malate dehydrogenase were increased compared with those of the control system. The equilibrium density of the brush borders was enhanced in the prednisolone-treated jejunum. The modal densities of the other organelles were unaltered by prednisolone administration. 3. There was a large increase in the total RNA content of enterocytes from the jejunum and ileum of prednisolone-treated animals. This was predominantly associated with a distinct particulate component, indicative of a proliferation of the rough endoplasmic reticulum and consistent with an enhanced rate of protein synthesis. 4. Studies of latent brush-border enzyme activities, the mechanical fragility of isolated brush borders and electron microscopy suggest that steroid administration results in no marked alterations in the gross conformation of the brush-border membrane or in the orientation of the enzymes within the membrane.

Alkaline Phosphatase↗
PubMed1978

Subcellular fractionation studies on peroral jejunal biopsies from the dog.

Portions of closed jejunal biopsies from the dog were homogenised and their organelles separated by isopycnic centrifugation on continuous sucrose density gradients. The distributions of marker enzymes for the principal organelles were determined using highly sensitive assay procedures. The following organelles, with assayed marker enzymes and modal densities between brackets were characterised: peroxisomes (catalase, 1.21); brush borders (zinc-resistant alpha-glucosidase, leucyl-beta-naphthyl-amidase, gamma-glutamyl transferase, alkaline phosphatase, 1.20); lysosomes (N-acetyl-beta-glucosaminidase, alpha-mannosidase, 1.19); mitochondria (malate dehydrogenase, 1.18); endoplasmic reticulum (Tris-resistant alpha-glucosidase, 1.16); basal-lateral membranes (5'-nucleotidase, 1.11) and cytosol (lactate dehydrogenase). Homogenisation in isotonic sucrose containing digitonin (0.12 mmol/litre) selectively disrupted lysosomes and increased the equilibrium density of brush border and basal-lateral membranes. This procedure will be used to study the subcellular pathology of naturally occurring intestinal disease in the dog.

Acetylglucosaminidase↗
PubMed1976

Absorption of galactose by the rat small intestine in vivo: proximal-distal kinetic gradients and a new method to express absorption per enterocyte.

1. The absorption in vivo of D-galactose by the rat small intestine has been examined in proximal jejunum and distal ileum by use of a recirculation-perfusion technique. 2. Multiple sequential perfusions over 4 h produced no subsequent functional or morphological damage in the perfused segments. 3. Absorption of galactose from 8 and 64 mmol/l solutions was found to be independent of flow rate over the range 1-0-6-5 ml/min. 4. Galactose absorption in both the jejunum and the ileum exhibited saturation kinetics of the Michaelis-Menten type, and phlorrhizin sensitivity. Sorbose was only absorbed minimally. These observations demonstrate that galactose is absorbed by carrier-mediated transport and that there is no significant passive diffusive component in vivo. 5. Under the stated experimental conditions, the maximum absorptive capacity was 4-5 times greater in the jejunum than in the ileum. The Michaelis constant for galactose was higher in the jejunum than in the ileum. 6. Enterocytes were isolated from perfused segments and quantified by DNA assay with a correction for yield. In this manner, the absorptive capacity per enterocyte was calculated. 7. The maximum absorptive capacity per enterocyte was 3-5 times greater in the jejunum than in the ileum.

Animals↗
PubMed1976

Effects of prednisolone on the small intestinal mucosa of the rat.

1. The effects in rats of an oral pharmacological dose of prednisolone on mucosal function, enzymology, lysosomal membrane fragility, morphology and cell kinetics have been examined in proximal jejunum and distal ileum. 2. The maximum absorptive capacity for galactose was significantly greater in both the jejunum and the ileum of the steroid-treated animals. This was due to an increase in carrier-mediated transport in the individual enterocytes and not to a change in the cell population. The Michaelis constant for galactose was not significantly altered by prednisolone. 3. Activities of brush-border and mitochondrial enzymes and of RNA were increased in isolated enterocyte preparations from the jejunum and ileum of the steroid-treated group. 4. Lysosomal membrane fragility was unaltered in the prednisolone-treated group. 5. Morphometrical observations confirmed that the size of the enterocyte population was unaltered by prednisolone. Studies on cell kinetics indicate that the effects of prednisolone are due to a direct action on the enterocyte and not secondary to changes in migration rate.

Animals↗