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Biomedical subjects

H Kather

Publications and source records attributed to H Kather.

At least 145 records · Page 8Linked to original sources
PubMed1978

[Adipose tissue and obesity. Part 1: fat cell size and fat cell number].

The role of the number and size of adipocytes in the pathogenesis of obesity is reviewed. The observation that hyperplasia of adipose tissue is associated with child-onset obesity was over-interpreted. Nevertheless most recent studies suggest that fact cell size and number are regulated and can influence food intake. The discovery of preadipocytes has opened a new field or research offering the possibility of new concepts in the prevention and therapy of obesity.

Adipose Tissue↗
PubMed1978

Adenylate cyclase of human gastric mucosa. Stimulation by prostaglandins.

It has been shown that human gastric mucosa contains a prostaglandin-sensitive adenylate cyclase system. Of the prostaglandins tested the E-type induced an about 3--3.5-fold increase of enzyme activity. The prostaglandin A2 by causing an about 2.5-fold enhancement of cAMP formation and the F-prostaglandins (1.4--2.0-fold stimulation) were less effective in activating the enzyme system. Maximally effective concentrations of histamine and prostaglandin E2 were additive with respect to enzyme activity indicating that both hormones act via individual adenylate cyclases.

Adenylyl Cyclases↗
PubMed1978

[New aspects of catecholamin-receptor interactions. Pathophysiological and clinical implications (author's transl)].

The molecular aspects of catecholamine-receptor interactions are reviewed with respect to their clinical implications. Beta- and in some tissues alpha-adrenergic receptors are coupled to the membrane-bound adenylate cyclase. The adrenergic receptor sites are distinct membrane constituents. Their number and the ratio alpha-to beta-receptor site depend on the plasma concentration of catecholamines and are affected by diet and endocrinological factors. Recent clinical studies suggest that long-term treatment with beta-adrenergic agonists may induces desensitization of target tissues due to changes in the adrenergic receptor moieties.

Adenylyl Cyclases↗
PubMed1978

Epinephrine-sensitive adenylate cyclase of human fat cell ghosts. Modulation of enzyme activity by GTP.

Some of the effects of GTP on human fat cell adenylate cyclase activity were studied. This nucleotide caused a dose-dependent inhibition of basal activity without affecting the hormone-activated rate of cAMP formation. Maximal effects were observed at GTP-concentrations of about 1 x 10(-4) M. The relative extent of hormonal stimulation was about 1.5-fold increased in the presence of 0.1 mM GTP.

Adenylyl Cyclase Inhibitors↗
PubMed1978

Human colonic adenylate cyclase: effects of bile acids.

Three different bile acids--deoxycholic acid, chenodeoxycholic acid and ursodeoxycholic acid--were tested for their capacity to stimulate the adenylate cyclase in human colonic mucosa. This enzyme system was found to be sensitive towards vasoactive intestinal polypeptide and prostaglandin E2. These three bile acids were ineffective in activating the human cyclase system over a wide concentration range tested. Concentrations above 1 X 10(-5) mmol/l induced a dose-dependent inhibition of basal enzyme activity. These results suggest that bile-acid induced diarrhoea is not associated with activation of the membrane-bound adenylate cyclase system at least in man.

Adenylyl Cyclases↗
PubMed1978

Hormone-sensitive adenylate cyclase in human colonic mucosa.

Human colonic adenylate cyclase has been shown to be sensitive to vasoactive intestinal polypeptide (VIP) and prostaglandins of the E- and F-type. Maximal activation of enzyme activity averaged 200% for VIP and 300-350% for the E-prostaglandins. Both classes of hormones had an additive effect on enzyme activity indicating the existence of two distinct hormone-sensitive adenylate cyclases in human colonic mucosa.

Adenylyl Cyclases↗
PubMed1978

Distribution of prostaglandin-sensitive adenylate cyclase in human upper gastrointestinal tract.

The localization of the prostaglandin-sensitive adenylate cyclase in the upper gastrointestinal tract in human beings was studied. The prostaglandin-sensitive enzyme was almost evenly distributed throughout the fundic, antral and duodenal mucosa. The enhancement of enzyme activity in the presence of maximally effective prostaglandin concentrations exceeded basal levels by about 200%. The physiological role of the prostaglandin sensitive adenylate cyclase in gastric and duodenal function, however, remains to be established.

Adenylyl Cyclases↗
PubMed1978

Effects of prostaglandins and their methylated analogues upon human adenylate cyclase in the upper gastrointestinal tract.

The effects of prostaglandin E2, prostaglandin A2 and their methylated analogues upon the adenylate cyclase in human gastric mucosa were studied. PG E2 and 16,16-dimethyl-PG E2 stimulated the enzyme activity to a greater degree than PG A2 and 16,16-dimethyl-PG A2. 16,16-dimethyl-PG E2 was less potent in activating the enzyme system than its parent compound. The results suggest that the more pronounced antisecretory activity of 16,16-dimethyl-PG E2 is due to its greater resistance against enzymatic degradation.

Adenylyl Cyclases↗
PubMed1978

Inhibition of human colonic adenylate cyclase by RMI 12330 A.

RMI 12330 A, a compound of the lactamamide series, is a potent inhibitor of vasoactive intestinal polypeptide(VIP)- and prostaglandin (PG)-stimulated colonic secretion in the rat. This substance was tested on the adenylate cyclase system in human colonic mucosa. RMI 12330 A inhibited PGE2-, 16,16-dimethyl-PGE2- as well as VIP-sensitive adenylate cyclases in a dose-related manner. Half-maximal inhibition of hormone-stimulated enzyme activities occurred at a lactamimide concentration of about 0.15 mM. Lactamimide inhibition was non-competitive. Our results are compatible with the concept of RMI 12330 A acting as an inhibitor of colonic secretion via inhibition of hormone-sensitive adenylate cyclase. Since basal, NaF- and guanylyl-imidodiphosphate-stimulated enzyme activities were also affected by this compound, we may conclude that RMI 12330 A is a non-specific inhibitor of the human colonic adenylate cyclase system.

Adenylyl Cyclases↗
PubMed1978

Activation of human adenylate cyclase in the upper gastrointestinal tract by vasoactive intestinal polypeptide.

The effects of various polypeptide hormones known to inhibit gastric acid secretion were tested on the adenylate cyclase system in human gastric and duodenal mucosal homogenates. Glucagon and secretin failed to stimulate the enzyme system in the stomach. The latter hormone produced a small but significant activation of the duodenal cyclase. The vasoactive intestinal polypeptide (VIP), however, induced a dose-dependent increase of enzyme activity throughout the stomach and the duodenum. Maximal effects (1.8 to 3.0-fold increase) were observed at a VIP-concentration of about 10 microgram per ml. Because the entire physiological role of VIP in gastric function has not been defined, ipt cannot be discerned whether the VIP-stimulated adenylate cyclase is linked to inhibition of gastric acid secretion or to another as yet unrecognized effect of this hormone in human gastric function.

Adenylyl Cyclases↗
PubMed1978

Prostacyclin: a potent activator of human colonic adenylate cyclase activity.

Prostacyclin and its stable catabolite 6-keto-prostaglandin F1 alpha were tested on the human colonic mucosal adenylate cyclase which represents the key enzyme in the secretory process in this organ. Prostacyclin was able to activate dose-dependently the human cyclase system. Saturating concentrations of prostacyclin and 6-keto-prostaglandin F1 alpha (each 0.28 mM) increased the enzyme activity 2.5-fold and only 1.4-fold, respectively. The presence of prostacyclin receptor sites in human colonic mucosa suggests a physiological role of this novel prostaglandin in human colonic function.

Adenylyl Cyclases↗