Jalil R. Kidwai

Hypoglycemie activity of Pterocarpus marsupium wood

Abstract Feeding of the ethyl acetate-soluble fraction of an absolute ethanol extract of Pterocarpus marsupium wood for 5 days significantly lowered blood sugar levels with a corresponding increase in the blood insulin level in alloxan-diabetic rats.

In vitro conversion of proinsulin to insulin by cathepsin B and role of C-peptide

SummaryCathepsin B, purified from isolated islets of Langerhans, when incubated with proinsulin underin vitro conditions could convert proinsulin to insulin and C-peptide, releasing free arginine and lysine. When C-peptide, prepared from rat pancreas, was added to the incubation system consisting of proinsulin and cathepsin B, it completely inhibited the conversion of proinsulin to insulin.

Alloxan-glucose interaction: Effect on incorporation of14C-leucine into pancreatic islets of rat

SummaryThe acute effect of alloxan on the incorporation of14C-leucine into isolated rat islets of Langerhans was studied. I.v. administration of alloxan (40 mg/kg body weight) in rats inhibited the subsequentin vitro incorporation of14C-leucine into (pro-)insulin in the isolated islets. Glucose (750 mg/kg body weight), when administered 5 min prior to alloxan, completely protected the islets against alloxan toxicity. The protective effect of glucose was partly reversed when the concentration of alloxan was raised to 80 mg/kg body weight. Similar results of inhibition of (pro-)insulin biosynthesis by alloxan and its protection by glucose were obtained when isolated rat islets were exposed to alloxan and/or glucosein vitro. Islets exposed to glucosein vitro immediately after alloxan exposure showed a slower rate of inhibition of (pro-)insulin biosynthesis, as compared to islets washed before exposure to D-glucose. In view of these findings, it is suggested that there is a common recognition site on B-cell for alloxan and glucose.

Precocious induction of hepatic aniline hydroxylase and aminopyrine N-demethylase with hydrocortisone in neonatal rat

Abstract The pre- and postnatal development of hepatic aniline hydroxylase and aminopyrine N -demethylase activities was studied in rats in order to identify the natural trophic factors, if any, responsible for early neonatal formation of the enzymes. The postnatal development of these two enzymes up to 3 weeks of age was comparable with that of cytoplasmic tyrosine aminotransferase. They could be precociously induced in 7-day-old rats by hydrocortisone. Cycloheximide inhibited their induction.

In vitro conversion of proinsulin to insulin by cathepsin B in isolated islets and its inhibition by cathepsin B antibodies

SummaryPurified bovine cathepsin B, when incubated with isolated rat islets of Langerhans, completely converts proinsulin to insulin as demonstrated by the incorporation of14C-leucine into islet proteins, releasing lysine as the only basic amino acid. Cathepsin B antibodies raised in rabbit inhibited the above conversion.

Synthetic analogs of cholecystokinin terminal tetrapeptide that stimulate insulin but not glucagon release from pancreatic islets

SummaryTwo synthetic analogs of CCK-4, Glp-Met-Asp-Phe-NH2 (I) and Pro-Met-Asp-Phe-NH2 (II) reported earlier to stimulate insulin release from the isolated rat pancreatic isletsin vitro at concentrations as low as 10−10 M, have now been found to be totally ineffective as glucagon releasers at concentrations as high as 10−6 M or higher. It is evident that the replacement of Trp in CCK- 4 by Glp and Pro residues leads to peptides which exhibit insulin releasing activity without stimulating the release of glucagon.

Stimulation of insulin secretion by peptides analogous to the C-terminal tetrapeptide amide of cholecystokinin

SummaryTwo tetrapeptides, Glp-Met-Asp-Phe-NH2 (I) and Pro-Met-Asp-Phe-NH2 (II), analogous to the C-terminal tetrapeptide amide of cholecystokinin (CCK-4) have been synthesized and their effect on the release of insulin from the isolated Langerhans islets of rat pancreas compared with that of synthetic CCK-4. Both the new congeners exhibited significant insulin-releasing activity at 10−8 M and 10−6 M concentrations, suggesting that the biological activity is retained when the N-terminal Trp residue of CCK-4 is replaced by Glp or Pro.

Insulin and glucagon releasing activity of coleonol (forskolin) and its effect on blood glucose level in normal and alloxan diabetic rats

SummaryColenol, a diterpenoid isolated from the roots ofColeus forskohlii stimulates the release of insulin and glucagon from the islets bothin vitro andin vivo. Coleonol-stimulated release of glucagon from isletsin vitro is much more pronounced as compared to that of insulin. Glucose concentration of 5.6 mM in the medium is required for the coleonol stimulation of insulin release. Feeding of coleonol to alloxan diabetic rats cause 36.5% increase in blood glucose level as compared to alloxan diabetic control. Oral feeding of coleonol for 7 days to normal rats causes increase in blood glucose, serum insulin, glucagon and free fatty acid levels with corresponding increase in glucose-6-phosphatase activity and depletion of liver glycogen. Predominant stimulation of A-cells by coleonol is suggested for the above effects.

Effect of some novel synthetic analogues of CCK-4 on insulin and glucagon secretion

SummaryThe biologic activities of three synthetic analogues of CCK-4 (Trp-Met-Asp-Phe-NH2) in which (i) the C-terminal residue Phe was N-methylated (peptide I); (ii) the C-terminal Phe residue was N-methylated and Ser is substituted for Met in position 2 (peptide II); (iii) Pro was substituted for Trp in position 1 and the C-terminal amino nitrogen was methylated (peptide III), have been described. Peptides I and II have been found to inhibit the release of both insulin and glucagon, while peptide III was found to be a potent releasing agent for insulin and an inhibitor for glucagon.

Isolation and characterisation of cathepsin-B from bovine pancreas

A simple procedure for the isolation of cathepsin-B from bovine pancreas employing ammonium sulphate fractionation, DEAE cellulose chromatography and Sephadex G-200 gel filtration is described. The purified enzyme gave a single band on polyacrylamide gel electrophoresis. The molecular weight as determined by gel filtration of the enzyme was 26,850. ItsKm andVmax values were 12.8 mM and 0.303 Μmol/min/mg, respectively. TheKi for iodoacetamide was 0.16 mM.