Summary. The effect of serotonin on insulin secretion and biosynthesis was studied using isolated islets of mice. Serotonin produced a small stimulatory effect on insulin secretion when glucose was present in the incubation medium at a low concentration. On the other hand, an inhibition of insulin secretion was obtained with serotonin when glucose in the medium reached 3.0 mg/ml concentration. No significant effect of serotonin was obtained on insulin biosynthesis, neither in the presence of low nor with a high glucose concentration. These results suggest that the effect of this monoamine on insulin secretion is not mediated via its effect on insulin biosynthesis.

The aim of this study was to evaluate the effect of a structured teaching/treatment programme on the clinical and metabolic control of non-insulin-dependent (type 2) diabetic patients. The programme was aimed at improving the overall treatment quality in these patients through measures involving self-care, diet, exercise and weight reduction. Four theoretical-practical teaching units were given once a week to group of 5-8 ambulatory patients by previously trained general practitioners. Clinical and biochemical parameters were recorded at the beginning of the course and 1 year after its completion in 40 patients attending the programme and in 39 patients of similar clinical characteristics under conventional diabetes treatment, but receiving no structured teaching before or during the survey period (control group). The drop-out percentage in the intervention group (25%) was significantly lower than in the control group (45%, P < 0.05), suggesting an incentive toward greater compliance in the former. At the end of the 1-year follow-up, the mean differences observed in the control and in the intervention groups were: body weight loss -2.4 +/- 0.5 kg vs -0.4 +/- 0.5 (P < 0.001); haemoglobin HbA1 -0.2% +/- 0.4% vs +0.8% +/- 0.4% (NS); number of daily oral hypoglycaemic agent intake -1.4 +/- 0.2 vs +0.9 +/- 0.2 tablets (P < 0.001). Our results strongly suggest that this programme, applied through family doctors, may constitute an efficient tool to improve the compliance and clinico-metabolic control of type 2 patients at the primary health care level.

This work was aimed at elucidating the effect of thyroid function on the physiology and biochemistry of the islet-cell population within the endocrine pancreas. To this end, we performed a comparative study of the physiochemical properties of islet-cell membranes and of the dynamics of glucose-induced insulin secretion in isolated pancreatic islets prepared from euthyroid i.e. control (C), hypothyroid (H), and thyroxin-supplemented hypothyroid (HT) rats. H rats were obtained by injecting normal rats with 131iodine, while HT rats consisted of H rats treated with thyroxin (T4). Insulin secretion was studied in isolated islets perifused with 3.3 and 16.6 mM glucose. Physicochemical properties of the partially purified islet plasma membranes were assessed by measurements of fluorescence polarization with the fluorophore 1,6-diphenyl-1,3,5-hexatriene (DPH) as a lipidic molecular probe. Insulin output during either the first or second phase of insulin secretion in H islets was significantly lower than in C islets. The slope of the curve in the second phase of insulin secretion was also lesser in H than in C islets, suggesting an additional defect in their velocity of hormone release. T4 administration of H rats reversed the decrease in insulin output to the range found in C islets but was incapable of correcting the defect in the hormone-secretion velocity. Several changes were found in the physicochemical properties of the membranes obtained from H islets as compared to C islets.(ABSTRACT TRUNCATED AT 250 WORDS)

Diabetes incidence and liver damage was studied and identified in C3H-s mice 21 days after Streptozotocin (SZ) administration (250 mg/kg/i.v.) at 04 hs (4 a.m.) and 16 hs (4 p.m.). Metabolic disturbances were assessed by daily control of glycosuria and serum glucose determined at the end of the experiment. Liver damage was controlled by light and electron microscopy. Both effects showed a circadian variation, with significant greatest values in the 16-h-injected group. Liver damage appeared whether the animals became diabetic or not, consisting in degranulation of the rough-surfaced endoplasmic reticulum, mitochondrial swelling with loss of cristae and edema of the ground substance, with flocculent amorphous precipitate. In some hepatocytes, a dilated cisternae of the endoplasmic reticulum was seen. It was concluded that: a) beta-cell and hepatocytes have a synchronic circadian sensitivity to SZ; b) liver damage was present whether the animals became diabetic or not, suggesting the presence of a different threshold for SZ effect in hepatocytes. These results might be taken into account when planning SZ use, either for experimental or clinical purposes.