Biomedical subjects
Publications and source records attributed to T Toyota.
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The present study revealed that glucose-induced insulin secretion was significantly inhibited by perfusion with trypsin (10 mug/ml) in the isolated rat pancreas perfusion. However, when trypsin was interposed during perfusion of 16.6 mM glucose, glucose-induced insulin secretion was not suppressed during trypsin infusion. The insulin level was significantly lower in the trypsin treated animals than in the control after completion of trypsin infusion. The results suggest that trypsin does not attack the glucorecoptor bound with glucose but attacks the free glucoreceptor. Interestingly a biphasic pattern of glucose-induced insulin secretion disappeared by the pretreatment with trypsin. The possibility was suggested that tyrpsin prevented the initial binding of glucose to the B-cell.
Age and sex distribution of diabetics, seasonal incidence of diabetes, grade of hyperglycemia, frequency of vascular complications and daily living conditions were studied of 2771 diabetic patients experienced at five clinics. The cases consisted of 1587 male and 1184 female diabetics. The distribution of age of diabetes onset revealed that males predominate among diabetics but females predominate among child diabetics, and that the precentage of child was extremely low. This pattern was emphasized as characteristic of Japanese diabetic population. Distribution of fasting blood sugar at the diagnosis of diabetes was compared among the age groups of diabetes-onset and the results showed that percentage of the value exceeding 300 mg/100 ml was highest in the under 10 year-onset cases and decreased with age. The frequency of diabetic retinopathy and of ischemic ECG changes was analysed from the view point of age of diabetes onset and also the duration of the disease. The frequency of the retinopathy at the diabetes-onset was zero in the under 10 year-onset cases, 4.2% in the 10s-onset cases and increased with age. The longer the duration of the disease the higher the frequency of the retinopathy was. This increase along with the duration was most remarkable in the 10s- and 20s-onset cases and less remarkable in the 30s-onset cases. The retinopathy was significantly more frequent in female diabetics. Daily of the patients were studied by a questionnaire and the analysis of 1022 cases with diabetes of more than three years revealed that cases of patients working uneventfully and/or feeling fit were most frequent among the 30s- or 40s-onset cases and that cases of bed-disability were frequent among the cases whose diabetes was found in their twenties or younger. This study showed that the prognosis of the patients is quite different according to whether their diabetes occurred before of after 30 years of age.
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Activation of adrenergic beta receptors has been found to stimulate insulin release in vitro that may be mediated through the augmentation of cyclic AMP in the beta cell. The activation of adrenergic alpha receptors in the beta cell inhibits the insulin release. The present studies have shown that isoproterenol (0.62 mug/ml) and sodium dibutyryl cyclic AMP (50 mug/ml) stimulate the insulin secretion and inhibit the glucagon secretion in the presence of 50 mg/100 ml glucose by the isolated pancreatic perfusion of the rat, while norepinephrine (0.5 mug/ml) inhibits the insulin secretion induced by 150 mg/100 ml glucose and stimulates the glucaton secretion. Theophylline (50 mug/ml) does not stimulate the insulin and the glucagon secretion. When norepinephrine is added to theophylline, the output of glucagon does not occur. From these results it can be deduced that the pancreatic alpha cell function may be inhibited by elevation of intracellular cyclic AMP, in contrast to the beta cell function which is stimulated by an increment of cyclic AMP.
The effects of synthetic rat C-peptide 1 on insulin secretion from the isolated perfused rat pancreas was studied. The perfusion technique was according to the procedure described by Grodsky et al (1963) with a few modifications. After about 20 min of stabilization, the pancreas was perfused for 40 min with synthetic rat C-peptide 1 (100 ng/ml), during which (at 20 min) glucose concentration was switched from 2.7 to 16.6 mM. Insulin response to glucose (16.6 mM) was significantly decreased by the addition of the rat C-peptide 1 in advance when compared with those not pretreated with the C-peptide. In other experiments, the pancreas was exposed to glucose infusion (16.6 mM) for 60 min. 20 min after the start of glucose infusion, the C-peptide (100 ng/ml) was interposed for 20 min. The insulin secretion was reduced by the addition of the C-peptide. It is postulated that the C-peptide may have a role in the regulatory mechanism of the insulin secretion.
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