This experiment was undertaken to explore a novel method of therapy for insulin-dependent diabetes mellitus (IDDM), using nonobese diabetic (NOD) mice that had symptoms and histologic changes similar to those of human IDDM patients. We examined preventive and therapeutic effects of large-dose nicotinamide administration on diabetes in NOD mice. Eighteen young female NOD mice without glycosuria were randomly divided into two groups; nine received subcutaneous nicotinamide (0.5 mg/g body wt) injections every day and the other nine were maintained as a control group and not injected. After 40 days, all of the mice given nicotinamide showed almost normal glucose tolerance and only mild insulitis on histologic study. On the other hand, marked glycosuria and severe insulitis were observed in six of the nine mice not injected. Four of six NOD mice given nicotinamide from the day of the first occurrence of marked glycosuria displayed a disappearance of glycosuria and an improvement in glucose tolerance during the therapy; however, urine sugar became negative in only one of six mice that received nicotinamide from 1 to 2 wk after the onset of marked glycosuria. These results indicate that nicotinamide has preventive and therapeutic effects on diabetes in NOD mice, and suggest the reversibility of B-cell damage, at least at a very early stage of IDDM.

A sensitive, accurate method has been established for the assay of serum carnosinase by measuring the fluorescence emitted from the L-histidine liberated on treatment with o-phthaldialdehyde. Using this method the serum values for normal adults, infants and children were measured. The mean value was very low in infants of less than 1 year old but increased with age, being almost the same in children aged 6 years or more as in adults. In adult men, the mean activity was 1·85 μmol/mL/h and in adult women it was 2·07 μmol/mL/h. Low activity was observed in patients with muscular dystrophy.

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Effects of domperidone, a dopaminergic antagonist, on serum prolactin levels were studied in 6 normal men and 6 normal cyclic women at the different phases of their menstrual cycles (i.e., the follicular, the preovulatory and the luteal phases). Domperidone (10 mg, i.v.) caused significant increases in serum prolactin in all cases within 15 min after the injection. The prolactin response was significantly (p<0.01) higher in women than in men, and there was no significant difference in the prolactin responses among the three phases of the menstrual cycles. These results indicate that domperidone may be an effective stimulator of serum prolactin secretion in human beings.