Diabetes due to secretion of a structurally abnormal insulin (insulin Wakayama). Clinical and functional characteristics of [LeuA3] insulin.

We have identified a non-insulin-dependent diabetic patient with fasting hyperinsulinemia (90 microU/ml), an elevated insulin:C-peptide molar ratio (1.68; normal, 0.05-0.20), normal insulin counterregulatory hormone levels, and an adequate response to exogenously administered insulin. Insulin-binding antibodies were absent from serum, erythrocyte insulin receptor binding was normal, and greater than 90% of circulating immunoreactive insulin coeluted with 125I-labeled insulin on gel filtration. The patient's insulin diluted in parallel with a human standard in the insulin radioimmunoassay, confirming close molecular similarity. The patient's insulin was purified from serum and shown to possess both reduced binding and ability to stimulate glucose uptake and oxidation in vitro. Analysis of the patient's insulin by high-performance liquid chromatography (HPLC) revealed two products: 7.3% of insulin immunoreactivity coeluted with the human standard, while the remaining 92.7% eluted as a single peak with increased hydrophobicity. Family studies confirmed the presence of hyperinsulinemia in four of five relatives in three generations, with secretion of an abnormal insulin documented by HPLC in the three tested. Leukocyte DNA was harvested from the propositus and the insulin gene cloned. One allele was normal, but the other displayed a thymine for guanine substitution at nucleotide position 1298 from the putative cap site, resulting in a leucine for valine substitution at position 3 of the insulin A chain. Insulin Wakayama is therefore identified as [LeuA3] insulin.

Glucagon binding autoantibodies in a patient with hyperthyroidism treated with methimazole.

A 47-yr-old woman who had previously received methimazole (MMI) treatment for hyperthyroidism was found to have glucagon binding autoantibodies in plasma. She had never received glucagon. The binding substances were detected in plasma at the time of a glucagon RIA. [125I]Glucagon binding was inhibited only by porcine glucagon and porcine glicentin, and dissociated at acid pH. The substances proved to be glucagon binding antibodies (immunoglobulin G, L-chain K-type), as determined by ammonium sulfate and radioprecipitation. There were no clinical manifestations related the presence of these autoantibodies. In a survey of 91 patients with thyroid disease, 3 patients whose plasma bound [125I]glucagon were identified among 41 with hyperthyroidism who were receiving MMI treatment. Such binding was not found in plasma from untreated hyperthyroid patients, those receiving propylthiouracil or those with chronic thyroiditis. These findings suggest that the development of glucagon antibodies in hyperthyroidism may be associated with MMI treatment.

Phage induction by ultraviolet radiation in strains of Escherichia coli possessing and lacking dark repair capacity.

Prophage induction by ultraviolet light (UV) in strains of Escherichia coli possessing and lacking dark repair capacity was investigated. E. coli B and its UV-sensitive mutant B(s-1) were lysogenized by temperate phage phi80. Relative prophage induction by UV in the two strains paralleled relative UV killing, suggesting that prophage induction in a UV-resistant strain is susceptible to dark repair. Photoreactivation of induction was observed in B(s-1)(80), suggesting that the initial damage for UV induction of prophage in this very sensitive strain is due to pyrimidine dimers. No recovery of induction, however, was observed in B(80) when the UV-irradiated cells were held in phosphate buffer at 37 degrees although there was recovery of cell survival (liquid holding recovery). The frequency of spontaneous induction was very much greater in B(s-1)(80) than in other strains and is one of the highest yet observed in bacteria. Although increased sensitivity to UV killing in the logarithmic phase is usually seen in lysogenic strains, B(s-1)(80) was not more sensitive to UV killing than logarithmic phase B(s-1). Cell division after UV irradiation and before lysis, permitting viable cells among the progeny, could account for the lack of extra sensitivity in B(s-1)(80). This phenomenon actually was observed microscopically, although the mechanism is not understood.

Radioreceptor assay for beta-adrenergic receptor-reactive catecholamines in serum samples.

A procedure for effective application of ultrafiltration is described for preparation of serum catecholamine samples suitable for a sensitive radioreceptor assay. Each of the fresh serum samples unsuitable for the direct receptor assay was dialyzed by applying centrifugal force into a capsule-shaped porous core whose surface was tightly covered with a molecular filtration membrane. Interfering macromolecular serum components were left outside the capsule during the centrifugation or forced dialysis. The ultrafiltrate in the capsule was readily recovered by another centrifugation, and was found satisfactory as an assay specimen. In the radioreceptor assay system adapted to detect 30 pg per assay tube, epinephrine added to fresh serum to make the final concentration approximately 1 X 10(-8) mol/L was recovered semiquantitatively. Serum catecholamine level determined was equivalent to beta-adrenergic receptor reactivity that could be expressed in terms of (-)-epinephrine concentration.

Encephalomyocarditis virus induced diabetes mellitus in mice: long-term changes in the structure and function of islets of Langerhans.

Adult male mice infected with the M variant of encephalomyocarditis virus develop hyperglycaemia acutely as a consequence of B cell injury. The severity of the metabolic disease is variable and many animals become normoglycaemic during convalescence. The islets of Langerhans of these mice exhibit minor structural changes, but there are no significant abnormalities of insulin and glucagon secretion. In contrast, animals with persistent hyperglycaemia exhibit striking morphological alterations in the islets. The A cell mass is prominent, whereas B cells are reduced in number and exhibit striking cytological features. These changes are associated with both hypoinsulinaemia and hyperglucagonaemia.