[Analysis of islet B cell reserve in patients with NIDDM]

The plasma glucose and insulin response to oral glucose or carbohydrate meal tolerance tests were determined in 78 normal controls, 71 persons with IGT and 110 patients with NIDDM. The results showed that: (1) The fasting serum insulin levels and insulin/glucose ratio were all higher in persons with IGT than those in the normal controls, and they were normal in diabetics with fasting plasma glucose less than 7.8 mmol/L. In diabetics with fasting plasma glucose at 7.8-20.3 mmol/L, fasting insulin levels were within normal limit, but the values of insulin/glucose ratio were significantly decreased. (2) After glucose challenge, the values of serum insulin/glucose ratio were all increased in IGT, but were progressively decreased in diabetics as fasting plasma glucose gradually became higher. (3) Fasting serum insulin levels were increased in normal weight and over-weight individuals with IGT. But in those with diabetes, fasting insulin was increased in comparison with normal controls. When fasting plasma glucose was greater than 11.1 mmol/L, insulin/glucose ratio was decreased significantly. Our data suggests that the increased insulin secretion in persons with IGT was due to peripheral resistance and relative insulin insufficiency, and that hyperglycemia could compensate for B cell impairment.

Growth stimulation of 3T3 fibroblasts by cystatin

Treatment of cultures of mouse 3T3 fibroblasts with Cystatin C, a thiol-proteinase inhibitor isolated from chicken egg white, resulted in an enhanced rate of cell proliferation. This stimulation was demonstrated using two independent assay systems: (a) assessment of total cell number and (b) measurement of [3H]thymidine incorporated into acid-precipitable DNA. In both assays, the dose-response curves of Cystatin stimulation showed a rising function that plateaued at a concentration of approximately 120 micrograms/ml. The addition of Cystatin to cultures of Kirsten murine sarcoma virus-transformed 3T3 cells also enhanced DNA synthesis in these target cells. Control experiments showed that the presence of Cystatin did not alter the level of binding of radioactively labeled epidermal growth factor and platelet derived growth factor to 3T3 cells. These results argue against the possibility that the observed growth stimulation by Cystatin was due to growth factor contamination of the Cystatin preparation.

Serial isolates of Pseudomonas aeruginosa from a cystic fibrosis patient have identical pilin sequences

Five isolates of Pseudomonas aeruginosa (CD2, CD3, CD4, CD5, and CD10) from a patient with cystic fibrosis were examined with regard to several genotypic and phenotypic characteristics to determine whether the patient was colonized with one or several distinct strains. Isolates CD2, CD3, and CD4 were obtained from a single sputum sample, and CD5 and CD10 were obtained 1 and 2 years later, respectively. On the basis of colonial morphology, serotyping, and antibiograms, the five isolates appeared to be different strains. However, Southern blot analysis with a 1.2-kilobase DNA probe containing the P. aeruginosa PAK pilin gene indicated that all five strains were identical at that genetic locus. The pilin genes of the five isolates were cloned and sequenced at the nucleotide level and found to be identical. Southern blot analysis with a probe from a separate region of the P. aeruginosa chromosome, a 741-base-pair PstI-NruI DNA fragment adjacent to the exotoxin A gene, also revealed genetic identity among these five clinical isolates. On this basis, it was concluded that this patient was colonized with a single strain of P. aeruginosa and that the strain had remained genetically stable over a period of 2 years. The predicted pilin sequence of the CD isolates was almost identical to that of strain PA103 (97% homology) and serologically related to PAO pilin, with which it shared 80% homology. No immunological cross-reactivity was detected between the CD and PAK pilins, which shared the least homology (62%) among the four pilins considered in this study. Although all five CD isolates contained identical pilin genes, three had acquired mutations which prevented normal expression of the pilus system. CD3 was a putative regulatory mutant which was unable to produce normal amounts of pilin, and CD4 and CD10 were putative assembly mutants which produced normal amounts of pilin but were unable to assemble the pilin subunit into intact pili.

Antibodies against mammary derived growth inhibitor (MDGI) react with a fibroblast growth inhibitor and with heart fatty acid binding protein

A polypeptide growth inhibitor, designated as mammary derived growth inhibitor, has previously been purified from lactating bovine mammary glands. Polyclonal rabbit antiserum raised against mammary derived growth inhibitor cross-reacts with bovine heart fatty acid binding protein and bovine peripheral myelin P2 protein. These results are consistent with the observation that the amino acid sequence of mammary derived growth inhibitor showed homology to the sequences of these proteins. In a parallel series of immunoblotting experiments, rabbit anti-mammary derived growth inhibitor also reacted specifically with a fibroblast growth inhibitor purified from the conditioned medium of cultured mouse 3T3 fibroblasts. These data suggest that bovine mammary derived growth inhibitor and mouse fibroblast growth inhibitor may share common structural features and raise the possibility that these growth inhibitors may together define a new family of growth regulatory molecules.