Effects of insulin-like growth factor-I on glucose tolerance, insulin levels, and insulin secretion.

Insulin-like growth factor-I (IGF-I) and insulin interact with related receptors to lower plasma glucose and to exert mitogenic effects. Recombinant human IGF-I (rhIGF-I) was recently shown to decrease serum levels of insulin and C-peptide in fasted normal subjects without affecting plasma glucose levels. In this study we have investigated in six healthy volunteers the responses of glucose, insulin, and C-peptide levels to intravenous rhIGF-I infusions (7 and 14 micrograms/kg.h) during standard oral glucose tolerance tests (oGTT) and meal tolerance tests (MTT), respectively. Glucose tolerance remained unchanged during the rhIGF-I infusions in the face of lowered insulin and C-peptide levels. The decreased insulin/glucose-ratio presumably is caused by an enhanced tissue sensitivity to insulin. The lowered area under the insulin curve during oGTT and MTT as a result of the administration of rhIGF-I were related to the fasting insulin levels during saline infusion (oGTT: r = 0.825, P less than 0.05; MTT: r = 0.895, P less than 0.02). RhIGF-I, however, did not alter the ratio between C-peptide and insulin, suggesting that the metabolic clearance of endogenous insulin remained unchanged. In conclusion, rhIGF-I increased glucose disposal and directly suppressed insulin secretion. RhIGF-I probably increased insulin sensitivity as a result of decreased insulin levels and suppressed growth hormone secretion. RhIGF-I, therefore, may be therapeutically useful in insulin resistance of type 2 diabetes, obesity, and hyperlipidemia.

[Studies in biotechnology at the Federal Technical College, Zurich]. / Das Studium in Technischer Biologie an der Eidgenössischen Technischen Hochschule Zürich.

A new Curriculum, termed Technical Biology (or Biotechnology) has been instituted at the Swiss Federal Institute of Technology in Zurich, Switzerland. Biotechnology is regarded not as a Natural Science, but as an Engineering Science. On a solid basis of two years of mathematics, physics, chemistry, physical chemistry, and biology, courses are offered in technical microbiology and process and control engineering.

Xanthine dehydrogenase and aldehyde oxidase in chicken liver: Molecular identity?

Evidence is presented to suggest that in chick liver, xanthine dehydrogenase and aldehyde oxidase activities are associated with only one protein species. The results of SDS electrophoresis of the purified material indicate a subunit MW of 120 000.

Origin of leg musculature during Drosophila metamorphosis.

Pro- and mesothoracic leg imaginal disks of late third-instar larvae of genotypes affecting the electrophoretic mobilities of alpha-glycerolphosphate dehydrogenase (EC 1.1.1.8) and arginine kinase (EC 2.7.3.3) were transplanted into host larvae of different genotypes. The metamorphosed implants were analyzed microscopically for the presence of musculature, histochemically for the distribution of enzyme activity, and electrophoretically for determination of the phenotypes of the two muscle-marker enzymes. The results permit the conclusion that leg imaginal disks contain muscle stem-cells.

Assay systems for the study of gene function. 2 assay systems, the syntheses of RNA and protein, are described; their virtues and drawbacks are discussed.

The study of genetic regulatory mechanisms operating in plants and animals is of paramount importance in contemporary biology. A precise understanding of the mechanisms that underlie normal cellular differentiation is a prerequisite for understanding neoplastic transformation and genetic disease. At present, we are not aware of a single assay system that can give answers to all questions we are already able to pose. Studies of RNA synthesis are valuable because they provide a direct measurement of transcriptional activity. But these studies remain incomplete until we succeed in unraveling the metabolic roles of the molecules whose synthesis we study. In this respect, the study of enzyme synthesis represents a better defined assay system, although the interpretation of observed fluctuations in synthetic rates is made difficult by the many steps that intervene between the genes and their finished protein products. We propose that a combination of protein biosynthetic and cytogenetic analysis is a promising assay system for further investigation.