Meal-frequency effects on plasma hormone concentrations and cholesterol synthesis in humans.

To examine meal-frequency effects on circulating hormone concentrations and cholesterol synthesis, male subjects consumed liquid diets given as either six evenly spaced (ES) or three diurnal (DI) meals over 3 d. Deuterium oxide was given on day 2 and blood sampled every 4 h over days 2 and 3 to measure plasma cholesterol, glucose, insulin, and glucose-dependent insulinotropic polypeptide (GIP) concentrations and cholesterol synthesis. Cholesterol synthesis was determined from deuterium incorporation into plasma free cholesterol by using constrained and unconstrained curve-fit models. Plasma total cholesterol concentrations decreased in both ES and DI groups (P < 0.05). The ES group had lower insulin (P < 0.05) and GIP (P < 0.001) concentrations compared with the DI group. Cholesterol synthesis was reduced (P < 0.01) in the ES vs the DI group when determined by using constrained (0.050 +/- 0.002 vs 0.075 +/- 0.005 pools/d, respectively) and unconstrained (0.072 +/- 0.005 vs 0.119 +/- 0.011 pools/d, respectively) models. These data suggest meal frequency-dependent control of cholesterogenesis via hormonally mediated mechanisms.

Identification of a Rous sarcoma virus transformation-related protein in normal avian and mammalian cells.

Avian sarcoma viruses (ASV) contain a gene (src) whose protein product mediates sarcomagenic transformation. This product is a 60,000-Mr phosphoprotein designated pp60src. We have found that normal uninfected frog, chicken, rat, and human cells contain a 60,000-Mr phosphoprotein related to the product of the ASV src gene and have designated that protein pp60. A phosphoprotein of similar size was not detectable in Drosophila cells. The pp60 proteins were detected by immunoprecipitation with rabbit antitumor serum containing broad spectrum antibodies to pp60src. Peptide maps of [35S]methionine-labeled pp60 and pp60src indicated major similarities as well as some differences in amino acid composition. Peptide maps of the 32P-labeled proteins demonstrated that the phosphopeptides of all endogenous pp60 molecules tested were identical. However, some differences were noted between the phosphopeptide patterns of pp60 and viral pp60src. The kinase activity associated with pp60src was measured in the immunocomplex and resulted in the transfer of radioactive phosphorus from [gamma-32P]ATP to the immunoglobulin heavy chain as well as to an 80,000-Mr phosphoprotein. The pp60 of chicken, rat, and human origin also contained an associated kinase activity. These results are consistent with the notion that the pp60 molecules are the protein products of endogenous sarc sequences found in vertebrate cells.