Muscle glycogen synthesis after exercise: effect of time of carbohydrate ingestion

The time of ingestion of a carbohydrate supplement on muscle glycogen storage postexercise was examined. Twelve male cyclists exercised continuously for 70 min on a cycle ergometer at 68% VO2max, interrupted by six 2-min intervals at 88% VO2max, on two separate occasions. A 25% carbohydrate solution (2 g/kg body wt) was ingested immediately postexercise (P-EX) or 2 h postexercise (2P-EX). Muscle biopsies were taken from the vastus lateralis at 0, 2, and 4 h postexercise. Blood samples were obtained from an antecubital vein before and during exercise and at specific times after exercise. Muscle glycogen immediately postexercise was not significantly different for the P-EX and 2P-EX treatments. During the first 2 h postexercise, the rate of muscle glycogen storage was 7.7 mumol.g wet wt-1.h-1 for the P-EX treatment, but only 2.5 mumol.g wet wt-1.h-1 for the 2P-EX treatment. During the second 2 h of recovery, the rate of glycogen storage slowed to 4.3 mumol.g wet wt-1.h-1 during treatment P-EX but increased to 4.1 mumol.g wet wt-1.h-1 during treatment 2P-EX. This rate, however, was still 45% slower (P less than 0.05) than that for the P-EX treatment during the first 2 h of recovery. This slower rate of glycogen storage occurred despite significantly elevated plasma glucose and insulin levels. The results suggest that delaying the ingestion of a carbohydrate supplement post-exercise will result in a reduced rate of muscle glycogen storage.     

Steel factor stimulates the tyrosine phosphorylation of the proto-oncogene product, p95vav, in human hemopoietic cells.

Steel factor (SF) (also called stem cell factor, mast cell growth factor, or c-kit ligand) is a recently cloned hemopoietic growth factor that is produced by bone marrow stromal cells, fibroblasts, and hepatocytes. In both mouse and man it acts synergistically with several colony stimulating factors, including interleukin-3 (IL-3) and granulocyte macrophage-colony stimulating factor (GM-CSF), to induce the proliferation and differentiation of primitive hemopoietic precursor cells. In order to study its mechanism of action and to explore the molecular basis for its synergistic activity we have examined the proteins that become tyrosine phosphorylated in response to SF, IL-3, and GM-CSF. We report herein that SF, but not IL-3 or GM-CSF, dramatically stimulates the tyrosine phosphorylation of the product of the recently discovered proto-oncogene, vav, in two SF-responsive human cell lines, M07E and TF-1. Although phosphorylation is very rapid, reaching maximal levels within 2 min at 37 degrees C, co-immunoprecipitation studies suggest that c-kit may either not associate directly with p95vav or bind to it with very low affinity. Nonetheless, our data suggest that c-kit may utilize p95vav to mediate downstream signaling in hemopoietic cells.     

Production and purification of recombinant human interleukin-5 from yeast and baculovirus expression systems

A cDNA for human interleukin-5 (hIL-5) was created from the hIL-5 gene using site-directed mutagenesis to splice out the introns in vitro. This cDNA was expressed in yeast and baculovirus systems, utilizing in both cases an in-frame fusion to the pre sequence of the alpha-mating-type factor to direct secretion. The highest level of production was achieved from Sf9 cells using a baculovirus vector in serum-containing medium (2.7 mg/l), whereas in serum-free medium ten times less hIL-5 was produced. In the yeast system much lower levels of hIL-5 were produced (12.5 micrograms/l). Recombinant hIL-5 was purified to homogeneity from serum-free baculovirus cultures. The rhIL-5 consisted of a 30-kDa homodimer linked by disulfide bridging. The purified recombinant protein had a specific activity on murine BCL1 cells of 1.5 x 10(4) U/mg, of 3 x 10(5) U/mg in the murine eosinophil differentiation factor assay, and 2.4 x 10(7) U/mg in a human peripheral eosinophil maintenance assay.     

Functional differences in human neutrophils isolated pre- and post-prandially.

Activated polymorphonuclear leukocytes have been associated with neoplasia, atherogenesis and reperfusion injury. Since some of these conditions are also correlated with dietary fat, we examined the functional characteristics of leukocytes isolated from subjects before and after consumption of a lipid-rich meal. There was up to 2-fold greater superoxide generation in response to agonists in leukocytes obtained post-prandially; the maximum increase was observed about 4 h after eating and followed the peak (2-4 h) in serum triglycerides. Neutrophils isolated post-prandially also exhibited impaired chemotaxis and defective bacterial killing, but normal phagocytosis. These findings provide a new variable that should be considered in studies of leukocytes.     

Influence of age,sex, and dietary restriction on intracellular free calcium responses of CD4+ lymphocytes in rhesus monkeys (Macaca mulatta)

The influence of aging and dietary restriction on increase in intracellular free calcium ([Ca²⁺]_i) of CD4⁺ lymphocytes from Macaca mulatta was examined after stimulation with anti-CD3 mAb. We used a flow cytometric assay with the dye indo-1 and either direct or reciprocal immunofluorescent staining to dientify CD4⁺ cells. After stimulation with anti-CD3 mAb, intracellular free calcium responses were reduced in CD4⁺ lymphocytes from old male and female ad libitum fed monkeys compared to young and adult male or female monkeys. Old female monkeys had significantly lower [Ca²⁺]_i than did old male monkeys. The reduced responses were in part related to a decreased percentage of responding cells. Dietary restrition of males over a four-year period did not alter [Ca²⁺]_i response compared to ad libitum fed male monkeys. Female monkeys of all ages (which were restricted only for four months) also had similar [Ca²⁺]_i responses to ad libitum fed controls. Our data suggest that age-related changes in [Ca²⁺]_i responses are similar between humans and M. mulatta, and that over these intervals, no effects of caloric restrictions can be detected. © 1995 Wiley-Liss, Inc.     

8[prime]-Methylene Abscisic Acid (An Effective and Persistent Analog of Abscisic Acid)

We report here the synthesis and biological activity of a new persistent abscisic acid (ABA) analog, 8[prime]-methylene ABA. This ABA analog has one additional carbon atom attached through a double bond to the 8[prime]-carbon of the ABA molecule. (+)-8[prime]-Methylene ABA is more active than the natural hormone (+)-ABA in inhibiting germination of cress seed and excised wheat embryos, in reducing growth of suspension-cultured corn cells, and in reducing transpiration in wheat seedlings. The (+)-8[prime]-methylene analog is slightly weaker than (+)-ABA in increasing expression of ABA-inducible genes in transgenic tobacco, but is equally active in stimulating a transient elevation of the pH of the medium of corn cell cultures. In corn cells, both (+)-ABA and (+)-8[prime]-methylene ABA are oxidized at the 8[prime] position. ABA is oxidized to phaseic acid and (+)-8[prime]-methylene ABA is converted more slowly to two isomeric epoxides. The alteration in the ABA structure causes the analog to be metabolized more slowly than ABA, resulting in longer-lasting and more effective biological activity relative to ABA.     

In vitro auxin production by Balansia epichloë

Balansia epichloë, a systemic plant pathogen isolated from Sporobolus poiretii, was shown to produce the plant growth regulators 3-indole acetic acid, 3-indole ethanol, 3-indole acetamide and methyl-3-indole carboxylate when grown on a medium containing tryptophan. When grown on a tryptophan deficient medium 3-substituted indole derivatives were not detected. However, extracts of the medium in lower doses increased and in higher doses inhibited the growth of wheat coleoptiles.     

Organic mulches in highbush blueberries alter beetle (Coleoptera) community composition and improve functional group abundance and diversity

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