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<p> Resistance exercise and amino acids independently and synergistically stimulate muscle protein synthesis. Unloading of skeletal muscle depresses fasted state muscle protein synthesis, but the effect on the fed state response is unknown. Elucidation of the signaling pathways underlying the regulation of these processes in humans is in its infancy. Therefore, the purpose of this thesis was to determine how resistance exercise, feeding, and unloading interact to affect muscle protein turnover and its markers. In study 1 young men (N=9) underwent an acute bout of unilateral leg resistance exercise with or without feeding, with biopsies 6 h post exercise. Exercise dephosphorylated eiF2Bε and together with feeding potentiated the increase in phosphorylation of p70s6k and rps6. In study 2, 12 young people received primed constant infusions of 13C6-Phe in the fasted state and at one of two i.v. AA infusion rates (low, 42.5 mg/kg/h AA; high: 261 mg/kg/h AA) after 14 d of knee-brace mediated immobilization. Immobilization decreased fasted and fed state myofibrillar protein synthesis at both doses without obviously affecting translational signaling proteins. In study 3, two markers of muscle protein breakdown and oxidative damage were measured in 21 subjects (men, N=13, women, N=8) after 2 d and 14 d of knee-brace mediated immobilization. Protein ubiquitination was elevated after 2 d of immobilization but there was no sustained elevation in ubiquination at 14 d or increases in the 14kDa actin fragment or protein carbonyls and 4-hydroxy-2-nonenal. These studies support the concept that the responses of human muscle to changes in loading are primarily at the level of protein synthesis, and the p70 pathway appears to play a role in mediating the hypertrophic response. The currently known static markers of translational signaling and protein breakdown, however, are not very informative when attempting to account for an underlying molecular mechanism for disuse atrophy. </p> / Thesis / Doctor of Philosophy (PhD)

<p> The presence of 0.10 moles/l. of glycine, glutamic acid, aspartic acid or leucine in a saturated bicarbonate solution will promote the formation of aragonitic calcium carbonate at 25.2°C. Magnesium ion, with or without an amino acid, also promotes the formation of aragonite. With increased amino acid concentration glutamic acid and alanine tend to promote the formation of more calcitic calcium carbonate, glycine and valine tend to promote the formation of more aragonitic calcium carbonate. Lysine and alanine show an increased tendency to form calcite at higher ionic strengths (.20) whereas glutamic acid shows the reverse. Some correlation with solubility and equilibrium constants for magnesium-amino acid complexes is indicated.</p> / Thesis / Candidate in Philosophy

<p> The experiments described in this thesis were performed to investigate the: 1. Role of nitrate in the growth of maize seedling and 2. Role of amino acids in the assimilation of nitrate by the growing embryo.</p> <p> Nitrate stimulated the germination of Zea mays L. seeds by 10 to 15 percent. Further growth of the embryo axis, up to 6 days, however, was not affected by nitrate. During the early growth of the seedling, endosperm nitrogen was able to support the requirements of the embryo for 6 to 8 days. After a lag of 2 days, the protein content of the embryo increased linearly up to 6 days at a rate of 597 μ g a day. Some increase was observed between 6 and 8 days also. After 8 days, the protein level of embryo plateaued. Addition of 10 mM nitrate caused an increase in the protein and total nitrogen of the embryo only after 6 days. The endosperm mutant of maize, opaque-2, also responded to the nitrate in the same way.</p> <p> The protein content of the primary leaves increased linearly between 5 and 7 days. After 7 days, there is no increase in the leaf protein. Nitrate increased the protein level of primary leaves by 25 percent after 7 days. It protected against the further loss of protein in mature leaf. These results suggest that the primary role of nitrate in the growth of maize seedlings is to prevent protein loss.</p> <p> Out of 8 amino acids tested individually, only lysine and to a lesser extent arginine, inhibited the induction of nitrate reductase in the maize root tips. Different ammonium salts had no effect on the induction of nitrate reductase. The initial rate of induction in opaque-2 mutant (high lysine) was lower than the wild type, W64A (low lysine). From a comparison of the rate of induction of nitrate reductase between young and mature leaf, it was suggested that the amino acid supply from the endosperm may inhibit the induction of nitrate reductase. In the young maize seedling, this effect of amino acids may be more effective in vivo and in this way the assimilation of exogenous nitrate could be restricted, when the endosperm amino acids are supporting the growth of the embryo.</p> / Thesis / Master of Science (MSc)

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