Biomedical subjects
Publications and source records attributed to M C Powanda.
Tularaemia in rats causes a doubling of the serum phenylalanine/tyrosine ratio and a more than twofold increase in muscle phenylalanine which cannot be accounted for by decreased hepatic phenylalanine hydroxylase (EC 1.14.16.1) activity, but appear to result from a generalized movement of amino acids from muscle to liver during infection.
At 26 h after inoculation of rats with Diplococcus pneumoniae, the serum concentrations of 10 and 20 individual amino acids were lower than corresponding values observed in pair-fed controls. In contrast, only 2 of 20 serum amino acids were similarly decreased in rats inoculated with Salmonella typhimurium. Despite these serum differences, a greater accumulation of labeled non-metabolizable amino acids occurred in the livers of rats infected with S. typhimurium. These data suggested a greater increase in the flux of amino acids from muscle to liver in the rats infected with S. typhimurium as compared to those infected with D. pneumoniae. A similar increase in serum protein synthesis was observed in rats infected with D. pneumoniae or S. typhimurium. However, with the latter infection, a larger percentage of the amino acids appeared to be utilized as a source of energy in addition to their role as precursors of proteins.
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Markedly increased synthesis of alpha(2) and beta globulins and alpha(1), alpha(2), and beta glycoglobulins occurs during pneumococcal sepsis in the rat simultaneously with decreased albumin formation, diminished tritiated leucine incorporation into muscle protein, and enhanced excretion of nitrogen. This augmented synthesis of specific serum proteins does not become evident until fever and bacteremia develop, and it appears to be a fundamental aspect of host response to a proliferating bacterial infection in that it occurs even in rats fed a protein-deficient (6% protein) diet after weaning and before exposure to Diplococcus pneumoniae. Although amino acid catabolism, in general, appears to be increased during infection, tryptophan degradation via the kynurenine pathway, as assessed by measuring diazotizable urinary metabolites, changes little or is, at times, significantly less than in control animals. Coincidentally, functional tryptophan oxygenase activity decreases at 16 hr after exposure. Total tryptophan oxygenase activity, however, is unchanged.
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The concentration of 21 individual free amino acids in serum, liver, and skeletal muscle was determined in rats during the incubation, acute illness, and terminal stages of experimental infection with Diplococcus pneumoniae. By 4 hr after subcutaneous inoculation with bacteria, the concentration of total and many individual free amino acids in serum, liver, and muscle was significantly decreased in comparison to findings in noninfected, pair-fed control rats. By use of a nonmetabolizable amino acid analogue (cycloleucine), it was possible to detect a flux of amino acids from muscle to liver in the infected rat. The endogenous amino acids which moved to the liver were rapidly utilized for the synthesis of serum proteins.
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Plasma levels of thyroxine (T4), triiodothyronine (T3) and growth hormone (GH) as well as the free T4 and free T3 index (FT4I, FT3I) in 20-month-old female Syrian hamsters kept under long daily photoperiod [light:dark (LD) cycles of 14:10] were significantly depressed compared to the values of 2-month-old animals kept under the same photoperiodic conditions. Cholesterol levels in old females were significantly elevated compared to those in young animals. In a subsequent experiment, young (4 month) and old (15 month) female hamsters were either placed in a short photoperiod (10:14 LD) or a 14:10 LD cycle and given daily afternoon injection of either diluent or 25 micrograms melatonin. After 8 weeks, the old females, regardless of treatment or photoperiod, had significantly lower T4 levels and higher cholesterol and triglyceride levels than did young animals. In 14:10 LD, FT4I and FT3I did not differ between young and old animals, possibly because of the reduced age gap in this experiment. Although the FT4I and FT3I in young females after 8 weeks of treatment with 10:14 LD or melatonin were not significant, the old females did demonstrate a significant suppression of their FT4I and FT3I values.