Subject(s)
Diet , Hypothalamus/metabolism , Norepinephrine/metabolism , Probenecid/pharmacology , Serotonin/metabolism , Stress, Physiological/metabolism , Adaptation, Physiological/drug effects , Animals , Body Temperature/drug effects , Cold Temperature , Male , Rats , Rats, Inbred Strains , Restraint, PhysicalABSTRACT
A commercial chow and a semipurified diet fed for 14 days to Sprague-Dawley male rats kept under standardized conditions of temperature, humidity, and light had different effects on a series of parameters related to the metabolism of central serotonin and noradrenaline. Rats fed the commercial chow had (1) a lower serum level of the six neutral amino acids (valine, isoleucine leucine, tyrosine, phenylalanine, and methionine) known to compete with tryptophan for its entry into the brain, (2) a higher ratio of tryptophan to the sum of the six neutral amino acids, (3) a lower ratio of tyrosine to the other five neutral amino acids, (4) a lower ratio of serotonin to 5-hydroxyindoleacetic acid in hypothalamus, (5) a higher tryptophan hydroxylase activity in raphe nuclei, and (6) a higher content of noradrenaline in hypothalamus. It is suggested that chow fed rats had a more active central serotonin metabolism in hypothalamus than rats fed the semipurified diet.
Subject(s)
Animal Feed , Brain/metabolism , Norepinephrine/metabolism , Serotonin/metabolism , Amino Acids/metabolism , Animals , Diet , Hydroxyindoleacetic Acid/metabolism , Male , Raphe Nuclei/metabolism , Rats , Tryptophan Hydroxylase/metabolismSubject(s)
Acclimatization , Cold Temperature , Diet , Animals , Blood Glucose/analysis , Corticosterone/blood , Glycogen/metabolism , Male , RatsSubject(s)
Acclimatization , Body Weight , Circadian Rhythm , Periodicity , Animals , Diet , Magnetics , Male , Rats , TemperatureSubject(s)
Calcium/metabolism , Cold Temperature , Longevity , Magnesium/metabolism , Acclimatization , Adaptation, Physiological , Adipose Tissue, Brown/metabolism , Animals , Body Composition , Body Temperature , Body Weight , Heart Diseases/etiology , Lipid Metabolism , Magnesium Deficiency , Male , Organ Specificity , Rats , Stress, Physiological , Time FactorsABSTRACT
Magnesium (Mg) and calcium (Ca) balances as well as determinations of atomic absorption analysis of atomic absorption analysis of total absolute contents of Mg and Ca fat-free dry carcasses were done on gnotobiotic male Sprague-Dawley rats, kept at 28 degrees or 6 degrees, for 69, 240, or 517 days, and fed either a commercial stock diet or a semipurified diet containing a normal or a subnormal amount of Mg. The often-reported observation of negative balances when Mg intake is subnormal has been confirmed. Total Mg and Ca accumulation in the carcass estimated from balance values was totally inconsistent with the actual content of the carcass as determined by direct analysis. The large discrepancy between the actual analysis of the carcass and the estimated content of Mg and Ca in the carcass derived from balance data demonstrates clearly that balance of trace minerals cannot reflect chronic retentions or losses of these minerals. Possible explanation of this discrepancy are dissussed.
Subject(s)
Body Composition , Calcium/metabolism , Magnesium/metabolism , Animals , Calcium/urine , Feces/analysis , Magnesium/urine , Neutron Activation Analysis , Preservation, Biological , Rats , Spectrophotometry, AtomicABSTRACT
Sprague-Dawley rats were kept at 28 degrees C from 21 to 517 days age and fed one of the two following diets: a semi-purified diet containing 502 p.p.m. of Mg (control) or the same diet containing only 120 p.p.m. (mg/kg) (low-Mg). The chronic suboptimal intake of Mg by rats fed the low-Mg diet did not result in overt signs of Mg deficiency even when Mg levels were greatly reduced in carcass, plasma, and tibia, but it significantly decreased bone strength. It is suggested that Mg deficiency in man could be a factor in the weakening of bone, commonly observed in old age, even when there are no visible signs of Mg deficiency. Studies of the human situation would be of interest.
Subject(s)
Bone and Bones/physiopathology , Magnesium Deficiency/physiopathology , Magnesium/metabolism , Animal Feed/analysis , Animals , Bone and Bones/metabolism , Calcium/metabolism , Diet , Feces/analysis , Male , Muscles/analysis , Rats , Water/analysisABSTRACT
Following either chronic exposure to 6 degrees C, or outdoor winter exposure, or chronic treatment with tyramine rats were exposed to -40 degrees C and their oxygen consumption and colonic temperature monitored. Fall in body temperature with time of exposure followed a sigmoid curve which had an inflection point around 32.9 degrees C. Both the time required for body temperature to reach this point and hypothermic resistance defined as the total O2 consumed up to the inflection time were useful indices of resistance to severe cold; Three days before the cold tests, capacity for norepinephrine-induced nonshivering thermogenesis was measured in all animals by examination of their metabolic response to tyraminemthe magnitude of response to tyramine correlated well with hypothermic resistance only for those rats chroncally treated with tyramine. It is concluded that it is impossible to predict with any reasonable degree of confidence the cold resistance of a rat from its tyramine response. In cold-acclimated rats, factors in addition to norepinephrine sensitivity are significantly involved in cold resistance and deserve further studies.
