Biomedical subjects
Publications and source records attributed to N Marcondes.
TRH was studied in rats with chronic Chagas disease. It was found an increased secretion of TSH 60 minutes after intraperitoneal injection of the hypothalamic hormone. T3 and T4 were also decreased in basal conditions. This may indicate a primary hypothyroidism.
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Plasmalogens have been determined in blood plasma, arterial and myocardial tissue of rats intubated with an atherogenic diet (vitamin D2 + cholesterol). These lipids are significantly decreased in arterial tissue after the administration of these substances for 5 consecutive days. Folic acid involved in the synthesis of plasmalogens and a powerful inhibitor of xanthine oxidase, on the contrary, increases enormously the concentration of plasmalogens in arterial tissue even with an atherogenic diet.
Urease obtained from seeds of Citrullus vulgaris fruits has been studied under three points of view: a) the effect of the urea analogs acetamide and hydroxi-urea on the enzyme kinetic b) the action of the sulfhydryl reagents and the reactivation agents on the enzyme c) the effect of X-rays and the protective action of the cysteamine. The Berthelot reaction for the determination of the liberated NH3 was used enzyme activity. Acetamide has no effect on urease kinetic. Hidroxy-urea which produces a typical green color when it is mixed with the Berthelot reagents at high concentrations, when properly diluted acts a aompetitive inhibitor of urease. Spectrophotometric experiments suggest that the studied urease decomposes hydroxi-urea with liberation of hydroxilamine. The sulphydril reagent, p-hydroxi-mercuribenzoate inhibits the enzime. Cysteine and dithiotreitol reactivate the enzyme activity in no more then 50% even when excess of the substances is used. Probably only in the first step of the urea hydrolysis, the enzyme behaves as a typical SH-enzyme. Urease is very sensitive to X-rays. Cysteamine acts as a protective agent of the enzyme. Dithiotreitol reinforces this protective action. This effect is clearly observed when the Fisbein catalytic method for urease is employed.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.