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Biomedical subjects

U Schmidt

Publications and source records attributed to U Schmidt.

At least 505 records · Page 28Linked to original sources
PubMed1975

Sodium- and potassium-activated ATPase. A possible target of aldosterone.

Na-K-ATPase activity was measured with an ultramicromethod in single portions of the proximal and distal convolution and of the thick ascending limb of Henle from adrenalectomized rats and after treatment with 5 mug aldosterone per 100 g body wt. The activity in all tubular structures returned to normal within 1 h after injection. This rapid activation of Na-K-ATPase induced by hormone was completely prevented by actinomycin D and cycloheximide. It appears that this aldosterone effect on Na-K-ATPase requires an intact protein synthetic process.

Adenosine Triphosphatases↗
PubMed1975

The diagnostic significance of liver cell inhomogeneity: serum enzymes in patients with central liver necrosis and the distribution of glutamate dehydrogenase in normal human liver.

16 Patients with acute right-sided cardiac failure associated with a high pressure of the central venous system, exhibited a marked increase in glutamate dehydrogenase activity in serum. This increase was 40-fold higher than in patients with acute viral hepatitis. Histological examination of seven deceased patients revealed central necrosis within the liver lobule. This observation led us to determine glutamate dehydrogenase activity in microdissected peripheral and central portions from the unchanged liver lobule. A 1.7-fold higher glutamate dehydrogenase activity was found in the central part of the liver lobule than in the peripheral portion. The diagnostic significance of the glutamate dehydrogenase activity distribution along the cords of liver cells is discussed in view of liver diseases with central necrosis.

Aged↗
PubMed1975

[Toxicology of epidithio-dioxopiperazines. 1. Studies on toxicity of cyclosarcosylsarcosineepitetrasulfide in guinea pigs and rats].

The present paper deals with the toxic effect of a mycotoxin of the group of epidithio-dioxopiperazines: cyclo-sarcosyl-sarcosin-epitetrasulfide, particularly upon the liver of guinea-pigs and rats. The sporidesmines, related to the compound tested, cause chronic obstructive cholangitis characteristic of a disease in sheep endemic in New Zealand. This type of cholangitis was attempted to be reproduced in order to establish an experimental model of producing biliary cirrhosis in animals. The acute and subacute LD50 in rats and guinea-pigs were determined intraperitoneally and intragastrally. In neither mode of application nor in short-term nor in chronic test could we find any specific, dose dependent changes of bile ducts. Merely, parenteral administration of lethal doses led to unspecific subcapsular liver necroses obviously due to direct diffusion of the toxic agent. The discrepancy between the efficacy of the toxic grass in New Zealand and the substance tested in the study is discussed.

Administration, Oral↗
PubMed1975

Hormonal effects on Na-K-ATPase of various parts of the rat nephron.

Aldosterone reactivates the impaired Na-K-ATPase very rapidly along the course of the distal tubule and in the proximal convolution. Surprisingly the latent period before enzyme induction parallels with the latent period before the restoration of active sodium reabsorption after a physiological dose of aldosterone [7]. Induction of Na-K-ATPase can be prevented by cycloheximide or actinomycin D, inhibitors of protein synthesis; this proves that protein synthesis is necessary for the induction of Na-K-ATPase. Although this kind of data can be interpreted as due to de-novo-synthesis for the induced enzyme this conclusion is not proved by such data. Another way of aldosterone action could exist in demasking inactive enzyme molecules which are already present in the membrane. Because of the very short latent period between aldosterone application and restoration of Na-K-ATPase we cannot exclude this possibility. The most important finding of our study is the rapid reactivation of the impaired Na-K-ATPase in the proximal and distal tubule after a single dose of aldosterone.

Adenosine Triphosphatases↗
PubMed1975

Metabolic patterns in various structures of the rat nephron. The distribution of enzymes of carbohydrate metabolism.

By means of the microdissection technique applied on kidney tissue, the following results were obtained: Hexokinase, an enzyme of glycolysis, revealed a low activity in the proximal and a high activity in the distal tubule. This distribution pattern is consistent with the finding that glucose is the main fuel for the distal tubule. Glucose-6-phosphatase, an enzyme of gluconeogenesis, demonstrates a significant activity in the distal tubule and in the glomerulus. Both structures are, however, no glucose producers. Phosphoenolpyruvate carboxykinase, the key enzyme of gluconeogenesis, is found only in the segments of the proximal tubule. The distal tubule lacks any activity. This is also the case during starvation and metabolic acidosis when gluconeogenesis is stimulated. Glutamic dehydrogenase, -an enzyme possibly connected with ammoniagenesis-, malate- and lactate dehydrogenase-, enzymes involved with hydrogen transfer through the mitochondrial membrane-, showed a close parallelism to phosphoenolpyruvate carboxykinase in their distribution along the proximal tubule. The bidirectional function of glyceraldehyde-P dehydrogenase is well documented by the close correlation to phosphoenolpyruvate carboxykinase (gluconeogenesis) in the proximal tubule and to pyruvic kinase (glycolysis) in the distal tubule.

Ammonia↗
PubMed1975

[Activity and properties of alkaline phosphatase in the plasma and various organs (kidney, liver, small intestine mucosa, bone) of the swine].

There was a high activity of alkaline phosphatase in the blood plasma of piglets during the first few days of live; enzyme obtained at this time had high heat stability and was readily inhibited by L-phenylalanine (5 mM). The enzyme in blood was inhibited to a greater extent than alkaline phosphatase from intestinal mucosa. With increasing age there was a fall in heat stability and in the ease with that the enzyme could be inhibited by phenylalanine. The proportion of alkaline phosphatase derived from bone and present in blood plasma increased with increasing age. Two isoenzymes were detected in liver, kidney, lung, intestinal mucosa and endometrial mucosa by electrophoresis in polyacrylamide gel. Heat lability and inhibition by phenylalanine were good criteria for differentiating different types of alkaline phosphatase in pigs. In the case of alkaline phosphatase in blood plasma, disodium phenylphosphate was split more readily than p-nitrophenyl phosphate and very much more readily than phenolphthalein diphosphate and beta-glycerophosphate.

Age Factors↗