Search PubMed⌕ Search

Biomedical subjects

W Reutter

Publications and source records attributed to W Reutter.

At least 199 records · Page 11Linked to original sources
PubMed1978

Induction and 'superinduction' of sialylation of membrane-bound gamma-glutamyltransferase during liver regeneration.

The present paper shows that in the regenerating rat liver the membrane-bound-gamma-glutamyltransferase exists in two molecular forms. Depending on the state of proliferation, a sialic-acid-rich enzyme (in the fetal or regenerating liver) or a sialic-acid-poor enzyme (in the adult or quiescent liver) could be detected. In regeneration liver (24 h after 2/3 resection) only the sialic-acid-rich or fetal enzyme could be found. Since total enzyme activity (adult + fetal type) remained unchanged, it is assumed that the adult type of gamma-glutamyltransferase was modified by sialylation during the initial phase of liver regeneration. This process of sialylation was prevented by inhibitors of RNA or protein synthesis such as D-galactosamine, actinomycin D or cycloheximide, provided that the inhibitor (D-galactosamine) was given within the first 8 h after partial hepatectomy. Sialylation was not impaired by inhibitors of DNA synthesis, e.g. hydroxyurea or cytosine arabinoside. Administration of actinomycin D during a defined phase of proliferation (24 to 48 h after partial hepatectomy) stimulated the transfer of sialic acid to gamma-glutamyltransferase, a finding which describes for the first time the so-called 'superinduction' of a sialylation process.

Animals↗
PubMed1978

Lower gastric secretion and higher incorporation of orotic acid into liver RNA in rats treated with 5-azacytidine and cycloheximide.

Out of different azapyrimidines tested for their ability to affect metabolism of orotic acid in the liver of rats kept on food only 5-azacytidine resulted in the enhanced incorporation of orotate into liver RNA following 24 hr pretreatment. Similar effect was observed also in cycloheximide-treated animals. No stimulation of orotic acid utilization following 5-azacytidine or cycloheximidine treatment was observed in the liver of starved animals. Both drugs (but not other pyrimidine analogues tested) depressed markedly gastric secretion in rats and caused decreased evacuation of the stomach. The decreased secretion of pepsin and lower gastric acidity resulting in drug-simulated starvation of the treated animals are discussed in relation to the enhanced uptake of orotic acid into liver RNA.

Animals↗
PubMed1977

[Concanavalin A- Sepharose affinity chromatography for routine microanalysis of gamma-glutamyltransferase (author's transl)].

The separation of two molecular forms of liver gamma-glutamyltransferase is achieved by Con A-Sepharose chromatography, an adult type with high affinity to Con A and a fetal type without binding capacity to this lectin. Now we present a new method using micro-columns for affinity chromatography (gel volume 2 ml). By this rapid and inexpensive procedure it is possible to study this enzyme separation for its use in the diagnosis of liver diseases.

Chromatography, Affinity↗
PubMed1977

Guanylate cyclase activity and cyclic nucleotide concentrations during liver regeneration after experimental injury.

Cyclic nucleotide concentrations and guanylate cyclase activity were measured in regenerating rat liver. Previous work has shown that in livers of partially hepatectomized rats the activity of a membrane-bound guanylate cyclase increases considerably during the early replicative phase [Kimura & Murad (1975) Proc. Natl. Acad. Sci. U.S.A.72, 1965-1969; Goridis & Reutter (1975) Nature (London) 257, 698-700]. Over the same time period after partial hepatectomy, increased tissue concentrations of cyclic GMP were found when the rats were killed under pentobarbital anaesthesia, but not when anaesthesia was omitted. The results obtained on hepatectomized livers were compared with the changes in guanylate cyclase activity and cyclic nucleotide concentrations during the response to galactosamine treatment. Here, a peak of guanylate cyclase activity and of cyclic GMP concentrations occurred at 8h, that is before the beginning of the proliferative response. Both parameters were normal at the time of increased DNA synthesis. There does not, therefore, seem to be a consistent correlation between changes in guanylate cyclase activity or concentrations of cyclic GMP and an increase in liver DNA synthesis. A modest rise in cyclic AMP concentrations was found, however, in livers of galactosamine-treated rats, which was coincident with the time of DNA synthesis.

Animals↗
PubMed1977

Glycosyltransferases and glycosidases in Morris hepatomas.

The following three parameters were studied in Morris hepatomas of different growth rates: (a) the specific activity of guanosine dephosphate (GDP)-fucose:glycoprotein fucosyltransferase and cytidine monophosphate (CMP)-N-acetylneuraminic acid:glycoprotein sialyltransferase, (B) the content of GDP-fucosee and CMP-N-acetylneuraminic acid, and (c) the activity of alpha-L-fucosidase and neuraminidase. Fucosyltrasferase activities were significantly elevated in all hepatomas investigated. Especially high levels of enzyme were measured in the rapidly growing tumors 7777, 66, and 3924A. The increase varied between 2- and 3-fold when compared with the corresponding host liver. Conversely, the activity of the sialytransferase was greatly decreased in all hepatoma lines with a rapid or intermediate growth rate. In the fast-growing tumor 9618A2, the activity was reduced to 8%. GDP-fucose and CMP-N-acetylneuraminic acid were determined by the isotope dilution technique. In normal rat liver from Buffalo or ACl rats, the concentration of GDP-fucose was 6.5+/-0.9 and 9.5+/-1.1nmoles/g, wet weight, respectively. In the fast-growing hepatomas 3924A and 9121, levels up to 21.5 nmoles/g, wet weight, were found, However, the content of CMP-N-acetylneuraminic acid in hepatomas was indluenced to a lesser extent by the degree of differentiation of the tumor. In the most rapidly growing tumor, 9618A2, a level of alpha-L- fucosidase seven times higher than in host liver was determined. Moreover, there existed a correlation bewteen the age of the hepatoma and enzyme activity. Within the 2nd week after inoculation, fucosidase activity increased from 130 to 343 nmoles/hr/mg of protein. Neuraminidase was measured in a new linked assay system. The activity of this enzyme was lowered by 50% or was at least unchanged when compared to the activity in host liver. Our results indicate that specific alterations of fucose metabolism are a characteristic feature of Morris hepatomas.

Animals↗
PubMed1976

Investigations on d-galactosamine hepatitis after pretreatment with alpha-hexachlorocyclohexane.

D-Galactosamine hepatitis cannot be induced in rapidly replicating liver tissue at various times after induction of proliferation. Proliferation was induced by administration of alpha-hexachlorocyclohexane. The morphological features of galactosamine hepatitis do not appear or are very mild. The onset of DNA synthesis is delayed to about 12 hrs as also shown in partially hepatectomized rats.

Alcohol Oxidoreductases↗
PubMed1975

The appearance of D-galactosamine-induced hepatitis and generalized edema in adrenalectomized rats.

In adrenalectomized female rats a single dose of 375 mg D-galactosamine.HCl per kg of body weight produces both hepatitis and generalized edema with ascites. These alterations depend upon the dose and the time interval after injection of the aminosugar. The effect is specific for D-galactosamine; 2-deoxy-galactose produces only edema and no hepatitis, whereas D-glucosamine and D-galactose are without any measurable effect. In male adrenalectomized animals D-galactosamine produced hepatitis alone; fluid extravasation occurs only after additional orchiectomy. Glucocorticoids given before or simultaneously with D-galactosamine are able to prevent the animals from gettin edema and to ameliorate hepatitis, while mineralcorticoids do not show any effect on these alterations. It is evident that the effects of D-galactosamine on the hepatocyte and on the endothelial cells are independent from each other. This leads to the conclusion that D-galactosamine acts at least upon two different target organs, the liver and the reticulo-endothelial system in general.

Adrenalectomy↗