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G Weber

Publications and source records attributed to G Weber.

At least 631 records · Page 35Linked to original sources
PubMed1979

Rat liver glutamine 5-phosphoribosyl-1-pyrophosphate amidotransferase [EC 2.4.2.14]. Purification and properties.

Glutamine 5-phosphoribosyl-1-pyrophosphate (PRPP) amidotransferase (amidophosphoribosyltransferase), [EC 2.4.2.14] was purified 1,600-fold from rat liver. The preparation gave two protein bands on acrylamide gel electrophoresis, of which only the main band showed enzyme activity. The molecular weight of the enzyme was estimated to be 215,000, 200,000, and 195,000 by Sephadex G-150 gel filtration, polyacrylamide gel electrophoresis, and sucrose density grandient ultracentrifugation, respectively. The apparent Km values for glutamine and PRPP were 1.24 mM and 0.57 mM, respectively. The concentration-activity curve for PRPP changed from a hyperbolic to a sigmoidal form on addition of AMP or GMP, and this inhibition by AMP was prevented by increasing the PRPP concentration. In the presence of high concentrations of inorganic phosphate, the catalytic activity was decreased and the sensitivity to AMP inhibition was slightly increased. The molecular size of liver amidotransferase was not changed by the addition of PRPP, AMP, or 2-mercaptoethanol. The purified rat liver enzyme has a broad pH-range of activity between 6.5 and 8.5.

Amidophosphoribosyltransferase↗
PubMed1979

[Joint involvement].

Explore the source record for details and available documents.

Arthritis, Rheumatoid↗
PubMed1979

Circulating endothelial-like cells in arterial peripheral blood of hypercholesterolemic rabbits.

In blood smears obtained from the central ear artery of rabbits after 7 days of cholesterol-rich diet, a high number of well staining cells, morphologically very similar to endothelial cells may be found. After 15 days, macrophage-like cells are found in the smears together with degenerated (endothelial or macrophagic) cells. The presence of circulating endothelial cells is in agreement with the findings of de-endothelialized areas of aortic intima observed at scanning and transmission electron microscopy in short term hypercholesterolemic rabbits.

Animals↗
PubMed1979

[Morphokinetic effect of PMSG and sex steroids on parts of the cerebral-hypophyseal-gonadal axis of anestrous sheep].

The action of gonadotropins and of sexual steroids on links of the cerebro-hypophyseo-gonadal axis can be morphologically quantified in sheep. In that context, karyovolumetry is a highly dependabel and information-yielding quantitative morphological method. In studies conducted with anoestrous sheep and described in this paper that method has helped to detect an inhibitory effect of PMSG and progesterone upon the activity of neurons of the medial preoptic nucleus of the hypothalamus. The two sexual steroids produced even stronger inhibition of neuronal activity of the arcuate nucleus of the hypothalamus. Such results, when evaluated and re-used under the adequate test conditions might be helpful in identifying structures of central nervous disorders along the cerebro-hypophyseo-gonadal axis and produce reliable information on acting points or general action (activation or inhibition) of active substances as well as on the course of control and regulatory mechanisms.

Anestrus↗
PubMed1978

Characterization and comparison of poly(adenosine dephosphoribose) synthesis and DNA synthesis in nucleotide-permeable cells.

Using eukaryotic cells that have been rendered permeable to exogenously supplied nucleotides, we have characterized the activity of the poly(adenosine diphosphoribose) (poly(ADPR)) synthesis system and compared it to the DNA synthesis complex. The synthesis of poly(ADPR) is dependent on the presence of NAD and Mg2+. It does not require ATP, NaF or a monovalent cation. It is inhibited by N-ethylmaleimide. The reaction product conforms to the nuclease susceptibilities expected for poly(ADP ribose) in that it is degraded by venom phosphodiesterase but not by DNAase of RNAase. A comparison of the effects of inhibitors of poly(ADPR) synthesis and DNA synthesis clearly distinguishes between the two enzymatic systems. Nicotinamide, 5-methyl nicotinamide, thymidine, 5-bromo deoxyuridine, adenosine diphosphoribose, caffeine and formycin all inhibit poly(ADPR) synthesis but not DNA synthesis. In contrast, araCTP, cytembena and phosphonoacetic acid all inhibit DNA synthesis but not poly(ADPR) synthesis. Addition of DNAase to the permeable cells causes a marked stimulation of poly(ADPR) synthesis. L cells in logarithmic growth were found to have high levels of activity of the DNA synthesis complex and low levels of activity of the poly(ADPR) synthesis system. In contrast, cells at plateau phase density demonstrate a decrease in the activity of the DNA synthesis complex and a marked increase in activity of the poly(ADPR) synthesis system. When examined in the presence of added DNAase, the activity of the poly(ADPR) synthesis system is the same in cells obtained from log or plateau phase cultures. This indicates that the physiologic activity of the enzyme varies while the total amount of enzyme remains constant. When the permeable cells are allowed to synthesize both poly(ADPR) and DNA simultaneously, the synthesis of one polymer has no effect on the rate of synthesis of the other.

Cell Cycle↗
PubMed1978

Relation of poly(adenosine diphosphoribose) synthesis to DNA synthesis and cell growth.

A permeable cell technique has been used to measure the synthesis of DNA and poly(adenosine diphosphoribose) (poly(ADPR)) in mouse L cells subjected to different perturbations of cell growth. Cells leaving log phase growth and entering plateau phase, showed a decrease in DNA synthesis and an associated increase in intrinsic poly(ADPR) synthesis. In contrast to the variations in intrinsic poly(ADPR) synthesis, the total poly(ADPR) synthesis activity, measured in the presence of added DNAase, remained relatively constant during the fluctuations in cell growth status. Cells subjected to acute glucose deficiency also demonstrated a decrease in DNA synthesis and an associated increase in intrinsic poly(ADPR) synthesis. Similarly, cells infected with vaccinia virus demonstrated an abrupt cessation of DNA synthesis associated with an increase in poly(ADPR) synthesis. Treatment of cells with cytosine arabinoside, inhibited cellular DNA synthesis. This was also associated with an increase in the intrinsic activity of poly(ADPR) synthesis. However, in this case, the increase in poly(ADPR) synthesis was associated with an increase in activity of the DNA synthesis complex, despite the overall inhibition of cell DNA synthesis. These studies demonstrate, that in mouse L cells, suppression of DNA synthesis by multiple different physiologic mechanisms is always associated with an increase in intrinsic activity of poly(ADPR) synthesis.

Cell Cycle↗