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Biomedical subjects

R Wiesner

Publications and source records attributed to R Wiesner.

88 records · Page 5Linked to original sources
PubMed1982

Physiology of 24,25-dihydroxyvitamin D3 in normal human subjects.

We determined the metabolic clearance and production rates of 24,25-dihydroxyvitamin D3 in four normal healthy adults. We also examined the excretion of radioactivity in stool, urine, and bile after the intravenous administration of 24,25-[3H]dihydroxyvitamin D3 to human subjects. 24,25-Dihydroxyvitamin D3 is rapidly cleared from the plasma with a half-life of approximately 390 +/- 25 min (mean +/- SE). The metabolic clearance rate of 24,25-dihydroxyvitamin D3 was 9.2 +/- 1.5 liters/day with a production rate of 26.4 +/- 7.2 micrograms/day (mean +/- SE). Within 1 day 13.0 +/- 4.2% (mean +/- SE) of the administered dose had appeared in the stool; by day 7, 48.8 +/- 2.7% of the dose had appeared in the feces. Within 24 hr, 6.4 +/- 0.8% of the administered dose appeared in the urine; 7.4 +/- 1.8% of the dose had appeared in the urine within 2 days. The biliary excretion of 24,25-dihydroxyvitamin D3 was studied in two subjects. By 8 h, 15.3 +/- 1.3% of the administered dose had appeared in the bile. The metabolites present in bile, feces, and urine were much more polar than 24,25-dihydroxyvitamin D3. These results demonstrate that 24,25-dihydroxyvitamin D3 is rapidly cleared from plasma and is excreted in the feces (probably via the bile) and urine of normal human subjects.

24,25-Dihydroxyvitamin D 3↗
PubMed1981

Blocking by the carcinogen, L-ethionine, of SOS functions in a tif-1 mutant of Escherichia coli B/r.

In Escherichia coli, DNA damage by carcinogenic agents results in the coordinate expression of a diversity of functions (SOS functions), many of which are thermally inducible without any damage to DNA in a tif-1 mutant. These include prophage induction, filamentous growth, and an error-prone DNA repair activity, which is responsible for ultraviolet-induced mutagenesis. Ethionine causes hepatic carcinoma in rats after prolonged feeding but is not a mutagen in the Ames test. The present study shows that 10 mM ethionine prevents the thermal induction of lambda-prophage in a tif-1 derivative of E. coli. The enhancement of mutation, which normally occurs at high temperature after a low dose of ultraviolet light, is also blocked by ethionine. Ethionine does not block, to any appreciable extent, the incorporation of radioactive precursors into RNA, DNA, or protein.

DNA↗
PubMed1980

Soybean diet lowers breast tumor incidence in irradiated rats.

This paper examines the relationship between feeding a diet rich in protease inhibitors and the reduction of mammary cancer induced by x-irradiation in Sprague-Dawley rats. Of a total of 145 irradiated animals, 44% of the 45 rats fed a raw soybean diet containing a high concentration of protease inhibitor developed mammary tumors as compared to 74% of 50 rats fed a casein diet containing no protease inhibitor. Animals fed Purina rat chow which contained low levels of protease inhibitor exhibited a 70% mammary tumor incidence. No spontaneous neoplasms were found in any of the non-irradiated animals on the raw soybean diet whereas about 10% of the animals on the protease-free diet developed tumors. Thus, soybeans which are rich in protease inhibitors reduced the induction of mammary cancer in x-irradiated rats. This work suggests that diets rich in protease inhibitors may contribute to reducing cancer incidence in man.

Animals↗
PubMed1979

The lipoxygenase of reticulocytes. Purification, characterization and biological dynamics of the lipoxygenase; its identity with the respiratory inhibitors of the reticulocyte.

A lipoxygenase has been purified from rabbit reticulocyte-rich anaemic blood cells. It possesses a molecular weight of 78 000 and an isoelectric point of 5.5 and contains 5% neutral sugars and two iron atoms per enzyme molecule. The lipoxygenase has proved to be identical with the inhibitors of respiratory proteins described formerly. The actions of the lipoxygenase on linoleic acid, phospholipids, mitochondrial and erythrocyte membranes and electron transfer particles were studied. A special feature of the reticulocyte lipoxygenase is the suicidal character of its action on lipids. With electron transfer particles the reticulocyte lipoxygenase causes a loss of acid-labile sulfur which accompanies respiratory inhibition; the strong respiratory inhibition is not exerted by soybean lipoxygenase. The reticulocyte lipoxygenase acts preferably on mitochondrial membranes as compared with cell membranes of the erythrocyte; erythrocyte cytosol moderates the action on mitochondrial membranes. Furthermore, the lipoxygenase reaction can concomitantly and irreversibly inactivate sulfhydryl enzymes as demonstrated with muscle glyceraldehyde-3-phosphate dehydrogenase. The occurrence of the lipoxygenase here described is restricted to reticulocytes; very low amounts were observed in bone marrow and no lipoxygenase was detectable in normal blood. During the course of an experimental anaemia the lipoxygenase is produced owing to superinduction in large amounts, which may persist for a long time since they escape inactivation. Preliminary evidence was obtained for the occurrence of other lipoxygenases in tissues of lung, spleen, kidney and also epithelial tumours.

Amino Acids↗
PubMed1977

[Purification and characterization of the respiratory inhibitor RF from rabbit reticulocytes].

In the stroma-free hemolysate of rabbit reticulocytes there exists a respiratory inhibitor (RF) of protein nature. It could be purified by the following procedure: (NH4)2SO4-precipitation leads to DEAE-Sephadex A-50-chromatography leads to isoelectric focusing leads to gelfiltration on Sephadex G-200. In addition to the activity the identity of the inhibitor could be proved immunologically at all steps of the purification. A molecular weight of about 80,000 was determined by gelelectrophoresis in the SDS-mercaptoethanol-system. The protein has an IP of 5.55--5.65 and consists of one polypeptide chain. This could be shown both by SDS-gelelectrophoresis and by estimation of only one N-terminal amino acid residue (glycine). Only after oxidation with performic acid the amino acid analysis of the protein gives reproducible values. The sum of weight-% is about 80 (without Tyr). The polarity of the protein with 41 mol-% agrees with the polarity of soluble globular proteins investigated by other authors. Acid hydrolysis without preceeding performic acid oxidation gives a sum of amino acid residues of only 35--45 weight-%, the glycoprotein nature of the inhibitor could be shown by staining the SDS-gels with Schiff's reagents and by carbohydrate determination with anthrone reagent.

Animals↗
PubMed1975

Mitochondrial protein synthesis and the stimulation of steroidogenesis by cyclic adenosine 3',5'-monophosphate in isolated rat adrenal cells.

The stimulation by cyclic AMP of steroidogenesis in rat adrenal cells isolated by trypsin treatment was inhibited by D-threo-chloramphenicol and by its L-threo-isomer. The former is an inhibitor of mitochondrial protein synthesis while the latter is not. Both substances, at concentrations which inhibit steroidogenesis, inhibit amino acid incorporation into the proteins of microsomes. Inhibition in other subcellular fractions also occurs depending on the isomer and its concentration. In no case was there a preferential inhibition of amino acid incorporation into mitochondrial proteins. Carbomycin, another inhibitor of mitochondrial protein synthesis, gave similar results. In addition, subfractionation of mitochondria in these experiments revealed no preferential inhibition of amino acid incorporation into the proteins of either the soluble of membrane fractions of this organelle. The above results were obtained at several concentrations of the inhibitors when only partial inhibition of steroidogenesis was present. Both isomers of chloramphenicol inhibited steroidogenesis in a cell-free system to an extent equal to that found with cyclic AMP-stimulated steroidogenesis in intact cells. It is concluded that these inhibitors of mitochondrial protein synthesis have multiple metabolic effects in adrenal cells.

Adrenal Glands↗
PubMed1975

Concerning the relationship between protein synthesis and adenosine-3',5'-cyclic phosphate-stimulated steroidogenesis in isolated rat adrenal cells.

Inhibitors of protein synthesis decrease protein synthesis in isolated rat adrenal cells to a greater extent than they decrease adenosine-3',5'-cyclic phosphate (cyclic AMP)-stimulated steroidogenesis. At low concentrations of the inhibitors, varying degrees of recovery of the rate of steroidogenesis occurs with increasing time of incubation. As the concentration is increased, the time required to achieve any recovery of the rate of steroidogenesis increases and the extent of recovery decreases. The recovery also depends on the amount of cyclic AMP present. During the process of recovery the inhibition of protein synthesis continues in a linear manner. An explanation consistent with these data involves a rapidly turningover protein, the concentration of which is independent of the level of cyclic AMP present. However, the extent of transformation of this protein to an active form depends on the concentration of cyclic AMP.

Adrenal Cortex↗
PubMed1965

Degradation of ribonucleic acid in mouse fibroblasts treated with actinomycin.

The cellular RNA content of mouse fibroblasts incubated with actinomycin decreases at a rate of about 1 to 1.5 per cent per hour, while DNA and protein content remain unchanged. This degradation affects nuclear and cytoplasmic RNA, ribosomal and soluble RNA. The breakdown products appear quantitatively in the acid-soluble fraction of the cells and the medium. Polynucleotides synthesized a short period (120 minutes) prior to exposure to actinomycin are degraded before those synthesized 8 to 12 hours previously.

Animals↗