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Biomedical subjects

R Schindler

Publications and source records attributed to R Schindler.

At least 109 records · Page 6Linked to original sources
PubMed1989

Control of ribonucleotide reductase in heat- and cold-sensitive mammalian cell-cycle mutants.

Two heat-sensitive (reversibly arrested in G1 phase at 39.5 degrees C, multiplying at 33 degrees C) and two cold-sensitive (reversibly arrested in G1 phase at 33 degrees C, multiplying at 39.5 degrees C) cell-cycle mutants of the P-815-X2 murine mastocytoma line were tested for ribonucleotide reductase activity, using cells made permeable to nucleotides. After transfer of the heat-sensitive mutant cells to 39.5 degrees C, ribonucleotide reductase activity, similar to thymidine kinase (Schneider, E., Müller, B. and Schindler, R. (1983) Biochim. Biophys. Acta 741, 77-85), but unlike DNA polymerase alpha (Schneider, E., Müller, B. and Schindler, R. (1985) Biochim. Biophys. Acta 825, 375-383), decreased rapidly and in parallel with numbers of cells in S phase, whereas in the cold-sensitive mutant cells brought to 33 degrees C, ribonucleotide reductase activity decreased approx. 8 h later than numbers of DNA-synthesizing cells. When arrested heat- or cold-sensitive mutant cells were returned to the permissive temperature, ribonucleotide reductase activities, similar to DNA polymerase alpha and to thymidine kinase in heat-sensitive mutants, increased essentially in parallel with reentry of cells into S phase, whereas the increase in thymidine kinase activity in the cold-sensitive mutants was previously shown to occur approx. one cell-cycle time later. This indicates that ribonucleotide reductase and thymidine kinase are coordinately expressed in the heat-sensitive, but independently regulated in the cold-sensitive mutants.

Animals↗
PubMed1989

A method for removing interleukin-1- and tumor necrosis factor-inducing substances from bacterial cultures by ultrafiltration with polysulfone.

The ability of human mononuclear cells (MNC) to produce cytokines is a highly sensitive and biologically relevant test system for the presence of microbial products. The safety of parenteral fluids is presently determined by gelation of the limulus amebocyte lysate (LAL) to endotoxin. In the present study, crude bacterial culture supernatants from Escherichia coli were subjected to ultrafiltration using polysulfone and the ultrafiltrates were tested for their ability to stimulate human MNC. Total interleukin-1 (IL-1) and tumor necrosis factor (TNF) produced by MNC were measured by radioimmunoassay. Endotoxin-like substances in E. coli cultures are rejected by a factor of at least 100,000. Rejection takes place by molecular size exclusion and by absorption. The sensitivity of the LAL and MNC cytokine production were comparable. These studies demonstrate a wide margin of safety for the production of parenteral fluids using ultrafiltration for endotoxin-containing materials.

Bacterial Toxins↗
PubMed1989

[High-resolution MR tomography of the hand: normal anatomy].

By using surface coils and a high resolution matrix, the images from MR tomography of small objects can be greatly improved. Normal subjects have been examined in order to demonstrate the usefulness of MR tomography for the examination of bones and soft tissues in the normal hand.

Adolescent↗
PubMed1989

Interferons as inhibitors of interleukin 1 induced interleukin 1 synthesis.

IL-1 induces its own gene expression in cultured smooth muscle and endothelial cells and in human PBMC. IL-1-induced IL-1 may be part of a self-amplification or autocrine event in inflammation. In the present study IFN gamma consistently increased LPS-induced IL-1, but reduced the total amount of IL-1-induced IL-1 from PBMC. On a molar basis, IFN gamma and IFN alpha 2 were equally effective. IL-6 also reduced IL-1 induced IL-1 but was approximately 300-fold less potent than the two interferons. The augmentation of LPS-stimulated IL-1 by IFN gamma was observed only when added at the same time as LPS, but IFN gamma could be added several hours after stimulation with IL-1 and still suppress IL-1 production. LPS-induced mRNA for IL-1 beta at 4 hours was enhanced by IFN gamma whereas IL-1-induced IL-1 beta mRNA was reduced by 70% in the presence of IFN gamma and this reduction was not due to increase degradation of IL-1 beta mRNA. These results suggest that in inflammatory tissues where IL-1 self amplification of its own gene expression is part of the pathological process, interferons may act to inhibit this cycle.

Humans↗
PubMed1988

Participation of mitochondrial proliferation in morphological differentiation of murine mastocytoma cells.

Proliferation of a cold-sensitive cell-cycle mutant isolated from an undifferentiated murine mastocytoma line is reversibly arrested at the nonpermissive temperature of 33 degrees C, and the arrested cells undergo morphological differentiation as expressed by the formation of metachromatic granules. Following transfer of these mutant cells from the permissive temperature of 39.5 to 33 degrees C, a transient increase in both cytochrome c oxidase and DNA polymerase gamma was observed, the ratio of total mitochondrial volume to cell volume nearly doubled within 6 days, and numbers of mitochondrial cross-sections per cellular cross-section as determined in electron micrographs underwent a threefold increase. Addition of chloramphenicol (100 micrograms/ml) to the mutant cell cultures 6 days prior to transfer from 39.5 to 33 degrees C prevented the increase in the ratio of total mitochondrial to cell volume. Furthermore, chloramphenicol markedly inhibited the increase in granule number per cell that normally is observed after transfer of cultures to 33 degrees C or during treatment with 1 mM butyrate, suggesting that mitochondrial proliferation may be an obligatory step in the process of morphological differentiation of these mastocytoma cells.

Animals↗
PubMed1988

Size and composition of liver vitamin A reserves of human beings who died of various causes.

Postmortem livers from 77 "normal" persons, 37 patients with neoplastic disease, 10 subjects with liver insufficiency, and 7 infants were analysed for free and esterified retinol. The average concentrations of total vitamin A for the members of each group were 597, 551, 289, and 162 micrograms/g wet liver, respectively. Compared with corresponding control values, both cancer victims and patients with liver disease had significantly lower hepatic vitamin A levels. With regard to the composition of the liver vitamin A reserves, our results show that approximately 97% of this vitamin was present as retinyl ester. Additionally, minute amounts of retinol were also found in most of the liver specimens analysed. In "normal" subjects the major ester fraction recovered was palmitate/oleate followed by stearate and myristate/linoleate. By contrast, the second most abundant fatty acid in the retinyl ester fraction of cancer victims was myristic/linoleic acid together with significantly smaller quantities of stearic acid. In tissue samples obtained from patients with liver disorders, however, the myristate/linoleate fraction was increased and therefore nearly equal amounts of both retinyl stearate and myristate/linoleate were present.

Cause of Death↗
PubMed1987

[Quantitative determination of vitamin A in liver and liverwurst using high pressure liquid chromatography (HPLC)].

Samples of liver sausage and liver tissue from slaughtered animals were analysed for pre-formed vitamin A. A sensitive reversed phase HPLC method with fluorescence detection was used to determine the amount of free and esterified retinol in extracts of these samples. Under our chromatographic conditions retinyl myristate and linoleate run together as do retinyl palmitate and oleate. The contents of all forms of vitamin A were expressed in milligrams of all-trans retinol per 100 g wet weight. The average concentrations of total vitamin A for turkey, pig, calf, beef, and chicken liver were 42.31, 38.15, 22.74, 14.98, and 13.22, respectively. In addition to these differences, the fatty acid composition of liver retinyl esters, as well as the amount of retinol, also varied considerably among species. Approximately 95% of the hepatic vitamin A was present as retinyl ester with retinyl palmitate/oleate as the main ester fraction. The second most abundant fatty acid in the retinyl ester fraction of calf, beef, and chicken liver was stearic acid followed by myristic/linoleic acid. An increment of retinol, however, was also found in these tissue samples. By contrast, in turkey liver the retinol fraction was increased and therefore both retinyl stearate and retinol were present in nearly equal amounts, whereas the retinyl ester fatty acids from pig liver contained relatively more myristate/linoleate and less stearate than those from liver of the other domestic animals (apparently a hallmark of pig liver). The retinol and retinyl ester pattern present in liver sausage was similar to, but not identical with, that of pig liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Is albumin synthesis regulated by the colloid osmotic pressure? Effect of albumin and dextran on albumin and total protein synthesis in isolated rat hepatocytes.

In order to study the influence of the colloid osmotic pressure on albumin and total liver protein synthesis, rat hepatocytes were isolated by collagenase perfusion and incubated in Krebs-Ringer-buffer for 4 h. The colloid osmotic pressure produced by different bovine serum albumin (BSA) or dextran 60 concentrations varied from 3 to 80 mm Hg. A physiological colloid osmotic pressure of 20 mm Hg was obtained with 5.7 g BSA or 3.7 g dextran 60 per 100 ml of buffer. Albumin synthesis was measured by Laurell rocket immunoelectrophoresis. Total liver protein and total secretory protein synthesis were determined by the measurement of 1-14C-leucine incorporation. Albumin synthesis was not primarily regulated by the colloid osmotic pressure as was demonstrated by a lack of inhibition after addition of BSA. There was no significant influence of the oncotic pressure on the incorporation of 14C-leucine into total liver proteins. The incorporation into total secretory proteins was inhibited by an increasing colloid osmotic pressure, mediated either by BSA or dextran, suggesting an inhibition of the secretion of plasma proteins other than albumin.

Animals↗
PubMed1986

Butyrate-induced cell differentiation of cell-cycle mutants and 'wild-type' mastocytoma cells: histamine, 5-hydroxytryptamine and metachromatic granules as independently regulated differentiation markers.

In cultures of heat-sensitive (hs; arrested at 39.5 degrees C, multiplying at 33 degrees C) and cold-sensitive (cs; arrested at 33 degrees C, multiplying at 39.5 degrees C) cell-cycle mutants that had been isolated from the same subclone (K21) of the murine P-815-X2 mastocytoma line, the degree of cell differentiation was assessed by determining the cellular histamine and 5-hydroxytryptamine (5-HT) content as well as the number of metachromatic granules per cell. The findings were compared with those obtained for 'wild-type' K21 and P-815-X2 cells. The addition of butyrate to 'wild-type' cells or to mutant cells maintained at the respective permissive temperature resulted in a relative increase in the level of all three differentiation markers. In cs mutant cells, essentially the same pronounced increase in granule numbers was observed during butyrate treatment at 39.5 degrees C and during incubation at 33 degrees C without butyrate, thereby suggesting that butyrate induces morphological cell differentiation in cs mutants via the same mechanisms as exposure to the nonpermissive temperature. In contrast, the histamine and 5-HT levels reached in hs and cs mutant cells in the presence of butyrate were higher than those observed during incubation at the nonpermissive temperature. Large quantitative differences were detected with respect to the potential of individual cell lines to express the three differentiation parameters. High levels of histamine were characteristic of 'wild-type' P-815-X2 cells treated at 33 degrees C with butyrate, while low amine levels and small numbers of granules were observed in K21 cells (i.e., the parent line of hs and cs mutants.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Transport of esterified retinol in fasting human blood.

The transport of retinyl palmitate in postabsorptive human blood has been investigated. For this purpose, lipoproteins were isolated from fasting serum of normal subjects as well as of patients with various diseases. The serum retinyl palmitate values of these individuals ranged from 2.0-30.3 micrograms/100 ml, with a mean value of 7.6 micrograms/100 ml. In the 14 human subjects investigated, 68.1% of the recovered retinyl palmitate was associated with the VLDL fraction and 28.9% with the LDL fraction. Nevertheless, the individual pattern of retinyl palmitate distribution among VLDL and LDL differed considerably within this group. No esterified retinol, however, was detected in the HDL as well as in the nonlipoprotein fraction (d greater than 1.21 g/ml) of human serum. It is concluded that the transport of esterified retinol in fasting blood is not restricted to chylomicron remnants. Nevertheless, in humans the serum transport of retinyl palmitate is preferentially mediated by lipoproteins of the VLDL fraction.

Adult↗