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Biomedical subjects

J Neuwirt

Publications and source records attributed to J Neuwirt.

At least 55 records · Page 3Linked to original sources
PubMed1981

Decreased sensitivity to hydroxyurea and to [3H]thymidine suicide in the middle of the S phase.

Pluripotent haemopoietic stem cells (CFUs) move synchronously through the cell cycle in hydroxyurea-treated mice in a cohort 1--2 hr broad. Ten to fifteen hours after hydroxyurea they pass through S phase. DNA synthesis appears to be depressed 5--10 times when the cells are in the middle part of the S phase but does not seem to be completely interrupted. High concentrations of [3H]thymidine must be used for 'suicide' in order to achieve lethality for the cells with depressed DNA synthesis. At the time when DNA synthesis is depressed, the sensitivity of the cells to hydroxyurea also decreases. This may lead to a significant underestimation of the S phase fraction by the hydroxyurea method, because CFUs with low DNA synthesis rate are resistant to hydroxyurea although being in S phase.

Animals↗
PubMed1981

Effect of heme on globin messenger RNA synthesis.

Erythroid spleen cells from anemic mice were incubated with various inhibitors of heme synthesis. All the effective inhibitors of heme synthesis decreased the incorporation of labelled leucine into protein in spleen erythroid cells. Hemin completely restored protein synthesis to the control levels in isonicotinic acid hydrazide (INH) and penicillamine treated erythroid cells. These two specific inhibitors of heme synthesis were used for the study of the effect of heme on globin mRNA synthesis. Newly synthesized [3H]-uridine labelled globin mRNA was isolated by hybridization to globin cDNA covalently bound to the cellulose column. INH and penicillamine inhibited [3H] uridine incorporation into globin mRNA. The addition of hemin to INH or penicillamine treated cells almost completely restored globin mRNA synthesis. Moreover, hemin alone slightly increased the incorporation of [3H] uridine into globin mRNA. Similar results were obtained in experiments with Friend erythroleukemia cells of the Fw line. These cells are deficient in ferrochelatase enzyme activity and heme synthesis is not significantly increased after induction of differentiation by chemical inducers. The cells induced by butyric acid were incubated for 2 h with or without 100 muM hemin. The incorporation of [3H] uridine into globin mRNA was measured. A 38% increase in globin mRNA synthesis was seen in cells incubated with hemin as compared with cells incubated without hemin. These results seem to indicate that heme affects transcription or processing of globin mRNA precursors. Heme inhibitors also reduce [3H] uridine incorporation into other poly(A)-containing RNA in erythroid spleen cells incubated in vitro. In agreement with these results hemin causes increase of synthesis of some other poly(A)-containing RNA in Friend cells described above.

Animals↗
PubMed1981

Human placental conditioned medium (from different phase of pregnancy) as a source of colony-stimulating activity for cultures of human and mouse. granulocyte-macrophage colony-forming cells in semisolid agar.

We have investigated the effect of conditioned medium derived from cultures of human placental tissue from different phases of pregnancy on in vitro growth of human and mouse granulocyte-macrophage colony forming cells in semisolid agar. We have confirmed that the colony-stimulating activity of human placental conditioned (normal delivery) medium was equivalent to the activity of peripheral blood leucocyte underlayers when medium was added at a 5%-20% concentration to the semisolid agar. Placentas from the 12th amd 10th week of gestation were found not convenient for preparation of medium with high CSA; the activity of media prepared from their cultures was not significantly higher than the autostimulating activity of bone marrow alone. Human placental conditioned medium proved inconvenient for cultures of mouse GM-CFC in semisolid agar containing foetal calf serum.

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PubMed1981

Transplantation of bone marrow cells with changed haemoglobin type.

Haemoglobin was used as a marker for the detection of radiation chimera in rats. After a single blood loss, the synthesis of haemoglobin type had changed, as observed in peripheral blood one week after bleeding. After one month the haemoglobin pattern was the same in the experimental rats and in the control animals. Twenty-four hours before bone marrow transplantation the donors were bled. Haemoglobin synthesis had changed also in the recipients. In contrast with a single blood loss, this change of haemoglobin type persisted as observed one year after transplantation. The cells with changed synthesis can repeatedly be retransplanted.

Animals↗
PubMed1981

The role of heme in the regulation of iron uptake during Friend cell differentiation.

The inhibitory effect of hemin on iron uptake and heme synthesis was investigated in Friend erythroleukemia cells. In cells of line 707 the inhibition of iron uptake became more pronounced after the induction of erythroid differentiation by dimethyl sulfoxide. No such rise in sensitivity to hemin was found in cells of line Fw, which are deficient in ferrochelatase activity and do not synthesize hemoglobin after induction of differentiation by sodium butyrate. The possibility that hemin influences mainly the uptake of iron used directly for heme synthesis, and to a lesser extent intracellular storage of iron is discussed.

Animals↗
PubMed1980

Iron and transferrin distribution in reticulocytes incubated with heme synthesis inhibitors.

A high level of non-heme iron (either labelled or unlabelled) in mitochondria, ferritin and low-molecular-weight pool of reticulocytes was induced by preincubation with isonicotinic acid hydrazide or penicillamine together with either 59Fe- of 56Fe-labelled transferrin. Addition of apotransferrin during reincubation of 59Fe-labelled reticulocytes was accompanied by the transfer of 59Fe from low-molecular-weight pool to transferrin, which was found in the reticulocyte cytosol both free and bound to a carrier. Similarly, when cells were reincubated with 125I-labelled transferrin, more 125I-labelled radioactivity was found, in both free and carrier-bound transferrin peaks, in reticulocytes with a high level of low-molecular-weight cold iron than in control ones. These results suggest that transferrin enters reticulocytes and takes up iron from low-molecular-weight pool.

Animals↗
PubMed1980

Biliary iron excretion in rats following pyridoxal isonicotinoyl hydrazone.

Biliary excretion of iron after administration of pyridoxal isonicotinoyl hydrazone (PIH), a recently identified effective iron-chelating agent, was investigated in rats. PIH administered both intraperitoneally and orally was shown to increase significantly 59Fe excretion into bile of rats which had previously been injected with 59Fe-transferrin to label hepatic parenchymal cells. 59Fe-PIH appears in bile as early as 15 min after chelator administration and the peak of 59Fe-radioactivity in bile is seen 1--5 h following intraperitoneal PIH injection. PIH, administered intraperitoneally, 125--250 mg/kg, increased 24 h biliary radioiron excretion about 35 times and in addition increased urinary and faecal iron excretion. When PIH was given immediately before 59Fe-transferrin, 24 h cumulative biliary 59Fe excretion was even higher. PIH was also demonstrated to increase biliary excretion of radioiron released from 59Fe-haemoglobin catabolysed in reticuloendothelial cells. The effect of PIH was confirmed by estimation of biliary iron concentration using the method of atomic absorption spectrophotometry. Repeated PIH administration to rats decreased 59Fe radioactivity in liver and kidney and increased urinary and faecal iron excretion.

Animals↗
PubMed1979

Effect of some cytostatics on the haemopoietic stem cells (CFUs) in blood.

The effect of some cell-cycle stage-specific cytostatics on the pluripotent stem cells (CFUs) present in the blood was investigated. The amount of these cells in the blood responds markedly and very quickly to a single administration of any of these drugs. Their effects on the circulating CFUs allowed the drugs tested to be divided into groups: (1) Hydroxyurea and arabinosyl cytosine induced a profound decrease in the number of CFUs in the blood, which was followed by a return to the normal value and an overshoot that lasted several days; (2) Colchicine, vinblastine, vincristine, and methotrexate first induced an increase in the number of CFUs in the blood, which was followed by a decrease to below the normal values, and still later an overshoot that lasted several days. The preliminary data on the effect of hydroxyurea on the CFUs circulating in large quantities in the blood of mice with Friend virus leukaemia indicate that the tumorous stem cells (CFUs) might respond to these cytostatics in a similar way.

Animals↗
PubMed1978

Changes in stem cell compartments in mice after hydroxyurea.

Hydroxyurea injection kills only approximately 10% of CFUs which are in the S phase of the cell cycle. In mice given a single injection of hydroxyurea CFUs in the femur decreased only about 50% in 2--4 days after hydroxyurea, and then started to return to normal levels with an overshoot evident after the eighth day after hydroxyurea. CFUs in spleens of mice given a single injection of hydroxyurea show an evident overshoot as early as 3 days after the drug, reaching levels which are about 300% of normal. CFUs from blood disappear rapidly, but equally rapidly return to normal values followed by a significant overshoot. The radioresistance of mice increased up to 4 days after hydroxyurea.

Animals↗
PubMed1978

A contribution to the technique of mouse bone marrow cell culture in semisolid agar.

A method of cultivation of mouse bone marrow cells in semisolid agar is described. Colony-stimulating factor was provided either by a "feeder layer" containing kidney cells (from 8-day-old mice) or by the addition of "lung conditioned medium" or post-endotoxin serum. The effect of various factors and media on the formation of colonies was tested. The best growth of colonies was observed in medium RPMI 1640 or in Eagle's minimal essential medium containing 0.2% bactotryptose supplemented with 20% foetal calf serum. Both the morphology of cells found in the colonies and the proliferative state of the cells that give rise to colonies indicate that CFU-C represent the committed progenitor for myelopoiesis.

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