Biomedical subjects

H Bessler

Publications and source records attributed to H Bessler.

At least 127 records · Page 7Linked to original sources

PubMed1977

Effect of a low dose of vincristine on platelet production in mice.

The effect of a single low dose (0.1 mg/kg) of vincristine (VCR) on platelet production was investigated in C57B1 mice. A parallel increase of circulating platelets and (75Se)-selenomethionine (Se-Met) uptake was observed. The total megakaryocyte count decreased insignificantly 6 hours after VCR injection, followed by an increase after 18 hours. Plasma taken from mice 24 hours after VCR injection was tested for thrombopoietic activity. The post-VCR plasma caused a significant thrombocytosis, increased Se-Met uptake and increased protein synthesis of the platelets, indicating an active overproduction of platelets. These results suggest that the thrombocytosis induced by a low dose of VCR is mediated by a thrombopoietin-like substance.

Animals↗

PubMed1976

Increased protein synthesis by human platelets during phagocytosis of latex particles in vitro.

A three-fold increase of protein synthesis by human platelets during in vitro phagocytosis of polystyrene latex particles was detected. During the first two hours of incubation, the percentage of phagocytizing platelets and the number of latex particles per platelet increased; by the end of the third hour, the first parameter remained stable, while the number of latex particles per cell had decreased. Vincristine (20 mug/ml of cell suspension) inhibited platelet protein synthesis. This effect was both time- and dose-dependent. The drug also caused a decrease in the number of phagocytizing cells, as well as in their phagocytotic activity.

Blood Platelets↗

PubMed1976

In vitro DNA and RNA synthesis by human platelets.

In vitro incorporation of [Me-3H] thymidine and [5-3H] uridine into human platelets was demonstrated. Thymidine incorporation was inhibited by three specific inhibitors of DNA synthesis: hydroxyurea, cytosine arabinoside and daunomycin. The effect was dose-dependent. Uridine uptake by platelets was found to be inhibited by specific inhibitors of RNA synthesis such as actinomycin D, rifampicin and vincristine, the effect of actinomycin D being dose dependent. The drug also led to a time-dependent inhibition of protein synthesis when preincubated with platelets. The platelet RNA profile on polyacrylamide gel was demonstrated to be similar to that of embryonic mouse erythroblast RNA. Synthesis of all three fractions, 28 S, 18 S and 4 S, was inhibited by actinomycin D. These findings show that human platelets are capable of DNA and RNA synthesis, and that these activities play a role in controlling protein synthesis in these cells. Detectable amounts of DNA have been found in whole human platelets, and in isolated mitochondria derived from these cells. Isolated platelet mitochondria incorporated [3H] thymidine and [3H] uridine into their macromolecules. These activities were inhibited by daunomycin and by both rifampicin and actinomycin D, respectively. These results support the assumption that DNA and RNA synthesis found in intact cell preparations takes place most probably in platelet mitochondria.

Blood Platelets↗

PubMed1976

Chloramphenicol induced inhibition of platelet protein synthesis: in vitro and in vivo studies.

Chloramphenicol (CAP), an antibiotic which causes various blood dyscrasias, was shown to inhibit in vitro protein synthesis of human blood platelets. The effect is dose- and time-dependent, it is reversible after incubation for 2 h, and is comparable with the suppression achieved by cycloheximide (CXM). Electron microscopic examination revealed swelling and destruction of mitochondria. Administration of CAP to dogs produced a progressive inhibition of platelet protein synthesis as shown by a reduction in the rate of [3H]leucine incorporation into protein. The maximal inhibitory effect of the antibiotic was reached 0.5-4.0 h after its administration, when minimal leucine incorporation values of 9-40% of the control were measured. The suppressive effect of CAP was followed by an overshoot in the incorporation of [3H]leucine, up to a maximum of 602% of the value at zero time of the experiment.

Animals↗

PubMed1976

Erythropoietic events in cultured embryonic mouse spleen.

The events of erythropoiesis in cultured embryonic mouse spleens isolated on the 12th day of gestation were compared with those occurring in spleens of corresponding gestational days in vivo. It was found that the development of erythroid precursors in the cultured spleen depended on the presence of erythropoietin in the culture medium. A progressive increase in the number of erythroid precursors, with a marked shift to mature cells, was observed in spleens cultured with erythropoietin. Although the origin of the hemocytoblasts in the spleen isolated in the earliest stage of its development remains obscure, the present study provided evidence that erythropoiesis in the embryonic mouse spleen was indigenous to this organ and did not result from colonization of erythroid precursors originating in the liver.

Animals↗

PubMed1975

Hematopoiesis in the embryonic mouse spleen. II. Alterations after phenylhydrazine administration to the mothers.

The effect of phenylhydrazine (PHZ) on the hematopoietic events in the embryonic spleen of C57Bl/6J mice was examined by light and electron microscopy. Following PHZ in injections to the mothers, the embryonic spleen revealed a marked increase in erythroid precursors, with a shift to mature cells. This phenomenon was part of a more generalized stimulation of erythorpoiesis, expressed by a shift to mature red cell precursors in the embryonic livers and an increase in the percentage of non-nucleated cells in the embryonic peripheral blood. Concomitantly stimulation of phagocytosis in the spleen of embryos in the early gestational days and increased vascularity were observed, and a later effect of granulocytopoietic stimulation. The effect on erythropoiesis in the embryonic spleen might be a sequence of erythropoietin stimulation, either in the mothers or the fetuses, due to anemia and hypoxia following PHZ injections.

Anemia↗

PubMed1975

Paroxysmal cold hemoglobinuria. Transmission and scanning electron microscopy features of erythrocytes.

Djaldetti, Meir, Elion, Dorith, Bessler, Hana, and Fishman, Pnina: Paroxysmal cold hemoglobinuria. Tranmission and scanning electron microscopy features of erythrocytes. Am J Clin Pathol 63. 804-810, 1975. The case history of a patint with paroxysmal cold hemoglobinuria of the chronic iduipathic type is reported. The patient showed a marked dependency on the external temperature, with severe hemolytic anemia and hemoglobinuria during the winter. Examination of the erythrocytes with the transmission electron microscope showed abnormal forms identified as ropalocytes, whereas examination with the scanning electron microscope revealed "holes" in the erythrocytes. (Key words: Paroxysmal cold hemoglobinuria' Ultrastructure of erythrocytes.

Adult↗

PubMed1975

Transfer of iron-dextran across the placenta.

In pregnant mice. 55Fe-labeled iron-dextran (Imferon) is transferred across the placenta. It was detected in the bone marrow, liver, spleen and peripheral blood of the pregnant animal, as well as in the embryonic liver erythroid precursors and peripheral blood. Uptake by liver and peripheral blood cells of pregnant anemic mice and by liver erythroid precursors of anemic embryos was significantly higher than in normal control animals. Electron-microscopic examination revealed that the iron deposits in the embryonic liver erythroid precursors had the same structure as the injected Imferon.

Animals↗

PubMed1975

Corticosteroid effect on eosinophils in vitro: ultrastructural studies.

The effect of corticosteroids, ultracortene and ACTH, on the eosinophilic cells of a patient with hypereosinophilic syndrome has been studied in vitro. Both drugs caused a marked decrease in the number of specific granules, a disappearance of their surrounding membrane and an almost complete destruction of their crystals. In addition, vacuolization of the cytoplasm, swelling of the mitochondria and distortion of their cristae were found. Incubation of the eosinophils with the antihistaminic drug mepyramine, did not produce ultrastructural alterations.

Adrenal Cortex Hormones↗

PubMed1974