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KMID : 0378019700130100051
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New Medical Journal
1970 Volume.13 No. 10 p.51 ~ p.62
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An Electron Microscope Autoradiographic Study on the Effects of Chloramphenicol on Nucleic Acid Synthesis
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Abstract
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The mechanism of bone marrow depression from the chloramphenicol administration remains unknown. Yunis and Harrington (1960) reported that in the experiment on patterns of inhibition by chloramphenicol of nucleic acid synthesis only at high concentrations of the drug was there a distinct inhibition effect on the uptake of labeled precursors into desoxyribose nucleic acid and ribose nucleic acid of normal bone marrow and leukemic leukocytes by means of biochemical analysis.
The present study was undertaken to compare the H3-thymidine incorporation of bone marrow of bone marrow of rabbits by means of light and electron microscopic observations using autoradiography and to contribute to understand the depression mechanism caused by chloramphenicol.
Chloramphenicol (250 mg/kg/day) was injected intramuscularly to the young. rabbits for fourrn days. Day after the last injection of the drug, H3-thymidine (1 pC/Gm. of body weight) was intradritoneally injected to the animals and one hour later the rabbits were killed and bone marrow was removed from the femur bead. Preparation of the light microscopic autoradiographs by dipping sections in fluid emulsion (Nuclear track emulsion, NTB-3) was carried out according to the techniques described by Messier and Leblond (1957) with minor modification. The electron microscope autoradiographic specimens were prepared by means of the technique using glass slides by Salpeter and Bachmann (1964).
In the light and electron microscopic observations, chloramphenicol was found to affect hemopoietic tissues and there were remarkable cytoplasmic changes of the marrow cells in the rabbit as cytoplasic vacuolaization, changes of nuclei. In the light microscopic autoradiographs, the percentage of H3-labeled cells in the erythroid and myeloid groups was not altered from control values while there was an increase in the mean grain count per labeled cell of the erythroid cells. This indicates that active erythroid cells may be in need of larger pool size of H3-thymidine for reserve accumulation than those of the myeloid cells. Quantitatively it seems that a number of the silver grains are associated with nuclei of the erythroid and myeloid cells, and also associated with ergastoplasm including the surrounding cytoplasmic matrix. The intra-granular labeling of both the neutrophilic myelocyte and the eosinophilic myelocyte was also observed.
The technical difficulties on the electron microscope autoradiography was discussed as well in view point of initial coupling autoradiography with electron microscopy.
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