岡山大学農学部 Acta Medica Okayama 0474-0254 40 1 1972 The Effect of Cycloheximide on RNA Metabolism in Leaves of the Tobacco Plant 9 18 EN Seiji Ouchi Iwao Furusawa Shigeyasu Akai The effect of cycloheximide on RNA metabolism in tobacco leaf discs was analyzed to signify its inhibitive or stimulative effect on TMV multiplication. RNA content increased in the leaf discs incubated in 1.0 or 3.0 ppm solution. 32P-incorporation into RNA, however, was accelerated at 1.0 ppm and disturbed at 3.0 ppm, suggestirg th~t the increment of RNA in the leaf disc<- treated at 1. O ppm is qualitatively different from that in the discs incubated at 3.0 ppm, i. e., the former is the result of stimulated synthesis while the latter is mainly due to the inhibition of degradation. Column chromatograms with methylated albumin Kiselguhr clearly elucidated that incubation of discs in 3.0 ppm led to the abolition of the integrity of the light ribosomal RNA. The change in chromatographic pattern was discernible 24 hr after the initiation of treatment of leaf discs. Incubation in 1.0 ppm cycloheximide, however, did not give rise to a drastic change in chromatograms, although an undulate incorporation of 32P-orthophosphate into ribosomal RNAs was noticed. 14C-glycine incorporation into RNA suggested that cycloheximide not only enhances RNA synthesis but also stimulates the synthesis of purine bases. Ribonuclease activity of leaf homogenate remarkably decreased by cycloheximide treatment, suggesting that the accumulation of RNA in the discs treated at 3.0 ppm could be acounted for by the retardation in RNA degradation. The inhibitory and stimulative effects of cycloheximide on TMV multiplication were discussed on the basis of these results. No potential conflict of interest relevant to this article was reported.

岡山大学農学部 Acta Medica Okayama 0474-0254 41 1 1973 Ultrastructure of Ribosomes in Cells of The Tobacco Leaves Treated With Cycloheximide 1 10 EN Iwao Furusawa Seiji Ouchi The effect of cycloheximide on cell organelles was investigated at the level of ultrastructure, with an emphasis on the ribosomal behaviors. The antibiotic, at low concentrations, primarily caused an orderly alignment of ribosomes on endoplasmic reticuli (ER), giving rise to rough-surfaced ER. Development of membrane systems was also a characteristic feature of the cells treated at low concentration or incubated for short period of time. Prolonged incubation or treatment at higher concentrations led eventuaily to the degeneration of cytoplasmic and nuclar organizations, the aggregation of ribosomal debris being one of the conspicuous features. On the contrary, no major structural change was observed of the chloroplasts and mitochondria which are both resistant to the inhibitory action of cycloheximide. These results were discussed in relation to the inhibition of protein synthesis by the cycloheximide. No potential conflict of interest relevant to this article was reported.