The minor RNA components in large ribosomal subunits of rat liver were analyzed by gel electrophoresis. Quantitative analysis showed that these minor components, whose apparent molecular weights ranged from 8.48×105 to 11.4×105, represented 10 to 13% of the total high-molecular-weight ribosomal RNA. It was elucidated that they were not artifacts arose during the cell homogenization, subcellular fractionation, RNA preparation and gel electrophoresis. Labeling experiment in vivo showed that they were preferentially present in "old" ribosomes. It was predicted that these minor components were the intermediates in the degradation of 28S ribosomal RNA in vivo. In the regenerating liver, where the degradation of proteins was reported to be blocked, the relative amount of the minor RNA components was decreased to about a half of that of normal liver. There was, however, no increase in their relative amount in the long-term starved rat liver, where RNA degradation should be going very rapidly.
Journal Article Cell Lysis and Superoxide Dismutase Activities of Highly Radioresistant Bacteria Get access Taeko Yoshinaka, Taeko Yoshinaka Laboratory of Radiation Genetics, Faculty of Agriculture, The University of Tokyo, Tokyo 113, Japan Search for other works by this author on: Oxford Academic Google Scholar Keiji Yano, Keiji Yano Laboratory of Radiation Genetics, Faculty of Agriculture, The University of Tokyo, Tokyo 113, Japan Search for other works by this author on: Oxford Academic Google Scholar Hikoyuki Yamaguchi Hikoyuki Yamaguchi Laboratory of Radiation Genetics, Faculty of Agriculture, The University of Tokyo, Tokyo 113, Japan Search for other works by this author on: Oxford Academic Google Scholar Agricultural and Biological Chemistry, Volume 40, Issue 1, 1 January 1976, Pages 227–229, https://doi.org/10.1080/00021369.1976.10862025 Published: 01 January 1976 Article history Received: 14 July 1975 Published: 01 January 1976
Mitochondrial DNAs (mtDNAs) were isolated from several rice strains of Chinsurah boro II (fertile), Zhen Shan 97A (male sterile), Zhen Shan 97 (fertile), and Akihikari (normal japonica). Small plasmid-like DNAs, B1 and B2, which were found firstly in BT line, were cloned into plasmid vectors and mapped in terms of some of restriction enzymes. Plasmid-like DNAs were also observed in the mitochondria of Zhen Shan 97A and Zhen Shan 97 by agarose gel electrophoresis. To examine whether these plasmids were identical or not, hybridization analyses were carried out with B1 and B2 as probes. Consequently, it was suggested that two plasmids of Zhen Shan 97A were identical to B1 and B2, and one of the plasmids of Zhen Shan 97 was identical to B2. The smaller plasmid of Zhen Shan 97 had no homology to either B1 or B2. Co-existence of B1 and B2, while common, is not an obligatory feature. Because B2 was found in the fertile cytoplasm of Zhen Shan 97, an involvement of B2 with cytoplasmic male sterility (cms) might be denied.
Barley root meristematic cells were treated with three antibiotics known as the inhibitors of protein synthesis, i.e., chloramphenicol (CAP), cycloheximide (CH) and puromycin (PU), at each stage of the interphase in first cell cycle. The results indicated that both CAP and CH induced the chromosome fragments of dot type after the treatment in early S, late S or early G2 cells, but PU produced no chromosomal aberrations. These chromosome fragments seemed to be produced by a 1-hit event.On the other hand, S cells treated with CAP or CH markedly reduced the number of chromosomes in a cell. The chromosome reduction is likely due to the nondisjunction of chromosomes.Moreover, CH inhibited the protein synthesis as revealed by the incorporation of 3H-lysine, but CAP did not depress at the concentrations used. It was discussed that chromosome fragments are attributable to the chromosome nondisjunction.
In order to clarify the effect of fractional dosage on sterility in the treaited generation, dormant Seeds of a variety "Norin No. 29" of rice and of a variety "Sekitori Sai No. 1" of barley were treated with X-radiation. The irradiation was given in two fractions of 10.000 r. at one, two or four days interval and a single dose of 20.000 r. in both species. The fractional dosage produced more sterility than the single dose in the first generation of rice as well as of barley, as shown at Table I and 3, and the increment of rest period elapsing between first irradiation and the next gave more sterile spikes). This result obtained with dormant seeds probably is due to the Storage of seed after the cessation of X-raying, also to the X-ray-sensitivity produced by the first irradiation.
