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Biomedical subjects

Y Tagashira

Publications and source records attributed to Y Tagashira.

At least 55 records · Page 3Linked to original sources
PubMed1982

Mitochondrial DNA analysis of mouse-rat hybrid cells: effect of chloramphenicol selection on the relative amounts of parental mitochondrial DNAs.

Several mouse-rat somatic hybrid cell lines were isolated by fusing chloramphenicol-resistant (CAPr) and CAP-sensitive (CAPs) parent cells, and propagation of the parent mitochondrial DNA (mtDNA) species in the hybrid cells was studied. The restriction endonucleases EcoRI, HpaII, and HaeIII were used for identification of mtDNA species. Both mouse and rat mtDNAs were propagated in all the hybrid cells examined and maintained during long-term cultivation and repeated cell division. Moreover, in CAPr mouse-rat hybrid cells, selection and successive cultivation in the presence of CAP did not increase the relative amount of mtDNA species of CAPr parent cell origin, and when CAP was removed from the culture medium, mtDNA species of CAPr parent cell origin did not decrease appreciably. The amount of mouse mtDNAs was consistently 1-4 times that of rat mtDNAs inthe mouse-rat hybrid cells regardless of the species of parent cells from which the CAP resistance was derived. Thus mouse-rat hybrid cells have a stable mtDNA population in which the amount of mouse mtDNAs is larger than that of rat mtDNAs without any influence of CAP selection.

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PubMed1982

Origins of laboratory mice deduced from restriction patterns of mitochondrial DNA.

To determine the origins of laboratory mice, the restriction patterns of mitochondrial DNAs (mtDNAs) from various strains were compared with those of relevant subspecies and/or races of Mus musculus. In most strains and substrains of laboratory mice examined (50/55), the cleavage patterns were identical to those of the European subspecies M. m. domesticus. Those that varied include two sublines of NZB, the strain NZC, and the Japanese strain RR. The NZB and NZC patterns were identical to that of the European subspecies M. m. brevirostris, which itself has restriction patterns similar to M. m. domesticus. On the other hand, the RR pattern was identical to M. m. molossinus-like mice trapped in Western China and slightly different from Japanese M. m. molossinus. These findings suggest that the strains NZB and NZC stemmed from a European founder stock which differed from the ancestral stocks of other laboratory strains and that the ancestral mice of the RR strain had been transported from China to Japan. Therefore, most laboratory strains of mice are derived from the European subspecies M. m. domesticus while M. m. brevirostris and M. m. molossinus have made minor contributions. M. m. musculus does not appear to have made any contribution.

Animals↗
PubMed1982

Specific suppression of the local GVH reaction by F1 spleen cells.

The local graft-versus-host (GvH) reaction in (C57BL/6 X BALB/c) F1 hybrid mice, assayed by popliteal lymph node enlargement, was specifically depressed by an injection of parental lymphocytes mixed with spleen cells from F1 mice pretreated with the same parental lymphocytes. Suppressor activity of CBF1 spleen cells was obtained 7 days after inoculation of parental lymphocytes, and peaked on day 10. The suppressive activity was induced by only spleen cells from CBF1 which was inoculated Balb/c lymphocytes, but not C57BL/6 lymphocytes. The lymphocyte subpopulation responsible for the suppressive activity was noticed in T cell population.

Animals↗
PubMed1981

Polymorphisms of mitochondrial DNAs in Norway rats (Rattus norvegicus): cleavage site variations and length polymorphism of restriction fragments.

Extensive polymorphism was found in mitochondrial DNAs (mtDNAs) of Norway rats (Rattus norvegicus). The restriction endonuclease cleavage patterns of mtDNAs of laboratory rats, wild rats, tumor cells, and culture cells were compared. The polymorphism is defined by two criteria; one is cleavage site variation and the other is length polymorphism of restriction fragments. The cleavage site variation may be caused by point mutation, and the length polymorphism by sequence deletions or insertions. At least five types, types A-E, were identified by cleavage site variations, and two groups, a and b, were identified by length polymorphism of one HpaII fragment, Hpa5. All types except type C belonged to either group-a or group-b, whereas both groups were found in type C. Differentiation of polymorphic Norway rat mtDNA types and the experimental use of the polymorphism are discussed.

Animals↗
PubMed1981

Evolutionary relationships among five subspecies of Mus musculus based on restriction enzyme cleavage patterns of mitochondrial DNA.

The intra- and intersubspecific genetic distances between five subspecies of Mus musculus were estimated from restriction enzyme cleavage patterns of maps of mitochondrial DNA (mtDNA). The European subspecies, M. m. domesticus and Asian subspecies, M. m. bactrianus, M. m. castaneus, M. m. molossinus and M. m. urbanus were examined. For each subspecies, except M. m. urbanus, at least two local races from widely separated localities were examined. Intrasubspecific heterogeneity was found in the mtDNA cleavage patterns of M. m. bactrianus and M. m. castaneus. M. m. molossinus and M. m. domesticus, however, revealed no intrasubspecific heterogeneity. Four of the subspecies had distinct cleavage patterns. The fifth, M. m. urbanus, had cleavage patterns identical to those of M. m. castaneus with several enzymes. Estimates of genetic distances between the various races and subspecies were obtained by comparing cleavage maps of the mtDNAs with various restriction enzymes. Nucleotide sequence divergences of mtDNA between local races were estimated to be less than 0.4% in M. m. bactrianus and less than 0.3% in M. m. castaneus. The times of divergence of both subspecies were calculated to be 0.1--0.2 x 10(6) years. These values suggest that the intrasubspecific divergence began some 0.1--0.2 x 10(6) years ago. On the other hand, nucleotide sequence divergences between European subspecies M. m. domesticus and Asian subspecies M. m. bactrianus and M. m. castaneus were 7.1% ane 5.8%, respectively. The times of divergence were calculated to be 2.1--2.6 x 10(6) years. Further, the nucleotide sequence divergence and time of divergence between M. m. molossinus and the other two Asian subspecies were comparable to those between M. m. molossinus and M. m. domesticus (about 3% and 1 x 10(6) years, respectively). These results suggest that M. m. molossinus is situated in a unique evolutionary position among Asian subspecies.

Animals↗
PubMed1979

Evolutionary aspects of variant types of rat mitochondrial DNA'S.

Mitochondrial DNA's (mtDNAs) were prepared from various kinds of individual Norway rats, Rattus norvegicus, and from three types of individual black rats, Rattus rattus, (Asian type, Ceylon type, and Oceanian type). Intra- and interspecies divergence of their mtDNA sequences were calculated based on changes in restriction endonuclease cleavage sites. The extent of intraspecies divergence of black rats (about 8%) is much larger than that of Norway rats (1%) and the mtDNA of Asian-type black rats resembles the mtDNA of Norway rats more closely than it resembles the mtDNA of other types of black rats. These results strongly suggest that during the course of intraspecies differentiation of black rats, probably long after the separation of the three types of black rats, some Asian-type black rats were isolated sexually and formed a new species, Norway rats. On the basis of our observations we propose a hypothetical process to explain the evolution of animal mtDNA.

Animals↗
PubMed1979

An improved method for estimating sequence divergence between related DNAs from changes in restriction endonuclease cleavage sites.

We have developed a theory to estimate the degree of sequence divergence between related DNAs from the comparison of restriction endonuclease recognition sites. Two major improvements have been made upon a similar method reported by Upholt (1977). First, the most probable value is calculated by the collective use of all available data. This reduces intrinsic statistical error and extends the analyzable range of sequence divergence. Second, all variables are redefined so that they have strict mathematical implications. This corrects a serious error arising from the misinterpretation of the meaning of the fraction of conserved cleavage sites. With this refined method, sequence divergence between rat and mouse mitochondrial DNAs (mtDNAs) was calculated to be about 25% substitutions/nucleotide, which is in good agreement with the DNA-DNA hybridization data obtained by Jakovcic et al. (1975). It was also estimated that the three types of rat mtDNAs differ from one another by 0.3 approximately 1% of total base pairs. These values are 2 approximately 5 times smaller than those obtained with the conventional method.

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