Search PubMed⌕ Search

Biomedical subjects

T Sagai

Publications and source records attributed to T Sagai.

31 records · Page 2Linked to original sources
PubMed1987

Sexual preference of meiotic recombination within the H-2 complex.

The recombination frequency between the H-2K and H-2D marker loci in male mice was measured using heterozygotes that carry the H-2wm7 haplotype derived from the Japanese wild mouse and common H-2 haplotypes derived from inbred mice. Previous mating experiments in which backcross progeny of heterozygous females were screened demonstrated that the H-2wm7 displays marked enhancement of recombination within the H-2 complex. In contrast to recombination in female mice, no enhancement of recombination was observed during male meiosis in the present study. Thus, it appeared that enhancement of recombination is specific to female mice. A genealogical study of recombination indicated that the postmeiotic stage is not involved in the generation of sexual preference of enhancement of recombination, suggesting that the preference is meiotic-drive and that a female-specific mechanism is involved in meiotic recombination mediated by the H-2wm7 haplotype.

Animals↗
PubMed1987

Lethal deletion of the complement component C4 and steroid 21-hydroxylase genes in the mouse H-2 class III region, caused by meiotic recombination.

A recombinant H-2 haplotype, designated aw18, was produced that underwent meiotic recombination in the E alpha (I-E alpha chain)--Slp (sex-limited protein) interval of the H-2 class III region between B10.A (H-2a) and wild-derived B10.MOL-SGR (H-2wm7) strains. It appeared that the H-2aw18 haplotype has a single, recessive, lethal mutation, since homozygotes for H-2aw18 were not detected in progeny generated from the intercross of mice that were heterozygous for this H-2 haplotype. Nine newly established recombinant H-2 haplotypes, which arose from the heterozygous mice that resulted from a cross between common inbred H-2 haplotypes and the aw18 haplotype, allowed us to map the lethal gene to the class III region of the H-2 complex. Southern blot analysis indicated that the aw18 haplotype has a deletion of the C4 gene and a deletion of one of the steroid 21-hydroxylase genes. This result was confirmed by an immunodiffusion test that demonstrated the absence of production of the C4 protein in mice of haplotype H-2aw18. All data that were obtained supported the hypothesis that the meiotic, presumably unequal, recombination between homologous chromosomes of the H-2a and H-2wm7 haplotypes caused the deletion of the C4 and the 21-hydroxylase genes.

Animals↗
PubMed1986

Characterization of newly isolated monoclonal antibodies against MHC of a Japanese wild mouse.

We have already developed nine B10.MOL congenic strains carrying H-2 haplotypes derived from Japanese wild mice, Mus musculus molossinus, with the C57BL/10 genetic background. To obtain monoclonal antibodies against the H-2 antigen of the Japanese wild mouse, we carried out cell fusion using spleen cells from the animal immunized with one of the B10.MOL strains, B10.MOL-SGR (H-2wm7). As a result, 19 hybridomas producing monoclonal antibodies were produced. Analysis with the intra-H-2 recombinants derived from B10.MOL-SGR indicated that 8 of them reacted with the class I and 11 with the class II molecule. The class I antibodies were tested for their cross-reactivities on wild mice and on the panels of standard inbred and B10.MOL strains. Most of the antibodies reacted with both the Japanese wild mice and the other subspecies, including standard inbred, while two antibodies highly specific for the donor H-2K region reacted with only three wild-derived mice, two M. m. molossinus from Anjo and Shizuoka, Japan, and one M. m. domesticus from Pigeon, Canada. In addition, all of the other four antibodies reactive with the K antigen of B10.MOL-SGR also reacted with the same three wild mice. The wild mice belonging to different subspecies might share very similar H-2K antigenic determinants in spite of their genetic and geographical remoteness.

Animals↗
PubMed1986

Maternal contamination of some NZB sublines and genetic profiles of NZ-strains.

Six sublines of NZB mice bred in Japan were collected and their mitochondrial DNA (mtDNA) was examined by restriction analysis. The phenotypes of at least three of these sublines (NZB/Nrs, NZB/Nga and NZB/KlJms) differed from a standard one (NZB/BlWehi). Since mtDNA is inherited maternally, all sublines of a single inbred strain should share the same mtDNA phenotype. Therefore, b-type of mtDNA should be observed in all NZB sublines. Nevertheless, the above-mentioned sublines showed d-type mtDNA. These results suggested a genetic contamination of these sublines. This was confirmed by the finding that six aberrant alleles were detected also in their nuclear genomes using biochemical markers. For elucidation of the cause of contamination, we characterized the genetic profiles of four standard NZ-strains, NZB/BlWehi NZO/BlWehi, NZC/BlWehi and NZX/BlWehi, and of common inbred strains with black coat color, C57BL/6J, C57BL/10Sn, C57BL/Ks, C58/J and AU/SsJ. We found that five of the six aberrant alleles most strongly corresponded with those of C57BL/Ks. These results suggest that this contamination was ascribable to cross of NZB mice with a certain C56BL strain. We also deduced that NAB/BlPt and NZB/Füll also probably were contaminated strains, suggesting that this contamination was not restricted to Japan.

Alleles↗
PubMed1981

A simplified micro-method for cytotoxicity testing using a flat-type titration plate for the detection of H-2 antigens.

A new micro-method for cytotoxicity testing using a flat-type titration plate has been developed. This micro-method is so simple that it involves no washing and staining procedures. In this method, cell viability is judged on the basis of the refractility change in the lymphocytes seen under the phase-contrast microscope. This micro-method has higher sensitivity and reproducibility than the dye exclusion method and 51Cr-release assay. Fixation of cells with glutaraldehyde and tight covering of the plate allow us to read the result even after 3 weeks. These advantage of the new method enable us to deal with a large number of samples at one time. We also introduce a rapid technique for the preparation of a cell suspension from the lymph node without killing the animal.

Animals↗
PubMed1975

Variation of C-bands in the chromosomes of several subspecies of Rattus rattus.

All subspecies of black rats (Rattus rattus) used in the present study are characterized by having large and clear C-bands at the centromeric region. The appearance of the bands, however, is different in the subspecies. Chromosome pair No. 1 in Asian type black rats (2n=42), which are characterized by an acrocentric and subtelocentric polymorphism, showed C-band polymorphism. In Phillipine rats (R. rattus mindanensis) the pair was subtelocentric with C-bands, but in Malayan black rats (R. rattus diardii) it was usually acrocentric with C-bands. In Hong-Kong (R. rattus flavipectus) and Japanese black rats (R. rattus tanezumi) it was polymorphic with respect to the presence of acrocentrics with C-bands or subtelocentrics without C-bands. The other chromosomes pairs showed clear C-bands, but in Hong-Kong black rats the pairs No. 2 and 5 were polymorphic with and without C-bands. In Japanese black rats, 6 chromosome pairs (No. 3, 4, 7, 9, 11 and 13) were polymorphic in regard to presence and absence of C-bands, but the other 5 chromosome pairs (No. 2, 5, 6, 8 and 10) showed always absence of C-bands. Only pair No. 12 usually showed C-bands. C-bands in small metacentric pairs (No. 14 to 20) in Asian type black rats generally large in size, but those in the Oceanian (2n=38) and Ceylon type black rats (2n=40) were small. In the hybrids between Asian and Oceanian type rats, heteromorphic C-bands, one large and the other small, were observed. Based on the consideration of karyotype evolution in the black rats, the C-band is suggested to have a tendency toward the diminution as far as the related species are concerned.

Animals↗