Search PubMed⌕ Search

Biomedical subjects

T H Yosida

Publications and source records attributed to T H Yosida.

At least 37 records · Page 2Linked to original sources
PubMed1979

Identification of the facultative heterochromatic X chromosome in females of 25 rodent species.

Treatment of the chromosomes of 25 rodent species with a 50 degrees C hypotonic solution and Giemsa staining permitted identification of the heterochromatic X chromosome in 24 species. With this technique, the facultative of the heterochromatic X chromosome or the facultative portion of large, composite-type X chromosoms is stained darker than the other chromosomes, allowing it to be distinguished from the homologous euchromatic X chromosome in female metaphase cells. Intense staining of the single X chromosome was not observed in male metaphase cells. It is suggested that this differential staining of one of the two X chromosomes might be due to qualitative differences in chromosomal proteins rather than to differences in the degree of chromosomal condensation or in DNA base sequence.

Animals↗
PubMed1979

Establishment of cell lines from the wild rodent Millardia meltada and tests for endogenous virus.

Four cell lines were established from the wild rodent, Millardia meltada; an untransformed cell line (MM-D), a non-producer (NP) cell line transformed with murine sarcoma virus (MM-CL4), and SV40-transformed cell lines (MM-8 MM-663). MM-D is epithelioid and contact-inhibited, whereas MM-CL4, MM-8, and MM-663 are fibroblastic and grow piling up. No endogenous virus was induced in Millardia cell lines by a long-term culture with various inducers. Millardia cell DNA has no nucleotide sequence homology with cDNA of either murine leukemia virus or rat endogenous virus.

Animals↗
PubMed1978

Experimental breeding and cytogenetics of the soft-furred rat, Millardia meltada.

The soft-furred rat, Millardia meltada, has bred successfully in the laboratory for 10 generations of brother x sister mating. It is half way in size between the rat and the mouse, and is gentle and easy to handle. Thin body hair and incisor teeth are present in the newborn. Some individuals have low blood pressure. Chromosome number (2n) in 50. It differs in several characteristics from the rat and mouse, and could become a useful experimental animal in biomedical research.

Animals↗
PubMed1977

New inversion of the pair no. 3 chromosome in the black rat.

A Japanese black rat (Rattus rattus tanezumi) with a subtelocentric pair no. 3 chromosome was found in Gotenba, Japan. By comparison of the length in both members of the chromosome pair, and from the G-band pattern, the subtelocentrics seemed to have developed from the original acrocentrics by the pericentric inversion.

Animals↗
PubMed1977

Frequencies of chromosome polymorphism in pairs no. 1, 9, and 13 in three geographical variants of black rats, rattus rattus.

Frequencies of the acrocentric and subtelocentric polymorphism in pairs no. 1, 9 and 13 chromosomes have been examined in 358 black rats. Rattus rattus, distributed over several countries of Asia, Austrailia and United States. The black rats are divided into three geographical types by the different chromosome numbers, such as Asian (2n=42), Ceylon (2n=40) and Oceanian types (2n=38). Pairs no. 13 polymorphism was found widely in these all types, but the pair no. 1 and 9 polymorphisms were found in only Asian type black rats. In the Asian type rats, however, those distributed in northern India and Pakistan showed always the subtelocentric pairs no. 1 and 9 like as those in Ceylon and Oceanien type rats have developed in India or Pakistan from the Asian type. The present study also suggests that inversion of the pair no. 13 could have occurred in earlier period than those of the pairs no. 1 and 9.

Animals↗
PubMed1977

Supernumerary chromosomes in the black rat (Rattus rattus) and their distribution in three geographic variants.

Supernumerary chromosomes have been examined in 352 black rats, covering three geographic variants, by use of conventional and C-band staining techniques. Metacentric supernumerary chromosomes, one to three in number, were found in Malayan black rats (Rattus rattus diardii), with 2n=42, in Indian black rats (R. rattus rufescens), with 2n=38, and in Ceylonese black rats (R. rattus kandianus), with 2n=40. The supernumeraries had similar morphology and stained heavily along their entire length by C-band staining. These findings suggested that the supernumeraries had originally developed in the Asian-type black rats and then were sequentially transmitted to the Ceylonese and Oceanian-type black rats, probably in southwestern Asia. A subtelocentric supernumerary chromosome found in one Japanese black rat seemed to have developed independently from the above metacentric supernumeraries.

Animals↗
PubMed1977

Karyologic studies on hybrids between Asian, Ceylonese, and Oceanian type black rats, with a note on an XO female occuring in the F2 generation.

F1 hybrids between the Asian type (2n=42) and Ceylonese type black rats (2n=40) invariably showed 41 chromosomes, while those between the Oceanian type (2n=38) and the Ceylonese type usually showed 39 chromosomes. Twelve F2 hybrids (three litters) were obtained only from the latter combination. Among them, the karyotypes of nine rats were successfully analyzed. They were segregated into the Oceanian type (three rats) and the F1 type (six rats). No Ceylonese type was obtained. From the results of fertility testing in F1 hybrids between these three variants, the Oceanian type is assumed to be more closely related to the Ceylonese type than the Asian type. This coincided well with the results of karyotypic evolution of these geographic variants. Among the nine F2 hybrids examined, one female consistently showed 37 chromosomes with one X chromosome. This XO female appeared to be a normal female and to have been a sporadic natural occurrence.

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↗