Tosihide H. Yosida

Autosomal polymorphism in laboratory bred and wild Norway rats, Rattus norvegicus, found in Misima

SummaryPolymorphism in chromosome pair no. 3 of Rattus norvegicus was found in laboratory strains and wild rats. Some of the animals had a subtelocentric pair no. 3, while others had a telocentric pair no. 3. 14 inbred strains were classified into two types concerning the pair no. 3.1.YOS-type (characterized by a subtelocentric pair no. 3): ACI-, Albany-, Buffalo-, CW-, Fisher-, Long-Evans-, NIG-IV-, Wayne pink-eyed hooded-, WKA- and YOS-strains belong to this type.2.WIS-type (characterized by a telocentric pair no. 3): Donryu-, NIG-III-, W/T- and WIS-strains are included in this type. F1 hybrids between YOS- and WIS-strain rats had a heteromorphic pair no. 3 consisting of a telocentric and a subtelocentric chromosomes.Polymorphism in pair no. 3 was also found in 43 wild rats collected in Misima. They were classified into three types concerning pair no. 3. Among 43 rats, 17 were WIS-type, 3 were YOS-type and the remaining 23 were of hybrid-type.

Banding patterns of Chinese hamster chromosomes revealed by new techniques

Two kinds of techniques were newly developed to reveal banding patterns of the Chinese hamster chromosomes. Both techniques were essentially the same as those used for the extraction of proteins, and one of them could induce bands in chromosome arms in only a few seconds. Banding patterns produced by these techniques appeared to be identical to those induced by the methods reported by previous workers, requiring post-fixation incubation of slides in a warm saline. —The banding pattern was typical for each chromosome pair, permitting unequivocal identification of several pairs which were hardly distinguished by the conventional staining procedures. It was confirmed that these patterns had been well preserved in the chromosomes of a cultured cell line.

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 Philippine 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 chromosome 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 were 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.

Karyological Study of Four Japanese Myotis Bats (Chiroptera, Mammalia)

Karyological investigations of four Japanese Myotis species were made based on Gand C-banding pattern analysis. It was revealed that the four species, M. nattereri, M. hosonoi, M. frater kaguyae and M. macrodactylus have all 2n=44 and their karyotypes are, excepting one chromosome pair, identical each other. The only difference in their karyotypes was found on the morphology of the chromosome no. 5. A minute acrocentric (A) was observed in M. nattereri, and a polymorphic (A) and an (Mh) which is a minute metacentric with totally heterochromatic arm was found in M. hosonoi. In M. f. kaguyae, pair no. 5 was a small submetacentric with a totally heterochromatic long arm (SMh). Polymorphic (SMh) and (M) which is a small metacentric derived from (SMh) by a pericentric inversion was seen in M. macrodactylus. Such morphological differentiations of no. 5 were interpreted by assuming an increase of constitutive heterochromatin and also an inversion. The evolutionary pathway in the genus Myotis is assumed to be as follows: (A)→(Mh)→(SMh)→(M). This assumption was supported by the geographical evidence that the species with the (A) type no. 5 pair is widely distributed in the whole world but the others are restricted to Asia (Mh type) or only to Japan (SMh and M types).

CHROMOSOMAL POLYMORPHISM IN RATTUS RATTUS (L.) COLLECTED IN KUSUDOMARI AND MISIMA.

SummaryChromosomes of Rattus rattus (L.), collected in Kusudomari (Nagasaki) and Misima (Sizuoka) were examined. The karyotype revealed a remarkable heteromorphism in chromosome no. 1. The homozygotic, i.e. standard type, was characterized by 13 pairs of telocentric and 7 pairs of metacentric chromosomes. Chromosome pair no. 1 was telocentric. X and Y chromosomes were also telocentrics. 18.4 per cent of rats from Kusudomari and 40 per cent from Misima showed heteromorphic pair in chromosome no. 1. One chromosome of the heteromorphic pair is conspicuous by the subtelocentric centromere. Total length of the telocentric chromosome of no. 1 is almost the same as of its subtelocentric partner. These facts indicate that the subtelocentric no. 1 chromosome might have arisen by a centromeric inversion of the telocentric chromosome. Individuals homozygous for the subtelocentric no. 1 chromosome could not be found in either population. The difference in the frequency of the dimorphics collected in Kusudomari and Misima was statistically significant. Possible causes of the difference are discussed.

Banding pattern analysis of polymorphic karyotypes in the black rat by a new differential staining technique

Polymorphic karyotypes of black rats (Rattus rattus) collected in Japan, Australia and India were analysed by a new differential staining technique by which banding patterns in the metaphase chromosomes are revealed. The technique consists in two steps: immersion of slides in a mixture of 2 x SSC and 0.1% (w/v) SDS (sodium dodecyl sulfate) for a few seconds at room temperature, and staining in Giemsa. By this treatment characteristic banding patterns were obtained in each chromosome pair. From the banding pattern analysis, subtelocentric pairs No. 1 and 9, which are polymorphic in respect to the acrocentrics and the subtelocentrics, were proven to have originated by pericentric inversion in the acrocentrics. The origin of two large metacentrics observed in Australian and Indian black rats was confirmed to have been developed by Robertsonian fusion of the acrocentrics No. 4 and 7 and No. 11 and 12 present in the Asian type black rat.

Evolution of karyotypes and differentiation in 13 Rattus Species

Karyotypes of 13 Rattus species collected in Asia and Oceania were analysed with special interest to karyotype evolution and species differentiation. They were classified into three groups according to their karyotype similarity. Four species (R. annandalei, R. exulans, R. muelleri and R. norvegicus) with 2n=42 and a karyotype similar to some of the polymorphic karyotypes in the Asian black rats (R. rattus) are classified into the first group. Pericentric inversion of some acrocentrics seemed to have caused the differentiation of these species. The other four species (R. bowersii, R. fuscipes, R. leucopus and R. conatus) with similar karyotypes as the above group, but lower chromosome numbers than 2n=42 are classified into the second group. Robertsonian fusion in some acrocentrics observed in the first group are suggested to have caused the development of the species in this group. The remaining four species (R. sabanus, R. canus, R. huang and R. niviventer) with karyotypes markedly different from the above two in having a fewer number of small metacentrics are classified into the third group. They seemed to be more primitive karyotypes than the other Rattus species. By the comparison between the polymorphic karyotypes in the black rat, and karyotypes in its related species it was suggested that the former had occurred as primary events to the differentiation of the latter. Parallelism between the karyotype evolution and the species differentiation was discussed.

Similarity of giemsa banding patterns of chromosomes in several species of the Genus Rattus

Giemsa banding patterns of chromosomes in seven Rattus species were compared. Four species (R. rattus tanezumi, R. norvegicus, R. exulans and R. muelleri) had all 2n=42 and their karyotypes and banding patterns were similar, although slight differences were observed. Another subspecies (R. rattus rattus) and two other species (R. fuscipes and R. conatus) had fewer chromosomes than the above species by having large biarmed chromosomes developed probably by Robertsonian fusion. The origin of the arms of biarmed chromosomes was recognized by their characteristic banding patterns. The remaining species, R. sabanus, had a karyotype markedly different from the other species by having two small metacentrics although in the others their number was 7. Banding patterns of the chromosomes in this species, however, were also very similar to those of the other, and therefore the 7 small metacentrics seemed to have originated by pericentric inversion of small acrocentrics.

Analysis of single and twin sister chromatid exchanges in endoreduplicated normal and bloom syndrome B-lymphoid cells

Single and twin sister chromatid exchanges (SCEs) were analysed in the colcemid-induced endoreduplicated normal and Bloom syndrome (BS) B-lymphoid cells with diplochromosomes. In normal cells, an equal number of SCEs occur in each of the two cell cycles; the ratio of single (= 5.51 SCEs/cell) to twins (= 2.64 SCEs/cell) was 2∶1 on the endoreduplicated-cell basis, and it was 1∶1 on the diploid-cell basis. In contrast, in 29 endomitoses from one BS B-lymphoid line, a manyfold increase of single SCEs was detected and 139.4 single SCEs on the average were counted, whereas twin SCEs were rare and only 4.9 twin SCEs were countable. In BS cells, the ratio of single (= 139.4 SCEs/cell) to twins (4.9 SCEs/cell) was 28∶1 on the endoreduplicated-cell basis, and it was 14∶1 on the diploid cell-basis; the rates of S1 and S2 exchanges were 4.9 and 69.7 SCEs/cell, respectively. The present study strongly indicates that most of BS SCEs occur during the second cell cycle when BrdU-containing DNA is used as template for replication and that BrdU enhances BS SCEs.

Karyotypic differences of black rats, Rattus rattus, collected in various localities of East and Southeast Asia and Oceania

Karyotypes of several subspecies of black rats, Rattus rattus, collected in different localities of Asia and Oceania were examined with special emphasis on the relationship between the chromosome polymorphism and differentiation of the subspecies. Subspecies of black rats (R. rattus) collected were as follows; tanezumi from Japan; flavipectus and sladeni from Hong Kong; diardii, jalorensis from Kuala Lumpur, Malaysia; argentiventer from Kuala Lumpur, and Java and Celebes, Indonesia; mindanensis from Luzon and Mindanao, Philippines; and rattus from Australia, New Zealand, and New Guinea. Subspecies in Formosa, Korea and Thailand were not determined. All black rats collected in the above Asian districts had 42 diploid chromosomes, while those in Oceania had 38. The rats collected in Japan (tanezumi), Korea, Formosa, Thailand and Malaysia (diardii) had A/A No. 1 pair or polymorphic No. 1 (A/A, A/S and S/S) pairs, while those collected in Java and Celebes (argentiventer), Luzon and Mindanao (mindanensis) showed a higher frequency of S/S No. 1 pair. From the higher occurrence of No. 1 A/A pair of black rats in the Asian continent where the black rats originated, it is suggested that the original type of No. 1 chromosome pair of the black rats is A/A, and a pericentric inversion occurred in the acrocentric No. 1 chromosome and thus rats with subtelocentric No. 1 pair formed.—Black rats with 38 chromosomes were observed in Australia, New Guinea and New Zealand. These karyotypes seem to have developed by Robertsonian fusion of 4 acrocentric pairs (No. 4 and 7, and No. 11 and 12) in black rats of the Asian type. A relationship between body size and chromosome constitution was observed in subspecies of the black rats.