Triploid hybrids between Rhodeus ocellatus ocellatus (female) and Acheilognathus limbatus (male) were artificially induced by cold shock treatment of eggs for 1h, 5min after the insemination. All of the treated eggs examined so far were triploidy. The chromosome number of the triploids was 72, and their karyotype consisted of a diploid set of the maternal species and a haploid set of the paternal species. When silver staining was applied, only NORs from the maternal species (R. o. ocellatus) were stained deeply; no NOR from the paternal species was detected. The aseptic breeding and the cell culture method with larvae newly induced in this study were very useful for facilitating breeding and chromosome studies.
The chromosomal distribution of the NORs in three species with 2n=48 (Acheilognathus lanceolatus, A. limbatus, and Rhodeus ocellatus ocellatus) and three species with 2n=44 (A. cyanostigma, A. tabira tabira, and A. rhombeus) in Rhodeinae, was investigated using the silver staining technique. In the species with the same chromosome number, the NORs are located in different chromosomes despite of the karyotypic similarity. These results suggest that the alternation of the locations of NORs have played an important role to the species differentiation in this subfamily.
Four kinds of cell lines (OST1, OST1-M, OST2, OST3) were established from human osteosarcoma through the transplantation into nude mice of biopsied tumors. OST1 and OST1-M cells were respectively derived from primary and metastatic lesions of a patient. The original cells for OST1 were sampled before the therapy, while those for OST1-M were extracted after the chemotherapy and radiotherapy. Q-banding analysis showed that the chromosomal composition was different between the two cell lines. Also, the marker chromosomes in OST1-M cells contained a number of abnormally stretched one which probably resulted from gene amplification.