Hitoshi Okumoto

Evidence for heteromorphic sex chromosomes in males of Rana tagoi and Rana sakuraii in Nishitama district of Tokyo (Anura: Ranidae).

Karyotypes of the Tago brown frog Rana tagoi and stream Tago brown frog Rana sakuraii from a mountain region in the Nishitama district in Tokyo were examined by conventional Giemsa staining, C-banding and late replication (LR)-banding. Chromosome number was 2n = 26 in all cases. The 26 chromosomes consisted of five (1–5) pairs of large chromosomes and eight (6–13) pairs of small chromosomes. Chromosome 10 had a secondary constriction on the long arm. In all frogs, on chromosome pair 8, the XX/XY type sex chromosome was present. C-banding analysis indicated that, in R. sakuraii, neither the X nor Y chromosome possessed interstitial C-bands but each had centromere staining, while in R. tagoi, an interstitial C-band was present on the long arm of the X chromosome. The Y chromosome had no interstitial C-band. LR-banding analysis demonstrated the X and Y chromosomes to have a LR-band on the short arm and two LR-bands, each on the long arm, and the bands on both species to be essentially the same. Heteromorphic sex chromosomes in males of R. sakuraii and R. tagoi were identified for the first time in this study.

Establishment of Three Cell Lines Derived from Frog Melanophores

Abstract Three cell lines have been established from melanotic and amelanotic melanophores of wild and albino Rana nigromaculata and albino Rana porosa brevipoda after experiencing three culture crises. The population doubling rate increased with culture time. Cells from both wild and albino R. nigromaculata changed shape twice in ten years. They began as large pigmented or non-pigmented epithelial-like cells at the beginning of the cultures. The melanophores of albino R. nigromaculata unexpectedly became pigmented shortly after the beginning of the culture. Over time, they transiently aquired a small, non-pigmented, bipolar morphology and finally became large non-pigmented epithelial-like cells after about 8 to 10 years. On the contrary, cells from albino R. porosa brevipoda remained large, non-pigmented, epithelial-like cells over the entire course of the culture. Pigmented cells contained many mature melanosomes, while non-pigmented epithelial like cells contained premelanosomes with characteristic internal structures. Non-pigmented, fibro-blast-like cells contained numerous small vesicles in place of typical premelanosomes. The cells of established cell lines, including those from wild R. nigromaculata, were unpigmented and showed no tyrosinase activity in histochemical dopa reactions. The number of chromosomes deviated from the normal pattern in the three cell lines. Each of the three cell lines had a different modal number than the other two, and the chromosomal compositions of the cells within the same lines differed from one another. Even within the same cell lines, the mode changed as the culture progressed without any consistent trends.