In six subspecies of Carassius auratus and Gold-fish including Carassius a. subsp., C. a. buergeri, C. a. grandoeulis, C. a. cuvieri, C. a. langsdorfii, the Chinese Funa (C. a, auratus) and the Wakin (C. a. auratus), the NORs patterns of chromosomes were comparatively investigated. The areas of intense silver deposition (Ag-NORs) were constantly and commonly associated with the short arms of the 12th largest submetacentric chromosomes in the varieties except C. a. langsdorfii. In C. a. langsdorfii there were two such elements among the median-sized submetacentric chromosomes. No remarkable sexual differences of the NORs was detected.
The segregation ratio in F2 hybrids from Mauritius type black rats (2n, 42)×Oceanian type rats (2n, 38) and their litter size were studied. The average litter size of the F2 offspring was 4.3±1.7. The segregation ratio of chromosome pair nos. 14 and 18 in the F2 hybrids was nearly identical with the expected one. It was concluded that the Mauritius type black rats are very closely related to the Oceanian type rats on the bases of litter size and segregation ratio in the F2 hybrids.
Human leukocytes were treated with CPM for the establishment of the in vitro activating system to detect inactive mutagenic chemicals in the presence of S-9 mix. CPM caused a maximum increase in SCE-frequency after 60min incubation. Further, the frequency of SCEs was markedly increased by additional doses of CPM. It thus appears that chemicals requiring metabolicactivation induce SCEs in the human leukocyte test system.
The total and partial amino acid sequences of Tetrahymena histones H4 and H2B, respectively, have been determined. Comparisons of these sequences with those of mammals and pea suggest that the divergence of protozoa and higher eukaryotes is more ancient than the divergence of animals and plants.