The triploid and tetraploid specimens of the Japanese common lach, Misgurnus anguillicaudatus, were detected among 13 individuals obtained from the Chinai river of Shiga prefecture and 67 specimens from the market. One polymorphism due to the Robertsonian fusion was found in a population of diploid specimens. The DNA values in individual nuclei of liven cells from diploidy, triploidy and tetraploidy were estimated through the Feulgen cytophotometry (Olympus DMSP-1). The DNA value of tetraploidy was about twice that of diploidy, and that of triploidy was intermediate between diploidy and tetraploidy.
The G-, Q- and C-banded structures of chromosomes were described in the field mouse (Apodemus argenteus Temmink). Out of the four specimens (2_??_, 2_??_) studied, three had 46 chromosomes, whereas one female individual showed 45 chromosomes in which an XO sex-constitution was detected.
Karyotype of the Australian wild rat, Rattus villosissimus, with 50 chromosomes were examined with conventional and G-banding techniques. Among 24 autosome pairs two were large metacentrics due to the Robertsonian fusion of pair nos. 2 and 3 and of pair nos. 6 and 10. Twelve extra small acrocentric pairs were confirmed to result from the Robertsonian fission of small metacentric pairs 14 to 19 occurring in the basic karyotype of Rattus.
Rat liver parenchymal and non-parenchymal cells were isolated by the collagenase perfusion method followed by Percoll density gradient centrifugation. The isolated parenchymal cells, when cultured for a few days, formed cords of polygonal cells which are typical for hepatocytes and produced a low (about 0.2% of total protein synthesized) but significant amount of collagen. This is the first demonstration of collagen production by hepatic parenchyma) cells in primary culture.