Karyotypes of three black rats from Chichijima, one of the Ogasawara islands of Japan, are described. One of them has 42 chromosomes, while the remaining two possess 41 chromosomes including one large metacentric chromosome resulted from the Robertsonian fusion of each one member of the pair nos. 11 and 12.
Sister chromatic exchange (SCE) frequency is lower in Down syndrome (DS) than in MR, though statistically not significant. The SCE frequency in the G(Y) chromosome group is statistically higher in DS than in MR. There is no regional specificity of chromatid exchange points in chromosome arms. Mitotic index is slightly higher in DS than in MR. Cultured peripheral blood lymphocytes (T-cells) in DS may be hyperresponsive.
A new combined system composed of XPS, SEM and microAES was realized for non-destructive surface characterization. A position sensitive detector system was utilized and a marked improvement of measurement efficiency was obtained. This combined system proved to be very useful for surface chemical state analysis, quantitative analysis and trace analysis.
Five serotype strains of leptospira were observed by both scanning eletcron microscope and transmission electron microscope under the conditions mentioned in the author's previous paper. The spiral direction of all the cells was right-handed, without any exception. This observation is a new established feature in leptospiral cytology and may provide value to the taxonomy as well as the locomotive physiology of bacteria.