A new substrain of cells, named Ban, was obtained from the human epidermoid carcinoma 2 (HEp-2) cell line. The Ban cells, which are larger than HEp-2 cells were isolated using a cell sorter after seeding HEp-2 cells by the limited dilution method. Not only the cell size but also the size of the nucleus of Ban cells was found to be larger than that of HEp-2 cells, and these characteristics were maintained for more than 7 months (46 passages). The chromosome frequency distribution of Ban cells was about 1.5 times greater than that of HEp-2 cells. When cell number were examined comparing Ban cells (50 passages) and HEp-2 cells, no significant difference in cell growth was observed for up to 7 days. Ban cells are useful for detection of anti-nuclear antibodies since these cells display 5 kinds of nuclear staining patterns as in the case of HEp-2 cells. However, the relative fluorescence intensity of Ban cells was greater than that of HEp-2 cells upon staining with anti-cytoplasmic antibodies.

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The karyotypes of various HeLa cells, one of the most often used human cell lines, were evaluated using strains maintained at different laboratories. Judging from chromosomal number and rearranged chromosomes, they could be classified into three groups. Group I was composed of the originally established HeLa and Groups II and Ill were composed of cells presumably derived from HeLa S3.O⁶-Methylguanine-DNA-methyltransferase activity was positive in cell sublines belonging to Groups I and III, but negative in Group II. These findings show that the HeLa cell sublines have distinct enzymatic activities, making it important to identify the cell sublines used in work with HeLa.

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Chondrocytes obtained from tibiae of chick and rat at different developmental stages were cultured as three dimensional pellets in centrifuge tubes in medium containing different concentrations of serum for 28 days, to examine the changes in the alkaline phosphatase (ALP) activity as a marker of chondrocyte hypertrophy, changes in the calcium (Ca) contents as a marker of cartilage calcification and the development of hitological structure. Growth plate chondrocytes obtained from the proximal tibiae of 17.5 day chick embryos and 2.5 week old rats developed as a typical hypertrophied cartilage structure with rises in the ALP activity and the Ca contents, indicating the coincident results with the growth plate chondrocytes obtained from 3 or 4 week rabbits. Chondrocytes obtained from articulator cartilage in tibiae of 17.5 day chick embryos and 3 day newborn rats, which were used as more advanced differentiated chondrocytes, showed a partial hypertrophy and cartilageous structure with the high ALP activity and Ca contents in cell-pellets. Less differentiated prechondrocytes obtained from whole tibiae of 6.5day chick embryos showed a condensation of many fobroblastic cells and a poor hypertrophy in their histology of cell-pellets with a gradual rise in the ALP activity and low Ca contents. These results indicate that chondrocytes obtained from the tibial growth plate of chick and rat were suitable and useful materials for examining cellular and molecular process of cartilage differentiation in vitro.

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