| Abstract |
During the period prior to the sudden increase of mitotic activity the
cells were transferred to new flasks every other week. In this way the
NHIK 3016, NHIK 3017, NHIK 3025 and NHIK 3043 cells were cultivated over
9, 7, 7 and 8 passages, respectively. Later the cells were handled as
stock cultures, cultivated as monolayers in Jena G20 square flasks, and
trypsinized once a week. To date (May 1969) they have been cultivated over
73, 73, 67 and 43 passages, respectively, after the increase of mitotic
activity. To prevent loss of cells, each of the strains was separated into
two groups, and these were handled separately (by different persons, with
serum from different blood donors, in different incubators etc.). For the
same reason, but also in order to prevent the cells from being mixed and
in order to preserve cells with unaltered properties, they were frozen in
liquid nitrogen shortly after the increase in mitotic activity. The
following properties of the four cell strains were studied: (1) The
morphology and growth pattern of the cells; (2) the mitotic activity and
the duration of mitotic stages (partly by means of the Colcemid technique);
(3) plating efficiency; (4) chromosomes of cells in metaphase.
(Chromosomes were counted for analysis of the distribution of chromosome
number, and detailed karyotype analyses were made.) The results of these
studies will be presented and discussed.
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