Premature Chromosome Condensation of Synchronized Chinese Hamster Lung Cells

Abstract

The orderly, nonrandom pattern of nuclear chromatin is observable when it is condensed as visually distinct and structurally reproducible metaphase chromosomes. Interphase nuclei are susceptible to being induced to condense prematurely when by somatic cell fusion they become exposed to the influence of mitotic nuclei. The mitotic inducer has a differential effect on G_1, S, and G­_2 chromatin and produces varied premature condensation products. In the following experiments metaphase-G_1 fusions yielded single, elongated chromatids. The metaphase-S fusions resulted in pulverized condensation products. Metaphase-G_2 fusions produced sister, elongated chromatids. Sendai virus was used as the fusing agent in these experiments. The seed virus was injected into the allantoic cavity of 11-day chick embryos. Four days post injection the allantoic fluid was collected and titrated to give the desired virus concentration. The virus was subsequently inactivated by ultraviolet exposure. This inactive Sendai virus when suspended in medium with the Chinese hamster cells, produced cell fusion and the various premature condensation products. The percentages of these various fusion products were able to be influenced by using synchronized cell populations. Thymidine, hydroxyurea and colcemid were the drugs of choice to bring about synchrony. Both thymidine and hydroxyurea have the capability to produce a transient inhibition of DNA synthesis. Colcemid interferes with the polymerization of microtubules and therefore arrests cells in metaphase. When synchronized populations were fused and compared to asynchronous population fusions.