The effects of p-DL-fluorophenylalanine on chromosome movement and cytokinesis of human amnion cells in culture

Testing for the chemical induction of aneuploidy in the male mouse

Dyad scores of metaphase II spermatocytes in the mouse have been used as an end point to assess the aneuploidy-inducing potential of three different chemicals; p-fluorophyalanine, phenylalanine and 6-mercaptopurine. The sensitivities of three different spermatogenic stages have been tested; pre-leptotene, zygotene and metaphase I. No effect was found at any treated stage for 6-mercaptopurine and phenylalanine. p-Fluorophenylalanine, when compared to control treatments, did, however, induce non-disjunction when applied at metaphase I. It also caused a delay to spermatogenesis when applied at this stage. The potential of mammalian test systems for the routine screening of chemicals as non-disjunction inducers, is discussed.

Alterations in metaphase durations in cells derived from human tumours

With the use of time-lapse cinemicrography, we previously found that metaphase durations were significantly prolonged in SV40-transformed human fibroblasts when compared to untransformed controls. This was consistent with some earlier reports and suggested that prolonged metaphases could account for high metaphase/prophase ratios and possibly, in part, for increased mitotic indices seen in advanced tumours. However, there are inconsistencies in the literature and no comparable data available from malignant carcinomas. Presented in this paper are data from two cervical dysplasias, two cases of carcinoma in situ, nine malignant carcinomas and several other types of human cells. The results show that mean metaphase durations were prolonged in cells derived from most of the carcinomas but not from the other cell types. On the other hand, cytokinesis appears to progress more rapidly than normal in most of the tumour-derived cells. These and other findings indicate that the changes are a result of some metabolic alteration common to many but not all tumour cells. For reasons presented, we suggest as a working hypothesis that the alterations may be due to changes in calcium regulation, possibly resulting from alterations in mitochondrial metabolism.

A dominantly inherited cytogenetic anomaly: a possible cell division mutant

Short-term lymphocyte cultures from three unrelated patients showed an increased frequency of mitoses with separated centromeres and splayed chromatids in the presence of colcemid. We refer to this phenomenon as premature centromere division (PCD). In two of the three patients the frequency of PCD in lymphocytes decreased when colcemid was omitted prior to harvest but was still higher than controls, whereas in the third patient, the frequency appeared unchanged. Cultured fibroblasts from the latter patient exhibited increased tetraploidy and multinucleated cells. Transmission of the trait in the three families was compatible with autosomal dominant inheritance. Time lapse cinemicrographic studies on fibroblasts from one patient demonstrate a shortened metaphase time, suggesting that the separation of chromatids observed in this patient may indeed be premature. The nature of the mutation(s) and phenotype correlation if any is unknown.

On the duration of mitotic stages in senescing human fibroblasts in culture

The duration of three mitotic periods was measured by time-lapse cinemicrography in a line of normal human fibroblasts which displays the phenomenon of limited growth potential in vitro. It was found that the durations of metaphase and anaphase did not change as a function of passage level but that there was a statistically significant increase in the duration of cytokinesis. It was also found that there was no progressive increase in the variance of these periods between early and late passage cells. The data suggest that for those late passage cells which still retain the capacity to divide, the cellular mechanisms responsible for the synthesis of functional proteins, energy regulation and at least some membrane functions appear to be working normally.