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Date of Award

7-1976

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

Abstract

The responses of primary root cells of Vicia faba to two methylxanthines, 8-ethoxycaffeine and 3-isobutyl-1 methylxanthine were compared. The object was to determine whether or not the binucleate condition, induced by treatment with methylxanthines, could be used to estimate cell cycle duration in a marked subpopulation of cells. Binucleate cells induced by EOC did not divide; about 75% of those induced by IBMX had a cell cycle duration of 15-16 hours, i.e. close to the duration estimated for fast cycling cells.

Methylxanthines may also induce other effects, e.g. (1) chromatid stickiness and tetraploid nucleus formation, (2) depression of mitotic index EOC and IBMX differed in their ability to induce these changes.

Using binucleate cells, nuclear growth was followed throughout interphase. Nuclei did not grow continuously throughout interphase; there was a period of little or no growth initially and then a period in which the nuclei contracted. In IBMX induced binucleate cells, nuclear growth occurred and was rapid in the 2 hours prior to the entry of nuclei into mitosis. The other aspect of nuclear growth that was studied concerned the relative growth of the two sister nuclei of a binucleate cell. Sister nuclei were rarely of identical volumes.

In most cases, large differences were seen between sister nuclei; these differences were maintained throughout interphase and into prophase. Nuclear shape changed during interphase but sister nuclei in a binucleate cell tended to have the same shape. The change in nuclear shape and the volume differences between sister nuclei are discussed in terms of nucleo-cytoplasmic interactions and the origin of the differential behaviour of sister nuclei present in a common cytoplasm.

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