[Ultrastructure of the mitotic apparatus of metaphase cells in a pig embryo kidney tissue culture after stopping the action of 2-mercaptoethanol]

Abstract

The ultrastructure of the metaphase mitotic apparatus has been studied in the KEPV cells during 6 hours after the removal of 2-mercaptoethanol (0.001 M). Starting from the analysis of chromosome disposition, the structures of the kinetochore regions and of the mitotic spindle poles, and the degree of integrity of the mitotic spindle microtubules, six types of metaphase cells were revealed. A comparison of the results of the present paper with those of the earlier studies enabled us to present the dynamics of the metaphase mitotic apparatus reconstruction. Four basic stages are revealed in this process. At the first stage, the K-metaphase centrioles form diplosomes again, the number and extent of kinetochore microtubules increase too. At the second stage, the metaphase plate forms, but interpolar and astral microtubules are absent. At the third stage, the structure of the kinetochore regions becomes normal. Thus, the metaphase plate may have formed before the orientation of kinetochores to the poles took place. At the fourth stage, the interpolar and astral microtubules appear; the mitotic spindle reestablishes completely. It is supposed that the formation and functioning of the mitotic apparatus is not confined to the interaction of microtubules of different types.