The role of the centriolar region in animal cell mitosis. A laser microbeam study.

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Abstract
An Ar ion laser microbeam (488 and 514 nm) was used to selectively irradiate 1 of the 2 centriolar regions of rat kangaroo Potorous tridactylis (PtK2) phosphase cells in vitro. The cells were sensitized to the laser radiation by treatment with acridine orange (0.1-0.2 .mu.g/ml). Ultrastructural examination of irradiated centriolar regions demonstrated that the primary site of damage was the pericentriolar material. Hence, nucleic acid may be present in the pericentriolar material. Behavioral and ultrastructural analysis demonstrated that cells with 1 damaged pericentriolar zone could undergo nuclear membrane breakdown, chromosome condensation, metaphase plate formation and cytokinesis, but the chromosomes neither separated nor exhibited any anaphase movements. Detailed ultrastructural analysis revealed the presence of kinetochore microtubules on both sides of the chromosome mass and a lack of microtubules in the cytokinesis constriction. The pericentriolar material is important in spindle organization and essential for the formation of the interpolar microtubules.