On the association of centrioles with the interphase nucleus.

Preparations of nuclei from rat liver and bovine spleen purified by centrifugation through dense sucrose solutions are shown to contain centrioles. These centrioles retain their in situ ultrastructure and are surrounded by a network of filaments adjacent to the nucleus and probably attached to it. The number of centrioles in isolated nuclei depends on the conditions of cell homogenization. Under certain conditions of homogenization, the fraction of purified nuclei contains almost all centrioles of the original tissue. The number of centrioles in isolated nuclei sharply decreases if the nuclei are rehomogenized under conditions that do not cause damage to nuclei. The number of nucleus-associated centrioles does not decrease after solubilization of nuclear membranes by Triton X-100. Nuclei retain the associated centrioles after treatmentwith RNase-free DNase I. It is concluded that in interphase the centrioles are associated with the nucleus and that this association which is probably mediated by filaments involves nuclear structures other than nuclear membranes or whole chromatin.