Sex Chromatin in Living Human Cells <i>In vitro</i>

Abstract

Cultured human cells from 3 females and 1 male were studied both in the living state in phase contrast and after fixation and Feulgen or thionin staining. A dense particle, the size of sex chromatin, is found lying adjacent to the nuclear membrane in 46% of living female cells. This particle is identical with the sex chromatin seen in the same cells after Feulgen or thionin staining. In 10% of living female cells the sex chromatin is very faint but becomes dense and distinct after fixation. In about 30% of female cells sex chromatin cannot be seen in the living state but can be clearly identified after fixation and Feulgen staining. In 10% of female nuclei no sex chromatin at all is found in Feulgen-stained preparations. A particle similar to sex chromatin is found only very rarely in living male cells. The fine structure of sex chromatin suggests that it consists of a folded thread, ½–1 <i>µ</i>mthick and 3–5 <i>µ</i>m long.It is concluded that the density or state of condensation of the sex chromatin is not the same in all nuclei in a particular culture at one time. No marked changes in structure and density of the sex chromatin occurred during the observation on single cells for periods up to 52 hours, except in one case, where a sex chromatin appeared in the hitherto homogeneous nucleus shortly before prophase.