Frequency of sex chromatin and number of nucleoli in cells grown in tissue cultures from normal human subjects and human subjects with supernumerary x-chromosomes.

Abstract

The frequency of sex‐chromatin‐positive cells and the number of nucleoli/cell were studied in relation to growth phase in cultures of skin fibroblasts from normal human males and females, one 46‐XX male, four 47‐XXY males and three 48‐XXXY males. The main conclusions are: 1) The frequency of sex‐chromatin‐positive cells is low in the logarithmic growth phase, but rises very close to 100 per cent in the postlogarithmic phase in normal females as well as in sex‐chromatin‐positive males. 2) In three 48‐XXXY males investigated the frequency of cells with two Barr bodies showed minima of 22, 20 and 22 per cent in the logarithmic phase and maxima of 90.5, 75.5 and 71.5 per cent in the postlogarithmic phase. 3) The location of the Barr body changes during growth with a significant rise in the relative frequency of Barr bodies non‐adjacent to the nuclear membrane (i.e. juxtanucleolar and intermediary Barr bodies) from logarithmic to postlogarithmic phase. 4) The average number of nucleoli per cell is significantly higher in normal females than in normal males and significantly higher in the three 48‐XXXY males than in the normal female controls. 5) The average number of nucleoli per cell increases significantly during the logarithmic growth phase reaching a maximum at day 5, 6 or 7. 6) There is no difference between the average number of nucleoli in Barr‐positive and Barr‐negative cells. It is suggested that the explanation of fact No. 4 is that the heterochromatic X‐chromosome is nucleolus‐organizing and has a stronger nucleolus‐organizing action than the Y‐chromosome, and that facts Nos. 3 and 5 may be a consequence of an alteration in the distribution of the cells in the different intermitotic phases during the growth period.