[Fluorescence study of X and Y chromatin in frozen sections]

Chinacrine fluorescence of the Y chromatin in histological sections is a useful tool for determination of nuclear sex. Nuclei of fibroblasts and smooth muscle cells seems to be most suitable for this investigation. Tissue specimens should be fixed for 5 minutes in hot formalin. Frequency of the Y chromatin in frozen sections of male origin was found to be 38--70 per cent, in paraffin embedded sections 28--44 per cent. It seems likely, that paraffin decreases chinacrin binding capacity of the Y chromatin. Frequency of the Barr-body in tissue specimens of female origin was found to be similar both in frozen and paraffin embedded sections. For the investigation of X and Y chromatin in tissue sections the technique of frozen sections should be used.