Birefringence and Paraffinophilia of Cell Nuclei

Birefringence of cell nuclei was present in most tissues but seen exclusively in paraffin sections. Only after staining with an acridinc derivative (rivanol) was it found in smears and frozen sections. Although retention of paraffin in the nucleus contributes, for the most part to its anisotropy, present evidence supports the hypothesis that the chemical nature and the physical state of nuclear material, especially of the DNA, plays the important role as a substrate, which selectively binds of paraffin molecules. This evidence is based mainly on the blocking effect on birefringence which occurs when small pieces of tissues are treated in toto, before paraffin embedding, with DNA-extracting procedures and nuclear stainings. Moreover, the variability in degree and extent of birefringence noted in different tissues corroborates this view. Factors in the preparatory procedure, i.e, deparaffinization, hydration and dehydration, were found to affect markedly the binding of paraffin to nuclear substance. Nevertheless, if paraffin affinity for nuclei is not considered, it may introduce inaccuracies into methods designed to determine the nuclear mass quantitatively, after staining.