MAGENTOSIS IN HUMAN LACTATING BREAST - A MODE OF CELL-DEATH ACCUMULATING SINGLE-STRANDED-DNA STRETCHES OR BREAKS

Pale and homogeneous-looking nuclei of degenerative acinar cells selec tively seen in an early regression stage of the human lactating breast were periodic acid-Schiff (PAS)-reactive. In our preceding paper, thi s peculiar morphologic feature was designated as 'magentosis'. The pre sent paper was aimed at histochemically clarifying the nature of tile 'magentotic' nuclei. The diffuse PAS reactivity was not influenced by pretreatments with alpha-amylase, DNase, RNase, proteinase K, nor by h ydrochloric acid or heating. The nuclei were negative for acid mucosub stances and secretory glycoproteins, and were unreactive with a variet y of lectins. In contrast, the presence of single-stranded DNA stretch es or breaks was proven. The 'magentotic' nuclei in non-heated paraffi n sections were hybridized with a heat-denatured DNA probe for human D NA consensus sequences and were focally immunoreactive with an antibod y to single-stranded DNA. The terminal deoxynucleotidyl transferase-me diated dUTP nick end-labeling (TUNEL) method turned to be positive aft er digestion by mung bean nuclease, a single-stranded DNA-specific enz yme. The 'magentotic' nuclei were further clearly labeled by the in si tu nick translation method. The nucleoli were devoid of reactivity for both the PAS and single-stranded DNA signals. We propose that 'magent osis' represents a unique mode of cell death, distinct from apoptosis and necrosis or oncosis. The PAS reactivity in the 'magentotic' nuclei may be correlated with the occurrence of single-stranded stretches or breaks in the DNA chain.