Autofluorescent particles of human uterine muscle cells

Smooth muscle tissue collected from the uterine fundus of 24 patients undergoing hysterectomy was examined for chromolipoid pigments by histochemical and electron microscopic techniques. Certain cytoplasmic particles were found, mainly in smooth muscle cells, which exhibited characteristic autofluorescence, sudanophilia, and acid phosphatase activity but did not correspond to any typical pigment described previously. These particles were present in all subjects and they tended to increase in number with age. Chemical tests on tissue lipid extracts failed to prove that vitamin A was responsible for the fluorescence. The ultrastructural appearance of the particles somewhat variable, but most particles were rounded and of low electron density, with a lucent central space and dense bodies, probably lysosomes, at the periphery. The whole complex was enclosed by a single trilaminar membrane.