Osmium dependent argentaffin staining of lysosomes

Application of Grimelius argyrophil staining to the study of tumour ultrastructure. III. Effects of osmium tetroxide

The results obtained in electron microscopy for Grimelius (1968) argyrophil staining by the en bloc staining of Vassallo and the staining on section of Håkanson were compared on tumoral and non-tumoral tissue samples and were found to lead to different results. Our earlier results for the en bloc staining method indicated that the fixative used in this process was important and that embedding in resin followed by staining of section weakened silver impregnation. We examined here the effects of OsO4 post-fixation combined with such embedding and found that staining was obtained within a shorter period and was more intense. This staining on section was not specific enough, since it was observed in secretory granules of non-argyrophil cells such as those containing somatostatin. In addition, this staining was not confined to specific peripheral zone as it occurred after en bloc staining; particularly in secretory granules with double structure including a core such as those containing glucagon in the pancreas or certain granules in tumoral carcinoid tissue. Consequently silver deposits were located both in the core and peripheral zone of such granules. Moreover, after OsO4 post-fixation, embedding in resin, and staining on section, argentaffin and argyrophil properties intermingle.

The electron density of light and dark lysosomes in the proximal convoluted tubule of the rat kidney

The present paper deals with the electron density of the lysosomal matrices in the renal proximal-convoluted-tubule cells of Wistar rats (20-60 days of age). Its purpose was to determine which physicochemical factors influence the electron density of lysosomes, and how their electron density is affected by various methods of fixation.--3 types of lysosomes can be distinguished in the proximal-convoluted-tubule cell; namely light, intermediate and dark lysosomes, which have an electron density lower, equal to or higher than the surrounding cytoplasm. All 3 types of lysosomes were invariably present after all methods of fixation tested. Light, intermediate and dark lysosomes differ in several respects. Staining intensity with uranyl acetate, lead citrate and potassium permanganate, osmiophilia, basophilia (in semithin sections) and --probably most importantly--the physical mass density of the lysosomal matrix are all low in light lysosomes, higher in intermediate lysosomes and highest in dark lysosomes. Light, intermediate and dark lysosomes of the proximal convoluted tubule do not form discrete classes, but one continuous spectrum of lysosomes of increasing electron density.