Ultrastructural variations following use of several weakly protic alcohols as dehydration agents.

: Evaluation has been made of ultrastructural variations which obtain following dehydration and infiltration of glutaraldehyde plus osmium fixed CHO cells with the weakly protic alcohols (methanol, ethanol, ethylene glycol, 1-propanol, 2-propanol, propylene glycol and glycerine), acetone alone, and with use of acetone and propylene oxide as transition solvents subsequent to dehydration with ethanol, methanol and ethylene glycol. It appears that the weakly protic alcohols, applied without transition solvent, in addition to some extraction by themselves, variously condition the components of membranes, etc, for possible further extraction by the embedment resin. Extraction by embedment consists mainy of removal of aggregate or 'corpuscular' units from regions assumed to have originally consisted of endomembrane. Relatively discrete extraction pits in membranes are noted in the cases of methanol and ethylene glycol dehydration without transition solvent; whereas use of the other alcohols such as 1-propanol and 2-propanol accentuate the visualization and staining of mitochondrial ribosomes. Cytoplasmic ribosomes stain more strongly when acetone or ethylene glycol are employed as dehydration agents, but some size (length) differences obtain. Apparently, acetone or propylene oxide transition following dehydration with ethanol or methanol (but not the glycols) assists in, or fixes, alterations of endomembrane components into the familiar 'unit membrane' orientation upon which the embedding substances have little discernible effect. Glycol dehydration and infiltration regimens (especially ethylene glycol alone and as a dehydration agent in the application of Bernhard's (1969) staining technique) result in lesser electron density of heterochromatin while accentuating RNP particles. The increased electron density of heterochromatin while accentuating RNP particles. The increased electron density of the RNP particles and the decrease in density of the heterochromatin result in improved visualization of the relationships among nucleolar RNP particles and the nuclear pore complexes.