Tissue fixation with diimidoesters as an alternative to aldehydes. II. Cytochemical and biochemical studies of rat liver fixed with dimethylsuberimidate

Abstract

Rat liver fixed with dimethylsuberimidate (DMS) was studied to investigate the use of diimidoesters as fixatives for light and electron microscopic cytochemistry. Paraffin sections of liver fixed with DMS at pH 9.5 were weakly stained with the ninhydrin Schiff procedure, indicating extensive reaction of NH3+ groups with the fixative. Nuclei were strongly stained by the Feulgen procedure, with no background reaction. In contrast, glutaraldehyde fixation resulted in a significant background reaction in the cytoplasm and nuclei in controls for the Schiff based stains. DMS fixed liver stained intensely for glycogen with the Periodic acid Schiff procedure, and biochemical analysis of glycogen retention and extractability indicated that DMS retained considerably more glycogen in sections than glutaraldehyde. DMS fixed liver incubated for thiamine pyrophosphatase activity revealed reaction product in ER cisternae, Golgi saccules and bile canaliculi. Peroxisomes were strongly reactive for catalase activity after incubation in diaminobenzidine medium, and reaction product of glucose 6 phosphatase activity was considerably greater following DMS fixation than after glutaraldehyde. Biochemical studies revealed up to twice as much residual activity of glucose 6 phosphatase after DMS fixation. These results suggest that DMS may be useful as a primary fixative for certain cytochemical procedures.