Effects of Fixation on the Morphology of Paneth Cell Granules

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Abstract
Mouse Paneth cell granules fixed with formalin have been reported to be composed of a core consisting of a polysaccharide-protein complex which is surrounded by a shell or “halo” of acid mucopolysaccharide. Electron micrographs of granules fixed with 1% OsO4 in veronal-acetate buffer show that the halo may be merely a result of shrinkage of the granule. Similar results obtained after fixation with either 1% OsO4 in s-collidine buffer containing 1% sucrose (OsO4) or with 3% glutaraldehyde in cacodylate buffer containing 1% sucrose (GAS) strengthen the belief that the halo is a shrinkage space. Fixation in GAS for 1-4 hr followed by fixation for 1 hr in OsO4, however, reduced the halo to negligible proportions. This sequence of GAS and OsO4 improved the preservation of other cytoplasmic structures also. Staining with Alcian blue failed to demonstrate acid mucopolysaccharide in the halo; therefore, the separation of granule components into a core and a halo is probably a fixation artifact.