Rodlet cells in the gill and intestine of Catostomus commersoni and Perca flavescens: a comparison of their light and electron microscopic cytochemistry with that of mucous and granular cells
Rodlet, mucous, and granular cells from the gills and intestines of two teleosts, Catostomus commersoni and Perca flavescens, were examined using light and electron microscopic cytochemical methods. The peripheral substance in the bipartite granules of rodlet cells was positive for carbohydrates (periodic acid – Schiff (PAS)) and proteins (e.g., coupled tetrazonium) but was uncolored by stains for lipid (Sudan black), nucleic acids (e.g., gallocyanin), and chemical groups of certain carbohydrates (e.g., alcian blue (AB), pH 1.0). The core of the granules showed positive protein but no carbohydrate, nucleic acid, or lipid staining. Electron microscopy revealed granules with (1) a protease resistant, periodic acid – silver methenamine positive periphery probably rich in glycoprotein and (2) a protease-digestible, silver methenamine negative core, perhaps of relatively pure protein. The granules were resistant to ribonuclease digestion. Mucous cells generally stained more strongly than rodlet cells for carbohydrate (PAS, AB, pH 2.5 and 1.0; periodic acid – silver methenamine) and had a greater range of staining intensities indicating a more variable carbohydrate component. Protein and lipid stains left mucus granules uncolored. Granular cells of P. flavescens were moderately PAS positive and stained strongly for protein. Granular cells of C. commersoni were strongly PAS positive and stained moderately for protein; their granules exhibited periodic acid – silver methenamine positive rims and unstained central "nucleoids."