Abstract
Histochemical and ultrastructural studies demonstrate that keratohyalin can be mobilized from fresh specimens of cattle hoof epidermis by 1.0 M potassium phosphate buffer (pH 7.0). Macroaggregates with histochemical characteristics identical to those of in situ keratohyalin granules (staining by Harris' hematoxylin, Congo red, diazotized sulfanilic acid, sodium alizarin sulfonate, toluidine blue, methyl green-pyronin, and acridine orange) and with similar morphological characteristics at the ultrastructural level are formed upon dialyzing the extracted keratohyalin against distilled water. Staining by basic dyes (toluidine blue, methyl green-pyronin, and acridine orange) is abolished by treating either in situ keratohyalin granules or isolated macroaggregates with ribonuclease. Electrophoresis of isolated macroaggregates on polyacrylamide gels in the presence of sodium decylsulfate results in the fractionation of a 13 member oligomeric series of ribonucleoproteins and two non-homologous species of ribonucleoproteins. The oligomeric series can be purified by isolating "stacked" oligomers on low concentration (3%) polyacrylamide gels. Fractionated oligomers on polyacrylamide gels and aggregates formed from purified ribonucleoproteins demonstrate histochemical characteristics identical to those of in situ keratohyalin granules. Aggregates formed from denatured ribonucleoproteins are highly disordered and are markedly different from in situ keratohyalin granules or nondenatured isolated macroaggregates at the ultrastructural level, possibly due to irreversible denaturation of the oligomers by sodium decylsulfate.