An electron microscopic autoradiographic study of proline incorporation by mouse lingual epithelium

Histochemistry of the keratohyalin granules in human oral leukoplakia

The keratohyalin granules from 25 human oral leukoplakias, showing benign hyperorthokeratosis histologically, were examined employing a series of histochemical techniques. The tissues were fixed in 10% neutral buffered formalin, 80% methanol, or Carnoy's fluid. The keratohyalin granules stained intensely with Pauly's reagent, Congo red and Harris hematoxylin, indicating the presence of proteins. This was confirmed by abolishing the staining reaction by pretreatment with proteolytic enzymes. The keratohyalin granules also reacted with methyl green-pyronin by staining pink at their peripheries; this staining was abolished by pretreatment with ribonuclease, indicating the presence of ribonucleotides. The keratohyalin granules partially stained with toluidine blue and colloidal iron, indicating the presence of acid polysaccharides. The keratohyalin granules did not react with the Feulgen reagent, suggesting the absence of DNA. Our studies indicate that the keratohyalin granules in human oral leukoplakia are primarily protein(s) complexed with polyribonucleotides. The presence of a carbohydrate moiety suggests the possibility of a protein-polysaccharide component in the granules.

Heterogenous proteins in keratohyaline granules studied by quantitative autoradiography

Electron microscopic autoradiography with [3H]histidine, [3H]cystine, I13H]arginine, and [3H]proline was used to study protein synthesis in keratohyaline granules of newborn rats. All 3H-amino acids were incorporated into proteins in the granular cells, and the radioactive proteins appeared in the keratohyaline granules. However, the amount of radioactivity associated with the granules and the pattern of ultrastructural localization of the radioactive proteins differed considerably for each 3H-amino acid. "Histidine-labeled" protein was located mainly in the matrix portion of keratohyaline granules whereas "cystine-labeled" protein accumulated in the dense homogenous deposits. "Arginine-labeled" protein was distributed more diffusely in the organelles of granular cells, but that associated with keratohyaline granules seemed to localize mostly with "histidine-labeled" protein and partly with "cystine-labeled" protein. Large amounts of "proline-labeled" protein were also present in other areas of the cytoplasm than keratohyaline granules. This protein localized in the dense homogeneous deposits, but it seemed to turn over more rapidly than "cystine-labeled" protein, an indication that the dense homogenous deposits consist of at least two different polypeptide chains, one of which contains higher cystine and the other higher proline.