The ichthyosis mouse: histologic, histochemical, ultrastructural, and autoradiographic studies of interfollicular epidermis.

Interfollicular epidermis from back and tail of the recessive mutant mouse ichthyosis (ic/ic) was studied by histologic, histochemical, ultrastructural, and autoradiographic techniques and compared to heterozygous and Swiss S mouse epidermis. In the ic/ic mouse the stratum corneum was thickened, the granular layer prominent, and the stratum spinosum hyperplastic. Staining reactions for certain respiratory and lysosomal enzymes were more pronounced in epidermis of both back and tail. Ultrastructural studies of ic/ic epidermis demonstrated excessively clumped tonofilaments and increased numbers of mitochondria, ribonuclear protein particles, and membrane-coating granules in the stratum spinosum cells. Dilated intercellular junctions between the stratum spinosum and stratum granulosum cells were packed with membrane-coating and amorphous material. Profuse keratin-forming structures, abnormally large keratohyaline granules, and persistent mitochondria were seen in the stratum granulosum cells. In the stratum corneum, inclusions were prominent and persisted into the upper layers of cells, which were irregular in outline and greatly thickened. No differences in epidermal cell transit time or labeling index were demonstrated among the three types of mice.