From Big Medical Encyclopedia

PARAKERATOSIS (grech, para near + a keratosis [y]) — the disturbance of process of keratinization connected with loss of ability of cells of epidermis to produce eleidin. The item is observed at psoriasis, eczema, dermatitis, pink herpes.

Fig. 1. Microdrug of skin at a parakeratosis: shooters specified cells of a corneous layer with the rhabdoid kernels containing a large amount of DNA; Feylgen's reaction; X 150.
Fig. 2. The diffraction pattern of a cell of epidermis at a parakeratosis: 1 — the extended kernel; 2 — lipidic granules; X 14 400.

At P. the thickening horn and partial or total disappearance of a granular layer of epidermis is noted. Cells of a corneous layer of epidermis have the rhabdoid kernels containing a significant amount of DNA (fig. 1) and the condensed cytoplasm in a cut lipids, neutral mucopolysaccharides, nedookislenny SH groups of protein are defined. In them small activity of the enzymes catalyzing education remains vysokoergichesky connections (see) that testifies about them funkts, activities.

At electronic microscopic examination existence in cytoplasm of ribosomes, polyribosomes, a large number of lipidic granules (fig. 2), the remains of tonofilaments is noted. Granules of eleidin, as a rule, are absent. The Item

is the cornerstone ratio distortion between proliferative activity and a differentiation of cells of epidermis, the reason to-rogo is still unknown, however nek-ry researchers attach great value to chalones — the substances which are specifically suppressing cell division (see. Chalones ) and influencing contents in them hell-nozinmonofosfornoy to - you are (AMF) and guanozinmonofosforny to - you are (GMF). It is shown that decrease in maintenance of the AMF form (3', 5' - AMF) and increase in the GMF form (3', 5' - GMF) in cells leads to stimulation of cellular proliferation and delay of a cellular differentiation.

See also Keratinization .

G. M. Tsvetkova.