Nuclei Of Keratinocytes Research Articles

Evidence of diurnal variation of human epidermal cell proliferation. II. Duration of epidermal DNA synthesis.

In the epidermis of six healthy male volunteers the DNA synthesis time was measured by in vitro double labeling technique in a longitudinal study (48 h) with taking skin punch biopsies every 6 h. The external conditions of the experiments and one group of volunteers were identical to those of a previous study on LI of the epidermal keratinocytes. 14C-thymidine and 3H-thymidine were used for double labeling the DNA-synthesizing nuclei of keratinocytes. The duration of DNA replication time proved to be nearly constant, with minor fluctuation, during the entire time span of experiments (mean 6.19 +/- 0.3 h). Thus, the present results are in accordance with the conception that a periodically changing entrance rate of G1-cells into the S-phase of the generation cycle of keratinocytes is predominantly responsible for circadian variations in the number of DNA-synthesizing epidermal keratinocytes.

The Phagocytic Nature of the Keratinocyte in Human Epidermis After Tape Stripping

Tape stripping of human epidermis seldom removes the entire stratum corneum; it usually causes damage to the remaining tissue, and promotes an increase in cell turn- over. Tape stripping apparently damages the Langerhans cells. The keratinocytes often phagocytose parts of Langerhans cells following epidermal stripping. Inclusions containing Langerhans cell granules were also found within keratinocyte nuclei and these inclusions were usually not membrane limited. Autophagic vacuoles containing premelanosomes and melanosomes were often seen in melanocytes, strongly suggesting that melanocytes play an active role in melanosome degradation.