On cell kinetics in skin tumours of the Pacific English sole Parophrys vetulus Girard

Abstract. An autoradiographic study of the various types of neoplastic lesions in the skin of Pacific English sole Parophrys vetulus Girard was performed using peritoneally injected tritiated thymidine. The epidermis offish is mitotically active at all cell levels, the most important being the supra-basal layer. In the hyperplastically growing epidermis of the English sole covering connective tissue nodules and in the papillating epidermis prior to formation of enlarged ovoid cells (X-cells), the supra-basal layer also shows the greatest degree of labelling. Parallel to the appearance of these X-cells, which are characteristic of the skin tumours in Pacific flatfish, the distribution of DNA-synthesizing cells is altered. In the tumour areas which are more or less filled with X-cells the 'envelope cells' are labelled throughout with a uniform frequency. On the other hand, the directly adjacent X-cell free areas are labelled with a greater than average frequency.