Transmission and Scanning Electron Microscopy and Freeze‐Fracture Replication of Normal Human Melanocytes and Human Melanoma Cells in Tissue Culture

Abstract

Basic LM, TEM, SEM, and FFR appearances of a pure line of normal human melanocytes derived from foreskin, and a human melanoma line, in cell culture are described. Normal melanocyte cultures exhibit side by side, cells of widely different melanogenic activities--possible clones--and melanosomes of bizarre shape and internal structure are frequent. Aggregates of melanosomes, with or without associated amorphous material, and with no discernible limiting membrane are present within many cells, and occasional simple specialised contacts occur between apposed cells. On replicas of plasma membrane of normal melanocytes, particle densities and diameters on P and E fracture faces were within the ranges for cells in general, and equivalent data for the melanoma cells were not significantly different. Similarly, there was no difference in density of distribution or diameter of nuclear pores between the normal and the tumoural cells.

Behavioral differences between donor site-matched adult and neonatal melanocytes in culture

“…Based on ultrastructural study, the melanosomes of adult melanocytes were distributed singly along the dendrites, whereas they were aggregated in the perinuclear cytoplasm of neonatal melanocytes. It has been suggested that aggregates of melanosomes or macromelanosomes are manifestations of autophagic activity (Hirone and Eryu 1978;Nakagawa et al 1984;Ortonne and Perrot 1979) due to impaired evacuation of "constipated" melanosomes (Breathnach et al 1988). In nevus depigmentosus which appears to result from melanosome aggregation and a transfer block, melanocytes have poorly developed, stubby dendrites and aggregated melanosomes (Mosher et al 1993).…”