THREE-DIMENSIONAL STRUCTURE OF IN VIVO MELANOCYTES

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To know the three-dimensional distribution and cell structure of human epidermal melanocytes in vivo, normal skin specimens were studied with newly developed stereographic and stereometric method using computer. After fixation, the specimens were received dihydroxyphenylalanine (DOPA)-premelanosome reaction. They were post- fixed with glutaraldehyde and osmium tetroxide, dehydrated, and embedded in Epon. Serial sections of each specimen were made in an ultramicrotome and stained with toluidine blue. Epidermal melanocytes were stained dark brown by the DOPA-premelanosome reaction. From the serial two-dimensional figures of the melanocytes, three-dimensional images of their cell structures were reconstructed using a computer- stereography system (Cosmozone 2SA, Nikon, Tokyo). The epidermal melanocytes stereographically showed an uneven distribution on a waving epidermal basement membrane; some of them often gathered. The melanocytes showed a spherical cell body extending several thin processes, whereas epidermal basal keratinocytes showed an ellipsoidal cell body. By stereometry, the melanocytes had significantly larger cytoplasm and a smaller nucleus in volumes than those of the basal keratinocytes. These results may be very important for further stereological studies on various kinds of normal or abnormal melanocytes.