Abstract
Melanocytes and melanin granules have been studied by electron microscopy in normal human and cat skin, and in hyperplastic human skin lesions. The melanocytes have always been found as free cells within the epidermis,i.e., on the epidermal side of the dermal membrane. Melanocytes frequently rest on the dermal membrane or bulge towards the dermis. In such cases the uninterrupted dermal membrane is uniformly thin and smooth in appearance, in contrast with the regions alongside Malpighian cells, where it appears appreciably thicker and seemingly anchored to the basal cell layer. Two types of melanin granules have been distinguished according to their location in the melanocytes and to morphological characteristics which may only express different stages in the maturation of the granules: (a) light melanin granules in which a structure resembling a fine network is apparent; (b) dense melanin granules which, in osmium-fixed preparations, appear as uniformly dense masses surrounded by a coarsely granular, intensely osmiophilic shell. Treatment of sections of osmium-fixed tissues with potassium permanganate has revealed within the dense granules the existence of an organized framework in the form of a regular, crystalline-like lattice. It is suggested that this basic structure is protein in nature and may include the enzymatic system capable of producing melanin. The existence is reported of fine filaments located in the cytoplasm of melanocytes and morphologically distinct from the tonofilaments found in Malpighian cells.
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Selected References
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- BIRBECK M. S., CUCKOW F. W. The electron microscopy of human hair pigments. Ann Hum Genet. 1955 Feb;19(3):231–249. doi: 10.1111/j.1469-1809.1955.tb01346.x. [DOI] [PubMed] [Google Scholar]
- BIRBECK M. S., MERCER E. H., BARNICOT N. A. The structure and formation of pigment granules in human hair. Exp Cell Res. 1956 Apr;10(2):505–514. doi: 10.1016/0014-4827(56)90022-2. [DOI] [PubMed] [Google Scholar]
- LUFT J. H. Permanganate; a new fixative for electron microscopy. J Biophys Biochem Cytol. 1956 Nov 25;2(6):799–802. doi: 10.1083/jcb.2.6.799. [DOI] [PMC free article] [PubMed] [Google Scholar]
- ODLAND G. F. The fine structure of the interrelationship of cells in the human epidermis. J Biophys Biochem Cytol. 1958 Sep 25;4(5):529–538. [PMC free article] [PubMed] [Google Scholar]
- PALADE G. E. A study of fixation for electron microscopy. J Exp Med. 1952 Mar;95(3):285–298. doi: 10.1084/jem.95.3.285. [DOI] [PMC free article] [PubMed] [Google Scholar]