New melanogenesis and photobiological processes in activation and proliferation of precursor melanocytes after UV-exposure: ultrastructural differentiation of precursor melanocytes from Langerhans cells
Photobiological processes involving new melanogenesis after exposure to ultraviolet (UV) light were experimentally studied in C57 black adult mice by histochemistry, cytochemistry, and autoradiography. The trunk and the plantar region of the foot, where no functioning melanocytes were present before exposure, were exposed to UV-A for 14 consecutive days. Both regions revealed a basically similar pattern for new melanogenesis which involved an activation of precursor melanocytes. Essentially all of ''indeterminate'' cells appeared to be precursor melanocytes, the fine structure of which could be differentiated even from poorly developed Langerhans cells. New melanogenesis was manifested by 4 stages of cellular and subcellular reactions of these cells as indicated by histochemistry of dihydroxyphenylalanine (dopa) and autoradiography of thymidine incorporation: (a) an initial lag in the activation of precursor melanocytes with development of Golgi cisternae and rough endoplasmic reticulum followed by formation of unmelanized melanosomes (day 0 to 2); (b) synthesis of active tyrosinase accumulated in Golgi cisternae and vesicles with subsequent formation of melanized melanosomes in these cells (day 3 to 5); (c) mitotic proliferation of many of these activated cells, followed by an exponential increase of new melanocytes (day 6 to 7); and (d) melanosome transfer with differentiation of 10 nm filaments and arborization of dendrites, but without any significant change in the melanocyte population (day 8 to 14). The melanosome transfer was, however, not obvious until after 7 days of exposure. The size of newly synthesized melanosomes was similar to that of tail skin where native melanocytes were present before exposure.
- Research Organization:
- Department of Dermatology, Sapporo Medical College, Japan
- OSTI ID:
- 5343365
- Journal Information:
- J. Invest. Dermatol.; (United States), Vol. 78:2
- Country of Publication:
- United States
- Language:
- English
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ANIMAL CELLS
BIOLOGICAL RADIATION EFFECTS
CELL DIFFERENTIATION
RADIOINDUCTION
CELL PROLIFERATION
MELANIN
AUTORADIOGRAPHY
CYTOCHEMISTRY
DOPA
MICE
NEAR ULTRAVIOLET RADIATION
AMINO ACIDS
ANIMALS
AUTONOMIC NERVOUS SYSTEM AGENTS
BIOCHEMISTRY
BIOLOGICAL EFFECTS
CARBOXYLIC ACIDS
CHEMISTRY
DRUGS
ELECTROMAGNETIC RADIATION
HYDROXY ACIDS
HYDROXY COMPOUNDS
MAMMALS
NEUROREGULATORS
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PIGMENTS
RADIATION EFFECTS
RADIATIONS
RODENTS
ULTRAVIOLET RADIATION
VERTEBRATES
560121* - Radiation Effects on Cells- External Source- (-1987)
560152 - Radiation Effects on Animals- Animals