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Characterization of a new melanosomal structural componentȁthe vesicula globular bodyȁby conventional transmission, high-voltage, and scanning electron microscopy

1974; Academic Press; Volume: 48; Issue: 2 Linguagem: Inglês

10.1016/s0022-5320(74)80082-1

1878-2345

Kowichi Jimbow, Thomas B. Fitzpatrick,

Skin Protection and Aging

A new structural subunit, i.e., vesiculoglobular body, of the melanosome was found in fine structure studies of melanosomes in various tissues using conventional transmission (50ȁ80 kV), high-voltage transmission (800 kV), and scanning (25 kV) electron microscopes. The high-voltage electron microscope was used for 5 μm-thick sections to study the entire inner and outer structures of the melanosome. The scanning electron microscope was used to observe the three-dimensional structure of leached melanosomes that were treated with the bleaching agents, thioglycolic acid, and phenol, and a prolonged boiling at 130°C for 24 hours. The vesiculoglobular body, 400 Å in diameter, appears to be the structural element that is incorporated in the organization and melanization of the inner matrices of the melanosome. These bodies were found to be (a) present in all stages of melanosomal development, (b) increased in number during developmental stages, (c) attached to the surface of the lamellae of the inner matrices, (d) covered by osmiophilic fine grains of melanin moieties after melanization of the melanosome, (e) not melanized within themselves during an entire course of melanosomal development, (f) unchanged in size even though the melanosome changed in size, (g) not degraded, once they have been incorporated into the inner matrices, by phenol and thioglycolic acid and prolonged boiling at 130°C for 24 hours, and (h) uninvolved in the lysosomal degradation of melanosomes in the keratinocytes.