Electron microscope observations of the melanocyte of the human epidermis

Using standard osmium fixation and methacrylate embedding techniques, a study has been made of the melanocyte of human biopsy skin removed under general and local anaesthesia. Melanogenesis was easily observable in the melanocytes, but immature pigment granules were rarely seen in the Malpighian cells. The passage of melanin from melanocyte to Malpighian cell—cytocrine secretion—is thought to have been observed. Phagocytes near the dermal-epidermal junction seem to have their pigment granules in vacuoles, rather than surrounded directly by the cytoplasmic matrix as in the melanocytes. This, together with the failure to observe "effete" melanocytes, prompts the suggestion that the phagocytes are melanocytes which have migrated from the epidermis into the dermis. A melanin granule is shown with alternating dark and lighter transverse striations, concerning which structure little can at present be said.

Chromaffin reacting cells in human digital skin

These studies demonstrated the existence of chromaffin-reacting granules in the human skin. The chromaffin reaction was provided by bichromate fixation. Subsequent special staining by the modified Sevki procedure revealed these granules to be localized usually to characteristic long, eel-like cells with distinctive tinctorial features. Although the true significance of these cells is not certain, they are believed to represent the local source of a vasopressor material for the peripheral tissues. Much indirect physiologic evidence supports this belief.

The fine structure of the adepidermal reticulum in the basal membrane of the skin of the newt, Triturus

The unique reticulum in the basal membrane of the adult newt's skin consists of a series of nodular swellings from which there radiate fibers. Electron micrographic studies showed that the nodules consist of layers of fibrillae arranged approximately and irregularly at right angles to one another. Some are packed to form a capsule; still others extend into the internodular zone to form the radiating fibers. The fibrils are banded and are revealed best after fixation with potassium permanganate. The reticulum is compared with that of the larval newt and the frog tadpole. The epidermal side of the reticulum is bounded by a membrane separated from the plasma wall of the epidermal cell by a clear space. These we have termed adepidermal membrane and space, and have compared them with similar structures in larvae.

Electron microscope studies of the human epidermis; the cell boundaries and topography of the stratum malpighii

The thin skin of the left upper quadrant of the human abdomen has been studied by electron microscopy. Tissue removed with a high speed rotary punch was fixed in osmium tetroxide or potassium permanganate. The latter fixative in our preparations is superior to osmium for the demonstration of epidermal cell membranes and certain other membranous structures of the epidermis. The cytoplasmic membranes of basal cells and cells of the stratum granulosum have been found to be relatively straight, while those of most spinous cells are sharply scalloped. The deep cells of the stratum spinosum in the rete ridge area show cell membranes and cytoplasmic structure intermediate between true basal cells and most cells of the stratum spinosum. The extracellular material of the desmosome has been found to consist of alternate dark and light laminae similar to those described by Odland (13) and Horstmann and Knoop (7).

Electron microscope studies of the human epidermis: the clear cell of Masson (dendritic cell or melanocyte)

The human epidermis has been studied by electron microscopy following osmium tetroxide and potassium permanganate fixation. An anatomically distinct cell in the human epidermis has been demonstrated with features similar to the melanocyte of the hair bulb described by Barnicot, Birbeck and Cuckow (3). It is dendritic in form and does not contain tonofilaments. "Intercellular bridges" are not formed. The mitochondria are larger and more numerous than those of other epidermal cells and the endoplasmic reticulum is more complex. Some of these cells contain melanin but others are melanin-free. The cell has been interpreted as being identical with the dopa-positive, clear cell of Masson (dendritic cell of Bloch or melanocyte). We have found that many membranous structures in the human epidermis are better preserved by permanganate fixation than by osmium tetroxide fixation.

Fine structure of the larval anuran epidermis, with special reference to the figures of Eberth

Small pieces of skin from 8 cm long Rana clamitans larvae were fixed in OsO(4), washed, dehydrated, and embedded in a methacrylate mixture. Ultrathin sections were cut on a Porter-Blum ultramicrotome and were examined in an RCA electron microscope, type EMU 2D. The sections showed that aggregates of fibrous material in the cells of the inner layer of epidermal cells are identical in disposition and size with the classical figures of Eberth. It is conclusively shown that these figures do not arise from an aggregation of mitochondrial filaments. The tendency of the fibrils to concentrate on attachment points, or thickenings of the basal plasma membrane, is noted. It is also observed that numerous mitochondria are located in the distal region of the cells of the outer layer of epidermis in association with the secretory vacuoles. Microvilli are seen occasionally on the free surface of the skin. Cisternae are found only in the cells of the outer epidermal layer, while vesicular endoplasmic reticulum is found in the cells of both epidermal layers.

Two kinds of "clear" cells in the human epidermis; with a report of a modified DOPA reaction for electron microscopy

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Chromaffin cells, mast cells and melanin. I. The granular cells of the skin

Sections of human skin obtained from a variety of sites and from subjects of different ages have been examined. Mast cells, melanocytes and melanophores have been identified by the use of various staining procedures, but the 'chromaffin cells' reported by Adams-Ray & Nordenstam (1956) and Burch & Phillips (1958) have not been observed. The staining reactions of pressor amine-containing chromaffin cells are reviewed and contrasted with those of the granular cells of the skin.