Electron microscopic observations on the secretory granules of the adrenal medulla of domestic fowl

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An electron microscopic observation has been made on the secretory granules of the adrenal medullary cell of 2-5 day-old male chicks. Small pieces of the adrenal gland were fixed for one hour in phosphate buffered 1% osmium tetroxide. After dehydrating by alcohol, the tissues were embedded in epoxy-resin by LUFT's method. Sections, cut with the PORTER-BLUM type ultramicrotome, were examined with JEM-4A or HU-11A type electron microscope.1. The adrenal medullary cells of the chick were classified into two types. The first type cell contains many spherical secretory granules in its cytoplasm (Figs. 1-12), and the second type has the granules of irregular shape.2. The spherical granule consists of a spherical osmiophilic deposit in the center, a light halo around it and of a surrounding limiting membrane (Figs. 3-11).The osmiophilic portion which is a dense mass of abundant fine grains is mostly situated in the center of the limiting membrane. However, in or near the GOLGI field, the osmiophlic deposit is not always in the center of the limiting membrane, but is situated eccentrically. This might be a young granule made in the GOLGI vesicle.The limiting membrane, of 50Å in thickness, consisting of two dense layers and a single light layer of 20-30Å between them, corresponds to a unit membrane of ROBERTSON.3. The granule of irregular-shape consists also of a osmiophilic deposit, a white halo around it and of a surrounding limiting membrane. The limiting membrane same as that of the spherical granule in the structure, is also a unit membrane. The osmiophile portion, which is situated eccentrically in the limiting membrane, is also a dense mass consisting of very fine osmiophile grains.4. Sometimes the limiting membrane of the granule contacts with the cell membrane at one point (Fig. 11). By the opening of this contact point, the internal substance of the granule might be excreted into the intercellular or perisinusoidal spaces.5. In the medullary cells of both types, sometimes smooth surfaced large vacuoles of unit membrane are found except in the GOLGI field (Figs. 7 and 17). Sometimes we notice the inclusion as shown in Fig. 10 in the first type of medullary cell.