A comparative autoradiographic study on the uptake and intracellular localization of ³H-leucine-, ³H-dopa-, ³H-dopamine- and ³H-ATP-derived radioactivity was performed in the mouse carotid body to investigate the metabolic features of the chief cell as a paraneuron.
³H-leucine-derived radioactivity representing recently synthesized peptides was demonstrated in all kinds of cells in the carotid body and surrounding area. The chief cell was less radioactive than the nerve cell in the superior cervical ganglion. In the electron microscope autoradiography, no accumulation of radioactivity could be demonstrated either in the Golgi area of the chief cell, where the membrane-bound particles were probably formed, nor in the periphery of the cell, where they were stored before their release.
Incorporation of ³H-dopa-derived radioactivity representing recently synthesized catecholamines was specific to the chief cell, mast cell, and nerve cell in the superior cervical ganglion. In the chief cell the distribution of radioactivity was roughly identical with that of the large dense-cored vesicles.
Striking accumulations of ³H-dopamine-derived radioactivity were demonstrated in the adrenergic nerve terminals in the perivascular space and the glomus complexes of the carotid body. Not all of the chief cells incorporated the ³H-dopamine-derived radioactivity.
³H-ATP-derived radioactivity was demonstrated in all kinds of cells in the carotid body and surrounding tissues. In the chief cell, as in other kinds of cells, the highest radioactivity was seen in the nucleus.
The present results suggest that, if the large dense-cored vesicles and/or small synaptic vesicles in the chief cell, like those membrane-bound particles in other paraneurons, contain peptides, monoamines and ATP, the turnover of these products as secretory materials is much slower in this cell than in such endocrine paraneurons as adrenal chromaffin cells and gut endocrine cells.

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By applying at the ultrastructural level the silver methenamine impregnation method to glutaraldehyde-osmium fixed pancreatic tissue of Snell-Bagg mice it was found that two islet cell types show deposition of reduced silver on their secretory granules: B cells and another cell type. Histochemical analyses indicate that very likely the osmium dependent argentaffinity is due to S-S groups. After alkaline treatment the reactivity of B cells is lost, while that of the other cells remains unaffected. It is suggested that the third cell type stores the pancreatic somatostatin, an S-S containing polypeptide hormone.

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One thousand eight hundred and fifty-six specimens of replicated rat renal glomerulus were examined under the scanning electron microscope, and an extremely rare anomaly of the glomerulus with double afferent arterioles was described.
The double afferent arterioles arose separately from a terminal twig of the interlobular artery and reached the vascular pole of a subcapsular glomerulus which possessed a single efferent arteriole. Microdissection revealed that this glomerulus was composed of three fairly independent lobules of anastomosing capillaries. Microdissection also revealed that the double afferent arterioles were isolated from each other even in the glomerulus; the one supplied two lobules, while the other the third one only.

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By means of the freeze-fracture technique, the membrane specialization of the cochlear hair cell of guinea pigs was studied. Periodically aggregated particles were revealed on the PF face of the plasma membrane of the outer hair cell. The particles were around 12nm in diameter and 10 to 17nm in center-to-center spacing. Their arragement was hexagonal, orthogonal or parallel. Possible involvement of this structure in the electrical excitability of the membrane was discussed.

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Laryngeal glands of adult cats were observed by scanning electron microscopy. Intercellular secretory canaliculi in the gland were an arborized system of capillaries extended among acinar cells, and their stem or collecting canaliculus opened to the gland lumen. The inner surface of the canaliculi was provided with small globular microvilli. The canaliculi in the laryngeal gland resembled the hepatic bile capillaries in lower vertebrates.

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Ultrastructural and cytochemical studies on developing tendon-bone joints (fibrocartilage) of rats indicated that the initial calcification loci were, as in some other calcifying tissues, matrix vesicles. These membrane-bounded vesicular structures were concentrated in the spaces between the longitudinal cell columns of the fibrocartilage.
Where calcification was going to start, the vesicles became denser and more osmiophilic in appearance. The first identifiable needles of apatite crystals were deposited in and close to the matrix vesicles. Where calcification was more extensive and crystals radiating from each calcification center formed a calcified spherule, the matrix vesicles were no longer visible in the spherule. No ultrastructural relation between collagen fibrils and the initial deposits of minerals was noticed at the site of the initial calcification.
Alkaline phosphatase activity was demonstrated in the matrix vesicles as well as in the plasma membrane of fibrocartilage cells, most intensely at the initiating site of calcification.
Following potassium pyroantimonate fixation to produce electron opaque deposits of calcium, the deposits were located mainly in the mitochondria and plasma membrane of fibrocartilage cells as well as in matrix vesicles. The closer to the initial site of calcification, the stronger the cells and vesicles reacted. In the area where calcification was in progress, however, calcium was gradually lost from the cell and reversely accumulated in the matrix vesicles.
The ultrastructural and cytochemical findings from this study suggested that they were of cellular origin and liberated into the matrix from cells, partly by way of budding- off and partly by cell disintegration. The possible roles of matrix vesicles at the initiating sites of calcification in fibrocartilage were discussed.

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Human permanent teeth without caries, obtained from 10-16 year old males and females and noncarious human deciduous teeth in which roots remained intact or were only poorly resorbed, were studied histologically. The distribution of sensory nerves in deciduous teeth were compared with that in permanent teeth by means of the silver-nitrate technique.
1. In radicular pulp, the sensory nerve fiber bundles accompany blood vessels in the axial area and several nerve single-fibers occur in the peripheral area of the pulp.
2. The subodontoblastic nerve plexus is formed in or beneath the cell-rich zone of the coronal pulp, and further, the marginal nerve plexus is built up near the pulpo-predentinal border.
3. The nerve fibers entering the predentin can be classified into 3 types by their courses. In the first type, nerve fibers pass directly toward the calcification front along the dentinal tubules in the predentin. In the second type, nerve fibers run obliquely or transversely in the predentin. The transversal fibers form a plexus-like structure by dividing and interlacing at various levels of predentin. The third type nerve fibers pass along the dentinal tubules in the predentin and, after reaching the predentino-dentinal border, reverse the odontoblast layer, thus forming a looped course.
4. There is no essential difference between the nerve supply in the deciduous and in the permanent teeth, but the nerves in the deciduous teeth are less dense in distribution and lower in amount than in the permanent teeth. Moreover, a typical marginal nerve plexus, which occurs constantly in the permanent teeth, is only occasionally found in the deciduous teeth; and no nerve fiber was observed to penetrate into the calcified dentin in the deciduous teeth. This finding seems to account for the fact that the deciduous teeth are less sensitive than their permanent successors.

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