Immunostained sections and whole-mount preparations of the layers of the guinea pig jejunum were investigated by an improved peroxidase-antiperoxidase method using an antiserum to S-100 protein. A delicate latticework of S-100 protein immunopositive glial cells was demonstrated extending in the longitudinal muscle layer, myenteric or Auerbach's plexus, circular muscle layer including the deep muscular plexus, submucous layer including the submucous or Meissner's plexus, lamina muscularis mucosae and lamina propria mucosae. The whole enteric nerve plexuses consisted of two subsystems; nerve plexuses of the muscular coat and those of the submucous and mucous coats. These two subsystems were joined to each other by thick, connecting branches perforating the inner circular muscle layer. Extrinsic nerves entering the myenteric plexus formed a specialized junctional structure containing S-100 protein immunopositive glial cells, whereas those entering the submucous plexus ran along the submucous arteries. We proposed the term enteroglial cells to designate the S-100 protein immunopositive cells which ensheathed the somata and processes of the enteric neurons. The frameworks of all structures in the enteric nerve plexuses from the largest ganglia to the thinnest nerve fasciculi were constructed of these enteroglial cells.
A spectrum of the enteroglial cells was presented. Those in the myenteric and submucous ganglia were found similar to the astroglia of the central nervous system and to the satellite cells in the peripheral ganglia. Those in the primary and secondary fasciculi of the myenteric plexus formed a kind of neuropil together with the neuronal processes. Those in the tertiary fasciculi of the muscular coat formed the framework of the autonomic ground plexus. We tentatively concluded that the interstitial cells of Cajal contain an immunoreactivity for S-100 protein, and thus are glial in nature. The occurrence of specialized enteroglial cells with a neuron-like function was discussed in the autonomic ground plexus of the muscular coat. In the lamina propria mucosae, there was a fine latticework of the S-100 protein immunopositive enteroglial cells. This latticework corresponded to that of the interstitial cells of Cajal in the villous and periglandular plexuses.

View full abstract

Electron microscopy of a neuro-insular complex type II is described in the adult cat. A group of B-cells was recognized in the endoneurial space of a nerve provided with a continuous multi-layered perineurial sheath. The endocrine cells together with unmyelinated axons were enveloped by cytoplasmic processes of Schwann cells. A synaptic-like structure was occasionally noted on the surface of an endocrine cell. The neurotropism of endocrine cells (WATZKA, 1931) which leads to the formation of pancreatic neuro-insular complexes is compared with the neurotropism of Leydig cells and ovarial interstitial cells. It is suggested that such neuro-endocrine complexes generally communicate via vascular connections to the target organs or target tissues.

View full abstract

Leucocytes and thrombocytes in the chicken liver sinusoids were observed under normal conditions and after intravenous India ink perfusion. The monocytes exhibited conspicuous phagocytic activity. At 30min or earlier and 4hr after the perfusion, they ingested considerable amounts of the carbon particles, which were deposited in small vacuoles and/or lysosomes. In this study we revealed two transitional forms of the monocyte changing into the Kupffer cell. In one transitional form, which already at 15min after the perfusion stored considerable amounts of the particles, the ectoplasmic layer was partly differentiated and projected many pseudopodia into the sinusoid. At 48hr after the perfusion, the other transitional form was attached by its wide basal surface to the endothelial linig and projected well-developed pseudopodia into the sinusoid like the Kupffer cell without, however, storing the carbon particles. These findings are thought to suggest the transformation of the monocytes into the Kupffer cells. Thus we came to the assumption that the Kupffer cells might be replenished: 1) by self-proliferation; 2) by the macrophages from the hepatic Parenchyme into the sinusoid; or 3) by transformation from the monocytes circulating into the sinusoid (the “triple origin” as opposed to the “dual origin” of the Kupffer cell).
In the earliest stage after India ink perfusion, the thrombocytes exhibited the most striking reaction comparable to the Kupffer cells toward which they were assembled. The India ink particles were taken up into the “surface connected canalicular system” (SCS), which thickened and made vacuolar expansions as the amount of the particles was increased. At 4hr after perfusion, the particles disappeared from the majority of the thrombocytes, leaving an empty SCS. The India ink particle uptake and storage by the thrombocyte were thought to be temporary phenomena, different from the true phagocytosis of the macrophages.

View full abstract

Vomeronasal tissues from four male gnotobiotic calves were prepared for transmission and scanning electron microscopy. Features described include: non-myelinated nerves in the non-neurosensory lamina propria, capillaries in the base of the neurosensory epithelium, sustentacular cells with microvilli 22-26μm long, neurosensory cells with numerous apical vesicles, cells with cytoplasmic projections containing dense bundles of filaments, and brush cells. The structurally well developed bovine vomeronasal organ is similar in other respects to that reported for a number of other mammals

View full abstract

Immunoelectron microscopy using a colloidal gold-antibody method with anti-rat GH serum demonstrated three morphologically different types of GH cells in the rat anterior pituitary. They were distinguished as Types I, II and III GH cells, containing only large secretory granules about 350nm in diameter, mixed large and small granules, and only small granules about 150nm in diameter, respectively. Double gold labeling with large gold particles for GH and small particles for PRL or ACTH indicated that neither GH and PRL nor GH and ACTH were contained in the same cell.
In adult male rats, Type I cells (68%) predominated over Type II (22%), while Type III cells were rare (9.7%). On the contrary, in the adult female rats, Type II cells (47%) slightly dominated over Type I (44%) though the rate of Type III cells was the same as in the male. In neonatal infants, the frequency of occurrence of Type III cells was as high as about 20%; sex differences between Types I and II were indistinct. The Type III cells were therefore thought to represent an immature type.

View full abstract

The blood vascular bed of the rat carotid body was reproduced with methacrylate and observed under the scanning electron microscope. The carotid body received the proper carotid body artery from the common carotid body artery, which arose from the external carotid or occipital artery and gave off subsidiary branches to the tissues near the carotid body. The proper carotid body artery divided in the carotid body, ultimately breaking up into thick (main) or thin (subsidiary) arterial terminals to form the vascular plexus of the carotid body. This plexus contained both thick and thin capillaries. The thick capillaries arose from the thick and thin arterial terminals and formed the basic capillary network of the carotid body. The thin capillaries were only subsidiary, intercalated among the thick capillaries. A few accessory twigs of the proper carotid body artery passed through the carotid body and supplied the adipose and other tissues around the carotid body. Many venules arose from the thick capillaries of the carotid body and were collected into rostral and caudal efferent veins. These efferent veins received the veins from the tissues adjacent to the carotid body, and drained into the internal jugular vein. No arterio-venous anastomosis was found in, on or around the carotid body. The common carotid body artery and its subsidiary branches showed, at their origins, marked constrictions indicative of the arterial cushions, though the proper carotid body artery and its accessory twigs were not provided with such clear constrictions. These findings suggest that the inflow of blood into the common carotid body artery may be regulated by its constriction, especially of its arterial cushion, and that the subsidiary branches of the common carotid body artery and the accessory twigs of the proper carotid body artery may act as bypass-routes to eliminate the excessive inflow of blood into the carotid body. It is considered that the thin arterial terminals and thin capillaries may act as buffer channels to homogenize the blood flow within the carotid body.

View full abstract

Using injections of horseradish peroxidase (HRP) and the osmium-tannic acid method, megakaryocytic cells in the livers of rat embryos at 12-16 days of gestation were examined for the purpose of classification of the stages of formation of the platelet demarcation membrane. Megakaryoblasts were classified into the following three types according to the formation patterns of the demarcation membrane. 1) The P-type megakaryoblasts showed plate-like membrane invaginations in large localized areas at early stages. The invaginating membrane developed toward the periphery of the nucleus. 2) The L-type megakaryoblasts showed localized labyrinthine membrane invaginations but no definite direction in its development. 3) The T-type megakaryoblasts had tubular invaginations at multiple sites on the plasma membrane. The P- and L-type cells were observed at 12 and 13 days of gestation. The T-type cells were found after the 14th day. In all the types of megakaryoblasts the membrane invagination occurred in the areas making contact with hepatocytes. It was agreed that the cells of the megakaryocytic series in which the demarcation membrane developed contrary to the basic pattern were ordinary promegakaryocytes. The megakaryocytes forming networks of the demarcation membrane dividing into platelet areas were small in cell size. Examination of the patterns of formation of the demarcation membrane proved useful for classifying the megakaryocytic series at each stage of maturation.

View full abstract