Antisera raised against neuron specific enolase (NSE), substance P, vasoactive intestinal peptide (VIP) and tyrosine hydroxylase (TH) were used to reveal nerve fibres in the wall of the canine small and large intestine. The circular muscle of the colon was innervated by nerve fibre bundles that ran parallel to the muscle throughout its thickness. A plexus of fibre bundles was found against the inner (submucosal) surface of the circular muscle. Fibres with substance P, VIP and TH immunoreactivity all contributed to this innervation. The circular muscle of the small intestine was distinctly separated into outer and inner layers by a dense plexus of nerve fibres, the deep muscular plexus. The outer and inner circular muscle were innervated by substance P, VIP and TH fibres. Extrinsic denervation through the severing of nerve fibres in the mesentery caused TH fibres in the intestine to degenerate, but had no detectable effect on the fibres with substance P or VIP immunoreactivity. Myectomy (the removal of the myenteric plexus from the full circumference of the intestine over a distance of 2-3cm), performed 7-13 days before tissue was taken, resulted in an almost complete loss of substance P fibres from the circular muscle of the colon and the outer circular muscle of the small intestine. However, many fibres persisted in the deep muscular plexus of the small intestine, and most fibres remained in its inner circular muscle. The changes in distribution of VIP fibres were almost identical, except that a small proportion of reactive fibres remained in the circular muscle of the colon and the outer circular muscle of the small intestine. It is concluded that the circular muscle layers of the small intestine and colon have dual sources of intrinsic nerve supply: the myenteric ganglia supply fibres primarily to the outer part of the muscle and the submucous ganglia supply fibres to the inner muscle.
The present study further demonstrated that VIP fibres ran anally in the myenteric plexus of both the small and large intestine, whereas substance P fibres ran orally in the large intestine and both orally and anally in the small intestine. The innervation of the muscularis mucosae and mucosa by substance P and VIP fibres was not affected by myectomy or extrinsic denervation, and these structures are therefore likely to be innervated by nerve cells in the submucous ganglia.

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Using the histochemical method for the demonstration of NADPH-diaphorase activity, the pineal organ of the frog and rat was investigated in serial sections. A positive NADPH-diaphorase activity was demonstrated in pinealocytes and nerve cells in the pineal organ of the frog, but not in the rat. An intense activity existed in the apical portion of the photosensitive pinealocytes of the frog. Large NADPH-diaphorase positive nerve cells (15-20μm in diameter) were located within the parenchyma of the pineal organ in the frog. Large NADPH-positive nerve cells were more numerous in the rostral than in the caudal portion of the organ, but the intensely stained cells, counting 25-35 in number, showed almost equal distribution and number in the ventral and the dorsal aspect of the pineal organ. In their staining ability, NADPH-diaphorase positive pineal nerve cells resembled retinal amacrine cells.
The results in the pineal organ of the frog are discussed in light of previous morphological findings using the acetylcholinesterase reaction, and with electrophysiological results.

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A ganglionated nerve plexus (GNP) found in the nasal vestibular mucosa of the adult musk shrew, and most likely belonging to the nervus terminalis, was studied by electron microscopy. The GNP, which contained ganglion cells and both myelinated and unmyelinated nerve fibers, was located in the subepithelial layer of the mesial vestibular mucosa of the snout processes. The ganglion cells were characterized by an eccentrically located round nucleus, dispersed mitochondria and Golgi apparatuses, and many small vesicles. Nissl bodies were rare. The ganglion cells, solitary or in a small group, were entirely covered with satellite cell sheaths. Semiserial sections suggested that a given ganglion cell directly extends one nerve process and plural modified cilia. There were no synaptic contacts between the ganglion cells and efferent nerve elements. On the other hand, it was seen that the epithelium overlying the GNP contained many nerve terminals which probably originated from the GNP. It is suggested that the ganglion cells in the nasal vestibular GNP of the musk shrew represent primary sensory neurons.

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The embryonic development of the salivary gland in the mouse was studied by scanning electron microscope (SEM). The submandibular morphogenesis was found to take place within its associated mesenchymal tissue. This stromal mesenchymal element has prevented us from observing three-dimensional details of the branching morphogenesis by SEM. In the present study, we applied a modified Evan's enzymatic digestion method to the embryonic submandibular gland.
Consequently, we obtained important information about the morphogenetic events for the branching development of the mouse submandibular gland, demonstrating that a pit and shallow clefts are formed on the lateral aspect of the spherical end bud. This pit and cleft formation likely represents the initial morphogenetic movement of the epithelium that establishes primary branchings. Furthermore, SEM observation of the basal surface of the embryonic epithelial cells provided us views of the developmental change of cell projections probably involving epithelial-mesenchymal contacts.

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Light and electron microscopic examination of the muscle coat of the mouse oviduct reveals differences in various regions concerning both the architectural pattern and cytological features of the smooth muscle cells. A network with large meshes made up of thin smooth muscle cells with unusual features, characterizes the infundibulum and upper ampulla. In the lower ampulla and isthmus these cells gradually stratify into two distinct muscle layers and acquire the typical characteristics of smooth muscle cells. In the uterotubal junction, the smooth muscle cells show a structure quite similar to that of myometrial cells. Exclusively at this level do cells of the circular layer form a ring at the opening of the oviduct into the uterine cavity. Independent of their location in one or the other region, the oviductal smooth muscle cells undergo striking changes during the estrous cycle. A substantial increase in organelle content, an enlargement in the extent of the contact area and the occurrence of myoblasts characterize proestrous and estrous. During metestrous all these features regress, until a picture typical of diestrous is reestablished. The peculiar structure of smooth muscle cells and their different arrangement in the upper oviductal region with respect to that in the lower one are in keeping with zonal differences in contractility of the oviductal wall and together with the striking cytological changes occurring during the estrous cycle, indicate their active involvement in reproductive processes.

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Histologic changes in the mouse epididymides were examined by light and electron microscopy 1, 3, 6 and 10 weeks after surgical fixation of the testes and epididymides to the internal abdominal wall at 2 months of age. In the epididymides subjected to the cryptorchid surgery, the principal cells in the segment next to the initial segment became taller, the nuclei were translocated to a higher position, and the widened infranuclear cytoplasm turned pale. The supranuclear cytoplasm showed a decrease in PAS stainability. Electron microscopy revealed that the infranuclear cytoplasm, which is occupied by small vesicular endoplasmic reticulum in the normal cells, was filled with distended rough endoplasmic reticulum. These changes first appeared one week after operation, further developing with time. Similar changes were observed when the epididymis was in the abdominal position with the testis in the scrotal position, or with the efferent duct ligated to block the testicular fluid flow into the epididymis. It is suggested that the epididymal changes recorded in this paper are induced by the elevation of temperature caused by the translocation from the scrotum to the abdomen.

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We found that when the midsection of Meckel's cartilage bars obtained from mice on the eighteenth day of gestation were grafted into isogenic mouse spleen, chondrocytes induced an endochondral calcification. Concurrent with the onset of calcification throughout Meckel's cartilage matrix, periodic banded thick collagen fibrils and matrix vesicles were observed around the chondrocytes.
Although most of the chondrocytes prior to grafting were hypertrophic cells, they survived for seven days in the splenic tissue and had well-developed secretory organelles. The cells which were surrounded by calcified matrix were relatively small, spherical, and showed a morphology closely resembling that of osteocytes.
These findings suggest that the life span of hypertrophic chondrocytes is influenced by the microenvironment of the spleen.

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We studied the metabolism of the conduction system and the working myocardium in diabetic rat hearts by enzyme histochemistry. The experiment was performed three weeks following the administration of streptozotocin (65mg/kg) to male Wistar rats. The hearts were quickly excised and tissue was frozen immediately by immersion in isopentane at -30°C and cut into 16μm thick sections in a cryostat. The PAS positive reaction was increased in the conduction system compared to the working myocardium in control rats. In diabetic rat hearts, these reactions in the working myocardium and the conduction system were strongly increased compared to control hearts. Several enzyme activities, such as phosphofructokinase, pyruvate dehydrogenase, glucose-6-phosphate dehydrogenase, Na-K ATPase, were reduced in both the working myocardium and conduction system of diabetic rat hearts. These results suggest that the changes in metabolic condition also exist in the conduction system of the diabetic rat hearts as well as the working myocardium.

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Light and transmission electron microscopic observations of the venom gland of the blue coral snake revealed a main venom gland and a long duct. The main secretory cell showed characteristic features of a protein secreting cell, with small microvilli, and a cytoplasm containing vacuoles and vesicles. Another type of “dark cell” and a third type of “basal cell” were also seen. “Nerve terminals” supplying the gland showed pleomorphic vesicles. The compressor muscle surrounding the venom gland showed the A band, Z disc, and H zone. Satellite cells were seen among muscle fibres. The neuromuscular junctions supplying the muscle showed clear vesicles. Scanning electron microscopy of the fangs showed the entrance lumen, discharge orifice, suture and the dental ridge. These findings are compared with relevant structures in other snake species.

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Intimal changes at the prelesional stage of atherosclerotic lesions were investigated ultrastructurally using hamsters fed a high cholesterol diet for 1 day to 1 month. Observations were restricted to the lesionprone area in the aortic arch. The endothelial cells began to show well-developed rough endoplasmic reticulum and Golgi apparatus after a few days of the cholesterol diet. After three days, macrophages which contained a few lipid droplets were observed just below the endothelium. We found that the intimal smooth muscle cell formed a gap junction with the process of the medial smooth muscle cell. After a few weeks to 1 month on the diet, the intima became markedly thickened and filled with dense extracellular matrices. The intimal smooth muscle cells showed well-developed rough endoplasmic reticulum and Golgi apparatus with immature granules, suggestive of high secretory activity. The present study showed that endothelial ultrastructural changes, macrophage invasion, and medial smooth muscle cell migration are very early events occurring within a few days after cholesterol intake commences.

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In order to examine the relationship between radial glial fibers and the migrating bipolar subependymal cells which are considered to be postmitotic precursors of granule cells in the rat olfactory bulb, the arrangement of radial glial fibers along the anterior lateral and olfactory ventricles was analysed by Golgi techniques, immunohistochemical demonstration of glial fibrillary acidic protein, and electron microscopy.
In rats during their first 3 weeks of life, the bipolar subependymal cells migrate along the anterior lateral and olfactory ventricles into the center of the olfactory bulb, whereas the radial glial fibers radiating from the ventricular surface are arranged rather perpendicularly to the direction of migration of bipolar cells. Hence radial glial fibers in this region are not considered to act as guides for the rostralwards migration of subependymal cells.

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This study was undertaken to determine the reaction of amputated dental pulp to the capping agent, α-tricalcium phosphate (αTCP), and to reveal the exact nature of the processes involved in both the healing of, and new hard tissue formation in the pulp when dressed with αTCP. The dental pulps of the anterior teeth of Macaca fuscata were dressed with αTCP ceramic 4-10 μm in diameter. The teeth were fixed by perfusion, then observed with light and electron microscopes. At 10 and 14 days postoperatively, the phagocytosis of the αTCP layer by the many macrophages and multinucleated giant cells, both of which had emerged beneath it, was seen. The synthesis of collagenous matrix underlying the αTCP layer began at 14 or 21 days, the cells involved exhibiting morphologic characteristics similar to those seen in osteoblasts. By the 90th day, only a bone-like hard tissue remained. No inflammation was observed in the residual dental pulp at any time during the experimental period. At 14 days, needle-like crystals were seen to have formed on the surface of αTCP particles, and by the 21st day, these crystals had extended to the newly synthesized matrix, with the result that calcification of the matrix was initiated, a calcified layer being superficially produced in the matrix. In the region of the matrix adjacent to the superficial calcified layer, a number of matrix vesicles were also found to function as another mechanism of matrix mineralization. Thus, it was concluded that the bone-like hard tissue was induced in the pulp capped with αTCP, and its potential for clinical application to exposed dental pulp was confirmed.

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