The distribution and ultrastructure of the class II major histocompatibility complex (MHC) antigen-expressing cells in the pulp tissue of human deciduous teeth during the process of physiological root resorption was surveyed by histochemical and immunocytochemical methods using an anti-human leukocyte antigen (HLA)-DR-monoclonal antibody. Dental pulp was found to contain numerous HLA-DR-positive cells of various shapes; those showing a dendritic appearance were located mainly in the periphery of the pulp tissue, associated closely with the odontoblasts. The immunopositive cells sometimes extended their cytoplasmic processes into the dentinal tubules and increased in number in the areas affected by dental caries, attrition or restorative procedures, implicating their role in immunosurveillance.
The immunopositive cells were located consistently at the pulp-dentin border during the stage of active resorption, adjacent to the preodontoclasts or odontoclasts, and covered the exposed dentin surface after the detachment of the odontoclasts until the onset of cementum formation. These data suggest that the HLA-DR-immunopositive cells in the coronal pulp of human deciduous teeth play an inductive role in the differentiation, migration and/or activation of the odontoclasts and cementoblast-like cells during the stages of tooth resorption.

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Vascular endothelial growth factor (VEGF) is a secreted polypeptide with specific effects on endothelial cell growth and vascular permeability. While previous studies have focused on the expression of VEGF associated with angiogenesis in tumor and embryonal tissues, little is known about the role of VEGF in normal adult tissues. In the present study, a specific antibody was used to study the immunohistochemical localization of VEGF in the entire body of normal adult rats. Intense to moderate immunoreactivities for VEGF were detected in some endocrine cell types, namely, the parafollicular cell of thyroid gland, B cell of endocrine pancreas, N cell of adrenal medulla and a minority of the thyrotrophs of the pituitary gland. A certain exocrine cell type, i. e., the surface mucous cell of stomach, was also immunoreactive for VEGF. At the ultrastructural level, VEGF immunoreactivity was localized exclusively in the secretory granules of all immunopositive endocrine and exocrine cells examined. The present study provided immunohistochemical evidence for the occurrence of VEGF in subsets of endocrine and exocrine cells of normal adult rats, suggesting that these secretory cells regulate local vascular permeability through a paracrine action of VEGF.

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Changes in the three-dimensional structures of the myoepithelium of the dilator pupillae (MDP) during mydriasis and miosis were investigated in the rat by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Following fixation, SEM specimens were treated with sodium hydroxide to expose the muscle surface. Significant morphological differences were noted in the anterior surface of the MDP between mydriasis and miosis. In the mydriatic eye, a highly rugged structure with numerous linear folds was oriented circularly or obliquely together with spherical bulges. These structures, presumably corresponding to the highly contractile portion of the myoepithelial cells, were more prominent near the pupillary margin than near the ciliary margin, indicating that the MDP may contract much more strongly in the pupillary margin. In the miotic eye, the anterior surface of the MDP showed less conspicuous linear folds in the pupillary area, and was almost flat in the ciliary area. Radially oriented ridges were observed only in the pupillary area. These findings suggest that the contraction of the sphincter pupillae in miosis induces a stretching of the MDP toward the pupil and a circular shrinkage of the MDP. Ultrastructural changes of the MDP particularly near the pupillary margin may play an important role in regulation of the pupil diameter as a diaphragm of the eye because morphological changes such as the linear folds, spherical bulges, and ridges were more prominent near the pupillary margin than those near the ciliary margin.

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The tongue in four species of penguin was investigated by light microscopy and by scanning electron microscopy, with special reference to the lingual papillae.
1) The middle of the penguin tongue contains a pair of long cartilages and long tendons accompanied by striated muscle bundles.
2) Large, spine-like, and caudally directed lingual papillae (filiform-like papillae) densely cover the dorsal surface of the tongue, apparently serving to catch fishes.
3) By light microscopy, the dorsal lingual epithelium with the lingual papillae are seen as a thick cornified layer, but the lateral and lower surfaces have a thinner cornified layer.
4) The connective tissue core (CTC) under the epithelium of the lingual papilla shows a stereo structure similar to but smaller than the external form of the papilla. The CTC contains some blood vessels and nerve fibers; the lingual glands are found in the submucous layer only in the posterior tongue.
5) Bundles of nerve fibers in the lamina propria of the tongue were immunohistochemically positive for PGP 9.5, and it appeared that Merkel corpuscles were distributed in the connective tissue closely beneath the epithelium of the finger-like papillae, though they were only weakly immunoreactive for PGP 9.5.
6) Numerous fine filaments of elastic fibers are found closely beneath the epithelial cell layer of the dorsal surface of the tongue including the lingual papillae, while there are very few of them on the lateral and lower sides of the tongue.

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When stomachs are stimulated to secrete acid, the intracellular canaliculi of the parietal cell increase and there is a concomitant depletion of the cytoplasmic tubulovesicular system. This change is believed to occur through the transformation of tubulovesicular membranes into intracellular canaliculi. This study was undertaken to examine the distribution of the cytoskeletons in rat gastric parietal cells during this process. In the resting parietal cells, actin filaments decorated with heavy meromyosin (HMM) were found in the cores of microvilli, extending from the apex of microvilli into the pericanalicular cytoplasm and forming radial networks. In some cases, these actin filaments were also associated with the tubulovesicles. Moreover, tubulovesicular membranes were rare in the 300nm zone around intracellular canaliculi but numerous actin filaments were seen in this region. Soon after stimulation of the parietal cells by gastrin, tubulovesicles were closely associated with the intracellular canaliculi, while actin filaments networks adjacent to the canaliculi diminished and their labeling with HMM seemed less orderly. By immunocytochemistry, immunogold partiles iudicating ezrin were associated with microvillous membranes in the resting as well as stimulated parietal cells but were absent on the tubulovesicular membranes. When intermediate filaments were immunocytochemically investigated using anticytokeratin immunogold particles clearly labeled filamentous bundles present around the intracellular canaliculi, perinuclear spaces and under the basolateral cell membrane. Their localization was not changed after stimulation. These results suggest that actin filaments in the cytoplasm around the intracellular canaliculi may play a key role in the translocation of the tubulovesicles toward the intracellular canaliculi during the acid secreting process.

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Using the force modulation mode in atomic force microscopy, we measured elastic properties of living mouse fibroblasts (NIH3T3) in a culture medium. The topographic images of the cellular surface and the corresponding elastic images of the cellular surface were able to be captured simultaneously with high spatial resolution. The consecutive images were useful for examining time-dependent changes in the cellular surface. We observed that some cells continued to shrink and change their softness for 2 hours. Then the force modulation mode in atomic force microscopy shows potential use in analyzing time-dependent regional elastic properties of living cells with high spatial resolution.

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The topographic relationship between the lymphatic network and the nerve plexus in the myenteric layer of the monkey jejunum was studied by an enzymehistochemical method. Identification of the lymphatics was achieved by a 5′-nucleotidase staining method, and the enteric neural components were visualized by acetylcholinesterase staining. A well-developed lymphatic network and a dense nerve plexus were demonstrated throughout the myenteric layer. Numerous segments of the initial lymphatics, with their blind endings at the apical parts, tended to gather toward the ganglion and run along the primary nerve strands. Elements of the tissue interstitium separated the lymphatics from the enteric nerves. Nerve terminals were often located closely beneath the endothelium of the initial lymphatics and were exposed to the subendothelial tissue on the side facing the abluminal surface of the lymphatic endothelium. These findings suggest that the lymph flow in the initial lymphatics might be regulated by the enteric nervous system, and that the transport of tissue fluid by the lymphatics might serve as a suitable microenvironment for the enteric nerves.

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An organ culture study was carried out to examine the effects of adrenal corticosteroids on the development of growth hormone (GH) cells and prolactin (PRL) cells. The adenohypophysial primordia were separated from 13.5-day-old fetal rats and maintained in vitro for 8 days with or without cortisol. Immunohistochemical examination of these explants showed that cortisol stimulated the differentiation of GH cells but suppressed that of PRL cells in a dosedependent manner. In the absence of cortisol there were more PRL cells. Corticosterone had a similar effect on the developing adenohypophysis. When the pituitary primordia of Day 16.5 were cultured for 5 days and studied by the in situ hybridization technique, the expression of GH and PRL mRNA was found to be parallel with the immunoreactivity of the respective hormones. These data are discussed in relation to the normal development of GH and PRL cells in the fetal rat adenohypophysis.

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Noxious chemical stimulation of the rat nasal mucosa with mustard oil induces the expression of Fos-like immunoreactivity in trigeminal and other brain stem neurons which contribute to upper airway protective reflexes such as sneezing, coughing and apnea. To examine the role of nociceptive processing in the upper cervical spinal cord, we investigated the Fos-like immunoreactivity of the brainstem and upper cervical spinal cord following the injection of mustard oil (10μl of 10%) into the nasal mucosa of pentobarbital anesthetized rats. Two hours after the application of mustard oil, numerous Fos-immunoreactive neurons were found in the mediolateral end of the C1 and dorsolateral division of the C2. The mean numbers of the Fos-immunoreactive neurons in the laminae I and II of the ipsilateral first and second spinal segments were significantly greater than in the control (vehicle treated) rats. There were no significant differences in the mean number of Fos-immunoreactive neurons in the contralateral C1 between the mustard oil and vehicletreated rats. These results suggest that the C1-C2 dorsal horn neurons process the nociceptive information from nasal mucosa as well as other areas innervated by the trigeminal nerves, and that ethmoidal nerves may contribute to the exclusive conveyance of nociceptive information.

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The postnatal morphodifferentiation of muscle fiber ends at the myotendinous junction was examined by scanning electron microscopy in gastrocnemius muscles of the Chinese hamster. Muscle fiber ends during the first week were simply conical or slightly complex, having a few pit-like invaginations and longitudinal and narrow clefts. By the second week, fiber ends gradually became complicated with an increased number of clefts and finger-like processes. Pits and short clefts linearly arranged towards the fiber tip were visible until the second week. This possibly indicates the linear elongation of the clefts by the fusion of adjacent pits to one another and to preexisting clefts. By the fourth week, the fiber ends had almost fully matured and displayed numerous cytoplasmic processes and lateral grooves.

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