This study was designed to gain insight into the underlying mechanisms of the centripetal migration of developing LHRH neurons. The medial wall of the nasal pit (NAP) of 12.5-day-old rat embryos (E12.5) was cultured singly or together with the E12.5 medial-basal wall of the forebrain vesicles (mFV) or with the E14.5 median eminence-arcuate complex (ME-Arc). Further, the NAP was cultured with the mFV and ME-Arc or with the mFV and nasal mesenchyme (NM), which lay between the mFV and the NAP, of E12.5 embryos (triple culture). The NAP gave rise first to fibers labeled with anti-neural cell adhesion molecules (NCAM) and then to LHRH neurons. In co-cultures, NAP-and brainderived NCAM fibers connected the NAP and brain cultures, and frequently linked with each other to form knots at the periphery. LHRH neurons migrating along the NAP-derived fibers directly or indirectly entered brain cultures. In the latter case, the cells strayed along the way from the NAP-derived fibers to the brainderived fibers at the knots and migrated retrogradely along the latter fibers to enter into the brain tissues; this occurred most frequently into the E14.5 ME-Arc. In triple cultures, abundant NCAM fibers emerging from the NAP were only found when the NM lay between the NAP and mFV; the fibers converged further to the mFV. These findings help elucidate the mechanisms underlying the centripetal LHRH cell migration from the NAP to the hypothalamus.

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Although intercellular junctions have been described between mature lamellar bone cells, little has been known about junctions between osteoblasts in early developing bone. We therefore conducted a freezefracture and ultrathin section study on developing calvaria of rat embryos aged 17-19 days to determine what types of intercellular junctions appear between osteoblasts in early osteogenesis. We observed that three main types of junctional structures, i. e., adherens of the macular type, gap, and focal tight junctions, coexist between osteoblasts in early developing bone. Their possible involvement in early morphogenetic events is discussed. Tight junctions are considered to be involved in compartmentalization of the early matrix and final polarization of osteoblasts.

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The muscle coat of the lower region of the mouse oviduct undergoes morphological changes during pregnancy and post-partum. Ultrastructural examination and morphometrical findings show that, during pregnancy, the smooth muscle cells undergo a significant increase in both the number of mitochondria and caveolae and in the extension of the rough endoplasmic reticulum and Golgi apparatus, suggesting an enhancement of metabolic activities, especially protein synthesis. Within two days after delivery, the number of mitochondria and caveolae is similar to that of non-pregnant mice, whereas the extension of the rough endoplasmic reticulum and Golgi apparatus further increases significantly. The cytological signs of enhanced protein synthesis in the smooth muscle cells of the lower oviduct during pregnancy and, especially, in the post-partum period are probably related to a remodelling of the intercellular connective tissue matrix.

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The distribution of human intestinal 15kDa protein (I-15P), a new fatty acid-binding protein (FABP), was observed in normal tissues using immunohistochemical techniques. The antiserum against human I-15P intensely reacted with the villous epithelium of the terminal ileum but not with the enterocytes of the crypts. Although the surface epithelium of the stomach and villous epithelium of the duodenum showed weak reactivities, the epithelial cells of the jejunum, proximal ileum, colon and rectum, and also glandular epithelia with intestinal metaplasia of the stomach were not immunostained. The other human tissues examined were negative for anti-human I-15P antibody. Human I-15P thus represents a distinctive, confined tissue distribution different from the other FABPs and is expected to serve as a useful cellular marker of terminal ileal enterocytes.

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Analysis of serial ultrathin sections of the human aortic intima detected a new cell yet to be described in the literature. These cells, which we have designated Vascular Dendritic Cells, appeared in contact with each other and with other intimal cells. Vascular dendritic cells are characterised by ultrastructural features similar to those of dendritic cells, including a well developed smooth endoplasmic reticulum and the presence of several processes which were 3-5 or more times in excess of the size of the cell body. In areas of the normal aorta resistant to atherosclerosis, vascular dendritic cells were mainly localised in the subendothelial layer where they contacted both endothelial cells and smooth muscle cells. In areas of the normal aorta predisposed to atherosclerosis, vascular dendritic cells were distributed throughout the intima and the cellular interactions were altered with the vascular dendritic cells, developing multiple contacts with monocyte/macrophages and lymphocyte-like cells. Aortic areas predisposed to atherosclerosis showed the destruction of some vascular dendritic cell processes where they apposed endothelial cells.
We speculate that vascular dendritic cells (VDCs) are a variety of dendritic cell and are involved in the maintenance of homeostasis in normal arterial intima. Vascular dendritic cells may be important in the development of atherosclerotic lesions, possibly through an immune mechanism.

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We studied the immunohistochemical localization of CD44 and heparan sulfate (HS) chains in rat enamel organ by confocal laser scanning microscopy and transmission electron microscopy. We also investigated the binding sites of basic fibroblast growth factor (bFGF), one of the heparin-binding growth factors (HBGF), on Microslicer-sections to clarify its role in the cell-cell interaction of HS.
At the differentiation stage of ameloblasts, weak immunoreactivity for CD44 was detected on the plasma membrane of the inner enamel epithelium, external enamel epithelium and the cells adjacent to the inner enamel epithelium. In accordance with the differentiation of preameloblasts into secretory ameloblasts, this immunoreactivity increased in stratum intermedium cells. At the secretory stage, stratum intermedium cells showed the most intense immunoreactivity in the enamel organ. At the maturation stage, strong immunoreactiviry was seen on papillary layer cells. On the other hand, the lateral plasma membrane of ruffleended (RA) and smooth-ended ameloblast (SA) showed weak reactivity. No immunoreactivity was detected on the ruffled border of RA and the distal plasma membrane of SA. Immunolocalization of HS chains was similar to that of CD44. The binding activity of bFGF was also intense on stratum intermedium cells and papillary layer cells.
These findings suggest that: 1) stratum intermedium cells and papillary layer cells express CD44 and HS chains in accordance with their differentiation; 2) HS chains on the plasma membrane of these cells may regulate calcium transport by their negative charge; and 3) HS chains on the stratum intermedium and papillary layer may play an important role in the differentiation and activity of ameloblasts by preserving HBGF.

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The postnatal development of Peyer's patches was investigated using routine histological and immunohistochemical techniques, focusing especially on the formation and increase in number of lymphoid follicles. In addition, we studied the influence on the development of lymphoid follicles in Peyer's patches of a sublethal dose of whole-body X-irradiation at an earlier postnatal age. At 1 day after birth, surface-IgM (sIgM)-bearing cells (B lymphocytes) were scattered throughout the Peyer's patch. At Day 3, sIgM-bearing cells had accumulated to form primary follicles in association with domed elevations. OX2-positive reticular cells (FDC) were detected in the centers of primary follicles at Day 5. The first appearance of germinal centers within lymphoid follicles was noted at 18 days, and at 21 days almost every follicle contained a germinal center. At Day 5, each Peyer's patch contained 6-8 lymphoid follicles, with the lymphoid follicles subsequently increasing in size and number. The mean number of follicles per Peyer's patch became 11.1, the adult level, at 21 days, and remained at this level for the next 15 weeks, even though respective follicles continued to enlarge during the observation period.
Three-week-old rats received 400rad whole-body X-irradiation. At 3 and 7 days after treatment, lymphocytes were largely depleted from Peyer's patches, leaving behind the structural framework of the lymphoid follicles, interfollicular zones and domes. Stromal cells in the follicle remnants retained a positive reaction to OX2. By 14 days after X-irradiation, lymphoid follicles together with their germinal centers had begun to repopulate, and the number of restored lymphoid follicles per Peyer's patch was comparable to that in non-irradiated 3-week-old rats.
In conclusion, the present results show that the majority of lymphoid follicles and their stromata are well established in Peyer's patches during the first 3 weeks after birth and are maintained for weeks and even months.

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The spatial distribution of dendritic cells, macrophages, and their respective precursor cells in the periodontal ligament of rat molars was examined by means of ACPase enzyme histochemistry and immunohistochemistry. Intense reactions for ACPase were localized in both the multinucleated-and mononucleated cells of the periodontal ligament located exclusively in the portions of physiological bone resorption due to the physiological migration of the molar teeth. Immunohistochemical staining with OX6-monoclonal antibody that recognizes antigen-presenting cells such as dendritic cells and macrophages revealed the localization of immunopositive cells predominantly in the portions of the periodontal ligament that showed only trace reactions for ACPase. On the other hand, a large number of ED1immunopositive cells, comprising a broad spectrum of cells of monocyte origin including dendritic cells and osteoclasts, displayed an almost even distribution throughout the periodontal ligament. Our current study is the first to show clear-cut in vivo morphological evidence that the cells of the bone-resorting, osteoclastic cell lineage and those of the non-bone resorbing, macrophagic and/or dendritic cell lineages are exclusively localized in roughly the distal and proximal regions of the periodontal ligament of rat molars, respectively. An advantage is proposed for the use of the rat molar periodontal ligament as an in vivo model system for pursuing differentiation pathways of cells of the monocyte lineage, particularly of the osteoclastic cells.

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The human visual cortex, especially its ganglionic lamina, was found to contain many neurons with perineuronal sulfated proteoglycans which were stained with cationic iron colloid and aldehyde fuchsin. It also contained many neurons with surface glycoproteins labeled with lectin Vicia villosa agglutinin (VVA) or Glycine max agglutinin (SBA). Double staining frequently showed that the neurons stained with cationic iron colloid were not labeled with lectin VVA or SBA. Hyaluronidase and chondroitinase ABC/heparitinase/keratanase digestions eliminated the perineuronal cationic iron colloid reaction, but never interfered with the cell surface lectin labeling. These findings indicate that the cell surface glycoproteins reactive to lectin VVA or SBA are neither structural elements nor adhesive molecules of the proteoglycans. Double staining further demonstrated that in some neurons with perineuronal sulfated proteoglycans, the cytoplasm was labeled with lectin Arachis hypogaea agglutinin (PNA). It was further noticed that the lectin VVA-labeled neurons were not always identical with the neurons labeled with lectin SBA or with lectin PNA.

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The pancreatic duct from the splenic lobe, the largest lobe of the pancreas in the mouse, was ligated at 6 weeks of age, with histological and cytological changes in the organ examined 1 day to 16 weeks after the ligation. Changes in the volumes of the pancreatic lobe, exocrine tissue, and interstitial tissue as well as relative total numbers of each cellular element in the organ after duct ligation were stereologically obtained using serial sections of the whole pancreas. Cell sizes, degenerated cell and mitotic cell indices, and nuclear densities of the acinar and ductal cells were also obtained.
After duct ligation, the volume of the pancreas increased by interstitial edema in the first 2 days but rapidly decreased thereafter due to atrophy of the exocrine tissue, amounting to 10% or less of normal volume by 7 days. The acinar cells showed an accumulation of the zymogen granules, cytoplasmic condensation and a pyknotic figure of the nucleus; they then were thoroughly deleted with appearance of numerous macrophages. This cell death was suggested to be due to apoptosis.
On the other hand, the ductal cells remained in the atrophic pancreas and proliferated with mitotic figures to two times the normal frequency at 3 days, and then formed duct-like structures lacking in the acinar cells. After 2 week, the ductal cells slowly decreased in number also due to cell death, but the pancreas became gradually enlarged by intralobular fatty replacement, to reach a volume approximating that of normal 8 weeks after duct ligation.
The stereological method serves for the correct evaluation of cell dynamics including the deletion and proliferation of the cells in the whole organ.

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A modification of azan staining (HEIDENHAIN, 1915) for a better differential demonstration than previously of adenohypophyseal cells is reported. Human hypophyses were fixed in Bouin's solution, washed in 70% alcohol, dehydrated and then embedded in paraffin. Sections of about 5μm thickness were cut and mounted on albumin-coated glass slides.
These sections were gently oxidized with a mixture of potassium permanganate and sulphuric acid, and then stained according to the original azan technique; thereafter a procedure of staining with aniline blue was added.
With this improvement, human adenohypophyseal cells were clearly classified into six groups on the basis of the color and intensity of staining of the cytoplasm. The α-acidophilic cells were stained clear red with azocarmine and the ε-acidophilic cells, orange-red with orange G, respectively. With aniline blue, β-basophilic cells stained a deep blue, while δ-basophilic cells were more weakly stained. The γ-chromophobic cells were faintly stained red, and the ACTH-cells very faintly blue. Collagenous fibers developed a blue color, while erythrocytes were orange-red to red.
This modified method produces much better results in differential staining of the adenohypophyseal cells than either the original azan or Masson-Goldner staining methods.

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