Tenotomized soleus muscles of adult rats were analyzed morphologically and biochemically with special reference to the recovery process. Light microscopic observations of semi-thin sections showed that the characteristic central core lesion was most extensive at 1 week after tenotomy and began to diminish in extent at 2 weeks until no trace of lesion could be seen by 6th week, as confirmed by thin-section electron microscopy. Three phases of changes in the cross-sectional area of muscle fibers after tenotomy were demonstrated by morphometry: phase I designated as the initial increase up to the 3rd day, phase II as the progressive decrease until the 4th week, and phase III as the recovery to normal or even hypertrophy. In electron microscopy, the earliest alteration of myofibrils was recognized at 3 days after tenotomy. The Z discs showed a wavy or zigzag profile with frequent longitudinal splitting of myofibrils. From the 2nd week on, muscle fibers underwent a process of recovery, replacing the central core lesion with new myofibrils in which a reassembly of thick filaments into bundles of thin filaments took place, with Z discs being aligned adjacent to the peripheral complete myofibrils. In SDS-polyacrylamide gel electrophoresis, the molar ratio of myosin to actin diminished markedly as the central core lesion developed and gradually returned to normal with time, correlating well with the loss and subsequent reassembly of thick filaments.

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This study aimed to clarify the effects of pinealectomy and sham-surgery on the area postrema (AP) by quantitative histological methods. Male, Wistar rats of normal (NO), sham-operated (SX), and pinealectomized (PX) groups were used in the late dark phase at 7 weeks of age. Consecutive frontal sections including the AP were stained with hematoxylin and eosin, and immunostained using PGP 9.5 for neurons, or GFAP or vimentin for glial cells. Consecutive sections of the AP were separated into five portions starting from the point of the central canal opening to the fourth ventricle in the caudal direction, and used for measurements. Mean cross-sectional areas of capillaries showed a lower value in the SX group than in the other two groups (vs NO, P<0.005; vs PX, P<0.03). In addition, the frequency distributions of the nuclear diameters of nerve cells showed different patterns among the three experimental groups (P<0.01), the frequency of large nuclei being higher in the SX group than in the other two groups. Possible mechanisms of the effects of sham-pinealectomy and pinealectomy and significance of the pineal-AP relation are discussed. The results of this study indicate that stuctural changes in the AP can be induced by intracranial surgery, suggesting certain pineal involvement in these changes.

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Tenascin-C (TN-C) is an astroglia-derived extracellular matrix protein that has been shown to be an early marker for astroglial precursors in the embryonic mouse brain. This study examined astroglial generation, migration, and differentiation in the developing mouse hippocampus by in situ hybridization histochemistry for TN-C mRNA. Special reference was given to the difference in the mode of astroglial development between the two cortical structures of the hippocampus: the dentate gyrus and Ammon’s horn. TN-C-positive cells were found in the ventricular germinative zone of the hippocampus as early as the 15th gestational day, and the labeled cells in the zone apposed to the fimbria migrated tangentially through the subpial area towards the forming dentate gyrus. The TN-C-positive cells aligned in the dentate gyrus exhibited the charac-teristic morphology of unipolar astrocytes as revealed by double labeling with glial fibrillary acidic protein (GFAP)-immunohistochemistry. On the other hand, the TN-C-positive cells ranging over a wide area of the ventricular germinative zone facing the forming Ammon’s horn migrated radially towards the cortex, with most of them aligned in the Ammon’s horn exhibiting a GFAP-positive stellate morphology. The onset of migration towards the dentate gyrus was two days earlier than that towards the Ammon’s horn. TN-C-positive cells in both cortical structures exhibited a DNA-replicating activity after settlement in the early postnatal stage and were considered to further generate astrocytes. On the other hand, TN-C-positive cells with DNA-replicating activity were also found in the subpial migratory stream moving towards the dentate gyrus and were considered to form the subpial matrix for the generation of the dentate astrocytes. Migratory TN-C-positive cells directed towards both the dentate gyrus and Ammon’s horn were apposed to radial glial processes and were believed to be guided by contact with these processes in a manner similar to migratory immature neurons. These findings indicate that TN-C-positive cells for the dentate gyrus and those for the Ammon’s horn have different migratory patterns and undergo different morphological differentiations depending on their site of origin at the early stage of astrogliogenesis and corresponding to the different modes of neurogenesis in the two cortical structures.

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Expression of aquaporin-8 mRNA has previously been shown in hepatocytes, pancreatic acinar cells, colon epithelial cells and seminiferous tubules of the testis in the rat by in situ hybridization technique. However, immunolocalization of this water channel has not yet been demonstrated. In the present study, the localization of immunoreactive aquaporin-8 and expression of the mRNA were examined in rat organs (cerebrum, cerebellum, eye, salivary gland, heart, lung, liver, pancreas, esophagus, stomach, jejunum, ileum, colon, testis, ovary, kidney, spleen and lymphnode) by immunohistochemistry using an antibody against aquaporin-8 and ribonuclease protection assay. Aquaporin-8 was distinctly immunolocalized on the apical membranes of pancreatic acinar cells and mucosal epithelium of the colon and jejunum. In the liver, the bile canalicular membrane of hepatocytes was immunostained. In the testis, immunoreactive aquaporin-8 was demonstrated on the luminal side of the seminiferous tubules. At high magnification, the peroxidase reaction products appeared on the ramified cytoplasmic membrane of Sertoli cells surrounding the residual bodies or spermatogenic cells. Specificity of the antibody was verified by Western blot analysis showing a minor ∼28 kDa band (deduced deglycosylated form of aquaporin-8) and a major ∼30 kDa band (glycosylated form) in these organs. The intensity of aquaporin-8 immunoreactivity was approximately comparable to that of aquaporin-8 mRNA expression in the liver, pancreas, colon, jejunum and testis. The aquaporin-8 mRNA expression in the hepatocytes was presumed to be closely associated with the structure of bile canaliculi since the message was detected in hepatocytes immediately after isolation from the liver but not in cells following cultivation for three days.
  The localization of immunoreactive aquaporin-8 indicated functions for this water channel in the secretion of bile and pancreatic juice, and the secretion or absorption of water in the colon and jejunum, and the maturation or liberation of spermatogenic cells in the testis.

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Heme oxygenase (HO)-1, the heme-degrading enzyme in macrophages, plays a key role in bilirubin metabolism. HO-1 is expressed in various tissue macrophages, especially Kupffer cells. This study aimed to examine the roles of macrophages and HO-1 in the modulation of heme catabolism in rat livers. Rats treated with or without liposome-encapsulated dichloromethylene diphosphonate, a macrophage-depleting reagent, were administered with heat-denatured red blood cells (h-RBC), and the time course of the biliary output of bilirubin and the expressions of HO-1 mRNA and protein were monitored. Immunohistochemistry in the control rat liver revealed that Kupffer cells constitute a major cellular component expressing HO-1, while hepatocytes exhibited little expression. The levels of HO-1 expression in Kupffer cells were elevated immediately after injection of h-RBC. In Kupffer cell-depleted livers, however, HO-1-expressing cells were not detected even after h-RBC administration. HO-1 mRNA levels were elevated at 2 h after administration of h-RBC in control rat livers, while they were very low in Kupffer cell-depleted rat livers. The control and Kupffer cell-depleted groups exhibited distinct time courses of biliary bilirubin excretion. In the untreated control rats, total bilirubin excretion increased about two-fold at 5 h after h-RBC administration. In contrast, the Kupffer cell-depleting treatment decreased the level of bilirubin production; administration of h-RBC to Kupffer cell-depleted rats did not accelerate the generation of bilirubin. These results suggest that Kupffer cells serve both as a sensor for scenesent RBC clearance and an effector that upregulates heme-degrading capacity and bilirubin production.

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In order to clarify the process of renal development more precisely than previously, the present study observed the rat neonatal kidney by scanning electron microscopy (SEM) of KOH digested tissue as well as by light microscopy of plastic sections. In the subcapsular region, aggregation of the mesenchymal cells was closely associated with the upper side of the ureteric duct ampulla. These mesenchymal cells projected a number of fine irregular processes at the basal portion facing the ureteric duct. A spherical cluster transformed from the mesenchymal cell aggregation was found on the lower side of the terminal ampulla, and was differentiated into the renal vesicle. Some cells at the top of the renal vesicle formed a cone-shaped projection and invaded the ureteric duct ampulla, forming a connection with it. In the advanced stage, a shallow transverse cleft appeared on the outer lateral side of the renal vesicle, and a second cleft was formed on the opposite side close to the junction between the renal vesicle and the ampulla. As the two clefts deepened, the vesicle assumed the well-known S-shaped body. In the advanced S-shaped body, the lower limb became cup-shaped, while the segment between the middle and lower limbs of the “S” elongated to form a tubular structure (i.e., the prospective proximal tubule and Henle’s loop). The upper limb of the “S” also increased its length to form a distal tubule. The middle limb of the “S”, however, was attached firmly to the cup-shaped lower limb (i.e., the prospective renal corpuscle) and was considered to become the macula densa of the mature nephron. In the maturing renal corpuscle, irregularly shaped cells were observed as a sheet-like aggregation at its vascular pole and were continu-ous with the vascular smooth muscle cells. These findings will help toward a better understanding of the morphological complexities of nephrogenesis.

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The present study demonstrated the three-dimensional architecture of peri-insular nerve plexuses in the murine pancreas by the combined use of light microscopy of S-100 immunostained sections, transmission electron microscopy (TEM) of thin sections, and scanning electron microscopy (SEM) of KOH digested tissues. By light microscopy of thin sections immunostained with anti-S-100 antibody, Schwann cells were often found on the margin of the islets as if delimiting the islet and exocrine parenchyma. In thick sections, Schwann cells of the islet connected their thin and slender processes with each other to form a delicate network on the surface of the islet. By TEM, Schwann cells were observed as an attenuated sheet that invested the surface of the islet. Axon terminals were usually found on the outer surface of these membranous Schwann cells. SEM of KOH digested tissues revealed that nerves reaching the islet spread on the insular surface. Schwann cells in this portion extended their thin membranous processes, which directly covered the basal part of several endocrine cells as a whole. Numerous axons with varicosities were usually found on the surface of these membranous Schwann cells, but sometimes crept beneath them.
  These findings indicate that “the interstitial cells” described by light microscopists are peculiar-shaped Schwann cells present in the islets. The functional significance of the rich innervation of the islets is also briefly discussed in the present study.

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The Purkinje cells in the adult cat cerebellar cortex were found to possess perineuronal proteoglycans which could be stained with our fine cationic iron colloid and Fujita’s highly concentrated aldehyde fuchsin, and digested by chondroitinase ABC/keratanase/ heparitinase and hyaluronidase. The Purkinje cells are surrounded by some collagenous elements wrlich are stained with Gömöri’s ammoniacal silver and digested by collagenase. The Purkinje cells also express nerve cell surface glycoproteins which are labeled with lectin Vicia villosa agglutinin and digested by a double treatment with collagenase and endo-alpha-N-acetylgalactosaminidase. Sole digestion by endo-alpha-N-acetylgalactosaminidase never erased the lectin labeling of the nerve cell surface glycoproteins. These findings suggest that the collagenous elements mediate the linkage of the perineuronal proteoglycans to the nerve cell surface glycoproteins. It is presumed that in mice and rats, the perineuronal nets of proteoglycans and nerve cell surface glycoproteins of the Purkinje cells are so thin or coarse that they can not be sufficiently visualized under the light microscope.

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The development of GH cells and the pituitary-adrenal axis was morphologically examined in male Djungarian hamsters (Phodopus sungorus) exposed to short days and those kept under long days and receiving daily afternoon injections of melatonin, from the time of weaning (20 days) until 100 days of age. The postnatal increase in area of ACTH cells under long days was inhibited in short-day-exposed or melatonin-treated animals. It was suggested that a short photoperiod may suppress, via melatonin, the development of ACTH cells. GH cells were not affected by age, photoperiod or exogenous melatonin. Under long days, the zona fasciculata decreased in volume with age, while the zona reticularis increased. Such changes in the volumes of these adrenocortical zones were depressed under short days. In addition, the volumes of the zona fasciculata and zona reticularis in long-day-housed animals became respectively larger and smaller subsequent to orchidectomy and melatonin administration. These results suggest that fasciculata cells in deeper levels become progressively differentiated into reticularis cells, that short photoperiod inhibits devel-opment of both zonae, and that such an inhibition is caused mainly by the decreased secretion of androgens.

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Rat dendritic cells selectively bind to Kupffer cells in vitro. The present study aimed to reveal adhesion molecules on dendritic cells and their roles in the host defense system. The in situ binding assay to examine the effects of pretreatment of dendritic cells with various kinds of monosaccharides suggested that N-acetylgalactosamine was necessary for the binding of dendritic cells to Kupffer cells. This binding was also attenuated when dendritic cells were injected into an ex vivo liver perfusion circuit together with N-acetylgalactosamine. It was further shown that the majority of rat lymph dendritic cells and some interdigitating dendritic cells in the lymph nodes possessed asialoglycoprotein receptors specific for N-acetylgalactosamine/ galactose as detected by immunostaining. Lymph dendritic cells could ingest virus particles in vitro, even though these cells showed no phagocytic activity for latex particles. The results indicate that rat dendritic cells possess asialoglycoprotein receptors which are probably utilized to recognize Kupffer cells for their recruitment to the liver and possibly to recognize virus particles prior to phagocytosis.

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