Glutaraldehyde fixed rat kidney blocks showed no charging effect when treated with lysine and osmic acid and viewed in a scanning electron microscope using an acceleration voltage of 5-30kV and a specimen current of 1×10-10A. The podocyte processes and endothelial micropores of the glomerulus were visible without metal coating. Glutaraldehyde fixed, tannin-osmium impregnated and lysine-osmium treated specimens also showed no charging effect in the scanning electron microscope, yielding instead much clearer scanning images which were comparable to those obtained from gold-coated specimens or from tannin-osmium-thiocarbohydrazide-osmium impregnated specimens (MURAKAMI and JONES, 1980).
Blood vascular beds of the rat parathyroid glands were reproduced with a methacrylate casting medium and observed with a scanning electron microscope. The rat possesses only a single pair (one left and the other right) of parathyroid glands. Each gland was found to contain a rich capillary network which was completely isolated from the capillary plexus of the thyroid gland. Each parathyroid gland received some small afferent arteries from the superior thyroid artery and emitted a thick efferent vein continuous with the superior thyroid vein. The capillary network of the parathyroid gland consisted of freely anastomosing capillaries. The afferent arteries were divided in the superficial and deep layers of the gland. The thick efferent vein arose in the deep layer of the gland. Some small or accessory efferent veins arose in the superficial layers of the gland. These also drained into the superior thyroid vein.
A sufficient differentiation of lymphatic capillaries from blood capillaries in conventional light microscopy still eludes researches. The endothelium and media of lymphatic capillaries are characterized by a strong 5′-nucleotidase activity, whereas blood capillaries reveal no or significantly lower activity. Alkaline phosphatase activity, on the other hand, missing in the lymphatic capillaries is positive in most of the blood capillaries. For the histochemical visualization of the entire blood capillary bed, dipeptidyl peptidase IV-activity has to be used together with alkaline phosphatase. Various fixation and detection methods of 5′-nucleotidase are compared. In order to demonstrate 5′-nucleotidase activity, a method modified after HEUSERMANN (1979) is considered to be most suitable. The results obtained are discussed with regard to their significance concerning the visualization of lymphatic capillaries. They are compared with a series of investigations in which alkaline phosphatase and dipeptidyl peptidase IV-activity are visualized in blood capillaries additional to the 5′-nucleotidase reaction. Various color reactions reveal a differentiation between blood capillaries and small lymphatics. The isolated visualization of 5′-nucleotidase activity with a simultaneous inhibition of alkaline phosphatase with L-tetramisole is considered to be the best way to histochemically demonstrate lymphatic capillaries. It was shown for the first time that only in the presence of L-tetramisole can small lymphatics be adequately visualized. A satisfactory differentiation between blood and lymphatic capillaries succeeded by means of a different color intensity of the reaction product.
The three-dimensional structure of the Sertoli cell in the miniature “shiba” goat was examined using scanning electron microscopy. In the basal portion of the seminiferous epithelium, spermatogonia and/or spermatocytes were located in compartments enclosed by adjacent Sertoli cells. From the basal aspect, they were situated in successive recesses. In the middle portion, early round spermatids halfway embedded in the Sertoli cell were recognized. The exposed surfaces of these spermatids were wrapped with ramifying processes which were derived from the Sertoli cell. In the apical portion, only the heads of the maturing spermatids invaded the Sertoli cell. As the spermatid matured, the apical Sertoli process varied in range to finally release the spermatid head. It is probably that the maturing spermatids gradually leave the apical Sertoli process and ultimately segregate themselves from the seminiferous epithelium.
The appearance and distribution of desmin, a muscle type intermediate filament, was examined in the truncus arteriosus of the chick embryonic heart during AP septation by an indirect immunofluorescence method. Prior to septation, on the 4th day of incubation, staining with antidesmin antibody was observed in the AP septum anlagen in the distal truncus. No staining with the antibody was detected in the developing tunica media of the great arteries in the distal truncus at this stage. During septation, on the 5th day of incubation, intense staining with the antidesmin antibody was observed in the cell condensation of the AP septum. In the 6-day-old embryo, the staining in the AP septum was reduced, but fluorescence by staining with the antibody was observed in the developing tunica media. No fluorescence was detected in other mesenchymal cells in the truncal swellings. Because of the time of appearance and the localization of antidesmin reactivity in the developing AP septum, it is suggested that muscle-type cells exist in the AP septum, and that these cells may perform an important function in septation.
Age-related changes in the testis were studied histologically in dd-mice from 2 months to 2 years of age. After 6 months of age, vacuoles appeared first singly and later became clustered in the seminiferous epithelium. With the appearance of the vacuoles, the epithelium started to release spermatids and spermatocytes into the lumen. Multinucleated giant cells occasionally appeared in the epithelium and were also released to the lumen. The epithelium, when markedly depleted of germ cells, was composed mainly of Sertoli cells. The lumen of the atrophied tubules occasionally contained accumulations of macrophages, sperm aggregations, and nodules of a homogeneous material covered with flattened epithelial cells. The basement membrane surrounding the atrophied tubules thickened corresponding to the degree of atrophy. The atrophied tubules initially appeared in patches and then spread throughout the testis. Leydig cells increased in amounts with age. The increase of Leydig cells was distinct around severely atrophied tubules with a thickened basement membrane. These changes are discussed in comparison with autoimmunized testes which show similar histologic changes.
Immunocytochemical localization of 17β-hydroxysteroid dehydrogenase (17β-HSD) and its relation to the ultrastructure of steroidogenic cells were examined in mature and immature rat ovaries. In mature (8-10 weeks old) rat ovaries, the theca interna cells of secondary as well as Graafian follicles, and the interstitial gland cells were all strongly stained with anti-17β-HSD antibody. However, granulosa cells, corpus luteum cells, oocytes and peritoneal epithelial cells were negative against this staining. In the ovaries of 1-week-old rats, all these cells were negative to immunostaining for 17β-HSD. In the ovaries of 2-week-old rats, the theca interna cells of secondary follicles and the interstitial gland cells showed a positive reaction for the 17β-HSD activity. Electron microscopic examination demonstrated the presence of characteristic structures for steroid secretory cells such as many lipid droplets, well developed smooth endoplasmic reticulum, and oval mitochondria with tubular cristae in the theca interna cell of secondary as well as Graafian follicles and in the interstitial gland cell of mature rat ovaries. In the ovaries of 1-week-old rats, all the theca cells of the primary and secondary follicles were fibroblast-like in their shape and fine structure, and typical interstitial cells were not recognized. In the 2-week-old rats, some of the theca interna cells and interstitial cells were well differentiated in ultrastructure, showing characteristic features for steroid secretory cells. These findings indicate that by 2 weeks after birth, theca interna cells and interstitial gland cells acquire the ability for testosterone production as seen in mature rat ovaries.
A method for scanning electron microscope (SEM) study of reticular fibers in their original shapes and locations is described. This technique was employed to demonstrate the three-dimensional organization of the reticular fibers of the human pancreas. The cellular elements were effectively removed by treatment of the tissue pieces with a 10% aqueous solution of NaOH for 3-4 days at room temperature. Thin layers of the reticular fibers surrounding the acini and ducts formed a three-dimensional interstitial compartment. The reticular fiber sheaths for the blood vessels coursed through the compartment. In the lobule, there were scattered round or oval capsules for the islets of Langerhans. The capsule also consisted of reticular fibers. Within the capsule, reticular fiber sheaths for accommodating islet capillaries, representing the pericapillary spaces, formed a threedimensionally anastomosing network. The channels for the capillaries ensheathed by the reticular fibers in the islet were continuous with those in the surrounding exocrine pancreas; thus, the insulo-acinar portal system was confirmed to exist in the human pancreas. This study also maintains that the present method is useful for examining the microvascular organization of the islet.
Striated muscle fibers appear with regularity in pituitary isografts transplanted beneath the kidney capsule. These differentiated striated muscle fibers consist of multinucleated cells resembling skeletal muscle fibers. They appear mainly in the pars distalis, though occasionally in the gars intermedia of the grafts. Although most glandular cells disappeared due to necrosis in the center of the grafted anterior pituitary, where the striated muscle fibers occurred, the folliculo-stellate cells were well preserved in this region and formed elongated myotube-like structures. The muscle fibers appearing in the central pars distalis were in close contact to the folliculo-stellate cells and also to the marginal epithelium of the pituitary cleft. In these cases the striated muscle fibers and folliculo-stellate cells were surrounded by a common basal lamina. This close association between heterotopically differentiated muscle fibers and the normally occurring folliculo-stellate cells strongly suggests a close relationship in differentiation and function between these different cells.
Multinucleated giant cells in the mouse testis after ligation of the efferent duct were examined by light and electron microscopy. The findings suggest that the giant cells are formed as a result of the fusion of spermatids due to alterations in the intercellular bridges. Further, the orientation of acrosomes, nuclei, and organelles for formation of the tail in the giant cells is related to the polarity of the spermatids.
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