The three-dimensional structure of the transverse-axial tubular system, sarcoplasmic reticulum (SR) and mitochondria in the capsular sleeve region of the intrafusal muscle fibers of the rat lumbrical muscle was observed by ultra-high-resolution scanning electron microscopy after removal of the cytoplasmic matrix by the osmium-DMSO-osmium procedure. Nuclear chain fibers were seen to have slender I-band limited mitochondria, and thick column-forming mitochondria which occasionally exhibited I-band branches. The transverse tubules (T-tubules) ran at the level of the A-band side of the A-I junction and were sandwiched between two large terminal cisternae for most of their length, forming triads. The sarcotubules arising from the terminal cisternae formed single-layer networks at the A-band level, and well developed, double-layer, three-dimensional networks at the I-band level. Occasionally, tetrads and pentads were also seen. Nuclear bag₂ fibers possessed column-forming mitochondria of medium size, practically devoid of I-band branches. The T-tubules ran at the level of A-band adjacent to the A-I junction and were coupled with terminal cisternae of various lengths at intervals. As a rule, the SR formed single-layered networks at the level of the A-band and double-layered networks at the I-band level, and was less developed than in chain fibers. Nuclear bag₁ fibers contained slender column-forming mitochondria devoid of I-band branches. The T-tubules were located at the level of the A-I junction. Both the T- and the axialtubules were occasionally coupled with small terminal cisternae, forming dyads or triads. At the I-band level, the SR was well developed and formed single layer networks, but at the A-band level only a few longitudinally arranged sarcotubules and axial tubules were recognized.

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In the buffalo, seminiferous tubules occupy about 82% of the testis. Spermatogenesis can be divided into 6 stages according to characteristic cellular associations in the seminiferous epithelium. A-spermatogonia have a volume of -1, 400μm³ and the highest absolute mitochondrial volume of all spermatogenic cells. B-spermatogonia display cellular, nuclear and mitochondrial volumes of approximately half the values of A-spermatogonia. From preleptotene (-470μm³) to late diplotene (-2, 300μm³), the volume of primary spermatocytes increases nearly five-fold; their nuclear volumes increase by 3.5 times within the same period. During zygotene mitochondrial cristae start to dilate. Grouping of mitochondria by a dense intermitochondrial substance is most prominent during pachytene and diplotene. In pachytene the absolute size of the Golgi apparatus more than doubles, indicating a high secretory activity. Through zygotene only rER is encountered; in pachytene and diplotene a tubular sER makes its first appearance. Secondary spermatocytes are found only in stage 4 of the cycle. Due to partial cell necrosis and autolytic events, late maturation phase spermatids display no more than 25% of the size of cap phase spermatids. There is no morphological evidence for an active uptake and digestion of residual bodies by the Sertoli cells. Also, no lipid cycle is present in the buffalo seminiferous epithelium. Morphometric evaluations reveal that 63% of all theoretically possible germ cells disappear from the seminiferous epithelium during spermatogenesis. Heavy cell loss is observed in stage 4 of the cycle in the spermatogonial fraction as well as during the second meiotic division.

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The adenohypophysis occasionally contains cysts of epithelial nature. The present study describes the incidence and immunohistochemical characteristics of these epithelial cysts in the adenohypophysis of rats at different ages and in young mice. Epithelial cysts were found in about 10% of the partes distales irrespective of age and animal species. Their incidence in the pars tuberalis was higher: 22% and 58% in young rats and mice, respectively. Immunohistochemically, cells composing these cysts failed to contain S-100 protein. Although cysts found in the pars tuberalis frequently possessed immunoreactive luteinizing hormone-producing cells, most cysts in the pars distalis were immunonegative when stained with antisera to several different adenohypophysial hormones. Examination of fetal rat hypophysis has shown a close topographical relationship between cysts and the pharyngeal duct. This fact, together with the frequent occurrence of cysts in the ventro-medial region of the pars distalis in neonatal and young animals, indicates that these cysts are probably derived from a part of oral epithelium that is otherwise destined to degenerate at the time when Rathke's pouch closes.

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The distribution of synaptophysin, a major protein of the synaptic vesicle membrane, was immunocytochemically examined in the rat cerebellar cortex. A monoclonal antibody against synaptophysin recognized the epitope to be present in the presynaptic membranous structures including synaptic vesicles, presynaptic membrane, coated vesicles, and vacuoles of endocytotic origin. In the nerve terminal as well as preterminal areas, the antibody labeled the smooth-surfaced tubular membranes which were located in the relatively interior parts of these areas and consistent in size and appearance with the short tubules comprising the thinner parts of the axonal reticulum. However, the antibody did not stain the short tubular membranes, though similar in appearance to the above, which existed right below the axolemma in the preterminal and nerve terminal areas. The results are discussed with special reference to the precursor membrane compartments of synaptic vesicles.

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Porcine tooth germ was investigated immunochemically and immunocytochemically using antibodies against a synthetic N-terminal peptide fragment from a 32kDa nonamelogenin found in the inner (old) secretory enamel. In immunochemical preparations, these antibodies reacted to many proteins of differing molecular weights, especially to 140kDa, 89kDa, 56kDa, 45kDa, and 32kDa proteins. Analysis of the layers of enamel suggested that the 140kDa and/or 89kDa proteins, both of which were found in newly formed enamel, were the parental proteins secreted by the ameloblasts, and that they were degraded to produce 32kDa and other low molecular-weight proteins associated with progressive mineralization. In immunohistochemical preparation, immunoreactivity at the differentiation stage was detected initially over the amorphous dense material or fine fibrils around calcified globules in predentin, while the stippled material was devoid of immunoreactivity. The amorphous dense material seemed to give rise to a continuous layer of initial enamel. At the matrix formation stage, the immunoreactivity of immature enamel just beneath the putative secretory face of the Tomes' processes was intense. From the surface of the enamel matrix to a depth of about 100μm, immunoreactivity of prism sheaths was weaker than that of enamel prisms, producing a reverse honeycomb pattern. In the enamel matrix deeper than 100μm, immunoreactivity was weak and homogeneously distributed. The Golgi apparatus and secretory granules of the secretory ameloblasts showed immunoreactivity. These results suggest that the likely parent proteins of the 32kDa nonamelogenin protein, i. e., the 140kDa and/or 89kDa proteins, play a significant role in the calcification of the enamel matrix.

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Morphological studies were carried out to delineate the characteristics of connective tissue sheaths surrounding working myocardial cells and Purkinje cells in the moderator band of adult sheep hearts, using a series of techniques including silver staining, immunohistochemistry, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). For SEM, tissue blocks were treated with 2N NaOH at room temperature to digest cellular elements.
Individual working myocardial cells were ensheathed by thin argyrophil fibers (reticular fibers), while fascicles of 4-8 Purkinje cells (Purkinje strands) were encircled by rather thick reticular fibers. Some collagen fibers were located between masses of myocardial cells as well as between the Purkinje strands. Immunohistochemical analyses indicated that reticular fibers directly surrounding both myocardial cells and Purkinje strands showed moderately positive reactions for adti-type I collagen and intensly positive reactions for anti-type III collagen.
Deserves particular note is that the three-dimensional architecture of the reticular sheaths varied widely at different places. The thin reticular sheaths surrounding each myocardial cell consisted of fibrils which were arranged in a coarse network and directed circularly along the long axis of cells. By contrast, the sheaths enclosing Purkinje strands were thicker, and their reticular fibrils were woven into a compact “felt-like” texture. The functional significance of these connective tissue sheaths is also discussed.

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General and histochemical observations of the thymus were carried out in guinea pigs after injection of cyclophosphamide (280mg/kg). Acute involution of the thymus induced by cyclophosphamide was accompanied by marked enlargement of Hassall's corpuscles in the first week after injection. However, the markedly enlarged Hassall's corpuscles disappeared entirely by the fourth week. Large cells characterized by pale nuclei with one or two prominent nucleoli became aggregated in the enlarged Hassall's corpuscles by the second week. Their cytoplasm frequently was foamy or vesicular in appearance. Histochemical observations revealed strong activities of nonspecific esterase, acid phosphatase and β-glucuronidase in these cells. Staining for these lysosomal hydrolytic enzymes was evident not only intracellularly but also extracellularly, indicating the dissolution of Hassall's corpuscles by intensive extracellular enzyme release.

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Gonadotrophs immunocytochemically identified with an antibody to LHβ were studied in both male and female rats of various ages, viz., 2, 14 and 23 months after birth. The rat gonadotrophs are classified into two cell types, i. e., Type I containing large (300-700nm) and small (150-200nm) secretory granules, and Type II containing only small (100-200nm) secretory granules. In normal young adults, the male rat pituitary contains a large number of Type I cells (more than 90% of all gonadotrophs), whereas the female pituitary contains much more Type II cells (more than 70%) than Type I cells. With age, Type I gonadotrophs in the male rat pituitary decrease remarkably to less than 25%, while Type II cells constitute more than 70% at the age of 23 months; the ratio of Type I to Type II comes to be the same as in the female. The main cause of this change is the decrease in the number of large secretory granules as the animal ages.
FSH and LH levels in both the pituitary and serum were determined by radioimmunoassay. Pituitary FSH content decreased gradually in the male with age, while that in the female showed no change. LH content in the male decreased slowly, but LH in the female increased with aging. The large secretory granules indicating the presence of FSH markedly decreased with aging. The Type II cells contain only small secretory granules which probably contain LH. Thus the results of morphological counting of each type of gonadotroph and those of radioimmunoassay of gonadotropins during aging were essentially parallel. Some signs of degeneration were observed in the gonadotrophs in the aged rat pituitaries.

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Gastrin-releasing peptide (GRP)-containing nerves are extremely numerous in the mucosa of the gastric body. Our previous study demonstrated that depletion of GRP from the nerves occurred in close relation to ulceration in the stomach. The present study deals with the ultrastructure of the GRP-immunoreactive nerves under normal conditions and its changes induced by conditions of stress. The immunoreactivity for GRP was recognized selectively in large cored vesicles in the swollen axoplasm of the nerves. The same axoplasm further revealed immunonegative small clear vesicles which were believed to contain acetylcholine. In materials where the GRP-immunoreactive nerves markedly decreased in number, both large and small synaptic vesicles were depleted from the nerves. These findings suggest that GRP and acetylcholine coexist in single nerves in the oxyntic mucosa, and that by nerve stimulation, they are coreleased into the lamina propria.

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