The plasmalemmal undercoat can be defined as the electron-dense material of layered organization closely applied to the cytoplasmic surface of the plasma membrane (plasmalemma) as revealed by thin-section electron microscopy. Though the structures which fulfill this criterion occur widely, most of them have not received the attention they may deserve. The undercoat is a special form of the cytoskeleton-membrane interaction, though it constitutes a part of the cytoskeleton. The significance of the plasmalemmal undercoat may be primarily to provide a structural support for the membrane. With this support, cells can perform many important functions on their limited or whole surfaces. The undercoat may provide a mechanical support to the plasmalemma so that the membrane may acquire rigidity, strength and elasticity. Through association with the membrane, the undercoat may regulate the distribution of integral membrane proteins to form and maintain various functional domains on the plasmalemma. The undercoat may further provide attachment sites for cytoskeletal fibrous components such as actin filaments, intermediate filaments and microtubules.

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A well developed extra-adrenal chromaffin body with an axis of 200-400μm was found in seven out of thirty adult male Wistar rats under a stereomicroscope. All seven bodies were located between the left and right kidneys. Blood vascular beds of the five bodies were reproduced with a methacrylate casting medium and observed with a scanning electron microscope. It was revealed that the extra-adrenal chromaffin body contained remarkably numerous capillaries, which anastomosed with each other to form a conglomerated network. The blood capillaries were of small and uniform caliber and did not represent swollen sinusoids as in the adrenal medulla. The capillary network was denser than that in the adrenal medulla and had no direct vascular linkage with the adrenal cortex or an extra-adrenal cortical body. Histological examination of the two bodies treated with dichromate containing fixatives confirmed that they mainly consisted of chromaffin cells. These findings suggest that in the rat, extra-adrenal chromaffin bodies survive throughout life, actively producing catecholamines.

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The distribution of acetylcholinesterase (AChE)-positive nerve fibers in the chicken pancreas was investigated with histochemical methods at the light and electron microscopic level. AChE-positive nerve bundles were found to run along the pancreaticoduodenal artery and their branches proceed into interlobular connective tissue, form a plexus around the interlobular secretory ducts and small arteries, and penetrate the exocrine parenchyma. Intrapancreatic ganglia showing a strong AChE activity were detected within the interlobular connective tissue or between acini. The exocrine pancreas was richly innervated with AChE-positive terminals which contained a few large densecored vesicles (about 100nm in diameter) and many small clear vesicles (about 50nm in diameter). Such terminals made contact with intercalated ductular cells and the smooth muscles of larger blood vessels. The endocrine pancreas was supplied with fewer nerves than the exocrine pancreas. A different distribution of AChE-positive fibers was noticed between A- and B-islets which were distinguished immunohistochemically. B- and D-cells were richly innervated by AChE-positive nerves, whereas A-cells, only poorly. These observations make clear that the cholinergic system relates to the regulation of both exocrine and endocrine tissues, except A-cells, in the chicken pancreas.

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A dense plexus of CGRP-immunoreactive nerve fibers was found subjacent to and within the epithelium of the excretory ducts of the parotid, submandibular and sublingual glands in the rat, in close proximity to the opening into the oral cavity. The immunoreactive nerve fibers disappeared after a neonatal administration of capsaicin. In immuno-electron microscopy, the immunoreactive nerve fibers were characterized by abundant small clear vesicles mixed with some large granular vesicles, but not by any particular abundance of small mitochondria. Intraepithelial immunoreactive fibers were directly apposed to adjacent epithelial cells without any membrane specializations. They did not exceed the subapical junctional complex of the epithelial cells.

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Conjugate of horseradish peroxidase and wheat germ agglutinin (HRP-WGA conjugate) was injected into the midbrain central gray (MCG) of three adult rats. Frontal sections of the diencephalon were first treated with diaminobenzidine and hydrogen peroxide to detect the retrogradely transported conjugate. They were then stained immunohistochemically to detect pro-opiomelanocortin (POMC)-derived peptides (ACTH, β-endorphin and α-MSH). The coexistence of the three POMC-derived peptides was confirmed by the immunohistochemistry of three consecutive sections stained with antiserum specific to each peptide. Some of the neuronal perikarya distributed in and around the arcuate nucleus were positive to the immunohistochemical stain for POMC-derived peptides, and, concomitantly, were labeled with HRP-WGA conjugate, which indicated that they projected to the MCG. They were mostly concentrated in the rostral three-fifths of the arcuate nucleus. The finding that some of the POMC neurons in the arcuate nucleus project to the midbrain central gray deserves interest, because the central gray is involved in analgesia induced by opioid peptides.

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The terminal segment of the seminiferous tubule in the testis of the adult domestic cat was investigated using scanning and transmission electron microscopy. The terminal segment gradually tapers towards the tubulus rectus, while transforming into tall columnar supporting cells termed modified Sertoli cells which protrude into the lumen of the tubulus rectus in the form of a plug. There is no distinct central lumen in the plug, rather, it is a narrow slit-like cleft surrounded by the modified Sertoli cells.
The modified Sertoli cells of the plug as well as the cuboidal cells lining the tubulus rectus revealed an active Phagocytosis of spermatozoa and even injected inert latex beads. These epithelial cells are thought to act as a protective filtration line for foreign bodies including unwanted spermatozoa.

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The existence of three morphologically different types of GH cells in the rat anterior Pituitary glands has been reported previously. Among these three types, Type III which contains the smallest granules has been considered to be immature, because this type occurs more frequently in neonatal rats than in adults. In this study, the prenatal development of GH cells in the rat fetus was observed by immunoelectron microscopy. In the rat fetus at 18.5 days of gestation, Type III cells were most numerous (48.5%), followed by Type II cells (45.5%). Type I cells were almost absent from these fetal pituitaries. At 20.5 days Type II cells exceeded Type III in frequency, and Type I cells also increased to about 35%. These results indicate that Type III cells are the most immature type of GH cells, and might transform into Type II and, in turn, to Type I, as the rats mature.
Images indicating active secretory functions such as qranule formation in the Golgi apparatus and/or GERL, exocytosis and crinophagy were observed in the GH cells even in the fetal stage.

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The cellular and nervous elements of the bullfrog taste organ were examined by immunhistochemical methods using various antibodies.
The immunoreactivity for spot 35 protein, a soluble protein isolated from bovine cerebellum, was found in numerous taste cells located at the middle or slightly lower levels within the gustatory cell layer. The immunoreactive cells possessed cytoplasmic processes rising upward the free surface and also issued branched processes to the base of the epithelium. The immunoreaction for spot 35 protein was found diffusely throughout the cytoplasm from the apical to the basal parts of the taste cells.
NSE-immunoreactive taste cells were located at the upper or middle levels within the gustatory cell layer in the taste organ. The fact that the cells were smaller in number and size than spot 35 protein-reactive cells and further differed in localization distinguished the NSE-taste cells from the spot 35 protein cells.
Serotonin-like immunoreactivity was detectable in the basal cells localized at the base of the taste epithelium. The immunoreactive cells were arranged in a circle at the periphery of the taste organ, each extending a slender process toward the center. The terminal portion of this process spread leaf-like; numerous fine projections protruded from its margin. The serotonin-immunoreactive cells appear to coincide with the monoamine-containing basal cells, which have been previously reported.
Substance P-, calcitonin gene-related peptide (CGRP)-, vasoactive intestinal polypeptide (VIP)-, peptide HI (PHI)- or gastrin releasing peptide (GRP)-immunoreactive nerve fibers with varicosities were demonstrated within the taste organ. Some substance P-fibers ran along the bottom of the taste organ epithelium. A few thinner substance P-fibers ascended among the epithelial cells of the organ and terminated closely below the free surface. CGRP-fibers were found to correspond to substance P-fibers from their evidencing a double immunostaining. VIP- and PHI-fibers formed a meshwork in the basal area of the taste epithelium. Abundant substance P- and/or CGRP-fibers formed a meshwork among the ciliated cells located at the periphery of the taste organ. However, PHI- and GRP-fibers were detected less than substance P- and/or CGRP-fibers, though VIP-fibers were rarely present in the same region.
Neurofilament protein- or tyrosine hydroxylase-like immunoreactivities were found in thick nerve fibers in the taste organ, whereas no immunoreactivities were present in cellular elements within the taste organ.
The relationship between cellular and nervous elements in the taste organ was examined by double immunostainings. The substance P-fibers were closely related with both spot 35 protein- and serotonin-immunoreactive cells. In addition, VIP-fibers were found in connection with serotonin-immunoreactive cells.
From the present study, it is concluded that the bullfrog taste organ might be a chemo-mechanoreceptive sensory organ.

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