The present study demonstrated for the first time the localizations and patterns of expression of key enzymes for steroidogenesis, cytochrome P450 side-chain-cleavage (P450scc), and P450 aromatase in the taste buds of rat circumvallate papillae, using immunoblot analyses and immunohistochemistry. Immunoblot analyses showed that proteins with a molecular weight close to that of rat adrenal cytochrome P450scc and a molecular weight close to that of rat ovary cytochrome P450 aromatase were present in the rat circumvallate papillae. In immunohistochemistry, antibodies against cytochrome P450scc and P450 aromatase yielded the labelings of a subset of taste bud cells. In the double immunolabeling of P450scc and α-gustducin or phospholipase Cβ2(PLCβ2), which were considered as markers of a majority of type II cells, P450scc was co-expressed in a subset of α-gustducin or PLCβ2, but did not co-express neural adhesion molecule (NCAM), a marker of major type III cells. Further double immunolabeled studies showed that P450 aromatase was co-expressed in a subset of α-gustducin or PLCβ2, but did not co-express PGP9.5, a marker of a majority of type III cells. The selective localization of cytochrome P450scc and P450 aromatase strongly suggests that estrogen biosynthesis from cholesterol might occur in a subset of type II cells of the rat taste buds. Although the full significance of estrogen in the taste bud function is not yet understand, estrogen appears to be an important regulator of taste transduction, as is the case with ATP (Finger et al., 2005), which further supports the centrality of taste cells in the life of taste buds.

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Cell proliferation in the pineal organ of the immature rainbow trout Oncorhynchus mykiss was investigated by immunocytochemical demonstration of the proliferating cell nuclear antigen (PCNA) together with photoreceptor-specific opsin. Numerous PCNA-immunoreactive cells were found throughout the pineal end-vesicle and stalk. Two types of PCNA-immuno-reactive cells were distinguished: intensely stained, large ovoid and round cells, and mildly stained, slender fusiform cells. The ovoid type of the former cell was found often in the apical region and the round type in the basal region of the epithelium, while the latter fusiform cells were scattered through the apical and middle regions. Occasionally, close approaches were found between the opsin-immunoreactive photoreceptor outer segments and the PCNA-immunoreactive cells, which expressed mildly stained, nuclear and cytoplasmic signals. In addition, overlaps of the opsin-immunoreactive outer segments with the BrdU-labelled cells were occasionally found within the pineal epithelium. These findings suggest that the proliferation and neurogenesis of the pineal photoreceptor cells might persist also in the adult rainbow trout, thus maintaining highly sensitive, photo-signal transduction mechanisms for melatonin synthesis.

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The present study was performed to examine the distribution and distinct morphology of the serotonin-containing enterochromaffin (EC) cells in the rat distal colon by immunohistochemical and electron microscopic methods. Serotonin-immunohistochemistry revealed that most of the serotonin-immunoreactive EC cells possessed extended cytoplasmic processes. In particular, the immunoreactive EC cells with long processes located along the body of the crypt were characterized by their bipolar processes comprising one with the terminal swellings extending vertically down to the basal crypt and the other running up along the luminal side - in many cases, with the apical ends reaching the glandular lumen. Moreover, a few EC cells had long processes which resembled neuronal processes with varicosities. Electron microscopic observations revealed rod-like, tortuous, oval, or round small pleomorphic granules in the long processbearing EC cells. The cell bodies and processes directly faced the crypt epithelial cells - including the enterocytes and goblet cells on one side and the basement membrane on the opposite side. The accumulation of the granules sometimes appeared within the cytoplasm on the side of the epithelial cells. These findings suggest that serotonin is released from the long processes of the EC cells and directly acts in a paracrine fashion on the crypt epithelial cells to secrete electrolytes and fluids into the colonic lumen. The long cytoplasmic processes of the EC cells may be a major contributor to the serotonininduced secretory events in the rat distal colon.

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The present study aims to identify α chains of type IV collagen in the basement membrane of the mouse ovarian follicle and examine their changes during follicular development using immunofluorescence microscopy with specific monoclonal antibodies. The basement membrane of the serous mesothelium enveloping the ovary contained all α chains of type IV collagen, α1(IV) through α6(IV) chains. Primordial follicles showed a distinct immunoreactivity against all six α chains in their basement membranes. Immunolabeling for α3(IV) and α4(IV) chains was almost eliminated in the primary follicles. In basement membranes of secondary and Graafian follicles, the immunofluorescent reaction of α3(IV) and α4(IV) chains disappeared in Graafian follicles, a partial reduction in fluorescent immunostaining intensity to α5(IV) and α6(IV) chains was observed; only α1(IV) and α2(IV) chains were not degraded throughout follicular development. On atretic follicles, in addition to α1(IV) and α2(IV) chains, α3(IV), α4(IV), α5(IV) and α6(IV) chains frequently persisted. A basement membrane-like matrix within the follicular granulosa cell layer, such as the focimatrix (focal intraepithelial matrix) and/or Call-Exner body, was also recognized in mouse secondary and Graafian follicles and contained α1(IV), α2(IV), α5(IV) and α6(IV) chains but not α3(IV) and α4(IV) chains. We expect that the decrease in α(IV) chains prompts follicular development and is a prerequisite condition for follicular maturation.

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Distributions of type IV collagen α chains in the basement membrane (BM) of human skin and its appendages were analyzed by immunofluorescent microscopy using chain-specific monoclonal antibodies. The basement membrane beneath the epidermis contained [α1(IV)]₂α2(IV) and [α5(IV)]₂α6(IV) but no α3(IV)α4(IV)α5(IV); this held true for at the eccrine sweat glands and glandular ducts, sebaceous glands, hair follicles, and arrector muscles of hair. The secretary portion of the eccrine sweat glands was rich in [α1(IV)]₂ α2(IV) and had less [α5(IV)]₂α6(IV), while [α5(IV)]₂ α6(IV) was abundant in the ductal portion. In the subepidermal zone, α5(IV)/α6(IV) chain negative spots (1.9-15.0 μm) were frequently observed. Triple staining samples (Mel.2, α2(IV) and α5(IV) chains) showed that about 50% of epidermal melanocytes colocalized with such spots. Results suggest that these α5(IV)/α6(IV) chain negative spots of the subepidermal basement membrane have a particular relationship with melanocytes and are sites for certain interactions between the two.

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