No abstract

Little attention has been paid to adrenal sustentacular cells, and several major histology textbooks do not even describe them. This study presents a detailed morphological description of sustentacular cells using immunolight microscopy and an antibody against brain-type fatty acid-binding protein. The immunopositive sustentacular cells and processes formed lattices with holes of various sizes and compactnesses or openness. In addition, weakly immunostained sheet-like structures with ill-defined contours were often associated with the processes and lattices. In the carotid body, which has traditionally been classified under the name of paraganglia in common with the adrenal medulla, immunostained sustentacular cell processes formed lattices in association with the weakly immunostained sheet-like structures, but the lattices with sheets were more compact and rigid than the adrenal medulla, and appeared like individually distinct compartments. In the ganglion, the immunostained satellite cell processes with the sheets tightly enclosed individual neurons. As a result, the immunostained sheet-like structures were regarded as en-face views of thinly flattened sustentacular cytoplasmic envelopes partially covering the chromaffin cells in the adrenal medulla, and widely in the carotid body in a way rather similar to the satellite cells in the ganglion. In brief, the terminal enclosing portions of adrenal sustentacular cell processes, in cut-views, were too thin/flat to be recognized as distinct lines in immuno-light microscopy because of its resolution limit. They are recognized in en-face views as entities of a substantially spacious extension in immuno-light microscopy.

The present immunohistochemical study was attempted to localize in the submandibular glands of mice at various postnatal stages a diacylglycerol kinase (DGK) isoform termed DGKζ which is characterized by a nuclear localization signal and a nuclear export signal. This attempt was based on following facts: the continuous postnatal differentiation of glandular cells in the rodent submandibular gland, the regulatory role of DGK in the activity of protein kinase C (PKC) through attenuation of diacylglycerol (DAG), and the possible involvement of PKC in various cellular activities including the saliva secretion as well as the cell differentiation. As a result, a selective localization of immunoreactivity for DGKζ was detected in terminal tubule (TT) cells which comprise a majority of the newborn acinar structure and differentiate into the intercalated duct cells and/or the acinar cells. The immunoreactivity was deposited in portions of the cytoplasm lateral and basal to the nucleus, but not in the nuclei themselves. Although the immunoreactive TT cells remained until later stages in female specimen than in male, they eventually disappeared in both sexes by young adult stages. The present finding suggests that the regulatory involvement of DGKζ in PKC functions via control of DAG is exerted in the differentiation of the TT cells. In addition, another possible involvement of DGKζ in the regulation of secretion of the TT cells as well as its functional significance of its nuclear localization in the submandibular ganglion cells was also discussed.

No abstract

It is known that phosphatidylinositol phosphate 5 kinase (PIP5K) γ and phospholipase C (PLC) β3, working sequentially in the phosphoinositide cycle, are localized in dorsal root ganglion (DRG) somata and are involved in the regulation of pain and related sensations. However, the sites of their involvement have remained to be clarified. In the present study, immunoreactivity for PLCβ3 was distinct only in the central process of mouse DRG, but not in its peripheral process, in contrast to distinct PIP5Kγ‐immunoreactivity in both peripheral and central DRG processes. No nerve terminals showing immunoreactivity for PLCβ3 were detected in any peripheral sensory fields, similar to PIP5Kγ‐immunoreactivity. In DRG somata, PIP5Kγ‐immunoreactivity was rather confined to the neurolemma in which dots and threads were discerned in 3D bright field light microscopy. This feature well corresponded to its discontinuous localization along the plasma membranes in immuno‐electron microscopy. In contrast, PLCβ3‐immunoreactivity occurred diffusely throughout the somata, but did not take distinct appearance of immunoreaction on neurolemma or plasma membranes, unlike PIP5Kγ‐immunoreactivity. In addition, satellite glial cells were immunonegative for PLCβ3, but immunopositive for PIP5Kγ. The involvement of PLCβ3 in regulation of pain and related sensations is thus suggested to be mainly exerted at levels of the DRG soma and its upstream, but to be less significant in the peripheral sensory fields, similar to PIP5Kγ. The possibility is also suggested that PIP, PIP5Kγ‐target, is localized heterogeneously, but PIP2, PLCβ3‐target, is localized homogenously over the plane of the neuronal plasma membranes. Research Highlights PIP5Kγ, different from PLCβ3, was localized heterogeneously on neuronal membranes, and this difference was demonstrated in 3D‐bright field immuno‐light and electron microscopy. Either PIP5Kγ or PLCβ3 was not detected in peripheral nerve terminals.