The structure and organization of paired lymphoid tissue in the nasal mucosa, situated in the transitional zone on both sides of the septal opening of the pharyngeal duct, of conventionally-housed rats was examined by light microscopy and scanning and transmission electron microscopy. Each lymphoid structure consisted of follicles containing T- and B-cell areas, and was covered with specialized epithelium. This epithelium consisted of cuboidal ciliated cells with oval nuclei parallel to the basal lamina. Goblet cells were sparse. Occasionally, islands of microvilli-bearing cells (so called membraneous or M cells) covered the lymphoid structures. M Cells were also found as single cells among the ciliated cells. The morphological characteristics and the particular localization justify the conclusion that the nasal lymphoid tissue described belongs to the mucosa-associated lymphoid tissue. It is therefore suggested that this nasal structure be designated nasal lymphoid tissue.

The distribution of nerve fibres in the mucosa of the nasal septum of the rat was investigated by means of transmission electron microscopy on transverse and tangential ultrathin sections. Near the basement membrane of respiratory and squamous epithelium, a rather dense network of unmyelinated nerve fibres occurs. Some fibres in the respiratory epithelium ascend between the epithelial cells to reach up to the tight junctions. These fibres appeared in transverse sections to end as hooks or boutons, sometimes with branches. These shapes resemble the free nerve endings that are considered to act as nociceptors. The small intraepithelial fibres, with diameters of about 0.5-1 microns, contain both dense granules and clear vesicles comparable to synaptic vesicles. Substance P was found in dense granules in basal fibres; vasoactive intestinal peptide was absent throughout the epithelium. Acetylcholinesterase activity was observed closely associated with the basal fibres; the apical fibres showed little if any activity. Membrane specializations pointing to an efferent function as well as structures usually associated with mechanoreceptive functions were lacking in both respiratory and squamous epithelium.

From a heterosexual male with recurrent genital herpes simplex virus (HSV-2) infection, a fresh intraepidermal vesicle on the penile skin was excised by punch biopsy, fixed and processed for electron microscopy. Differing locations and appearances of capsids and virions were studied to elucidate true host or destroyer cells. HSV-2 propagation and virion formation occurred predominantly in multi- or mononucleate spinosum cells situated at the base of the vesicle. However, some of the monocytes, young histiocytes and lymphocytic cells floating in the vesicle fluid were also involved. They harbored a small number of intranuclear capsids, designating the cells as viral (capsid) carriers. Infrequently encountered free virions in the vesicle fluid were invariably seen near neutrophils. All neutrophil granulocytes examined lacked intranuclear capsids. In contrast, distinct evidence of phagocytosis of virions and some capsids by neutrophils was found in the vesicle fluid near apical portions of spinosum cells packed with virions, or in neutrophils located between virion-loaded spinosum cells in the base lining of the vesicle. In the cytoplasm of neutrophils, single and lysosome-enclosed clusters of virions were noted. Myelin figures and vacuolation of lysosomes in free-floating neutrophils were suggestive of virion distintegration. Viral propagation and abundant virion formation, beside neutrophil and lymphocyte attack, eventually lead to spinosum cell destruction. The minimal cytopathic effects (CPE) observed in involved monocytes and lymphocytic cells floating in the vesicle fluid suggest that these cells might function as vehicles for HSV-2 (capsid) transport to the exterior or interior.

The dye-coupled intercellular communication across gap junctions in primary hamster tracheal epithelial cells has been studied in serum-free, hormone-supplemented medium. In the absence of vitamin A, non-cytotoxic concentrations of cigarette-smoke condensate (CSC) inhibited intercellular communication between tracheal epithelial cells in a concentration-dependent way. All-trans retinol and retinoic acid showed biphasic effects on intercellular communication depending on their concentration. Physiological concentrations of retinol and retinoic acid increased the dye-coupled transfer of Lucifer Yellow CH via gap junctions compared with the dimethylsulfoxide-treated tracheal epithelial cells. At pharmacological concentrations retinol slightly increased the intercellular communication in the first 2 h of the exposure period, whereas upon longer treatment times with retinol and retinoic acid, gap-junction-mediated intercellular communication was inhibited almost completely. When retinol was given to tracheal epithelial cells before exposure to CSC or simultaneously with CSC-exposure, retinol counteracted the inhibitory potential of CSC on intercellular communication. The results of the present study clearly indicate that both CSC and all-trans retinol influence the intercellular communication between primary hamster tracheal epithelial cells in serum-free, hormone-supplemented culture medium.

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