Immunohistochemical colocalization of 7B2 and 5HT in the neuroepithelial bodies of the lung of Rana temporaria

Neuroepithelial bodies and solitary neuroendocrine cells in the lungs of amphibia

In the lungs of 12 species of Amphibia investigated so far, solitary neuroendocrine (NE) cells, as well as groups of these cells called "neuroepithelial bodies" (NEB), are observed. They occur in the position strategic to monitoring gas composition, mainly in the ciliated epithelium of the apical part of the septa. A great diversity in the structure of NEB is observed. The NE cells and NEB in Amphibia are predominantly of the "closed type," separated from the air space by a thin cytoplasmic layer of ciliated cells, goblet cells or pneumocytes. In two species, Bufo marinus and Ambystoma tigrinum, the "open type" of NEB occur, where NEB communicate with the air space, by apical cells in Bufo and type II NE cells in Ambystoma. Both types of cells possess single atypical cilia with an 8+1 microtubule arrangement and microvilli on the free surface. Single and grouped NE cells are characterized by small dense core vesicles (DCV) dispersed in the cytoplasm. In Salamandra and Ambystoma the second type of NE cells with large DCV are observed. The DCV represent sites of storage of serotonin and several neuropeptides. The basal parts of NEB and of some solitary cells are invested by the intraepithelial sensory nerve terminals, both afferent and efferent morphologically. In the lungs of Amphibia, similarly to other vertebrates, NE cells, which act as endocrine/paracrine receptors, form epithelial endocrine systems.

Spatial and temporal distribution of 7B2 in the pulmonary diffuse neuroendocrine system of the cat

The postnatal developmental profile of the presence of 7B2 was studied immunocytochemically in the pulmonary diffuse neuroendocrine system of the cat. Labelling was found in neuroepithelial bodies (NEB) but not in solitary neuroendocrine cells. The identity of NEB was confirmed on adjacent serial sections by the immunostaining for protein gene product 9.5, a pan-neuroendocrine marker. The first 3 weeks after birth 7B2 stained NEB were most abundant with a subsequent decline thereafter. The positive correlation between the variation of 7B2 immunoreactivity and number of NEB suggests an important role for 7B2 in NEB.

Immunocytochemical survey of the neuroepithelial endocrine system in the respiratory tract of the Tokyo salamander, Hynobius nebulosus tokyoensis TAgo

The epithelial lining of the respiratory tract of urodeles has been shown to harbor an innervated system of neuroepithelial endocrine (NEE) cells. Even between phylogenetically closely related species, large differences have been reported in the appearance and chemical coding of the NEE system. Although urodeles are well suited for the purpose, none of the prior studies have provided an immunocytochemical survey of the NEE system in all parts of the respiratory tract. In the present study, many bioactive substances and a general marker were immunocytochemically demonstrated in serial sections of the entire respiratory tract of the Tokyo salamander, Hynobius nebulosus tokyoensis, a species in which neuroepithelial bodies (NEBs) were previously characterized at the electron microscopic level. In the current study, serotonin-immunoreactive solitary NEE cells were observed in variable numbers in the larynx, in all parts of the trachea, and in areas of the lungs covered with ciliomucous epithelium. Serotonin-containing NEBs, however, were detected in small cranial areas of the lung only. Solitary NEE cells were seen in the trachea and lungs of H. nebulosus tokyoensis by immunocytochemical staining for somatostatin, calcitonin, calcitonin gene-related peptide, and bombesin, but the number, localization, and appearance of the labeled NEE cells differed considerably. Only calcitonin-like immunoreactivity was also noted in some NEB-like cell clusters in the cranial parts of the lungs. Unlike many other vertebrates, neuron specific enolase was found to be a poor marker for the NEE system in the salamander species used in this investigation. It may be concluded that the NEE system of H. nebulosus tokyoensis contains at least five different bioactive substances.(ABSTRACT TRUNCATED AT 250 WORDS)

7B2 expression in intrapulmonary neuroepithelial bodies: immunocytochemical detection and colocalization with serotonin and calcitonin gene-related peptide

In this study, the occurrence of 7B2, a highly conserved pituitary protein present in many neuroendocrine tissues and tumors, was investigated for the first time in the neuroendocrine cells (NEC) and neuroepithelial bodies (NEB) of hamster, rat and cat lung, as well as its colocalization with serotonin (5-HT) and calcitonin gene-related peptide (CGRP). Bouin fixed and wax embedded lung tissue was serially cut and immunoreactive sites for 7B2, 5-HT and CGRP were demonstrated on adjacent sections with polyclonal rabbit antibodies, using the streptavidin-biotin peroxidase method. 7B2 immunostained NEB were numerous in the intrapulmonary airways and the alveolar parenchyma, always representing a subpopulation of CGRP labelled NEB, but outnumbering those containing 5-HT. NEC, on the other hand, were only immunoreactive for CGRP and 5-HT. Our results suggest that mammalian NEB are storehouses of heterogenous bioactive substances, which may be important components in the development of bronchopulmonary tumors. Moreover, the ubiquitous presence of 7B2 in NEB supports the idea of a pre- and/or post-exocytotic role in the cellular secretory processes while the lack of 7B2 immunoreactivity in NEC might indicate a distinct function for each of both neuroendocrine cell types.