Lectin histochemistry of epidermal glandular cells in the earthworm Lumbricus terrestris (Annelida Oligochaeta).

Carbohydrate residues were localized in the glandular cells of the epidermis of Lumbricus terrestris by lectin histochemistry. The following biotinylated lectins were used: ConA, PNA, WGA, UEA-I. Each lectin has a specific binding pattern in the epidermal glandular cells. The ConA binding is evident in the orthochromatic mucous cells; PNA in the metachromatic mucous cells; WGA in the neuroendocrine-like cells; UEA-I in the cuticle. The epidermal glandular cells possess specific sites for the different lectins in relation to their functional characteristics. Therefore, these sugar residues indicate different behaviours of the cells in epidermal functions related to ion transport, receptor-secretory processes and defence.

Immunohistochemical localization of calcium-binding proteins (CaBPs) in the epidermis of the earthworm Lumbricus terrestris (Annelida, Oligochaeta).

The present immunohistochemical study provides the first evidence of the presence of calcium-binding proteins (CaBPs) in the epidermis of the earthworm Lumbricus terrestris (Annelida, Oligochaeta) a lower invertebrate. The entire epidermis was labelled for calmodulin which is in agreement with its ubiquitous occurrence. Immunopositivity for calbindin D28K was limited to mucous cells, while that for S-100 protein was present only in neuroendocrine-like small granular cells. Finally, labelling for parvalbumin was specifically present in the subcutaneous nerve plexus. S-100 protein is considered to be a marker of neuroendocrine cells, at least in lower invertebrates such as Annelida. Although calbindin D28K is considered to be a marker of these cells in vertebrates, the same function cannot be attributed in Lumbricus terrestris. However, we can conclude that S-100 protein, as a regulatory protein, is phylogenetically older than calbindin D28K. We assume that the latter has an autoregulatory function in secretory processes. In agreement with previous data, we suggest that small granular cells exert a paracrine action in osmoregulatory and secretory processes.

Immunohistochemical localization of bioactive substances in the epidermis of the earthworm, Lumbricus terrestris (Annelida, oligochaeta).

Serotonin (5HT), endothelin-big (ET-big) and neuron-specific enolase (NSE) are present in some epithelial paraneuronal cells of vertebrates. In the invertebrates, we show for the first time, by immunofluorescence and immunoperoxidase methods, the immunoreactions to antibodies raised to ET, 5-HT and NSE in the epidermis of the Lumbricus terrestris. It is assumed that the reactive cells are small granular cells that may have a paracrine action in the mechanisms of cell proliferation and secretory processes. The function of these bioactive substances in the epidermis of the earthworm awaits investigation. Phylogenetically it is very interesting that paraneuronal-like type of cells appear in such an ancient species of invertebrate which uses the epidermis for various functional activities.

Localization of immunoreactive endothelin in the neuroendocrine cells of fish gill.

Immunohistochemical tests have demonstrated for the first time the presence of endothelins in the neuroendocrine cells of fish gill. We have sought co-localization of endothelins with serotonin and neuropeptides which are regarded as neuroendocrine markers of pulmonary diffuse neuroendocrine systems in higher vertebrates. Regarding their endocrine and paracrine activities in mammals, endothelins are considered as peptide hormones and growth factors regulating respiratory function. The roles of endothelins in the gill await investigation based on the multifunctional organization of this organ.

Cytokeratin type distribution in the skin and gill epithelia of the Indian freshwater catfish, Heteropneustes fossilis as detected by immunohistochemistry.

Based on the general cross-reactivity of the cytokeratins in vertebrates, we describe the immunoreactivity for some mammalian cytokeratins of both the epidermis and gill of H. fossilis. The following monoclonal antibodies, commercially supplied, were tested: K8.13, KL1, AE1 and AE3, which have a wide spectrum of specificity, and LDS-68, M 20, K8.60, KS-B17.2, K4.62, which are more narrowly specific. The reaction of the epithelial cells of the skin to K8.13 was negative in the basal layer, weakly positive in the layers above but strongly positive in some cells of the superficial layer. KL1 was negative in the basal layer, positive in the outer layers. AE1 was strongly positive in the basal layer, negative in the superficial cells. AE3 gave a general but weak reaction in the epithelial cells. K8.60 was negative for the epithelial cells, but reacted positively in the club cells. Club cells also reacted to K8.13 and AE1, and were strongly positive to KL1 and AE3. Goblet mucous cells were negative to all antibodies tested. In the gills, K8.13 labelled cells of both filament and lamellar epithelia. The reaction to AE3 was similar but less intense. KL1 was positive in the basal layer of the filament epithelium but not elsewhere, and K8.60 was negative throughout. AE1 and KS- B17.2 specifically labelled small cells scattered in the filament and lamellar epithelia, which are tentatively identified as neuroendocrine cells.

Ectopic expression of bioactive peptides and serotonin in the sacciform gland cells of teleost skin.

Immunohistochemical methods identified serotonin, and the peptides bombesin and caerulein, in the skin of the teleosts Lepadogaster candollei and Mastacembelus erytrotaenia. In both species, the secretory content of epidermal sacciform cells reacted positively for all three substances. These results are compared with studies on the skin glands of amphibians, which also contain multiple active compounds, and on various neuroendocrine cells of fish. The precise functions of the secretions are not known.

Serotonin-like immunoreactivity in the epidermal club cells of teleost fishes.

The present immunocytochemical study concerns the distribution of serotonin in the epidermis of three species of teleost fish. Serotonin-like immunoreactivity was found in the club cells of Heteropneustes fossilis and Carapus acus but not in those from the sea eel Conger conger. This study is the first immunocytochemical identification of serotonin in the club cells of teleost epidermis. By comparing data from the literature (Zaccone et al. 1986, 1987, 1988) regarding the occurrence of serotonin and GRP/bombesin in the exocrine sacciform gland cells of piscine skin, it is worthy mentioning here that the serotonin contained in the club cells of the species studied may have the ability to affect the pheromonal or other possible functions of these cells. The presence of serotonin in these systems has been correlated with the capacity of the exocrine glands of fish skin to secrete, ectopically, amine messengers in contrast to those produced eutopically i.e. in the neuron-paraneuron system in some vertebrates (Fujita et al. 1988).

Primary nucleolus and amphinucleoli in the oocytes of Patella coerulea L. (Moll. Gast.).

Electron microscope observations show in the primary nucleolus some granulations with dimensions less 70 A than those of the amphinucleoli (90 A). Even though the primary nucleolus has a high RNA content, this has not a very active turnover except at the periphery, probably in relation to the emission of 'daughter-nucleoli'. The amphinucleoli, even though they do not have RNA which is cytochemically discloseable, possess, however, RNA at a very high rate of turnover.

Characteristics of the nucleolini observed under the electron microscope.

Observations with the electron microscope permitted us to ascertain that in molluscs and echnioderms oocytes and in malignat tumour cells, the nucleolini, already seen with the phonton microscope, correspond to the "clear fibrillar zones/. These present fibrils 40-60 A thick, spread throughout a very clear matrix. All around these zones there are other closely thickened and interlacing fibrils.