Enteroendocrine cells in the Echinodermata.

Enteroendocrine cells are endocrine-like cells found in the luminal epithelia of the digestive tract. These cells have been described in most animal phyla. In echinoderms, the cells have been described mainly in organisms of the class Asteroidea (sea stars) and Holothuroidea (sea cucumbers). Here, we describe what is known about the enteroendocrine cells of the Echinodermata, including the cell types, their distribution in the digestive tract, their neuropeptide content and their regeneration and compare them to what has been found in other animal species, mainly in vertebrates. We also discuss the newly described view of enteroendocrine cells as chemical sensors of the intestinal lumen and provide some histological evidence that similar functions might be found within the echinoderms. Finally, we describe the temporal regeneration of the enteroendocrine cells in the holothurian intestine.

Immunohistochemical study of the digestive tract of Oligosarcus hepsetus.

AIM: To describe the histology of the digestive tract and to investigate the occurrence of endocrine cells in Oligosarcus hepsetus (O. hepsetus). METHODS: The digestive tract (DT) of O. hepsetus was divided into esophagus, two stomach regions (glandular and non-glandular) and two intestinal regions (anterior and posterior). These specimens were processed by routine histological techniques and stained with hematoxylin-eosin, Gomori's trichrome, periodic acid Schiff (PAS) and Alcian blue (AB). An immunohistochemical method using avidin-biotin-peroxidase was employed. RESULTS: The esophagus is lined with a non-keratinized stratified squamous epithelium that is reactive to PAS and AB. The stomach has a mucosa lined with a simple columnar epithelium with mucus-secreting cells that are reactive only to PAS. The intestine has a simple columnar epithelium with a brush border and goblet cells that are reactive to PAS and AB. Somatostatin, serotonin and cholecystokinin immunoreactive cells were identified throughout the DT. CONCLUSION: This study revealed adaptations for the species' diet and showed that the distribution and relative frequency of immunoreactive cells are similar to those of other fish.

Endocrine cells and nerve ganglia of the small intestine of the Opossum Didelphis aurita Wied-Neuwied, 1826 (Mammalia: Didelphidae).

The nervous and endocrine systems jointly control intestinal movements, secretions of their glands and also participate of the processes of nutrient digestion and absorption. Therefore, the central objective of this study was to verify the existence of a possible relationship between the number of nervous cells and ganglia of the submucosal and myenteric plexuses and the number of endocrine cells in the small intestine of adult D. aurita. The utilized staining techniques were Grimelius, modified Masson-Fontana, direct immunoperoxidase and H-E. Argyrophillic, argentaffin and insulin immunoreactive endocrine cells do not numerically vary between the initial, mid and final regions of the duodenum, jejunum and ileum (P>0.05), except for argyrophillic cells in the jejunum (P>0.05). No numerical relationship has yet been verified between the number of nerve ganglia and endocrine cells, and also between nervous and endocrine cells. We recommended the use of new immunohistochemical techniques to confirm the numerical correlation between the nervous and endocrine systems in the small intestine. The morphology and distribution of endocrine cells and the nerve ganglia studied were similar to those encountered in eutherian mammals.

Distributions of the endocrine cells in the gastrointestinal tract of nectarivorous and sanguivorous bats: a comparative immunocytochemical study.

The present study was conducted to clarify the influence of feeding habits on regional distribution and relative frequency of endocrine cells secreting cholecystokinin (CCK), gastrin (GAS), serotonin (5-HT) and enteroglucagon (GLUC) in the nectarivorous Anoura geoffroyi and Glossophaga soricina and the sanguivorous Desmodus rotundus bats of the Phyllostomidae family, by specific immunohistochemical methods. The regional distribution and frequency of the different types of endocrine cells varied according to their location in the GIT. 5-HT immunoreactive cells (IR), detected throughout the GIT of three bats, were the most predominant gastrointestinal endocrine cells. GAS-IR cells in A. geoffroyi were found at the base of the pyloric gland, while in G. soricina they could also be observed in the middle to basal portions of the gland. GLUC-IR cells were located in the fundic region of A. geoffroyi, G. soricina and D. rotundus. These endocrine cells were more abundant in the sanguivorous bat. In nectarivorous bats were compared to sanguivorous bat, which differ in dietary habits, difference in the distribution and relative frequency of gut endocrine cells would be predicted. The absence of some, and decrease in frequency of other, gastrointestinal endocrine cells may reflect, in part, its interspecies differences or dietary habits.

Immunocytochemical study of gastrintestinal endocrine cells in insectivorous bats (Mammalia: Chiroptera).

The regional distribution and relative frequency of endocrine cells in the stomach and intestine of Phyllostomidae: Lonchorhina aurita and Molossidae: Molossus molossus bats were studied immunohistochemically. Three types of immunoreactive (IR) endocrine cells--to serotonin (5-HT), gastrin (GAS) and enteroglucagon (GLUC)--were found in the gastric mucosa and four types of IR cells were identified in the intestinal mucosa. This study showed an interespecfic difference in the regional distribution and relative frequency of endocrine cells in the Chiropteran alimentary tract.

Immunocytochemical study of gastrintestinal endocrine cells in insectivorous bats (Mammalia: Chiroptera) / Estudo imunocitoquímico das células endócrinas gastrintestinais de morcegos insetívoros (Mammalia: Chiroptera)

The regional distribution and relative frequency of endocrine cells in the stomach and intestine of Phyllostomidae: Lonchorhina aurita and Molossidae: Molossus molossus bats were studied immunohistochemically. Three types of immunoreactive (IR) endocrine cells - to serotonin (5-HT), gastrin (GAS) and enteroglucagon (GLUC) - were found in the gastric mucosa and four types of IR cells were identified in the intestinal mucosa. This study showed an interespecfic difference in the regional distribution and relative frequency of endocrine cells in the Chiropteran alimentary tract.

A distribuição regional e a freqüência relativa das células endócrinas no estômago e intestino dos morcegos insetívoros Phyllostomidae: Lonchorhina aurita e Mormoopidae: Molossus molossus foram estudadas pelo método de imunohistoquímica. Três tipos de células endócrinas imunorreativas (IR) à serotonina (5-HT), gastrina (GAS) e enteroglucagon (GLUC) foram localizadas na mucosa gástrica e quatro tipos de células endócrinas IR à 5-HT, GAS, colecistoquinina (CCK) e GLUC foram identificadas na mucosa intestinal. Este estudo mostrou uma diferença interespecífica na distribuição regional e na freqüência relativa das células endócrinas no trato alimentar de Chiropteros.

Myenteric denervation differentially reduces enteroendocrine serotonin cell population in rats during postnatal development.

The enteric nervous and enteroendocrine systems regulate different processes in the small intestine. Ablation of myenteric plexus with benzalkonium chloride (BAC) stimulates epithelial cell proliferation, whereas endocrine serotonin cells may inhibit the process. To evaluate the connection between the systems and the influence of myenteric plexus on serotoninergic cells in rats during postnatal development, the ileal plexus was partially removed with BAC. Rats were treated at 13 or 21 days and sacrificed after 15 days. The cell bodies of myenteric neurons were stained by beta NADH-diaphorase to detect the extension of denervation. The number of enteroendocrine cells in the ileum was estimated in crypts and villi in paraffin sections immunostained for serotonin. The number of neurons was reduced by 27.6 and 45% in rats treated on the 13th and 21st days, respectively. We tried to establish a correlation of denervation and the serotonin population according to the age of treatment. We observed a reduction of immunolabelled cells in the crypts of rats treated at 13 days, whereas this effect was seen in the villi of rats denervated at 21 days. These results suggest that the enteric nervous system might control the enteroendocrine cell population and this complex mechanism could be correlated to changes in cell proliferation.

Ontogeny of the VIP system in the gastro-intestinal tract of the Axolotl, Ambystoma mexicanum: successive appearance of co-existing PACAP and NOS.

Evidence for the presence and potential co-existence of vasoactive intestinal polypeptide (VIP), pituitary adenylate cyclase-activating polypeptide (PACAP) and nitric oxide synthase (NOS) in gastro-intestinal endocrine cells and/or nerve fibers is conflicting and very few results exist on development. This immunofluorescence study aims to clarify the appearance and localization of VIP, PACAP and NOS in the gastro-intestinal tract of the Axolotl, Ambystoma mexicanum, during ontogeny. VIP-immunoreactivity appeared in nerve fibers as early as on day 3 after hatching likely indicating a particular role, such as a trophic action, of VIP in very early development. PACAP-immunoreactivity was observed 3 days later within the VIP-immunoreactive (-IR) fibers. From this time on, VIP- and PACAP-immunoreactivity exhibited complete co-existence. VIP/PACAP-IR fibers were found throughout the gastro-intestinal tract. They were most prominent in the myenteric plexus and the muscle layers and less frequent in the submucosa. NOS-immunoreactivity appeared as late as at the 1st (64 days) juvenile stage in a subpopulation of the VIP/PACAP-IR fibers that contacted submucosal arteries. We found only very few VIP/PACAP-IR perikarya, indicating that part of the VIP/PACAP-IR fibers is of extrinsic origin. On day 12 and in the 1st and 2nd (104 days) juvenile stage, infrequent PACAP-IR entero-endocrine cells were noted, while neither VIP- nor NOS-immunoreactivity occurred in endocrine cells at any stage of development. The complete coexistence of neuronal PACAP- and VIP-immunoreactivities and their very early appearance in ontogeny may suggest important and coordinated roles of both peptides in the control of Axolotl gastro-intestinal activity, while the VIP/ PACAP/NOS-IR fibers may be involved in the regulation of submucosal blood flow.

Argyrophilic and glucagon-immunoreactive cells in the ileum and colon of the developing opossum Didelphis albiventris (Marsupialia).

The ontogenesis of glucagon-producing cells of the ileum and colon of pouch young and of weaned and adult opossums Didelphis albiventris was studied in comparison with the endocrine argyrophilic cell population development. In the ileum, the mean population of argyrophilic cells/mm(2) increased with ontogenesis from 122.9 +/- 18.7 in the pouch young to 211.4 +/- 48.9 in adult animals, while the number of glucagon-immunoreactive cells/mm(2) remained practically constant, i.e. 29.2 +/- 7.3 in the pouch young and 28.1 +/- 5.0 in the adult animal. In the colon, the population of argyrophilic cells/mm(2) remained constant throughout ontogenesis, i.e. 45.8 +/- 6.2 in the pouch young and 48.9 +/- 10.4 in the adult animals. In turn, the enteroglucagon-producing cells increase in number from 4.5 +/- 2.9 to 14.6 +/- 5.2 cells/mm(2) from the pouch young to the adult. We conclude that the intestinal glucagon-producing cells of D. albiventris present a differentiated development in the ileum and colon. This fact suggests that glucagon-immunoreactive cells may play a distinct role in these segments of the intestine during ontogenesis.

[Intraepithelial enteroendocrine cells in cecum and appendix from ovoalbumin sensitized rabbits]. / Células enteroendocrinas intraepiteliales en ciego y apéndice de conejos sensibilizados con ovoalbumina.

Intraepithelial enteroendocrine cells (IEC) produce peptides which influence motility, secretion and absorption of nutrients. Recently the role of these cells in the immune mucosal system is under study. The aim of the present study was to evaluate the modifications in number of IEC in cecum and appendix from Ovalbumin (OVA) sensitized rabbits. Twenty adult New Zealand rabbits were separated in two groups: Group 1 (G1 = 10) not sensitized normal control. Group 2 (G2 = 10) were sensitized twice intraperitoneally with 70 mg OVA and 30 mg ALUM/ml (aluminium hydroxide). Anti OVA specific IgE was evaluated by means of PCA test (passive cutaneous anaphylaxis). Samples form cecum and appendix were fixed in buffered formaldehyde 10%, paraffin embedded and stained with anti-Chromogranin A for neuroendocrine cells. 400 high power fields were counted in each animal, referred as IEC/100 enterocytes. In cecum surface epithelium and crypt were considered. Surface epithelium, deep crypts and superficial crypts were evaluated in appendix. Results showed in cecum in G1:1,6 IEC/100 enterocytes in surface epithelium and 3/100 in crypts; G2 6 IEC/100 in surface epithelium and 12/100 in crypts. The difference between G1 and G2 was statistically significant (p < 0.05). In appendix surface epithelium from G1 showed 5.2/100 while G2 5.4/100. Superficial crypts 8.5 (G1) and 11.3 (G2) (p < 0.05) and deep crypts 4.9 (G1) and 8.5 (G2) (p < 0.01). The results showed that OVA-sensitized animals presented increment in the number of IEC in surface epithelium and crypts which may indicate a relationship between these cells and rabbit mucosal immune system.