The distribution of endocrine cells along the mouse intestine: A quantitative immunocytochemical study

The topographical distribution of endocrine cells in the crypt and villus epithelium along the length of the mouse intestine was studied. Argyrophil reactivity using the Grimelius stain was used to estimate the total endocrine population of the intestine. Comparisons were then made with the fraction of endocrine cells containing glucagon like material, stained immunocytochemically using rabbit anti-glucagon antisera. A highly significant reduction in the incidence of endocrine cells (argyrophil reactive) from the proximal to distal end of the intestine was noted. However, only 10-30% of these cells contained glucagon like material in the crypts of the duodenum, jejunum and ileum, compared to 30–60% in the crypts of the colon and rectum. The distribution of endocrine cells (argyrophil reactive) was maximal in the lower regions of the proliferative zone of the crypts but showed no significant variation along the length of the villi. Cells containing glucagon like material were also most frequent in the lower regions of the proliferative zone of the crypts, but were not generally found above the botom third of the villi. Each crypt in the small intestine contains between 3 and 5 endocrine cells one of which contained glucagon like immunoreactive material. In the colon and rectum each crypt contains about 6-8 endocrine cells, of which 3–4 contained glucagon like immunoreactive material. These results indicate that a sub-set of cells containing glucagon like material, differentiate early in the lineage of endocrine cells within the proliferative zone of the intestinal crypts.     

An immunocytochemical survey of endocrine cells in the gastrointestinal tract of chicks at hatching

Summary The ultrastructure of the micro-environment of the fully functional rat thymus was studied. The thymus consists of two discrete compartments, viz., an epithelial and a mesenchymal compartment. Thymus fibroblasts/fibrocytes, mast cells and granulocytes, are restricted to the mesenchymal compartment. The thymocyte maturation process seems to occur in the epithelial compartment in a network of reticular epithelial cells. The cortex is finely meshed and filled with proliferating thymocytes and some scattered macrophages. Moreover, in the medulla vacuolated epithelial cells form part of a loosely meshed reticulum which is filled with thymocytes and interdigitating cells (IDCs). IDCs frequently contain Birbeck granules and appear to be phagocytic. Together with macrophages, they probably enter the thymus, predominantly in the cortico-medullary region, and cross the separating wall between the two compartments. Some functional aspects of the non-lymphoid cells and in particular the IDCs, which form the micro-environment of the thymus, are discussed with respect to T-cell development.     

Ontogeny of some endocrine cells of the digestive tract in sea bass (Dicentrarchus labrax): An immunocytochemical study

Serotonin- and ten peptide-immunoreactive (IR) cell types were identified in the digestive tract of sea bass (Dicentrarchus labrax L.) larvae of four morphofunctional phases ranging in age from hatching to 61 days. The sequence of appearance and location of endocrine cells during ontogenetic development of the larvae was determined. The differentiation of endocrine cells followed a distal-proximal gradient in the gut which paralleled the morphofunctional differentiation. Serotonin-IR cells were identified in the last portion of the digestive tract from phase I onwards and in the gastric region from phase III, before these regions were morphofunctionally differentiated; met-enkephalin-IR cells were identified from phase II onwards in both the differentiated rectum and the undifferentiated intestine; cholecystokinin (CCK)- and synthetic human gastrin-34-IR cells were located only in the intestine and first found in the undifferentiated intestine of phase II; human gastrin-17-, peptide YY (PYY)- and neuropeptide Y (NPY)-IR cells appeared in the intestine from phase II and in stomach in phase IV, when it showed gastric glands; pancreatic polypeptide (PP)- and glucagon-IR cells were observed in both intestine and stomach, but insulin- and somatostatin-IR cells only in stomach, from phase III, during which the intestine but not the stomach was differentiated. PP- and PYY-, PP- and glucagon-, and PYY- and glucagon-like immunoreactivities coexisted from their first appearance in some cells of the gut.     

Seasonal changes in the diets of migrant and non-migrant nectarivorous bats as revealed by carbon stable isotope analysis

Three species of nectar-feeding bats migrate from tropical and subtropical Mexico into the Sonoran and Chihuahuan deserts during the spring and summer months. We examined geographic and seasonal changes in the diet of one migrant species, Leptonycteris curasoae, using carbon stable isotope techniques to determine the relative importance of C3 and CAM (Cactaceae, Agavaceae) plants in its diet. We also examined the diet of a non-migratory nectar-feeding bat, Glossophaga soricina, from southern Mexico using the same techniques. We found that L. curasoae feeds extensively or exclusively on CAM plants during migration and in the northern part of its range and feeds mostly on C3 plants in southern Mexico. This bat is a year-round resident on Baja California where it is a CAM specialist. The non-migrant G. soricina feeds mostly on C3 plants year-round. Phenological data suggest that certain species of columnar cacti and at least one group of paniculate Agaves on the Mexican mainland provide a spatio-temporally predictable nectar corridor along which nectarivorous bats may migrate in the spring and fall, respectively. Different flowering schedules of Agaves in Baja California appear to promote year-round dietary specialization and perhaps non-migratory behavior in nectar-feeding bats living there.     

Enriching agroecosystems with fruit-producing tree species favors the abundance and richness of frugivorous and nectarivorous bats in Veracruz, Mexico

We evaluated how the abundance and richness of frugivorous and nectarivorous bat species differs among three types of common agroecosystems (diversified coffee plantations, simple coffee plantations and pastures) in Veracruz, Mexico, that represent a gradient of structural and floristic complexity. Using mixed effects models we demonstrated that both the richness and the total abundance of bats was higher in the diversified coffee plantations. We detected similar patterns on comparing the abundance of the four most abundant bat species. Neither season nor the season-agroecosystem interaction had any effect on the comparisons made. Using multiple regressions we found that the richness of plants that are useful to both people and bats had the most explanatory power for the richness and total abundance of frugivorous and nectarivorous bats, as well as for the abundance of Carollia sowelli, Glossophaga soricina and Sturnira spp. Our results indicate that agroecosystems value for conservation of fruit and nectar-eating bats increases as the fruit-bearing trees increases. For the effective conservation of these guilds of bats in tropical agroecosystems, a strategy of diversification with fruit-bearing species is highly recommended; such a strategy would benefit both agricultural producers and wildlife.     

Influence of feeding habits in the endocrine pancreas of insectivore bat Pteronotus personatus and nectarivore bat Anoura geoffroyi: A comparative stereological and immunohistochemical study

Pteronotus personatus as an insectivore bat and has a diet that consists of a high protein diet, whereas the diet of Anoura geoffroyi, a predominantly nectarivore bat, is rich in simple sugars like sucrose, glucose and fructose. Considering that diet influences the activation of different pathways, which may influence morphological adaptations in the gastrointestinal system, the aim of this study was to compare the morphology of the endocrine pancreas in P. personatus and A. geoffroyi. For this, histological, stereological and immunohistochemical methods were used. In P. personatus, the average diameter of the pancreatic islet was 40.47 μm ± 13.94, while in A. geoffroyi was 88.16 μm ± 36.40. The total number of pancreatic islets in P. personatus was 26150 ± 2346 and in A. geoffroyi was 15970 ± 1666. In P. personatus, the volume density of the pancreatic islets was 3.4%± 2.6, whereas in A. geoffroyi the volume density was 6.1% ± 3.7. In addition, the immunodensity of the α, β and δ cells, in P. personatus was 25.8% ± 11.9, 35.5% ± 13.5, 3.9% ± 0.7, respectively, and in A. geoffroyi was 33.10% ± 12.7, 55.08% ± 7.4, 6.2% ± 4.6, respectively. In conclusion, the results of this study indicate differences in the pancreatic weight/body, weight ratio, diameter and volume density of pancreatic islets and in immunodensity of the β and α cells between both species, which have different dietary habits.     

Contacts between endocrine and exocrine cells in the pancreas

Summary Close contacts between exocrine and endocrine cells were observed in human and rat pancreas. The presence of junctional specializations, including desmosomes, tight and gap junctions, as well as interdigitations between endocrine and exocrine cells, implies that these cells are structurally and functionally associated.     

A cytochemical and immunofluorescence study of endocrine cells in the gut of the ascidian Styela clava

Summary Strong secretin-like immunofluorescence has been demonstrated in endocrine-like cells from the gastric epithelium of Styela. These cells also stain with lead haematoxylin and exhibit a brilliant formaldehyde-induced fluorescence, but do not show any other cytochemical features characteristic of the mammalian APUD series. Tests with antisera to glucagon, gastrin and somatostatin all proved negative. In the oesophagus tests with all four antisera proved negative. The significance of these results is discussed in relation to the phylogeny of vertebrate gastro-intestinal hormones.     

Immunocytochemical study of the lung of domestic fowl and pigeon: endocrine cells and nerves

the presence of endocrine cells and nerves in the lung of 2 avian species (Gallus gallus and Columba livia domestica) has been studied by peroxidase-antiper-oxidase (PAP) and avidin-biotin complex (ABC) immunocytochemical methods at the light-microscopic level. Two immunoreactive cell-types have been identified in the epithelium of the primary and secondary bronchi of chick lung: serotonin- and bombesin-immunoreactive cells; and 3 cell-types, namely, serotonin-, bombesin- and CGRP-(calcitonin gene related peptide) immunoreactive cells, have been located in the bronchial epithelium of pigeon lung. Co-localization of 2 different immunoreactivities within the same cell has not been detected. VIP-immunoreactive nerves have been observed in different locations in chick lung.     

Regulatory peptides in the gastrointestinal tract of Alligator mississipiensis

Summary The gastrointestinal tract of the alligator Alligator mississipiensis has been investigated for the presence of immunoreactivity to fourteen regulatory peptides all known to occur in the mammalian gut system.Mucosal endocrine cells reacting specifically with the antisera to neurotensin, C-terminal gastrin, somatostatin, bombesin, secretin, pancreatic glucagon and enteroglucagon were detectable, the distribution of these cells being, in general, similar to the mammalian pattern. Peripheral nerve cell bodies and nerve fibres were detected with the antisera to vasoactive intestinal polypeptide, substance P, bombesin and somatostatin again with a distribution similar to that seen in mammals.No immunoreactivity was observed with the available antisera to glicentin, motilin, gastric inhibitory polypeptide, gastrin 34, cholecystokinin 9–20 and met-enkephalin.     

Ultrastructure of midgut endocrine cells in the adult mosquito, Aedes aegypti

The ultrastructure of endocrine cells in the midgut of the adult mosquito, Aedes aegypti, resembled that of endocrine cells in the vertebrate gastro-intestinal tract. Midgut endocrine cells, positioned basally in the epithelium as single cells, were cone-shaped and smaller than the columnar digestive cells. The most distinctive characteristic of endocrine cells was numerous round secretory granules along the lateral and basal plasma membranes where contents of the granules were released by exocytosis. Secretory granules in each individual cell were exclusively of one type, either solid or 'haloed', and for all cells observed, the range in granule diameter was 60-120 nm. The cytoplasm varied in density from clear to dark. Lamellar bodies were prominent in the apical and lateral cellular regions and did not exhibit acid phosphatase activity. The basal plasma membrane was smooth adjacent to the basal lamina, whereas in digestive cells the membrane formed a labyrinth. Some endocrine cells reached the midgut lumen and were capped by microvilli; a system of vesicles and tubules extended from beneath the microvilli to the cell body. An estimated 500 endocrine cells were distributed in both the thoracic and abdominal regions of the adult midgut. In one midgut, we classified a sample of endocrine cells according to cytoplasmic density and granule type and size; endocrine cells with certain types of granules had specific distributions within the midgut.     

The distribution of endocrine cells along the mouse small intestine

The topographical distribution and incidence of endocrine cells in the crypt and villus epithelium and along the length of the mouse intestine was studied. Cells containing somatostatin and bombesin like reactivity were stained by immunocytochemical techniques using polyclonal antiserum. Most of the somatostatin cells were found in the duodenum, jejunum and ileum, and these cells were generally more frequent on the villus compared to the crypts. This may indicate that the somatostatin cells develop late in the endocrine cell lineage. Bombesin like cells were rare in occurence, and were only present in measureable numbers in the ileum, where they were observed in the crypt and villi. The application of ELISA assays to determine the specificity of the antisera for these peptides is also discussed.     

Chromogranin A in the human gastrointestinal tract: an immunocytochemical study with region-specific antibodies.

We studied the immunoreactivity of 12 different region-specific antibodies to the chromogranin A (CgA) molecule in the various neuroendocrine cell types of the human gastrointestinal (GI) tract by using double immunofluorescence techniques. These staining results were compared with others obtained with a commercial monoclonal CgA antibody (LK2H10). G (gastrin)-cells showed immunoreactivity to virtually all region-specific antibodies, but with varying frequency. Most intestinal EC (enterochromaffin)- and L (enteroglucagon)-cells were immunoreactive to the antibodies to the N-terminal and mid-portion of the CgA molecule, whereas the EC-cells in the stomach reacted with fewer region-specific antibodies. D (somatostatin)-cells reacted to the CgA 411-424 antibody and only occasionally showed immunoreactivity to the other CgA antibodies. A larger cytoplasmic area was stained with the antibodies to CgA 17-38 and 176-195 than with the other antibodies tested. These differences in staining pattern may reflect different cleavage of the CgA molecule in different cell types and at different regions of the GI tract.     

An immunohistochemical study on the distribution of endocrine cells in the chicken gastrointestinal tract

The distribution and the frequency of occurrence of nine types of gut endocrine cells were revealed using immunohistochemical methods in eight portions from the gastrointestinal tract of the chicken (Gallus gallus var domestica). In the proventriculus, somatostatin- and gastrin-releasing polypeptide (GRP)-immunoreactive cells were commonly found. Serotonin-, pancreatic glucagon-, and enteroglucagon-immunoreactive cells were uncommon. Avian pancreatic polypeptide (APP)-immunoreactive cells were rare. In the gizzard, numerous GRP-, and a small number of somatostatin-immunoreactive cells were observed. The pyloric region was characterized by the presence of abundant gastrin-, somatostatin-, and neurotensin-immunoreactive cells. Numerous serotonin-immunoreactive cells were detected in all portions of the intestine. Moderate numbers of neurotensin-immunoreactive cells were detected in all portions of the intestine except for the cecum. A few gastrin- and somatostatin-immunoreactive cells were detected in the duodenum and jejunum. A small number of pancreatic glucagon-immunoreactive cells were detected in the jejunum and ileum. Enteroglucagon-immunoreactive cells were detected in the small intestine in increasing numbers forwards the ileum. Motilin-immunoreactive cells were rare in the small intestine.     

Immunohistochemical localization of neurotensin in endocrine cells of the gut

Summary Endocrine cells displaying neurotensin immunoreactivity are found scattered in the jejuno-ileum of all mammals studied, including man. They are rather scarce in rat, guinea pig, rabbit and pig and fairly numerous in cat, dog and man. In most mammals the neurotensin cells predominate on the villi. Only in the dog are they more numerous in the crypts. In the chicken, neurotensin cells occur all along the intestinal tract. They are particularly numerous in the zone that joins the gizzard with the duodenum. The ontogeny of the neurotensin cells in the gut was studied in rats and chickens. In the rat, the cells are first observed in the jejuno-ileum immediately before birth. The adult frequency is reached 4–5 days later. In the chicken, neurotensin cells first appear in the colon in the 18 day old embryo and in the small intestine two days later (i.e. one or two days before hatching). A few days after hatching, the gut has achieved the adult number of neurotensin cells per unit area.     

An immunocytochemical study of the endocrine pancreas in the Australian fat-tailed dunnart (Sminthopsis crassicaudata)

Summary The endocrine pancreas of the Australian fattailed dunnart, Sminthopsis crassicaudata, was investigated by means of electron-microscopic immunocytochemistry using the protein A-gold technique on London resin (LR) white-embedded tissue. The primary antibodies used were raised against insulin, glucagon, somatostatin and pancreatic polypeptide. The morphology of the secretory granules differed in the four cell types. The insulin cells are pleomorphic, and the secretory granules composed of an electron-dense core surrounded by an electron-lucen halo. The glucago cells possess granules with an electron-dense core usually surrounded by a halo of less dense granular material. Somatostatin cells have large, less dense secretory granules. The pancreatic polypeptide cells show small, dense secretory granules. In order for an ultrastructural study to be considered reliable for the definite identification of endocrine cell types, it is essential that it be corroborated by immunocytochemical data at the light-or preferably electron-microscopic level. Recent developments in immuno-electron-microscopic techniques have contributed to a better knowledge of cells responsible for the secretion of a wide variety of hormones, as in this study.     

Ultrastructural and cytochemical studies on the cytodifferentiation of duodenal endocrine cells

Summary The development and cytodifferentiation of endocrine cells that produce the gastrointestinal hormones gastrin, cholecystokinin and secretin have been studied by a combined fluorescence-cytochemical, immunocytochemical and ultrastructural approach. The results show that, during development, several ultrastructurally distinct cell types exhibit COOH-terminal gastrin and cholecystokinin immunoreactivity. Furthermore, some cells simultaneously contain both gastrin- and cholecystokinin-specific antigenic determinants. Studies on the time course of development of gastrin and cholecystokinin cells, together with the above-mentioned data, suggest that gastrin cells may be converted into cholecystokinin cells in development. During this period, gastrin, cholecystokinin and secretin cells store the biogenic monoamine, 5-hydroxytryptamine a feature not displayed by the adult counter-parts of these cells. In the adult duodenum, characteristic enterochromaffin (EC) cells store 5-hydroxytryptamin for which, evidence for a possible hormonal role has been presented. Taken together, our data indicate that the differentiation of duodenal endocrine cells occurs in distinct steps, each involving a restriction in the biosynthetic repertoire of the cell.     

Glucagon- and glicentin-immunoreactive cells in the human digestive tract

Summary The distribution and cellular location of substances reacting with anti-glucagon or anti-glicentin sera, i.e., glucagon-like and glicentin-like immunoreactivities, were studied in the human digestive tract using the immunofluorescence and immunoperoxidase methods. Both types of immunoreactivity were (1) absent in the antrum, (2) abundant in cells located at the periphery of pancreatic islets, (3) unevenly present in cells scattered in the epithelium of the small intestinal mucosa, the glicentin-immunoreactive cells being particularly abundant in the ileum. In the pancreas, and, when simultaneously present, in the intestine, both glucagon and glicentin immunoreactivities were located in the same cells.The precise ultrastructural location of each immunoreactivity was readily made using colloidal gold and ferritin tracers on ultrathin sections of glutaraldehyde-osmium fixed and epoxy resin-embedded tissues. In the pancreas, both glucagon and glicentin immunoreactivities were found in the granules of the A-type cells; the glucagon immunoreactivity was only present in the core of the granule, whereas the glicentin immunoreactivity was found either in the peripheral halo only, or throughout the entire granule. In the small intestine, both immunoreactivities were located inside the granules of the L-type cells.Quantitative specificity tests suggested that the glucagon- and the glicentin-like substances of the pancreas differ from those found in the intestine.Work supported by INSERM, A.T.P. number: 167539     

Expression of preproVIP-derived peptides in the human gastrointestinal tract: a biochemical and immunocytochemical study

In order to study biosynthetic processing of the precursor for vasoactive intestinal peptide (preproVIP) in the human gut we have developed antisera against the five functional domains of the precursor molecule: preproVIP 22-79, peptide histidine methionine (PHM), preproVIP 111-122, VIP and preproVIP 156-170. The antisera were used to quantify and characterize VIP-precursor peptides by radioimmunoassay (RIA) together with high-pressure liquid Uchromatography (HPLC) and to examine their cellular localization and colocalization by immunocytochemistry. All five peptides were expressed but not in equimolar amounts as expected from the amino acid sequence of the precursor. However, the ratios between them were fairly constant throughout the gastrointestinal tract. The only exceptions were the lower concentrations of PHM and preproVIP 111-122 in the gastric antrum which could be explained by the presence of PHV (the C-terminally extended form of PHM which includes preproVIP 111-122) in large concentrations in this region. It was also found that the C-terminal lysine residue of preproVIP is not removed during processing. Immunocytochemically all preproVIP-derived peptides were shown in neuronal elements. They had a similar distribution throughout the gut suggesting coexistence, a finding which was supported by doublestaining. The findings indicate that differences in the posttranslational processing of preproVIP exist in subpopulations of neurons in the human gut.     

Distribution of peptide-containing neurons and endocrine cells in the rabbit gastrointestinal tract,with particular reference to the mucosa

Summary The distribution patterns of peptide-containing neurons and endocrine cells were mapped in sections of oesophagus, stomach, small intestine and large intestine of the rabbit, by use of standard immunohistochemical techniques. Whole mounts of separated layers of ileum were similarly examined. Antibodies raised against vasoactive intestinal peptide (VIP), substance P (SP), somatostatin (SOM), neuropeptide Y (NPY), enkephalins (ENK) and gastrin-releasing peptide (GRP) were used, and for each of these antisera distinct populations of immunoreactive (IR) nerve fibres were observed. Endocrine cells were labelled by the SP, SOM or NPY antisera in some regions.VIP-IR nerve fibres were common in each layer throughout the gastrointestinal tract. With the exception of the oesophagus, GRP-IR nerve fibres also occurred in each layer of the gastrointestinal tract; they formed a particularly rich network in the mucosa of the stomach and small intestine. Fewer nerve fibres containing NPY-IR or SOM-IR were seen in all areas. SOM-IR nerve fibres were very scarce in the circular and longitudinal muscle layers of each area and were absent from the gastric mucosa. The SP-IR innervation of the external musculature and ganglionated plexuses in most regions was rather extensive, whereas the mucosa was only very sparsely innervated. ENK-IR nerve fibres were extremely rare or absent from the mucosa of all areas, although immunoreactive nerve fibres were found in other layers.These studies illustrate the differences in distribution patterns of peptide-containing nerve fibres and endocrine cells along the gastrointestinal tract of the rabbit and also show that there are some marked differences in these patterns, in comparison with other mammalian species.