Identification, localization and morphology of APUD cells in gastroenteropancreatic system of stomach-containing teleosts

Equine Stomach Development in the Foetal Period of Prenatal Life-An Immunohistochemical Study

The study consisted of the immunohistochemical analysis of fundic and pyloric mucosa in the equine stomach between the 4th and 11th month of gestation. The accessible material was classified into three age groups using the CRL method. The adult reference group was used to define potential differences between foetal and adult populations of gastric APUD cells. The samples were preserved, prepared, and stained according to the standard protocols. The immunohistochemical reaction was assessed using the semi-quantitative IRS method. The results were documented and statistically analysed. The most significant increase was seen in gastrin (G) cell activity. The activity of other endocrine cells (cholecystokinin (I) cells, somatostatin (D) cells, and somatotropin receptor (SR) cells) was less dynamic. This study proved that the development of APUD cells within the stomach mucosa undergoes quantitative and qualitative changes during stomach development. Our results correspond with the findings described in the accessible literature and prove a strong correlation between morphological changes in the stomach wall and the organ development, growth, and maturation.

Ultrastructure and histochemistry of the subepithelial glands of the nasal septal island in dromedaries with special reference to the possible functions

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The NSI subepithelial glands in dromedaries had unique anatomical features.

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Their ultrastructural features are typical for APUD cells.

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They may have the structures required for synthesis of active peptides, amines and chemical mediators.

The nasal septal island (NSI) is a sensory patch of neuroepithelium located within the soft tissue of the nasal septum in dromedaries. The island has unique anatomical features, including the specialized subepithelial glands. The aim of the present study was to describe the microscopic features and ultrastructure of these subepithelial glands and to speculate the possible functions. A total of 10 camel heads were used for the study. Unlike the serous and mucous airway glands, the NSI glands’ ultrastructural features were typical for cells of the (Amine Precursor Uptake and Decarboxylation, APUD) system. These features were included, membrane bound secretory vesicles of varying electron density, smooth endoplasmic reticulum in the form of vesicles; electron dense mitochondria, abundant rough endoplasmic reticulum and free ribosomes. Alcian-PAS identifiable mucus granules were not observed, except for few clusters of cells, located at the luminal surface. The probable functions were discussed on basis of cellular morphology and context. In a conclusion, the NSI subepithelial glands in dromedaries had unique anatomical structures, and as many other APUD cells, they had the machinery required for synthesis of a variable number of biologically active peptides, amines and chemical mediators.

Mucosal Hallmarks in the Alimentary Canal of Northern Pike Esox lucius (Linnaeus)

Simple Summary

In vertebrates, mucous cells are one of the main cellular components of the gut mucosal system, which secrete different mucin types involved in several functions. Endocrine cells are scattered in the epithelium of the gut mucosa, and they produce and release regulatory molecules affecting food intake and nutrition. The goal of this study was to obtain data on quantitative distribution of mucous and endocrine cell types in the alimentary canal of the northern pike (Esox lucius), using histochemistry and immunofluorescence. In the stomach of pike, there is a high abundance of mixed mucins, with the acid component contributing to the lubrication of mucosae, where they are associated with the rapid passage of digesta through the intestine. Neutral mucins increase in the intestine aborally. The distribution of endocrine cells of the diffuse endocrine system shows the presence of somatostatin and catecholamine-secreting endocrine cells and the lack of gastrin-secreting endocrine cells. We show a close regulatory relation between endocrine and mucous cells of the gut mucosal system involved in the physiology of fish nutrition. Results confirmed the relationship between the carnivorous diet and the gut mucins distribution of northern pike; indeed, our data provide very important information to ichthyologists who study dietary behavior of species.

Abstract

On the basis of trophic behavior, fish are classified as herbivores, carnivores, omnivores, or detritivores. Epithelial mucous cells secrete mucin types specific to diet and digestive function. Mucus secretion is regulated mainly by molecular modulators produced by epithelial endocrine cells in response to luminal or tissue stimuli. These modulators are involved in control of food intake and digestive functions. Immunohistochemical and immunofluorescence studies were conducted on 10 adult northern pike (Esox lucius Linnaeus, 1758) from Lake Piediluco (Central Italy) to quantify distribution of sub-types of mucous and endocrine cells in alimentary mucosal epithelium. Neutral mucins predominated in the esophagus, and mixed and acidic mucins predominated in stomach and intestine. The gastric epithelium contained endocrine cells secreting somatostatin, tyrosine hydroxylase, and substance P. Mucous cells secreting neutral mucins increased in number from proximal to distal intestine, with endocrine cells containing substance P in the proximal intestine and those containing Leu-enkephalin throughout the intestine. Lectin histochemistry of gut sections revealed an abundance of N-acetyl-glucosamine and N-acetyl-galactosamine as carbohydrate residues on the mucin chain. The quantity and content of endocrine and mucous cells in the alimentary canal of E. lucius showed a direct relationship with its diet.

Effects of dietary vitamin E on growth performance as well as intestinal structure and function of channel catfish (Ictalurus punctatus, Rafinesque 1818)

To evaluate the impact of dietary vitamin E supplementation on growth performance, the intestinal structure and function of channel catfish (Ictalurus punctatus, Rafinesque 1818) was investigated. A total of 900 healthy channel catfish (weight, 5.20±0.15 g) were divided into four groups, which received experimental diets with different vitamin E content (0, 50, 100 or 1,000 mg/kg). At the end of the feeding trial (after 15 weeks), the growth and gut performance of the animals was determined. The digestive enzyme activity in hepatopancreas and gut was also detected. In addition, the height of intestinal fold, the thickness of the mucous membrane and the number of somatostatin-positive cells was examined by histological analysis. Dietary vitamin E supplementation at 50 and 100 mg/kg significantly improved the growth and gut performance, which also increased the activity of several digestive enzymes compared to that in animals without vitamin E supplementation (P<0.05). In addition, vitamin E supplementation also significantly increased the height of intestinal fold and the thickness of the mucous membrane (P<0.05). Fish with dietary vitamin E supplementation at appropriate doses also had more somatostatin-positive cells in than those without vitamin E supplementation (P<0.05). In conclusion, dietary vitamin E supplementation at 50 and 100 mg/kg was shown to improve the growth performance as well as intestinal structure and function of channel catfish.

Histochemical and immunohistochemical study on endocrine cells (5HT, GAS, and SST) of the gastrointestinal tract of a teleost, the characin Astyanax bimaculatus

Endocrine cells secrete hormones through the mucosa of the gastrointestinal tract (GIT) and act on the overall regulation of digestive processes such as nutrient absorption, gut motility and intestinal blood flow. This study aimed to determine regional distribution and frequency of endocrine cells secretory of serotonin (5-HT), somatostatin (SST) and gastrin (GAS) in the GIT of a small-bodied widespread characin Astyanax bimaculatus using histological, histochemical and immunohistochemical techniques. Fragments of the stomach and gut fixed for 8h in Bouin liquid were subjected to histological processing and immunohistochemical routine. For the histological analyses, the technique of staining with hematoxylin and eosin (HE) was used, whereas for the histochemical analyses Gomori's trichrome, periodic acid+Schiff (PAS) and Alcian blue pH 2.5 (AB) were used to further immunohistochemical processing. The stomach has a mucosa lined with a simple columnar epithelium with mucus-secreting cells; the glandular region (proximal and distal portions) has folds and pits, whereas the non-glandular region has pits only. The intestinal epithelium is simple with plain cylindrical grooved and goblet cells. The anterior region has thin folds with few goblet cells, and the posterior region with thick folds and many goblet cells. The regional distribution and frequency of endocrine cells varied across regions of the GIT with the stomach showing the highest amount of immunoreactive (IR) cells. Only the 5-HT was found in the stomach (epithelia and glands) and gut regions, with comparatively higher frequency in the stomach. SST-IR cells were found in the stomach (epithelia and gastric glands) with higher frequency in the glandular region, whereas GAS-IR were found in the gastric glands only. The stomach was the only organ to have all the three types of endocrine cells, indicating that this organ is the main site of digestion of food in this species.

Relative distribution of gastrin-, CCK-8-, NPY- and CGRP-immunoreactive cells in the digestive tract of dorado (Salminus brasiliensis)

The endocrine cells (ECs) of the gastrointestinal mucosa form the largest endocrine system in the body, not only in terms of cell numbers but also in terms of the different produced substances. Data describing the association between the relative distributions of the peptide-specific ECs in relation to feeding habits can be useful tools that enable the creation of a general expected pattern of EC distribution. We aimed to investigate the distribution of ECs immunoreactive for the peptides gastrin (GAS), cholecystokinin (CCK-8), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP) in different segments of the digestive tract of carnivorous fish dorado (Salminus brasiliensis) by using immunohistochemistry procedures. The distribution of endocrine cells immunoreactive for gastrin (GAS), cholecystokinin (CCK-8), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP) in digestive tract of dorado S. brasiliensis was examined by immunohistochemistry. The results describe the association between the distribution of the peptide-specific endocrine cells and feeding habits in different carnivorous fish. The largest number of endocrine cells immunoreactive for GAS, CCK-8, and CGRP were found in the pyloric stomach region and the pyloric caeca. However, NPY-immunoreactive endocrine cells were markedly restricted to the midgut. The distribution pattern of endocrine cells identified in S. brasiliensis is similar to that found in other carnivorous fishes.

Immunohistochemical evaluation of the goat forestomach during prenatal development

Here we report the detection and distribution of synaptophysin (SPY), non-neuronal enolase (NNE), glial fibrillary acidic protein (GFAP), vimentin (VIM), neuropeptide Y (NPY), and vasoactive intestinal peptide (VIP) expression in the goat forestomach during prenatal development. A total of 140 embryos and fetuses were examined to evaluate protein expression from the first stage of prenatal life until birth. In all cases, SPY immunoreactivity was detected at 53 days gestation in the lamina propria-submucosa, tunica muscularis, serosa, and myenteric plexuses. Immunoreactivity to NNE was observed at 64 days gestation in the same locations as well as the epithelial layer. Glial cells were found at 64 days as indicated by signals corresponding to GFAP and VIM at 39 days. Positive staining for NPY and VIP was observed at 113, 75, and 95 days in the rumen, reticulum, and omasum, respectively, in the lamina propria-submucosa, tunica muscularis, and myenteric plexuses of each of these gastric compartments. These findings indicate possible preparation of the fetal goat forestomach for postnatal function. Compared to other ruminant species, neuroendocrine cells, glial cells and peptidergic innervations markers were detected earlier compared to sheep but at around the same stage as in deer.

Neuroendocrine system of the digestive tract in Rhamdia quelen juvenile: an immunohistochemical study

In this work, an immunohistochemical study was performed to determine the distribution and relative frequencies of some neuromodulators of the digestive tract of silver catfish (Rhamdia quelen). The digestive tract of silver catfish was divided into six portions; the oesophagus, stomach, intestine (ascendant, descendant and convoluted segments), and rectum. Immunohistochemical method using a pool of specific antisera against-gastrin, -cholecystokinin-8, -leu-enkephalin, -neuropeptide Y, -calcitonin gene-related peptide (CGRP), and -vasoactive intestinal peptide (VIP) was employed. Immunoreactivity to all antisera was identified in neuroendocrine cells (NECs) localized in the gut epithelium, although no reaction was observed in the oesophagus or stomach. The morphology of NECs immunopositive to each antibody was similar. They were slender in shape, with basally located nucleus, and their main axis perpendicular to the basement membrane. The number of NECs immunoreactive to all antisera was higher in the ascendant and descendant intestine, exhibiting a decreasing trend toward distal segments of the gut. In addition, immunoreactivity to CGRP and VIP was observed in the myenteric plexus and nerve fibers distributed in the mucosal, submucosal and muscular layers. The higher number of immunopositive NECs in the ascendant and descendant intestine may indicate the primary role of these segments in the control of food intake by means of orexigenic and anorexigenic peripheral signals.

Histochemical features of the Muscovy duck small intestine during development

We demonstrated for the first time the distribution and morphology of argyrophil and of goblet cells in the mucosa of the small intestine of the Muscovy duck during development using the Grimelius silver staining and alcian blue/periodic acid-Schiff (AB/PAS) staining technique. The argyrophil cells distribution was variable over the length of the small intestine from embryonic day 24 (24E) to post-hatching day 13 (13d). In the villi most argyrophil cells belonged to the open-type, while in the crypts they belonged to the closed-type. In the duodenum the density of argyrophil cells was highest at hatching, while in the jejunum and in the ileum the highest density value was at hatching and 13d. AB/PAS-positive goblet cells appeared on the villi and crypts of the duodenum and jejunum at 30E, and in the ileum at hatching. The density of AB/PAS-positive cells was the highest in the three segments at hatching. The AB-positive cells, compared with the PAS-positive cells, predominated in villi and crypts of the three segments, moreover the rate of AB-positive cells to PAS-positive cells significantly decreased from 30E to 9d. An increase in argyrophil and goblet cells number during the later incubation and at hatching, could indicate the small intestine in that period is being prepared to face a new diet.

An immunohistochemical study of the gut neuroendocrine system in juvenile pejerrey Odontesthes bonariensis (Valenciennes)

In this study, several neuropeptides were identified by immunohistochemistry in neuroendocrine cells (NEC) located in the gut epithelium and nerve cell bodies of the enteric nervous system of pejerrey Odontesthes bonariensis, a species that is a promising candidate for intensive aquaculture. The neuropeptides involved in orexigenic or anorexigenic action, i.e. gastrin, cholecystokinin-8, neuropeptide Y and calcitonin gene-related peptide (CGRP), displayed a significantly higher number of immunoreactive NECs in the anterior intestine, suggesting that this region of the gut plays an important role in the peripheral control of food intake. On the other hand, leu-enkephalin and vasoactive intestinal peptide (VIP), both associated with the modulation of the enteric immune system, showed no significant variations in the mean value of immunopositive NECs between the anterior and posterior intestine. This may indicate that their activity is required at a similar level along the entire gut. In addition, CGRP and VIP-immunoreactive neurons and nerve fibres were observed in the myenteric plexus, which might exert synergistic effects with the neuropeptides immunolocalized in NECs.

Extrapituitary growth hormone

Pituitary somatotrophs secrete growth hormone (GH) into the bloodstream, to act as a hormone at receptor sites in most, if not all, tissues. These endocrine actions of circulating GH are abolished after pituitary ablation or hypophysectomy, indicating its pituitary source. GH gene expression is, however, not confined to the pituitary gland, as it occurs in neural, immune, reproductive, alimentary, and respiratory tissues and in the integumentary, muscular, skeletal, and cardiovascular systems, in which GH may act locally rather than as an endocrine. These actions are likely to be involved in the proliferation and differentiation of cells and tissues prior to the ontogeny of the pituitary gland. They are also likely to complement the endocrine actions of GH and are likely to maintain them after pituitary senescence and the somatopause. Autocrine or paracrine actions of GH are, however, sometimes mediated through different signaling mechanisms to those mediating its endocrine actions and these may promote oncogenesis. Extrapituitary GH may thus be of physiological and pathophysiological significance.

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.

Immunohistochemical study on distribution of endocrine cells in gastrointestinal tract of flower fish (Pseudophoxinus antalyae)

AIM: To detect distribution and relative frequency of endocrine cells in gastrointestinal tract of flower fish (Pseudophoxinus antalyae).

METHODS: The intestinal tract of flower fish was divided into four portions from proximal to distal; the enlarged area after oesophagus and anterior, middle and posterior intestine. Immunohistochemical method using the peroxidase anti-peroxidase complex was employed. All antisera between four portions of flower fish were compared using ANOVA.

RESULTS: Eleven types of gut endocrine cells were determined; they were immunoreactive for calcitonin gene related peptide, substance P, vasoactive intestinal peptide, bombesin, somatostatin-14, secretin, TrkA, TrkB, TrkC, neurotensin, neuropeptide Y, which were found in almost all portions of the gastrointestinal tract.

CONCLUSION: The regional distribution and relative frequency of immunoreactive cells in the flower fish, Pseudophoxinus antalyae, are essentially similar to those of other fish.

Development of the islets, exocrine pancreas, and related ducts in the Nile tilapia, Oreochromis niloticus (Pisces: Cichlidae)

Pancreatic development and the relationship of the islets with the pancreatic, hepatic, and bile ducts were studied in the Nile tilapia, Oreochromis niloticus, from hatching to the onset of maturity at 7 months. The number of islets formed during development was counted, using either serial sections or dithizone staining of isolated islets. There was a general increase in islet number with both age and size. Tilapia housed in individual tanks grew more quickly and had more islets than siblings of the same age left in crowded conditions. The pancreas is a compact organ in early development, and at 1 day posthatch (dph) a single principal islet, positive for all hormones tested (insulin, SST-14, SST-28, glucagon, and PYY), is partially surrounded by exocrine pancreas. However, the exocrine pancreas becomes more disseminated in older fish, following blood vessels along the mesenteries and entering the liver to form a hepatopancreas. The epithelium of the pancreatic duct system from the intercalated ducts to the main duct entering the duodenum was positive for glucagon and SST-14 in 8 and 16 dph tilapia. Individual insulin-immunopositive cells were found in one specimen. At this early stage in development, therefore, the pancreatic duct epithelial cells appear to be pluripotent and may give rise to the small islets found near the pancreatic ducts in 16-37 dph tilapia. Glucagon, SST-14, and some PPY-positive enteroendocrine cells were present in the intestine of the 8 dph larva and in the first part of the intestine of the 16 dph juvenile. Glucagon and SST-14-positive inclusions were found in the apical cytoplasm of the mid-gut epithelium of the 16 dph tilapia. These hormones may have been absorbed from the gut lumen, since they are produced in both the pancreatic ducts and the enteroendocrine cells. At least three hepatic ducts join the cystic duct to form the bile duct, which runs alongside the pancreatic duct to the duodenum.

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Localization of TRAIL/TRAILR in fetal pancreas

AIM: To observe the localization of TRAIL/TRAIR (DR4, DR5, DcR1, DcR2) in the fetal pancreas.

METHODS: Fetal pancreas of 32 wk of pregnancy were obtained from induced abortions, embedded in paraffin, and 4-μm sections were prepared. The localization of TRAIL/TRAILR in fetal pancreas was investigated by fluorescence immunohistochemical method combined with laser scanning confocal microscopy.

RESULTS: TRAIL immunoreactive cells were mainly located on the periphery of the pancreas islets. There were a few DcR1 and DcR2 positive cells whereas there were no immunoreactive cells of DR4 and DR5 in the pancreas islets. In the acini and the ducts of the exocrine pancreas there were no TRAIL/TRAILR immunoreactive cells.

CONCLUSION: This study not only describes the distribution of TRAIL/TRAILR in the fetal pancreas, but also provides a morphological basis for deducing the function of TRAIL/TRAILR in pancreas, suggesting that in normal pancreatic islets, the pancreatic cells are resistant towards apoptosis too.

Localization of neurokinin B receptor in mouse gastrointestinal tract

AIM: To observe the location of neurokinin receptor (NK3r) in the mouse gastrointestinal tract.

METHODS: The abdomens of 8 male Kunming mice were opened under anaesthesia with sodium pentobarbital. The exposed gut organs were kept moisture and temperature at the same time. Then the esophagus, jejulum, ileum, colon, etc were respectively cut and the segments from the stomach to the distal colon were opened along the mesenteric border. A circular 4 mm-6 mm enteric part(pieces of 1 cm² were to be prepared) and mucosa and submucosa were removed, then the longitudinal muscle layer was pulled off from the circular muscle layer under microphotograph. They were rinsed in 50 nmol·L^-1 potassium phosphate-buffered saline(PBS). Immunohistochemistry and immunoreactive fluorescence were used in the staining procedures.

RESULTS: There was not NK3r-Like(-Li) positive material on the smooth muscle cells of the esophagus, stomach, and intestines and other regions. The nerve cell bodies with immunoreactivity for NK3r were mainly distributed in the submucousal nerve plexus or myenteric nerve plexus of the gastrointestinal tract except for the esophagus, stomach and rectum. The reaction product was located on the surface of the nerve cell plasma. It was occasionally observed in the cell plasma endosomes, but was very weakly stained. Among the NK3-like positive neurons in the plexus,the morphological type in many neurons appeared like Dogiel II type cells. Some neuron cell bodies were big, having many profiles, some were long ones or having grading structure. Cell body diameter was about 10 μm-46 μm and 8 μm-42 μm in myenteric plexus and submucous plexus.

CONCLUSION: This study not only described the distribution of neurokinin B receptor in the mouse gut in detail, but also provided a morphological basis for deducing the functional identity of the NK3r-LI immunoreactivity neurons, suggesting the possibility that these neurons were closely related to gastrointestinal tract contraction and relaxing activity.

Distribution of nitric oxide synthase in stomach myenteric plexus of rats

AIM: To study the distribution of nitric oxide synthase (NOS) in rat stomach myenteric plexus.

METHODS: The distribution of NOS in gastric wall was studied in quantity and location by the NADPH-diaphorase (NDP) histochemical staining method and whole mount preparation technique.

RESULTS: NOS was distributed in whole stomach wall, most of them were located in myenteric plexus, and distributed in submucosal plexus. The shape of NOS positive neurons was basically similar, most of them being round and oval in shape. But their density, size and staining intensity varied greatly in the different parts of stomach. The density was 62 ± 38 cells/mm² (antrum), 43 ± 32 cells/mm² (body), and 32 ± 28 cells/mm² (fundus), respectively. The size and staining intensity of NOS positive neurons in the fundus were basically the same, the neurons being large and dark stained, while they were obviously different in antrum. In the body of the stomach, the NOS positive neurons were in an intermediate state from fundus to antrum. There were some beadlike structures which were strung together by NOS positive varicosities in nerve fibers, some were closely adherent to the outer walls of blood vessels.

CONCLUSION: Nitric oxide might be involved in the modulation of motility, secretion and blood circulation of the stomach, and the significant difference of NOS positive neurons in different parts of stomach myenteric plexus may be related to the physiologic function of stomach.