Existence of serotonin and neuropeptides-immunoreactive endocrine cells in the small and large intestines of the mole-rats (Spalax leucodon)

The present study was conducted to clarify the regional distribution and relative frequency of endocrine cells secreting serotonin, substance P (SP), cholecystokinin-8 (CCK-8), vasoactive intestinal polypeptide (VIP) and neurotensin in the small and large intestine of the mole-rats (Spalax leucodon), by specific immunohistochemical methods. In the small and large intestine of mole-rats (Spalax leucodon), serotonin, SP and VIP were identified with various frequencies, but CCK-8 and neurotensin were not observed. Most of the IR cells in the small and large intestine were located in the intestinal crypt and epithelium however, they were more frequency in the intestinal crypt. Serotonin-IR cells were detected throughout the whole intestinal tract, predominantly in the duodenum and colon. SP-IR cells were demonstrated throughout the whole intestinal tract except for the ileum and rectum with highest frequencies in the cecum. VIP-IR cells were found in all parts of the small intestine except for the large intestine.In conclusion, the general distribution patterns and relative frequency of intestinal endocrine cells of the mole-rats (Spalax leucodon) was similar to those of some rodent species. However, some species-dependent unique distributions and frequencies characteristics of endocrine cells were also observed in the present study.     

Bacterial Community Mapping of the Mouse Gastrointestinal Tract

Keeping mammalian gastrointestinal (GI) tract communities in balance is crucial for host health maintenance. However, our understanding of microbial communities in the GI tract is still very limited. In this study, samples taken from the GI tracts of C57BL/6 mice were subjected to 16S rRNA gene sequence-based analysis to examine the characteristic bacterial communities along the mouse GI tract, including those present in the stomach, duodenum, jejunum, ileum, cecum, colon and feces. Further analyses of the 283,234 valid sequences obtained from pyrosequencing revealed that the gastric, duodenal, large intestinal and fecal samples had higher phylogenetic diversity than the jejunum and ileum samples did. The microbial communities found in the small intestine and stomach were different from those seen in the large intestine and fecal samples. A greater proportion of Lactobacillaceae were found in the stomach and small intestine, while a larger proportion of anaerobes such as Bacteroidaceae, Prevotellaceae, Rikenellaceae, Lachnospiraceae, and Ruminococcaceae were found in the large intestine and feces. In addition, inter-mouse variations of microbiota were observed between the large intestinal and fecal samples, which were much smaller than those between the gastric and small intestinal samples. As far as we can ascertain, ours is the first study to systematically characterize bacterial communities from the GI tracts of C57BL/6 mice.     

Distribution of endocrine cells in the digestive tract of Alligator sinensis during the active and hibernating period

The digestive tract is the largest endocrine organ in the body; the distribution pattern of endocrine cells varies with different pathological and physiological states. The aim of the present study was to investigate the distributed density of 5-hydroxytryptamine (5-HT), gastrin (GAS), somatostatin (SS) and vasoactive intestinal peptide (VIP) immunoreactive (IR) cells in the digestive tract of Alligator sinensis during the active and hibernating period by immunohistochemical (IHC) method. The results indicated that 5-HT-IR cells were distributed throughout the entire digestive tract, which were most predominant in duodenum and jejunum. The density increased significantly in stomach and duodenum during hibernation. GAS-IR cells were limited in small stomach and small intestine. The density decreased significantly in small stomach during hibernation, while increased in duodenum. What's more, most of the endocrine cells in duodenum were generally spindle shaped with long cytoplasmic processes ending in the lumen during hibernation. SS-IR cells were limited in stomach and small stomach. The density increased in stomach while decreased in small stomach during hibernation, meanwhile, fewer IR cells occurred in small intestine. VIP-IR cells occurred in stomach and small stomach. The density decreased in small stomach, while increased in stomach during hibernation. These results indicated that the endocrine cells in different parts of digestive tract varied differently during hibernation, their changes were adaptive response to the hibernation.     

Spatial dynamics of the bacterial community structure in the gastrointestinal tract of red kangaroo (<Emphasis Type="Italic">Macropus rufus</Emphasis>)

The quantification and community of bacteria in the gastrointestinal (GI) tract (stomach, jejunum, ileum, cecum, colon and rectum) of red kangaroos (Macropus rufus) were examined by using real-time PCR and paired-end Illumina sequencing. The quantification of bacteria showed that the number of bacteria in jejunum and rectum was significantly lower than that in colon and cecum (P < 0.05). A total of 1,872,590 sequences was remained after quality-filtering and 50,948 OTUs were identified at the 97 % similarity level. The dominant phyla in the GI tract of red kangaroos were identified as Actinobacteria, Bacteroidetes and Firmicutes. At the level of genus, the samples from different parts of GI tract clustered into three groups: stomach, small intestine (jejunum and ileum) and large intestine (cecum and rectum). Prevotella (29.81 %) was the most dominant genus in the stomach and significantly (P < 0.05) higher than that in other parts of GI tract. In the small intestine, Bifidobacterium (33.04, 12.14 %) and Streptococcus (22.90, 19.16 %) were dominant genera. Unclassified Ruminococcaceae was the most dominant family in large intestine and the total relative abundance of unclassified bacteria was above 50 %. In identified genera, Dorea was the most important variable to discriminate large intestine and it was significantly higher in cecum than in stomach, small intestine and colon (P < 0.05). Bifidobacterium (21.89 %) was the only dominant genus in colon. Future work on culture in vitro and genome sequencing of those unidentified bacteria might give us insight into the function of these microorganisms in the GI tract. In addition, the comparison of the bacterial community in the foregut of kangaroos and other herbivores and the rumen might give us insight into the mechanism of fiber degradation and help us exploit approaches to improve the feed efficiency and subsequently, reduce the methane emission from herbivores.     

Immunohistochemical study on the ontogenetic development of the regional distribution of peptide YY, pancreatic polypeptide, and glucagon-like peptide 1 endocrine cells in bovine gastrointestinal tract

The regional distribution and relative frequency of peptide YY (PYY)-, pancreatic polypeptide (PP)-, and glucagon-like peptide 1 (GLP-1)-immunoreactive (IR) cells were determined immunohistochemically in the gastrointestinal tract at seven ontogenetic stages in pre- and postnatal cattle. Different frequencies of PYY-, PP-, and GLP-1-IR cells were found in the intestines at all stages; they were not found in the esophagus and stomach. The frequencies varied depending on the intestinal segment and the developmental stage. The frequencies of PYY- and PP-IR cells were lower in the small intestine and increased from ileum to rectum, whereas GLP-1-IR cells were more numerous in duodenum and jejunum, decreased in ileum and cecum, and increased again in colon and rectum. The frequencies also varied according to pre- and postnatal stages. All three cell types were most numerous in fetus, and decreased in calf and adult groups, indicating that the frequencies of these three types of endocrine cells decrease with postnatal development. The results suggest that these changes vary depending on feeding habits and adaptation of growth, secretion, and motility of intestine at different ontogenetic stages of cattle.     

Immunohistochemical study of the distribution of endocrine cells in the gastrointestinal tract of the camel (Camelus bactrianus)

The regional distribution and relative frequency of endocrine cells in the gastrointestinal tract of the camel, Camelus bactrianus, were investigated using immunohistochemical methods. Ten types of immunoreactive (IR) endocrine cells were identified in this study. Among these cell types, only serotonin- and somatostatin-IR cells were detected in almost all regions of the gastrointestinal tract. Most of the cell types showed peak density in the pyloric gland region. The others showed restricted distribution: gastrin, cholecystokinin (CCK), motilin, bovine pancreatic polypeptide (BPP), and (gastric) substance P in the stomach; gastrin, CCK, BPP, gastric inhibitory polypeptide (GIP), glucagon, peptide tyrosine tyrosine (PYY) and substance P in the small intestine; and CCK, motilin, BPP, and PYY in the large intestine. Fundamentally the distribution pattern of endocrine cells in the gastrointestinal tract of the camel is similar to that of cattle. The distribution and frequency of endocrine cells in the glandular sac region are the same as those of the cardiac gland.     

Anatomy and histology of the gastrointestinal tract of the neo-tropical opossum (Didelphis marsupialis insularis,Allen 1902)

The morphology of the gastrointestinal tract (GI) is a strong indicator of the dietary habits of a species. The goal of this study was to describe the gross and microanatomy of the digestive tract of the neo-tropical opossum (Didelphis marsupialis insularis) and relate them to the animals’ food habits. GI tracts from 12 adult animals were used for this study. Results found the small intestine made up 65.9% of the GI tract, and the stomach was simple with a prominent caecum. Histologically, the oesophageal mucosa was non-keratinized and glands were found throughout the oesophagus. The large intestine showed a great number of goblet cells, the jejunum possessed well-developed villi, and Peyer's patches were absent in the ileum. The absence of keratinization of the epithelial lining of the oesophagus and stomach and a high lymphocytic infiltration throughout the small and large intestine reflected a more carnivorous diet, whereas the presence of a well-developed caecum in the large intestine indicated the ability to digest plant matter. Overall, the morphology of GI tract of D. m. insularis displayed both carnivorous and herbivorous features, allowing us to conclude that it is an omnivorous animal.     

Germination and outgrowth of Bacillus subtilis and Bacillus licheniformis spores in the gastrointestinal tract of pigs

Aims: To determine if orally ingested Bacillus spores used as probiotics or direct‐fed microbial feed additives germinate and the vegetative cells grow in the gastrointestinal (GI) tract. Methods and Results: Three independent experiments were done to determine if spores of Bacillus licheniformis and Bacillus subtilis germinate and grow in the GI tract of pigs. After a 2 weeks spore‐feeding period, spores were detected in all segments of the GI tract. The lowest number of spores was found in the stomach, increasing in the small intestine to approx. 55% of the dietary inclusion. When spores were withdrawn from the feed, faecal excretion of spores reflected the dietary inclusion, but decreased gradually to the background level after 1 week. By containing spores in short, sealed pieces of dialysis membrane that were orally administered to the pigs, both the number of spores and vegetative cells could be determined by flow cytometry. Spores accounted for 72% of the total counts after 4–6 h in the stomach and proximal part of the small intestine. After 24 h, spores constituted only 12% of the total counts in the stomach, caecum, and mid‐colon. Less spores and more vegetative cells were detected after 24 h, but total counts increased only 2·14‐fold compared to time zero. Conclusions: The experiments showed that 70–90% of dietary‐supplemented Bacillus spores germinate in the proximal part of the pig GI tract, and that only limited outgrowth of the vegetative cell population occurs. The two Bacillus strains can temporarily remain in the GI system, but will be unable to permanently colonize the GI tract. Significance and Impact of the Study: A substantial population of growing vegetative cells in the GI tract is not a prerequisite for the mode of action of Bacillus feed additives and probiotics.     

Interstitial cells in the primate gastrointestinal tract

Kit immunohistochemistry and confocal reconstructions have provided detailed 3-dimensional images of ICC networks throughout the gastrointestinal (GI) tract. Morphological criteria have been used to establish that different classes of ICC exist within the GI tract and physiological studies have shown that these classes have distinct physiological roles in GI motility. Structural studies have focused predominately on rodent models and less information is available on whether similar classes of ICC exist within the GI tracts of humans or non-human primates. Using Kit immunohistochemistry and confocal imaging, we examined the 3-dimensional structure of ICC throughout the GI tract of cynomolgus monkeys. Whole or flat mounts and cryostat sections were used to examine ICC networks in the lower esophageal sphincter (LES), stomach, small intestine and colon. Anti-histamine antibodies were used to distinguish ICC from mast cells in the lamina propria. Kit labeling identified complex networks of ICC populations throughout the non-human primate GI tract that have structural characteristics similar to that described for ICC populations in rodent models. ICC-MY formed anastomosing networks in the myenteric plexus region. ICC-IM were interposed between smooth muscle cells in the stomach and colon and were concentrated within the deep muscular plexus (ICC-DMP) of the intestine. ICC-SEP were found in septal regions of the antrum that separated circular muscle bundles. Spindle-shaped histamine⁺ mast cells were found in the lamina propria throughout the GI tract. Since similar sub-populations of ICC exist within the GI tract of primates and rodents and the use of rodents to study the functional roles of different classes of ICC is warranted.     

An immunohistochemical study on the distribution of endocrine cells in the gastrointestinal tract of the musk shrew, Suncus murinus

The endocrine cells in the gastrointestinal tract of the musk shrew were studied immunohistochemically. Eleven kinds of endocrine cells, immunoreactive for serotonin, somatostatin, gastrin, cholecistokinin, gastric inhibitory polypeptide, motilin, secretin, neurotensin, pancreatic glucagon, enteroglucagon and bovine pancreatic polypeptide, were revealed. In the stomach, serotonin-, somatostatin-, gastrin-, pancreatic glucagon- and enteroglucagon-immunoreactive cells were detected. The first three types of cells predominated and were more abundant in the pyloric glands than in the other stomach regions. In the small intestine, all types of endocrine cells were found, each having different distributions and relative frequencies. In the large intestine, 10 types of endocrine cells except cholecystokinin-immunoreactive cells were detected. Serotonin- and bovine pancreatic polypeptide-immunoreactive cells were more numerous in the large intestine than in the small intestine.     

Atropine-induced gastrointestinal cytoprotection dependences to the intact of vagal nerve against indomethacin-induced gastrointestinal mucosal and microvascular damage in rats

The non-steroidal antiinflammatory drugs, such as an indomethacin (IND), cause mucosal ulceration and increase the mucosal vascular permeability in the gastrointestinal (GI) tract. Some exogenous agents, e.g. the atropine, can protect the GI mucosa against these ulcerogenic effects. The gastrointestinal functions and mucosal protection, however, are regulated by the vagal nerve. The aims of this study was to examine the dependence of atropine-induced GI cytoprotection to the vagal innervation against the development of IND-caused ulcers and microvascular damage in the mucosa of stomach and small intestine in rats. METHODS: the observations were carried out on CFY-strain rats. The mucosal damage was produced by subcutaneous administration of IND in a 20 mg/kg dose 24 h prior to the killing of animals at the same time as the start of atropine-application, which was given in a small dose (0.1 mg/kg) every 5 h. The subdiaphragmatic bilateral surgical vagotomy was done 24 h before the experiment. The vascular permeability, indicated by the microvascular endothel damage, was measured by the appearance and concentration of intravenously administered Evans blue into the GI mucosa. The number and severity of mucosal lesions and the Evans blue content of mucosa were determined in the stomach and small intestine. RESULTS: (1) The IND caused mucosal ulcers and Evans blue extravasation into the mucosa of the stomach and small intestine. (2) The IND-induced mucosal ulceration and vascular permeability significantly decreased after atropine-administration in the same parts of GI tract. (3) The extent of cytoprotective effect of atropine against the IND was decreased after bilateral surgical vagotomy. CONCLUSIONS: (1) The IND causes microvascular endothel damage in the stomach and small intestinal. (2) The atropine has a cytoprotective effect in the stomach and small intestine against the aggressive effects of IND without decrease of gastric acid secretion. (3) The intact vagal nerve is necessary to the function of cytoprotective mechanisms of atropine against the IND.     

Structure and Function of the Gastrointestinal Tract of the Green Turtle(Chelonia mydas) Hatchling

The gastrointestinal tracts of four Chelonia mydas hatchlings were examined at the anatomical, histological and ultrastructural level. Our results show that the gastrointestinal tract(GI) is composed by esophagus, stomach, small intestine(SI) and large intestine(LI), and histologically of mucosa, submucosa, muscularis externa(ME) and serosa. The esophagus is marked by conical papillae lined by keratinized stratified squamous epithelium, whereas the remaining GI by simple columnar epithelium; esophageal diverticulum is absent. The stomach covered with mucous granule cells, contains cardia, fundic regions and pylorus, which are separately characterized by cardiac glands, fundic glands and pyloric glands, and have the thickest submucosa and ME of the GI. The ME of the esophagus mainly consist of one layer of circular smooth muscle whereas the rest of GI of two layers, inner circular muscle and outer longitudinal muscle. The SI is slightly longer than the LI and the GI is approximately 5.11 times of the carapace length. The SI is lined with longitudinal zigzag folds and characterized by absorptive cells with longer and denser microvilli, whereas the LI by transversal folds, goblet cells and lymphoid nodules. Only intestinal glands appear in duodenum. Endocrine cells are observed in all sections of the GI and accounted for the largest proportion in duodenum. The results demonstrate a perfect combination of the structure and function of the GI and reveal that the digestion and absorption primarily occurs in the foregut. C. mydas hatchling may prefer carnivorous diet.     

Histological and Histochemical Analysis of the Gastrointestinal Tract of the Common Pipistrelle Bat (Pipistrellus Pipistrellus)

Bats have a very high mass-specific energy demand due to small size and active flight. European bat species are mostly insectivorous and the morphology of the gastrointestinal (GI) tract should be adapted accordingly. This study investigated the general anatomy by histology and the function by analysing carbohydrate distribution in particular of the mucus of the GI tract of the insectivorous bat Pipistrellus pipistrellus. The GI tracts of three individuals were dissected, fixed in formaldehyde, and embedded in paraffin wax. The tissues and cells of the GI tract of P. pipistrellus were analysed by classical (acid alizarin blue, haematoxylin-eosin, and Masson Goldner Trichrome), histochemical (periodic acid-Schiff, Alcian blue at pH 2.5) and lectin histochemical (lectins WGA and HPA) staining procedures. The GI tract of P. pipistrellus is organised into the typical mammalian layers. The short, narrow, and thin-walled esophagus is simple with a folded stratified squamous epithelium without glands but mucous surface cells secreting neutral mucus. The stomach is globular shaped without specialisation. Mucous surface cells produced neutral mucus whereas neck and parietal cells secreted a mixture of neutral and acid mucus. Chief cell surface was positive for N-acetylglucosamine and the cytoplasm for N-acetylgalactosamine residues. The intestine lacked a caecum and appendix. The small intestine was divided into duodenum, jejunum-ileum and ileum-colon. The epithelium consisted of columnar enterocytes and goblet cells. The large intestine is short, only represented by the descending colon-rectum. It lacked villi and the mucosa had only crypts of Lieberkühn. Towards the colon-rectum, goblet cells produced mucus with N-acetylglucosamine residues increasing in acidity except in colon-rectum where acidity was highest in the base of crypts. Along the tube the surface of enterocytes was positive for N-acetylglucosamine and N-acetylgalactosamine. All over the mucus filling the lumen of the GI tract was positive for N-acetylglucosamine and increased in acidity in all parts except of the stomach.In conclusion, the simple GI tract showed an anatomical reduction of tissue enabling for a short retention time and a reduction of the load carried during flight: short GI tract, lack of lymphoid tissue, missing of glands in certain regions, and a distinct pattern of mucus distribution, indicating different physiological functions of these areas. The GI tract of P. pipistrellus was typical for an insectivorous species probably representing the ancestral condition.Key words: Chiroptera, esophagus, glycoconjugates, intestine, lectins, stomach     

Gastrointestinal flora of cotton rats

The gastrointestinal (GI) flora of cotton rats was examined. No lactobacilli were detected in any part of the GI tract. Anaerobes, including Peptococcaceae, Bacteroidaceae, bifidobacteria and eubacteria, were the predominant bacteria in the stomach, small intestine, caecum and faeces. Aerobes and facultative anaerobes, including Enterobacteriaceae and streptococci, were detected at low numbers and very low frequency of occurrence in all parts of the GI tract. Sixty-one isolates of bifidobacteria were recovered from the stomach, small intestine, caecum and faeces of cotton rats. They were identified as Bifidobacterium animalis, B. pseudolongum biovar a and b. The study showed that the GI flora of cotton rats seem to be very different from the GI flora in other rodents.     

Human Gastroenteropancreatic Expression of Melatonin and Its Receptors MT1 and MT2

Background and Aim

The largest source of melatonin, according to animal studies, is the gastrointestinal (GI) tract but this is not yet thoroughly characterized in humans. This study aims to map the expression of melatonin and its two receptors in human GI tract and pancreas using microarray analysis and immunohistochemistry.

Method

Gene expression data from normal intestine and pancreas and inflamed colon tissue due to ulcerative colitis were analyzed for expression of enzymes relevant for serotonin and melatonin production and their receptors. Sections from paraffin-embedded normal tissue from 42 individuals, representing the different parts of the GI tract (n=39) and pancreas (n=3) were studied with immunohistochemistry using antibodies with specificity for melatonin, MT₁ and MT₂ receptors and serotonin.

Results

Enzymes needed for production of melatonin are expressed in both GI tract and pancreas tissue. Strong melatonin immunoreactivity (IR) was seen in enterochromaffin (EC) cells partially co-localized with serotonin IR. Melatonin IR was also seen in pancreas islets. MT₁ and MT₂ IR were both found in the intestinal epithelium, in the submucosal and myenteric plexus, and in vessels in the GI tract as well as in pancreatic islets. MT₁ and MT₂ IR was strongest in the epithelium of the large intestine. In the other cell types, both MT₂ gene expression and IR were generally elevated compared to MT₁. Strong MT₂, IR was noted in EC cells but not MT₁ IR. Changes in gene expression that may result in reduced levels of melatonin were seen in relation to inflammation.

Conclusion

Widespread gastroenteropancreatic expression of melatonin and its receptors in the GI tract and pancreas is in agreement with the multiple roles ascribed to melatonin, which include regulation of gastrointestinal motility, epithelial permeability as well as enteropancreatic cross-talk with plausible impact on metabolic control.     

Difference between the effect of acute and chronic surgical vagotomy on the cytoprotective action of atropine against indomethacin-induced mucosal lesions on the gastrointestinal tract in rats

The cytoprotective effect of a small dose of atropine was proved against the indomethacin (IND)-caused gastrointestinal (GI) mucosal damage. This protective effect of atropine disappeared in the acute phase of surgical vagotomy (ASV) on the vagally-innervated parts of GI tract. The aims of our observations were: 1) to examine the effect of chronic surgical vagotomy (CSV) on the cytoprotective action of atropine in the GI tract; and 2) to compare the effects of ASV and CSV on the GI cytoprotection caused by atropine against IND-induced mucosal damage and vascular permeability in rats. The IND was given s.c. 24 h prior to the killing of the animals in a dose of 20 mg x kg(-1). Bilateral surgical vagotomy or sham operation were carried out 24 h (ASV) or 14 d (CSV) before IND-application. Atropine was given i.p. every 5 h after IND-treatment in a dose of 0.1 mg x kg(-1). The number of macroscopical mucosal ulcerations was noted and its severity was calculated by semiquantitative scale in the stomach, small intestine and three equal parts of colon. Vascular permeability was measured by Evans-blue leakage into the mucosal tissue. It has been found that: 1) Tte small dose of atropine significantly decreased the IND-induced mucosal damage and vascular permeability on the stomach, small intestine and the vascular permeability on the proximal colon; 2) the small dose of atropine did not cause any changes in the appearance of IND-induced mucosal lesions and in Evans blue concentration in the mucosa after ASV, but it significantly decreased the IND-caused mucosal damage and Evans blue concentration in the mucosa of stomach, small intestine and proximal colon after CSV; 3) the IND-induced mucosal damage and vascular permeability treated with atropine (given in cytoprotective dose) were significantly smaller after CSV than that after ASV on the stomach, small intestine and proximal colon. It has been concluded that the intact vagal nerve has an essential role in the appearance of cytoprotective mechanisms of atropine in GI tract.     

The gastrointestinal tract of Adélie penguins – morphology and function

The aim of this study was to provide data on the morphology of the gastrointestinal tract of Adélie penguins (Pygoscelis adeliae). It was found to consist of a long oesophagus, a two-chambered stomach, a small intestine measuring only 5.22body length, two rudimentary caeca and a short colon, typical of carnivorous birds. The stomach comprised a glandular proventriculus and a muscular gizzard that frequently contained grit. An acidic pH was recorded in both chambers. Ultrastructural studies of the small intestinal mucosal membrane revealed epithelial cells with elongated, irregular microvilli and high affinity for toluidine blue, absorptive intestinal epithelial cells and goblet cells. Numerous large lymphocyte-like cells were observed close to the brush border of the epithelium, and empty spaces on the epithelial surface reflected normal cell loss in the small intestine. The rudimentary caeca and colon provide relatively little volume and time for symbiotic bacteria to aid the digestion of crustacean chitin.     

Expression and regulation of α‐transducin in the pig gastrointestinal tract

Taste signalling molecules are found in the gastrointestinal (GI) tract suggesting that they participate to chemosensing. We tested whether fasting and refeeding affect the expression of the taste signalling molecule, α‐transducin (G_αtran), throughout the pig GI tract and the peptide content of G_αtran cells. The highest density of G_αtran‐immunoreactive (IR) cells was in the pylorus, followed by the cardiac mucosa, duodenum, rectum, descending colon, jejunum, caecum, ascending colon and ileum. Most G_αtran‐IR cells contained chromogranin A. In the stomach, many G_αtran‐IR cells contained ghrelin, whereas in the upper small intestine many were gastrin/cholecystokinin‐IR and a few somatostatin‐IR. G_αtran‐IR and G_αgust‐IR colocalized in some cells. Fasting (24 h) resulted in a significant decrease in G_αtran‐IR cells in the cardiac mucosa (29.3 ± 0.8 versus 64.8 ± 1.3, P < 0.05), pylorus (98.8 ± 1.7 versus 190.8 ± 1.9, P < 0.0 l), caecum (8 ± 0.01 versus 15.5 ± 0.5, P < 0.01), descending colon (17.8 ± 0.3 versus 23 ± 0.6, P < 0.05) and rectum (15.3 ± 0.3 versus 27.5 ± 0.7, P < 0.05). Refeeding restored the control level of G_αtran‐IR cells in the cardiac mucosa. In contrast, in the duodenum and jejunum, G_αtran‐IR cells were significantly reduced after refeeding, whereas G_αtran‐IR cells density in the ileum was not changed by fasting/refeeding. These findings provide further support to the concept that taste receptors contribute to luminal chemosensing in the GI tract and suggest they are involved in modulation of food intake and GI function induced by feeding and fasting.     

Histochemical distribution of four types of enzymes and mucous cells in the gastrointestinal tract of reared half‐smooth tongue sole Cynoglossus semilaevis

The histochemical distribution of acid phosphatase (ACP), alkaline phosphatase (ALP), non‐specific esterase (NSE), peroxidase (POD) and mucous‐cell types was evaluated in the gastrointestinal tract of the half‐smooth tongue sole Cynoglossus semilaevis. The enzymes were detected in the entire stretch of the gastrointestinal tract. ACP activity was found in the supranuclear region of enterocytes and the lamina propria of the intestine, as well as the cytoplasm of epithelial cells of the stomach. The staining intensity of ACP in the anterior and posterior intestines was stronger than in the stomach. ALP activity was detected in the striated border of enterocytes and muscularis of the whole intestine, lamina propria and supranuclear cytoplasm of the enterocytes in the anterior intestine, as well as in the blood vessels of the stomach. The staining intensity for ALP in the anterior intestine was stronger than in the posterior segment and the latter was stronger than in the stomach. NSE activity was detected in the cytoplasm of the epithelial cells in the entire gastrointestinal tract, with the anterior intestine showing stronger intensity than the stomach. POD activity was located in the blood cells of the lamina propria of the gastrointestinal tract and the levels in the stomach were similar to the anterior and posterior intestines. Alcian blue (pH 2·5) periodic acid Schiff (AB‐PAS) histochemical results revealed three types of mucous cells in the gastrointestinal tract. Type I cells (PAS+AB‐) were observed among the gastric mucosa columnar cells in the stomach and enterocytes in the basal region of the villi and in the middle and top regions of the intestinal villi. Type II cells (PAS‐AB+) and type III cells (PAS+AB+) were not detected in the stomach but were distributed ubiquitously among enterocytes in the middle and top regions of the intestinal villi.