Immunocytochemical identification and localization of APUD cells in the gut of seven stomachless teleost fishes

Immunohistochemical characterisation of the adult Nothobranchius furzeri intestine

Nothobranchius furzeri is emerging as an exciting vertebrate organism in the field of biomedicine, developmental biology and ecotoxicology research. Its short generation time, compressed lifespan and accelerated ageing make it a versatile model for longitudinal studies with high traceability. Although in recent years the use of this model has increased enormously, there is still little information on the anatomy, morphology and histology of its main organs. In this paper, we present a description of the digestive system of N. furzeri, with emphasis on the intestine. We note that the general architecture of the intestinal tissue is shared with other vertebrates, and includes a folding mucosa, an outer muscle layer and a myenteric plexus. By immunohistochemical analysis, we reveal that the mucosa harbours the same type of epithelial cells observed in mammals, including enterocytes, goblet cells and enteroendocrine cells, and that the myenteric neurons express neurotransmitters common to other species, such as serotonin, substance P and tyrosine hydroxylase. In addition, we detect the presence of a proliferative compartment at the base of the intestinal folds. The description of the normal intestinal morphology provided here constitutes a baseline information to contrast with tissue alterations in future lines of research assessing pathologies, ageing-related diseases or damage caused by toxic agents.

Immunohistochemical investigation of epithelial, mesenchymal, neuroectodermal, immune and endocrine markers in sterlet (Acipenser ruthenus), shortnose sturgeon (Acipenser brevirostrum) and common carp (Cyprinus carpio)

Immunohistochemistry (IHC) is a laboratory method widely used to characterize tissue and cell origin, both in human and veterinary medicine. In fish, however, little is known about staining characteristics of most tissue types, and especially for less studied chondrostean fish. The aim of this study was to examine the specificity of various immunohistochemical markers in tissues of chondrostean and teleostean fish and to validate diagnostic tests. Sterlet (Acipenser ruthenus L.), shortnose sturgeon (Acipenser brevirostrum) and common carp (Cyprinus carpio L.) were examined. Markers were chosen as representatives of epithelial (cytokeratin AE1/AE3), mesenchymal (vimentin), neuroectodermal (S-100 protein), lymphoid (leukocyte common antigen, LCA) and endocrine (thyroglobulin, thyroxin) tissues and organs. Applied antibodies were of monoclonal or polyclonal mammalian origin and primarily intended for human medicine research or diagnostic application. No species differences were obvious while examining sterlet, shortnose sturgeon and carp. Cytokeratin AE1/AE3, vimentin, S-100 protein and thyroxin were positive on targeted tissues and structures. Leukocyte common antigen (LCA) and thyroglobulin were negative on targeted structures, however, and with clear cross-reactivity on non-targeted tissues (vascular wall, granulocytes). Conclusive results were obtained when using polyclonal antibodies with dilution adjusted to laboratory practice, while application of ready-to-use (RTU) kits with pre-diluted antibodies or monoclonal antibodies often showed conflicting or inconclusive results.

Novel Identification and Microscopy of the Intestinal Bulb of Molly Fish (Poecilia sphenops) with a Focus on Its Role in Immunity

The intestinal bulb is a simple dilatation in the anterior part of the intestine of agastric fish. This study was conducted on 18 adult specimens of molly fish (Poecilia sphenops) and demonstrated the presence of an intestinal bulb. The intestinal epithelium was composed of enterocytes covered with microvilli, many mucous goblet cells, and enteroendocrine cells. Numerous intraepithelial lymphocytes, neutrophils, plasma cells, dendritic cells, stem cells, rodlet cells, and macrophages were identified in the epithelial layer. Interestingly, this study recorded the process of autophagy and formation of autophagosomes, multivesicular bodies, and dense bodies. The intestinal epithelium extended into the intestinal gland that consisted of simple columnar epithelium, mucous cells, stem cells, enteroendocrine cells, and basal cells. These glands opened to the lumen of the bulb and were surrounded by a network of telocytes. Moreover, immunohistochemistry revealed that the intestinal epithelium expressed APG5, myostatin, TGF-β, IL-1β, NF-κB, Nrf2, and SOX9. Leukocytes in the lamina propria-submucosa expressed APG5. The inflammatory cells in the connective tissue showed strong immunoreactivity to myostatin and TGF-β. The smooth muscular layer also expressed myostatin. Both IL-1β and NF-κB showed immunoreactivity in macrophages in the lamina propria-submucosa. Stem cells expressed Sox-9 and telocytes expressed NF-κB and SOX9; while astrocytes in the tunica muscularis expressed GFAP. The high frequency of immune cells in the intestinal bulb suggested an immune role of this organ. This is the first study demonstrating the absence of the stomach and its replacement with an intestinal bulb in molly fish, and consequently, this species could be reclassified as agastric fish according to this study.

Microanalysis of the Intestinal Bulb of Grass Carp (Ctenopharyngodon Idella): Histological, Histochemical, Immunohistochemical, and Scanning Electron Microscopical Studies

Cyprinid fishes have one of the simplest types of gastrointestinal tract among vertebrates. Those fish species do not possess a true stomach that is replaced by a simple dilatation at the anterior part of the intestine called the intestinal bulb. Twenty adult specimens of grass carp were used in the present study to identify the cellular components as well as the immunohistochemical and surface architectural characteristics of the intestinal bulb. The mucosa of the intestinal bulb shows numerous, deep longitudinal folds arranged in zigzagging-like patterns. The epithelium is composed mainly of absorptive columnar cells covered by microvilli and mucous goblet cells. Spindle-shaped enteroendocrine cells and some migratory immune cells such as intraepithelial lymphocytes and rodlet cells could be identified between the absorptive cells. The epithelium also contains many secretory granules and large numbers of vacuoles containing digestive enzymes mostly in the basal part. The immunohistochemistry revealed that CD20-positive B-lymphocytes are immunolocalized mainly in the connective tissue core lamina propria of the mucosal folds. However, CD3-immunopositive T-lymphocytes are highly concentrated in the lamina propria. In addition, intraepithelial T-lymphocytes expressed immunopositivity to CD3. The current study presented many types of immune cells and suggests their essential immunological role for the intestinal blub.

The gut-brain axis in vertebrates: implications for food intake regulation

The gut and brain are constantly communicating and influencing each other through neural, endocrine and immune signals in an interaction referred to as the gut-brain axis. Within this communication system, the gastrointestinal tract, including the gut microbiota, sends information on energy status to the brain, which, after integrating these and other inputs, transmits feedback to the gastrointestinal tract. This allows the regulation of food intake and other physiological processes occurring in the gastrointestinal tract, including motility, secretion, digestion and absorption. Although extensive literature is available on the mechanisms governing the communication between the gut and the brain in mammals, studies on this axis in other vertebrates are scarce and often limited to a single species, which may not be representative for obtaining conclusions for an entire group. This Review aims to compile the available information on the gut-brain axis in birds, reptiles, amphibians and fish, with a special focus on its involvement in food intake regulation and, to a lesser extent, in digestive processes. Additionally, we will identify gaps of knowledge that need to be filled in order to better understand the functioning and physiological significance of such an axis in non-mammalian vertebrates.

Daily rhythms of intestinal cholecystokinin and pancreatic proteases activity in Senegalese sole juveniles with diurnal and nocturnal feeding

The influence of diurnal and nocturnal feeding on daily rhythms of gut levels of cholecystokinin (CCK) and the activity of two key pancreatic proteases, trypsin and chymotrypsin, were examined in juveniles of Senegalese sole (Solea senegalensis), a species with nocturnal habits. Four feeding protocols were performed: P1) One morning meal; P2) Six meals during the light period; P3) Six meals during the dark period; and P4) 12 meals during 24 h. Daily activity patterns of both proteases were remarkably similar and showed a high correlation in all the experimental protocols. In P1, daily patterns of CCK and digestive enzymes showed a single maximum. In P2, CCK levels exhibited two peaks. Digestive enzymes activities showed slightly delayed peaks compared to CCK, although their daily fluctuations were not significant. In P3, intestinal CCK concentration exhibited two peaks at the end of light and dark periods, but only the second one was significant. The first maximum level of chymotrypsin activity occurred 4 h after the first CCK peak, while the second one coincided with the second CCK peak. Fluctuations of trypsin activity were not significant. In P4, CCK concentration showed three small peaks. Digestive enzymes daily fluctuations were not significant, although they showed an inverted trend with respect to CCK. The daily pattern of the gut CCK content in our study is in agreement with the anorexigenic function of this hormone. Our results support the existence of a negative feedback regulatory loop between CCK and pancreatic proteolytic enzymes in Senegalese sole juveniles.

Distribution of goblet and endocrine cells in the intestine: A comparative study in Amazonian freshwater Tambaqui and hybrid catfish

Goblet cells (GCs) and endocrine cells (ECs) play an important role in intestine physiology, and few studies currently exist for Amazonian fishes. This study aimed to quantify the distribution of GCs and ECs producing cholecystokinin-8 and neuropeptide Y, assessed by mucin histochemistry and peptides immunohistochemistry, in the intestine of two Amazonian species with different feeding habits Tambaqui (Colossosoma macropomum) and hybrid catfish (Pseudoplatystoma reticulatum × Leiarius marmoratus), an omnivore and carnivore, respectively. A systematic literature review correlating feeding habit and GC and EC distribution was also included to contribute to the comparative study. The results of this study provided novel information about the gut cells of Tambaqui and hybrid catfish. Both, GCs and ECs can be found sweeping the entire intestine of Tambaqui and hybrid catfish although the cells can be more concentrated in certain segments. The GCs and ECs in Tambaqui were more uniformly distributed in the midgut segments (T1, T2, and T3). Unlike, in hybrid catfish GCs were more concentrated in the hindgut (C4) and ECs mainly in the two midgut segments (C1 and C2) of hybrid catfish. Based on the comparison between Tambaqui, hybrid catfish, and other fishes in the literature review, we suggest that cell distribution can be partially explained by feeding habits, carnivorous vs. omnivorous.

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.

Endocrine cells producing peptide hormones in the intestine of Nile tilapia: distribution and effects of feeding and fasting on the cell density

Endocrine cells (ECs) act as a luminal surveillance system responding to either the presence or absence of food in the gut through the secretion of peptide hormones. The aim of this study was to analyze the effects of feeding and fasting on the EC peptide-specific distribution along the intestine of Nile tilapia. We assessed the density of ECs producing gastrin (GAS), cholecystokinin-8 (CCK-8), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP) in nine segments of the intestine using immunohistochemistry. Our results show that ECs immunoreactive to CCK-8, GAS, NPY, and CGRP can be found along all the intestinal segments sampled, from the midgut to hindgut, although differences in their distribution along the gut were observed. Regarding nutrient status, we found that the anterior segments of the midgut seem to be the main site responding to luminal changes in Nile tilapia. The NPY+ and CGRP+ EC densities increased in the fasted group, while the amount of CCK-8+ ECs were higher in the fed group. No effects of fasting or feeding were found in the GAS+ EC densities. Changes in ECs density were found only at the anterior segments of the intestine which may be due to the correlation between vagus nerve anatomy, EC location, and peptide turnover. Lastly, ECs may need to be considered an active cell subpopulation that may adapt and respond to different nutrient status as stimuli. Due to the complexity of the enteroendocrine system and its importance in fish nutrition, much remains to be elucidated and it deserves closer attention.

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.

Effects of Enteromyxum scophthalmi experimental infection on the neuroendocrine system of turbot, Scophthalmus maximus (L.)

Enteromyxum scophthalmi is an intestinal myxosporean parasite responsible for serious outbreaks in turbot Scophthalmus maximus (L.) culture, in North-western Spain. The disease affects the digestive tract, provokes severe catarrhal enteritis, emaciation and high rates of mortality. The digestive parasitization triggers a response with the coordinate participation of immune and neuroendocrine systems through the action of peptides released by enteroendocrine cells and present in nervous elements, acting as neuro-immune modulators. The present study was designed to assess the response of the turbot neuroendocrine system against E. scophthalmi infection. Immunohistochemical tests were applied to sections of the gastrointestinal tract of uninfected and E. scophthalmi-infected turbot to characterize the presence of bombesin (BOM), glucagon (GLUC), somatostatin (SOM), leu-enkephalin (LEU) and met-enkephalin (MET). The occurrence of E. scophthalmi in the turbot gastrointestinal tract increased the number of enteroendocrine cells immunoreactive to SOM, LEU and MET. On the other hand, BOM and GLUC immunoreactive cells were less numerous in the gastrointestinal tract of the parasitized turbot. Scarce immunoreactivity to BOM, GLUC and SOM was observed in nerve fibres and neurons of the myenteric plexus of control and infected fish. The results indicate that E. scophthalmi infection in turbot induced changes in the neuroendocrine system, with the diminution of the anorexigenic peptides BOM and GLUC; the increase of enkephalins, related to pro-inflammatory processes; and the increase of SOM, which may cause inhibitory effects on the immune response, constituting a compensatory mechanism to the exacerbated response observed in E. scophthalmi-infected turbot.

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.

Synthesis, characterization and anti proliferative effect of [Au(en)2]Cl3 and [Au(N-propyl-en)2]Cl3 on human cancer cell lines

Two Au(III) complexes of the type [Au(en)2]Cl3 (2a) and [Au(N-pr-en)2]Cl3 (3a) were synthesized by reacting Auric acid (HAuCl(4)·3H2O) with 2 equiv. ethylenediamine (en) or N-alkyl substituted ethylenediamine ligands. This metallodrug was characterized by various analytical and spectroscopic techniques such as elemental analysis, UV-Vis, Far-IR, 1H NMR and solution 13C as well as solid 13C and 15N NMR. Potentiality of [Au(en)2]Cl3 and [Au(N-pr-en)2]Cl3 as an anti-cancer agent were investigated by measuring some relevant physicochemical and biochemical properties such as stability of Au-N bonds by vibrational stretching from Far IR as well as cytotoxicity and stomach cancer cell inhibiting effect, respectively. The solid-state 15N NMR chemical shift shows that the ligand is strongly bound to gold(III) centre via N atoms. The computational study of 2a shows that the gold coordination sphere adopts distorted square planar geometry with bidentate ethylenediamine ligands acting as a tetradentate chelate. While stable in the solution state, the in vitro biological studies performed with these compounds 2a in solution showed higher activity towards the inhibitory effects of the human cancer cell lines such as prostate cancer (PC-3) and gastric carcinoma (SGC-7901) than that of the N-substituted gold(III) complex (3a). Cytotoxicity of the new compounds has also been estimated in PC-3 and SGC-7901 cells.

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.

Immunocytochemical study of the distribuition of endocrine cells in the pancreas of the Brazilian sparrow species Zonotrichia Capensis Subtorquata (Swaison, 1837)

In the present study, we investigated types of pancreatic endocrine cells and its respective peptides in the Brazilian sparrow species using immunocytochemistry. The use of polyclonal specific antisera for somatostatin, glucagon, avian pancreatic polypeptide (APP), YY polypeptide (PYY) and insulin, revealed a diversified distribution in the pancreas. All these types of immunoreactive cells were observed in the pancreas with different amounts. Insulin- Immunoreactive cells to (B cells) were most numerous, preferably occupying the central place in the pancreatic islets. Somatostatin, PPA, PYY and glucagon immunoreactive cells occurred in a lower frequency in the periphery of pancreatic islets.

Gastroenteropancreatic hormones and metabolism in fish

Metabolism of vertebrates integrates a vast array of systems and processes, including the pursuit and capture of food, feeding and digestion of ingested food, absorption and transport of nutrients, assimilation, partitioning and utilization of energy, and the processing and elimination of wastes. Fish, which are the most diverse group of vertebrates and occupy a wide range of habitats and display numerous life history patterns, have proven to be important models for the study of the structure, biosynthesis, evolution, and function of gastroenteropancreatic (GEP) hormones. Food intake is promoted by galanin, neuropeptide Y, and pancreatic polypeptide (PP), while cholecystokinin (CCK) and glucagon-like peptide-1 (GLP-1) inhibit food intake. Digestion of ingested food is facilitated by CCK, PP, and secretin by coordinating gastrointestinal tract motility and regulation of exocrine secretion. Somatostatins (SS), on the other hand, generally inhibit exocrine secretions. Insulin facilitates assimilation by promoting the uptake of nutrient molecules (e.g., glucose, amino acids, and fatty acids) into cells. Insulin also is generally anabolic and stimulates the synthesis and deposition of energy reserves (e.g., glycogen, triacylglycerol) as well as of proteins, thereby facilitating organismal growth. Insulin-like growth factors (e.g., IGF-1) also promote cell proliferation and organismal growth. Breakdown and mobilization of stored energy reserves is stimulated by glucagon, GLP-1, and SS. Somatostatins also affect metabolism and reproduction via their effects on the thyroid axis as well as growth via effects on growth hormone (GH) release and perhaps directly via modulation of GH sensitivity. Studies in fish have revealed that GEP hormones play an important role in coordinating the various aspects of metabolism with each other and with the physiological and developmental status of the animal as well as with the environment.

Histology of the digestive tract of the freshwater stingray Himantura signifer Compagno and Roberts, 1982 (Elasmobranchii, Dasyatidae)

We investigated the histology and histochemistry (of carbohydrates and proteins) of the digestive tract of the freshwater stingray Himantura signifier. The alimentary tract consists of a mouth, pharynx, esophagus, stomach (with a descending cardiac and ascending pyloric part), anterior intestine (with an initial portion and a spiral intestine) and posterior intestine, ending in a cloaca. Histologically, three layers--mucosa, muscularis and adventitia/serosa--were defined from the mouth to esophagus and in the posterior intestine, whereas in the stomach and anterior intestine four layers were present, including a submucosa. The epithelial lining of mouth, pharynx and cloaca was of the stratified cuboidal type, whereas that of the esophagus and posterior intestine was stratified columnar. The stomach and anterior intestine were lined by a simple columnar epithelium with microvilli. Goblet cells were observed along the alimentary tract, except in the stomach. In the descending cardiac portion of this organ, gastric glands composed of oxyntic, oxyntic-peptic and peptic cells were observed. The anterior intestine presented a spiral valve with 11 folds, formed by mucosa and submucosa. The posterior intestine was particular in displaying a three-layered muscularis. Mucosubstances secreted along the alimentary tract contained both neutral and acid mucins, but in the stomach only neutral mucins were detected. The stomach presented intense protein content in the epithelial lining of the gastric pits. Enteroendocrine cells were identified in the stomach and intestine. Overall, our data offer a baseline for comparative purposes and future detailed ultrastructural and immunohistochemical studies.

Formation of the digestive system in zebrafish: III. Intestinal epithelium morphogenesis

Recent analysis of a novel strain of transgenic zebrafish (gutGFP) has provided a detailed description of the early morphological events that occur during the development of the liver and pancreas. In this paper, we aim to complement these studies by providing an analysis of the morphological events that shape the zebrafish intestinal epithelium. One of our goals is to provide a framework for the future characterization of zebrafish mutant phenotypes in which intestinal epithelial morphogenesis has been disrupted. Our analysis encompasses the period between 26 and 126 h post-fertilization (hpf) and follows the growth, lumen formation and differentiation of a continuous layer of endoderm into a functional intestinal epithelium with three morphologically distinct segments: the intestinal bulb, mid-intestine and posterior intestine. Between 26 hpf and 76 hpf, the entire intestinal endoderm is a highly proliferative organ. To make a lumen, the zebrafish endoderm cells undergo apical membrane biogenesis, adopt a bilayer configuration and form small cavities that coalesce without cell death. Thereafter, the endoderm cells polarize and differentiate into distinct cell lineages. Enteroendocrine cells are distinguished first at 52 hpf in the caudal region of the intestine in a new stable transgenic line, Tg[nkx2.2a:mEGFP]. The differentiation of mucin-containing goblet cells is first evident at 100 hpf and is tightly restricted to a middle segment of the intestine, designated the mid-intestine, that is also demarcated by the presence of enterocytes with large supranuclear vacuoles. Meanwhile, striking expansion of the lumen in the rostral intestine forms the intestinal bulb. Here the epithelium elaborates folds and proliferating cells become progressively restricted to a basal compartment analogous to the crypts of Lieberkühn in mammals. At 126 hpf, the posterior intestine remains an unfolded monolayer of simple columnar epithelium.

Hormonal regulation of the fish gastrointestinal tract

The gastrointestinal tracts (GIT) of fish and other vertebrates are challenged with a diversity of functional demands caused by changes and differences in dietary inputs and environmental conditions. This contribution reviews how hormonal regulation plays an essential role in modulating the GIT functions of fish to match changes in functional demands. Exemplary is how hormones produced by the GIT, the associated organs (e.g., pancreas), and other sources (e.g., hypothalamus, adrenal cortex, thyroid, gonads) modulate the digestive processes (motility, secretion, and nutrient absorption) in response to dietary inputs. Hormones regulate the other GIT functions of osmoregulation (secretion and absorption of electrolytes and water), immunity, endocrine secretions, metabolism, and the elimination of toxic metabolites and environmental contaminants to match changes in environmental conditions and physiological states. Although the regulatory molecules and associated signaling pathways have been conserved during evolution of the vertebrate GIT, the specific responses often vary among fish with different feeding habits and from different environments, and can differ from those described for mammals.

Review article--involvement of gastric APUD cells in chronic renal failure

Uremia leads to a number of metabolic and hormonal disorders induced by renal failure with definite biological and clinical sequels. Most frequently, alimentary disorders are the first to appear, followed by symptoms from other organs and systems. The gastrointestinal tract is a site of synthesis of many compounds that have hormonal or hormonal-like biological activity. These substances are produced by highly-specialised receptor-effector cells, that are dispersed in the gastrointestinal mucosa and classified as APUD cells. The present review is an attempt to make a synthesis of current opinions and views concerning the effect of homeostatic dysfunction of the kidneys on the morphology and action of APUD cells in the stomach.

Effect of apoptosis on gastric adenocarcinoma cell line SGC-7901 induced by cis-9, trans-11-conjugated linoleic acid

AIM

To determine the effect of apoptosis on gastric cancer cells (SGC-7901) induced by cis-9, trans-11-conjugated linoleic acid (c9, t11-CLA) and its possible mechanism in the inhibition of cancer cells growth.

METHODS

Using cell culture, flow cytometery and immunocytochemical techniques, we examined the cell growth, frequency of apoptosis and distribution of cell cycle, expression of ki67, bcl-2, Fas, and c-myc of SGC-7901 cells which were treated with various c9, t11-CLA concentrations (25,50,100 and 200 micromol x L(-1)) of c9, t11-CLA for 24 h and 48 h, with a negative control (0.1 % ethanol).

RESULTS

The growth of SGC-7901 cells was inhibited by c9,t11-CLA. Eight days after treatment with various concentrations of c9,t11-CLA, as mentioned above, the inhibition rates were 5.9 %, 20.2 %,75.6 % and 82.4 %, respectively. The frequency of apoptosis on SGC-7901 cells induced by different concentrations of c9, t11-CLA (except for 25 micromol.L(-1), 24 h) was significantly greater than that in the negative control (P<0.01). To further investigate the influence of the cell cycle progression, we found that apoptosis induced by c9, t11-CLA may be involved in blocking the cell cycle of SGC-7901 cells. Immunocytochemical staining demonstrated that SGC-7901 cells preincubated in media supplemented with different c9, t11-CLA concentrations for various time periods significantly decreased the expressions of ki67 (the expression rates were 18.70-3.20 %, at 24 h and 8.10-0.20 % at 48 h, respectively), bcl-2 (4.30-0.15 % at 24 h and 8.05 %-0 at 48 h), and c-myc (4.85-2.20 % at 24 h and 4.75-0.30 % at 48 h) as compared with those in the controls (the expressions of ki67, bcl-2, and c-myc were 15.1 % at 24 h and 13.5 % at 48 h, 6.80 % at 24 h and 8.00 % at 48 h, 5.50 % at 24 h and 5.30 % at 48 h, respectively) (P<0.01), whereas the expressions of Fas were increased (0.60-2.75 %, 24 h and 0.45-5.95 %, 48 h).

CONCLUSION

The growth and proliferation of SGC-7901 cells are inhibited by c9, t11-CLA via blocking the cell cycle, pathways of bcl-2-associated mitochondria with reduced expression of bcl-2 and Fas-associated death domain protein (FADD) with enhanced expression of Fas. But expression of c-myc on SGC-7901 cells is lower than that in negative control, which needs to be studied further.

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

AIM:To identify the type localization and morphology of APUD endocrine cells in the gastroenteropancreatic (GEP) system of stomach-containing teleosts, and study APUD endocrine system in the stomach, intestine and pancreas of fish species.METHODS:Two kinds of immunocytochemical (ICC) techniques of the streptavidin biotin-peroxidase complex (SABC) and streptavidin-peroxidase (S-P) method were used. The identification, localization and morphology of APUD endocrine cells scattered in the mucosa of digestive tract, intermuscular nerve plexus and glandular body of northern snakehead (Channa argus), ricefield eel (Monopterus albus), yellow catfish (Pelteobagrus fulvidraco), mandarinfish (Siniperca chuatsi), largemouth bass (Micropterus salmoides),oriental sheatfish (Silurus asotus), freshwater pomfret (Colossoma brachypomum) and nile tilapia (Tilapia nilotica) were investigated with 8 kinds of antisera.RESULTS:The positive reaction of 5-hydroxytryptamine (5-HT) immunoreactive endocrine (IRE) cells was found in the digestive tract and glandular body of 8 fish species in different degree.Only a few gastrin (GAS)-IRE cells were seen in C.argus,M.albusand P.fulvidraco. Glucagon (GLU)IRE cells were not found in the digestive tract and glandular body but existed in pancreatic island of most fish species. The positive reaction of growth hormone (GH)IRE cells was found only in pancreatic island of S. Chuatsi and S. Asotus, no positive reaction in the other 6 fish species. Somatostatin (SOM), calcitonin (CAL), neurofilament (NF) and insulin (INS)-IRE cells in the stomach, intestine and pancreas of 8 kinds of fish were different in distribution and types. The distribution of all 8 APUD cells was the most in gastrointestinal epithelium mucosa and then in digestive glands. The positive reaction of SOM and 5-HT-IRE cells was found in intermuscular nerve plexus of intestine of P.fulvidraco and S.chuatsi. Only GH-IRE cells were densely scattered in the pancreatic islands of S.chuatsi and S. asotus, and odd distribution in the pancreas of S. asotus.SOM-IRE cells were distributed in the pancreatic islands of S. asotus, C. Brachypomumand T. nilotica. There were INS-IRE cells in the pancreatic islands of S. chuatsi and S. asolus. Eight kinds of APUD cells had longer cell body and cytoplasmic process when they were located in the gastrointestinal epithelium, and had shorter cell body and cytoplasmic process in the gastric gland, and irregular shape in the esophagus and pancreatic island.CONCLUSION:Eight kinds of IRE cells were identified in the GEP system of stomach-containing teleosts. These endocrine cells were scattered in gastrointestinal mucosa, intermuscular nerve plexus, gland body, pancreatic gland and islands under APUD system. CAL and GH-IRE cells in the pancreatic islands of fishes showed functional diversity for these two hormones. Their morphological feature provides evidence of endocrine-paracrine and endocrine-exocrine acting mode. This research can morphologically prove that the GEP endocrine system of fish (the lowest vertebrate) is almost the same as of mammal and human.