Immunohistochemical localization of (neuro)peptide hormones in endocrine cells and nerves of the gut of a stomachless teleost fish,Barbus conchonius (Cyprinidae)

Summary Enteroendocrine cells containing glucagon-, substance P-, neurotensin- and VIP-like substances have been demonstrated immunocytochemically in the gut of Barbus conchonius. Mainly based on the distribution of the immunoreactive endocrine cells in this and a previous^* study, at least eight different enteroendocrine cell types appear to be present in this stomachless fish: 1. C-terminal-gastrinimmunoreactive cells^*, predominantly present in the upper parts of the folds of the proximal part of the intestinal bulb. 2. Metenkephalin-immunoreactive cells^*, basally located in the folds of the first segment. 3. Pancreatic polypeptide (PP)-immunoreactive cells^*, mainly present in the first half of the first segment. 4. Glucagon-like-immunoreactive (GLI) cells that are basally located in the folds of the first segment and that contain a different polypeptide (possibly glicentin) than pancreatic glucagon cells. 5. Substance P-immunoreactive cells, present in the upper parts of the folds throughout the gut. 6. C-terminal-neurotensin-immunoreactive cells, basally located in the folds throughout the first segment. 7. Vasoactive intestinal polypeptide (VIP)-immunoreactive cells, present in small numbers in the proximal part of the intestinal bulb. 8. Nonspecifically-immunoreactive cells^*, found throughout the intestinal bulb. Many VIP-immunoreactive nerves have been demonstrated in the smooth muscle layer and myenteric plexus of the gut; furthermore some of them are peptide histidineisoleucine (PHI)-immunoreactive. Substance P-, somatostatin-, neurotensin- and met-enkephalin-immunoreactive nerves are also found. Thus, at least partial sequences of four different mammalian neuropeptide hormones (VIP, substance P, neurotensin, met-enkephalin) occur both in endocrine cells and enteric nerves of the gut of B. conchonius.     

Immunocytochemical localisation of the icosapeptide fragment of the PP precursor: a marker for ‘true’ PP cells?

Antisera were raised against the icosapeptide fragment of the pancreatic polypeptide (PP) isolated from the canine pancreas. They were used for the immunocytochemical study of the cellular localisation and distribution of the icosapeptide in the gut and pancreas of various mammals. The results indicate that PP and the icosapeptide coexist in the majority of the PP-immunoreactive cells in the pancreas of cat, dog, pig, monkey and man and in all the PP-immunoreactive cells in the stomach of the cat and dog. The icosapeptide does not seem to occur in cells or nerves containing PP-related peptides, such as peptide YY or neuropeptide Y. PP-immunoreactive cells devoid of the icosapeptide could be demonstrated in the large intestine. These cells are probably distinct from the pancreatic PP cell type, and the PP-immunoreactive material probably represents the homologous peptide YY rather than PP. The present findings support the view that the icosapeptide is part of the PP precursor and hence, only the cells containing immunoreactive icosapeptide in addition to immunoreactive PP are to be considered ‘true’ PP cells. The icosapeptide antisera did not stain PP cells in mouse, rat and guinea-pig, suggesting marked species variation in the amino acid sequence of the icosapeptide portion of the PP precursor.     

Immunocytochemical studies on the pancreatic endocrine cells in the Japanese newt (Cynopus pyrrhogaster)]

Pancreatic endocrine cells were examined by light and electron microscopic immunocytochemistry to discuss the co-localization of peptides in one cell type. A cells were irregular in shape with an occasional long cytoplasmic process, and contained glucagon-immunoreactive granules with various contours. These granules were 160-300nm in diameter with various density, and also immunoreactive to anti-human pancreatic polypeptide (PP) serum. A part of them were further immunoreactive to anti-somatostatin serum. B cells were round to elliptical in shape, and often aggregated around the capillaries. Granules of B cells were round to irregular in shape, 270-410 nm in diameter, and immunoreactive to anti-insulin serum. D cells were irregular in shape with meager cytoplasm, and contained somatostatin-immunoreactive granules. These granules were ovoid or teardrop in shape, 140-250nm in longitudinal diameter, and immunoreactive to both anti-somatostatin and anti-human PP sera. PP cells were round to spindle-shaped, and contained human PP-immunoreactive round granules 150-35nm in diameter. These findings reveal the existence of at least 4 types of endocrine cells secreting glucagon, insulin, somatostatin, and PP, respectively, in the newt pancreas, and suggest the co-localization of some of these peptides in one cell type.     

Energy homeostasis and gastrointestinal endocrine differentiation do not require the anorectic hormone peptide YY

The gastrointestinal hormone peptide YY is a potent inhibitor of food intake and is expressed early during differentiation of intestinal and pancreatic endocrine cells. In order to better understand the role of peptide YY in energy homeostasis and development, we created mice with a targeted deletion of the peptide YY gene. All intestinal and pancreatic endocrine cells developed normally in the absence of peptide YY with the exception of pancreatic polypeptide (PP) cells, indicating that peptide YY expression was not required for terminal differentiation. We used recombination-based cell lineage trace to determine if peptide YY cells were progenitors for gastrointestinal endocrine cells. Peptide YY(+) cells gave rise to all L-type enteroendocrine cells and to islet partial differential and PP cells. In the pancreas, approximately 40% of pancreatic alpha and rare beta cells arose from peptide YY(+) cells, suggesting that most beta cells and surprisingly the majority of alpha cells are not descendants of peptide YY(+)/glucagon-positive/insulin-positive cells that appear during early pancreagenesis. Despite the anorectic effects of exogenous peptide YY(3-36) following intraperitoneal administration, mice lacking peptide YY showed normal growth, food intake, energy expenditure, and responsiveness to peptide YY(3-36). These observations suggest that targeted disruption of the peptide YY gene does not perturb terminal endocrine cell differentiation or the control of food intake and energy homeostasis.     

The distribution and ontogeny of polypeptide YY (PYY)-and pancreatic polypeptide (PP)-immunoreactive cells in the gastrointestinal tract of rat

Summary The distribution and ontogeny of polypeptide YY (PYY)-and pancreatic polypeptide (PP)-immunoreactive cells in the gastrointestinal tract of rat were investigated. PYY-immunoreactive cells were numerous in the pylorus, ileum and colon and only a few cells were observed in the corpus, duodenum, jejunum and rectum. On the other hand, a few PP-immunoreactive cells were seen in the colon only. Both PYY-and PP-immunoreactive cells were of the open type, i.e., they extended from the basal lamina to the gut lumen. PYY-immunoreactive cells were observed first in the lower half of the stomach and in the intestine of 19 day-old embryo. The localization of the cells seemed to move along towards the pylorus and the lower part of the intestine. PP-immunoreactive cells could only be detected for the first time in the colon of 2 day-old rat. These cells appeared temporarily in the pylorus and rectum during the period 7 to 21 days after birth. It was concluded that the difference between PYY-and PP-immunoreactive cells in the distribution, frequency and ontogeny provide further evidence that PYY and PP occur in two independent cell types.     

An immunohistochemical study of pancreatic endocrine cells in SKH-1 hairless mice

The regional distribution and frequency of the pancreatic endocrine cells in the SKH-1 hairless mouse were studied by an immunohistochemical (peroxidase anti-peroxidase; PAP) method using four types of specific antisera against insulin, glucagon, somatostatin and human pancreatic polypeptide (PP). The pancreas of mice were divided into three portions; pancreatic islets, exocrine and pancreatic ducts. The pancreatic islets were further subdivided into three regions (central, mantle and peripheral region) according to their located types of immunoreactive cells. In the pancreatic islet portions, insulin-immunoreactive cells were located in the central and mantle regions with 84.60 +/- 7.65 and 33.00 +/- 12.45/100 cells frequencies, respectively, but most of somatostatin-, glucagon- and PP-immunoreactive cells were detected in the mantle and peripheral regions. In the mantle region, somatostatin-, glucagon- and PP-immunoreactive cells were demonstrated with 28.70 +/- 9.91, 52.00 +/- 14.05 and 2.60 +/- 1.51/100 cells frequencies, respectively, and showed 6.20 +/- 2.86, 15.30 +/- 5.31 and 21.50 +/- 10.28/100 cells frequencies, respectively in peripheral regions. However, glucagon-immunoreactive cells were also demonstrated in the central regions with 4.00 +/- 2.83/100 cells frequency. In the exocrine portions, insulin-, glucagon-, somatostatin- and PP-immunoreactive cells were demonstrated in the SKH-1 mouse with 0.90 +/- 0.74, 0.80 +/- 0.79,4.90 +/- 3.54 and 2.70 +/- 1.34/100 cells frequencies, respectively. In the pancreatic duct portions, insulin-, glucagon- and somatostatin-immunoreactive cells were demonstrated in the subepithelial connective tissues and showed islet-like appearances with 30.30 +/- 14.67, 2.70 +/- 3.13 and 5.90 +/- 4.23/100 cells frequencies, respectively. However, no PP-immunoreactive cells were demonstrated in these regions. In conclusion, some peculiar distributional patterns of pancreatic endocrine cells were found in the SKH-1 hairless mouse.     

Some peptide-like colocalizations in endocrine cells of the pyloric caeca and the intestine of Oncorhynchus mykiss (Teleostei)

Summary The coexistence of immunoreactivities to cholecystokinin, glucagon, glucagon-like peptide 1, salmon pancreatic polypeptide, neuropeptide tyrosine, and peptide tyrosine tyrosine was studied immunocytochemicaly, revealing for the first time in fish intestine the existence in the same cell of immunoreactivities to cholecystokinin-glucagon/glucagon-like peptide 1, cholecystokinin-salmon pancreatic polypeptide, glucagon/glucagon-like peptide 1-salmon pancreatic polypeptide, glucagon/glucagon-like peptide 1-neuropeptide tyrosine, salmon pancreatic polypeptide tyrosine tyrosine, and glucagon/glucagon-like peptide 1-peptide tyrosine tyrosine. Colocalization of cholecystokinin-salmon pancreatic polypeptide was observed only in the pyloric caeca of the rainbow trout Oncorhynchus mykiss, while the other colocalizations also occurred in proximal and middle intestinal segments. In all cases, endocrine cells immunoreactive to only one of the paired antisera were detected except for anti-glucagon and anti-glucagon-like peptide 1, which always immunostained the same cells.     

Immunocytochemical identification of polypeptide YY (PYY) cells in the human gastrointestinal tract

Various parts of the human gastrointestinal tract were investigated immunocytochemically for the occurrence of polypeptide YY (PYY) and pancreatic polypeptide (PP). PYY-immunoreactive cells were observed in the lower part of the ileum, in the colon and in the rectum, and PP-immunoreactive cells were found in the colon and rectum. Both cell types were of the open type, i.e. they extended from the basal lamina to the gut lumen. PYY-immunoreactive cells were seen to emit cytoplasmic processes to the neighbouring goblet cells. This latter observation suggests that PYY cells may exert a paracrine action on the mucus-secreting goblet cells. Staining of consecutive thin plastic sections and staining of the same section simultaneously for two peptides showed that PYY-immunoreactivity did not occur in PP- or enteroglucagon-immunoreactive cells. On the ultrastructural level PYY-immunoreactivity was localized in basal granulated endocrine cells. These cells contained round or slightly oval electron dense granules with a mean diameter of 150 nm (range 100-300 nm).     

Immunocytochemical investigation of the gastro-entero-pancreatic (GEP) neurohormonal peptides in the pancreas and gastrointestinal tract of the dogfish Squalus acanthias

The pancreas and gastrointestinal tract (GIT) of adults and of an embryonic stage of 11 cm long (about half the length of newborn fish) of the spiny dogfish, Squalus acanthias, were investigated immunocytochemically for the occurrence of the gastro-entero-pancreatic (GEP) neurohormonal peptides. In the pancreas of adult forms 5 endocrine cell types were seen, namely insulin-, somatostatin-, glucagon-, pancreatic polypeptide (PP)- and gastric inhibitory peptide (GIP)-immunoreactive cells. These cell types form scattered islets and were seen sometimes to surround small ducts. GIP-immunoreactivity cells did not occur in glucagon-containing cells. In the mucosa of GIT of adults 18 endocrine cell types were observed, viz. insulin-, somatostatin-, glucagon-, glicentin, PP-, polypeptide YY (PYY)-, vasoactive intestinal polypeptide (VIP)-, GIP-, gastrin C-terminus, CCK-, neurotensin N-terminus-, bombesin/gastrin releasing peptide (GRP)-, substance P-, enkephalin-, alpha-endorphin, beta-endorphin-, serotonin- and calcitonin immunoreactive cells. These cells occurred mostly in the intestine. All these cell types were of the open type, except glucagon- and glicentin-immunoreactive cells in the stomach, which seemed to be of the closed type. In the muscle layers and the submucosa, VIP and substance P- immunoreactive nerves and neurons were observed. In the pancreas of the dogfish embryo only 3 endocrine cell types could be demonstrated, namely insulin-, somatostatin- and glucagon-immunoreactive cells. In the mucosa of the GIT of the embryos studied 12 endocrine cell types were detected, viz. insulin-, somatostatin-, glucagon-, PP-, PYY-, VIP, GIP, gastrin C-terminus-, CCK-, neurotensin N-terminus-, enkephalin- and serotonin immunoreactive cells. The number of these cells, except that of PYY-immunoreactive cells, was lower than that of adults and in some cases their distribution did not correspond with that of adults.     

Histological and immunohistochemical studies of the endocrine cells of the gastrointestinal mucosa of the toad (Bufo regularis)

Summary Using histological and immunhistochemical techniques, nine endocrine cell types were observed in the mucosa of the gastrointestinal tract of the toad,Bufo regularis, viz. enterochromaffin, somatostatin, glucagon, pancreatic polypeptide (PP), secretin, gastric inhibitory peptide (GIP), gastrin-C-terminal pentapeptide (GTPP), neurotensin and bombesin cells. The enterochromaffin cells were distributed throughout the gastrointestinal tract except the rectum. Somatostatin, glucagon, PP, secretin, GIP and GTPP cells were observed both in the ileum and bombesin cells only in the pyloric and antral parts of the stomach. Immunostaining of consecutive sections did not reveal more than one polypeptide hormone in any of these cell types. It is concluded from the present results that the toad gastrointestinal mucosa contains endocrine cell types that are more or less homologous to those in the mammal alimentary tract, though some of them exhibit a different topographic distribution.     

Endocrine cells and nerves in the stomach of the lizard Podarcis hispanica detected by immunocytochemistry

The general identification of endocrine cells in the stomach of the lizard Podarcis hispanica was carried out by their response to the Grimelius and Masson-Fontana techniques. 11 immunoreactive cell-types, positive for chromogranin-, serotonin-, caerulein/gastrin/ cholecystokinin (CAER/G/CCK)-, glucagon-like-peptide-1 (GLP-1)-. glucagon-, bombesin-,somatostatin-, pancreatic polypeptide (PP)-, peptide tyrosine tyrosine (PYY)-, neurotensin-and calcitonin gene related peptide (CGRP)- antisera were detected by immunocytochemical methods. Co-existence of glucagon with GLP-1, and PP with PYY were observed in some cells. Furthermore, immunoreactivities for members of gastrin and PP families were also found to co-exist in a few cells. In the muscular layer, vasoactive intestinal peptide (VIP)- and substance P-immunoreactive nerve fibers were also found.     

Ultrastructural characterization of 6 immunoreactive enteroendocrine cells in Barbus conchonius (Teleostei,cyprinidae)

Summary Using the semi-thin/ultra-thin technique six different immunoreactive endocrine cell types are ultrastructurally identified in 0.5% glutaraldehyde fixed gut of B. conchonius. In addition two of them (gastrin-and PP-immunoreactive cells) are also characterized with the immunogold method, showing that the immunoreactivity is only restricted to the secretory granules. Size distribution histograms and the average diameters of 30% (d30) of the largest granules are given, showing a gradual increase in granule size from unspecific immunoreactive cells, (d30=110 nm) via gastrin-(119 nm), VIP-like-(127 nm), met-enkephalin-(143 nm) and PP-(174 nm) to glucagon-immunoreactive cells (178 nm). The presence of PP-and glucagon-immunoreactivity in the same cells and the consequence for their granule size is discussed. In the distal part of the gut endocrine cells are found showing no immunoreactivity with the antisera used; their granules (d30=144 nm) were, although not significantly, larger then those of VIP-like-immunoreactive cells, also found in that part of the gut. It is supposed that they represent substance P-immunoreactive cells. Unfortanately, secretory granules of several cell types showed about 20% more shrinkage in 0.5% glutaraldehyde fixed tissue, than in osmicated tissue.     

The endocrine cells in the gastroenteropancreatic system of the bowfin, Amia calva L.: an immunohistochemical, ultrastructural, and immunocytochemical analysis.

The gastroenteropancreatic (GEP) endocrine system of bowfin (Amia calva) was described using light and electron microscopy and immunological methods. The islet organ (endocrine pancreas) consists of diffusely scattered, mostly small islets and isolated patches of cells among and within the exocrine acini. The islets are composed of abundant, centrally located B cells immunoreactive to bovine and lamprey insulin antisera and D cells showing a widespread distribution and specificity to somatostatin antibodies. A and F cells are present at the very periphery of the islets and are immunoreactive with antisera against glucagon (and glucagon-like peptide) and several peptides of the pancreatic polypeptide (PP)-family, respectively. The peptides of the two families usually collocates within the same peripheral islet cells and are the most common immunoreactive peptides present in the extra-islet tissue. Immunocytochemistry and fine structural observations characterised the granule morphology for B and D cells and identified two cell types with granules immunoreactive to glucagon antisera. These two putative A cells had similar granules, which were distinct from either B or D cells, but one of the cells had rod-shaped cytoplasmic inclusions within cisternae of what appeared to be rough endoplasmic reticulum. The inclusions were not immunoreactive to either insulin or glucagon antisera. Only small numbers of cells in the stomach and intestine immunoreacted to antisera against somatostatin, glucagon, and PP-family peptides. The paucity of these cells was reflected in the low concentrations of these peptides in intestinal extracts. The GEP system of bowfin is not unlike that of other actinopterygian fishes, but there are some marked differences that may reflect the antiquity of this system and/or may be a consequence of the ontogeny of this system in this species.     

The distribution of polypeptide YY (PYY)- and pancreatic polypeptide (PP)-immunoreactive cells in the domestic fowl

Summary The distribution of the polypeptide which has an N-terminal tyrosine and a C-terminal tyrosine (PYY)- and pancreatic polypeptide (PP)-immunoreactive cells were investigated in the gut of the domestic fowl. PYY-immunoreactive cells were observed in the duodenum and jejunum. PP-immunoreactive cells were seen in the duodenum, jejunum, ileum and colon. Both PYY- and PP-immunoreactive cells were extended from the basal lamina to the gut lumen i.e. of open type. PYY-immunoreactive cells occurred mainly in the basal and middle portion of the villi. On the other hand, PP-immunoreactive cells were located mostly in the crepts. The occurrence of PYY-immunoreactive cells in the upper part of the small intestine is rather similar to that of amphibians and reptiles, than to that of mammals, where PYY-immunoreactive cells are located in the distal part of the small intestine and in the large intestine.Preliminary results were given in abstract form in the 4th International Symposium on Gastrointestinal Hormones, held in Stockholm, June 20–23, 1982     

Histological and immunohistochemical studies of the endocrine cells of the gastrointestinal mucosa of the toad (Bufo regularis)

Using histological and immunhistochemical techniques, nine endocrine cell types were observed in the mucosa of the gastrointestinal tract of the toad, Bufo regularis, viz. enterochromaffin, somatostatin, glucagon, pancreatic polypeptide (PP), secretin, gastric inhibitory peptide (GIP), gastrin-C-terminal pentapeptide (GTPP), neurotensin and bombesin cells. The enterochromaffin cells were distributed throughout the gastrointestinal tract except the rectum. Somatostatin, glucagon, PP, secretin, GIP and GTPP cells were observed both in the stomach and in the small intestine. Neurotensin cells were seen only in the ileum and bombesin cells only in the pyloric and antral parts of the stomach. Immunostaining of consecutive sections did not reveal more than one polypeptide hormone in any of these cell types. It is concluded from the present results that the toad gastrointestinal mucosa contains endocrine cell types that are more or less homologous to those in the mammal alimentary tract, though some of them exhibit a different topographic distribution.     

Ontogeny and distribution of certain endocrine cells in the human fetal large intestine

Summary In 9 fetuses, 9 to 24 weeks-old, the occurrence and relative distribution of argentaffin cells, as well as of cells immunoreactive to somatostatin (SRIF), glucagon-like polypeptide (GLI), pancreatic polypeptide (PP) and substance P (SP) were studied in five segments of the colon (appendix, cecum, ascending colon, descending colon, and rectosigmoid). For each colonic segment, data concerned with the occurrence of endocrine cells were expressed either as mean absolute numbers of specific cells per entire mucosal section, or as cell densities per mm³ of mucosa after calculation of the mucosal volume of the sections. Argentaffin, GLI, SRIF and PP immunoreactive cells are all present in relatively large numbers, scattered along the entire length of the colonic mucosa as early as the 9th–10th week of gestation, whereas substance P-containing cells occur sporadically and first appear during the 14th–17th week. Until the 20th week, with progressing embryonic development, an increase was determined in absolute numbers per section of all types of endocrine cells in all segments of the colon. This observation is clearly related to the general growth of the colonic mucosa, since cell densities per mm³ of mucosa do not greatly change or even decrease during gestation. However, it is possible that densities of argentaffin, GLI and BPP cells increase in the appendix around the 14th–17th week of gestation. Between the 20th and 24th week, absolute numbers of cells per section remain stable or slightly increase, while cell densities tend rather to decrease in all segments. These data demonstrate that some endocrine cells are present very early in the human fetal colon, but their functional significance remains to be elucidated.This work was supported by the Institut National de la Santé et de la Recherche Médicale (INSERM)     

Immunocytochemical investigation of the gastro-enteropancreatic (GEP) neurohormonal peptides in the pancreas and gastrointestinal tract of the dogfishSqualus acanthias

Summary The pancreas and gastrointestinal tract (GIT) of adults and of an embryonic stage of 11 cm long (about half the length of newborn fish) of the spiny dogfish,Squalus acanthias, were investigated immunocytochemically for the occurrence of the gastro-entero-pancreatic (GEP) neurohormonal peptides. In the pancreas of adult forms 5 endocrine cell types were seen, namely insulin-, somatostatin-, glucagon-, pancreatic polypeptide (PP)- and gastric inhibitory peptide (GIP)-immunoreactive cells. These cell types form scatterd islets and were seen sometimes to surround small ducts. GIP-immunoreactivity cells did not occur in glucagon-containing cells. In the mucosa of GIT of adults 18 endocrine cell types were observed, viz. insulin-, somatostatin-, glucagon-, glicentin-, PP-, polypeptide YY (PYY)-, vasoactive intestinal polypeptide (VIP)-, GIP-, gastrin C-terminus, CCK-, neurotensin N-terminus-, bombesin/gastrin releasing peptide (GRP)-, substance P-, enkephalin-, -endorphin, -endorphin-, serotonin- and calcitonin immunoreactive cells. These cells occurred mostly in the intestine. All these cell types were of the open type, except glucagon- and glicentin-immunoreactive cells in the stomach, which seemed to be of the closed type. In the muscle layers and the submucosa, VIP and substance P-immunoreactive nerves and neurons were observed. In the pancreas of the dogfish embryo only 3 endocrine cell types could be demonstrated, namely insulin-, somatostatin- and glucagon-immunoreactive cells. In the mucosa of the GIT of the embryos studied 12 endocrine cell types were detected, viz. insulin-, somatostatin-, glucagon-, PP-, PYY-, VIP, GIP, gastrin C-terminus-, CCK-, neurotensin N-terminus-, enkephalin- and serotonin immunoreactive cells. The number of these cells, except that of PYY-immunoreactive cells, was lower than that of adults and in some cases their distribution did not correspond with that of adults.     

Immunocytochemical demonstration of vertebrate neuropeptides in the earthworm Lumbricus terrestris (Annelida,Oligochaeta)

Summary The localisation and distribution of 10 vertebrate-derived neuropeptides in the earthworm, Lumbricus terrestris, have been determined by an indirect immunofluorescence technique. The peptides are pancreatic polypeptide (PP), peptide tyrosine tyrosine (PYY), neuropeptide Y (NPY), glucagon (C-terminal), vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine (PHI), gastrinreleasing peptide (GRP), calcitonin gene-related peptide (CGRP), neurotensin (NT), and met-enkephalin. For 6 of the peptides — PYY, NPY, PHI, glucagon, GRP and CGRP — this is the first demonstration of their presence in any annelid, and NT has not previously been described in an oligochaete. Cell bodies and nerve fibres immunoreactive to the 10 peptides occur throughout the CNS. In the PNS, epidermal sensory cells displayed immunoreactivities to PP and PYY, and PP-, PYY-, NPY-, PHI- and GRP-like immunoreactivities occurred in nerve fibres supplying the main body muscles. Nerve fibres immunoreactive to PP and PYY are also associated with the innervation of the gut (pharynx, oesophageal glands, and mid and posterior regions of the intestine). No endocrine cells immunoreactive for any of the antisera tested could be identified in the gut epithelium, suggesting that dual location of peptides in the brain and gut epithelium is a phenomenon that occurred at a later stage in evolution. No immunoreactive elements were detected in any of the organs and ducts of the reproductive and excretory systems.     

Evidence for somatostatin,gastrin and pancreatic polypeptide-like substances in the mucosa cells of the gut in fishes with and without stomach

Gastrin, pancreatic polypeptide and somatostatin immunoreactive cells in the gut of two fish with stomachs (perch and catfish) and a stomachless fish (carp) were studied by immunocytochemistry. In the gastric mucosa of perch and catfish, cells showing gastrin and somatostatin-like immunoreactivity are found, scattered among the surface mucous cells and mucous neck cells. No pancreatic polypeptide (P.P.) immunoreactive cells are detected in the gastric mucosa. Cells showing gastrin and P.P.-like immunoreactivity are observed in the intestinal mucosa of perch, catfish and carp. In this location no somatostatin immunoreactive cells are found.