Immunohistochemical localization of chromogranin A and B in the endocrine cells of the alimentary tract of the green frog, Rana esculenta

An immunohistochemical study of the pancreatic endocrine cells of the Korean golden frog, Rana plancyi chosenica

The regional distribution and quantitative frequency of pancreatic endocrine cells were demonstrated in the Korean golden frog (Rana plancyi chosenica Okada), which is known as a Korean endemic species, for the first time by immunohistochemical methods using specific mammalian antisera to insulin, glucagon, somatostatin and human pancreatic polypeptide (PP). In the pancreas of the Korean golden frog, all four endocrine cell types were demonstrated. Insulin- and glucagon-positive cells were located in the pancreas as single cells or islet-like clusters, respectively. Somatostatin-containing cells were also dispersed in the pancreas as single cells or clusters but in the case of clusters, they are exclusively situated in the marginal regions of insulin- or glucagon-positive cell clusters. PP-containing cells were also distributed as single cells or clusters. Clusters consisted of PP-positive cells are distributed as a core type and a marginally distributed type. Overall, there were 40.84±3.81% insulin-, 26.02±1.71% glucagon-, 7.63±2.09% somatostatin- and 25.51±3.26% PP-IR cells.

Regional distribution and relative frequency of gastrointestinal endocrine cells in the ddN mice: an immunohistochemical study

The distributions and frequencies of some endocrine cells in the eight portions of the gastrointestinal (GI) tract - fundus, pylorus, duodenum, jejunum, ileum, cecum, colon and rectum of the ddN mouse, were studied with immunohistochemical method using seven types of antisera against chromogranin (Cg) A serotonin, somatostatin, glucagon, gastrin, cholecystokinin (CCK)-8 and human pancreatic polypeptide (hPP). In the GI tract of ddN mice, CgA, serotonin, somatostatin, glucagon, gastrin, CCK-8 immunoreactive (IR) cells were identified with various frequencies, but hPP-IR cells were not observed in this study. Most of IR cells in the intestinal portion were generally spherical or spindle in shape (open type cell) whereas cells showing round in shape (close type cell) were found in the intestinal gland and stomach regions occasionally. They showed the highest frequency in the pylorus or colon. CgA-IR cells were observed from the pylorus to ileum. Serotonin-IR cells were detected throughout the whole GI tract except for the fundus. Somatostatin-IR cells were demonstrated throughout the whole GI tract except for the cecum and colon. Gastrin and CCK-8-IR cells were restricted to the pylorus and duodenum. In addition, a few glucagon-IR cells were restricted to the fundus and rectum. In conclusion, the general distribution patterns and relative frequency of GI endocrine cells of the ddN mouse was similar to that of other strains of mice. However, some strain and/or species-dependent unique distributions and frequencies of endocrine cells were also observed in the present study.

Immunocytochemical study of gastrintestinal endocrine cells in insectivorous bats (Mammalia: Chiroptera)

The regional distribution and relative frequency of endocrine cells in the stomach and intestine of Phyllostomidae: Lonchorhina aurita and Molossidae: Molossus molossus bats were studied immunohistochemically. Three types of immunoreactive (IR) endocrine cells - to serotonin (5-HT), gastrin (GAS) and enteroglucagon (GLUC) - were found in the gastric mucosa and four types of IR cells were identified in the intestinal mucosa. This study showed an interespecfic difference in the regional distribution and relative frequency of endocrine cells in the Chiropteran alimentary tract.

Decrease in intestinal endocrine cells in Balb/c mice with CT-26 carcinoma cells

The density of intestinal endocrine cells, in Balb/c mice with colon 26 (CT-26) carcinoma cells, were examined immunohistochemically at 28 days after implantation. After CT-26 cell administration there was a significant decrease in most of the intestinal endocrine cells (p < 0.01) compared with the control group. The significant quantitative changes in the intestinal endocrine cell density might contribute to the development of the gastrointestinal symptoms commonly encountered in cancer patients.

Chromogranins A and B and secretogranin II: evolutionary and functional aspects

Chromogranins/secretogranins or granins are a class of acidic, secretory proteins that occur in endocrine, neuroendocrine, and neuronal cells. Granins are the precursors of several bioactive peptides and may be involved in secretory granule formation and neurotransmitter/hormone release. Characterization and analysis of chromogranin A (CgA), chromogranin B (CgB), and secretogranin II (SgII) in distant vertebrate species confirmed that CgA and CgB belong to related monophyletic groups, probably evolving from a common ancestral precursor, while SgII sequences constitute a distinct monophyletic group. In particular, selective sequences within these proteins, bounded by potential processing sites, have been remarkably conserved during evolution. Peptides named vasostatin, secretolytin and secretoneurin, which occur in these regions, have been shown to exert various biological activities. These conserved domains may also be involved in the formation of secretory granules in different vertebrates. Other peptides such as catestatin and pancreastatin may have appeared late during evolution. The function of granins as propeptide precursors and granulogenic factors is discussed in the light of recent data obtained in various model species and using knockout mice strains.

Changes of the intestinal endocrine cells in the C57BL/6 mouse after implantation of murine lung carcinoma (3LL): An immunohistochemical quantitative study

AIM: To study the distributions and frequencies of intestinal endocrine cells in the C57BL/6 mouse with immunohistochemical method using seven types of specific antisera against chromogranin A (CGA), serotonin, somatostatin, glucagons, gastrin, cholecystokinin (CCK)-8 and human pancreatic polypeptide (hPP) after abdominal subcutaneous implantation of murine lung carcinoma (3LL).

METHODS: The experimental animals were divided into two groups, one is non-implanted Sham and the other is 3LL-implanted group. Samples were collected from six regions of intestinal tract at 28^th d after implantation of 3LL cells (1×105 cell/mouse).

RESULTS: In this study, five types of immunoreactive (IR) cells were identified except for gastrin and hPP. The regional distributions of the intestinal endocrine cells in the 3LL-implanted group were similar to those of the non-implanted Sham. However, significant decreases of IR cells were detected in 3LL-implanted group compared to those of non-implanted Sham. CGA- and serotonin-IR cells significantly decreased in 3LL-implanted groups compared to that of non-implanted Sham. Somatostatin-IR cells in the jejunum and ileum and CCK-8-IR cells in the jejunum of 3LL-implanted groups significantly decreased compared to that of non-implanted Sham. In addition, glucagon-IR cells were restricted to the ileum and colon of non-implanted Sham.

CONCLUSION: Implantation of tumor cell mass (3LL) induced severe quantifiable changes of intestinal endocrine cell density and the abnormality in density of intestinal endocrine cells may contribute to the development of gastrointestinal symptoms such as anorexia and indigestion, frequently encountered in patients with cancer.

Changes of the gastric endocrine cells in the C57BL/6 mouse after implantation of murine lung carcinoma: An immunohistochemical quantitative study

AIM: The regional distributions and relative frequencies of some gastric endocrine cells of C57BL/6 mice were studied by immunohistochemical method using seven types of specific antisera against chromogranin A (CGA), serotonin, somatostatin, gastrin, cholecystokinin (CCK)-8, glucagon and human pancreatic polypeptide (HPP) after subcutaneous implantation of murine lung carcinoma (3LL) cells.

METHODS: The experimental animals were divided into two groups, one is non-implanted sham and the other is 3LL-implanted group. Samples were collected from the two regions of stomach (fundus and pylorus) at 28 d after implantation of 3LL cells (1×10⁵ cell/mouse).

RESULTS: In this study, all the seven types of immunoreactive (IR) cells were identified except for HPP. Most of these IR cells in the gastric portion were generally spherical or spindle in shape (open-type cell) while cells showing round in shape (closed-type cell) were found occasionally. The regional distributions of gastric endocrine cells in the 3LL-implanted group were similar to those of non-implanted sham. However, significant decreases of some types of IR cells were detected in 3LL-implanted group compared to those of non-implanted sham. In addition, the IR cells showing degranulation were numerously detected in 3LL-implanted group. CGA-, serotonin- and somatostatin-IR cells in the fundus and pylorus regions, and gastrin-IR cells in the pylorus regions of 3LL-implanted groups significantly decreased compared to those of non-implanted sham. However, no changes on frequencies of CCK-8- and glucagon-IR cells were demonstrated between 3LL-implanted and non-implanted groups.

CONCLUSION: Endocrine cells are the anatomical units responsible for the production of gut hormones, and the change in their density would reflect a change in the capacity of producing these hormones. Implantation of tumor cell mass (3LL) induced severe quantitative changes of gastric endocrine cell density, and the abnormality in density of gastric endocrine cells may contribute to the development of gastrointestinal symptoms such as anorexia and indigestion, frequently encountered in patients with cancer.

Tissue Expression and Secretion of Amylin

Amylin and insulin are co-localized within the same secretory granules of pancreatic beta-cells. Acutely, the secreted ratio of amylin:insulin is comparatively invariant, but long-standing hyperglycemia may favor induction of amylin synthesis and secretion over that of insulin. Amylin is also found in much lesser quantities in the gut and other tissues. In humans, both type 1 diabetes mellitus and the later stages of type 2 diabetes mellitus are characterized by deficiency of both insulin and amylin secretion. The severity of amylin deficiency appears to correlate with the severity of insulin deficiency. This concordance of deficiencies in amylin and insulin secretion observed with the progression of diabetes mellitus is consistent with their co-localization in pancreatic beta-cells. Amylin is cleared mainly by proteolytic degradation at the kidney. The terminal t1/2 for rat amylin in rats is approximately 13 min, and that for pramlintide in humans is approximately 20-45 min.

An immunohistochemical study on the neuropeptide-producing endocrine cells in the alimentary tract of wrinkled frog, Rana rugosa (Ranidae)

The regional distribution and relative frequency of neurohormonal peptides-producing endocrine cells were demonstrated in the alimentary tract of wrinkled frog, Rana rugosa, using eight types of specific antisera raised against mammalian regulatory peptides. The alimentary tract of frog was divided into six portions from esophagus to rectum. Most of the cells in the epithelial lining portion, between epithelial cells, were generally spherical or spindle shaped having long cytoplasmic process that was reached to the lumen (open-typed cell) while cells showing round shape (close-typed cell) were also found in the gastric, esophageal or intestinal glands occasionally. All of eight immunoreactive (IR) cells against serotonin, somatostatin, bovine Sp-1/chromogranin (BCG), gastrin, cholecystokinin (CCK)-8, bombesin, glucagon, and human pancreatic polypeptide (HPP) were observed in this study. Serotonin-IR cells were demonstrated throughout whole alimentary tract including esophagus and showed most predominant frequency in antrum. Somatostatin-IR cells were also detected throughout whole alimentary tract including esophagus and showed most predominant in pylorus and antrum. BCG-IR cells were restricted to stomach regions with relatively low frequencies. CCK-8-IR cells were observed from antrum to ileum and showed highest frequency in antrum. Gastrin-IR cells were restricted to antrum with low frequency and bombesin-IR cells were demonstrated from esophagus to antrum with various frequencies. Glucagon-IR cells were located throughout whole alimentary tract except for rectum and showed most predominant frequency at antrum. HPP-IR cells were detected from antrum to ileum with highest frequency in antrum. In conclusion, the regional distribution and relative frequency of these IR cells correspond well to the previous report in anuran species but somewhat peculiar patterns are also detected.

Immunohistochemical localization of amylin in rat brainstem

Immunohistochemical studies were conducted on rat brainstem using a specific polyclonal antiserum against the COOH-terminal (25-37) of human amylin. Amylin-immunoreactive cell bodies were observed in the vestibular, cochlear, trapezoid, and inner cerebellar nuclei and in the mesencephalic nucleus of trigeminal nerve. Positive cell bodies were also found in lateral, gigantocellular and magnocellular reticular nuclei. Numerous amylin-immunoreactive nerve fibers were shown in the trigeminal spinal tract, in the solitary area and in the area postrema. Amylin-immunoreactive cell bodies were often surrounded by a network of tyrosine hydroxylase-immunoreactive nerve fibers. These results provide morphologic evidence that amylin may play a role in some discrete sensory functions.

Chromogranin A-immunoreactive cells in the olfactory system of anuran amphibians

Chromogranin A (CgA) is a member of the granin family of acidic proteins that are present in the secretory granules of many endocrine and neuroendocrine cells. The specific function(s) of these proteins is not known, but they seem to be the precursors of biologically active peptides, and they may act as helper proteins in the sorting and packaging of peptide hormones and neuropeptides. Using indirect immunohistochemistry, we have found CgA immunoreactivity in the primary olfactory epithelia, the vomeronasal epithelia, the olfactory nerves, and the olfactory bulbs of tadpoles of the American toad, Bufo americanus, and the green frog, Rana clamitans. CgA immunoreactivity was present in the early stages of larval development in toads but was not detected in toad tadpoles after the hindlimb buds formed or in toadlets or adults. In green frog tadpoles, CgA-immunoreactive cells were found in pre- and prometamorphic stages but not in late climax. CgA immunoreactivity was also absent in froglets, but it was detected in the vomeronasal epithelium but not the olfactory epithelium of adult green frogs.

Granin proteins (chromogranin A and secretogranin II C23-3 and C26-3) in the endocrine pancreas of amphibians

The occurrence and cellular distribution of chromogranin A (CgA) and of two synthetic secretogranin II (SgII)-fragments (termed C23-3 and C26-3) has been investigated immunohistochemically in the endocrine pancreas of five amphibian species. Immunoreactivity for CgA was detected only in specimens of the genus Rana, whereas for SgII it was found in all the urodeles and anurans studied. Either CgA or the SgII-fragment displayed its own cellular distribution patterns in the endocrine pancreas of a given species. Moreover, immunoreactivity for both regions (C23-3 and C26-3) of the SgII-molecule exhibited by the same endocrine cell population have been encountered in newt and frog organs. Besides the interspecific heterogeneous distribution of CgA and of the two SgII-fragments in relation to the insular cell types, a striking heterogeneity of their immunostaining density among the endocrine cells of the same type was also revealed. The above findings entirely support the concept of a good conservation of granins during phylogeny; they do not support, however, the previously ascribed usefulness of these anionic glycoproteins as markers for all neuro-endocrine cells.

Histology and lectin-binding patterns in the digestive tract of the carnivorous larvae of the anuran, Ceratophrys ornata

Larvae of Ceratophrys ornata are carnivorous, have relatively short digestive tracts and continue to feed during metamorphic climax, in contrast to those of more typical herbivorous anuran larvae. The present study describes both histological and histochemical changes in the stomach, small intestine, and large intestine of C. ornata prior to and during metamorphic climax. Modifications in these organs were found to be similar to but less dramatic than those in herbivorous larvae. Luminal epithelial cells in the three regions develop vacuoles, suggesting degeneration, but sloughing of this epithelium, as occurs in herbivorous larvae, was not observed in C. ornata. Multicellular tubular glands develop gradually in the gastric area during the larval stages, gastric pits appear during metamorphic climax, and mucous neck cells are first visible in the juvenile. Goblet cells in the small and large intestine increase in number during larval life, as do the number of folds in the intestinal wall. Increase in diameter and thickness of the wall occurs in the stomach as well as in the small and large intestine. Such changes result in an adult-type digestive tract characteristic of frogs in general. Staining with two horseradish peroxidase conjugated lectins, soybean agglutinin (SBA) and Ulex europaeus agglutinin I (UEA I), demonstrated specific sites along the digestive tract of glycoconjugates with terminal sugars N-acetylgalactosamine and alpha-fucose, respectively. As metamorphic climax approaches, staining intensities decrease--thus providing evidence for metamorphic changes in the sugar moieties of glycoconjugates present in the digestive tract of carnivorous larvae.

Granin proteins (chromogranin A and secretogranin II C23-3 and C26-3) in the intestine of reptiles

The occurrence, distribution and the possible cellular co-localizations of chromogranin A (CgA) and of two synthetic secretogranin II-peptides (SgIIC23-3 and SgIIC26-3) with several enteric neuropeptides and serotonin have been investigated immunohistochemically in turtles, lizards and snakes. The distribution of CgA-immunoreactivity was restricted only to the enteroendocrine cells in all the reptiles studied. SgII-immunoreactivity--absent in turtle--revealed nerve cells and fibers, besides enteroendocrine cells in lizard and snake guts. Moreover, the two antisera (C23-3 and C26-3) raised against the different regions of the SgII-molecule yielded distinct distribution patterns of immunoreactivity both in the lizard and snake organs. Small amounts of enteric serotonin cells co-stored CgA or SgIIC23-3 in lizards and snakes and only SgIIC26-3-peptide in snakes. CgA was found co-stored with somatostatin in a few enterocytes of the turtle duodenum. In the same gut segment of lizards and throughout the snake organ, neurotensin and the SgIIC23-3-peptide co-existed in a small number of endocrine cells. The pancreatic polypeptide-containing cells were devoid of immunoreactivity both for CgA and SgII. Bombesin immunopositive cells were absent throughout the intestines of the reptiles investigated. The above findings entirely support the heterogenous distribution of granins in neuroendocrine organs and tissues and also within the same neuroendocrine cell population. They further support the concept of a good conservation of granins during phylogeny.

Phosphorylation and O-glycosylation sites of human chromogranin A (CGA79-439) from urine of patients with carcinoid tumors

Because of their water-soluble properties, chromogranins (CGs) and chromogranin-derived fragments are released together with catecholamines from adrenal chromaffin cells during stress situations and can be detected in the blood by radiochemical and enzyme assays. It is well known that chromogranins can serve as immunocytochemical markers for neuroendocrine tissues and as a diagnostic tool for neuroendocrine tumors. In 1993, large CGA-derived fragments have been shown to be excreted into the urine in patients with carcinoid tumors and the present study deals with the characterization of the post-translational modifications (phosphorylation and O-glycosylation) located along the largest natural CGA-derived fragment CGA79-439. Using mild proteolysis of peptidic material, high performance liquid chromatography, sequencing, and mass spectrometry analysis, six post-translational modifications were detected along the C-terminal CGA-derived fragment CGA79-439. Three O-linked glycosylation sites were located in the core of the protein on Thr163, Thr165, and Thr233, consisting in di-, tri-, and tetrasaccharides. Three phosphorylation sites were located in the middle and C-terminal domain, on serine residues Ser200, Ser252, and Ser315. These modified sites were compared with sequences of others species and discussed in relation with the post-translational modifications that we have reported previously for bovine CGA.

Granin proteins (chromogranin A and secretogranin II C23-3 and C26-3) in the intestine of amphibians

The occurrence, distribution and possible cellular colocalizations of chromogranin A (CgA) and of two synthetic secretogranin II peptides (SgIIC23-3 and SgIIC26-3) with serotonin, somatostatin, neurotensin, pancreatic polypeptide and bombesin have been investigated immunohistochemically in the amphibian gut. CgA or SgIIC26-3-immunostained enterocytes were found throughout along the frog intestine, while no immunoreaction for any of the tested antisera against granins was seen in the same organ of newts. Variable amounts of serotonin-immunoreactive cells co-storing CgA or SgIIC26-3, but never both granins, were encountered in all intestinal segments of the frogs investigated. In addition, CgA was co-localized with somatostatin in a few endocrine cells of the frog (genus Rana) duodenum and small intestine. In the duodenum of another frog (genus Xenopus) several enterocytes co-stored SgIIC26-3 and neurotensin. Pancreatic polypeptide- and bombesin-immunoreactive cells, the latter detected only in the duodenum of Xenopus, did not contain and granin. The results suggest that, in spite of their relatively restricted occurrence in the intestine of frogs and even of their absence in that of newts, the granins are well conserved during phylogeny. On the other hand, the heterogeneous distributions of these anionic glycoproteins, related to the entero-endocrine cell types, make their previously assigned usefulness as markers of all neuro-endocrine cells unlikely.

Phosphorylation and O-glycosylation sites of bovine chromogranin A from adrenal medullary chromaffin granules and their relationship with biological activities

Bovine adrenal medullary chromogranin A, the major soluble component of chromaffin granules, is a phosphorylated glycoprotein. In the present work, phosphorylation and glycosylation sites were determined using mild proteolysis, peptide separation, microsequencing, and mass analysis by electrospray and matrix-assisted laser desorption ionization time-of-flight techniques. Seven post-translational modification sites were detected. Two O-linked glycosylation sites, each consisting of the trisaccharide NeuAcalpha2-3Galbeta1-3GalNAcalpha1, were located in the middle part of the protein, on Ser186 and on Thr231. The former residue is present in the antibacterial peptide named chromacin. Four phosphorylation sites were located on serine residues at positions Ser81 in the N-terminal region of the protein and Ser307, Ser372, and Ser376 in the C-terminal end. One additional phosphorylation site was found on the tyrosine residue at position Tyr173, the N-terminal amino acid of chromacin. With the exception of the phosphorylation on Tyr173, all of the other post-translational modifications are located on highly conserved chromogranin A regions, implying some biological importance.

Somatostatin-immunoreactive cell in the gastrointestinal tract of the frog Rana esculenta

The morphology and topographic distribution of somatostatin-immunoreactive cells in the stomach and small intestine of the frog Rana esculenta were studied at the light-microscopic level by the use of the peroxidase-antiperoxidase method. Scattered immunostained cells occurred in all regions of the gastrointestinal tract investigated. In the small intestine, the number of these cells decreased gradually in the oral to anal direction, i.e. from the pyloric (antral) stomach to the entrance into the colon. Most of the immunostained cells possessed thick, short cytoplasmic processes, which did not display a preferential spatial orientation. Other somatostatin-immunoreactive cells, which were exclusively located in the small intestine, gave rise to a single long extension oriented toward the lumen. In both stomach and small intestine, a complete penetration of the epithelial surface by these processes of somatostatin-immunoreactive cells was observed only occasionally. The morphological features of the somatostatin-immunostained cells speak in favor of endocrine, paracrine, and possibly also intraluminal secretory functions of the enteroendocrine somatostatin system in frogs.