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216 records · Page 12Linked to original sources
PubMed1984

Immunocytochemical study of gastro-entero-pancreatic (GEP) endocrine cells in the vampire bat (Desmodos rotundus).

The distribution and frequency of gastro-entero-pancreatic (GEP) endocrine cells were studied in vampire bats by immunocytochemistry. Moderate numbers of somatostatin- and a few 5-hydroxytryptamine (5-HT)- and glucagon-immunoreactive cells were seen in the fundic cecum of the stomach. Numerous gastrin- and moderate numbers of somatostatin- and 5-HT-immunoreactive cells were found in the pyloric region. Moderate numbers of 5-HT-, somatostatin-, and gastrin-immunoreactive cells also were found in BRUNNER's glands. In addition to the above-mentioned 4 immunoreactive cell types, cells immunoreactive for glicentin, secretin, cholecystokinin (CCK), gastric inhibitory peptide (GIP), and neurotensin were found in the intestine. Numerous insulin-, moderate numbers of somatostatin- and glucagon-, and a few 5-HT-immunoreactive cells were detected in the pancreatic islets with lesser numbers scattered within the exocrine pancreas. Motilin- and pancreatic polypeptide-immunoreactive cells were not observed in this study.

Animals↗
PubMed1982

[Glucagonoma with diabetic ketoacidosis; case report].

Diabetic ketoacidosis is an extremely rare manifestation of glucagonoma. We report such a case in a 72-year-old woman known to be diabetic for seven years. The patient was admitted with diabetic ketoacidosis and associated necrolytic migratory erythrema which suggested the diagnosis of glucagonoma. Plasma glucagon levels were increased (569 to 2298 pg/ml). A vascular tumor of the head of the pancreas without obvious hepatic metastases was visualised by angiography. Duodeno-pancreatectomy including the head of the pancreas led to complete recovery of the mucocutaneous lesions and the plasma glucagon level fell (229 pg/ml). The tumor had several histological characteristics suggesting malignancy and a high glucagon content on extraction. Electron microscopy showed multiple A cells and a few isolated B cells. Most of the cells showed immunoreactivity with anti-glucagon and anti-glicentine antibodies. Three months after surgery, the diabetes was again required treatment with insulin. Plasma glucagon level was again increased and chemotherapy with dimethyltriazenimidazolecarboxamide was undertaken.

Adenoma, Islet Cell↗
PubMed1983

Gastro-entero-pancreatic (GEP) endocrine system of the flatfish, Paralichtys olivaceus: an immunocytochemical study.

The localization of the gastro-entero-pancreatic (GEP) endocrine cells in the flatfish, Paralichtys olivaceus was examined using immunocytochemical methods. The Brockmann body of the flatfish included a large principal islet and a smaller islet. Three types of endocrine cells, i.e., insulin-, glucagon- and somatostatin-immunoreactive cells were found in both islets. Pancreatic polypeptide (PP)-immunoreactive cells were restricted to the periphery of the smaller islet. In the digestive tract, somatostatin cells occurred only in the stomach. The pyloric appendages contained cells reactive simultaneously to cholecystokinin (CCK) antiserum and to gastrin antiserum, whereas the middle portion of the intestine contained cells reactive only to the CCK antiserum. The intestinal endocrine cells showing N-terminal glucagon-immunoreactivity were also reactive to a glicentin antiserum.

Animals↗
PubMed1993

Endocrine cells in colorectal adenocarcinomas: incidence, hormone profile and prognostic relevance.

The occurrence of endocrine cells in 350 cases of colorectal adenocarcinoma was studied by immunohistochemistry for chromogranin A (CGA). The hormone profile of endocrine tumor cells, the correlation between endocrine differentiation and presence of other colorectal epithelial-cell lineages and the prognostic relevance of endocrine differentiation in colorectal cancer were investigated. CGA-positive tumor cells were found in 30% of cases, 21% showing moderate positivity and 9.0% extensive positivity. Of CGA-positive tumors, 70% additionally produced neurohormones, mainly indigenous to normal colorectal epithelium: 55% showed immunoreactivity for glucagon-like substances, 20% for serotonin and 10% for somatostatin, PYY and HCG. No immunoreactivity was found for various neurohormones not normally produced by colorectal endocrine cells. CGA-positive tumors tended to be more aggressive than CGA-negative tumors. Especially, tumors with extensive CGA positivity showed shorter survival, which was most apparent within Dukes' stage C. In multivariate analysis, extensive CGA positivity was an independent indicator of poor prognosis. CGA immunoreactivity significantly correlated with mucin production, but not with expression of secretory component (SC), a columnar-cell marker. Mucin production significantly correlated with SC expression. Tumors positive for CGA but not for mucin and/or SC showed the worst prognosis. SC expression was a relatively favorable feature, and mucin-producing tumors showed intermediate behavior.

Adenocarcinoma↗
PubMed1994

Immunological detection of prohormone convertases in two different proglucagon processing cell lines.

The distribution of the prohormone convertases, PC1/3, PC2 and PC5/6, was determined by immunoblotting in two cell lines. In alpha TC1-6 cells, the proglucagon processing occurred according to the pancreatic A-cell type. In STC-1 cells, proglucagon was processed in a manner reminiscent of the intestinal L-cell type. PC1/3 was undetectable in both proglucagon processing cell lines whereas PC2 displayed a strong immunostaining in the alpha TC1-6 cells and was barely detectable in the STC-1 cells. PC5/6 was detected as a 70 kDa protein in both cell lines. These results suggest a possible role of PC2 in the processing of proglucagon into glucagon in the A-cells, whereas in L-cells it would require still undetermined endoproteases.

Animals↗
PubMed1995

Simulating the folding of small proteins by use of the local minimum energy and the free solvation energy yields native-like structures.

Assuming that the protein primary sequence contains all information required to fold a protein into its native tertiary structure, we propose a new computational approach to protein folding by distributing the total energy of the macromolecular system along the torsional axes. We further derive a new semiempirical equation to calculate the total energy of a macromolecular system including its free energy of solvation. The energy of solvation makes an important contribution to the stability of biological structures. The segregation of hydrophilic and hydrophobic domains is essential for the formation of micelles, lipid bilayers, and biological membranes, and it is also important for protein folding. The free energy of solvation consists of two components: one derived from interactions between the atoms of the protein, and the second resulting from interactions between the protein and the solvent. The latter component is expressed as a function of the fractional area of protein atoms accessible to the solvent. The protein-folding procedure described in this article consists of two successive steps: a theoretical transition from an ideal alpha helix to an ideal beta sheet is first imposed on the protein conformation, in order to calculate an initial secondary structure. The most stable secondary structure is built from a combination of the lowest energy structures calculated for each amino acid during this transition. An angular molecular dynamics step is then applied to this secondary structure. In this computational step, the total energy of the system consisting of the sum of the torsional energy, the van der Waals energy, the electrostatic energy, and the solvation energy is minimized. This process yields 3-D structures of minimal total energy that are considered to be the most probable native-like structures for the protein. This method therefore requires no prior hypothesis about either the secondary or the tertiary structure of the protein and restricts the input of data to its sequence. The validity of the results is tested by comparing the crystalline and computed structures of four proteins, i.e., the avian and bovine pancreatic polypeptide (36 residues each), uteroglobin (70 residues), and the calcium-binding protein (75 residues); the C alpha-C alpha maps show significant homologies and the position of secondary structure domains; that of the alpha helices is particularly close.

Animals↗
PubMed2001

Immunocytochemical and ultrastructural characterization of endocrine cells in the larval stomach of the frog Rana temporaria tadpoles: a comparison with adult specimens.

According to immunostaining and ultrastructural patterns, Rana temporaria tadpole stomach displays a well-differentiated endocrine population comprising, at least, six cellular types: ECL, EC [serotonin], D [somatostatin] - all three of them abundant -, P [bombesin] - less numerous -, CCK-8 [cholecystokinin/gastrin] and A [glucagon/glicentin] - both very scarce. Larval endocrine cells are mainly located in the surface epithelium and show open or closed morphologies. Cellular diversity is similar in tadpoles and frogs, with the exception of immunoreactivity for gastrin-17, found in adults in numerous cells. Larval cells display mature ultrastructural traits, although with smaller secretory granules. The different distribution of endocrine cells, which in adults are preferentially located in the glands, probably refers to different functional requirements. However, the rich vascular plexus present in larval mucosa may be an efficient transport medium of surface hormones to-gastric targets. The enhancement in adults of endocrine population and correlative increase in hormonal secretion indicates a more active functional role, probably related to the shift from herbivorous to carnivorous habits. In summary, the tadpole gastric endocrine population, although not as numerous as that of adult frogs, displays histological traits that indicate a relevant (immunoreactive and ultrastructural properties, cellular diversity) and specific (surface location, relative abundance of open-type cells) role of local regulatory factors in amphibian larval gastric function.

Animals↗
PubMed1994

Proglucagon is processed to glucagon by prohormone convertase PC2 in alpha TC1-6 cells.

Proglucagon is processed differentially in the pancreatic alpha cells and the intestinal L cells to yield either glucagon or glucagon-like peptide 1, respectively, structurally related hormones with opposing metabolic actions. Here, we have studied the processing of proglucagon in alpha TC1-6 cells, an islet-cell line transformed by simian virus 40 large tumor (T) antigen, a model of the pancreatic alpha cell. We found that these cells process proglucagon at certain dibasic cleavage sites to release glucagon and only small amounts of glucagon-like peptide 1, as demonstrated by both continuous and pulse-chase labeling experiments. Both normal islet alpha cells and alpha TC1-6 cells were shown to express the prohormone convertase PC2 at high levels, but not the related protease PC3. Expression of PC2 antisense RNA in alpha TC1-6 cells inhibited both PC2 production and proglucagon processing concomitantly. We conclude that PC2 is the key endoprotease responsible for proglucagon processing in cells with the alpha-cell phenotype.

Animals↗
PubMed1996

Induction of intestinal epithelial proliferation by glucagon-like peptide 2.

Injury, inflammation, or resection of the small intestine results in severe compromise of intestinal function. Nevertheless, therapeutic strategies for enhancing growth and repair of the intestinal mucosal epithelium are currently not available. We demonstrate that nude mice bearing subcutaneous proglucagon-producing tumors exhibit marked proliferation of the small intestinal epithelium. The factor responsible for inducing intestinal proliferation was identified as glucagon-like peptide 2 (GLP-2), a 33-aa peptide with no previously ascribed biological function. GLP-2 stimulated crypt cell proliferation and consistently induced a marked increase in bowel weight and villus growth of the jejunum and ileum that was evident within 4 days after initiation of GLP-2 administration. These observations define a novel biological role for GLP-2 as an intestinal-derived peptide stimulator of small bowel epithelial proliferation.

Animals↗
PubMed1990

Depressed tubular adenoma of the stomach: pathological and immunohistochemical features.

We examined 12 depressed tubular adenomas of the stomach pathologically and immunohistochemically in order to clarify the difference between the depressed type and the elevated type. Depressed tubular adenomas showed shallow mucosal depression and, of the 12, nine were endoscopically diagnosed as early gastric cancer. Histologically, the adenoma cells showed dysplasia in varying degree and focal adenocarcinoma occurred in two adenomas measuring over 2 cm. The mean height of the adenoma glands was 0.63 +/- 0.31 mm in the 12 depressed adenomas and 1.32 +/- 0.43 mm in 44 elevated adenomas, while the mean heights of the subjacent mucosa were 0.18 +/- 0.19 mm and 1.07 +/- 0.71 mm, respectively. Thus, depressed adenomas resulted from paucity of the mucosa subjacent to the adenoma glands and the height of the adenomatous glands was half that found in the elevated type. Goblet cells, a variety of endocrine cells and lysozyme-containing cells were found in nine, nine and eight depressed adenomas, respectively, in variable numbers. Hyperplasia of these cells was also detected in depressed adenomas showing mild or moderate dysplasia. Immunohistochemical examination revealed no difference in the phenotypic expression of adenoma cells as between the depressed and the elevated type.

Adenoma↗
PubMed1988

The gastric acid secretagogue gastrin-releasing peptide and the inhibitor oxyntomodulin do not exert their effect directly on the parietal cell in the rat.

Previous studies suggested that gastrin-releasing peptide (a neuropeptide found in rat oxyntic mucosa) and oxyntomodulin (a glucagon-containing peptide of mammalian gut) could directly affect the acid secretion of the parietal cells. We therefore studied their effect on gastric acid production in vitro by measuring [14C]-aminopyrine accumulation, a reliable index of H+ generation, in isolated rat parietal cells. However, neither gastrin-releasing peptide nor oxyntomodulin influenced basal acid secretion or histamine-stimulated gastric acid secretion. Electron-microscopic studies of unstimulated and histamine-stimulated parietal cells confirmed that the cells retained the normal morphology of intracellular organelles and that the cells responded to physiological stimulation by marked expansion of the intracellular canaliculi.

Aminopyrine↗
PubMed2004

Glucagon-like peptide 2 (GLP-2), an intestinotrophic mediator.

Glucagon-like peptide 2 (GLP-2) is a newly discovered gastrointestinal peptide with 33% sequence homology to glucagon. GLP-2 has attracted interest because of its potent intestinotrophic endocrine/paracrine actions. The peptide, consisting of 33-amino-acid, results from expression of the glucagon gene in the enteroendocrine L-cells of the intestinal mucosa, from where it is released mainly in response to luminal contact with unabsorbed nutrients. In addition to mucosal growth, GLP-2 enhances activities of several intestinal brush-border enzymes, and it delays gastric transit, thereby increasing the intestinal capacity for nutrient absorption. Thus, it appears that GLP-2 serves to ensure an optimal intestinal capacity. The physiological responses following exogenous administration of GLP-2 have been intensely investigated, and these appear to be rather specific for the gut, which is concordant with the localization of the GLP-2 receptor. In addition, treatment with GLP-2 in experimental animal models of several enteropathies indicates that GLP-2 ameliorates most of the observed intestinal abnormalities in these conditions. Following secretion to the blood stream, the intact peptide is degraded rather rapidly by an aminopeptidase. To circumvent the rapid and widespread metabolization of intact GLP-2, degradation-resistant synthetic GLP-2 analogues have been developed together with other approaches, such as inhibition of the GLP-2 degrading enzyme. This is of particular interest with respect to developing GLP-2 into a useful therapeutic agent in conditions with compromised intestinal function, since the first clinical trial has already indicated the potential of GLP-2 treatment in patients with short bowel syndrome.

Amino Acid Sequence↗
PubMed1990

Biological and clinicopathological significance of endocrine differentiation of gastric adenocarcinoma evaluated by double immunohistochemical labeling for chromogranin A and bromodeoxyuridine.

To elucidate the biological and clinicopathological significance of endocrine differentiation in gastric adenocarcinoma, an immunohistochemical study was made of 127 cases with ascertained five-year survivals, and of 45 recent cases of bromodeoxyuridine (BrdU) labeling. Endocrine differentiated cancer cells were demonstrated in 37 out of the 127 cases (29.1%) evaluated by chromogranin A (CGA) immunoreactivity, and all CGA-positive tumors were classified as advanced gastric cancer. Analysis of retrospective five-year survival rates revealed the adenocarcinomas with endocrine differentiation to have had significantly longer survival times than those without endocrine immunoreactivity in stage II, but not in stages III or IV. Double immunolabeling for CGA and BrdU in the other 45 adenocarcinoma cases showed only a single CGA-positive cancer cell with BrdU incorporation among a total of 454 CGA-positive cells examined. There was no significant difference between the labeling indices of the general cancer population and the cancer cells adjacent to CGA-positive cells. In conclusion, endocrine differentiation of gastric cancer is not uncommon, particularly in advancing cancer, and it would be a useful marker for a better prognosis in stage II. Probably, endocrine differentiated cancer cells are almost dormant with virtually no DNA synthesizing activity, and their paracrine effect is most unlikely to work in vivo.

Adenocarcinoma↗
PubMed1994

Proglucagon processing in porcine and human pancreas.

In the pancreas proglucagon (PG), a peptide precursor of 160 amino acids is cleaved to produce glucagon and a 30-amino acid N-terminal flanking peptide, but the fate of the C-terminal flanking peptide (99 amino acids) is incompletely known. We subjected acid ethanol extracts of human and porcine pancreases to gel filtration and analyzed the fractions with specific radioimmunoassays for the following regions of proglucagon: PG 62-69, PG 72-81, PG 78-87, PG 98-107 amide, PG 126-134, and PG 149-158. Based on these assays and successive purifications by high performance liquid chromatography we isolated and purified to homogeneity three porcine peptides which were subjected to mass spectrometry and sequencing. One peptide was PG 64-69. The second was PG 72-108, as determined by mass spectrometry, N-terminal amino acid sequencing, and specific radioimmunoassays. The third had a molecular size of approximately 10,000, an N-terminal sequence corresponding to PG 72-81, and a C-terminal sequence terminating at PG 158 (specific radioimmunoassay). A similar peptide with an identical N-terminal sequence, a C-terminal sequence corresponding to PG 146-158, and a molecular mass of 9969 (theoretical mass for human PG 72-158 = 9971) was isolated from human pancreas together with small amounts of a peptide corresponding to PG 72-107 amide. Thus, the pancreatic processing of the C-terminal flanking peptide in proglucagon includes the formation of equimolar (to glucagon) amounts of PG 64-69 and PG 72-158 (major proglucagon fragment) and smaller amounts of N-terminally extended glucagon-like peptide-1 (GLP-1) (PG 72-108 in pigs and PG 72-107 amide in humans).

Amino Acid Sequence↗