Papers by Guida Portela-gomes
Scandinavian journal of gastroenterology. Supplement
The presence of serotonin, substance P and enteroglucagon was investigated in 8 argentaffin and a... more The presence of serotonin, substance P and enteroglucagon was investigated in 8 argentaffin and argyrophil midgut carcinoid tumours. All tumours were argentaffin and displayed formalin-induced fluorescence indicating a content of serotonin. In addition, all 8 tumours showed substance P immunoreactivity and 7 of them enteroglucagon immunoreactivity. The results indicate that the midgut carcinoid tumours are as a rule multihormonal.
Acta pathologica, microbiologica, et immunologica Scandinavica. Section A, Pathology, 1982
Parathyroid glands from inbred rats were transplanted to rats of the same strain. The transplanta... more Parathyroid glands from inbred rats were transplanted to rats of the same strain. The transplantation resulted in hyperparathyroidism and persistent hypercalcaemia. These hypercalcaemic animals were compared with the hypocalcaemic donors and with untreated controls. No significant differences in serum gastrin values were found between the different groups. In all three groups, one series of animals was killed 6 weeks after the transplantation (6w series) and another after 14 weeks (14w series). Quantitative studies of the antral gastrin cells showed an increase in the number of these cells per unit volume in the 6w series in the hyperparathyroid recipient animals. The number of gastrin cells per unit segment was also higher in the recipient animals than in the parathyroidectomized and untreated groups in both the 6w and 14w series. The amount of gastrin extracted from antral mucosa did not differ between the different groups. The findings show that an experimentally induced hyperpar...
Current Medicinal Chemistry-Immunology, Endocrine & Metabolic Agents, 2004
ABSTRACT Chromogranin A (CgA) and chromogranin B (CgB) are proteins present in secretory granules... more ABSTRACT Chromogranin A (CgA) and chromogranin B (CgB) are proteins present in secretory granules of the diffuse neuroendocrine system, with multiple pairs of basic amino acids, which are potential cleavage sites for production of biologically active peptides. We have developed antibodies against 12 defined epitopes of the CgA and 16 defined epitopes of CgB. With these, we have shown that the pancreatic neuroendocrine cells express different epitopes of the CgA and the CgB molecules. The insulin and glucagon producing cells express almost all examined epitopes of CgA and CgB, while the pancreatic polypeptide cells express some defined parts of the chromogranins and the somatostatin cells express only one CgA epitope and two CgB epitopes. Malignant endocrine pancreatic tumours show varied expression of chromogranin epitopes. The normal and neoplastic neuroendocrine cells of the gastrointestinal tract show various expressions of CgA epitopes. Thus, gastrin cells show a different expression of CgA epitopes than the enterochromaffin cells. One of the antibodies, CgA176-195, immunostained a larger cytoplasmic area than the other CgA antibodies, including the commercially available monoclonal antibody (LK2H10). In the adrenal glands, all chromaffin cells showed immunoreactivity to all region-specific chromogranin antibodies tested. By radioimmunoassay measurements we have shown that circulating plasma concentrations of different chromogranin epitopes differ between various types of tumours, indicating specific processing. We have also shown that the region-specific antibodies can be used to study biological processes. We conclude that the region-specific antibodies presented in this review are important tools to further study the biological role of chromogranins.
Applied Immunohistochemistry & Molecular Morphology, 2000
Knowledge concerning tissue-specific expression of the five somatostatin receptor subtypes is of ... more Knowledge concerning tissue-specific expression of the five somatostatin receptor subtypes is of great importance in understanding their physiological function. We developed rabbit polyclonal antibodies specific for each human somatostatin receptor subtype and report our results concerning the expression in normal endocrine pancreatic cells. The antibodies were produced by immunizing rabbits with fragments specific for the five cloned somatostatin receptor subtypes. Colocalization of these somatostatin receptors with the four major islet hormones--insulin, glucagon, somatostatin, and pancreatic polypeptide--was studied in normal human endocrine pancreatic cells, using double-immunofluorescence staining. High expression of somatostatin receptor subtypes 1, 3, and 4 was found in all endocrine pancreatic cells. Somatostatin receptor subtype 2 was frequently expressed in alpha and beta cells, whereas expression was low in pancreatic polypeptide cells and intermediate in delta cells. Somatostatin receptor subtype 5 was expressed in most beta and delta cells but almost absent in alpha and pancreatic polypeptide cells. There is a variability in the normal expression of somatostatin receptor subtypes among the different human endocrine pancreatic cells. Knowledge of this expression and the physiological function mediated by these receptors will be valuable in the future when considering treatment of endocrine disorders.
Advances in Experimental Medicine and Biology, 2002
Virchows Archiv, 2005
Chromogranin A (CgA) and its valuable complement synaptic vesicle protein 2 (SV2) are neuroendocr... more Chromogranin A (CgA) and its valuable complement synaptic vesicle protein 2 (SV2) are neuroendocrine (NE) markers. Post-translational processing of CgA has been reported to vary in different NE cell types and tumors, but little is known regarding the expression of various CgA epitopes and SV2 in NE pulmonary tumors. We studied the immunoreactivity to six CgA epitopes and SV2 in ten typical (TC) and ten atypical (ACT) carcinoids, five large-cell NE carcinomas (LCNEC) and five small-cell carcinomas (SCLC), also comparing the results with clinicopathological characteristics of tumors. The sequences CgA 17--38 (vasostatin), 176--195 (chromacin), 375--384 (parastatin) and 411--424 (C-terminal parastatin) and SV2 were relevant markers for the CT/ATC group, whereas the antibody to CgA 176--195 was a better marker for the LCNEC/SCLC group. An inverse correlation was found between proliferative activity and granule-related markers in the CT/ACT group, and a direct correlation in poorly differentiated tumors. The expression of granule-related markers did not correlate with hormone content or clinical characteristics of NE tumors. The expression of CgA epitopes and SV2 occurs in all NE tumors, differing between better differentiated and poorly differentiated tumors but not within the respective groups.
Regulatory Peptides, 2009
Regulatory Peptides, 2003
Pituitary adenylate cyclase-activating polypeptide (PACAP) is an islet neuropeptide with potent i... more Pituitary adenylate cyclase-activating polypeptide (PACAP) is an islet neuropeptide with potent insulinotropic action. The current study investigates PACAP expression in normal human and rat pancreatic islets, and whether it is altered in diabetic state. To that end, PACAP immunoreactivity was studied by immunofluorescence methods enhanced by the catalyzed reporter deposition (CARD) technique. Insulin and cyclic adenosine monophosphate (cAMP) generation induced by PACAP were investigated in islets isolated from the spontaneously diabetic Goto -Kakizaki (GK) rat. PACAP immunoreactivity was observed in virtually all insulin and glucagon cells in both species, but not in somatostatin or pancreatic polypeptide (PP) cells; this co-localization pattern was unaltered in diabetic pancreata. In normal human pancreas, PACAP was further localized ultrastructurally to the secretory granules of insulin and glucagon cells. PACAP significantly potentiated glucose-stimulated insulin release in isolated islets of normal but not of GK rats. PACAP failed to enhance cAMP generation in normal islets, but induced f 5-folds exaggeration in the diabetic islets. In conclusion, using improved immunocytochemistry techniques and electron microscopy (EM), PACAP was shown to be expressed both in normal and diabetic islet cells and localized to secretory granules of insulin and glucagon cells. Furthermore, the insulinotropic action of PACAP was markedly impaired in diabetic islets in spite of exaggerated cAMP response. D
Regulatory Peptides, 2000
Synaptic vesicle protein 2 (SV2), previously reported in the nervous system, is here demonstrated... more Synaptic vesicle protein 2 (SV2), previously reported in the nervous system, is here demonstrated in human neuroendocrine (NE) cells in different endocrine organs -gastrointestinal tract and pancreas, anterior pituitary gland, thyroid C cells, parathyroid chief cells and adrenal medulla. Ultrastructural studies showed SV2 labelling in secretory granules. Comparison of SV2 with the NE cell markers chromogranin A (CgA) and synaptophysin (Sy), showed more SV2 and Sy than CgA-immunoreactive cells in the antrum and pancreas, whereas the converse was found in the intestinal tract. In the intestinal tract more SV2 than Sy-immunoreactive cells were observed. SV2 immunoreactivity occurred in all NE tumours examined -foregut carcinoids (stomach and bronchial carcinoids, islet cell tumours), midgut carcinoids, hindgut carcinoids, medullary thyroid carcinoma, anterior pituitary tumours and pheochromcytomas.
Regulatory Peptides, 2010
This review focus on neuroendocrine tumours (NETs), with special reference to the immunohistochem... more This review focus on neuroendocrine tumours (NETs), with special reference to the immunohistochemical analysis of granins and granin-related peptides and their usefulness in identifying and characterizing the great diversity of NET types. Granins, their derived peptides, and complex protein-processing enzyme systems that cleave granins and prohormones, have to some extent cell-specific expression patterns in normal and neoplastic NE cells. The marker most commonly used in routine histopathology to differentiate between non-NETs and NETs is chromogranin (Cg) A, to some extent CgB. Other members of the granin family may also be of diagnostic value by identifying special NET types, e.g. secretogranin (Sg) VI was only found in pancreatic NETs and phaeochromocytomas. SgIII has recently arisen as an important NET marker; it was strongly expressed in NETs, with some exceptionsphaeochromocytomas expressed few cells and parathyroid adenomas none. Some expression patterns of granin-related peptides seem valuable in differentiating between some benign and malignant NETs, some may also provide prognostic information, among which: well-differentiated NET types expressed more CgA epitopes than the poorly differentiated ones, except insulinomas, where the opposite was noted; medullary thyroid carcinomas containing few cells immunoreactive to a CgB antibody were related to a bad prognosis; C-terminal secretoneurin visualized a cell type related to malignancy in phaeochromocytomas. Further research will probably establish new staining patterns with marker functions for granins in NETs which may be of histopathological diagnostic value.
Regulatory Peptides, 2010
Regulatory Peptides, 2010
Different epitopes of the granin family of proteins, chromogranin (Cg) A, CgB and secretogranin (... more Different epitopes of the granin family of proteins, chromogranin (Cg) A, CgB and secretogranin (Sg) II, have been demonstrated in normal human pancreas, gastrointestinal tract, adrenal medulla and in several neuroendocrine tumours (NETs). SgIII has been recently reported in endocrine pancreas. The aim of the present study was to examine the expression of SgIII in different NETs and compare it with the expression of CgA, CgB and SgII epitopes. Tissue specimens from 47 NETs were analyzed. Antibodies to CgA 250-284, CgB 244-255, SgII 172-186 (C-terminal secretoneurin) and SgIII 348-361 were used for immunostaining. SgIII was expressed in 41 of 47 NETs. The expression of SgIII agreed well with that of CgA, CgB and SgII, with exceptions of phaeochromocytomas, where more CgB and SgII immunoreactive cells were observed and parathyroid adenomas, which were only stained by CgA. In rectal NETs more cells expressed SgIII than CgA. This is the first report on SgIII expression in various NETs. A majority of tumours studied displayed SgIII immunostaining, which indicates a functional relationship with the other granins.
Regulatory Peptides, 2008
Background: Chromogranin (Cg) A is expressed in neuroendocrine and neuronal tissues. It is involv... more Background: Chromogranin (Cg) A is expressed in neuroendocrine and neuronal tissues. It is involved in the generation of secretory granules and is cleaved to form biologically active peptides. Targeted ablation of the Chga gene resulted in increased plasma catecholamines, high blood pressure, and decreased size and number of adrenal medullary chromaffin granules. The aim of this study was to determine whether Chga null mice display changes in the morphology and function of the endocrine pancreas. Materials and methods: Sections of pancreata from Chga−/−, Chga+/− and Chga+/+ mice, were immunostained with antibodies against synaptophysin, CgA, CgB, secretogranin II and the four major pancreatic islet hormones. Plasma was analysed for glucose, insulin, glucagon, somatostatin and pancreatic polypeptide (PP). Results: CgA epitopes were undetectable in the islets of Chga−/− animals. CgB and secretogranin II epitopes were expressed in the islets of all animal groups albeit with decreased expression in Chga−/− islets. The islet number and size were decreased in the Chga−/− animals compared with Chga+/+. The proportion of insulin cells was decreased but somatostatin and PP cells were increased in Chga−/− mice compared to Chga+/+ mice. The nuclear size was decreased in insulin cells and increased in somatostatin cells in Chga−/− mice. Plasma insulin level was markedly decreased in the Chga−/− mice although fasting plasma glucose and glucagon were normal. Conclusion: Ablation of the Chga gene affected the islet volume, the composition, distribution and nuclear size of islet cell types and plasma insulin concentration. Our data indicate decreased insulin cell function and increased glucagon cell function. Our study shows that CgA exerts a significant influence on the endocrine pancreas with importance in maintaining islet volume, cellular composition and function.
Regulatory Peptides, 2008
Prohormone convertases (PCs) are proteinases that cleave inactive prohormones to biologically act... more Prohormone convertases (PCs) are proteinases that cleave inactive prohormones to biologically active peptides. Seven PCs have been identified; two of them, PC1/3 and PC2, have only been localized in neuroendocrine (NE) tissues; a third, furin, in both endocrine and exocrine tissues.
Pancreas, 2002
Knowledge about the relation between G proteins and adenylyl cyclases (ACs) is important for the ... more Knowledge about the relation between G proteins and adenylyl cyclases (ACs) is important for the construction of signaling paradigms to increase our understanding of signal transduction in the normal state and its alterations in pathologic states, such as type-2 diabetes. The immunocytochemical expression patterns of the stimulatory Gs proteins (G alpha-s and G alpha-olf) and the in vitro Ca2+-stimulated ACs (AC1, 3, and 8) were studied in normal and spontaneously diabetic Goto-Kakizaki (GK) rat pancreatic islets with use of well-characterized antibodies. The expressions of G alpha-11 and AC2, abundant in pancreatic islets, were also studied. G alpha-s and G alpha-olf were mainly expressed in insulin cells, and G alpha-11 in glucagon cells. The immunoreactivity to G alpha-s and G alpha-olf and to AC1 and AC3 was higher in the GK islets than in the controls, whereas AC8 was found only in the diabetic islets. Strong G alpha-11 and AC2 immunoreactivity was seen equally in both animal groups. G alpha-s was colocalized with all ACs, whereas G alpha-olf was mainly colocalized with AC3, and G alpha-11 with AC1. The current findings may help in drawing a more specific signaling paradigm coupling Gs proteins to ACs.
Pancreas, 2010
Somatostatin inhibits hormone release through 5 G protein-coupled somatostatin receptors (sst1-ss... more Somatostatin inhibits hormone release through 5 G protein-coupled somatostatin receptors (sst1-sst5). However, the role of somatostatin in islet physiology is not fully known. The immunoreactivity to sst1 to sst5 in normal human endocrine pancreas has been described. The present study reports the expression of sst1 to sst5 in human pancreatic islets with type 2 diabetes mellitus. Pancreatic autopsy specimens from individuals with type 2 diabetes mellitus and matched controls were double immunostained to demonstrate sst1 to sst5 in the major islet cell types. Most apparent differences in type 2 diabetic islets were the lack of sst1 and sst4 in glucagon cells and sst1-3 and 4 in somatostatin cells, whereas minor changes were demonstrated in insulin cells. The pancreatic polypeptide cells showed a reversed staining pattern in diabetic islets compared with the controls. In type 2 diabetes mellitus, the sst pattern differed from that of the controls in somatostatin, pancreatic polypeptide, and glucagon cells, to a minor extent in insulin cells. It is unclear whether the changes in sst patterns are primarily due to the diabetes or secondary to metabolic disturbances. However, this study may be the basis for further functional studies to evaluate the role of sst1 to sst5 in the diabetic state.
Journal of Histochemistry & Cytochemistry, 2002
We studied the immunoreactivity of 12 different region-specific antibodies to the chromogranin A ... more We studied the immunoreactivity of 12 different region-specific antibodies to the chromogranin A (CgA) molecule in the various neuroendocrine cell types of the human gastrointestinal (GI) tract by using double immunofluorescence techniques. These staining results were compared with others obtained with a commercial monoclonal CgA antibody (LK2H10). G (gastrin)-cells showed immunoreactivity to virtually all region-specific antibodies, but with varying frequency. Most intestinal EC (enterochromaffin)-and L (enteroglucagon)-cells were immunoreactive to the antibodies to the N-terminal and mid-portion of the CgA molecule, whereas the EC-cells in the stomach reacted with fewer region-specific antibodies. D (somatostatin)-cells reacted to the CgA 411-424 antibody and only occasionally showed immunoreactivity to the other CgA antibodies. A larger cytoplasmic area was stained with the antibodies to than with the other antibodies tested. These differences in staining pattern may reflect different cleavage of the CgA molecule in different cell types and at different regions of the GI tract.
Journal of Histochemistry & Cytochemistry, 1997
Co-localization of chromogranin (Cg) A, B, and C has been studied in different neuroendocrine cel... more Co-localization of chromogranin (Cg) A, B, and C has been studied in different neuroendocrine cell types in histologically normal mucosa from human gastrointestinal tract (corpus, antrum, duodenum, ileum, and colon) using single-, double-, and triple-immunofluorescence stainings. Virtually all enterochromaffin (EC) cells contained CgA, and those in the luminal two thirds of the antral mucosa and villi of small intestine often also contained CgB. A few EC cells in the duodenal crypts contained CgC. Most gastrin cells harbored both CgB and CgA, although rather more CgB than CgA, but some gastrin cells contained all three types, i.e., also CgC. Some CCK cells also contained all three chromogranins. Enteroglucagon cells in the duodenal villi contained CgA and some CgB. CgA (but not B or C) was found in some secretin, GIP, enteroglucagon/peptide YY, and neurotensin cells. A few somatostatin cells contained CgA but neither CgB nor CgC. CgA and C were found mainly in the basal cell region, whereas CgB occurred more diffusely throughout the cytoplasm. This varying distribution suggests that not all secretory granules contain CgA, or that CgB may occur in a nongranular form. The varying composition of the different chromogranins may reflect their complex functional roles in the widespread neuroendocrine system. (J Histochem Cytochem 45:815-822, 1997)
Journal of Histochemistry & Cytochemistry, 2002
S U M M A R Y Chromogranin (Cg) B is an acidic glycoprotein present in neuroendocrine tissue. The... more S U M M A R Y Chromogranin (Cg) B is an acidic glycoprotein present in neuroendocrine tissue. The sequence shows several dibasic amino acid positions susceptible to proteolytic cleavage. The purpose of this study was to elucidate the expression of CgB epitopes in the human endocrine pancreas. Tissue sections of six human pancreata were immunostained with 16 different region-specific antibodies to the CgB molecule, using double immunofluorescence techniques. The CgB epitope pattern varied in the four major islet cell types. B (insulin)-cells expressed immunoreactivity to all region-specific antibodies. The antibodies to the N-terminal and mid-portions of CgB showed moderate immunoreactivity, the C-terminal antibodies weak. A (glucagon)-cells were reactive only to the N-terminal and midportion antibodies but, after microwave pretreatment, to all antibodies, whereas D (somatostatin)-cells expressed only the sequence CgB 244-255 and a subpopulation CgB 580-595. PP (pancreatic polypeptide) cells were immunostained with antibodies between CgB 1-417 and a few with CgB 580-593. The fragment CgB 244-255 was expressed in all four cell types. The cause of these differences may be cell-specific cleavage or masking of the molecule, but varying translation of CgB mRNA is also possible. The extent to which these epitopes reflect fragments having biological functions remains to be evaluated.
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Papers by Guida Portela-gomes