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At least 199 records · Page 11Linked to original sources
PubMed2003

Influence of the intramural innervation on the morphogenesis of the enteroendocrine cells and the genetic construct involved (review).

The influence of intramural intestinal innervation on the morphogenesis of the mucosa and in particular of the enteroendocrine cells (EECs) has been studied on male Wistar rats with morphometric, autoradiographic and immuno-histochemical methods in the duodenum, proximal and distal jejunum and ilium before and after myenteric ablation with benzalkonium chloride (BAC). Twenty-one days after denervation alterations were observed in the mucosal structure with thickening of the mucosa, increase in the proliferation rate and with changes in numerical and spatial distribution of D-cells, I-cells, N-cells, glucagon and glicentin i.r. L-cells and 5-HT i.r. cells which myenteric ablation caused. Analysis of the genetic constructs involved in the alterations of EECs on the EECs provide evidence for the cAMP responsive elements as the main mediator.

Animals↗
PubMed2004

The influence of neural signal transduction on EEC gene expression under consideration of chromatin, following myenteric ablation (review).

Significant numerical and spatial changes in 5-HT i.r. cells, CCK i.r. I-cells, glucagon and glicentin i.r. I-cells, somatostatin i.r. D-cells and neurotensin i.r. N-cells occur after a 98% myenteric ablation in the rat. Signal transduction from G-protein-coupled crypt cell receptors (m2, m3; VCAP1 and 2, CAP1; Y2, Y5, Y4) stimulates a cAMP-responsive transcription machinery in which phosphorylation of the cAMP-responsive elements (e.g. CREB) is the first step in initiation of transcription. A DNA pre-initiation complex (PIC), consisting of DNA transcription activators, general activators (TFIID, IIA, IIB, IIF, IIE, II-I and IIH), at least 14 different TAFIIs and CBP/300 coactivators which contain multiple enzymatic activities, associated with the central TBP (TATA-binding protein), which together bind to the RNA-polymerase II holoenzyme disrupts chromatin blockade over the promoter with or without the intervention of activated chromatin remodeling factors. CBP/p300 contains several highly conserved domains e.g., KIX, whose methylation by CARM-1 represses CREB transcription activation, but the bromo-binding domain of CBP increases CREB transcription. A similar positive/negative switch occurs in the regulation of gastrointestinal hormones by transcription factors, from Myc/Max to Mad/Max + corepressor mSin3A, during terminal differentiation of the cell. From these observations we conclude that the primary targets for neural signals are factors of the basal DNA transcriptional apparatus, whose promoter factors then activate chromatin induction, which facilitates transcription positively or negatively.

Animals↗
PubMedDate not supplied

The peculiar processing of glucagon and glucagon-related peptides in patients after pancreatectomy.

BACKGROUND/AIMS: Although, glucagon has been detected even in the serum of totally pancreatectomized patients and the origin was suggested to be the intestine, the kinetics of glucagon is not well known after pancreatectomy. In this study, we investigated the kinetics of glucagon and glucagon-related peptides and discuss the glucagon processes in the pancreas and intestine in pancreatectomy patients. METHODOLOGY: Seven patients who had undergone pancreatoduodenectomy reconstruction using Child's procedures (distal pancreatojejunostomy, choledochojejunostomy and gastrojejunostomy) (group PD) and five patients who had undergone distal pancreatectomy (group DP) served as the subjects of this study. In addition to these two groups, five patients who had undergone gastrectomy reconstructions using the Billroth II procedure (group GX), to examine whether the alimentary tract reconstructions themselves would have any effect on the kinetics of glucagon, and 10 normal subjects (group C) were also enrolled in this study. All patients received a 75-g oral glucose tolerance test in the early morning fasting state. Serum glucagon levels were assessed using the glucagon non-specific N-terminal (glucagon-like immunoreactivity: GLI) and specific C-terminal (immunoreactive glucagon: IRG) radioimmunoassays. The molecular forms of these glucagon-related peptides were also estimated using the gel filtration chromatography method before and after the 75-g oral glucose load. RESULTS: After the glucose load, serum GLIs were increased significantly in groups GX and PD suggesting that these were affected by the alimentary tract reconstructions. Serum IRGs including true pancreatic glucagon were slightly increased in groups PD and DP after oral glucose load suggesting that these paradoxical responses might be associated with the glucose tolerance deficiencies observed in both groups, but not associated with the alimentary tract reconstruction. CONCLUSIONS: The paradoxical rise of IRGs based on the findings of gel filtration chromatography were possibly due to the generated peculiar glicentin-like peptide and pancreatic glucagon from the glucagon precursor, preproglucagon, after pancreatectomy, which is processed in association with the glucose tolerance deficiencies after pancreatectomy.

Aged↗
PubMed1979

[Immunocytochemical anatomy of alpha granules in the human endocrine pancreas].

Using the sensitive protein A-gold technique for the demonstration of antigenic sites in thin section for electron microscopy it was found that in the alpha granules of human pancreas, glucagon immunoreactivity (specific, C-terminal) is restricted to the dense granule core while glicentin immunoreactivity predominates on the peripheral halo surrounding the dense core.

Cytoplasmic Granules↗
PubMedDate not supplied

Peculiar glucagon processing in the intestine is the genesis of the paradoxical rise of serum pancreatic glucagon in patients after total pancreatectomy.

BACKGROUND/AIMS: Although glucagon has been detected even in the serum of totally pancreatectomized patients and the origin was suggested to be the intestine, the kinetics of glucagon are not well known after pancreatectomy. In the present study, we investigated the kinetics of glucagon and glucagon-related peptides in pancreatectomy patients and discuss the glucagon processes. METHODOLOGY: Ten patients who had undergone total pancreatoduodenectomy reconstruction using Billroth II type procedures (group PX) and 12 normal subjects (group C) were also enrolled in this study. All patients received a 75-g oral glucose tolerance test in the early morning fasting state. Serum glucagon levels were assessed using the glucagon specific C-terminal (immunoreactive glucagon: IRG) and nonspecific N-terminal (glucagon-like immunoreactivity: GLI) radioimmunoassays. The molecular forms of these glucagon-related peptides were also estimated using the gel filtration chromatography method before and after the oral glucose load. RESULTS: After the glucose load, serum GLIs were increased significantly in group PX suggesting that these were affected by the alimentary tract reconstructions. Serum IRGs were significantly increased in group PX, but decreased in group C after oral glucose load suggesting that these paradoxical increased responses in group PX might be associated with the insulin secretion deficiencies, but not associated with the alimentary tract reconstruction. CONCLUSIONS: The paradoxical rise in IRGs based on the findings of gel filtration chromatography in group PX were possibly due to the generated peculiar glicentin-like peptide from the glucagon precursor, preproglucagon, after total pancreatectomy, which might be processed in intestines in association with the insulin deficiencies.

Adult↗
PubMed1991

Neuroendocrine carcinoma of the urinary bladder: case report and review of the literature.

A 63-year-old Japanese man complained of hematuria and pollakisuria for several months. Computed tomography and cystography disclosed an infiltrative tumor mass in the irregularly thickened apical and posterior walls of the urinary bladder. Narrowing of the vesical lumen and posterior extension of the tumor into the pelvic cavity were also noted. After palliative ureterocutaneostomy, 60 Gy irradiation was given locally. The patient died of cachexia seven months later. Autopsy revealed neuroendocrine carcinoma of the urinary bladder with extensive invasions and metastases to the pelvic and peritoneal cavities, liver, lungs, vertebrae, left kidney and retroperitoneal lymph nodes. Histologically, atypical tumor cells with eosinophilic cytoplasm formed solid nests and anastomosing cords with pseudoglandular structures. No other histologic tumor components were included. An intact urachal remnant was found at the vesical apex while features of metaplastic cystitis were absent. In addition to positive carcinoembryonic antigen and cytokeratin, the argyrophilic cancer cells were immunoreactive for neuron-specific enolase, chromogranin A, serotonin, neuropeptide Y, glicentin, somatostatin, neurotensin and calcitonin. Ultrastructurally, neurosecretory-type granules, with a mean diameter of 166 nm, were identified in the cytoplasm of the tumor cells. To discuss the histogenesis of the tumor, 44 previously reported cases of neuroendocrine carcinoma of the urinary bladder were reviewed.

Carcinoma↗
PubMed1990

[Post-translational maturation of peptides of the glucagon family. Relationship with their mode of action].

Two types of proglucagon processing have been evidenced in producing tissues (endocrine pancreas, stomach, intestine, central nervous system) using antibodies recognizing the epitopes unmasked during processing, which takes place at dibasic sites. A first type, leading essentially to glucagon, has been observed in the two former tissues; a second type, leading to peptides (oxyntomodulin and glicentin) containing an additional C-terminal octapeptide, has been shown in the two latter. All peptides are released in plasma and reach their targets: liver, fat... (control of metabolism) for glucagon and gastric mucosa (control of acid secretion) for the octapeptide-bearing peptides. The mode of action of these peptides includes receptors coupled to adenylate cyclase and a processing, at a dibasic site, of the circulating peptides leading to C-terminal fragments which act through non cyclic AMP-dependent mechanisms, such as the control of the plasma membrane calcium pump.

Animals↗
PubMed1989

Complete sequences of glucagon-like peptide-1 from human and pig small intestine.

In the small intestine, proglucagon is processed into the previously characterized peptide "glicentin" (proglucagon (PG) 1-69) and two smaller peptides showing about 50% homology with glucagon: glucagon-like peptide-1 and -2. It was assumed that the sites of post-translational cleavage in the small intestine of the proglucagon precursor were determined by pairs of basic amino acid residues flanking the two peptides. Earlier studies have shown that synthetic glucagon-like peptide-1 (GLP-1) synthesized according to the proposed structure (proglucagon 71-108 or because residue 108 is Gly, 72-107 amide) had no physiological effects, whereas a truncated from of GLP-1, corresponding to proglucagon 78-107 amide, strongly stimulated insulin secretion and depressed glucagon secretion. To determine the amino acid sequence of the naturally occurring peptide we isolated GLP-1 from human small intestine by hydrophobic, gel permeation, and reverse-phase high performance liquid chromatography. By analysis of composition and sequence it was determined that the peptide corresponded to PG 78-107. By mass spectrometry the molecular mass was determined to be 3295, corresponding to PG 78-107 amide. Furthermore, mass spectrometry of the methyl-esterified peptide showed an increase in mass compatible with the presence of alpha-carboxyl amidation. Thus, the gut-derived insulinotrophic hormone GLP-1 is shown to be PG 78-107 amide.

Amino Acid Sequence↗
PubMed1989

Enteroendocrine cells in the developing opossum small intestine and colon.

Enteroendocrine cells immunoreactive for gastrin, bovine pancreatic polypeptide (BPP), glucagon (glicentin), 5-hydroxytryptamine (5-HT), somatostatin, secretin, motilin, gastric inhibitory peptide (GIP) and cholecystokinin (CCK) are scattered throughout the small intestinal epithelium of the newborn opossum and in all later postnatal stages examined. The number of BPP- and glucagon-immunoreactive cells is relatively high in the newborn and rapidly decreases until only occasional cells are present after the first postnatal week. Cells immunoreactive for GIP, CCK, 5-HT, motilin, gastrin and secretin increase in number with development. Secretin-, motilin-, CCK- and GIP-immunoreactive cells generally are concentrated proximally in the small intestine and as they increase in number, differentiate in more distal regions. The number of gastrin-immunoreactive cells actually decreases just prior to weaning but then increases at and after, weaning. Neurotensin-immunoreactive cells are unusual in that they do not appear until about the 74th postnatal day and then are first encountered in the distal small intestine. As development progresses they increase in number and appear in the more proximal regions. Cells immunoreactive for 5-HT at first increase but then decrease sharply at weaning only to increase markedly again after this time. In contrast, somatostatin-immunoreactive cells gradually decrease in number until weaning then dramatically increase. If the total number of enteroendocrine cells in the small intestine is considered, there is a gradual decrease from birth until weaning when a dramatic increase occurs. Cells immunoreactive for neurotensin, 5-HT and somatostatin are also found in the intestinal epithelium of the developing colon and caecum. Somatostatin- and 5-HT-immunoreactive cells are found throughout the colon in the newborn whereas neurotensin-immunoreactive cells, although observed initially in the proximal colon, do not form a significant population until weaning and then are concentrated distally.

Animals↗
PubMed1986

Multiple endocrine neoplasia type I: assessment of laboratory tests to screen for the gene in a large kindred.

We measured multiple components of serum or plasma in 221 members of a kindred with familial multiple endocrine neoplasia type 1 (FMEN1). The kindred showed typical features of FMEN1; the FMEN1 gene could be traced through 7 generations with 74 members identifiable as gene carriers. Between family screening in 1981 and completion of our study in 1985, we identified 16 previously unscreened members as carriers of the FMEN1 gene. The earliest age at diagnosis of FMEN1 was 17. The tests with the greatest yield of abnormal results among carriers of the FMEN1 gene were albumin-adjusted calcium, PTH, gastrin, and (in females) prolactin. The following tests provided little or no use in identifying carriers: prolactin (in males), pancreatic polypeptide, glucagon, glicentin, insulin, growth hormone, motilin, and somatostatin. Primary hyperparathyroidism was the commonest expression of the FMEN1 gene; the gene penetrance for this trait increased from near 0% before age 15 to near 100% after age 40. It appeared prior to development of serious morbidity from hypergastrinemia or hyperprolactinemia. All 42 co-operating members who were alive and expressing the FMEN1 gene in 1984 showed active or treated primary hyperparathyroidism. Primary hypergastrinemia had a prevalence below half of that for primary hyperparathyroidism at all ages and was not diagnosed in the absence of primary hyperparathyroidism. Primary hyperprolactinemia was still less prevalent than primary hypergastrinemia. It was limited almost exclusively to females.

Adolescent↗
PubMed1987

Glucagon gene transcription in an islet cell line is regulated via a protein kinase C-activated pathway.

Proglucagon is a polyprotein precursor containing not only glucagon and glicentin, but glucagon-like peptides-I and -II and an intervening peptide (IP-II). The glucagon gene is expressed in both pancreatic islets and neuroendocrine L-cells of the gastrointestinal tract. We have recently cloned an islet cell line from a rat pancreatic islet cell tumour that simultaneously expresses the glucagon, insulin, somatostatin, and angiotensinogen genes. We investigated the potential role of "second messenger" pathways in the regulation of glucagon gene expression. Both the tumor promoter agent phorbol myristate acetate (PMA) and a diacylglycerol analog, 1,2-dioctanoylglycerol, induced a 2.7- and 2.5-fold increase in steady-state glucagon mRNA levels at 24 h, respectively. The increase was progressive up to 24 h and was specific for glucagon mRNA; the insulin and somatostatin mRNA levels remained unchanged. An inactive phorbol ester, 4 beta-phorbol 12,13,20-triacetate, was without effect. The glucagon mRNA increase induced by PMA was mediated through an increase in glucagon gene transcription reaching maximal stimulation at 30-60 min. Glucagon mRNA half-life was similar in both control and PMA-treated cells, approximating 12 h. The stimulation of glucagon gene transcription was accompanied by a corresponding 3-fold increase in proglucagon biosynthesis. Neither dibutyryl cAMP nor glucocorticoids affected glucagon mRNA levels, while inducing a 5-fold increase in somatostatin mRNA levels and 4.8-fold stimulation in angiotensinogen mRNA at 24 h, respectively. We conclude that expression of the glucagon gene in this islet cell line is regulated at the level of transcription through a protein kinase C (Ca2+/phospholipid-dependent enzyme)-activated pathway.

Angiotensinogen↗
PubMed1988

Naturally occurring products of proglucagon 111-160 in the porcine and human small intestine.

Recent studies have revealed that the glucagon gene is expressed in the mammalian intestine. Here it codes for "glicentin" (proglucagon 1-69) and a glucagon-like peptide, proglucagon 78-107, recently isolated from porcine intestine. We studied the fate of the remaining COOH-terminal part of proglucagon (proglucagon 111-160) using radioimmunoassays against proglucagon 111-123 and 126-160. Two peptides were isolated from acid ethanol extracts of porcine ileal mucosa and sequenced: one corresponding to proglucagon 126-158 and one probably corresponding to proglucagon 111-158. By comparing human and porcine proglucagon sequences, Ala117 is replaced by Thr, and Ile138, Ala144, Ile152 and Gln153 are replaced by Val, Thr, Leu, and His. By gel filtration and radioimmunoassay of intestinal extracts it was established that a large part of porcine and virtually all of human proglucagon are processed to release proglucagon 111-123 (designated spacer peptide 2), which, like proglucagon 126-158 must be considered a potential hormonal entity. By isocratic high pressure liquid chromatography human spacer peptide 2 was indistinguishable from synthetic proglucagon 111-122 amide, suggesting that this is the structure of the naturally occurring human peptide.

Amino Acid Sequence↗
PubMed1986

Preproglucagon gene expression in pancreas and intestine diversifies at the level of post-translational processing.

Glucagon is a pancreatic hormone of 29 amino acids that regulates carbohydrate metabolism and glicentin is an intestinal peptide of 69 amino acids that contains the sequence of glucagon flanked by peptide extensions at the amino and carboxy termini. The glucagon gene encodes a precursor containing glucagon and two additional, structurally related, glucagon-like peptides separated by an intervening peptide. These peptides are encoded in separate exons. To determine whether the pancreatic and intestinal forms of glucagon arise by alternative RNA and/or protein processing, we used antisera to synthetic glucagon-like peptides and exon-specific, complementary oligonucleotides for analyses of proteins and mRNAs in pancreatic and intestinal extracts. Preproglucagon mRNAs are identical, but different and highly specific peptides are liberated in the two tissues. Immunocytochemistry shows colocalization of glucagon and the two glucagon-like peptides in identical cells. We conclude that diversification of preproglucagon gene expression occurs at the level of cell-specific post-translational processing.

Amino Acid Sequence↗
PubMed1986

Immunohistochemical study of gastroenteropancreatic endocrine cells of the herbivorous Japanese field vole, Microtus montebelli.

The gastroenteropancreatic (GEP) endocrine cells of the Japanese field vole were studied immunohistochemically. Somatostatin-, 5-hydroxytryptamine-, glicentin-, glucagon-, bovine pancreatic polypeptide-, gastrin-, gastric inhibitory polypeptide-, cholecystokinin-, substance P-, secretin-, neurotensin- and insulin-immunoreactive cells were revealed. The characteristic findings of the regional distribution and relative frequency of these immunoreactive cells in the GEP system of the vole were as follows. Somatostatin-immunoreactive cells were more numerous in the oxyntic glands than in the pyloric glands. Some somatostatin-immunoreactive cells were found in small clusters in the oxyntic glands. Gastrin-immunoreactive cells were detected not only in the pyloric glands and small intestine but also in the caecum and spiral colon. Gastric inhibitory polypeptide-immunoreactive cells were also detected in the pyloric glands and no motilin-immunoreactive cell was found in the gastroenteropancreatic system.

Animals↗
PubMed1985

Glucagon and VIP in the retina.

Immunoreactive glucagon and immunoreactive vasoactive intestinal polypeptide (VIP) have been demonstrated in neuronal elements in the retina of a number of species by immunohistochemistry. In the present study, the concentrations of glucagon-like and VIP-like material in retinae from different species were determined by radioimmunoassay. The retinal concentration of glucagon-like immunoreactivity was 10-35 pg/mg in goldfish, chicken, pigeon, and frog, whereas retinae from cow, pig, rabbit, and rat contained very little. Retinae from the latter four species were on the other hand rich in VIP-like material whereas retinae from cat, guinea pig, and goldfish contained very little. The glucagon-like immunoreactive material in chicken and frog retina was subjected to gel chromatography and high performance liquid chromatography (HPLC). The results indicate that the extracted protein is of similar molecular size as porcine pancreatic glucagon, distinct from porcine glicentin. VIP immunoreactive material extracted from bovine retina was similar in molecular size as authentic porcine VIP by gel chromatography.

Animals↗
PubMed1979

Endocrine cells in the intestinal metaplasia of gastric mucosa.

Sections of gastric mucosa removed during surgery for cancer or peptic ulcer and containing regions of intestinal metaplasia were studied by the immunofluorescence technique using several antiserums against intestinal hormones. Endocrine cells such as cells containing somatostatin, glicentin (gut GLI-I), motilin, and probably cholecystokinin were found within metaplastic intestinal epithelium while secretin and neurotensin, which are present in the normal intestinal mucosa, were not detected in metaplastic epithelium. The endocrine-cell population present in the intestinal metaplasia resembles that found in the cryptal region of the normal small intestine, a finding in accordance with the fact that intestinal metaplasia of gastric mucosa usually reproduces structural and histochemical characteristics of small intestinal crypts.

Adult↗
PubMed1984

On the contamination of commercially available aprotinins with pancreatic islet peptides.

Contamination of aprotinins with immunoreactive insulin, glicentin, glucagon, somatostatin, pancreatic polypeptide and pancreatic polypeptide-icosapeptide was estimated by radioimmunoassay. High somatostatin concentrations were found in two commercial preparations. Influence of somatostatin contamination of aprotinins on the clinical as well as the laboratory applications of aprotinin may thus be anticipated.

Aprotinin↗
PubMed1981

The diffuse endocrine-paracrine system of the gut in health and disease: ultrastructural features.

At least 16 types of endocrine-paracrine cells have been identified ultrastructurally in the gastrointestinal mucosa. The production of hormones and local messengers such as 5-hydroxytryptamine, gastrin, cholecystokinin, somatostatin, secretin, gastric inhibitory peptide (GIP), enteroglucagon (glicentin, GLI), motilin, neurotensin, substance P and the enkephalins, by these cells, has been established. Progress has also been made in cytological studies of gut and pancreatic endocrine tumours. Argentaffin EC cell carcinoids, gastrinomas (of several ultrastructurally different varieties of gastrin cells), L-cell tumours and D-cell tumours are among those cytologically and functionally defined in the gut. Functionally undefined tumours include the so-called non-argentaffin carcinoids arising in various parts of the gut, some of which have been characterised cytologically as gastric ECL cell tumours and gastroduodenal P-D1-cell tumours. Gastrinomas, vipomas and rare argentaffin carcinoids are among gut-related pancreatic endocrine tumours. Non-functional paragangliomas, usually with some neuromatous component, occur in the duodenal wall. Extrapancreatic vipomas display ultrastructural features of ganglioneuroblastomas with peptidergic granules.

Animals↗