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C Sternini

Publications and source records attributed to C Sternini.

At least 55 records · Page 3Linked to original sources
PubMed1995

Peptide immunoreactivities in the ganglionated plexuses and nerve fibers innervating the human gallbladder.

The mammalian gallbladder is innervated by a well-developed intrinsic neural network. However, little is known about the neurochemistry and organization of the innervation of this organ in humans. The aim of this study was to analyze the distribution of immunoreactivity (IR) for the neuropeptides, vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), tachykinins (TK) and calcitonin gene-related peptide (CGRP) in the human gallbladder by means of immunohistochemistry. Neuropeptide-IRs are found in neurons and processes of the two ganglionated plexuses, i.e., the innermost plexus located in the lamina propria at the base of the mucosal folds, and the outermost plexus situated within the fibro-muscular layer. In these two plexuses, VIP-, NPY- and TK-IRs are present in ganglion cells and varicose fibers, whereas CGRP-IR is confined to nerve processes. VIP-IR is present in most, if not all, neurons. NPY- and TK-IRs are also found in many neurons. The densities of the peptide-IR nerves in the mucosa are NPY and VIP > TK >> CGRP, and in the fibro-muscular layer are NPY > VIP and TK > CGRP. The vasculature is richly innervated by NPY-IR nerves, which are mostly perivascular. CGRP-, VIP- and TK-IR processes are found only occasionally around blood vessels and in a paravascular position. Double-label studies demonstrated that a large number of VIP-containing neurons expresses NPY- or TK-IR. On the other hand, all neurons positive for either NPY- or TK-IR are immunostained for VIP. In agreement with these findings, most of the NPY-IR fibers in the lamina propria and fibro-muscular layer contain VIP-IR, and numerous TK-IR fibers are positive for VIP. However, the perivascular NPY-IR processes do not contain VIP-IR, suggesting an extrinsic origin. In addition, a population of TK-IR processes contains CGRP-IR and presumably originates from extrinsic sources, since CGRP/TK-IR intrinsic neurons could not be detected in the gallbladder. Peptide-IRs have a similar distribution in the neck, body and fundus of the gallbladder. No peptide-containing endocrine/paracrine cells are observed in the epithelium. The presence of peptide-IRs in the ganglionated plexuses and the abundance of peptidergic innervation suggest that peptides exert their effects on gallbladder function by acting directly on tissue targets and influencing intrinsic ganglion cells. Furthermore, the co-localization of more than one peptide in the same neuron raises the possibility that peptides are co-released upon stimulation and might interact at the same target.

Gallbladder↗
PubMed1995

Up-regulation of transforming growth factor alpha binding sites in experimental rabbit colitis.

BACKGROUND & AIMS: Transforming growth factor alpha (TGF-alpha), a member of the epidermal growth factor family, has been proposed to mediate protection against mucosal injury and promote healing of the gastrointestinal mucosa. TGF-alpha acts via a plasma membrane receptor, which is distributed throughout the digestive system with the highest density in epithelia. The aim of this study was to investigate the pattern of TGF-alpha binding sites in the normal and inflamed rabbit colon. METHODS: The immune complex/formalin model of acute colitis and tissue section receptor autoradiography were used. Inflammation was characterized by cellular infiltration, edema, and necrosis. TGF-alpha binding relative density was determined by densitometry on film autoradiograms. RESULTS: The normal colon had a low to moderate density of specific TGF-alpha binding sites in the mucosa and external muscle. TGF-alpha binding density was significantly increased in the mucosa at 4 hours and remained higher than normal for up to 48 hours. The density of binding sites in the mucosa and the inflammatory index returned to near normal values at 96 hours, when colitis had subsided. CONCLUSIONS: The increase in TGF-alpha binding in the mucosa during experimental colitis supports the hypothesis that members of the epidermal growth factor family play a role in inflammation, perhaps acting as mediators of mucosal protection and repair.

Acute Disease↗
PubMed1995

Production of a rat pancreatic polypeptide-specific monoclonal antibody and its influence on glucose homeostasis by in vivo immunoneutralization.

To test the effect of endogenous pancreatic polypeptide (PP) on rat hepatic glucose homeostasis by immunoneutralization, a rat PP-specific monoclonal antibody (MAb) was produced. Binding of this IgG1 monoclonal antibody was inhibited 50% by 350 pM rat PP. Immunohistochemistry showed that the antibody produced the expected pattern of endocrine cell staining in rat pancreas. Groups of six adult male Sprague-Dawley rats were given 5 mg of Protein-A-purified anti-PP MAb or anti-KLH MAb (control) ip every 48 hr for 5 dosing intervals. The rate of hepatic glucose output during isolated liver perfusion was 0.25 +/- 0.03 mg/g/min for the PP MAb-treated rats and 0.17 +/- 0.02 mg/g/min for the control group (p < 0.05). Liver glycogen content was 21.8 +/- 2.9 mg/g for the PP MAb-treated rats and 14.7 +/- 2.4 mg/g for the control group (N = 5). Chronic in vivo immunoneutralization of PP with this new monoclonal antibody suggests that PP influences glucose homeostasis in the rat by affecting hepatic glucose output.

Animals↗
PubMed1995

Differential expression of two vesicular monoamine transporters.

Specific transport proteins package classical neurotransmitters into vesicles so that their release can be regulated by neural activity. Previous studies have suggested that a single activity mediates the vesicular transport of monoamines in the adrenal gland, brain, and other tissues such as mast cells and platelets. However, molecular cloning has recently identified two vesicular transporters for monoamines. Although the predicted proteins are closely related in sequence, they show a range of differences in their physiologic and pharmacologic properties. To clarify further the biological significance of the observed functional differences, we have generated anti-peptide antibodies to the C-termini of the two transporters and used them to determine the distribution and localization of the proteins in the rat. We have detected expression of vesicular monoamine transporter 1 (VMAT1) in adrenal chromaffin cells but not in neural cells. Interestingly, some adrenal chromaffin cells also express VMAT2 but the amount of VMAT2 relative to VMAT1 appears much lower than in the bovine adrenal gland. In contrast, sympathetic ganglion cells express only VMAT2, as do enteric neurons and enterochromaffin-like cells of the stomach. Thus, although adrenal chromaffin cells, sympathetic and enteric neurons derive from the neural crest, they express different vesicular amine transporters. In the CNS, dopamine, norepinephrine, epinephrine, 5-HT, and histamine cell groups all express VMAT2. These findings are consistent with the functional characteristics of VMAT1 and VMAT2 and help to explain several classic pharmacological observations. VMAT2-immunoreactivity is generally stronger in cell bodies, proximal dendrites and axonal processes, indicating the potential for monoamine storage at each of these sites. Surprisingly, dopaminergic interneurons in the olfactory bulb show no detectable immunoreactivity for either VMAT1 or VMAT2.

Adrenal Glands↗
PubMed1994

Fos protein expression in the nucleus of the solitary tract in response to intestinal nutrients in awake rats.

Nutrients in the intestine inhibit food intake via an action on the vagal afferent pathway. The aim of the present study was to use immunochemical detection of Fos protein-like immunoreactivity (FLI) in the brainstem to trace the neuronal pathways activated by intestinal nutrients. Perfusion of the intestine of awake rats via an indwelling duodenal catheter with iso-osmotic mannitol, hydrochloric acid or casein hydrolysate had no effect on the number of FLI neurons in the nucleus of the solitary tract (NTS). Lipid emulsion (20%) and 2.7 M glucose significantly increased the number of immunopositive cells in the NTS. There was a significant increase in the number of immunopositive cells from caudal to rostral NTS. Nutrients effective at decreasing food intake (carbohydrate and fat) produced significant increases in Fos-like immunopositive cells in the NTS.

Animals↗
PubMed1994

The conserved NPXnY motif present in the gastrin-releasing peptide receptor is not a general sequestration sequence.

Exposure of the gastrin-releasing peptide (GRP) receptor to agonists causes a rapid desensitization of the receptor-stimulated mobilization of intracellular calcium. Homologous desensitization occurs by uncoupling the G-proteins from the receptor and by ligand induced internalization. The molecular determinants of desensitization of the GRP receptor are not well known. The importance of tyrosine 324 which is located in a highly conserved NPX2-3 Y motif of the GRP receptor was investigated. Kirsten murine sarcoma virus-transformed rat kidney (KNRK) cells were transfected with expression vectors encoding either the wild type or the mutant (tyrosine 324 to alanine 324) rat GRP receptor. The wild type and mutant GRP receptors were expressed at a high level in the KNRK cells, 2.0 x 10(6) and 0.5 x 10(6) receptors per cell, respectively. The wild type and mutant GRP receptors bound GRP with the same affinity (Kd = 6-7 nM). KNRK cells expressing the wild type or mutant GRP receptor had similar [Ca2+]i, dose response to GRP. KNRK cells expressing the GRP receptor rapidly internalized bound 125I-GRP at 37 degree C. Internalization was inhibited at 4 degrees C and by 0.45 m sucrose. The internalization of bound 125I-GRP by the mutant GRP receptor was identical to the wild type receptor. Fluorescent microscopy was used to directly observe the GRP receptor expressed on the surface of the KNRK cells and to visualize its ligand induced internalization. There was no difference in the pattern of internalization between the wild type and mutant GRP receptors expressed in KNRK cells. Therefore, the highly conserved tyrosine 324 does not have a role in GRP binding, receptor-G-protein interaction, or initial events of ligand induced receptor internalization. The NPXnY motif is not a general sequestration sequence for seven transmembrane G-protein linked receptors.

Amino Acid Sequence↗
PubMed1994

Nitric oxide producing neurons in the monkey and human digestive system.

Nitric oxide has been proposed as an inhibitory transmitter molecule that plays a role in muscle relaxation and vasodilation in the gastrointestinal tract. The present study analyzes the distribution of nitric-oxide-producing neurons in the monkey and human digestive system by means of nicotinamide-adenine-dinucleotide-phosphate-diaphorase histochemistry. This histochemical method is reliable and convenient for the visualization of neuronal nitric-oxide synthase, the enzyme responsible for nitric-oxide generation. In the gastrointestinal tract, nitric-oxide-synthase-related diaphorase activity was present in nerve fibers running throughout the muscular layer (circular > longitudinal) and in numerous ganglion cells and processes in the myenteric plexus of monkeys and humans. Labelled ganglion cells and fibers also were observed in the submucous plexus, although they were much less numerous than those seen in the myenteric plexus. In the submucosa, a few positive fibers were seen around blood vessels. In the mucosa, stained fibers were sparse at the base of the villi and crypts, whereas they were quite abundant in the muscularis mucosae, especially in the small intestine and colon. In the gallbladder (human), labelling was found in ganglion cells and processes of the innermost and outermost ganglionated plexuses. Stained fibers also were distributed to the muscular layer and, less abundantly, to the mucosa and vasculature. Labelled fibers were more abundant in the sphincter of Oddi (human) than in the gallbladder. In the monkey and human pancreas, nicotinamide-adenine-dinucleotide-diaphorase staining was seen mainly in ganglion cells and fibers of intrapancreatic ganglia, and in processes running among acini, around ducts and in the stroma. A moderate density of stained fibers also was distributed to the vasculature, whereas the islets showed few positive processes. Finally, double label experiments performed in the pancreas showed that the vast majority of neurons producing nitric oxide are immunoreactive for vasoactive intestinal peptide.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Use of the Fab fragment for immunoneutralization of somatostatin in the isolated perfused human pancreas.

The role of the somatostatin-secreting D cell in the islet remains controversial. The present study was undertaken to determine whether infusion of the Fab fragment of a highly sensitive somatostatin monoclonal antibody into the isolated, perfused human pancreas would influence insulin secretion. Single-pass perfusion was performed in pancreata obtained from cadaveric organ donors using a modified Krebs-media with 3.9 mM glucose. Sequential test periods separated by basal periods were performed with either somatostatin monoclonal antibody Fab fragment (SFab), somatostatin-14 (SS-14), or a combined infusion. Immunoneutralization of intraislet somatostatin with SFab resulted in a significant increase in both immunoreactive insulin (IRI) (1,122 +/- 497 pM) (p < 0.05) and immunoreactive C-peptide (IRC-P) secretion (146 +/- 53 pM) (p < 0.05). Infusion of SS-14 resulted in inhibition of both IRI secretion (-3,372 +/- 1,360 pM) (p < 0.05) and IRC-P secretion (-708 +/- 220 pM) (p < 0.05). Combined infusion of SFab and SS-14 reversed the inhibitory effect of exogenous SS-14 on IRI and IRC-P secretion. The data suggest that intraislet somatostatin has an inhibitory role in the regulation of B-cell secretion in the human islet and demonstrates that the Fab fragment of the somatostatin monoclonal antibody is an effective tool for immunoneutralization studies in the human pancreas. In addition, immunostaining of the donor pancreata demonstrated the presence of somatostatin-immunoreactive endocrine cells interspersed throughout the islet core and mantle. The demonstrated proximity of somatostatin-immunoreactive endocrine cells to B cells lends anatomic support to the concept that intraislet somatostatin influences insulin secretion in the human islet.

Adult↗
PubMed1993

Abdominal surgery induces c-fos expression in the nucleus of the solitary tract in the rat.

In a model of abdominal surgery, which consisted of cecal manipulation and induces postoperative ileus in rats, we studied c-fos protein expression in the nucleus of the solitary tract (NTS), the spinal cord and dorsal root ganglia. Abdominal surgery resulted in a significantly higher number of c-fos protein immunoreactive cells in the NTS compared with controls but not in dorsal root ganglia and resulted in only a few scattered cells in the spinal cord. Neurons expressing c-fos protein were concentrated in NTS regions where cecal afferents terminate. These findings support the hypothesis that sensory vagal pathways partly mediate abdominal surgery-induced postoperative ileus.

Abdomen↗
PubMed1993

Monoclonal antibody to rat alpha-CGRP: production, characterization, and in vivo immunoneutralization activity.

Spleen cells from a Robertsonian mouse immunized with rat alpha-CGRP were fused with FOX-NY cells to induce hybridoma cells. Antibody activities were screened by radioimmunoassay, and hybridomas producing high affinity antibodies were cloned by limiting dilutions. Ascites were produced from the highest affinity clone in pristine-primed Balb/c mice. Ascites fluid contained approximately 20 mg/ml IgG which was of subclass IgG2a as determined by immunodiffusion analysis. The titer of this IgG2a antibody titled #4901, was 1:2,000,000 and the ID50 for rat alpha-CGRP, rat beta-CGRP and human alpha-CGRP were 350, 4000, and 4500 pg/ml respectively. Protein A purified CGRP antibody #4901 (5-10 mg/kg) completely abolished the portal release of somatostatin and the inhibition of gastric acid secretion induced by intravenous infusion of rat alpha CGRP (15-20 micrograms/kg/h) in anesthetized rats. The unpurified antibody (25 mg/kg) also prevented the fall in mean arterial blood pressure and the increase in heart rate caused by intravenous injection of rat alpha-CGRP. Immunohistochemistry showed that CGRP monoclonal antibody stains nerve fibers and endocrine-like cells in the pancreas, and neuronal elements in the gastrointestinal tract. These results show that CGRP monoclonal antibody #4901, which is relatively specific for rat alpha-CGRP, is useful for in vivo immunoneutralization of CGRP and is also an excellent reagent for immunohistochemical localization of alpha- and beta-CGRP in mammals.

Amino Acid Sequence↗
PubMed1993

Differential effects of experimentally induced chronic pancreatitis on neuropeptide immunoreactivities in the feline pancreas.

The distribution and concentration of calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), and gastrin-releasing peptide (GRP) immunoreactivities in the pancreas of cats with experimentally induced chronic pancreatitis and of age- and sex-matched controls were investigated. By narrowing the main pancreatic duct between the head and the body to approximately 25% of its normal diameter, we induced within 5 weeks chronic pancreatitis restricted to the body and tail. In control animals, peptide immunoreactive nerves were distributed to the islets, acini, and ducts; the latter were predominantly innervated by fibers immunoreactive for NPY, VIP, or CGRP. The vasculature received an abundant supply of NPY-, CGRP-, and, to a lesser extent, SP-containing axons. Within intrapancreatic ganglia, peptide immunoreactivities were identified in fibers and ganglion cells, with the exception of CGRP and SP immunostaining, which could be visualized only in fibers. In animals with chronic pancreatitis, the innervation pattern of each peptidergic system was comparable to that described in controls. However, there was a remarkable increase in the density and staining intensity of VIP and NPY immunoreactive fibers in the exocrine parenchyma and fibrous septa of the body and tail, where chronic pancreatitis developed. Fibers immunoreactive for CGRP and SP also were moderately denser than in controls, whereas those containing GRP immunoreactivity did not show any detectable changes. In addition, a marked increase of the immunostaining for VIP and, to a much lesser extent, for NPY and GRP, was observed in neurites supplying the head of the pancreas, which appeared devoid of histologically detectable pathological alterations. Radioimmunoassay analysis confirmed the immunohistochemical observations. The increased density of distinct peptidergic nerves in the pancreas with induced chronic pancreatitis might be the result of compensatory phenomena in response to the inflammatory process.

Animals↗
PubMed1993

Distribution and abundance of neutral endopeptidase (EC 3.4.24.11) in the alimentary tract of the rat.

The distribution of neutral endopeptidase (NEP; EC 3.4.24.11) was examined in the alimentary tract of the rat. Immunoreactive NEP and NEP mRNA were localized to epithelial cells of the small intestine and to muscle cells in the stomach, small intestine, and colon by immunohistochemistry and in situ hybridization histochemistry. NEP antisera recognized a protein on Western blots of membranes from gastric, jejunal, and colonic mucosa and gastric muscle with an electrophoretic mobility identical to that of recombinant human NEP (approximately 95 kDa). An antisense cRNA probe to NEP hybridized to RNA of approximately 3.5 kb and approximately 6.5 kb, corresponding to the primary transcripts of rat NEP, on Northern blots of total RNA from the jejunal mucosa. NEP message was detected in mRNA from jejunal and colonic mucosa and gastric, jejunal, and colonic muscle using a ribonuclease protection assay. NEP enzymatic activity, assessed by DL-thiorphan-inhibitable degradation of glutaryl-Ala-Ala-Phe-4-methoxy-2-naphthylamine, was highest in homogenates of jejunal mucosa (868 +/- 98 pmol.h-1 x micrograms protein-1) and was between 49- and 413-fold lower in other gastrointestinal tissues. The cellular origin of NEP in the gastric and colonic mucosa could not be determined.

Animals↗
PubMed1992

Calcitonin gene-related peptide neurons innervating the canine digestive system.

The pattern of nerve cells and fibers containing calcitonin gene-related peptide immunoreactivity (CGRP-IR) was investigated in the canine digestive tract by means of immunohistochemistry. CGRP-IR nerve fibers innervate all the layers of the gut, including the vasculature, with different densities depending on the region. CGRP-IR processes are sparse in the esophagus and stomach, where they are mostly confined to the enteric plexuses and vasculature. CGRP-IR fibers are quite abundant in the small and large intestine, where they form dense arborizations in the mucosa, and are numerous in the muscularis mucosae, deep muscular plexus and circular muscle. The myenteric and submucous plexuses of the intestine contain dense networks of CGRP-IR fibers and numerous CGRP-IR ganglion cells. On the other hand, in the enteric ganglia of the esophagus and stomach, in the intrapancreatic ganglia and in the ganglionated plexus of the gallbladder, CGRP-IR is restricted to non-varicose processes. A moderate density of CGRP-IR fibers supplies the endocrine and exocrine pancreas, and the fibromuscular layer and lamina propria of the gallbladder. The density of CGRP innervation in different regions can be summarized as follows: intestine >> pancreas and gallbladder > or = antrum > cardia > gastric corpus and distal esophagus. CGRP- and tachykinin (TK)-IRs are colocalized in a substantial population of fibers, particularly those distributed to the mucosa, muscularis mucosae and vasculature, whereas there was no evidence of colocalization in intrinsic ganglion cells. The present results suggest that (1) the CGRP innervation of the dog digestive system includes an intrinsic and an extrinsic component, and (2) CGRP- and TK-IRs are co-expressed in extrinsic nerve fibers. These findings extend previous observations in rats and guinea pigs and provide insights into the sites of action of CGRP in the digestive system of the dog, which has served as a model for CGRP functional studies.

Animals↗
PubMed1992

Calcitonin gene-related peptide in inflammatory bowel disease and experimentally induced colitis.

Pronounced changes in gut neuropeptide content have been observed in colonic tissues from animals with acute experimental colitis and in some patients with inflammatory bowel disease. The early decrease of CGRP in the colon during colitis in the animal studies suggest that CGRP is released during the inflammatory process. No data are available showing the biological action of released CGRP during inflammation. The sensory neurotoxin capsaicin was used in animal studies to examine the effect of sensory nerves on inflammation and healing in experimental animal models. The severity of colitis was enhanced after capsaicin pretreatment in acute and chronic animal models of colitis. These data support the hypothesis that sensory nerves exert a protective and healing-promoting function in the gut. CGRP is a good candidate for this action of sensory nerves because it is a major component in sensory nerve fibers. How CGRP exerts its protective function in the intestine is unknown. Data from gastric ulcer models support the hypothesis that a main action of CGRP is regulation of mesenteric and mucosal blood flow resulting in enhanced protection and tissue healing. Other effector roles of CGRP afferent nerve endings could also be considered.

Animals↗