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Biomedical subjects

R De Giorgio

Publications and source records attributed to R De Giorgio.

At least 55 records · Page 3Linked to original sources
PubMed1999

Involvement of endogenous tachykinins and CGRP in the motor responses produced by capsaicin in the guinea-pig common bile duct.

In functional experiments, we have investigated the effect exerted by neurotransmitters released from capsaicin-sensitive primary afferent nerve terminals in the isolated guinea-pig common bile duct. In resting preparations, capsaicin (0.1 microM) produced a quick contraction (45.1+/-4% of KCl 80mM) which was abolished by either atropine (1 microM) or tetrodotoxin (0.5 microM). The tachykinin receptor-selective antagonists GR 82334 (NK1 receptor-selective; 3 microM), MEN 11420 (NK2 receptor-selective; 1 microM) and SR 142801 (NK3 receptor-selective; 0.1 microM) administered separately failed to reduce the capsaicin-evoked contraction, whereas any combination of the three antagonists was effective: GR 82334 plus MEN 11420, 36+/-7% reduction; GR 82334 plus SR 142801, 48+/-4% reduction; MEN 11420 plus SR 142801, 55+/-3% reduction; GR 82334 plus MEN 11420 plus SR 142801, 57+/-5% reduction. Neither the CGRP1 receptor antagonist h-CGRP (8-37) (1.5 microM) nor the P2X purinoceptor antagonist PPADS (50 microM) affected the contractile response to capsaicin. The effect of capsaicin (0.1 microM) was abolished by pretreatment with capsaicin itself (10 microM for 15 min). Human calcitonin gene-related peptide (h-CGRP; 0.1 microM) mimicked the effect of capsaicin on resting preparations (contractile response =28% of KCl 80 mM). In preparations precontracted with a submaximal concentration of KCl (24 mM), and in the presence of atropine (1 microM), GR 82334 (3 microM) and MEN 11420 (3 microM), capsaicin (1 microM) produced a tetrodotoxin-insensitive long-lasting relaxation (45+/-3% reduction of tone, at 4min from administration), which was unaffected by the nitric oxide (NO) synthase inhibitor, L-NOARG (100 microM). h-CGRP (10-50 nM) produced a similar sustained relaxation of precontracted preparations (59+/-4% reduction of tone). h-CGRP (8-37) (1.5 microM) almost completely reversed the relaxations produced by both capsaicin and h-CGRP. Application of electrical field stimulation (EFS: trains of stimuli of 10Hz; 0.25ms pulse width; supramaximal voltage; for 60s) to precontracted preparations produced a sustained, tetrodotoxin (1 microM)-sensitive relaxation (32+/-4% reduction of tone). L-NOARG (100 microM) greatly reduced (69+/-5% inhibition) the EFS-elicited relaxation. A complete reversal of the relaxant response to EFS into a contraction was obtained by administering L-NOARG to preparations in which a functional blockade of capsaicin-sensitive primary afferent neurons had been achieved by incubating the tissue with capsaicin (10 microM) for 15 min. At immunohistochemistry, tachykinin- and CGRP-immunoreactivities (TK-IR/CGRP-IR) were detected in varicose nerve fibers throughout the common bile duct, while TK-IR cell bodies were observed in the terminal portion (ampulla) only. In vivo pretreatment with capsaicin (50 mg/kg; 6-7 days before) decreased the number of CGRP-IR nerves, whereas the TK-IR neural network was apparently unchanged. In conclusion, our data provide functional evidence for the presence of capsaicin-sensitive primary afferent nerve endings in the guinea-pig terminal biliary tract, whose stimulation by capsaicin or EFS produces the release of tachykinins and CGRP. In addition, morphological evidence is provided that the bulk of TK-IR material in the biliary tract is contained in intrinsic neuronal elements, while CGRP in this tissue is of extrinsic origin only. Tachykinins, probably released in small amounts by capsaicin, act by activating receptors of the NK1, NK2 and NK3 type, most probably located on intrinsic cholinergic neurons, which in turn release ACh to produce the final excitatory motor response. The contractile response to capsaicin obtained in the presence of the three tachykinin receptor antagonists could be due to the co-released CGRP and/or to other unknown neurotransmitters. CGRP produces either indirect excitatory or direct inhibitory responses by stimulation of CGRP2 and CGRP1 receptors, respectively.

Animals↗
PubMed1999

Expression of cholecystokinin A receptors in neurons innervating the rat stomach and intestine.

BACKGROUND & AIMS: Two distinct receptors, cholecystokinin (CCK)-A and CCK-B, mediate CCK effects in the digestive system. The aim of this study was to elucidate the cellular sites of expression of CCK-A receptor in the rat stomach and small intestine. METHODS: We developed and characterized an antibody to the N-terminal region (LDQPQPSKEWQSA) of rat CCK-A receptor and used it for localization studies with immunohistochemistry. RESULTS: Specificity of the antiserum was demonstrated by (1) detection of a broad band at 85-95 kilodaltons in Western blots of membranes from CCK-A receptor CHO-transfected cells; (2) cell surface staining of CCK-A receptor-transfected cells, (3) translocation of CCK-A receptor immunostaining in CCK-A receptor-transfected cells after exposure to CCK; and (4) abolition of tissue immunostaining by preadsorbtion of the antibody with the peptide used for immunization. CCK-A receptor immunoreactivity was localized to myenteric neurons and to fibers in the muscle and mucosa. In the stomach, myenteric neurons and mucosal fibers were abundant. Many CCK-A receptor myenteric neurons contained the inhibitory transmitter vasoactive intestinal polypeptide, and some were immunoreactive for the excitatory transmitter substance P. Subdiaphragmatic vagotomy reduced the density of CCK-A receptor fibers in the gastric mucosa by approximately 50%, whereas celiac/superior mesenteric ganglionectomy had no detectable effect on fiber density. CONCLUSIONS: CCK-A receptor is expressed in functionally distinct neurons of the gastrointestinal tract. CCK-A receptor may mediate reflexes stimulated by CCK through the release of other transmitters from neurons bearing the receptor.

Amino Acid Sequence↗
PubMed1999

Tachykinin NK(1)receptor-mediated inhibitory responses in the guinea-pig small intestine.

We used in vivo, in vitro studies and immunohistochemistry to elucidate the mechanisms activated by tachykinin NK(1)receptors in evoking inhibitory motor response in the guinea-pig small intestine. In vivo, the selective NK(1)receptor agonist GR 73,632 produced a dose-dependent suppression of the distension-induced duodenal contractions, and a decrease of basal tone. These effects were reduced by pretreatment with the NK(1)receptor antagonist SR 140,333. In L-Nomega-nitro-L-arginine methylesther hydrochloride-pretreated animals, the suppressant effect of GR 73,632 on duodenal contractions was reduced, whereas the relaxation of the basal tone was unaffected. In vitro, GR 73,632 evoked a biphasic response consisting of a transient, tetrodotoxin-sensitive inhibitory effect followed by tetrodotoxin-resistant contractions. SR 140,333 blocked both inhibitory and excitatory motor responses induced by GR 73,632. NK(1)immunoreactivity was localized to myenteric and submucosal neurons and to interstitial cells of Cajal in the deep muscular plexus of the small intestine. NK(1)receptor-expressing neurons had Dogiel type I morphology and many of them were beta-nicotinamide adenine phosphate dinucleotide-diaphorase-positive, indicating they are inhibitory neurons. In conclusion, in the guinea-pig small intestine, NK(1)receptor stimulation evokes a myogenic excitatory motor response and a neurogenic inhibitory motor response that involves, at least in part, a nitrinergic pathway.

Adrenergic Agents↗
PubMed1999

Predominant symptoms identify different subgroups in functional dyspepsia.

OBJECTIVE: Dyspepsia is a common syndrome that often defies diagnosis. Whether the unexplained (or "functional") dyspepsia represents a homogeneous syndrome or includes different subgroups with specific clinical features has not been clarified. The aim of this study was to investigate the relationship between symptom severity, demographic features, and gastric dysmotility in a large series of patients with functional dyspepsia. METHODS: Severity of individual digestive symptoms, demographic features, and scintigraphic gastric emptying of solids were evaluated in 483 patients with chronic unexplained dyspepsia. RESULTS: Two main subgroups were identified. The first was characterized by predominant epigastric pain, male gender (61%), and normal gastric emptying. The second subgroup was characterized by predominant nonpainful symptoms, female gender (60%), a high frequency of associated irritable bowel syndrome (30%), and delayed gastric emptying (42%). A third group included approximately one-third of patients who did not present with any predominant symptom, and was characterized by a high frequency of delayed gastric emptying (30%), overlapping irritable bowel syndrome (28%), and gastroesophageal reflux disease (41%). CONCLUSIONS: Different subgroups exist among patients with functional dyspepsia seen in a referral center. They can be identified by the predominant symptom and are characterized by different demographic, clinical, and pathophysiological features.

Adult↗
PubMed1999

Esophageal and gastric nitric oxide synthesizing innervation in primary achalasia.

OBJECTIVE: We performed a qualitative and quantitative analysis of the nitrinergic neurons in the esophageal and gastric component of the lower esophageal sphincter (LES) and gastric fundus of patients with primary achalasia. METHODS: Four muscle strips were obtained from the esophagogastric junction (two from the esophageal and two from the gastric side of the LES), and two from the gastric fundus of six patients with endstage achalasia who underwent an esophagogastric myotomy plus hemifundoplication. Control specimens were obtained from eight patients who underwent surgery for cancer of the thoracic esophagus. Fixed sections were processed for NADPH-diaphorase histochemistry and the number (mean +/- SE) of nitrinergic neurons per section was visually quantified in each specimen. RESULTS: In the controls, nitric oxide fibers were distributed to the muscle layer and surrounding myenteric neurons of both the LES and the gastric fundus. By contrast, achalasic patients showed a marked decrease of nitric oxide nerves and labeled neurons in both esophageal and gastric components of the LES and the gastric fundus. Quantitative assessment in achalasic patients showed that the mean number of nitrinergic neurons was dramatically reduced in both the esophageal (0.2 +/- 0.1) and the gastric component (2 +/- 0.6) of the LES as compared to those in controls (15 +/- 5 and 12 +/- 4, respectively; p < 0.05); nitrinergic neurons in the gastric fundus (3 +/- 1) were significantly reduced in comparison to those of controls (10 +/- 2) (p < 0.05). CONCLUSIONS: Our results indicate that achalasia is a motor disorder with an intrinsic inhibitory denervation of the esophageal and gastric component of the LES and of the proximal stomach, thus providing further evidence for an extraesophageal extension of the disease.

Adult↗
PubMed1999

How should Helicobacter pylori negative patients be managed?

Dyspepsia is a digestive syndrome distinct from (although frequently overlapping with) gastro-oesophageal reflux disease (GORD) and irritable bowel syndrome (IBS), which is characterised by various combinations of painful and non-painful symptoms arising from the epigastrium. Dyspepsia can be secondary to a variety of diseases, but in most instances it is idiopathic. Helicobacter pylori infection is responsible for the majority of peptic ulcers and of other diseases potentially associated with dyspepsia. Nevertheless, a causal role for H pylori infection in symptom occurrence has not been established. Experimental data indicate that H pylori eradication does not improve symptoms in the majority of dyspeptic patients. It has been proposed recently that H pylori negative patients should be managed according to their clinical presentation. Some reports suggest that taking into consideration the most relevant or "predominant" symptom may help to identify distinct subgroups among dyspeptic patients with different underlying pathophysiological abnormalities and different responses to treatment. Well designed and conducted prospective studies are needed to verify whether treatment of H pylori negative dyspeptic patients based on the predominant symptom actually is a cost effective approach.

Dyspepsia↗
PubMed1999

A histological and immunohistochemical study of neuropeptide containing somatic nerves in the levator ani muscle of women with genitourinary prolapse.

BACKGROUND: To evaluate the changes occurring in the somatic innervation throughout the levator ani muscle in women with genitourinary prolapse and stress urinary incontinence (SUI). METHODS: Thirty-four patients with genital prolapse entered the study and ten subjects with non-malignant pathologies acted as a control group. All patients were evaluated by urodynamic investigation and an electromyographic study of pelvic floor muscles to define the type of urinary incontinence. Biopsy samples were obtained from both groups of patients: the site of muscle biopsies were left and right part of perirectal pubococcygeus muscle. The evaluation of immunoreactivity was semiquantitative and based on staining intensity and distribution. RESULTS: In all cases, S-100 protein and NSE immunoreactivities were found in nerve fascicles running throughout the striated muscle. NPY and VIP positivities were more intense and diffuse, whereas SP immunoreactivity was quite scanty. The different patterns of NPY and VIP expression changed in relation to degree of genital prolapse and to the presence of SUI. CONCLUSIONS: Our immunohistochemical study shows the presence in the pelvic floor of neurons that are able to synthesize neuropeptides. The lower immunoreactivity score of same neuropeptides (VIP, NPY) observed among patients with third degree genital prolapse and with SUI could be related to biochemical damage of the neurons with subsequent lower production of chemical messengers.

Aged↗
PubMed1998

Detection of substance P immunoreactivity in human peripheral leukocytes.

The neuropeptide substance P (SP) has a marked proinflammatory effect and modulates the immune response. In this study, we tested the hypothesis that human peripheral leukocytes contain SP. Resting peripheral leukocytes collected from healthy volunteers (n = 20) were studied by applying a SP rabbit polyclonal antiserum to both flow cytometry and immunohistochemistry. To identify possible changes in Sp expression, we also analyzed both activated T-lymphocytes (cell cultures; n = 5 normal subjects) and neoplastic hematologic samples of different types of leukemias. Flow cytometry showed that normal granulocytes and monocytes contained SP, whereas lymphocytes were generally negative (or weakly positive) with the exception of a few (10-20%) positive subsets. In comparison, activated T-lymphocytes were markedly immunolabeled by SP as well as samples from neoplastic patients demonstrated strong SP immunoreactivity in all cell lineages. This pattern was confirmed by immunohistochemistry on cytospins. Our results support a potential role for SP-mediated immunomodulatory mechanisms both in normal and pathological conditions.

Flow Cytometry↗
PubMed1998

Evidence that tachykinins are the main NANC excitatory neurotransmitters in the guinea-pig common bile duct.

Application of electrical field stimulation (EFS; trains of 10 Hz, 0.25 ms pulse width, supramaximal voltage for 60 s) to the guinea-pig isolated common bile duct pretreated with atropine (1 microM), produced a slowly-developing contraction ('on' response) followed by a quick phasic 'off' contraction ('off peak' response) and a tonic response ('off late' response), averaging 16+/-2, 73+/-3 and 20+/-4% of the maximal contraction to KCl (80 mM), n=20 each, respectively. Tetrodotoxin (1 microM; 15 min before) abolished the overall response to EFS (n 8). Neither in vitro capsaicin pretreatment (10 microM for 15 min), nor guanethidine (3 microM, 60 min before) affected the excitatory response to EFS (n 5 each), showing that neither primary sensory neurons, nor sympathetic nerves were involved. Nomega-nitro-L-arginine (L-NOARG, 100 microM, 60 min before) or naloxone (10 microM, 30 min before) significantly enhanced the 'on' response (294+/-56 and 205+/-25% increase, respectively; n=6-8, P<0.01) to EFS. The combined administration of L-NOARG and naloxone produced additive enhancing effects (655+/-90% increase of the 'on' component, n = 6, P<0.05). The tachykinin NK2 receptor-selective antagonist MEN 11420 (1 microM) almost abolished both the 'on' and 'off late' responses (P<0.01: n=5 each) to EFS, and reduced the 'off-peak' contraction by 55+/-8% (n=5, P<0.01). The subsequent administration of the tachykinin NK1 receptor-selective antagonist GR 82334 (1 microM) and of the tachykinin NK3 receptor-selective antagonist SR 142801 (30 nM), in the presence of MEN 11420 (1 microM), did not produce any further inhibition of the response to EFS (P>0.05; n=5 each). At 3 microM, GR 82334 significantly reduced (by 68+/-9%, P<0.05, n=6) the 'on' response to EFS. The contractile 'off peak' response to EFS observed in the presence of both MEN 11420 and GR 82334 (3 microM each) was abolished (P<0.01; n=6) by the administration of the P2 purinoceptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS, 30 microM). PPADS (30 microM) selectively blocked (75+/-9 and 50+/-7% inhibition, n = 4 each) the contractile responses produced by 100 and 300 microM ATP. Tachykinin-containing nerve fibres were detected by using immunohistochemical techniques in all parts of the bile duct, being distributed to the muscle layer and lamina propria of mucosa. In the terminal part of the duct (ampulla) some labelled ganglion cells were observed. In conclusion, this study shows that in the guinea-pig terminal biliary tract tachykinins, released from intrinsic neuronal elements, are the main NANC excitatory neurotransmitters, which act by stimulating tachykinin NK2 (and possibly NK1) receptors. ATP is also involved as excitatory neurotransmitter. Nitric oxide and opioids act as inhibitory mediators/modulators in this preparation.

Animals↗
PubMed1998

Constipation: a common problem in patients with neurological abnormalities.

Constipation is a frequent complaint among patients with different neurological diseases. This review provides a brief account of the numerous conditions affecting the central, peripheral and intrinsic (enteric) nervous systems in which constipation can be the only clinical manifestation or a component of a complex syndrome. Recent neuropathophysiological acquisitions show that any structural or functional impairment of the intrinsic innervation of the gut, including both developmental (i.e., Hirschsprung's disease and intestinal neuronal dysplasia) and acquired (i.e., either degenerative or inflammatory neuropathies) disorders, can be associated with constipation. Constipation may also arise from derangements of the peripheral nervous system, including diabetes and primary chronic autonomic failure (pandysautonomias). Finally, in the central nervous system, a wide array of disorders (post-traumatic, degenerative, ischaemic or neoplastic) are recognized to determine bowel dysfunction, ultimately leading to constipation. Further understanding of the fine pathophysiological mechanisms through which the intrinsic and extrinsic nerve supplies to the digestive system are involved in idiopathic constipation or in diseases generating this symptom will hopefully lead to a better treatment of this frequent pathological condition.

Central Nervous System Diseases↗
PubMed1997

NK1 receptor expression in the interstitial cells of Cajal and neurons and tachykinins distribution in rat ileum during development.

The origin and function of the interstitial cells of Cajal (ICCs) that are located at the level of the deep muscular plexus (DMP) have not been completely identified. It has been recently reported that these cells express neurokinin-1 (NK1) receptors to which substance P (SP) shows the highest affinity. Studies during pre- and postnatal life have demonstrated that ICCs are identifiable in the rat ileum soon after birth and already show adult features at 7 days of postnatal life. Several neurotransmitters have been identified at the DMP which appear at specific times during development. We have studied the expression of NK1 receptors by ICCs and enteric neurons and the timing of the appearance of SP in the DMP, myenteric plexus (MP) and submucous plexus (SMP) of rat ileum during development. Rats, aged from 18 days of fetal life to adulthood, were used. NK1 receptors and SP were identified by using NK1 polyclonal antibodies and tachykinin (SP/TK) polyclonal antibodies, respectively. NK1-immunoreactivity (IR) was detected in the ICCs immediately after birth and reached maximal intensity at 7 days. From birth, SP/TK-IR fibers originated from short excitatory neurons at the MP and reached the DMP at 1 week of postnatal life. NK1- and SP/TK-IR appeared in the MP neurons in the fetus and in the SMP neurons at weaning. The present study demonstrates that by the first days of postnatal life, the NK1-IR might be used as a marker of the ICCs at the DMP and suggests that these cells may participate in the actions exerted by tachykinins on muscle cells.

Animals↗
PubMed1997

Widespread eradication of Helicobacter pylori: a debate.

BACKGROUND: Helicobacter pylori eradication is recommended currently only in peptic ulcer patients. The accumulating evidence of a possible pathogenetic role of the germ in other pathological conditions, such as mucosa-associated lymphoid tissue lymphomas and (possibly) also functional dyspepsia and gastric cancer, creates increasing pressure in favor of an expansion of such indication. However, at present, cultural and practical considerations should discourage widespread screening and eradication programs. METHODS: The basis for our study is a critical review of the literature. RESULTS: The lack of a sound pathophysiological basis linking H. pylori infection to both dyspeptic symptom perception and gastric cancer risk sharply contrasts with the numerical and clinical relevance of these pathological conditions. Screening tests are not sufficiently cheap, easy, and reliable to be applicable on a large scale. Also, eradication therapies may provide suboptimal therapeutic effects and excessive side effects if applied by physicians who are not prepared culturally. CONCLUSIONS: Improvement of pathophysiological, diagnostic, and therapeutic knowledge must be achieved before eradication programs can be proposed on a large scale.

Helicobacter Infections↗
PubMed1996

Vesicular monoamine transporter 2 expression in enteric neurons and enterochromaffin-like cells of the rat.

The cellular localization of the vesicular monoamine transporter 2 (VMAT2) in the rat digestive tract was investigated with immunohistochemistry. VMAT2-immunoreactivity (IR) was localized to neurons and fibers of enteric and pancreatic ganglia, to processes supplying the gut wall, the pancreas and blood vessels, and to enterochromaffin-like (ECL) cells in the gastric corpus, which contained calbindin-IR. Few VMAT2-IR cells were also found in the gastric antrum, but they did not contain gastrin-IR. VMAT2-IR was expressed in extrinsic sympathetic fibers as demonstrated by the elimination of a portion of VMAT2-IR processes by sympathectomy. The VMAT2-IR pattern is consistent with the overall distribution of biogenic amine cell groups in the digestive tract. Our results provide further evidence that VMAT2 is the vesicular amine transporter responsible for accumulation of monoamines into secretory vesicles of monoaminergic neurons and ECL cells.

Animals↗
PubMed1996

In vivo evidence for the involvement of tachykinin NK3 receptors in the hexamethonium-resistant inhibitory transmission in the rat colon.

In urethane-anaesthetized rats, moderate colonic distention (0.5 ml) induced reflex rhythmic contractions (5 mm Hg amplitude and 1.1 cycles/min frequency). Senktide (1-10 nmol/kg, i.v.), a tachykinin NK3 receptor selective agonist, transiently suppressed distension-induced contractions. SR 142,801 (1-10 mumol/kg i.v.), a non-peptide tachykinin NK3 receptor antagonist, had no effect on distension-induced contractions but prevented the inhibitory effect of senktide. Infusion of N-omega-nitro-1-arginine methyl esther hydrochloride (L-NAME, 20 mumol/ml/h, i.v) increased the amplitude of colonic contractions and decreased the inhibitory effect of senktide. Hexamethonium (15 mumol/ml/h, i.v.) or atropine (1 mumol/ml/h, i.v.) inhibited the distension-induced contractions. In hexamethonium- or atropine-treated rats, senktide (10 nmol/kg) transiently and selectively enhanced the amplitude of contractions. Also SR 142,801 (10 mumol/kg), but not its inactive enantiomer SR 142,806, increased both amplitude and frequency of contractions. During continuous infusion of L-NAME and hexamethonium or atropine both frequency and amplitude of distension-induced colonic contractions were higher than when in hexamethonium or atropine only. Senktide (10 nmol/kg) had no effect and SR 142,801 (10 mumol/kg) produced a slight enhancement of colonic contractions. Infusion of sodium nitroprusside (3 mumol/ml/h, i.v.) decreased amplitude and frequency of distension-induced contractions. SR 142,801 had no effect in the presence of the nitric oxide (NO) donor. We conclude that tachykinins acting through NK3 receptors exert at least four different actions on colonic motility activated by distension: 1) a hexamethonium-resistant, NO-dependent, suppressant effect on contractions; 2) a hexamethonium-sensitive, NO-independent inhibitory effect on the amplitude of contractions; 3) a hexamethonium-resistant, NO-independent inhibitory effect on the amplitude of contractions and 4) a hexamethonium resistant and L-NAME-sensitive excitatory effect on amplitude of contractions. The prevalent inhibitory effect evoked in normal conditions along with the excitatory activity induced by SR 142,801 on hexamethonium-resistant colonic motility indicates that tachykinins, acting through neuronal NK3 receptors, activate NO-dependent and NO-independent inhibitory neurotransmission in the rat colon.

Adrenergic Agents↗