Biomedical subjects

G Soldani

Publications and source records attributed to G Soldani.

At least 37 records · Page 2Linked to original sources

PubMed1998

Manufacturing and microscopical characterisation of polyurethane nerve guidance channel featuring a highly smooth internal surface.

The present study demonstrates the possibility of manufacturing polyurethane [ChronoFlex (CF)] nerve guidance channels (NGCs) featuring a highly smooth internal surface. Comparative SEM and AFM observations prove marked differences between the internal surface microgeometry of Silastic and CF channels. SEM of CF samples shows a surface with no detectable roughness, while Silastic channels show transversal rows along the entire surface. AFM digital image of Silastic samples show a surface with a rough microgeometry defined by a tridimensional pattern with peaks up to 1400 nm. AFM digital image of CF samples show, indeed, an essentially flat microgeometry with the highest level at 545 nm. These preliminary results suggest that the association of an innovative sequential deposition manufacturing technique with the new CF polyurethane may produce NGCs with a smoother surface microgeometry, in comparison to NGCs obtained from commercial Silastic tubes.

Biocompatible Materials↗

PubMed1998

Effects of beta3-adrenoceptor agonist SR 58611A on gastric acid secretion and histamine release in the dog: comparison with ritodrine.

1. The involvement of beta3 adrenoceptors in the control of gastric acid secretion and histamine release was investigated in the dog. 2. In conscious dogs, SR 58611A (0.0625-1.0 mg/kg/hr i.v.) dose dependently inhibited gastric acid secretion induced by pentagastrin. Maximal inhibition (40%) was obtained with the dose of 1 mg/kg. Ritodrine (1 mg/kg/hr i.v.) also induced a marked inhibition (85%) of gastric acid secretion stimulated by pentagastrin. 3. On 2-deoxy-D-glucose-stimulated acid secretion, both SR 58611A and ritodrine at 1 mg/kg/hr i.v. showed inhibitory effects. On these experiments, ritodrine, but not SR 58611A, significantly reduced plasma gastrin concentrations. 4. In anaesthetized dogs, histamine concentrations from gastrosplenic vein increased fivefold after the infusion of pentagastrin. SR 58611A (1 mg/kg/hr i.v.) did not significantly modify the stimulant effect of pentagastrin on histamine release. In contrast, ritodrine (1 mg/kg/hr i.v.) significantly inhibited histamine release induced by pentagastrin. 5. These data suggest that beta3 adrenoceptors may participate in the negative control of gastric acid secretion in the dog, probably through a histamine-independent mechanism.

Adrenergic beta-Agonists↗

PubMed1997

The plasma kinetics and tissue distribution of enrofloxacin and its metabolite ciprofloxacin in the Muscovy duck.

The disposition and tissue distribution of enrofloxacin and of its main metabolite ciprofloxacin were investigated in ducks after oral or intramuscular administration of a single dose of 10 mg/kg enrofloxacin. Plasma and tissue concentrations were determined by a HPLC method. The peak concentrations of enrofloxacin after intramuscular administration (1.67 micrograms/ml at 0.9 h) were higher than after an oral dose (0.99 microgram/ml at 1.38 h). The relative bioavailability of enrofloxacin after administration directly into the crop was 68%, while the metabolic conversion of enrofloxacin to ciprofloxacin was quite low (< 10%) with both routes of administration. High tissue concentrations and high tissue:plasma concentration ratios were demonstrated for enrofloxacin and ciprofloxacin 24 h after treatment. It was concluded that a dose of 10 mg/kg per day provides serum and tissue concentrations sufficiently high to be effective in the control of many infectious diseases of ducks.

Administration, Oral↗

PubMed1996

Modulation of pentagastrin-induced histamine release by histamine H3 receptors in the dog.

BACKGROUND: The histamine H3 receptor has been shown to inhibit pentagastrin-induced gastric acid secretion in dogs. Since pentagastrin releases histamine in dogs, we have now assessed whether the effects of H3-receptor ligands may be indirectly mediated by changes in gastric histamine release. METHODS: Pentagastrin infusions (1 or 6 micrograms/kg/h), alone or together with the H3-receptor agonist (R) alpha-methylhistamine (1.2 mumol/kg/h) or the antagonist thioperamide (0.1 mumol/kg/h), were performed in dogs. One group (anaesthetized) was used for enzyme immunoassays of plasma histamine and, when required. (R) alpha-methylhistamine in the gastrosplenic vein, and another group (non-anaesthetized) for measurement of gastric acid secretion. RESULTS: Histamine levels were increased five- and eight-fold after 1 and 6 micrograms/kg/h pentagastrin, respectively, whereas acid output was nearly maximal at the lower dosage. (R) alpha-methylhistamine, at a plasma concentration of 0.15 microM, inhibited histamine release by 78% (P < 0.007) and 37% (not significant) and the total acid output by 44% (P < 0.05) and 19% (not significant) after infusion of 1 and 6 micrograms/kg/h pentagastrin, respectively. Thioperamide, together with pentagastrin in low dose, significantly increased histamine release by 212% (P < 0.05), whereas acid output increased by 34% (not significant). CONCLUSIONS: The histamine H3 receptor mediates a negative feedback control of pentagastrin-induced release of gastric histamine. It is tonically activated by endogenous histamine after pentagastrin in low dosage. The control of acid secretion by the H3 receptor seems to involve modulation of endogenous histamine release, possibly by means of enterochromaffin-like cells.

Animals↗

PubMed1996

Pharmacokinetics of enrofloxacin and its metabolite ciprofloxacin after intravenous and intramuscular administrations in sheep.

OBJECTIVE: To evaluate the pharmacokinetics of enrofloxacin and its metabolite ciprofloxacin after administrations of enrofloxacin in sheep. DESIGN: Crossover study performed by i.v. and i.m. administrations of 2.5 mg of enrofloxacin/kg of body weight to 2 groups of 3 sheep. After a 15-day resting period, the drug administration was repeated, using the alternative route. ANIMALS: 6 clinically normal Massese sheep of either sex. PROCEDURE: Blood samples were collected at suitable intervals over a 24-hour period, and plasma concentrations of enrofloxacin and its main metabolite ciprofloxacin were determined by a high-performance liquid chromatography method. Pharmacokinetic variables for both substances after i.v. and i.m. enrofloxacin administrations were calculated by use of statistical moments and were analyzed, using a crossover ANOVA. RESULTS: After i.v. administration of enrofloxacin, a rapid distribution phase was followed by a slower elimination phase. When the same dose was administered IM, enrofloxacin was rapidly and almost completely absorbed, with bioavailability of 85%. After 24 hours, the mean plasma concentration of ciprofloxacin was similar to that of the parent drug. CONCLUSIONS: The large volume of distribution indicates that enrofloxacin is widely distributed in the body of sheep. The fraction of enrofloxacin metabolized to ciprofloxacin (35 and 55% for i.v. and i.m. administrations, respectively) suggests that, in this species, the antimicrobial activity of enrofloxacin could be attributable, at least in part, to its main metabolite ciprofloxacin. CLINICAL RELEVANCE: i.v. or i.m. administration of 2.5 mg of enrofloxacin/kg provides plasma concentrations higher than mean inhibitory concentration for most pathogens in sheep.

Analysis of Variance↗

PubMed1996

Biochemical and genetic interactions of two commercial pesticides with the monooxygenase system and chlorophyllin.

Two commercial preparations of atrazine and zineb were tested on a diploid D7 strain of the yeast Saccharomyces cerevisiae using cells from logarithmic growth phase (with a high level of cytochrome P-450) and from stationary growth phase. The compounds induced marked increases of both gene conversion and point mutation frequencies in the logarithmic phase cells, while in the stationary phase no genotoxic effect was observed. The results obtained employing TA98 and TA100 strains of Salmonella typhimurium (Ames test) confirmed that neither atrazine nor zineb were mutagenic. The interaction between zineb and chlorophyllin, a known antimutagen in several biological systems, has been evaluated in yeast cells from logarithmic growth phase. The results showed that chlorophyllin seems to have a protective role against the genotoxic effects of zineb. The in vivo effects on cytochrome P-450 content (Cyt. P-450) and on monooxygenase activities were examined in hepatic microsomes of induced animals (rat, pig, and rabbit) 24 hrs after acute treatment. The results obtained with atrazine showed that it caused different effects in the three animal species. Preliminary data with zineb indicated that it can act both as an inducer or as an inhibitor of the monooxygenase system, depending on the dose used.

Animals↗

PubMed1995

Enrofloxacin-theophylline interaction: influence of enrofloxacin on theophylline steady-state pharmacokinetics in the beagle dog.

Enrofloxacin, a quinolone antibiotic developed exclusively for use in animals, was investigated for its effects on the steady-state pharmacokinetics of theophylline in six healthy Beagle dogs. A sustained-release theophylline formulation was given alone (20 mg/kg per os twice daily at 12 h intervals) for 9 days and then co-administered with enrofloxacin (5 mg/kg i.v. once a day) for 5 days. Mean trough theophylline concentrations progressively and significantly increased during the five days of enrofloxacin co-administration. Theophylline clearance and concentration-time profile were significantly changed by enrofloxacin co-administration. No significant change was observed in enrofloxacin pharmacokinetics. The kinetic interaction between theophylline and enrofloxacin could be of clinical significance and may require plasma drug concentration monitoring and adjustment of theophylline dosage.

Administration, Oral↗

PubMed1994

Regulation of gastric acid secretion by histamine H3 receptors in the dog: an investigation into the site of action.

The involvement of histamine H3 receptors in the regulation of gastric acid secretion was investigated in the conscious dog with gastric fistula, by the use of the selective agonist (R)alpha-methylhistamine and the selective antagonist thioperamide. (R)alpha-methylhistamine (0.3-1.2 mumol/kg/h) induced a dose-related inhibition of the acid secretion induced by pentagastrin and by bombesin, maximum inhibition not exceeding 60-65%. The inhibitory effect of the H3 agonist (0.6 mumol/kg/h) was inhibited by thioperamide (0.1 mumol/kg/h), suggesting that the effect was entirely mediated by H3 receptors. Thioperamide was also able to enhance the acid response to submaximal doses of pentagastrin and bombesin. The acid secretion induced by histamine was not modified by (R)alpha-methylhistamine (0.3-1.2 mumol/kg/h) but it was significantly enhanced by thioperamide (0.1 mumol/kg/h). Neither (R)alpha-methylhistamine nor thioperamide significantly modified the increase in plasma gastrin levels induced by bombesin. In conclusion these data demonstrate that histamine H3 receptors may represent an effective mechanism for the negative control of stimulated gastric acid secretion in the dog; however, since the inhibition was mainly evident against stimuli which involve the release of histamine, a location of H3 receptors in paracrine cells of the gastric mucosa rather than in gastrin producing cells or parietal cells seems more likely.

Animals↗

PubMed1994

Effects of medetomidine on intestinal and colonic motility in the dog.

The motor responses of the jejunum and colon to stimulation of alpha 2-adrenoceptors by medetomidine and clonidine were investigated in four dogs. In fasting dogs, medetomidine, at a dose rate of 30 micrograms/kg i.v., disrupted the migrating myoelectric complex (MMC) pattern of the small intestine for about 2 h. Similar, but shorter-lasting effects were also induced by clonidine (30 micrograms/kg i.v.) on the jejunum. The administration of alpha 2-agonists inhibited colonic motility in fasting dogs, although medetomidine-induced inhibition was preceded by a short period of increased muscle tone. All these effects were reversed by the alpha 2-antagonists atipamezole (0.15 mg/kg i.v.) and yohimbine (0.20 mg/kg i.v.). In fed dogs, medetomidine (30 micrograms/kg i.v.) induced a strong increase of the tone on the proximal colon, while the activity of the medium and distal colon was completely suppressed. Yohimbine (0.50 mg/kg i.v.) immediately restored the activity of the colon and induced a propagated giant contraction and defaecation by the animal. These data confirm the importance of alpha 2-adrenergic receptors in the control of intestinal and colonic motility in the dog.

Adrenergic alpha-Agonists↗

PubMed1994

Regulation of gastrin release in the dog by alpha 2-adrenoceptors.

1. The purpose of the present study was to analyse the effects of the alpha 2-adrenoceptor agonist medetomidine and the antagonist yohimbine on gastrin release in conscious dogs. 2. Gastrin secretion was investigated under both basal conditions and stimulation by 2-deoxy-D-glucose, food or bombesin. 3. Basal gastrin under fasting conditions was significantly reduced by medetomidine and increased by yohimbine. 4. 2-deoxy-D-glucose-induced gastrin increase was fully inhibited by medetomidine; this effect was antagonized by yohimbine. 5. Medetomidine significantly inhibited food-induced increase in plasma gastrin; under these conditions yohimbine was without effect per se, but significantly antagonized the inhibitory action of medetomidine. 6. Gastrin release induced by bombesin was not affected by medetomidine or yohimbine. 7. These results suggest that alpha 2-adrenoceptors play an inhibitory role under conditions in which gastrin release is mainly mediated through cholinergic and non-cholinergic nervous pathways; in contrast, they do not indicate the presence of alpha 2-adrenoceptors on G cells of the dog stomach.

Adrenergic alpha-Agonists↗

PubMed1994

Synthesis, platelet anti-aggregating activity and anti-inflammatory activity of a series of beta-aminoxypropionic acids.

This paper reports the platelet anti-aggregating activity induced by arachidonic acid (AA) and by adenosine-diphosphate (ADP), together with the anti-inflammatory activity evaluated by the carrageenan-induced rat paw edema method, of a series of beta-aminoxypropionic acids which were projected and synthesised as analogues of non-steroidal anti-inflammatory drugs with an arylacetic structure B, in which the aromatic group is substituted by a methyleneaminoxymethylic moiety. Some of the beta-aminoxypropionic acids were evaluated for their capacity to inhibit the cyclooxygenase enzyme by measuring the malondialdehyde (MDA) produced by incubation of sodium arachidonate with platelet-rich plasma (PRP).

Animals↗

PubMed1993

The role of peripheral opioid receptor subtypes in the modulation of gastric acid secretion and plasma gastrin in dogs.

The peripheral opioid receptor subtypes involved in the regulation of gastric acid secretion were studied in dogs with both a gastric fistula and a Heidenhain pouch, by using the putative mu-opioid receptor agonist dermorphin, the delta-opioid receptor agonist [D-Ala2,D-Leu5]enkephalin (DADLE) and the kappa-opioid receptor agonist dynorphin-(1-13). Dermorphin caused a significant increase in basal acid secretion from both the gastric fistula and the Heidenhain pouch, while DADLE and dynorphin-(1-13) did not. Acid secretion stimulated by 2-deoxy-D-glucose from the gastric fistula was not modified by dermorphin and dynorphin-(1-13), while DADLE significantly inhibited it; at the same time gastric secretion from the Heidenhain pouch was significantly increased by dermorphin and unmodified by DADLE and dynorphin-(1-13). Dermorphin, DADLE or dynorphin-(1-13) did not modify plasma gastrin during basal or 2-deoxy-D-glucose-stimulated conditions. Submaximal bethanechol-stimulated secretion was increased by dermorphin and DADLE but unaffected by dynorphin-(1-13). Acid secretion from the gastric fistula stimulated by pentagastrin was enhanced by dermorphin, inhibited by DADLE and unaffected by dynorphin-(1-13). Dermorphin and DADLE significantly increased acid secretion from the Heidenhain pouch stimulated by pentagastrin, while dynorphin-(1-13) was ineffective. Naloxone prevented the stimulatory effects of dermorphin and DADLE on the Heidenhain pouch, but it reduced acid secretion from the gastric fistula further when given with DADLE. The inhibitory effects of DADLE on secretion from the gastric fistula were prevented by naltrindole, a selective antagonist of delta-opioid receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Histamine H3 receptor-mediated inhibition of gastric acid secretion in conscious dogs.

The effect of (R)alpha-methylhistamine (MH) and thioperamide (selective agonist and antagonist respectively of histamine H3 receptors) was examined in conscious gastric fistula dogs to investigate the role of histamine H3 receptors in the control of basal and stimulated gastric acid secretion. Intravenous infusion of MH at 0.3 and 0.6 mumol/kg/h caused a significant reduction of the 2-deoxy-D-glucose (2-DG)-stimulated acid output, maximal inhibition being 60%. The inhibitory effect of MH was counteracted by thioperamide (0.1 mumol/kg/h), which, by itself, did not modify the 2-DG-induced acid secretion. The increase in plasma gastrin levels induced by 2-DG was not significantly affected either by MH or by thioperamide. Under basal conditions MH (0.3 mumol/kg/h) did not induce any significant change in acid secretion and in plasma gastrin levels; by contrast, thioperamide (0.1 mumol/kg/h) produced a significant increase both in acid output and in plasma gastrin. These results suggest that activation of H3 receptors can exert a negative control in stimulated acid secretion in conscious dogs, when cholinergic pathways to acid secretion are activated by 2-DG; moreover, the slight, but significant, stimulatory effect of thioperamide on basal acid output and basal plasma gastrin may be suggestive for a tonic inhibitory role of H3 receptors in the regulation of basal acid secretion, however, a nonspecific effect of this drug cannot be excluded.

Animals↗

PubMed1993

Inhibitory cholinergic effects of esaprazole on gastric secretion and plasma gastrin levels in the dog.

The effects of esaprazole, a novel antiulcer drug, on gastric acid secretion and plasma gastrin levels were investigated in dogs provided with a gastric fistula or Heidenhain pouch. Esaprazole affected in a different extent the tests performed on dogs with a gastric fistula. The greatest inhibitory effect was obtained against 2-deoxy-D-glucose-induced acid output and gastrin release. An intermediate inhibition by esaprazole was detected on bethanechol-evoked secretion, and the lowest activity was found versus histamine-stimulated secretion. All these responses were strongly inhibited by the antimuscarinic drug pirenzepine used as reference drug. Moreover, both esaprazole and pirenzepine prevented the acid secretory response to a test meal in dogs with a Heidenhain pouch, without significantly affecting plasma gastrin levels. The present results suggest that the depressant action of esaprazole on gastric secretion depends on its peripheral anticholinergic activity, consisting of a partial blockade of acid output and a main reduction of vagally mediated gastrin release. On the basis of these findings, the antiulcer activity of esaprazole might be in part ascribed to its inhibitory effects on gastric secretion.

Animals↗

PubMed1993

Very small-diameter polyurethane vascular prostheses with rapid endothelialization for coronary artery bypass grafting.

Two types of spongy polyurethane-polydimethylsiloxane blend (Cardiothane 51, Kontron Instruments, Inc., Everett, Mass.) vascular grafts with an internal diameter of 1.5 mm were fabricated by a spray, phase-inversion technique. Low-porosity grafts with hydraulic permeability of 2.7 +/- 0.4 ml/min per square centimeter and medium-porosity grafts with hydraulic permeability of 39 +/- 8 ml/min per square centimeter displayed good handling properties and suturability. Twelve straight low-porosity grafts, 17 straight medium-porosity grafts (1.5 to 2.0 cm in length), and one loop medium-porosity graft (10 cm in length) were implanted by the same surgeon end to end in the infrarenal aorta of 30 male Sprague-Dawley rats. Three months after implantation, patency was 8% for low-porosity grafts (1/12) and 76% for straight medium-porosity grafts (13/17). The loop medium-porosity graft was also patent. The sole patent low-porosity graft showed neointimal hyperplasia and incomplete endothelialization. All but one of the patent straight medium-porosity grafts showed a glistening and transparent neointima with complete endothelialization and no anastomotic hyperplasia. The loop medium-porosity graft displayed endothelialization from each anastomosis and in many islands in the middle portion of the graft, totalling 47% of the luminal surface by morphometric analysis. Thick mural thrombus, anastomotic hyperplasia, or aneurysm formation were not observed in any patent medium-porosity graft. These data indicate that in the rat aortic replacement model it is possible to achieve patency and a high degree of endothelialization in very small-diameter prostheses of appropriate porosity.

Animals↗

PubMed1992

Acute intragastric application of capsaicin inhibits 2-deoxy-D-glucose--but not histamine-induced gastric acid secretion in the dog.

In this study the influence of acute exposure of gastric mucosa to the sensory neurotoxin capsaicin on basal gastric acid secretion and on secretion induced by 2-deoxy-D-glucose or histamine in conscious dogs with gastric fistulae has been investigated. Under basal conditions intragastric capsaicin (160 microM, 50 ml of volume) did not induce any significant change in acid secretion and in plasma levels of gastrin. Total acid output induced by 2-deoxy-D-glucose (75 mg/kg i.v.) was significantly decreased by intragastric application of capsaicin, while plasma gastrin concentrations were unaffected. A direct stimulant of the parietal cells, such as histamine (64 micrograms/kg s.c.) increased gastric acid secretion which was not sensitive to capsaicin pretreatment. These findings indicate the involvement of capsaicin-sensitive fibers in the control of vagally-induced gastric acid secretion in the dog.

Animals↗

PubMed1992

Central and peripheral motor effects of galanin on the duodenojejunum and colon in fed rats.

The effects of intraperitoneal, intrathecal and intracerebroventricular injections of the peptide galanin (GAL) on duodenojejunal and colonic motility were studied in conscious fed rats. At 0.3-3.0 nmol/rat, intraperitoneal GAL restored the 'fasted pattern' of duodenojejunal activity, i.e. the migrating myo-electric complex (MMC) was restored for a short period of time, and the MMC frequency was not significantly different from that observed before feeding. In addition, the activity of the proximal but not of the distal colon was significantly increased by GAL administration. The intracerebroventricular administration of GAL (0.03-0.3 nmol/rat) induced an MMC fasted pattern on the duodenojejunum after a latency period of about 1 h. In these experiments proximal colonic motor activity was significantly increased for 120-180 min. GAL given intrathecally (0.03-0.3 nmol/rat) induced a long-lasting fasted pattern of the intestinal activity within 10-20 min which was not dose dependent in duration, while the motility index of the proximal colon was significantly increased. Pretreatment with naloxone prevented the specific effects of GAL, given intracerebroventricularly or intrathecally, on the duodenojejunum and colon and the colonic response, but not the restoration of the MMC pattern on the duodenojejunum, induced by GAL given intraperitoneally. Ketoprofen pretreatment was completely ineffective. These observations indicate a plurality of sites of action of GAL on digestive tract motility including local duodenal receptors and suggest the importance of a spinal component in the control of motility by GAL when given intrathecally. Moreover the present results indicate the involvement of opioid receptors in the fasted pattern induced by GAL given intracerebroventricularly or intrathecally and in the colonic effects regardless of the route of administration.

Animals↗

PubMed1992

Neurokinin receptors and mucosal ion transport in porcine jejunum.

Neurokinin (NK) peptides such as substance P (SP) may modulate epithelial ion transport in the small intestine. The present study was undertaken to examine the pharmacological mechanisms by which SP and its endogenous homologs NKA and NKB affect active electrolyte transport in the mucosa of porcine jejunum. Neurokinins and NK agonist analogs increased short circuit current, a measure of active ion transport, across sheets of jejunal mucosa-submucosa with the order of potency: SP greater than [beta-Ala8]NKA4-10 greater than or equal to [Sar9,Met(O2)11]SP greater than NKA = Arg-NKB greater than NKB after their addition to the serosal aspect of tissues (SP EC50 = 11 nM). Epithelial responses to SP or NKA underwent rapid autotachyphylaxis and unidirectional cross-tachyphylaxis after repeated peptide administration. The neuronal conduction blocker tetrodotoxin significantly reduced NK efficacy. SP activity was significantly reduced in tissues pretreated with the muscarinic cholinoceptor blocker atropine or the eicosanoid synthesis inhibitor eicosa-5,8,11,14-tetraynoic acid. NK peptides increased contractility in longitudinally oriented strips of jejunal smooth muscle with an order of potency: [Sar9,Met(O2)11]SP greater than SP greater than Arg-NKB = [beta-Ala8]NKA4-10 greater than or equal to NKB = NKA (SP EC50 = 11 nM). SP-induced contractions were reduced by 70 to 80% in tissues pretreated with atropine or the neuronal Ca++ channel blocker, omega-conotoxin. [125I]Bolton-Hunter-substance P (BHSP) bound specifically to a single population of sites in slide-mounted sections of mucosa-submucosa and smooth muscle with Kd = 0.3 and 0.1 nM and Bmax = 18 and 31 fmol/mg protein, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗