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Biomedical subjects

F Capasso

Publications and source records attributed to F Capasso.

At least 19 recordsLinked to original sources
PubMed2001

Quantum mechanical actuation of microelectromechanical systems by the Casimir force.

The Casimir force is the attraction between uncharged metallic surfaces as a result of quantum mechanical vacuum fluctuations of the electromagnetic field. We demonstrate the Casimir effect in microelectromechanical systems using a micromachined torsional device. Attraction between a polysilicon plate and a spherical metallic surface results in a torque that rotates the plate about two thin torsional rods. The dependence of the rotation angle on the separation between the surfaces is in agreement with calculations of the Casimir force. Our results show that quantum electrodynamical effects play a significant role in such microelectromechanical systems when the separation between components is in the nanometer range.

Journal Article↗
PubMed2001

Cannabinoid CB1-mediated inhibition of stress-induced gastric ulcers in rats.

The effect of cannabinoid drugs (i.p.) on cold/restraint stress-induced gastric ulcers was studied in rats. The cannabinoid receptor agonist (WIN 55,212-2, 0.1-1 mg/kg), but not the less active isomer WIN 55,212-3 (1 mg/kg), reduced gastric ulceration. The protective effect of WIN 55,212-2 (1 mg/kg) was counteracted by the cannabinoid CB1 receptor antagonist SR141716A, but not by the cannabinoid CB2 receptor antagonist SR144528. These results indicate that the antiulcer effect of the cannabinoid receptor agonist WIN 55,212-2 is mediated by cannabinoid CB1 receptors.

Animals↗
PubMed2001

Effect of vanilloid drugs on gastrointestinal transit in mice.

1. We have studied the effect of capsaicin, piperine and anandamide, drugs which activate vanilloid receptors and capsazepine, a vanilloid receptor antagonist, on upper gastrointestinal motility in mice. 2. Piperine (0.5 - 20 mg kg(-1) i.p.) and anandamide (0.5 - 20 mg kg(-1) i.p.), dose-dependently delayed gastrointestinal motility, while capsaicin (up to 3 mg kg(-1) i.p.) was without effect. Capsazepine (15 mg kg(-1) i.p.) neither per se affected gastrointestinal motility nor did it counteract the inhibitory effect of both piperine (10 mg kg(-1)) and anandamide (10 mg kg(-1)). 3. A per se non effective dose of SR141716A (0.3 mg kg(-1) i.p.), a cannabinoid CB(1) receptor antagonist, counteracted the inhibitory effect of anandamide (10 mg kg(-1)) but not of piperine (10 mg kg(-1)). By contrast, the inhibitory effect of piperine (10 mg kg(-1)) but not of anandamide (10 mg kg(-1)) was strongly attenuated in capsaicin (75 mg kg(-1) in total, s.c.)-treated mice. 4. Pretreatment of mice with N(G)-nitro-L-arginine methyl ester (25 mg kg(-1) i.p.), yohimbine (1 mg kg(-1), i.p.), naloxone (2 mg kg(-1) i.p.), or hexamethonium (1 mg kg(-1) i.p.) did not modify the inhibitory effect of both piperine (10 mg kg(-1)) and anandamide (10 mg kg(-1)). 5. The present study indicates that the vanilloid ligands anandamide and piperine, but not capsaicin, can reduce upper gastrointestinal motility. The effect of piperine involves capsaicin-sensitive neurones, but not vanilloid receptors, while the effect of anandamide involves cannabinoid CB(1), but not vanilloid receptors.

Alkaloids↗
PubMed2001

Immune tolerance induction in haemophilia A patients with high-responding inhibitors to factor VIII: experience at a single institution.

Inhibitor antibodies to transfused factor VIII pose significant challenges in the management of haemophilia A patients. The main concern is the inefficacy of replacement therapy in patients with high-titre antibodies, who have a shorter life-span and a greater morbidity compared to subjects without inhibitors. The ultimate goal in treating these patients is to eliminate the inhibitor antibody entirely, allowing the recommencement of specific replacement therapy. The results of an immune tolerance regimen based on pharmacokinetic parameters are reported here. In 12 high-responder haemophilia A patients immune tolerance induction (ITI) was attempted with daily administration of factor VIII concentrates of very high purity, either plasma-derived or produced by recombinant-DNA technology. Patients were given 100 IU kg(-1) day(-1) until the inhibitor was shown to be absent by at least two negative assays 1 month apart, with normal recovery of infused factor VIII and normal half-life (> 6 h), as assessed after a 3-day washout period. After the patient was judged to be inhibitor-free, immune tolerance treatment was continued with unmodified factor VIII doses for 2 months. Doses were thereafter gradually reduced and finally, regular prophylaxis by administration of 25 IU kg(-1) three times weekly was instituted. Immune tolerance was achieved in 10 of the 12 patients (including six of seven with long-standing inhibitors) within a median time of 8 months. Outcome of immune tolerance was not influenced by age at start of ITI nor by the interval between inhibitor development and ITI. The success rate and the inhibitor disappearance time of our immune tolerance regimen, utilizing high-purity factor VIII, agrees with those reported by other investigators.

Antibodies↗
PubMed2000

Self-mode-locking of quantum cascade lasers with giant ultrafast optical nonlinearities.

We report on the generation of picosecond self-mode-locked pulses from midinfrared quantum cascade lasers, at wavelengths within the important molecular fingerprint region. These devices are based on intersubband electron transitions in semiconductor nanostructures, which are characterized by some of the largest optical nonlinearities observed in nature and by picosecond relaxation lifetimes. Our results are interpreted with a model in which one of these nonlinearities, the intensity-dependent refractive index of the lasing transition, creates a nonlinear waveguide where the optical losses decrease with increasing intensity. This favors the generation of ultrashort pulses, because of their larger instantaneous intensity relative to continuous-wave emission.

Journal Article↗
PubMed2000

Modulation of peristalsis by cannabinoid CB(1) ligands in the isolated guinea-pig ileum.

The effect of cannabinoid drugs on peristalsis in the guinea-pig ileum was studied. Peristalsis was induced by delivering fluid into the oral end of an isolated intestinal segment. Longitudinal muscle reflex contraction, threshold pressure and threshold volume to trigger peristalsis, compliance of the intestinal wall during the preparatory phase (a reflection of the resistance of the wall to distension) and maximal ejection pressure during the emptying phase of peristalsis were measured. The cannabinoid agonists WIN 55,212-2 (0.3 - 300 nM) and CP55,940 (0.3 - 300 nM) significantly decreased longitudinal muscle reflex contraction, compliance and maximal ejection pressure, while increased threshold pressure and volume to elicit peristalsis. These effects were not modified by the opioid antagonist naloxone (1 microM) and by the alpha-adrenoceptor antagonist phentolamine (1 microM). The inhibitory effect of both WIN 55,212-2 and CP55,940 on intestinal peristalsis was antagonized by the cannabinoid CB(1) receptor antagonist SR141716A (0.1 microM), but not by the cannabinoid CB(2) receptor antagonist SR144528 (0.1 microM). In absence of other drugs, the CB(1) receptor antagonists SR141716A (0.01 - 1 microM) and AM281 (0.01 - 1 microM) slightly (approximatively 20%) but significantly increased maximal ejection pressure during the empty phase of peristalsis without modifying longitudinal muscle reflex contraction, threshold pressure, threshold volume to trigger peristalsis and compliance. It is concluded that activation of CB(1) receptors reduces peristalsis efficiency in the isolated guinea-pig, and that the emptying phase of peristalsis could be tonically inhibited by the endogenous cannabinoid system.

Animals↗
PubMed2000

Central and peripheral cannabinoid modulation of gastrointestinal transit in physiological states or during the diarrhoea induced by croton oil.

We have evaluated the effect of cannabinoid drugs, administered intraperitoneally (i.p.) or intracerebroventricularly (i.c.v.) on upper gastrointestinal transit in control and in croton oil-treated mice. The cannabinoid agonists, WIN 55,212-2 (2-239 nmol mouse(-1)) and cannabinol (24-4027 nmol mouse(-1)), decreased while the CB(1) antagonist SR141716A (2-539 nmol mouse(-1)) increased transit in control mice. WIN 55,212-2, cannabinol and SR141716A had lower ED(50) values when administered i.c.v., than when administered i.p. The CB(2) antagonist SR144528 (52 nmol mouse(-1), i.p.) was without effect. During croton oil (0.01 ml mouse(-1), p.o.)-induced diarrhoea, the ED(50) values of i.p. -injected WIN 55,212-2 and cannabinol (but not SR141716A) were significantly decreased (compared to control mice). However, the ED(50) values of WIN 55,212-2 were similar after i.p. or i.c.v. administration. The inhibitory effects of WIN 55,212-2 and cannabinol were counteracted by SR141716A (16 nmol mouse(-1), i.p.) but not by SR144528 (52 nmol mouse(-1), i.p.) both in control and croton-oil treated mice. Ganglionic blockade with hexamethonium (69 nmol mouse(-1), i.p.) did not modify the inhibitory effect of i.p. -injected cannabinoid agonists either in control or in croton-oil treated mice. The lower ED(50) values of cannabinoid drugs after i.c.v. administration suggest a central (CB(1)) site of action. However, a peripheral site of action is suggested by the lack of effect of hexamethonium. In addition, croton oil-induced diarrhoea enhances the effect of cannabinoid agonists by a peripheral mechanism.

Animals↗
PubMed1999

The role of cannabinoid receptors in intestinal motility, defaecation and diarrhoea in rats.

We have studied the effects of the cannabinoid receptor agonists (R)-(+)[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2, 3-de]-1,4-benzoxazin-6-yl]-1-naphthalenylmethanone (WIN 55,212-2, 0. 3-5 mg/kg, i.p.) and (-)-cis-3-[2-hydroxy-4-(1, 1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol) (CP 55,940, 0.03-1 mg/kg, i.p.), the cannabinoid CB(1) receptor antagonist (N-piperidin-1-yl)-5-(4-chlorophenyl)-1-2, 4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (SR141716A, 0. 3-5 mg/kg, i.p.) and the cannabinoid CB(2) receptor antagonist N-[-(1S)-endo-1,3,3-trimethyl bicyclo [2.2.1] heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazo le- 3-carboxamide (SR144528, 1 mg/kg, i.p.) on intestinal motility, defaecation and castor-oil (1 ml/100 g rat, orally)-induced diarrhoea in the rat. SR141716A, but not SR144528, increased defaecation and upper gastrointestinal transit, while WIN 55,212-2 and CP 55,940 decreased upper gastrointestinal transit but not defaecation. WIN 55,212-3 (5 mg/kg), the less active enantiomer of WIN 55,212-2, was without effect. A per se non-effective dose of SR141716A (0.3 mg/kg), but not of SR144528 (1 mg/kg) or the opioid receptor antagonist, naloxone (2 mg/kg i.p.), counteracted the inhibitory effect of both WIN 55,212-2 (1 mg/kg) and CP 55,940 (0.1 mg/kg) on gastrointestinal motility. WIN 55,212-2 did not modify castor-oil-induced diarrhoea, while CP 55,940 produced a transient delay in castor-oil-induced diarrhoea at the highest dose tested (1 mg/kg), an effect counteracted by SR141715A (5 mg/kg). These results suggest that (i) intestinal motility and defaecation could be tonically inhibited by the endogenous cannabinoid system, (ii) exogenous activation of cannabinoid CB(1) receptors produces a reduction in intestinal motility in the upper gastrointestinal tract but not in defaecation, (iii) endogenous or exogenous activation of cannabinoid CB(2) receptors does not affect defaecation or intestinal motility and (iv) the cannabinoid receptor agonist, CP 55, 940, possesses a weak and transient antidiarrhoeal effect while the cannabinoid receptor agonist, WIN 55,212-2, does not possess antidiarrhoeal activity.

Analgesics↗
PubMed1999

Bidirectional Semiconductor Laser.

A semiconductor laser capable of operating under both positive and negative bias voltage is reported. Its active region behaves functionally as two different laser materials, emitting different wavelengths, depending on the design, when biased with opposite polarities. This concept was used for the generation of two wavelengths (6.3 and 6.5 micrometers) in the midinfrared region of the spectrum from a single quantum cascade laser structure. The two wavelengths are excited independently of each other and separated in time. This may have considerable impact on various semiconductor laser applications including trace gas analysis in remote sensing applications with differential absorption spectroscopy.

Journal Article↗
PubMed1999

Contractile effect of (+)-glaucine in the isolated guinea-pig ileum.

The intestinal effects of (+)-glaucine [(S)-1,2,9,10-tetramethoxyaporphine] were studied using the guinea-pig ileum. (+)-Glaucine (10-300 microM) induced ileal contractions. The contraction was not affected by tetrodotoxin, atropine, hexamethonium, propranolol, naloxone, methysergide, N(G)-nitro-L-arginine methyl ester, SR141716A (a cannabinoid CB1 receptor antagonist) or SR140333 (a tackykinin NK1 receptor antagonist) plus SR48968 (a tackykinin NK2 antagonist). (+)-Glaucine-induced contraction was reduced by indomethacin, nordihydroguaiaretic acid or bisindolylmaleimide I and abolished by verapamil and nifedipine. These results suggest that (+)-glaucine-induced contraction involves activation of voltage-dependent Ca2+ channels and protein kinase C and could be mediated by the release of arachidonic acid metabolites.

Animals↗
PubMed1999

The role of nitric oxide in aloe-induced diarrhoea in the rat.

The role of nitric oxide (NO) on aloe-induced diarrhoea was studied in the rat. Nine hours after oral administration, aloe produced diarrhoea at doses of 5 g kg(-1)(20% rats with diarrhoea) and 20 g kg(-1) (100% of rats with diarrhoea). Lower doses of aloe (0.1 and 1 g kg(-1) did not produce a diarrhoeal response. Pre-treatment (i.p.) of rats with the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME 2.5-25 mg kg(-1) reduced the diarrhoea induced by aloe (20 g kg(-1) 9 h after its oral administration. L-NAME (25 mg kg(-1)) also reduced the increase in faecal water excretion produced by aloe (20 g kg(-1). L-arginine (1500 mg kg(-1), i.p.), administered to rats pre-treated with L-NAME (25 mg kg(-1), drastically reduced the effect of L-NAME on diarrhoea and increase in faecal water excretion induced by aloe (20 g kg(-1). Given alone, L-arginine did not modify aloe-induced diarrhoea. Basal Ca2+ -dependent NO synthase activity in the rat colon was dose-dependently inhibited by aloe (0.1-20 g kg(-1)) and by aloin (0.1-1 g kg(-1)), the active ingredient of aloe. These results suggest that endogenous NO modulates the diarrhoeal effect of aloe.

Aloe↗
PubMed1999

Defaecation, intestinal fluid accumulation and motility in rodents: implications of cannabinoid CB1 receptors.

We have studied the effect of SR141716A (0.1-5 mg/kg, i.p.), a cannabinoid CB, receptor antagonist, and WIN (0.1-5 mg/kg, i.p.), a cannabinoid receptor agonist, on acute defaecation and gastrointestinal transit in mice and on intraluminal fluid accumulation in the rat small intestine. SR141716A increased while WIN 55,212-2 decreased defaecation, gastrointestinal transit and fluid accumulation. A per se non-effective dose of SR141716A (0.3 mg/kg) counteracted the inhibitory effect of WIN 55,212-2 (1 mg/kg) on gastrointestinal functions studied. The effect of SR 141716 on both intestinal fluid accumulation in rats and gastrointestinal transit in mice was inhibited by atropine (1 mg/kg, i.p.), but not by hexamethonium (1 mg/kg, s.c.), SR140333 (20 microg/kg, i.p.) or SR48968 (20 microg/kg, i.p.), antagonists of NK1 and NK2 receptors, respectively. These results suggest that intestinal fluid accumulation and motility are inhibited by endogenous cannabinoid(s) acting at the cannabinoid CB1 receptors. This effect may be mediated by mechanisms involving muscarinic cholinoceptors.

Animals↗
PubMed1999

Inhibitory effect of cannabinoid agonists on gastric emptying in the rat.

We have studied the effect of WIN 55,212-2 (a psychoactive cannabinoid agonist), cannabinol (a nonpsychoactive cannabinoid agonist), SR141716A, a cannabinoid CB1 antagonist, and SR144528, a cannabinoid CB2 antagonist, on gastric emptying in the rat. WIN 55,212-2 (0.1-5 mg/kg, i.p.) and cannabinol (0.1-25 mg/kg, i.p.) dose-dependently delayed gastric emptying while SR141716A (1 mg/kg and 5 mg/kg) and SR144528 (1 mg/kg) were without effect. SR141716A (1 mg/kg), but not SR144528 (1 mg/kg), counteracted the inhibitory effect of the two cannabinoid agonists. These results suggest that cannabinoid agonists delay gastric emptying through activation of cannabinoid CB1 receptors, while the endogenous cannabinoid system does not seem to modulate gastric motility.

Analgesics↗
PubMed1999

Flavonoids: old and new aspects of a class of natural therapeutic drugs.

Flavonoids are natural products widely distributed in the vegetable kingdom and currently consumed in large amounts in the daily diet. Flavonoids are capable of modulating the activity of enzymes and affect the behaviour of many cell systems, suggesting that the compounds may possess significant antihepatotoxic, antiallergic, anti-inflammatory, antiosteoporotic and even antitumor activities. This review summarizes available data on these beneficial effects of flavonoids.

Animals↗
PubMed1999

Ascending neural pathways in the isolated guinea-pig ileum: effect of muscarinic M1, M2 and M3 cholinergic antagonists.

The effect of muscarinic cholinoceptor antagonists was investigated on the ascending neural pathways activated by electrical stimulation in the guinea-pig ileum. For comparison, prejunctional and postjunctional effects of muscarinic cholinoceptor antagonists were also studied on circular smooth muscle. A two-compartment (oral and anal compartments) bath was used to study the ascending neural pathways. These were activated by electrical field stimulation in the anal compartment and the resulting contraction of the intestinal circular muscle in the oral compartment was recorded isotonically. Pirenzepine (10-300 nM), a muscarinic M1 cholinoceptor antagonist, reduced the ascending neural contractions in a concentration-dependent fashion when applied either to the oral or anal compartments (11-52% and 13-55% inhibition, respectively, P < 0.05). Pirenzepine inhibited (31+/-7%, P < 0.05) the acetylcholine (100 nM)-induced contractions at a higher non-selective concentration (300 nM), while its effect on the electrically-induced contractions was biphasic (10 and 30nM: 8-15% increase, P<0.05; 100 and 300 nM: 16-28% inhibition, P<0.05). The muscarinic M2 cholinoceptor antagonist methoctramine (3-100 nM) did not modify the contractions produced by 100 nM acetylcholine, electrically-induced contractions and the ascending neural contractions (when applied to either compartment). Parafluorohexahydrosiladifenidol (3-100 nM), a muscarinic M3 cholinoceptor antagonist, inhibited the contractions produced by 100 nM acetylcholine (19-81% and 15-69%), electrically-induced contractions (11-71% and 12-72%) and the ascending neural contractions (13-76% and 866%) when applied to the oral compartment, but it was without effect when applied to the anal compartment. These studies suggest that in the enteric ascending neural pathway, muscarinic M1 receptors are involved in neuroneuronal transmission, muscle contraction is mediated by muscarinic M3 cholinergic receptors, whereas muscarinic M2 receptors do not seem to participate.

Acetylcholine↗
PubMed1999

Intracoronary shunt prevents left ventricular function impairment during beating heart coronary revascularization.

OBJECTIVE: Beating heart coronary revascularization is becoming increasingly popular world-wide. Temporary occlusion of the coronary artery is often required in order to perform the anastomosis. An alternative method to maintain perfusion is to use an intracoronary shunt. In this study, we monitored global left ventricular function and regional wall motion in the presence or absence of a shunt using transesophageal echocardiography (TEE). METHOD: Left ventricular wall motion score index (WMSI), wall motion score (WMS) in the left anterior descending (LAD) coronary artery territory, and ejection fraction (EF%) were measured by multiplane TEE during construction of the left internal mammary artery (LIMA)-LAD coronary artery anastomosis in 40 patients undergoing revascularization with or without the use of a shunt. WMSI was assessed preoperatively, 1, 3 and 6 min during the construction of the anastomosis and after 5 min of reperfusion. WMS was assessed at 6 min during anastomosis and after 5 min of reperfusion. EF% was calculated preoperatively, 5 min into the construction of the anastomosis, and 5 min after reperfusion. RESULTS: During construction of the anastomosis, when the shunt was used, there were no changes in WMSI, WMS in the LAD territory or EF%. A significant decline in these parameters was seen in the group in which the shunt was not used, although on reperfusion all the values returned to baseline control. CONCLUSION: (i) occlusion of the LAD to perform the anastomosis results in temporary impairment in left ventricular function with complete recovery on reperfusion; (ii) the use of an intracoronary shunt presumably by maintaining myocardial perfusion prevents deterioration in ventricular function; (iii) from this data it seems therefore advisable to use an intracoronary shunt in patients with unstable angina, poor left ventricular function, or in cases in which a longer time to perform the anastomosis is anticipated.

Aged↗