HCV infection by cell-to-cell transmission: choice or necessity?

In vitro models of HCV infection have allowed for the clarifying of molecules and mechanisms involved in the main steps of virus cell-entry. HCV entry and neutralization appear to be closely related. Neutralizing antibodies inhibit the E2-CD81 binding, therefore CD81 is considered to be a major target of immune response. The tight-junction proteins are also implicated in E2-binding to CD81 and successive steps of virus entry, in cooperation with several co-receptors, whose involvement has still to be elucidated. Increasing evidence has emphasized the importance of cell-to-cell HCV-transmission in chronic infection. This route for infection could favour virus-escape from host-neutralization though its CD81-dependency is still debated. The main reasons which have delayed our understanding of HCV-infection are here critically reviewed, as are the challenges faced by investigators in the field. A deeper insight into the different pathways involved could help to elucidate some crucial features of HCV infection mechanisms and disclose important implications in its pathogenesis, which could help in suggesting new targets for successful immune-prophylactic/therapeutic strategies.

A hybrid tool for reaching and grasping rehabilitation: the ArmeoFES.

Many research groups are currently working with robotic devices for hand grasp rehabilitation and restoration. A common problem in this area is the fact that existing and commercially available robotic exoskeletons are able to provide gravity compensation of the shoulder and elbow but do not provide any support for the grasping and releasing movements of the hand. The lack of a flexible support technology for the hand reduces the possible ways in which clinicians can deal with the issue of a personalized, effective rehabilitation. This paper presents new software that allows FES assisted grasping to integrate with the ArmeoSpring (Hocoma AG). The system uses a Man-In-The-Loop control approach, whereby surface EMG signals from proximal muscles are used to trigger and modulate multichannel FES applied to distal muscles, thus allowing patient induced and strength adapted movement control of the hand. Combining volitionally controlled FES with arm-weight-compensation allows early adoption of FES assisted therapy for patients, augmenting their functionalities and extending training capabilities with the ArmeoSpring.

Priming-like effect and successful desensitization after anaphylactic shock by latex sublingual immunotherapy.

The present report deals with some unusual events observed restarting allergy vaccine in a case of anaphylactic shock which occurred giving the maximum scheduled dose (25 drops) of rush sublingual immunotherapy (SLIT) to latex. Restarting SLIT by usual (not rush) scheme we observed long-lasting fall of reactivity threshold. The maximum tolerable dose was reduced to 2 drops, a dose fivefold smaller than the one well tolerated during previous rush phase (10 drops). We have excluded a possible nocebo effect and proved that the reduced tolerance was real by double blind placebo-controlled challenge test. We have considered this effect in some ways similar to priming effect. SLIT was continued with two drops every day. After about twenty months we could demostrate a significant reduction of skin reactivity by end-point technique and an improved response to the controlled exposition to latex by use-tests. In the same time the tolerance to vaccine was improved to three drops. The better safety profile allowed us to restart and continue with SLIT also in the reported case of anaphlicatic shock by latex vaccine and, after about two years, to induce valuable hyposensitization. Latex SLIT is confirmed as a safe and effective method.

[The electrocardiology of atrial fibrillation]. / Elettrocardiologia della fibrillazione atriale.

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia and it is associated mainly with a significant mortality and morbidity. The purpose of this report is to focus on the major electro-cardiological aspects of AF and to provide some elements useful in the understanding of its pathophysiology. Experimental and clinical studies have shown that AF is maintained by multiple reentrant wavelets within the atrial muscle. It has been estimated that a critical number of wavelets (from 3 to 6) is necessary for perpetuation of AF. The short duration of the atrial effective refractory period (ERP) usually favors the onset of AF. Two different kinds of reentry have been observed during AF: random reentry and leading circle reentry. The presence of an adequate substrate is critical for the beginning of AF. Although this event is possible even in a normal atrium, atrial dilation and/or structural heterogeneity enhance the atrial propensity to develop AF. Even uniform or non-uniform anisotropy is now believed to play an important role in the genesis of AF. Finally, ionic channel disorders, some of which are genetically transmitted, may represent a possible substrate of AF. An important modulating role of the autonomic nervous system in the genesis of AF is universally accepted. In particular, many observations support the hypothesis that patients without heart disease tend to have vagally-mediated AF, whereas patients with structural heart disease tend to have adrenergic-mediated AF. In the presence of an opportunely modulated substrate, a third prerequisite for the triggering of a multiple atrial reentry is the presence of an adequate "trigger" factor. This is represented, in most cases, by ectopic atrial beats, commonly originating in the pulmonary veins. AF may cause atrial changes, either in an electrophysiological behavior and anatomy or both, that may favor its irreversibility and/or its frequent recurrence. Some of these changes are: atrial ERP disease, paradoxical shortening of ERP at a lower rate (inversed rate adaptation), accumulation of glycogen within atrial cells, apoptosis, and cellular dedifferentiation. The ventricular rate during AF has a pivotal role in its pathophysiology. The ERP of the atrioventricular node, the concealed conduction through the atrioventricular node, the autonomic neural balance and the drug's action are the most important factors that regulate ventricular rate during AF. In the presence of an atrioventricular accessory pathway, with fast anterograde conduction, AF is a very dangerous arrhythmia. During AF, aberrant conduction may often be seen, especially after long cycles (Ashman phenomenon). In patients with dilated cardiomyopathy and AF, arrhythmia is not always a secondary phenomenon. In fact, there is current evidence that AF may be the cause of cardiomyopathy.

Stereoselective pharmacokinetics of moguisteine metabolites in healthy subjects.

We studied the pharmacokinetics of moguisteine, a racemic non-narcotic peripheral antitussive drug, in 12 healthy male subjects after a single oral administration of 200 mg. The unchanged drug was absent in plasma and urine of all subjects. Moguisteine was immediately and completely hydrolyzed to its main active metabolite, the free carboxylic acid M1. Therefore, we evaluated the kinetic profiles of M1, of its enantiomers R(+)-M1 and S(-)-M1, and of M1 sulfoxide optical isomers M2/I and M2/II by conventional and stereospecific HPLC. Maximum plasma concentrations for M1 (2.83 mg/l), M2/I (0.26 mg/l) and M2/II (0.40 mg/l), were respectively reached at 1.3, 1.6 and 1.5 h after moguisteine administration. Plasma concentrations declined after the peak with mean apparent terminal half-lives of 0.65 h (M1), 0.88 h (M2/I) and 0.84 h (M2/II). Most of the administered dose was recovered in urine within 6 h from moguisteine treatment. The systemic and renal clearance values indicated high renal extraction ratio for all moguisteine metabolites, and particularly for M1 sulfoxide optical isomers. Plasma concentration-time profiles and urinary excretion patterns for M1 enantiomers R(+)-M1 and S(-)-M1 were quite similar. Thus, for later moguisteine pharmacokinetic evaluations the investigation of the plasma concentration-time curve and the urinary excretion of the sole racemic M1 through non-stereospecific analytical methods may suffice in most cases.

Inhibitory effects of SR 58611A on canine colonic motility: evidence for a role of beta 3-adrenoceptors.

1. In order to clarify whether atypical or beta 3-adrenoceptors can modulate canine colonic motility in vivo, we studied the effects of SR 58611A (a selective agonist for atypical beta-adrenoceptors) alone and after pretreatment with beta-adrenoceptor antagonists on colonic motility in the conscious dog. The gastrocolonic response (postprandial increase in motility) was monitored by means of electrodes and strain-gauge force transducers chronically implanted along the distal colon. In some experiments, heart rate was also measured. The possible role of beta 3-adrenoceptors in mediating the effects of SR 58611A was also tested in vitro in circular muscle strips taken from the canine distal colon. 2. Intravenous infusion of SR 58611A, ritodrine or isoprenaline at doses inducing the same degree of tachycardia inhibited the gastrocolonic response to a different extent, with SR 58611A and ritodrine being more effective than isoprenaline. 3. In a dose-response study, SR 58611A was more potent in inhibiting colonic motility than in inducing tachycardia: the ED35 values for inhibition of colonic motility and induction of tachycardia were 23 and 156 micrograms kg-1, i.v., respectively. 4. The inhibitory effect of SR 58611A 100 micrograms kg-1, i.v., on the gastrocolonic response was reversed by alprenolol (non-selective beta-adrenoceptor antagonist), but resistant to CGP 20712A (beta 1-adrenoceptor antagonist) or ICI 118551 (beta 2-adrenoceptor antagonist). 5. In vitro, SR 58611A concentration-dependently relaxed circular muscle strips, an effect that was competitively antagonized by alprenolol with a pA2 value of 7.1, but resistant to CGP 20712A (100 nM), ICI 118551 (100 nM) or tetrodotoxin (1 microM). 6. The present study provides strong functional evidence for a role of atypical or beta 3-adrenoceptors in the modulation of canine colonic motility both in vivo and in vitro by an inhibitory effect most likely at the smooth muscle level.

Effect of food on the bioavailability of pidotimod in healthy volunteers.

Pidotimod ((R)-3-[(S)-(5-oxo-2-pyrrolidinyl) carbonyl]-thiazolidine-4-carboxylic acid, PGT/1A, CAS 121808-62-6) is a dipeptide-like molecule with immunostimulating activity in animals and in men. According to a cross-over randomized study design, 12 healthy volunteers received pidotimod both as 800 mg sachets and 800 mg ampoules after fasting and after a standard meal. The intake of a standard meal before pidotimod administration, either as sachet or as ampoule, reduced the bioavailability of the drug, probably due to an interference at the absorption level. After eating, the time of maximum plasma level was significantly longer than that observed after fasting, while AUC values and the maximum concentration were reduced by 50%. On the contrary, the pharmacokinetics after absorption phase were not influenced by food: as a matter of fact, half-life and MRT did not differ significantly when the drug was taken after fasting or after a standard meal. Finally, the two formulations used in this study resulted bioequivalent.

Prolonged monitoring of colonic spike activity by a computerized system: application to the rabbit colon.

In the present paper, we describe and validate a computerized system for the quantitative analysis of colonic spike activity in the conscious rabbit. This system allowed data acquisition at 160 Hz on 8 channels simultaneously during the recording session. Data analysis at the end of the recording session took approximately 10 min for each hour of recording. The spike recognition procedure was carried out on the basis of a discriminant function which discarded artifactual fast events. Data could be presented as histograms or be transferred into an ASCII file for later statistical analysis. Reliability tests showed that the misrecognition rate was only 3.88%. In conclusion, this computerized system is a reliable, timesaving tool for the quantitative analysis of colonic spike activity.

Differential effects of antimuscarinic agents on intestinal motility in the conscious dog.

In this study we investigated the effects of antimuscarinics with different selectivity on the intestinal migrating myoelectric complex (MMC) in five fasting, conscious dogs, chronically fitted with electrodes along the small bowel. Furthermore, we evaluated the chronotropic and mydriatic effects to assess the in vivo selectivity of the agents tested. Dose-response studies were performed with the following drugs administered i.v.: atropine, telenzepine (M1 antagonist), AF-DX 116 [11,2-(diethylamino)methyl-1-piperidinyl-acetyl-5,11-dihydro-6H-pyrido-2 ,3b- 1,4-benzodiazepine-6-one (M2 antagonist)] and 4-diphenylacetoxy-N- methylpiperidine methiodide (4-DAMP) (M3 antagonist). All the antimuscarinics tested dose-dependently increased the duration of the MMC period and inhibited spike activity, except low-dose telenzepine (3-10 nmol/kg), which shortened the MMC period and stimulated spike activity. High-dose telenzepine (> 100 nmol/kg) mimicked the inhibitory effect of atropine on the intestine. ED50 values for delay of MMC onset were 87,232, > 10,000 and 129 nmol/kg for atropine, telenzepine, AF-DX 116 and 4-DAMP, respectively. At doses lengthening the MMC period, atropine and 4-DAMP also induced tachycardia and mydriasis. At doses shortening the MMC period, telenzepine had no effect on pupil diameter or heart rate, except at the dose of 10 nmol/kg, which reduced heart rate. Finally, AF-DX 116, at doses inducing marked tachycardia, had a minor intestinal effect and no mydriatic effect. The present data are consistent with the hypothesis that both M1 and M3 receptors are involved in the regulation of the MMC: M1 receptors are probably located on an inhibitory pathway, whereas M3 receptors mediate excitatory stimuli.(ABSTRACT TRUNCATED AT 250 WORDS)

Motility of rabbit proximal colon. Relevance of cholinergic pathways and role of different muscarinic receptor subtypes.

To better define the physiologic relevance of the cholinergic muscarinic input to the rabbit colon and the role of different muscarinic receptor subtypes, we studied the effects of atropine, telenzepine (MI antagonist) and DF594 (M3 antagonist) on colonic motility in eight conscious rabbits fitted with bipolar electrodes and strain gauges along the proximal colon. In some experiments, the chronotropic and mydriatic effect of the pharmacological agents were also assessed. Two main patterns of spike activity were identified: short spike bursts (SSBs), which were usually stationary, and long spike bursts (LSBs), which were usually propagated. Both myoelectrical patterns were dose-dependently inhibited by atropine (0.06-4 mumol/kg). Atropine, at the doses of 2-4 mumol/kg, abolished both myoelectrical and mechanical activity. Telenzepine (0.008-0.125 mumol/kg) dose-dependently inhibited migrating LSBs without significant effect on SSBs. Higher doses (0.25-0.5 mumol/kg) inhibited both LSBs and SSBs. DF594 (0.06-2 mumol/kg) dose-dependently inhibited both migrating LSBs and SSBs. The three antimuscarinic agents, at doses that inhibited colonic spike activity by approximately 80% (equiactive doses), behaved as follows on heart rate and pupil diameter: atropine induced tachycardia and mydriasis, telenzepine had no effect, and DF594 induced slight mydriasis with no effect on heart rate. We conclude that spontaneous motility in the rabbit proximal colon depends on a muscarinic excitatory input. M3 receptors are involved in the control of both LSBs and SSBs, while M1 receptors play an important role in the regulation of LSBs. The development of selective antimuscarinic drugs, acting on a given motility pattern and with minimal side effects, may offer new perspectives in the treatment of functional bowel motor disorders.

Effect of calcium channel blockers on postprandial gastrointestinal motility in the dog.

We have compared the ability of nifedipine and lacidipine, a new 1,4-dihydropyridine, to interfere with postprandial gastrointestinal motility. Five conscious dogs, fitted with 8 bipolar electrodes along the gastrointestinal tract, were studied. Gastrointestinal spike activity was evaluated by means of a computer system. Lacidipine (8 micrograms kg-1) was administered as an i.v. bolus immediately followed by a 10 micrograms kg-1 h-1 i.v. infusion for 3 h, starting 30 min before a standard meal. This dose of lacidipine decreased systolic blood pressure by approximately 20%. Nifedipine was used at equihypotensive doses (30 micrograms kg-1 i.v. bolus followed by 300 micrograms kg-1 h-1 i.v. infusion). Lacidipine had no effect on either gastric or intestinal postprandial spike activity. Nifedipine significantly delayed the appearance of the fed pattern and reduced the number of spikes in the small bowel, while it had no effect on gastric spike activity. We conclude that equihypotensive doses of lacidipine and nifedipine differ in their effects on the gastrointestinal tract, lacidipine having a better cardiovascular selectivity profile than nifedipine, and that the sensitivity to nifedipine varies in different parts of the gut.

Physiopharmacology of the peristaltic reflex: an update.

The peristaltic reflex is one of the simplest models which can be used to study the function of enteric neurons by recording intestinal motor activity. Peristalsis consists of a coordinated, aborally propagating motor activity which requires the functional integrity of receptor pathways, excitatory and inhibitory neural pathways and neuromuscular junctions. Luminal distension elicits polarized responses: an ascending excitatory response (ascending contraction) and a descending inhibitory response (descending relaxation). The present paper reviews the most recent acquisitions on the neural pathways and neurotransmitters involved in the regulation of the peristaltic reflex.

Effect of single doses of rufloxacin on the disposition of theophylline and caffeine after single administration.

Several reports indicate that quinolone antibiotics affect the pharmacokinetics of theophylline and caffeine. This study investigated the effects of one single oral dose of rufloxacin, a new quinolone antibacterial, on the pharmacokinetics of theophylline and caffeine, given as single oral doses. Twelve healthy male volunteers were randomly given one of the following treatments: treatment T: 300 mg theophylline; treatment T + R: 300 mg theophylline followed by 400 mg rufloxacin after 30 min; treatment C: 200 mg caffeine; treatment C + R: 200 mg caffeine followed by 400 mg rufloxacin after 30 min. Blood samples for determination of xanthine plasma levels were taken immediately before and 1, 2, 4, 6, 8, 10, 12, 24 and 48 hours after xanthine administration. Urine were collected before treatment and at 0-6, 6-12, 12-24 and 24-48 h intervals. There were no significant differences in the pharmacokinetic parameters or in urinary excretion after administration of either theophylline or caffeine when combined with rufloxacin. Sleep disturbances were reported by two subjects after both treatment T + R and C + R, and by four subjects after treatment T + R. The results of this study indicate that there is no significant pharmacokinetic interaction between a single oral dose of rufloxacin and single doses of theophylline and caffeine.