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M Marchi

Publications and source records attributed to M Marchi.

At least 37 records · Page 2Linked to original sources
PubMed1999

Evidence for calcium-dependent vesicular transmitter release insensitive to tetanus toxin and botulinum toxin type F.

Whether exocytosis evoked by a given releasing stimulus from different neuronal families or by different stimuli from one neuronal population occurs through identical mechanisms is unknown. We studied the release of [3H]noradrenaline, [3H]acetylcholine and [3H]dopamine induced by different stimuli from superfused rat brain synaptosomes pretreated with tetanus toxin or botulinum toxin F, known to block exocytosis by cleaving VAMP/synaptobrevin. The external Ca2(+)-dependent [3H]transmitter overflows evoked by KCl were similarly inhibited by tetanus toxin or botulinum toxin F; the toxins cleaved similar amounts of synaptosomal synaptobrevin, as determined by western blot analysis, suggesting prevalent involvement of synaptobrevin-II. GABA uptake-mediated release of the three [3H]transmitters was that differentially sensitive to the toxins: only the release of [3H]noradrenaline, which is dependent on external Ca2+, but not of [3H]acetylcholine and [3H]dopamine was blocked. Neither toxin affected the [3H]transmitter overflows evoked by the Ca2(+) ionophore ionomycin. Cadmium blocked the K(+)-evoked release of all [3H]transmitters and the GABA-evoked release of [3H]noradrenaline; the GABA-evoked releases of [3H]acetylcholine and [3H]dopamine and those elicited by ionomycin were insensitive to cadmium. The results suggest that tetanus toxin and botulinum toxin F selectively affect exocytosis linked to activation of voltage-sensitive Ca2(+) channels; the Ca2(+)-dependent, exocytotic-like release induced by stimuli not leading to activation of voltage-sensitive Ca2+ channels seems insensitive to these clostridial toxins.

Animals↗
PubMed1999

Methodological problems and the role of statistics in cluster response studies: a framework.

More and more citizens urge public health authorities to investigate reports of disease excess in their neighbourhood. These environmental concerns are legitimate and it is part of good public health practice to respond to these complaints. However, the methodological and practical problems are severe and a lot of controversy exists about the usefulness of these investigations. To clarify the possibilities and limitations in this situation, this paper proposes a typology of cluster studies. According to this framework, cluster response is distinguished from two other types of cluster studies: Cluster monitoring. screening proactively for clusters to act as an early warning system, and cluster research, scrutinizing clustering to generate and test aetiological hypotheses. To each of these three types of cluster studies corresponds a different public health context; respectively public health action, public health surveillance and public health research. Probably, part of the controversy mentioned stems from not acknowledging sufficiently the corresponding intrinsic differences in rationality and practical constraints. Cluster response is crisis management and not scientific research. In a relatively short time, an informed decision should be taken by a multidisciplinary team of experts using readily available information and knowledge. In accordance with this point of view, cluster reports should be handled stepwise and the role of statistics is to quantify a cluster exploring different points of view as an input to the decision process.

Cluster Analysis↗
PubMed1998

Prematurely detected traumatic carotid-cavernous sinus fistula, by means of unintentional contralateral inferior petrosal sinus catheterization: bilateral jugular bulb oxygen saturation findings.

A traumatic carotid-cavernous sinus fistula (CCSF) was prematurely suspected following the detection of arterial-like hemoglobin oxygen saturation values, sampled from a catheter placed for cerebrovenous monitoring. A high-resolution scan of jugular foramina revealed that the catheter tip had been unintentionally placed in the inferior petrosal sinus, contralateral to the CCSF, instead of in the superior jugular bulb. Jugular bulb hemoglobin oxygen saturation (SjO2), ipsilateral to CCSF, later approached arterial hemoglobin oxygen saturation (SaO2) values.The possibility and consequences of unintentional catheterization of the inferior petrosal sinus, and of extracerebral contamination of blood in the jugular bulb due to blood in the inferior petrosal sinus, are discussed. We also discuss the reliability of SjO2 monitoring in the present CCSF case.

Carotid Sinus↗
PubMed1998

[Deglutition in patients treated with reconstructive laryngectomy].

INTRODUCTION: We stress the importance of dynamic radiologic studies of swallowing in the patients submitted to reconstructive laryngectomy. MATERIAL AND METHODS: January, 1989, to December, 1996, we examined 36 patients submitted to reconstructive laryngectomy, namely cricohyoidoepiglottopexy in 34 cases, cricohyoidopexy in 1 case and Guerrier's cricohyoidoepiglottopexy in 1 case. Dynamic radiologic studies were performed with fluoroscopic videorecording (Sony U-Matic RM 580) from an X-ray unit. The study was performed with the patients standing or sitting, initially acquiring AP and LL fluoroscopic images of the oropharyngeal region at rest and during swallowing. The patients then swallowed 2 boluses of 5 ml liquid (60%) and semiliquid (250%) barium. When aspiration was suspected, we began with a 2-ml bolus. RESULTS: The patients were grouped by symptoms: group A patients had no symptoms, group B patients had dysphagia and group C patients presented aspiration. The functional changes were: reduced pharyngeal contraction, reduced epiglottis deflection, reduced hyoid bone elevation, aspiration, altered upper esophageal sphincter function. The organic alterations were: parapharyngeal diverticulum, pharyngeal stenosis, posterior pharyngeal wall introflexion. Three group A patients had severe posterior pharyngeal wall introflexion, 4 had marked retention and 2 of them presented postswallowing aspiration. Two group B patients had major retention, 1 cricopharyngeal incoordination, 3 posterior pharyngeal wall introflexion, 2 a pseudodiverticulum and 2 a luminal stenosis. Seven group C patients had intraswallowing and 3 postswallowing aspiration. CONCLUSION: The videofluorographic identification of organic and functional complications, sometimes unknown in asymptomatic patients, is useful for therapy and suggests the speech specialist the best compensatory mechanism to improve the patients' swallowing and consequently their quality of life. Moreover, videofluorography of swallowing is a very useful tool in the follow-up, to monitor treatment outcome after rehabilitation.

Deglutition↗
PubMed1997

Haemangioma of the zygoma: case report.

Haemangioma of bone in the zygoma is extremely rare. We report two cases presenting with swelling of the zygomatic region. The literature is reviewed and CT, angiographic and MRI findings are discussed.

Adult↗
PubMed1996

Intrinsic compressibility and volume compression in solvated proteins by molecular dynamics simulation at high pressure.

Constant pressure and temperature molecular dynamics techniques have been employed to investigate the changes in structure and volumes of two globular proteins, superoxide dismutase and lysozyme, under pressure. Compression (the relative changes in the proteins' volumes), computed with the Voronoi technique, is closely related with the so-called protein intrinsic compressibility, estimated by sound velocity measurements. In particular, compression computed with Voronoi volumes predicts, in agreement with experimental estimates, a negative bound water contribution to the apparent protein compression. While the use of van der Waals and molecular volumes underestimates the intrinsic compressibilities of proteins, Voronoi volumes produce results closer to experimental estimates. Remarkably, for two globular proteins of very different secondary structures, we compute identical (within statistical error) protein intrinsic compressions, as predicted by recent experimental studies. Changes in the protein interatomic distances under compression are also investigated. It is found that, on average, short distances compress less than longer ones. This nonuniform contraction underlines the peculiar nature of the structural changes due to pressure in contrast with temperature effects, which instead produce spatially uniform changes in proteins. The structural effects observed in the simulations at high pressure can explain protein compressibility measurements carried out by fluorimetric and hole burning techniques. Finally, the calculation of the proteins static structure factor shows significant shifts in the peaks at short wavenumber as pressure changes. These effects might provide an alternative way to obtain information concerning compressibilities of selected protein regions.

Muramidase↗
PubMed1996

Role of external and internal calcium on heterocarrier-mediated transmitter release.

Release-regulating heterocarriers exist on brain nerve endings. We have investigated in this study the mechanisms involved in the neurotransmitter release evoked by GABA heterocarrier activation. GABA increased the basal release of [3H]acetylcholine and [3H]noradrenaline from rat hippocampal synaptosomes and of [3H]dopamine from striatal synaptosomes. These GABA effects, insensitive to GABA receptor antagonists, were prevented by inhibiting GABA uptake but not by blocking noradrenaline, choline, or dopamine transport. Lack of extracellular Ca2+ or addition of tetrodotoxin selectively abolished the GABA-evoked release of [3H]noradrenaline, leaving unaffected that of [3H]acetylcholine or [3H]dopamine. 1,2-Bis(2-aminophenoxyl)-ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester (BAPTA-AM) or vesamicol attenuated the release of [3H]acetylcholine elicited by GABA. Reserpine, but not BAPTA-AM, prevented the effect of GABA on [3H] dopamine release. Autoreceptor activation inhibited the GABA-evoked release of [3H]noradrenaline but not that of [3H]acetylcholine or [3H]dopamine. It is concluded that (a) the release of [3H]noradrenaline consequent to activation of GABA heterocarriers sited on noradrenergic terminals meets the criteria of a conventional exocytotic process, (b) the extracellular [Ca2+]-independent releases of [3H]acetylcholine and [3H]dopamine appear to occur from vesicles possibly through involvement of intraterminal Ca2+, and (c) autoreceptor activation only affects heterocarrier-mediated vesicular release linked to entry of extracellular Ca2+.

Acetylcholine↗
PubMed1996

Nicotinic autoreceptors mediating enhancement of acetylcholine release become operative in conditions of "impaired" cholinergic presynaptic function.

The existence in the mammalian CNS of release-inhibiting muscarinic autoreceptors is well established. In contrast, few reports have focused on nicotinic autoreceptors mediating enhancement of acetylcholine (ACh) release. Moreover, it is unclear under what conditions the function of one type of autoreceptor prevails over that of the other. Rat cerebrocortex slices, prelabeled with [3H]choline, were stimulated electrically at 3 or 0.1 Hz. The release of [3H]ACh evoked at both frequencies was inhibited by oxotremorine, a muscarinic receptor agonist, and stimulated by atropine, a muscarinic antagonist. Nicotine, ineffective at 3 Hz, enhanced [3H]ACh release at 0.1 Hz; mecamylamine, a nicotinic antagonist, had no effect at 3 Hz but inhibited [3H]ACh release at 0.1 Hz. The cholinesterase inhibitor neostigmine decreased [3H]ACh release at 3 Hz but not at 0.1 Hz; in the presence of atropine, neostigmine potentiated [3H]ACh release, an effect blocked by mecamylamine. In synaptosomes depolarized with 15 mM KCl, ACh inhibited [3H]ACh release; this inhibition was reversed to an enhancement when the external [Ca2+] was lowered. The same occurred when, at 1.2 mM Ca2+, external [K+] was decreased. Oxotremorine still inhibited [3H]ACh release at 0.1 mM Ca2+. When muscarinic receptors were inactivated with atropine, the K+ (15 mM)-evoked release of [3H]ACh (at 0.1 mM Ca2+) was potently enhanced by ACh acting at nicotinic receptors (EC50 approximately 0.6 microM). In conclusion, synaptic ACh concentration does not seem to determine whether muscarinic or nicotinic autoreceptors are activated. Although muscarinic autoreceptors prevail under normal conditions, nicotinic autoreceptors appear to become responsive to endogenous ACh and to exogenous nicotinic agents under conditions mimicking impairment of ACh release. Our data may explain in part the reported efficacy of cholinesterase inhibitors (and nicotinic agonists) in Alzheimer's disease.

Acetylcholine↗
PubMed1995

Effects of an acute increase in plasma triglyceride levels on glucose metabolism in man.

The aim of the study was to evaluate the effects of an acute increase in triglyceride levels induced by Intralipid (Kabivitrum, Stockholm, Sweden) infusion on forearm glucose uptake, glucose oxidative metabolism, and hepatic glucose production independent of circulating free fatty acid (FFA) levels in man. Six normal subjects underwent three different tests in random order. Each test consisted of a control period of 120 minutes followed by a euglycemic, hyperinsulinemic clamp lasting 120 minutes. In test 1, a high-dose intravenous Intralipid infusion was performed to increase triglyceride and FFA levels. In test 2, heparin (30 U/min) plus low-dose Intralipid infusions were performed to maintain triglyceride at normal levels and increase only FFA levels. Test 3 was performed as a control study. During the 120-minute control period, forearm glucose uptake and hepatic glucose production were not affected by increasing only FFA levels (test 2) or FFA and triglyceride levels (test 1) as compared with the control study. On the contrary, glucose oxidation was significantly decreased as compared with the control study during tests 1 and 2, without a further significant decrease during simultaneously increased FFA and triglyceride levels. Concomitantly, lipid oxidation was similar in tests 1 and 2, at values significantly greater than in test 3. During the euglycemic clamp, forearm glucose uptake and glucose oxidation were significantly lower during tests 1 and 2 than test 3. At variance with the control period, the increase of triglyceride levels during test 1 caused a significant 30% to 40% decrease of both parameters as compared with test 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Lateral thigh free flap in head and neck reconstruction.

To understand the role of the lateral thigh flap in head and neck reconstruction, we performed injection studies and anatomic dissections in 2 fresh and 61 preserved cadaver extremities followed by 10 clinical cases involving defects after tumor ablation. The flap, based on the third perforator of the profunda femoris artery, is designed on the posterolateral aspect of the distal thigh. The pedicle courses through the biceps short head, allowing optional transfer of this muscle. Defects of the oral cavity, pharynx, cervical esophagus, and external skin were successfully restored. One flap was unsuccessful because of intraoperative injury to the vascular pedicle. Compared with the radial forearm flap, the lateral thigh flap provides more tissue and the donor scar is more easily hidden, but the vascular pedicle is shorter, of smaller caliber, and more variable. The lateral thigh flap provides thin, pliable, and reliable tissue for a variety of needs in properly selected patients.

Adult↗
PubMed1995

[Time series analysis in environmental epidemiology: short-term effects of air pollution on mortality and morbidity].

This work gives an overview of design and analysis of temporal studies using aggregated data in air pollution epidemiology. In the last years time series are often used to study the short-term association between ambient air pollution levels and aggregated health data. Health endpoints are usually daily mortality and/or daily hospital admission data from routine health registers. Air quality data are commonly obtained from one (or a few) fixed site monitoring stations. To detect the temporal association between the time-pattern in air pollution and the time-pattern in health data particular attention needs to be given to the autocorrelation structure, to the seasonality and long term trend in the data, and to the weather variables. Poisson regression with autocorrelated residuals is the suitable statistical method to analyze time studies. Furthermore, the pollutant variable can be analyzed at different lag-times to account for short latency periods in the manifestation of diseases. Studies with temporal aggregated data show the same disadvantages of the ecologic studies, although, in this case, confounding is less of a problem. Temporal studies usually are based on a large database, so that sufficient power can be achieved to detect even weak associations. Finally, the exposure information on subjects is often better characterized by short-term fluctuations in ambient air quality than is the case in geographic aggregations.

Air Pollutants↗
PubMed1995

[A critical review of epidemiological methods for spatial analysis].

Since the 1950's a number of methods have been developed whose aims is to provide enhanced mapping tools, which allow the depiction of the distribution of disease, and thereafter, to assess risks due to environmental factors (or other spatial-defined factors). Our review of statistical-epidemiological methodology for spatial analysis of diseases shall outline the distinction between global tests for clustering (detection of non casual distribution of events in an area) and cluster detection's techniques for the identification and location of abnormal aggregation of disease's cases. In this paper we evaluate each-one of the proposed methods, on general grounds, with regard to whether they meet the aims of the analysis and how successful they are in overcoming problems.

Epidemiologic Methods↗
PubMed1994

Pain relief after caesarean section: comparison of different techniques of morphine administration.

We have studied postoperative pain relief after different techniques of morphine administration given in addition to bupivacaine 15 mg during spinal anaesthesia for caesarean section. In group A, morphine was given both intravenously (10 mg) and orally (30 mg slow release MST) at the end of surgery and continued orally at 8-hourly intervals for 24 h. In group B morphine (80 microg) was given intrathecally only, with the bupivacaine. Both quality of analgesia and duration of action were better in group B, while most side-effects were more frequent in group A where a mild self limiting respiratory depression occurred in 38% of patients. Pruritus was, on the other hand, observed in 48% of patients of group B compared to 7% of the patients of group A. This study suggests that adding 80 microg of morphine to the local anaesthetic used in spinal anaesthesia for caesarean section is a simple procedure that gives excellent results in term of reliability, duration of analgesia and safety.

Journal Article↗
PubMed1994

Brain stem and motor evoked responses in "locked-in" syndrome.

A patient suffering for an ischemic "locked-in" syndrome following a subarachnoid hemorrhage, was evaluated with brain stem acoustic evoked potentials (BAEPs), short latency somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs). Neuroradiological findings failed to reveal any lesion in the brain stem, while a transcranial Doppler showed increased flow velocity upon the basilar artery, suggesting vascular spasm. BAEPs were normal and SEPs showed to be slightly impaired while MEPs upon magnetic cortical stimulation were heavily deranged. Neurophysiological investigations appeared remarkable for the early diagnosis of the disease, when neuro-radiological findings were still negative.

Adult↗