Biomedical subjects

C Mattei

Publications and source records attributed to C Mattei.

At least 19 recordsLinked to original sources

PubMed2001

Multicenter randomized evaluation of a nutritional education software in obese patients.

OBJECTIVE: To study the efficacy of the nutritional education software, Nutri-Expert, in the management of obese adult patients. MATERIAL AND METHODS: Two groups of obese patients were followed up over one year in a randomized study: the first group received close traditional management (seven nutritional visits over the year, with physicians and dietitians conjointly) and the second one also used at home by Minitel the Nutri-Expert system. 557 patients were enrolled in the study by 16 French centers of diabetology and nutrition. Body mass index (BMI), tests of dietetic knowledge, dietary records and centralized biological measurements were assessed at inclusion, 6 and 12 months. 341 patients were evaluable at the end of the year. RESULTS: The group using Nutri-Expert scored significantly better in the tests of dietetic knowledge than the control group. For all patients, nutritional education led to a significant improvement in BMI, dietary records and biological measurements, without significant difference between the two groups. Five years after the end of the study, the weight of 148 patients was recorded; mean BMI was significantly lower than the initial value but there was no significant difference between the two groups. CONCLUSION: In the management of obese patients, Nutri-Expert system has a role to play in reinforcing nutritional knowledge; if regular follow-up is not possible, or if a large series of obese patients is to be treated, Nutri-Expert could partly replace traditional management, for example between visits.

Adult↗

PubMed2000

Leaky wave detection at air-solid interfaces by laser interferometry

A recently developed optical heterodyne interferometer is proved to be sensitive to detect ultrasonic waves leaking out from metals (and from non-metals as well) several centimeters away from the metal surface in air. This measurement is based on the detection of the optical index variation in air due to the leaky wave. Experiments were carried out using both ultrasonic leaky Rayleigh and leaky Lamb waves in the low-megahertz region. Optical measurements of these leaky wave velocities in semi-infinite materials and plates, which are related to elastic constants of the materials, showed a good correlation to the predicted values. Optical measurements of the amplitude of the leaky waves were used to obtain attenuation coefficients, which correlate to the structural integrity of the materials. Surface and near-surface defects were also detected. This optical method can be used for metals with low-reflectivity surfaces. Thus, it can be used for non-polished surfaces and can be extended for non-contact, non-destructive evaluation applications.

Journal Article↗

PubMed2000

Trachynilysin mediates SNARE-dependent release of catecholamines from chromaffin cells via external and stored Ca2+.

Trachynilysin, a 159 kDa dimeric protein purified from stonefish (Synanceia trachynis) venom, dramatically increases spontaneous quantal transmitter release at the frog neuromuscular junction, depleting small clear synaptic vesicles, whilst not affecting large dense core vesicles. The basis of this insensitivity of large dense core vesicles exocytosis was examined using a fluorimetric assay to determine whether the toxin could elicit catecholamine release from bovine chromaffin cells. Unlike the case of the motor nerve endings, nanomolar concentrations of trachynilysin evoked sustained Soluble N-ethylmaleimide-sensitive fusion protein Attachment Protein REceptor-dependent exocytosis of large dense core vesicles, but only in the presence of extracellular Ca2+. However, this response to trachynilysin does not rely on Ca2+ influx through voltage-activated Ca2+ channels because the secretion was only slightly affected by blockers of L, N and P/Q types. Instead, trachynilysin elicited a localized increase in intracellular fluorescence monitored with fluo-3/AM, that precisely co-localized with the increase of fluorescence resulting from caffeine-induced release of Ca2+ from intracellular stores. Moreover, depletion of the latter stores inhibited trachynilysin-induced exocytosis. Thus, the observed requirement of external Ca2+ for stimulation of large dense core vesicles exocytosis from chromaffin cells implicates plasma membrane channels that signal efflux of Ca2+ from intracellular stores. This study also suggests that the bases of exocytosis of large dense core vesicles from motor nerve terminals and neuroendocrine cells are distinct.

Animals↗

PubMed1999

Hyperosmolar D-mannitol reverses the increased membrane excitability and the nodal swelling caused by Caribbean ciguatoxin-1 in single frog myelinated axons.

The effects of hyperosmolar D-mannitol were studied on single frog myelinated nerve fibres previously poisoned with Caribbean ciguatoxin-1 (C-CTX-1), a new toxin isolated from the pelagic fish Caranx latus inhabiting the Caribbean region. In current-clamped myelinated axons, C-CTX-1 (50-120 nM) caused spontaneous and repetitive action potential discharges after a short delay. In addition, the toxin produced a marked swelling of nodes of Ranvier of myelinated axons that reached a steady state within about 90 min, as revealed by using confocal laser scanning microscopy. The increased excitability and the nodal swelling caused by C-CTX-1 were prevented or reversed by an external hyperosmotic solution containing 100 mM D-mannitol. Moreover, the C-CTX-1-induced nodal swelling was completely prevented by the blockade of voltage-sensitive sodium channels by tetrodotoxin (TTX). It is suggested that C-CTX-1, by increasing nerve membrane excitability, enhances Na(+) entry into nodes of Ranvier through TTX-sensitive sodium channels, which directly or indirectly disturb the osmotic equilibrium between intra- and extra-axonal media resulting in an influx of water that was responsible for the long-lasting nodal swelling. The fact, that hyperosmolar D-mannitol either reversed or prevented the neurocellular actions of C-CTX-1, is of particular interest since it provides the rational basis for its use to treat the neurological symptoms of ciguatera fish poisoning in the Caribbean area.

Action Potentials↗

PubMed1999

Naftazone reduces glutamate cerebro spinal fluid levels in rats and glutamate release from mouse cerebellum synaptosomes.

It is well known that an excessive release of glutamate in the mammalian brain plays a major role in several neurological diseases. Naftazone (Etioven) is a currently used vasoprotectant drug that is metabolized in humans by reduction and glucuronidation. In the present study naftazone was found to decrease glutamate levels in the cerebro spinal fluid (CSF) of rats treated for 15 days, as determined by a chemiluminescent glutamate assay reaction. Naftazone and its glucuronide derivative also reduced respectively spontaneous and high K+-evoked glutamate release from mouse cerebellum synaptosomes. It is likely that naftazone and its glucuronide metabolite contribute in vivo to decrease glutamate levels in the CSF through their inhibitory actions on glutamate release.

Animals↗

PubMed1999

Neurotoxins targetting receptor site 5 of voltage-dependent sodium channels increase the nodal volume of myelinated axons.

The effects of a C57 type ciguatoxin (CTX-3C) and two types of brevetoxins (PbTx-1 and PbTx-3), known to bind to receptor site 5 of the neuronal voltage-dependent Na+ channel-protein, were studied on the morphology of living frog myelinated axons using confocal laser scanning microscopy. During the action of CTX-3C, PbTx-1, and PbTx-3 (10-50 nM), a marked swelling of nodes of Ranvier was observed without apparent modification of internodal parts of axons. In all cases, toxin-induced nodal swelling attained a steady-state within 75-100 min that was well maintained during an additional 90-115 min. The nodal swelling was reversed by an external hyperosmotic solution containing 100 mM D-mannitol and could be completely prevented by blocking voltage-dependent Na+ channels with 1 microM tetrodotoxin. It is suggested that CTX-3C, PbTx-1, and PbTx-3 by activating Na+ channels cause a continuous Na+ entry into axons, increasing internal Na+ concentration. Such an increase directly or indirectly disturbs the osmotic equilibrium between intra- and extra-axonal media, resulting in an influx of water, which is responsible for the long-lasting nodal swelling. Similar results were previously reported with two C60 type ciguatoxins (CTX-1B and CTX-4B). Thus, it is concluded that the four types of toxins targetting receptor site 5 of neuronal voltage-dependent Na+ channels, not only enhance nerve membrane excitability but also, on a long-term basis, cause a marked increase in the axonal volume.

Animals↗

PubMed1999

A new conotoxin isolated from Conus consors venom acting selectively on axons and motor nerve terminals through a Na+-dependent mechanism.

A novel conotoxin was isolated and characterized from the venom of the fish-hunting marine snail Conus consors. The peptide was identified by screening chromatography fractions of the crude venom that produced a marked contraction and extension of the caudal and dorsal fins in fish, and noticeable spontaneous contractions of isolated frog neuromuscular preparations. The peptide, named CcTX, had 30 amino acids and the following scaffold: X11CCX7CX2CXCX3C. At the frog neuromuscular junction, CcTx at nanomolar concentrations selectively increased nerve terminal excitability so that a single nerve stimulation triggered trains of repetitive or spontaneous synaptic potentials and action potentials. In contrast, CcTx had no noticeable effect on muscle excitability even at concentrations 100 x higher than those that affected motor nerve terminals, as revealed by direct muscle stimulation. In addition, CcTx increased miniature endplate potential (MEPP) frequency in a Ca2+-free medium supplemented with ethylene glycol-bis-(beta-aminoethyl ether)-N,N,N', N'-tetraacetic acid (EGTA). Blockade of voltage-dependent sodium channels with tetrodotoxin (TTX) either prevented or suppressed the increase of MEPP frequency induced by the toxin. CcTx also produced a TTX-sensitive depolarization of the nodal membrane in single myelinated axons giving rise, in some cases, to repetitive and/or spontaneous action potential discharges. In addition, CcTx increased the nodal volume of myelinated axons, as determined using confocal laser scanning microscopy. This increase was reversed by external hyperosmolar solutions and was prevented by pretreatment of axons with TTX. It is suggested that CcTx, by specifically activating neuronal voltage-gated sodium channels at the resting membrane potential, produced Na+ entry into nerve terminals and axons without directly affecting skeletal muscle fibres. CcTx belongs to a novel family of conotoxins that targets neuronal voltage-gated sodium channels.

Action Potentials↗

PubMed1999

[Ciguatoxins and brevetoxins: dissection of the neurobiological actions].

This review focuses on the neurobiological actions of ciguatoxins and brevetoxins which are phycotoxins produced respectively by the dinoflagellates Gambierdiscus toxicus and Ptychodiscus brevis. These actions are illustrated in particular by the effects of the toxins on myelinated nerve fibres and on skeletal neuromuscular junctions of vertebrates. Ciguatoxins and brevetoxins, through different vectors, are responsible for human intoxications characterized mainly by neurological disturbances. The molecular target of these families of lipid-soluble cyclic polyethers is the voltage-gated sodium channel, a fundamental transmembrane protein involved in cellular excitability. The different toxins share a common binding site (the receptor-site 5) located on the alpha sub-unit of this neuronal transmembrane protein. Electrophysiological studies of the mode of action of ciguatoxins and brevetoxins identify these toxins as specific sodium channel activators. Indeed, during the action of these phycotoxins, sodium channels remain permanently opened, at the resting membrane potential, which produces a continuous entry of sodium ions in most excitable cells. Such a sodium entry has various consequences on sodium-dependent physiological mechanisms, consisting in a membrane depolarization which, in turn, causes spontaneous and/or repetitive action potential discharges and thereby increases membrane excitability. These neuronal discharges may be transient or continuous according to the preparation and the toxin tested. The increase in membrane excitability during the action of ciguatoxins and brevetoxins is responsible for the different effects exerted by these toxins on various chemical synapses and secretory cells. Another consequence of the continuous entry of sodium ions into cells was revealed using confocal laser scanning microscopy and vital staining of plasma membranes with the fluorescent dye FM1-43. These techniques made feasible the dynamic study of morphological alterations produced by ciguatoxins and brevetoxins on various cellular preparations in situ. Thus, it has been possible to bring to the fore that these phycotoxins cause a marked increase in the volume of nodes of Ranvier of myelinated nerve fibres, motor nerve terminals innervating skeletal muscle and perisynaptic non-myelinating Schwann cell somata. This increase could be reversed by hyperosmotic external solutions and completely prevented by the blockade of voltage-gated sodium channels. The mechanisms involved in the increase in cellular volume, during the action of ciguatoxins and brevetoxins, are discussed.

Animals↗

PubMed1998

The wheat proteins puroindoline-a and alpha1-purothionin induce nodal swelling in myelinated axons.

The effects of two basic cysteine-rich lipid-binding proteins isolated from wheat seedlings, puroindoline-a and alpha1-purothionin, were studied on single frog myelinated axons stained with the fluorescent dye FM1-43 using confocal laser scanning microscopy. During exposure to either puroindoline-a or alpha1-purothionin (10 and 100 microM) a marked swelling of nodes of Ranvier was observed, provided NaCl was present in the external solution. It is suggested that these proteins increase the internal osmolality by forming pores in the axonal membrane and induce water influx to compensate for such an increase. Moreover, in the presence of alpha1-purothionin (100 microM), the intensity of the axonal staining with FM1-43 was increased. It is the first time, to our knowledge, that basic proteins containing domains of a cysteine-rich repeated motif are reported to produce swelling and water movements across neuronal cell membranes.

Animals↗

PubMed1998

Diverging evolution of anti-GAD and anti-IA-2 antibodies in long-standing diabetes mellitus as a function of age at onset: no association with complications.

Glutamic acid decarboxylase autoantibodies (GAD-A) and tyrosine phosphatase IA-2 autoantibodies (IA2-A) were measured in sera of 50 recently diagnosed (<6 wk, 33% younger than 15 yr), 19 short-term (1 to 9 yr, 35% with onset age below 15 yr) and 89 long-standing diabetic patients (>10 yr, 57% with onset age below 15 yr). Complications were assessed by clinical examination, retinal angiographs and microalbuminuria measurement. Both prevalences and levels of GAD-A and IA2-A decreased with increasing duration of diabetes. However even in those with long duration diabetes, 15 to 63% of the sera were still positive for one or two antibodies. In the group with onset after the age of 15 yr, significantly higher prevalences and levels of GAD-A (but not IA2-A) was observed in comparison with the group with earlier onset. No association was found with any microvascular complications in any group. We conclude that GAD-A and IA2-A persist in some diabetic patients, despite a long duration. Persistence of GAD-A was greatest in those with postpubertal disease onset. We speculate that persistence of some beta-cells or specific environmental factors can sustain one autoimmune reaction especially in some postpubertal-onset diabetic patients.

Adolescent↗

PubMed1997

Gambiertoxin (CTX-4B), purified from wild Gambierdiscus toxicus dinoflagellates, induces Na(+)-dependent swelling of single frog myelinated axons and motor nerve terminals in situ.

The effects of gambiertoxin (CTX-4B), purified from the dinoflagellate Gambierdiscus toxicus, were assessed on the morphology of both frog myelinated axons and motor nerve terminals, using confocal laser scanning microscopy. During the action of the toxin (24 and 30 nM), a marked swelling of nodes of Ranvier and motor nerve terminals was observed. The CTX-4B-induced swelling could be prevented by blocking voltage-dependent Na+ channels with tetrodotoxin, and could be partly reversed by an external hyperosmotic solution containing 100 mM D-mannitol. The results suggest that CTX-4B, by modifying voltage-dependent Na+ channels, increases internal Na+ concentration of axons and nerve terminals and consequently induces water influx to compensate such an increase. It is suggested that stimulated transmitter release by CTX-4B, as well as by hyperosmotic dmannitol, contribute also to the swelling of the terminals through an increase in their surface area.

Animals↗

PubMed1995

[Multicenter evaluation of the Nutri-Expert Telematic System in diabetic patients].

Nutri-Expert is a system for self-monitoring and dietetic education, accessible through Minitel. A preliminary randomised evaluation of one hundred diabetic patients in the Midi-Pyrénées region showed that Nutri-Expert improved dietetic knowledge, dietary habits and metabolic balance. The aim of the present study was to show that the system can be successfully prescribed to patients by physicians outside the center which originated it, indicating the benefit of a wider use of Nutri-Expert, among the diabetic population. One hundred and fifty-five patients, recruited by six French centres of diabetology, used Nutri-Expert from their homes for six months. Clinical examination, tests of dietetic knowledge and biological tests, including lipid fractions, were carried out before and after six months of use. After six months, there was a significant improvement in the patients' dietetic knowledge and in some biological parameters. Nutri-Expert is thus useful even when prescribed by a centre other than the hospital which devised the system. It is an additional beneficial tool in the ambulatory management of diabetic patients.

Adolescent↗

PubMed1987