Lactobacillus acidophilus versus placebo in the symptomatic treatment of irritable bowel syndrome: the LAPIBSS randomized trial.

Irritable bowel syndrome is a chronic functional gastrointestinal disorder characterized by abdominal pain/discomfort and altered bowel habits. The use of Lactobacilli as probiotics during irritable bowel syndrome is based on their interesting mechanisms of action and their excellent safety profile but little is known about their clinical efficacy due to the lack of adequately designed clinical trials. The current clinical trial protocol aims to determine the effects of a mixture of Lactobacillus acidophilus NCFM and LAFTI L10 as probiotics to improve irritable bowel syndrome symptoms (LAPIBSS). Eighty patients with a positive diagnosis of irritable bowel syndrome according to Rome III criteria were recruited to a multicentre, double-blinded, in parallel groups, placebo-controlled randomized trial. Patients were provided with a daily dose of two capsules with two strains of Lactobacilli (5x109cfu/capsule) or placebo for 8 weeks on a 1:1 ratio. The primary outcome is to obtain scores of abdominal pain/discomfort assessed with a 100-mm visual analogue scale. The secondary outcome is to obtain scores of bloating, flatus and rumbling tested with a 100-mm visual analogue scale, composite score, stool frequency and stool consistency/appearance assessed with the Bristol Stool Form scale. According to the hypothesis that abdominal pain is mainly the result of a visceral hypersensitivity, the current study protocol aims to provide high quality proof of concept data to elucidate the efficacy of a consumption of a mixture of Lactobacillus acidophilus probiotic strains after 8 weeks, for decreasing abdominal pain. Ethical approval was given by ethics committee French Consultative Committee for the Protection of Individuals in Biomedical Research of the South West (Number CPP08-014a) and ANSM (French National Agency for Medicines and Health Products Safety - Number B80623-40). The findings from LAPBISS will be disseminated through peer-reviewed publications and at scientific conferences. TRIAL REGISTRATION: EudraCT N°2008-A00844-51.

Docosahexaenoic acid (DHA) injection in spinal cord transection stimulates Na⁺,K⁺-ATPase in skeletal muscle via ß 1 subunit.

Spinal cord injuries (SCI) induce a loss of skeletal muscle mass and functional capacity. The muscle excitability and contractility depend on the plasma membrane potential, regulated by transmembrane ion gradients, and thus necessarily on the Na⁺,K⁺-ATPase activity. The aim of this work was to evaluate the consequences of a spinal cord transection (SCT) on the skeletal muscle Na⁺,K⁺-ATPase and the impact of collateral GlyceroPhosphoLipids enriched in DocosaHexaenoic Acid (GPL-DHA) administration. The Na⁺,K⁺-ATPase activity and membrane expression of Na⁺,K⁺-ATPase α1, α2 and ß1 isoforms were assessed by K⁺-stimulated paranitrophenyl phosphatase (pNPPase) measurements and Western Blotting, respectively. The results show that spinal cord transection increased significantly (p<0.05) Na⁺,K⁺-ATPase activity in muscle by 25% and decreased the amounts of α1 isoform and α2 isoform expressions by 50% (p<0.05) respectively compared to controls. The results also show that early injection of GPL-DHA after SCT decreases in membrane skeletal muscle the α1 and α2 isoforms expression but increases the membrane Na⁺,K⁺-ATPase activity. This treament partially restores the membrane expression of the ß1 subunit of the Na⁺,K⁺-ATPase. These data suggest that the increase of ß1 subunit expression is probably the main trigger to the membrane Na⁺,K⁺-ATPase activation following a trans-synaptic denervation.

Short communication: Ischemia increases cortical Na⁺,K⁺-ATPase activity (K-Pase) in a model of kidney auto-transplantation in the large white pig.

Acute renal failure (ARF) induced by Ischemia-Reperfusion (I-R) is associated with a significant impairment of tubular sodium reabsorption. Na⁺,K⁺-ATPase has a crucial role in tubular sodium reabsorption and maintenance of water and ion homeostasis. In this study, we examined whether renal I-R affects Na⁺,K⁺-ATPase activity in a renal auto graft model (Large White Pig) with controlateral nephrectomy. Kidney samples were obtained from medulla (n = 4) and cortex (n = 3) after one hour of warm ischemia in autotransplanted models. These experimental groups were compared with a controlateral nephrectomy group (Control). Na⁺,K⁺-ATPase activity in purified membrane fractions was measured as ouabain-sensitive K⁺ -stimulated paranitrophenyl phosphatase (pNPPase) activity. The Na⁺,K⁺-ATPase activities of control, ischemia and ischemia -reperfusion were significantly higher in the medulla than in the cortex, irrespective of the experimental group (P<0.05). In cortices, Na⁺,K⁺-ATPase activity increased significantly (P<0.05) by 35% after ischemia compared to control group. In medullae, there was only a trend toward an activation of Na⁺,K⁺-ATPase activity after Ischemia (increased by 25%) and after Ischemia-Reperfusion (increased by 30%) compared to control group, and these differences did not reach statistical significance. These data suggest that renal ischemia induces a significant alteration of Na⁺,K⁺-ATPase by increasing its ouabain-sensitive K⁺-stimulated paranitrophenyl phosphatase (pNPPase) activity in isolated membrane from cortical renal tissues after one hour of ischemia. This change of activity seems to be a new regulation mechanism of an important membrane ion transporter during renal I-R in the large pig model of renal transplantation.

Vitamin D metabolism, functions and needs: from science to health claims.

BACKGROUND: Vitamin D is a nutrient long considered as essential for skeletal health but is now attracting interest from medical and nutritional communities as knowledge emerges of its biological function and its association with decreased risk of many chronic diseases. RESULTS: A question emerges: How much more vitamin D do we need for these new functions of vitamin D? This review discusses vitamin D physiology and hypovitaminosis D and presents two vitamin D dietary policies: that according to regulatory authorities and that of nutrition scientists. Scientific evidence suggests that 25(OH)D serum levels should be over 75 nmol/L; otherwise, there is no beneficial effect of vitamin D on long-latency diseases. Current regulatory authority recommendations are insufficient to reach this level of adequacy. Observational and some prospective data show that vitamin D has a role in the prevention of cancer as well as immunity, diabetes and cardiovascular and muscle disorders, which supports the actions of 1α,25(OH)2D at cellular and molecular levels. The recent assessments done by the European Food Safety Authority should lead to new health claims. CONCLUSIONS: Vitamin D, through food fortification and supplementation, is a promising new health strategy and thus provides opportunities for food industry and nutrition researchers to work together towards determining how to achieve this potential health benefit.

ω6/ω3 Polyunsaturated fatty acid supplementations in renal cell model lead to a particular regulation through lipidome for preserved ω6/ω3 ratios.

Polyunsaturated fatty acids (PUFA) supplementations modify cell lipid composition leading to a change in cell function. However, the effect of PUFA supplementations in renal model cell on the kidney epithelial cells membrane fatty acid profile is not known. Therefore, the purpose of this study was to determine the effects of PUFAs with different ω6/ω3 ratios supplementations in the kidney epithelial cells and the type of supplementation that can be used as cellular protection during kidney transplantation. For that, we used as model the LLCPK1 cell and determined their membrane fatty acid (FA) composition after supplementation with three different commercial food supplements. These supplements consist of S1: docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) with ω6/ω3 ratio = 0.1, S2: DHA, EPA, linoleic acid (LA) and γ-linoleic acid (GLA) with ω6/ω3 ratio = 2.5, or S3: α-linolenic acid (ALA) and LA with ω6/ω3 ratio near 1. Cells were incubated for 24 hr with 30 µM of ω3 fatty acids from each supplement. Fatty acid composition of control and experimental groups was analysed by gas chromatography after extraction of lipids and fatty acids methylation. The efficiency of cell PUFA supplementation was achieved by showing 2 to 4 fold increases in cell PUFA incorporation. Whatever the supplementation used, the cell saturated fatty acids (SFA) were decreased by 50% following the three supplementations used (p<0.001) as compared to control group. These decreases in SFA were compensated in part by increasing monounsaturated fatty acid levels. All these changes were observed with constant of cell ω6/ω3 ratio whatever the supplementations used. These data suggest that the supplements, with long chain polyunsaturated fatty acids or their precursors, lead to important regulation in the lipidome (desaturases and elongases) associated to preserved ω6/ω3 ratios. The fatty acids remodeling may represent an interesting new mechanism by which renal FA homoestasis could occurred.

Opinion paper food supplements: the European regulation and its application in France. Thoughts on safety of food supplements.

The first definition of food supplements in France was established by decree 96-307 of April 10th 1996. In 2002, the European Community adopted a regulation for food supplements (European Directive 2002/46/CE June 10th). This was an important event in the regulation of food supplements. The European regulation was adopted in France, with some modifications, by decree 2006-352 of March 20th 2006. The European Regulation on food supplements is more defined than those for any other food types and is exemplary. The Regulation on addition of vitamins and minerals to food differs from the regulation on the addition of other substances such as amino acids, essential fatty acids, fibers, carbohydrates, various plant, and herbal extracts. While the Regulation includes vitamins and minerals to the positive list of supplements, other substances are included in the negative list of supplements. According to the Regulation, substances added to food supplements must have a nutritional or physiological effect. The increased use of food supplements led to the creation of a department specialized in the safety of food supplement. The safety of food supplements is a permanent concern for sanitary authorities. These authorities have recently combined scientific methodological approaches and a collective expertise to implement and monitor simple and useful rules that insure consumer's safety. Safety laws aim to protect the consumers of food supplements.

Relation between α-isoform and phosphatase activity of Na+,K+-ATPase in rat skeletal muscle fiber types.

In skeletal muscle the relationship between Na+,K+-ATPase activity and isoform content remains controversial (9,6). It could be due to the fiber-type content, membrane isolation and analytical methods. We investigated the distribution of subunit α1 and α2 Na+,K+-ATPase catalytic isoforms and the Na+,K+-ATPase activity in isolated membranes from white ( type I and glycolitic fibers) and red (type II and oxidative fibers) skeletal muscles. Red Gastrocnemius and White Gastrocnemius muscles were sampled from 8 week-old female Wistar rats and crude membranes were performed. The Na+,K+-ATPase activity and membrane distribution of Na+,K+-ATPase α1 and α2 isoforms were assessed by ouabain sensitive K-phosphatase (Kpase) measurements and Western Blot respectively. The Na+,K+-ATPase activity was 6 fold lower in White Gastrocnemius membranes than in Red Gastrocnemius membranes. The α1 and α2-isoform levels are higher in RG than in White Gastrocnemius. The α1 and α2-subunit Red Gastrocnemius content was significantly higher than in WG. The correlation between crude membrane Kpase activity and both catalytic α-subunit of the Na+,K+-ATPase exist.These data suggest that the Na+,K+-ATPase phosphatase activity correlates with the α1 and α2 isoforms levels in Red Gastrocnemius and White Gastrocnemius and confirms the fiber-specific Na+,K+-ATPase catalytic α-subunits and α2-isoform as the major catalytic isoform in rat skeletal muscle.

Effect of a novel Omegacoeur®/Doluperine® nutritional combination on human embryonic kidney cell viability.

Holistica Laboratories (Eguilles, France) developed the nutritional supplements Omegacoeur® and Doluperine® based on two of the most ancient and unique dietary health traditions. Omegacoeur® is formulated to supply key active components of Mediterranean diet (omega 3,6,9 fatty acids, garlic, and basil) and the formulation of Doluperine® was based on the Ayurvedic tradition (curcuma, pepper, ginger extracts). Interestingly, recent studies suggest that an combination of the ingredients supplied by these two supplements could provide additional and previously unanticipated benefit through synergistic actions of some of their key components. However, the effect of such combination on human cell viability has not been investigated. In this present article, a review of the various effects of the individual compounds of the new combination and the reported active doses, and the result of a study of an combination of Omegacoeur® / Dolupérine® on Human Embryonic Kidney (HEK 293) cells. Incremental doses of 4 Omegacoeur® / Dolupérine® combinations prepared so that the molar ratio DHA (Docosahexaenoic acid) in Omegacoeur® / curcumin in Dolupérine® was kept constant, at 2.5 DHA / 1 curcumin, were added to the culture media. After 24h of incubation, cell viability was assessed by the trypan blue exclusion method. The data suggest that the combination of Omegacoeur® with Dolupérine® does not affect HEK 293 cells viability in the range of doses that have demonstrated beneficial effects in earlier studies.

7-ketocholesterol inhibits Na,K-ATPase activity by decreasing expression of its α1-subunit and membrane fluidity in human endothelial cells.

As cholesterol, oxysterols, can insert the cell membrane and thereby modify the functions of membrane-bound proteins. The Na,K-ATPase is very sensitive to its lipid environment, seems to be involved in important endothelial functions as the regulation of nitric oxide (NO) release. The effects of 7-ketocholesterol , an oxysterol present in oxidized LDL, was investigated on Na,K-ATPase in isolated human endothelial cells. Cells were incubated 24h with lecithin-, cholesterol- or 7-ketocholesterol liposomes (6 µg/ml). K+-stimulated paranitrophenyl phosphatase activity, reflecting Na,K-ATPase activity, was evaluated as well as cell viability and lipoperoxidation. The expression of Na,K-ATPase subunits mRNAs and membrane fluidity were also investigated. As Na,K-ATPase and nitric oxide seem to be related, we determined the production of NO and the expression of endothelial NO synthase mRNAs. Na,K-ATPase activity was strongly decreased by 7-ketocholesterol. This decrease, not related to lipoperoxidation, was correlated with a decreased expression of the Na,K-ATPase α1-subunit messengers and with rigidity of plasma membranes. Cholesterol induced similar effects but was less potent than 7-ketocholesterol. Basal NO production and expression of endothelial NO synthase mRNAs were not modified by 7-ketocholesterol. Our new findings demonstrate that 7-ketocholesterol, used at non toxic doses, was very potent to disrupt the transport of ions by Na,K-ATPase and perturb membrane structure. These data demonstrate that 7-ketocholesterol induces endothelial dysfunction without cell death that may contribute to early events in atherosclerosis.

[Morphological study of CNS lesions and the consequences on rat neuromuscular junction and peripheral nerve using confocal laser scanning microscopy and Koelle's technique]. / Existe-t-il un retentissement sur la jonction neuromusculaire de rat lors de lésions du système nerveux central ? Etude morphologique en microscopie confocale et technique de Koelle.

STATE OF THE ART: In humans, it is currently believed that peripheral nerves remain intact after central nervous system (CNS) injuries. This should lead us to observe a lack of amyotrophy in the peripheral projection areas of CNS damage. Nevertheless, the appearance of amyotrophy, described as underuse amyotrophy, is common in victims of CNS injury. Its pathophysiology remains poorly understood and is currently being debated. Amyotrophy could result directly from the structural deterioration of a nervous fiber in the muscular area corresponding to the CNS injury caused by neuromuscular junction (NMJ) changes. AIMS OF THIS STUDY: The aims of this study were to assess the repercussions of a CNS injury on the NMJ and peripheral nerve complex and to evaluate the involvement of peripheral nerves and NMJs in plasticity. METHODOLOGY: Peripheral nerve and muscle biopsies were collected from a group of 35 female Wistar rats that had previously undergone a thoracic spinal cord hemisection (15 rats at the T2 level (group 1), 15 rats at the T6 level (group 2), and 5 matched rats used as controls). We studied the localization and expression of the NMJ molecular components in muscle specimens by immunohistochemistry using confocal microscopy. We also searched for signs of nerve and muscle degeneration using light and electron microscopy. RESULTS: We observed nonpathologic NMJs coexisting with completely denervated and partially reinnervated NMJs. We also found characteristics of embryonic behavior in rat axons secondary to axonal caliber distortions. Some authors associate this decrease in axonal activity with physiological denervation. CONCLUSION: This project was designed to improve the understanding of the mechanisms involved in the interactions between the first and second motoneurons after different types of CNS injuries, with variable functional repercussions. Our results strongly suggest that CNS injuries lead to both morphological and functional repercussions at the NMJ and the peripheral nerve.

[Pathophysiological, molecular and metabolic changes at the neuromuscular junction and the peripheral nerve after central nervous system lesions in humans]. / Caractérisation physiopathologique, moléculaire et métabolique de la jonction neuromusculaire et du nerf périphérique après lésion du système nerveux central chez l'homme.

From the elaborate information processing that takes place in the brain to the contraction of skeletal muscles, the neurotransmission pathways involve, at least in part, (1) in tissue, Na+, K+-ATPase electrogenesis making action potential (AP) propagation possible and (2) in the cell, the synthesis, maturation, and renewal of an amazing number of molecules concentrated at the neuromuscular junction (NMJ). Our aim is to clarify CNS and peripheral nerve system (PNS) interactions by determining whether the partial motor recovery sometimes observed after a lesion of the first motoneuron is related to (1) changes in active transportation of the ions in peripheral nerve and/or muscle and (2) morphological and/or molecular changes at the NMJ, illustrating a dysfunction. Peripheral nerve surgery is proposed to some spastic patients who have recovered partially after CNS lesions to improve their gait. During these surgical procedures, the nerve and muscle samples that are usually resected can be collected and analyzed. Here, we report on eight patients who showed strictly similar motor recovery 2 years after massive CNS lesions and who underwent a selective tibial neurotomy for a spastic equinus foot. In these eight spastic patients, we performed a pathophysiological, molecular, and metabolic study of their neuromuscular junctions and peripheral nerves to characterize the dysfunction of the neuromuscular transmission after a permanent CNS injury.

[Tools and techniques dedicated to neuromuscular junction observation]. / Modalités et outils d'observation de la jonction neuromusculaire.

A few decades ago, the neuromuscular junction (NMJ) concept was reduced to two elements: the nerve ending and the facing muscular zone. This description has since changed substantially based on recent studies conducted on the molecular aspects of neurotransmission. The aim of this paper is to provide a synthetic view of the major morphological, molecular and electrophysiological tools used in the analysis of NMJ architecture and its functional characterization.

[Energetic applications: Na+/K+-ATPase and neuromuscular transmission]. / Applications énergétiques: Na/K-ATPase et transmission neuromusculaire.

Na/K-ATPase electrogenic activity and its indispensable role in maintaining gradients suggest that the modifications in isoform distribution and the functioning of the sodium pump have a major influence on both the neuronal functions, including excitability, and motor efficiency. This article proposes to clarify the involvement of Na/K-ATPase in the transmission of nerve influx within the peripheral nerve and then in the genesis, the maintenance, and the physiology of muscle contraction by comparing the data found in the literature with our work on neuron and muscle characterization of Na/K-ATPase activity and isoforms.

[Major mechanisms involved in the synaptic transmission of the neuromuscular apparatus]. / Principaux mécanismes impliqués dans la transmission synaptique au sein de l'appareil neuromusculaire.

Neuromuscular transmission results from a double signal transduction from electric impulses to chemical messengers, taking place at a highly differentiated region, the neuromuscular junction (NMJ). A nerve cell responds to a specific stimulus by modifications of its plasmic membrane properties, generating an action potential (AP). This electric signal is transmitted along the axon to the NMJ, where it induces the voltage-gated calcium channels to open. Intracellular calcium entry leads to acetylcholine release in the synaptic space at the active zones but all scientists do not consider it the major release factor. Acetylcholine binding with its receptor at the muscle membrane generates an endplate potential when the induced depolarization is greater than the sodium voltage channel opening threshold. Muscle AP causes a muscle contraction involving the three phases. This paper will successively review the electrophysiological and molecular mechanisms involved at the pre-, inter- and postsynaptic levels. The last part of the article will discuss electromechanical considerations directly affecting the mechanical properties of the muscle fiber, most particularly the factors influencing the predetermined involvement of motor units, motor neuron electrical properties determining responses to synaptic inputs and finally the impact of recruited motor neurons and their electrical impulse rates on muscle contraction strength and velocity.

[Toward a metabolic approach of the central pattern generator concept in a spinal rat model]. / Vers une approche métabolique du centre locomoteur autonome chez l'animal: le modèle d'hémisection médullaire chez le rat.

It has been shown that the onset of a central nervous system lesion in the rat results in morphological modifications of the peripheral nerves and the underlying neuromuscular junctions, without suggesting a functional correlation between recuperation of motor functions and sublesional metabolic activity. Using double lesion localization (T2 and T6) in a spinal rat model has nevertheless pointed out the functional importance of the T2-T6 metameric interval in the reinnervation phenomena observed, raising the problem of spinal generation in locomotor movements. Motivated by electrophysiological data that have given support to the concept of an anatomic substrate for these intramedullary rhythm generators, we attempted to establish a relation between the functional recuperation possible after a central nervous system lesion and modifications within the metabolism of the underlying neuromuscular system. We notably focused on Na/K-ATPase, whose crucial role in neuromuscular transmission has been evidenced. This paper proposes to demonstrate the involvement in the mechanisms of metabolic regulation after trans-synaptic denervation, i.e., a central nervous system lesion. Our study includes the Na/K-ATPase activity analysis on the sublesional peripheral nerve and the combined analysis of the expression of different RNA messengers within the corresponding muscle groups. We have also investigated the spatiotemporal organization of the compensating processes of the nerves underlying the lesion using magnetic resonance spectroscopy.

The standardized Ginkgo biloba extract Egb-761 protects vascular endothelium exposed to oxidized low density lipoproteins.

Dietary antioxidants are frequently proposed as protective agents for the vascular endothelium during the onset of atherosclerosis. This protection may occur at two distinct levels. First, they prevent oxidative modification of atherogenic lipoproteins (LDL). Second, they can provide a cellular protection against oxidized LDL-mediated endothelium dysfunction, although this mechanism remains poorly considered in many instances. To gain insight into the mechanism underlying such cellular protection against oxidized LDL, we examined the impact of a popular traditional medicine, an extract from Ginkgo biloba with well-known antioxidant properties, on two endothelial cells properties: cell adhesion and ionic homeostasis. Cellular lipoperoxides levels were also measured as a marker of cellular oxidative stress. Human umbilical-vein endothelial cells were exposed to native (nat-) or oxidized (ox-) LDL, the latter prepared to be compatible with clinically observed levels of oxidation. Although nat-LDL had little effect, ox-LDL increased endothelial adhesive properties (35%, p<0.01) and lipoperoxidation (45%, p<0.01). Na,K-ATPase activity, a key regulator of ionic homeostasis, was significantly decreased after exposure to nat-LDL (30%, p<0.01) and dramatically depressed after exposure to ox-LDL (65%, p<0.001). The standardized preparation of Ginkgo biloba EGb-761 totally protected adhesive properties and endothelial lipoperoxide levels. Moreover, it limited the decrease in Na,K-ATPase activity induced by ox-LDL to levels similar to nat-LDL. This suggests that EGb-761 protects endothelial adhesive properties and helps prevent the disruption of ionic homeostasis. The EGb-761-mediated inhibition of ox-LDL-induced lipoperoxide levels in endothelial cells appears to be an important mechanism by which Ginkgo biloba extract protects endothelial properties.

A high calorie diet induces type 2 diabetes in the desert sand rat (Psammomys obesus).

Diabetes mellitus type 2 is a major factor for cardiovascular diseases. The toxic effects of chronic hyperglycemia involve many alterations in the vascular tissue, including atherosclerosis. The pathogenesis of atherosclerosis in the diabetic syndrome (DS-II) has not been fully elucidated. A better understanding of the progress of DS-II at the level of the aorta could help us to identify inhibitors of atherosclerosis. Studies have shown that obesity and high calorie diet (HCD) are associated with the development of DS-II, however the lack of naturally occurring experimental models of DS-II have impaired to directly address these issues. We hypothesize that a HCD induces DS-II. This study (15 months duration) is designed to determine if HCD induces DS-II in the desert sand rat (Psammomys obesus; P. obesus). We also evaluated the histopathology of the aorta in animals fed with a laboratory chow pellets ad libitum (hypercaloric) and in control (animals fed with the naturally occurring hypocaloric diet; halophile plants). The weight and blood chemistry (glucose, lipids, and insulin levels) were evaluated periodically (once per week), and the histology of the aortas of these animals were assessed every 3 months for up to 12 months, during the development of DS-II. This study demonstrates that 40% of the animals in HCD develop DS-II at 3 months. Histological characterization demonstrates the typical alterations observed in atherosclerosis, i.e., alteration of the elastic fibers of the media layer and enrichment in collagen and glucosaminoglycans. This study demonstrates that P. obesus is an excellent animal model to study the progression of DS-II and the development of atherosclerosis.

Anti-arrhythmic effects of I (Na), I (Kr), and combined I (Kr)-I (CaL) blockade in an experimental model of acute stretch-related atrial fibrillation.

INTRODUCTION: Atrial dilatation is commonly associated with atrial fibrillation (AF), but the electrophysiological mechanisms and the implications for anti-arrhythmic therapy are poorly understood. In a model of acute stretch-related AF in isolated rabbit hearts, we evaluated the electrophysiological effects of three different anti-arrhythmic drugs: dofetilide, flecainide and BRL-32872 (associating I (Kr) and I (CaL) blocking properties). METHODS: After 30 min of sustained stretch-related AF, we perfused BRL 10-7 M, BRL 3.10-7 M, BRL 10-6 M, flecainide 2.4 10-6 M and dofetilide 10-7 M and iteratively measured atrial effective refractory periods (ERPs), AF inducibility and AF cycle length (AFCL) 15, 30 and 60 min after drug perfusion, respectively. RESULTS: After a significant shortening of the ERPs by acute atrial stretch in the five groups individually (p < 0.001, stretch vs baseline for each group individually), drug perfusion led to a strong lengthening of AFCL, a very significant prolongation of ERPs (p < 0.001 vs stretch) and a reduction of AF inducibility (p < 0.01 vs control group) for each of the five experimental groups. The relative ERP increase was comparable in all groups, whereas a significantly lower AF inducibility was observed in the BRL 10-6 M group (p < 0.05 vs other BRL concentrations). CONCLUSION: In a model of acute stretch-related AF, dofetilide, flecainide and BRL-32872 terminated AF and prevented its immediate reinduction after having comparatively prolonged AFCL and ERPs. These comparative results suggest that those drugs are equally efficacious, albeit with different mechanisms, in the setting of acute atrial stretch.

The Na, K-ATPase alpha3-isoform specifically localizes in the Schmidt-Lanterman incisures of human nerve.

INTRODUCTION: To our knowledge, there is little reference in literature with regards to alpha3-isoform of Na+,K+-ATPase in human peripheral nerves. The aim of this study was to determine the expression of the neuronal alpha3-isoform of Na+,K+-ATPase in human sural nerves from patients with a permanent medullary central nervous system injury. MATERIALS AND METHODS: We studied the immunolocalization of alpha3-isoform of Na+,K+-ATPase using a polyclonal antibody against the amino sequence near the phosphorylation site of the alpha3-isoforms of Na+,K+-ATPase using immunohistochemistry and confocal laser scanning microscopy. An antibody specific for alpha2-isoform of Na+,K+-ATPase was used to label the Schwann cells. RESULTS: Morphometric analysis of longitudinal section of human sural nerves showed that the alpha3-isoform of Na+,K+-ATPase was distributed along the length of axolemma. The myelin sheath of the Schwann cells showed clearly a distribution of alpha3- but not alpha2-isoforms of Na+,K+-ATPase at the level of Schmidt-Lanterman incisures. CONCLUSION: The human sural nerve shows a specific localization of the Na+,K+-ATPase alpha3-isoform in the Schmidt-Lanterman incisures of Schwann cells in addition to its localization in axonal membranes.

Peripheral diabetic neuropathy and polyunsaturated fatty acid supplementations: natural sources or biotechnological needs?

The two essential fatty acids linoleic and alpha-linolenic acids, precursors of the n-6 and n-3 PUFA family, respectively, are known to play a strong regulatory function on cells via their incorporation into membrane phospholipids, and also on microcirculation by the production of eicosanoids. Moreover, diabetes mellitus induces impairment in PUFA metabolism due to an inhibition of desaturases, the enzymes involved in their synthesis. The decrease in PUFA bioavailability will conduct to marked alterations in membranes as well as impairment of the microcirculation. Those metabolic perturbations are involved in part in the degenerative complications of diabetes such as neuropathy. Nutritional supplementations with PUFA have given very interesting results in experimental diabetic neuropathy but also in human diabetic neuropathy. The gamma linolenic and arachidonic acids, members of the n-6 family, prevent the physiological abnormalities associated to neuropathy. The results obtained with the n-3 family PUFA are more discordant, probably because of the simultaneous use of eicosapentaenoic and docosahexaenoic acids. Nevertheless, the use of docosahexaenoic acid-enriched phospholipids produced positive results in the treatment of experimental diabetic neuropathy. These PUFA are available from natural sources but a biotechnological demand exists to provide these PUFA in different structural forms.