N exchanges in hyperbaric environments: towards a model based on physiological gas transport (O and CO).

Decompression sickness can occur in divers even when recommended decompression procedures are followed. Furthermore, the physiological state of individuals can significantly affect bubbling variability. These informations highlight the need for personalized input to improve decompression in SCUBA diving.

Keratinocytes Communicate with Sensory Neurons via Synaptic-like Contacts.

Objective: Pain, temperature, and itch are conventionally thought to be exclusively transduced by the intraepidermal nerve endings. Although recent studies have shown that epidermal keratinocytes also participate in sensory transduction, the mechanism underlying keratinocyte communication with intraepidermal nerve endings remains poorly understood. We sought to demonstrate the synaptic character of the contacts between keratinocytes and sensory neurons and their involvement in sensory communication between keratinocytes and sensory neurons.

TGF-β Pathway Inhibition Protects the Diaphragm From Sepsis-Induced Wasting and Weakness in Rat.

Sepsis is a frequent complication in patients in intensive care units (ICU). Diaphragm weakness, one of the most common symptoms observed, can lead to weaning problems during mechanical ventilation. Over the last couple of years, members of the transforming growth factor (TGF) β family, such as myostatin, activin A, and TGF-β1, have been reported to strongly trigger the activation of protein breakdown involved in muscle wasting.

In Vitro Differentiation of Human Skin-Derived Cells into Functional Sensory Neurons-Like.

Skin-derived precursor cells (SKPs) are neural crest stem cells that persist in certain adult tissues, particularly in the skin. They can generate a large type of cell in vitro, including neurons. SKPs were induced to differentiate into sensory neurons (SNs) by molecules that were previously shown to be important for the generation of SNs: purmorphamine, CHIR99021, BMP4, GDNF, BDNF, and NGF.

Polarization-resolved second harmonic microscopy of skeletal muscle in sepsis.

Polarization-resolved second harmonic generation (P-SHG) microscopy is able to probe the sub-micrometer structural organization of myosin filaments within skeletal muscle. In this study, P-SHG microscopy was used to analyze the structural consequences of sepsis, which is the main cause of the critical illness polyneuromyopathy (CIPNM). Experiments conducted on two populations of rats demonstrated a significant difference of the anisotropy parameter between healthy and septic groups, indicating that P-SHG microscopy is promising for the diagnosis of CIPNM.

The diaphragm is better protected from oxidative stress than hindlimb skeletal muscle during CLP-induced sepsis.

Objectives: The aim of this study was to determine whether non-lethal sepsis induced by cecal ligation and puncture (CLP) modulates oxidative damage and enzymatic antioxidant defenses in diaphragm and hindlimb skeletal muscles (soleus and Extensor Digitorus Longus (EDL)).

Methods: Female Wistar rats were divided into four experimental groups: (1) control animals, (2) animals sacrificed 2 hours or (3) 7 days after CLP, and (4) sham-operated animals. At the end of the experimental procedure, EDL, soleus, and diaphragm muscles were harvested and 4-hydroxynonenal (HNE)-protein adducts and protein carbonyl contents were examined in relation to superoxide dismutase and catalase expression and activities.

Single Muscle Immobilization Decreases Single-Fibre Myosin Heavy Chain Polymorphism: Possible Involvement of p38 and JNK MAP Kinases.

Purpose: Muscle contractile phenotype is affected during immobilization. Myosin heavy chain (MHC) isoforms are the major determinant of the muscle contractile phenotype. We therefore sought to evaluate the effects of muscle immobilization on both the MHC composition at single-fibre level and the mitogen-activated protein kinases (MAPK), a family of intracellular signaling pathways involved in the stress-induced muscle plasticity.

Activation of primary sensory neurons by the topical application of capsaicin on the epidermis of a re-innervated organotypic human skin model.

Using an ex vivo skin-nerve preparation, skin and nerve cells were reconstituted into a single unit and maintained in a nutrient medium bath until required experimentally. Our objective was to use the epidermis as a relay for the induction of an electric current to the neurons following the topical application of capsaicin on the skin epidermis of the skin explant, an agonist of the TRPV1 channel implicated in pruritus and pain. After 10-20 days of coculture to form the re-innervated skin model, we applied a solution of capsaicin directly on the epidermis of the skin explant (4 μm).

Tumor Necrosis Factor alpha induced hypoexcitability in rat muscle evidenced in a model of ion currents and action potential.

Sepsis and Tumor Necrosis Factor alpha (TNFα), a major pro-inflammatory mediator, have previously been shown to induce a decrease in the conductance of voltage-dependent sodium channels (NaV). Moreover, TNFα increased resting membrane potential, leading to hyperpolarization. NaV and resting potential are the two major factors of membrane excitability.

Alteration of muscle membrane excitability in sepsis: possible involvement of ciliary nervous trophic factor (CNTF).

One of the main factor involved neuromyopathy acquired in intensive care unit (ICU) appears to be sepsis. It induces the release of many pro- and anti-inflammatory factors which can directly modulate the muscle excitability. We have studied the effects of one of them: the ciliary nervous trophic factor (CNTF) which is a cytokine released in the early phase of sepsis.

Effect of human skin explants on the neurite growth of the PC12 cell line.

The skin is a densely innervated organ. After a traumatic injury, such as an amputation, burn or skin graft, nerve growth and the recovery of sensitivity take a long time and are often incomplete. The roles played by growth factors and the process of neuronal growth are crucial.

Effect of okadaic acid on cultured clam heart cells: involvement of MAPkinase pathways.

Okadaic acid (OA) is one of the main diarrhetic shellfish poisoning toxins and a potent inhibitor of protein phosphatases 1 and 2A. The downstream signal transduction pathways following the protein phosphatase inhibition are still unknown and the results of most of the previous studies are often conflicting. The aim of the present study was to evaluate the effects of OA on heart clam cells and to analyse its possible mechanisms of action by investigating the signal transduction pathways involved in OA cytotoxicity.

Tumor necrosis factor-α downregulates sodium current in skeletal muscle by protein kinase C activation: involvement in critical illness polyneuromyopathy.

Sepsis is involved in the decrease of membrane excitability of skeletal muscle, leading to polyneuromyopathy. This effect is mediated by alterations of the properties of voltage-gated sodium channels (Na(V)), but the exact mechanism is still unknown. The aim of the present study was to check whether tumor necrosis factor (TNF-α), a cytokine released during sepsis, exerts a rapid effect on Na(V).

TNFα increases resting potential in isolated fibres from rat peroneus longus by a PKC mediated mechanism: involvement in ICU acquired polyneuromyopathy.

Background And Aims: Our aim was to investigate the effect of TNFα on muscle resting potential (RP) and then in muscle excitability and to demonstrate another mechanism implicated in intensive care units (ICU) acquired polyneuromyopathy.

Methods: Experiments were carried out on adult female Wistar rats. After isolation of muscle fibres from peroneus longus, influence of TNFα was tested on RP by using intracellular microelectrodes.

Na v1.4 and Na v1.5 are modulated differently during muscle immobilization and contractile phenotype conversion.

Muscle immobilization leads to modification in its fast/slow contractile phenotype. Since the properties of voltage-gated sodium channels (Na(v)) are different between "fast" and "slow" muscles, we studied the effects of immobilization on the contractile properties and the Na(v) of rat peroneus longus (PL). The distal tendon of PL was cut and fixed to the adjacent bone at neutral muscle length.

Annexin A5 increases the cell surface expression and the chloride channel function of the DeltaF508-cystic fibrosis transmembrane regulator.

Cystic fibrosis (CF) is caused by a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. In CF, the most common mutant DeltaF508-CFTR is misfolded, is retained in the ER and is rapidly degraded. If conditions could allow DeltaF508-CFTR to reach and to stabilize in the plasma membrane, it could partially correct the CF defect.

Effects of chronic sepsis on contractile properties of fast twitch muscle in an experimental model of critical illness neuromyopathy in the rat.

Objective: Critical illness polyneuromyopathy has been extensively studied in various animal models regarding electrophysiological aspects or molecular mechanisms involved in its physiopathology; however, little data are available on its main clinical feature, that is, muscular weakness. We have studied the effects of chronic sepsis in rats with special consideration to contractile and neuromuscular blockade properties in relation with the level of messenger RNA (mRNA) coding for ryanodine and acetylcholine receptors.

Design: This was an experimental animal study.

Effects of chronic sepsis on rat motor units: experimental study of critical illness polyneuromyopathy.

Critical illness polyneuromyopathy (CIP) leads to major muscle weakness correlated with peripheral nerve and/or muscle alterations. Because sepsis seems to be the main factor, we used an experimental model of chronic sepsis in rats to study the localization of the first alterations on isolated motor units of soleus muscle. Seven days of chronic sepsis leads to a decrease in muscle force and an increase in muscle fatigability.

Effects of immobilizing a single muscle on the morphology and the activation of its muscle fibers.

A single muscle of Wistar female rats, either soleus or peroneus longus, was immobilized by fixing its cut distal tendon to the bone during 8 weeks. We observed a transitory weight loss in both muscles; the mean fiber cross-sectional area (CSA) showed a reduction at day 30, followed by an increase at day 60. The time course of the activation of the immobilized muscle was evaluated by recording the chronic electromyographic (EMG) activity during short periods (1 min every other day) of treadmill locomotion.