Malignant hyperthermia (MH) is a rare but severe reaction that can occur in the operating room. Due to the low volume of these reactions, nurses are often unprepared to handle the event; however, not recognizing the event and intervening can lead to the death of the patient. This is a practice problem that can be addressed through a nursing staff education simulation training program. The purpose for this doctoral project was to develop a multidisciplinary MH simulation program that could improve nursing knowledge when caring for patients experiencing an MH crisis in the operating room. The practice-focused question for this project asked whether MH multidisciplinary simulation education improves the knowledge of nurses in the operating room setting. Utilizing Kolb’s theory of experiential learning, nurses were developed through the four stages of learning. Sources of evidence for this project included a review of the literature. Data were also collected pre- and post-intervention on the reliability of simulation training to improve operating room nurses’ knowledge of caring for the patient experiencing an MH crisis. Descriptive statistics via percent difference evaluated pre- and post-test evaluations. Results revealed a 16.4% increase knowledge scores from pretest to posttest following participation in the MH simulation. Improving patient outcomes creates significant social impact by developing community confidence in the surgical care provided by local hospitals.

The present study was performed to determine if pigs varying in their susceptibility to stress, adapted to a casein-based diet, experience an improvement in biochemical parameters related to stress and behaviour compared to pigs adapted to the traditional western canadian cereal-based swine diet. Experiment 1 involved separating fifty-eight, 8-week old pigs according to genotype with respect to the halothane gene. Within each genotype pigs were divided into 2 groups and assigned to either a control diet or to a diet where most of the protein source was substituted for casein. All animals were adapted to diet for 6 weeks and experienced a weekly blood sampling stressor. Day 1, 14 and 35 of the plasma samples were analyzed for glucose, cortisol, ACTH, insulin, pyridoxal 5$ sp prime$-phosphate (PLP), amino acid concentrations and dopamine-$ beta$-hydroxylase (DBH) activity; metabolic indices known to be responsive to stress. Experiment 2 involved separating fifty-seven, 14-week old pigs in the same manner, then adapting the pigs to their respective diets for a period of 4 weeks. Afterwards, pigs were transferred from their pen to a novel pen-maze situation where they had their behaviour monitored for a period of one hour. Results of these experiments have revealed that (1) the stress susceptible and carrier pigs experienced reduced day 35 plasma glucose, PLP concentrations and DBH activity compared to normal pigs; (2) dietary adaptation to the casein diet resulted in greater day 14 and 35 PLP levels and day 35 essential amino acid lysine, threonine, methionine, tryptophan and arginine concentrations compared to control-adapted pigs; (3) the carrier pigs investigated their surroundings more frequently than the stress susceptible pigs, and the normal pigs engaged in the through-maze behaviour more often than the stress susceptible pigs; and (4) adaptation to the casein diet, compared to the control diet, resulted in fewer displacement-type behaviours such as drinking

Malignant hyperthermia is a potentially fatal pharmacological disorder and is triggered by volatile anaesthetics in predisposed individuals. Mutations in the RYR1 gene, encoding the skeletal muscle calcium receptor channel have been linked to MH susceptibility. Over 200 point mutations have been have been found to date in the RYR1 gene linked to MHS worldwide. EBV-immortalization is regularly used worldwide as an effective procedure for inducing long-term growth of human B lymphocytes. In the current study, it was observed that immortalized lymphocytes from MHS patients heterozygous for the missense mutation H4833Y when initially cultured expressed both wild type and mutant allele but after a few weeks of culture they seemed to lose the mutant allele. High resolution melting assays and hybridization probe assays showed the loss of heterozygosity and this was confirmed using DNA sequencing. Genotyping and haplotype analysis using three intragenic RFLPs and two (CA)n repeat microsatellite markers tightly linked to the RYR1 gene showed a definite change in the haplotype, suggesting more widespread changes in the genome upon short-term culture of EBV-immortalized B-lymphocytes

Malignant hyperthermia (MH) is a rare pharmacogenetic disorder in humans induced by volatile anaesthetics and depolarising muscle relaxants. An MH reaction shows abnormal calcium homeostasis in skeletal muscle leading to a hypermetabolic state and increased muscle contracture. A mutation within the skeletal muscle calcium release channel ryanodine receptor gene (RYR1) is associated with MH and is thought to cause functional defects in the RYR1 channel leading to abnormal calcium release to the sarcoplasm and consequent MH reactions. Mutations within RYR1 are also associated with a rare congenital myopathy, central core disease (CCD). CCD is characterised by muscle weakness and is thought to be caused by insufficient calcium release from the RYR1 channel during excitation-contraction (EC) coupling. To investigate functional effects of RYR1 mutations, the entire coding region of human RYR1 was assembled and cloned into an expression vector. Mutant clones containing RYR1 mutations linked to MH or CCD were also constructed. Wild-type (WT) and mutant RYR1 clones were used for transient transfection of HEK-293 cells. Western blotting was performed after harvesting and expressed WT and mutant RYR1 proteins were successfully detected. Immunofluorescence showed co-localisation of RYR1 proteins and the endoplasmic reticulum in HEK-293 cells. [3H]ryanodine binding assays showed that RYR1 mutants linked to MH were more sensitive to the agonist 4-chloro-m-cresol (4-CmC) and less sensitive to the antagonist Mg2+ compared with WT. Two C-terminal RYR1 mutants T4826I and H4833Y were very significantly hypersensitive to 4-CmC and they may also result in a leaky channel. This hypersensitivity of mutants linked to MH may result in abnormal calcium release through the RYR1 channel induced by triggering agents leading to MH reactions. RYR1 mutants linked to CCD showed no response to 4-CmC showing their hyposensitive characteristics to agonists. This study showed that the human RYR1 proteins could be expressed in HEK-293 cells. Moreover, using the recombinant human RYR1 clone, a single mutation within RYR1 resulted in a functional defect in expressed RYR1 proteins and functions of mutant RYR1 proteins varied from hypersensitive to hyposensitive depending on the mutation and whether it was linked to MH or CCD.

No description available.

Steady advancements in diagnostics over the past century have propelled the world of medicine into the more advanced era of preventative medicine, an era with a resoundingly clear message: early detection can save lives. For patients who suffer from either pancreatic cancer or malignant hyperthermia susceptibility, early or preoperative diagnosis, respectively can save lives and minimize morbidity and mortality, in addition to offering cost-savings to hospitals and healthcare systems. Fortunately, significant progress have been made in the fields of metabolomics and biomarker identification. Given the benefits carried by serum biomarkers as targets of screening and diagnostic tool development, we applied functional nucleic acid technology and in vitro selection directly in whole human serum to search for disease-specific biomarkers and associated detection probes without a priori knowledge of the biomarkers pursued. This endeavour simultaneously serves as a proof-of-concept study to establish whether in vitro selection can be successfully performed in human serum. We specifically focused on the derivation of RNA-cleaving DNAzymes (RCD) through in vitro selection, or SELEX (systemic evolution of ligands through exponential exposure). DNAzymes constructed with a fluorogenic signalling molecule were incubated with human serum with the goal of identification of a functional nucleic acid probe capable of detecting the presence of a disease-specific biomarker. Two independent protocols have been designed and executed for the identification of DNAzyme sequences capable of detecting pancreatic cancer and malignant hyperthermia susceptibility, respectively. The first exploration was performed in serum obtained from cancer patients, with the goal of identifying DNAzymes capable of distinguishing pancreatic cancer from other cancer types. To do so, we employed in vitro selection, Next-Generation Sequencing, and bioinformatic analysis. We successfully demonstrated the feasibility of performing in vitro selection with DNAzymes in human serum, evidenced by distinct round-to-round enrichment of a DNA library towards the identification of DNAzymes capable of detecting pancreatic cancer. Additionally, we isolated two DNAzymes capable of distinguishing pancreatic cancer serum from healthy patient serum in fresh collected serum samples. Based on the positive results gathered in the pancreatic cancer in vitro selection project, we subsequently endeavoured to replicate the demonstrated feasibility of performing in vitro selection in human serum. By selecting malignant hyperthermia as the pathology investigated, we simultaneously sought to diversify the scope of DNAzyme detection by establishing whether successful DNAzyme selection can be achieved in a non-acute disease state. Thus, the second exploration was performed in serum obtained from patients who underwent evaluation for malignant hyperthermia susceptibility using the gold-standard caffeine-halothane contracture test. The goal of this project rested on the identification of DNAzymes capable of distinguishing malignant hyperthermia susceptibility in serum and approximating the performance of the gold standard test. We successfully isolated four DNAzyme candidates which demonstrated clinically relevant thresholds of sensitivity and specificity following thorough sensitivity and specificity analysis. In doing so, we once again demonstrated the ability to perform in vitro selection in human serum. Given the complexity of molecular interactions observed over the course of two in vitro selection protocols in human serum, it became clear that distinguishing meaningful target-mediated interactions from non-specific interactions would require advanced bioinformatic analysis. Consequently, using principles of computational biology, we performed a deep exploration of Next-Generation Sequencing results obtained from sequencing our recovered DNA libraries to extract additional data that would inform on the next required steps required to identify a DNAzyme specific for the pathology pursued. In doing so, we identified a two-step method to evaluate the progress of the in vitro selection protocol undertaken, and offered a systematic approach for choosing candidate sequences to undergo further testing based on promising performance in silico. Using this approach, we successfully identified a DNAzyme sequence capable of acting as a general cancer detection probe, with promising potential for diagnostic application. Ultimately, this thesis serves as a feasibility study of a novel approach to both in vitro selection and biomarker identification technique by combining the latest nanotechnology techniques with clinical data and real patient serum samples, and advanced computational biology tools. Despite the inability to identify a highly sensitive and specific DNAzyme capable of advancing towards biosensor construction, several important strides and lessons have been acknowledged, establishing the feasibility of performing in vitro selection in human serum, and outlining strategies for addressing and anticipating challenges with this technique. The hope is for this work to inspire and inform future efforts to apply functional nucleic acid technology to solve current gaps in both the diagnostic and therapeutic branches of medicine, and with the help of computational biology continue to bridge the gap between basic science and clinical medicine. / Dissertation / Doctor of Philosophy (PhD)

by Yuen Wai Fan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 211-232). / Abstracts in English and Chinese. / Acknowledgements --- p.i / List of Publications and Abstracts --- p.ii / Abbreviations --- p.iv / Abstract --- p.xi / Abstract in Chinese --- p.xiv / List of Figures --- p.xvii / List of Tables --- p.xxiii / Contents --- p.xxiv / Chapter Chapter 1. --- General Introduction --- p.1 / Chapter 1.1 --- Hyperthermia --- p.2 / Chapter 1.1.1 --- History of Hyperthermia --- p.2 / Chapter 1.1.2 --- Biological Functions of Hyperthermia --- p.3 / Chapter 1.1.3 --- Clinical Application of Hyperthermia --- p.4 / Chapter 1.1.3.1 --- Whole-body Hyperthermia --- p.4 / Chapter 1.1.3.2 --- Regional Hyperthermia --- p.4 / Chapter 1.1.3.3 --- Local Hyperthermia --- p.5 / Chapter 1.1.4 --- Combination Therapy --- p.5 / Chapter 1.1.4.1 --- Combined treatment with Hyperthermia and Radiotherapy --- p.6 / Chapter 1.1.4.2 --- Combined treatment with Hyperthermia and Chemotherapy --- p.6 / Chapter 1.2 --- Tumour Necrosis Factor --- p.9 / Chapter 1.2.1 --- History of Tumour Necrosis Factor --- p.9 / Chapter 1.2.2 --- Sources of TNF-α and TNF-β --- p.9 / Chapter 1.2.3 --- Biological Roles of TNF --- p.10 / Chapter 1.2.3.1 --- Receptors of TNF-α --- p.11 / Chapter 1.2.4 --- Signaling Pathway of TNF --- p.12 / Chapter 1.2.4.1 --- Activation of Death Domain --- p.12 / Chapter 1.2.4.2 --- Activation of Sphingomyelin Pathway --- p.13 / Chapter 1.2.4.3 --- Activation of NF-kB pathway --- p.13 / Chapter 1.3 --- Types of Cell Death: Necrosis and Apoptosis --- p.16 / Chapter 1.3.1 --- Necrosis --- p.16 / Chapter 1.3.2 --- Apoptosis --- p.16 / Chapter 1.4 --- Signaling Pathway in Apoptosis --- p.19 / Chapter 1.4.1 --- Factors Involved in Apoptotic Pathway --- p.19 / Chapter 1.4.1.1 --- Caspases --- p.19 / Chapter 1.4.1.2 --- Death Substrates --- p.20 / Chapter 1.4.1.3 --- Bcl-2 Protein Family --- p.21 / Chapter 1.4.1.4 --- Role of Mitochondria --- p.23 / Chapter 1.5 --- Objectives of the Project --- p.26 / Chapter Chapter 2. --- Materials and Methods --- p.28 / Chapter 2.1 --- Materials --- p.29 / Chapter 2.1.1 --- Culture of Cells --- p.34 / Chapter 2.1.1.1 --- "TNF-α Sensitive Cell Line, L929" --- p.34 / Chapter 2.1.1.2 --- "TNF-α Resistance Cell Line, L929-11E" --- p.34 / Chapter 2.1.1.3 --- Preservation of Cells --- p.35 / Chapter 2.1.2 --- Culture Media --- p.36 / Chapter 2.1.2.1 --- RPMI 1640 (Phenol Red Medium) --- p.36 / Chapter 2.1.2.2 --- RPMI 1640 (Phenol Red-Free Medium) --- p.36 / Chapter 2.1.3 --- Buffers and Reagents --- p.37 / Chapter 2.1.3.1 --- Preparation of Buffers --- p.37 / Chapter 2.1.3.2 --- Buffer for Common Use --- p.37 / Chapter 2.1.3.3 --- Reagents for Annexin-V-FITC/PI assay --- p.37 / Chapter 2.1.3.4 --- Reagents for Cytotoxicity Assay --- p.37 / Chapter 2.1.3.5 --- Reagents for Molecular Biology Work --- p.38 / Chapter 2.1.3.6 --- Reagents for Western Blotting Analysis --- p.38 / Chapter 2.1.4 --- Chemicals --- p.40 / Chapter 2.1.4.1 --- Recombinant Murine TNF-α --- p.40 / Chapter 2.1.4.2 --- Dye for Cytotoxicity Assay --- p.41 / Chapter 2.1.4.3 --- Fluorescence Dyes --- p.41 / Chapter 2.1.4.4 --- Chemicals Related to Mitochondrial Studies --- p.41 / Chapter 2.1.4.5 --- Inhibitors of Caspases --- p.42 / Chapter 2.1.4.6 --- Antibodies for Western Blotting --- p.42 / Chapter 2.1.4.7 --- Other Chemicals --- p.43 / Chapter 2.2 --- Methods --- p.44 / Chapter 2.2.1 --- Treatment with TNF-α --- p.44 / Chapter 2.2.2 --- Treatment with Hyperthermia --- p.44 / Chapter 2.2.3 --- In vitro Cell Cytotoxicity Assay --- p.45 / Chapter 2.2.4 --- Flow Cytometry --- p.46 / Chapter 2.2.4.1 --- Introduction --- p.46 / Chapter 2.2.4.2 --- Analysis by FCM --- p.48 / Chapter 2.2.4.3 --- Determination of Apoptotic and Late Apoptotic/Necrotic Cells with Annexin-V-FITC/PI Cytometric Analysis --- p.50 / Chapter 2.2.4.4 --- Determination of Mitochondrial Membrane Potential (ΔΨm) --- p.51 / Chapter 2.2.4.5 --- Determination of Hydrogen Peroxide (H202) Release --- p.52 / Chapter 2.2.4.6 --- Determination of Intracellular Free Calcium ([Ca2+]i) Level --- p.52 / Chapter 2.2.4.7 --- Determination of the Relationship of ΔΨm and [Ca2+]i Level --- p.53 / Chapter 2.2.5 --- Western Blotting Analysis --- p.53 / Chapter 2.2.5.1 --- Preparation of Proteins from Cells --- p.53 / Chapter 2.2.5.2 --- SDS Polyacrylamide Gel Electophoresis (SDS- PAGE) --- p.56 / Chapter 2.2.5.3 --- Electroblotting of Proteins --- p.57 / Chapter 2.2.5.4 --- Probing Antibodies for Proteins --- p.57 / Chapter 2.2.5.5 --- Enhanced Chemiluminescence (ECL) assay --- p.58 / Chapter 2.2.6 --- Reverse Transcriptase Polymerase Chain Reaction --- p.58 / Chapter 2.2.6.1 --- Extraction of RNA by Trizol Reagent --- p.59 / Chapter 2.2.6.2 --- Determination of the Amount of RNA --- p.60 / Chapter 2.2.6.3 --- Agarose Gel Electrophoresis --- p.60 / Chapter 2.2.6.4 --- Reverse Transcription --- p.63 / Chapter 2.2.6.5 --- Polymerase Chain Reaction (PCR) --- p.63 / Chapter 2.2.6.6 --- Design of Primers for Different Genes --- p.64 / Chapter 2.2.6.7 --- Determination of the Number of Cycles in PCR for Different Genes --- p.67 / Chapter 2.2.7 --- Caspase Fluorescent Assay --- p.67 / Chapter 2.2.7.1 --- Caspase-3 or ´ؤ8 Assay --- p.67 / Chapter Chapter 3. --- Results --- p.59 / Chapter 3.1 --- Studies of the Characteristics of L929 and L929-11E cells --- p.70 / Chapter 3.1.1 --- Determination of the Growth Curve of L929 and L929-11E Cells --- p.70 / Chapter 3.2 --- Studies on the Effect of TNF-α on L929 and L929-11E Cells --- p.73 / Chapter 3.2.1 --- TNF-α Induced Cell Death in L929 Cells but not in L929- 11E Cells --- p.73 / Chapter 3.2.2 --- TNF-α Induced Apoptosis in a Time-dependent Manner in L929Cells but not in L929-11E Cells --- p.80 / Chapter 3.2.3 --- TNF-α Induced Mitochondrial Membrane Depolarization in a Time-dependent Manner in L929 Cells but notin L929-11E Cells --- p.87 / Chapter 3.2.4 --- TNF-α Induced Cytochrome c Release in a Time- dependent Manner in L929 Cells but not in L929-11E Cells --- p.92 / Chapter 3.3 --- Effect of Hyperthermia on L929 and L929-11E Cells --- p.96 / Chapter 3.3.1 --- Introduction --- p.95 / Chapter 3.3.2 --- Hyperthermia Induced Apoptosis in L929 and L929-11E Cells --- p.96 / Chapter 3.3.3 --- Effect of Hyperthermia on Mitochondrial Membrane Depolarization --- p.100 / Chapter 3.3.4 --- Hyperthermia Induced Cyto c Release in a Time-dependent Manner in L929 and L929-11E Cells --- p.105 / Chapter 3.4 --- Relationship of Hyperthermia and TNF-α with PTP in L929 Cells --- p.107 / Chapter 3.5 --- Effect of TNF-α and Hyperthermia on the Level of Hydrogen Peroxide (H202) in L929 and L929-11E Cells --- p.114 / Chapter 3.5.1 --- Introduction --- p.114 / Chapter 3.5.2 --- TNF-α Enhanced the Level of H202 in L929 cells but not in L929-11E Cells --- p.115 / Chapter 3.5.3 --- Hyperthermia Enhanced the Level of H202 in L929 and L929-11E cells --- p.117 / Chapter 3.6 --- Effect of TNF-α and Hyperthermia on the Level of Intracellular Calcium in L929 and L929-11E Cells --- p.122 / Chapter 3.6.1 --- Increase in the Intracellular Calcium Level Induced by TNF-α Was Related to the Mitochondrial Membrane Depolarization in L929 Cells but not in L929-11E Cells --- p.122 / Chapter 3.6.2 --- Hyperthermia Increased the Level of [Ca2+]i in L929 and L929-11E Cells in a Time-dependent Manner --- p.124 / Chapter 3.7 --- Effect of Combined Hyperthermia and TNF-α Treatment on the Induction of Apoptosis in L929 and L929-1 1E Cells --- p.129 / Chapter 3.7.1 --- Combined Treatment with Hyperthermia and TNF- α Induced Apoptosis in Both L929 and L929-11E cells --- p.129 / Chapter 3.7.2 --- Hyperthermia and Its Combined Treatment with TNF-α Induced Mitochondrial Membrane Depolarization in L929 and L929-11E Cells --- p.135 / Chapter 3.8 --- Investigation of the Downstream Apoptotic Pathway in L929 and L929-11E Cells Upon Hyperthermia and TNF-a treatment --- p.142 / Chapter 3.8.1 --- Introduction --- p.142 / Chapter 3.8.2 --- Effect ofTNF-α and Hyperthermia on p53 Expression --- p.142 / Chapter 3.8.3 --- Effect of Hyperthermia and TNF-α on PARP --- p.146 / Chapter 3.8.4 --- Effect of Hyperthermia and TNF-α on Caspase-3 Activity --- p.149 / Chapter 3.8.5 --- Effect of Hyperthermia and TNF-α on Bid protein --- p.158 / Chapter 3.8.6 --- Effect of Hyperthermia and TNF-α on Caspase-8 Activity --- p.165 / Chapter 3.8.7 --- Effect ofTNF-α on TNFR1 Expression --- p.169 / Chapter Chapter 4. --- Discussion / Chapter 4.1 --- TNF-α Induced Apoptosis and Changed the Mitochondrial Activities in L929 Cells --- p.176 / Chapter 4.2 --- L929-11E cells Possessed Resistance Towards TNF-α --- p.187 / Chapter 4.3 --- Hyperthermia Triggered Apoptosis and Changed Mitochondrial Activities in L929 and L929-11E cells --- p.190 / Chapter 4.4 --- Combined hyperthermia and TNF-α treatment induced cell death and changed mitochondria activities in L929 and L929-11E cells --- p.195 / Chapter 4.5 --- Reversal of the TNF-α resistance and Enhancement of Sensitivity Towards Hyperthermia in L929-11E cells --- p.197 / Chapter 4.6 --- Proposed Pathway in the TNF-α- and Hyperthermia-mediated Apoptosis --- p.200 / Chapter 4.7 --- Application of TNF-α and Hyperthermia on Clinical Cancer Treatment --- p.203 / Chapter Chapter 5. --- Future Perspective of the Project --- p.206 / References --- p.210

Le canal cationique TRPV1 (Transient Receptor Potential Vanilloid 1) est activé par la capsaïcine, une acidose, de fortes températures ainsi que par les anesthésiques volatils (AV) dans les neurones sensoriels. Dans le muscle squelettique, TRPV1 est impliqué dans le métabolisme énergétique et l'exercice d'endurance. Grâce à des techniques d'immunomarquage et d'imagerie calcique, la première partie de la thèse vise à caractériser TRPV1 en tant que canal de fuite fonctionnel du réticulum sarcoplasmique (RS) dans les cellules musculaires squelettiques isolées de FDB (Flexor Digitorum Brevis) de souris. Par la suite, nous nous sommes intéressés à son rôle physiopathologique dans le muscle strié squelettique. Ainsi, dans une seconde partie nous supposons une implication de TRPV1 dans les crises d'hyperthermie maligne (HM) chez l'homme. Cette pathologie musculaire correspond à une crise de métabolisme exacerbé du muscle strié squelettique menant à une brusque montée en température chez le patient (>42°C) endormi au moyen d'AV. Dans cette deuxième étude nous démontrons, à travers une approche combinant imagerie calcique et outils pharmacologiques spécifiques du canal, que TRPV1 est activé lors de l'exposition des cellules musculaires à l'isoflurane. TRPV1 est donc une cible des AV dans la cellule musculaire. Puis, des variants de TRPV1 (T612M et N394del) de patients susceptibles à l'HM ont été découvertes. Nous avons pu montrer, suite à la transfection in vivo de ces variants dans des souris déficientes en TRPV1 et grâce à la mesure de flux calciques intracellulaires, que les variants humains de TRPV1 rendent ces canaux plus sensibles aux anesthésiques volatils que le canal TRPV1 humain sauvage. La troisième partie de la thèse a pour but de déterminer le rôle de TRPV1 dans le muscle squelettique en conditions physiologiques par des études fonctionnelles (fonction locomotrice, consommation d'oxygène) sur animal entier. Les résultats préliminaires de cette étude tendent à montrer que l'entraînement physique est moins efficace sur la fonction musculaire des souris déficientes en TRPV1. En conclusion, l'ensemble de ces résultats révèlent pour la première fois que TRPV1 est un canal calcique de fuite fonctionnel du RS pouvant faire le lien entre le déclenchement de l'HM au cours des anesthésies et la présence des RyR1 mutés dans le muscle squelettique / TRPV1 (Transient Receptor Potential Vanilloid 1) cation channel is activated by capsaicine, acidosis, high temperature and by volatile anaesthetics (VA) in sensory neurons. In skeletal muscle, TRPV1 appears to be implied in exercice endurance and energy metabolism. The present work aims first to characterize the functionality of this channel using immnostaining and calcium imaging. We report that TRPV1 is functionally expressed in isolated mouse skeletal muscle cells of FDB (Flexor Digitorum Brevis). These experiments point out that TRPV1 acts as a SR calcium leak channel. In contrast to earlier reports, our analysis shows that TRPV1 is only located to the sarcoplasmic reticulum (SR) membrane. Subsequently, we have studied its physiological role in skeletal muscle. Thus, in a second part, we suppose that TRPV1 could be involved in malignant hyperthermia (MH) crisis in human. MH is a muscular pathology linked to an abrupt increase in body temperature (> 42°C) in patients. MH crisis is a severe and feared complication of anesthesia. Nevertheless, any studies have demonstrated that RyR1 mutants are activated by VA. If the triggering agents of MH are known, their targets remain to be determined. By combining calcium imaging and pharmacological agents, our data first demonstrate that TRPV1 is activated by isoflurane in skeletal muscle cells. TRPV1 is so a target of volatile anaesthetics in skeletal muscle. Afterwards, TRPV1 mutants (T612M and N394del), obtained from susceptibles MH patients, were discovered. In the second part of the work, using in vivo transfection of TRPV1 mutants in TRPV1-/- mice and intracellular calcium measurements we have been able to demonstrate that human TRPV1 mutants are more sensitive to VA than human wild type TRPV1. The last part of the work investigates the physiological role of TRPV1 in skeletal muscle, using a functional exploration (locomotor function, oxygen consumption) in TRPV1-/- mice. Preliminary data point out that training seems to be less effective on skeletal muscle function of TRPV1-/- mice. To conclude, these results indicate for the first time that TRPV1 is a functional SR calcium leak channel and that TRPV1 may be the missing link between MH induction and RyR1 mutants in skeletal muscle during anesthesia

Les ions Ca2+ responsables de la contraction musculaire sont extrudés du réticulum sarcoplasmique (RS) via le récepteur de la ryanodine de type 1 (RyR1). Des mutations du gène de RyR1 sont responsables chez l’homme de l’hyperthermie maligne (HM) et de la myopathie à cores centraux (MCC). Nous avons caractérisé les altérations de l’efflux calcique du RS dues à de telles mutations dans la fibre musculaire de souris par électrophysiologie et imagerie confocale. L’expression des formes Y523S, R615C et R2163H de RyR1, associées à l’HM, provoque une hypersensibilité de l’efflux vis-à-vis du potentiel membranaire alors que les formes I4897T et G4896V associées à la MCC provoquent une réduction chronique de l’efflux sans modification de densité des RyR1 s ainsi que des protéines Cav1.1 et SERCA1. L’expression de la forme R4892W associée à la MCC ne modifie pas l’efflux calcique suggérant une plus faible pénétrance fonctionnelle de cette forme. Dans tous les cas, aucune indication de changement du contenu en calcium RS n’a été observée. Les résultats suggèrent que les modifications pathologiques de l’efflux calcique sont la conséquence directe de l’altération de fonction des canaux. Le deuxième objectif du travail s’est intéressé au rôle de certains phosphoinositides (PtdInsPs) dans la régulation de l’efflux calcique du RS. La surexpression de la PtdInsPs-phosphatase Mtm 1 n’a aucun effet sur l’efflux calcique alors que l’application intracellulaire de ses deux principaux substrats inhibe l’efflux, suggérant que leur accumulation dans les fibres musculaires déficientes en Mtm1 pourrait contribuer aux altérations pathologiques associées du couplage excitation-contraction / Ca2+ ions that trigger muscle contraction are released from the sarcoplasmic reticulum (SR) through the type 1 ryanodine receptor (RyR1) channel. Mutations of the gene encoding RyR1 are responsible for malignant hyperthermia (MH) and central core disease (CCD) in human. We characterized the alterations of SR Ca2+ release due to such mutations in mouse fibers using electrophysiology and confocal imaging. Expression of each of the MH-associated Y523S, R615C and R2163H mutant forms of RyR1 increases the sensitivity of Ca2+ release to membrane potential whereas forms I4897T and G4896V that are associated to CCD provoke a chronic depression of Ca2+ release with no concurrent alteration of RyR1, Cav1.1 and SERCA1 density. Expression of the CDD-associated R4892W form of RyR1 has no effect on Ca2+ release suggesting a weaker functional penetrance of this mutant form. In all cases we found no indication for a change in SR calcium content. Results suggest that pathological changes in Ca2+ release are the direct consequence of the functional alteration of the channels. The second goal of this work focused on the role of certain phosphoinositides (PtdInsPs) in the control of SR Ca2+ release. Over-expression of the PtdInsPs-phosphatase Mtm 1 does not affect Ca2+ release whereas intracellular application of its two main substrates inhibits Ca2+ release, suggesting that accumulation of these molecules in Mtm 1-deficient fibers could contribute to the associated alterations of excitation-contraction coupling