Malignant Hyperthermia Syndrome Research Articles

Clinical and morphological features of malignant hyperthermia: a rare case from practice

Malignant hyperthermia, is one of the most serious complications of modern anesthesia, which is a pharmacogenetic disease phenotypically manifested by skeletal muscle hypermetabolism and rhabdomyolysis during or after general anesthesia using inhalation anesthetics. An unexpected increase in CO2 concentration at the end of exhalation is the most common initial sign of malignant hyperthermia. Atypical forms of this pharmacogenetic disease are observed much more often than lightning or fulminant. In Russia, malignant hyperthermia currently remains a problem.
 We present a case of malignant hyperthermia in a 19-year-old girl who underwent surgery for nasal breathing disorders and received Sevoran anesthesia as support. The patient died 1 h 25 min after the surgery during withdrawal from anesthesia caused by a clinically confirmed syndrome of malignant hyperthermia. Forensic autopsy confirmed this diagnosis. The morphological changes in the skeletal muscles using both plain and elective histological stains were described.
 The presented observation is valuable owing to the rarity of lightning-fast forms of malignant hyperthermia and the high lethality accompanying these pathologies. This expert case demonstrate how a competent and comprehensive histological examination, including the use of genetic testing, allows correct formulation of a diagnosis and, if necessary, reasonably answer questions from law enforcement agencies.

Beneficial effects of dantrolene in the treatment of rhabdomyolysis as a potential late complication associated with COVID-19: a case report

BackgroundPatients with severe COVID-19 have disorders of the respiratory, cardiovascular, coagulation, skeletal muscle, and central nervous systems. These systemic failures may be associated with cytokine release syndrome, characterized by hyperpyrexia, thrombocytopenia, hyperferritinemia, and the elevation of other inflammatory markers. Rhabdomyolysis with high fever is a complication that is rarely found in COVID-19. The exact relations of these clinical conditions in patients with COVID-19 remain unknown.Case presentationWe present the case of a 36-year-old man with severe COVID-19 complicated by rhabdomyolysis and high fever. After admission, his condition continued to deteriorate, with a high body temperature. On day 9, the patient had elevated creatine kinase and myoglobin levels consistent with rhabdomyolysis (26,046 U/L and 3668 ng/mL, respectively). In addition to viral therapy, he was immediately treated with hydration. However, the patient had persistent fever and elevated creatine kinase levels. The patient was diagnosed with malignant hyperthermia as a late complication of COVID-19, although he had no hereditary predisposition to malignant hyperthermia or neuroleptic malignant syndrome. The administration of dantrolene with muscle relaxation and anti-inflammatory function showed potential efficacy for rhabdomyolysis, high fever, and increased plasma inflammatory markers.ConclusionsMalignant hyperthermia is triggered by not only anesthetic agents but also viral infections. A possible mechanism of malignant hyperthermia is hypersensitivity of calcium release from the sarcoplasmic reticulum. These include mutations in or the activation of the skeletal muscle ryanodine receptor calcium release channel. Dantrolene is a ryanodine receptor antagonist and is used as an anti-inflammatory agent. The administration of dantrolene showed potential efficacy for rhabdomyolysis, high body temperature due to inflammation, and increased inflammatory markers. The underlying mechanism of the association of rhabdomyolysis and high fever in COVID-19 might be similar to the pathogenesis of malignant hyperthermia.

Dantrolene Requires Mg2+ and ATP To Inhibit the Ryanodine Receptor.

Dantrolene is a ryanodine receptor (RyR) inhibitor, which is used to relax muscles in malignant hyperthermia syndrome. Although dantrolene binds to the RyR protein, its mechanism of action is unknown, mainly because of the controversial results showing that dantrolene inhibited Ca2+ release from intact fibers and sarcoplasmic reticulum (SR) vesicles, but failed to inhibit single RyR channel currents in bilayers. Accordingly, it was concluded that an important factor for dantrolene's action was lost during the purification procedure of RyR. Recently, Mg2+ was demonstrated to be the essential factor for dantrolene to inhibit Ca2+ release in skinned muscle fibers. The aim of the present study was to confirm these results in Ca2+ release and bilayer experiments, using SR vesicles and solubilized channels, respectively. Our Ca2+ release experiments demonstrated that the effect of dantrolene and Mg2+ was cooperative and that ATP enhanced the inhibiting effect of dantrolene. Namely, 10 µM dantrolene reduced RyR channel open probability by ∼50% in the presence of 3 mM free Mg2+ and 1 mM ATP, whereas channel activity further decreased to ∼20% of control when [ATP] was increased to 2 mM. Our data provide important complementary information that supports the direct, Mg2+-dependent mechanism of dantrolene's action and suggests that dantrolene also requires ATP to inhibit RyR.

Anomalous Kv 7 channel activity in human malignant hyperthermia syndrome unmasks a key role for H2 S and persulfidation in skeletal muscle.

Human malignant hyperthermia (MH) syndrome is induced by volatile anaesthetics and involves increased levels of cystathionine β-synthase (CBS)-derived H2 S within skeletal muscle. This increase contributes to skeletal muscle hypercontractility. Kv 7 channels, expressed in skeletal muscle, may be a molecular target for H2 S. Here, we have investigated the role of Kv 7 channels in MH. Skeletal muscle biopsies were obtained from MH-susceptible (MHS) and MH-negative (MHN) patients. Immunohistochemistry, RT-PCR, Western blot, and in vitro contracture test (IVCT) were carried out. Development and characterization of primary human skeletal muscle cells (PHSKMC) and evaluation of cell membrane potential were also performed. The persulfidation state of Kv 7 channels and polysulfide levels were measured. Kv 7 channels were similarly expressed in MHN and MHS biopsies. The IVCT revealed an anomalous contractility of MHS biopsies following exposure to the Kv 7 channel opener retigabine. Incubation of negative biopsies with NaHS, prior to retigabine addition, led to an MHS-like positive response. MHS-derived PHSKMC challenged with retigabine showed a paradoxical depolarizing effect, compared with the canonical hyperpolarizing effect. CBS expression and activity were increased in MHS biopsies, resulting in a major polysulfide bioavailability. Persulfidation of Kv 7.4 channels was significantly higher in MHS than in MHN biopsies. In skeletal muscle of MHS patients, CBS-derived H2 S induced persulfidation of Kv 7 channels. This post-translational modification switches the hyperpolarizing activity into depolarizing. This mechanism can contribute to the pathological skeletal muscle hypercontractility typical of MH syndrome. This article is part of a themed section on Hydrogen Sulfide in Biology & Medicine. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v177.4/issuetoc.

Severe hyponatremia in a patient with schizophrenia associated with prolonged consciousness disturbance

Hyponatremia presents with various central nervous system symptoms during its course and treatment. We treated a patient who presented with a prolonged consciousness disorder and was suspected of having complications of neuroleptic malignant syndrome and osmotic demyelination syndrome (ODS) during the treatment for his hyponatremia, which was caused by syndrome of inappropriate secretion of antidiuretic hormone (SIADH). The patient was a 30-year-old Japanese man who had been under treatment for schizophrenia. He presented with profound hyponatremia (96 mEq/L) and a consciousness disorder. Because he was taking a number of antipsychotic drugs and since psychogenic polydipsia was present along with laboratory findings, the patient was diagnosed with SIADH. However, the consciousness disorder reappeared after his serum sodium concentrations were normalized, and it persisted over a long period. Although ODS was suspected from the clinical course and imaging findings, there were several inconsistencies, such as the lack of quadriplegia. The patient also showed muscular rigidity and fever, and we, therefore, diagnosed complications of malignant hyperthermia syndrome caused by the discontinuation of all antipsychotic drugs at the time of onset. There have been no reports of complications of these two conditions, and we report this case for its clinically valuable information.

Molecular changes in mitochondrial respiratory activity and metabolic enzyme activity in muscle of four pig breeds with distinct metabolic types.

Skeletal muscles are metabolically active and have market value in meat-producing farm animals. A better understanding of biological pathways affecting energy metabolism in skeletal muscle could advance the science of skeletal muscle. In this study, comparative pathway-focused gene expression profiling in conjunction with muscle fiber typing were analyzed in skeletal muscles from Duroc, Pietrain, and Duroc-Pietrain crossbred pigs. Each breed type displayed a distinct muscle fiber-type composition. Mitochondrial respiratory activity and glycolytic and oxidative enzyme activities were comparable among genotypes, except for significantly lower complex I activity in Pietrain pigs homozygous-positive for malignant hyperthermia syndrome. At the transcriptional level, lactate dehydrogenase B showed breed specificity, with significantly lower expression in Pietrain pigs homozygous-positive for malignant hyperthermia syndrome. A similar mRNA expression pattern was shown for several subunits of oxidative phosphorylation complexes, including complex I, complex II, complex IV, and ATP synthase. Significant correlations were observed between mRNA expression of genes in focused pathways and enzyme activities in a breed-dependent manner. Moreover, expression patterns of pathway-focused genes were well correlated with muscle fiber-type composition. These results stress the importance of regulation of transcriptional rate of genes related to oxidative and glycolytic pathways in the metabolic capacity of muscle fibers. Overall, the results further the breed-specific understanding of the molecular basis of metabolic enzyme activities, which directly impact meat quality.

Muscle Transcriptional Profile Based on Muscle Fiber, Mitochondrial Respiratory Activity, and Metabolic Enzymes.

Skeletal muscle is a highly metabolically active tissue that both stores and consumes energy. Important biological pathways that affect energy metabolism and metabolic fiber type in muscle cells may be identified through transcriptomic profiling of the muscle, especially ante mortem. Here, gene expression was investigated in malignant hyperthermia syndrome (MHS)-negative Duroc and Pietrian (PiNN) pigs significantly differing for the muscle fiber types slow-twitch-oxidative fiber (STO) and fast-twitch-oxidative fiber (FTO) as well as mitochondrial activity (succinate-dependent state 3 respiration rate). Longissimus muscle samples were obtained 24 h before slaughter and profiled using cDNA microarrays. Differential gene expression between Duroc and PiNN muscle samples were associated with protein ubiquitination, stem cell pluripotency, amyloid processing, and 3-phosphoinositide biosynthesis and degradation pathways. In addition, weighted gene co-expression network analysis within both breeds identified several co-expression modules that were associated with the proportion of different fiber types, mitochondrial respiratory activity, and ATP metabolism. In particular, Duroc results revealed strong correlations between mitochondrion-associated co-expression modules and STO (r = 0.78), fast-twitch glycolytic fiber (r = -0.98), complex I (r=0.72) and COX activity (r = 0.86). Other pathways in the protein-kinase-activity enriched module were positively correlated with STO (r=0.93), while negatively correlated with FTO (r = -0.72). In contrast to PiNN, co-expression modules enriched in macromolecule catabolic process, actin cytoskeleton, and transcription activator activity were associated with fiber types, mitochondrial respiratory activity, and metabolic enzyme activities. Our results highlight the importance of mitochondria for the oxidative capacity of porcine muscle and for breed-dependent molecular pathways in muscle cell fibers.

A Review of the Factors Affecting the Incidence of Malignant Hyperthermia in the Greater Kansas City Area

Malignant Hyperthermia (MH) is a rare genetic disease. However, it is devastating when it occurs in a patient. MH is usually triggered by inhalational anesthetics and/or depolarizing muscle relaxants. Public awareness of MH has increased with the presentation of an episode on the television program, “House”, and the availability of web-based information. For over 20 years, the MH susceptible pig has been used in experiments by our group as an animal model for MH in humans. The incidence of Malignant Hyperthermia in the Greater Kansas City Area has declined dramatically since the introduction of Sevoflurane in 1992 as the anesthetic of choice (over 60% usage rate) in most surgical procedures. Historically, Malignant Hyperthermia was reported to occur at a rate of 1:50,000 during surgical procedures [1]. In the Greater Kansas City Area, Malignant Hyperthermia (MH) occurred at a rate of 1:53,636 during the 1965-1985 time period, as there were 38 MH cases in 35 patients [2]. During the past ten years (1996-2006), there were only 2 cases of MH, representing an incidence rate of 1:597,240. That decrease is an 11.13 fold (or 89%) decrease which is very significant. Despite the reduced incidence of Malignant Hyperthermia, two recent cases of MH that result in deaths in Wisconsin and Florida make it imperative that MH is recognized early and appropriate treatment initiated without delay. We have expanded our analysis of the futile cycle mechanism that underlies the MH syndrome. MH is equivalent to the rapid discharge of a battery by a short circuit.

Procalcitonin interest to assess a septic state inducing the death

In this prospective study, we evaluated the use of PCT when collecting the body which was carried out. The chosen cut-off was set at 10 ng/mL because at this level, the PCT was associated to a multiorgan failure attributable to a septic shock.For 90 cases, two groups were stratified by their final diagnosis: 33 of for non violent deaths and 57 of violent deaths. There was no significant elevation of procalcitonin rate (PCT) in the group of violent deaths. We noted 6 elevations of PCT rate above 10 ng/mL for non violent deaths (15.4%) and in 3 cases there wasan evidence for an infectious context (recent anti- infectious treatments, chemotherapy in progress).Control of CRP performed on blood samples found initial elevations above 10 mg/L in 3 of the 6 cases (including 2 of 3 cases associated with an infectious context). There is no evidence of PCT rate increase for intermediate PMI (post mortem interval), long PMI and undefined PMI. This study found a PPV (positive predictive value) and clinical specificity of 100% for a cut-off set at 10 ng/mL. By taking this threshold, no significant PCT increase was observed in presence of death cases related to a violent origin as well as a fatal multiorgan failure due to malignant hyperthermia syndrome induced by neuroleptic use. The PCT appears to remain stable over time and whatever the conservation conditions of the body.

Porcine stress syndrome (PSS) in mangalitsa pigs

Porcine stress syndrome (PSS) is one kind of molecular genetics defect which will cause malignant hyperthermia syndrome in pigs. It was reported that mutation of pig rynodine receptor (RYR1) gene is the main reason for PSS. The aim of this study was to test the RYR1 genotype of 10 Mangalitsa pigs using a polymerase chain reaction-restriction endonuclease fragment length polymorphism (PCR-RFLP) technique, which is a reliable and simple method for RYR1 gene testing. Extraction of DNA was done by using hair follicles. The results showed that the RYR1 genotype of all the 10 porcine cases were negative. These results suggested that Mangalitsa pig could be one of the porcine breeds selectively bred for medical and clinically experiments.

Continued progress in understanding the molecular genetics of malignant hyperthermia

A little over 50 years ago, Denborough and Lovell described the syndrome known today as malignant hyperthermia (MH). Little was known about this disorder at the time other than it carried a high fatality rate and was characterized by explosive hyperthermia in an otherwise apparently healthy individual undergoing general anesthesia. The unravelling of the principal features of the syndrome involved a combination of astute clinical observations, a fortuitous association with a similar syndrome in pigs, and assiduous laboratory investigations involving contributions from many countries. Seminal contributions to the understanding of MH were made by individuals associated with the University of Toronto, particularly Drs. Beverly Britt, Werner Kalow, Roderick Gordon, David MacLennan, and their many coworkers. In this issue of the Journal, Dr. MacLennan et al. continue to expand on earlier work in MH, particularly the molecular genetics of MH and the allied myopathy, Central Core Disease. Although the inheritance pattern of MH in humans was known by the 1980s, a turning point in the MH story occurred in 1990 when Dr. MacLennan’s team identified the mutation in the ryanodine receptor gene causal for MH in the swine model of MH. However, the molecular genetics of MH in humans has proven to be far more complex and obscure. This is due, in part, to the inherent complexity of the MH syndrome; to a variety of presentations that may be mimicked by several clinical situations; to a lack of typical phenotypic signs in the absence of anesthesia; to an association with several genes; and potentially, to scores of DNA variants that may lead to the pathophysiologic abnormality in MH, namely, calcium dysregulation in the skeletal muscle cell. Since MH may become manifest without warning and may progress rapidly to life-threatening hypercarbia, muscle breakdown, acidosis, and hyperthermia, much effort has been expended in attempting to identify those at risk for the syndrome. The mainstay diagnostic test for MH is the muscle biopsy contracture test first described by Drs. Britt and Kalow in the early 1970s. The test entails exposure of biopsied skeletal muscle to calcium-releasing agents, such as halothane, caffeine, ryanodine, and /or chloro-m-cresol. Since that time, the contracture test has served to clarify the inheritance of MH, the association with Central Core Disease, and multiple phenotypic presentations of the syndrome. Clearly, it is not applicable either to screening or to rapid identification of susceptibility. Furthermore, as with most laboratory tests, sensitivity and specificity are not 100%. Nevertheless, the test has served as the standard against which other tests are judged. One of the main current goals of research related to MH is the development of a minimally invasive, highly accurate diagnostic test for MH. Molecular genetics holds the promise of meeting that goal. In fact, clinical genetic testing for MH susceptibility is already available in many countries at the present time, but it requires careful patient selection because of the limited sensitivity of genetic testing. The road to the goal line of a sensitive and specific genetic test has proven to be replete with obstacles, just as it has been for many other inherited disorders. For instance, although the ryanodine receptor gene (RYR-1) and the ryanodine receptor or calcium release channel in the sarcoplasmic reticulum are most often associated with the syndrome, other calcium regulatory proteins, such as the dihydropyridine receptor and, more recently, calsequestrin, lead to intracellular calcium dysregulation and clinical MH H. Rosenberg, MD (&) Department of Medical Education and Clinical Research, Saint Barnabas Medical Center, Livingston, NJ, USA e-mail: hrosenberg@sbhcs.com

Influence of diets containing raw or extruded peas instead of soybean meal on meat quality characteristics in growing-finishing pigs

An experiment was conducted to evaluate the effect of pea-based diet fed to growing and finishing pigs on performance, carcass and meat quality. Thirty pigs (Slovak White Meaty or crossbred Slovak White Meaty × Pietrain) were tested for the malignant hyperthermia (MH) syndrome using a DNA based test. Pigs were allotted to control and experimental groups (of 10 pigs each, equal for normal – NN and he-terozygotes – Nn and equal for barrows and gilts) with 2 pigs per pen. Pigs receiving the control treatment were fed soybean meal diets. In all diets fed to experimental pigs the soybean meal was replaced by 30% of raw or extruded pea-based meal balanced on an isonitrogenous and isoenergetic level. Pig performance was monitored for the entire experimental period. At the conclusion of the experiment, carcass and meat quality were measured. The results did not show any effects of dietary treatments on average daily gain (P > 0.05). The evaluation of carcass composition showed no significant differences (P > 0.05) in backfat and lean percentage values between the control and experimental pigs. Chemical composition (total water, protein, intramuscular fat) and fatty acid profile did not differ among treatments (P > 0.05). The differences in the omega-6/omega-3 ratio were significant (P > 0.05) between animals fed the control ration with soybean meal and animals receiving the pea ration. No differences were observed between control and experimental pigs in pH (45 min and 24 h), colour (24 h), drip loss (24 h) and tenderness (5 day) measured with Warner-Bratzler instrument (P > 0.05). In conclusion, peas may replace the soybean meal in diets fed to growing and finishing pigs without negative influence on pig performance, carcass composition and meat quality.

Serotonin Syndrome with Severe Hyperthermia after Ingestion Of Tranylcypromine Combined with Serotonin Reuptake Inhibitors and Tyramine-Rich Food in a Case of Suicide

The monoamine oxidase inhibitor (MAO-I) tranylcypromine was introduced about 50 years ago. It has been used for a long time as a third-line antidepressant for treatment-resistant depression. The blood plasma half-life of tranylcypromine is relatively short (1.5–3 h), but its biological effects last considerably longer. The combination of MAO-I with drugs which enhance the activity of the serotonergic system can result in a severe serotonin syndrome [2] with malignant hyperthermia syndrome [1] [3].

Out of a Cell into This Darkened Space

Out of a Cell into This Darkened Space

Sevoflurane modulation of Ca2+ regulation in skeletal muscle sarcoplasmic reticulum vesicles from young and mature rabbits

Developmental differences in splice variants of the two key sarcoplasmic reticulum (SR) calcium regulatory proteins, ryanodine (RyR1), and sarcoendoplasmic reticulum calcium pump (SERCA1) have been linked to various neuromuscular disorders, but not malignant hyperthermia (MH). However, it is unclear whether an age-related difference in volatile anesthetic-mediated SR calcium function exists that could add to our current understanding of the clinical presentation of MH syndrome and provide insight into molecular mechanisms for general anesthesia that may have other physiologic and/or pathophysiologic significance. Therefore, the effects of sevoflurane on intracellular calcium regulation in isolated SR membrane vesicles from the skeletal muscle of healthy young rabbits were compared to their adult counterpart using an established in vitro model with the assumption that exposure to sevoflurane would elicit a weaker response in the young SR. Through dual wavelength spectroscopy of Ca(2+): Arsenazo III difference absorbance, the effects of sevoflurane on SR Ca(2+) uptake rate and release in heavy and light fraction SR membrane vesicles isolated from the white muscle of anesthetized, postweaned (age = 6 weeks, n = 5) and adult (age = 6 months, n = 5) male New Zealand rabbits were examined. The adult group showed a 50% increase in Ca(2+) uptake rate from control at both subclinical and clinically relevant anesthetic concentrations, whereas in the SR from the younger animals, Ca(2+) uptake rate was not altered by any concentration of sevoflurane. The sensitivity of both the low and high affinity Ca(2+)-binding sites on RyR1 was increased by sevoflurane to the same extent in the SR vesicles from the young and mature adult rabbits. Interestingly, a greater potency of sevoflurane for the high affinity-binding site was identified, and this was independent of age. These findings suggest that the sensitivity of the SR to sevoflurane-mediated Ca(2+) uptake may be increased with maturity, while an analogous developmental effect on RyR1 is less probable. Nonetheless, this study shows for the first time that a potent inhalational agent such as sevoflurane can influence the high affinity SR calcium-binding site by lowering the extraluminal concentration of calcium necessary to trigger calcium release. While this may not be of consequence when inhaled anesthetics are administered to normal children or adults, it may have life-threatening consequences in carriers of RyR1 mutations.

Maligne Hyperthermie und deren Differenzialdiagnosen

Hyperthermia affects almost all endogenous regulatory systems, where especially cardiovascular and central nervous system interactions can result in life threatening complications. This review illustrates signs and symptoms, pathophysiology and therapeutic options of the three most common hyperthermic syndromes in neurology: malignant hyperthermia, serotonine-syndrom and malignant neuroleptic syndrome. The aim of this contribution is to enable the reader to make the differential diagnosis of these three disease entities. Furthermore the association of other specific myopathies and hyperthermia syndromes is discussed.

Enhanced Excitation-Coupled Calcium Entry in Myotubes Expressing Malignant Hyperthermia Mutation R163C Is Attenuated by Dantrolene

Dantrolene is the drug of choice for the treatment of malignant hyperthermia (MH) and is also useful for treatment of spasticity or muscle spasms associated with several clinical conditions. The current study examines the mechanisms of dantrolene's action on skeletal muscle and shows that one of dantrolene's mechanisms of action is to block excitation-coupled calcium entry (ECCE) in both adult mouse flexor digitorum brevis fibers and primary myotubes. A second important new finding is that myotubes isolated from mice heterozygous and homozygous for the ryanodine receptor type 1 R163C MH susceptibility mutation show significantly enhanced ECCE rates that could be restored to those measured in wild-type cells after exposure to clinical concentrations of dantrolene. We propose that this gain of ECCE function is an important etiological component of MH susceptibility and possibly contributes to the fulminant MH episode. The inhibitory potency of dantrolene on ECCE found in wild-type and MH-susceptible muscle is consistent with the drug's clinical potency for reversing the MH syndrome and is incomplete as predicted by its efficacy as a muscle relaxant.

The Effects of Dantrolene on Hypoxic-Ischemic Injury in the Neonatal Rat Brain

The pathophysiology of brain damage from hypoxia or ischemia has been ascribed to various mechanisms and cascades. Intracellular calcium overload and a calcium excitotoxic cascade have been implicated. It has been suggested that disturbances of endoplasmic reticulum calcium homeostasis are involved in the induction of neuronal cell injury. Two types of intracellular Ca2+-release channels, involving the ryanodyne receptor and the inositol (1,4,5)-triphosphate receptor, are essential for Ca2+ signaling in cells. Dantrolene, which is used for the treatment of malignant hyperthermia syndrome, has been reported to inhibit Ca2+ release through ryanodyne receptors from the endoplasmic reticulum into the cytosol. We designed this study to investigate the neuroprotective effects of dantrolene on hypoxic-ischemic brain damage in the neonatal rat brain. Seven-day-old Sprague-Dawley rats were assigned into two groups; control group (n = 69) and dantrolene group (n = 60). Dimethyl sulfoxide was administered intracerebroventricularly in the control group, and dantrolene in dimethyl sulfoxide was similarly administered to the dantrolene group, before hypoxic-ischemic brain injury (HII). HII was induced by the ligation of the common carotid artery under isoflurane anesthesia, followed by exposure to about 2.5 h of hypoxia (oxygen concentration was maintained at 7%-8%). 1H magnetic resonance spectroscopy was performed 1 day after HII. This noninvasive method evaluated apoptotic processes in the brain after HII. Morphologic score analyses and the calculated percentage of infarct areas after 2,3,5-triphenyltetrazolium chloride staining 14 days after HII were also used to evaluate the effects of dantrolene on HII. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) staining was performed 1 day after HII using 24 more rats. The lipid/creatine ratios in the right hemispheres in the dantrolene group 1 day after HII were significantly lower than those of the control group (P < 0.05). There was no significant difference between the two groups in the N-acetylaspartate/creatine ratios. The gross morphologic scores were lower in the dantrolene group than in the control group (P < 0.05), and infarct area (%) after 2,3,5-triphenyltetrazolium chloride staining was less in the dantrolene group than in the control group (P < 0.05) 14 days after HII. Further work with 24 rats showed no significant difference, however, in the number of TUNEL positive cells on the two groups. Our results show that dantrolene, administered intracerebroventricularly before HII, had a neuroprotective effect in HII model of the neonatal rat brain.

Pharmacologic and Functional Characterization of Malignant Hyperthermia in the R163C RyR1 Knock-in Mouse

Malignant hyperthermia is a pharmacogenetic disorder affecting humans, dogs, pigs, and horses. In the majority of human cases and all cases in animals, malignant hyperthermia has been associated with missense mutations in the skeletal ryanodine receptor (RyR1). The authors used a "knock-in" targeting vector to create mice carrying the RyR1 R163C malignant hyperthermia mutation. Validation of this new mouse model of human malignant hyperthermia susceptibility includes (1) proof of transcription of the R163C allele and expression of ryanodine receptor protein in R163C heterozygous and R163C homozygous animals; (2) fulminant malignant hyperthermia episodes in R163C heterozygous mice after exposure to 1.25-1.75% halothane or an ambient temperature of 42 degrees C characterized by increased rectal temperature, respiratory rate, and inspiratory effort, with significant blood biochemical changes indicating metabolic acidosis, ending in death and hyperacute rigor mortis; (3) intraperitoneal pretreatment with dantrolene provided 100% protection from the halothane-triggered fulminant malignant hyperthermia episode; (4) significantly increased sensitivity (decreased effective concentration causing 50% of the maximal response) of R163C heterozygous and homozygous myotubes to caffeine, 4-chloro-m-cresol, and K-induced depolarization; (5) R163C heterozygous and homozygous myotubes have a significantly increased resting intracellular Ca concentration compared with wild type; (6) R163C heterozygous sarcoplasmic reticulum membranes have a twofold higher affinity (Kd = 35.4 nm) for [H]ryanodine binding compared with wild type (Kd = 80.1 nm) and a diminished inhibitory regulation by Mg. Heterozygous R163C mice represent a valid model for studying the mechanisms that cause the human malignant hyperthermia syndrome.

Influence of MHS genotype and feeding regime on allometric and temporal growth of pigs assessed by magnetic resonance imaging

Abstract A total of 68 barrows, 4-way-crosses with a Pietrain × Hampshire sire and a Large White × German Landrace dam were used in this study. The pigs were divided into 4 groups regarding the MHS (malignant hyperthermia syndrome) genotype (NN and Nn) and feeding regime (intensive and restrictive). The piglets were genotyped by DNA test; data on muscle and fat growth were obtained by repeated measurements of body composition at 4 weeks intervals by magnetic resonance imaging (MRI). Differential growth analysis showed that muscle tissue grew proportionally with the increase of live weight (allometric coefficient, b ≈ 1); fat grew faster in relation to live weight ( b > 1) in all investigated groups of pigs. Significant differences in growth coefficients for fat were found only between feeding groups. The analysis by asymmetric S-function showed different patterns of live weight growth of pigs from two feeding regimes. Within the feeding regimes, no significant differences in live weight growth patterns between the pigs of different MHS genotype (NN and Nn) were found. Muscle growth pattern significantly differed between the groups of investigated pigs: Nn pigs from the intensive feeding group were significantly superior to NN pigs in the same group and to Nn pigs fed restrictively ( p b -coefficient of the S-function). In this respect Nn pigs performed better under intensive feeding than under restrictive feeding regime, while no difference was found between NN pigs from two feeding regimes. By combining information on live weight and muscle growth, the optimal slaughter weight of pigs was calculated: 130 and 126 kg for intensively fed NN and Nn pigs, respectively, and about 114 kg for both genotypes from the restricted group of pigs. From fat growth analysis by asymmetric S-function, no influence of genotype on fat deposition in both feeding systems could be observed. Growth patterns of fat differed significantly only between the feeding groups. This study showed that the growth of body components fits a sigmoid curve and that the asymmetric S-function proved to be a more accurate and informative model than a simple allometric function, providing a base for important decisions in fattening of pigs. A practical consequence of this study is that the more cost-effective restrictive feeding regime can be recommended as more appropriate in fattening of pigs, since intensive feeding generally failed to improve their growth traits. Similarly, inclusion of MHS-gene did not enhance muscle growth characteristics of investigated pigs, so MHS-negative pigs (NN) can be considered as more desirable fatteners, especially when fed restrictively.