Functional analysis of RYR1 variants in patients with confirmed susceptibility to malignant hyperthermia.

Background: A major bottleneck to the introduction of noninvasive presymptomatic diagnostic tests for the pharmacogenetic disorder malignant hyperthermia is the lack of functional data for associated variants.

Methods: We screened 50 genes having a potential role in skeletal muscle calcium homeostasis using the HaloPlex™ (Agilent Technologies, Santa Clara, CA, USA) target enrichment system and next-generation sequencing. Twenty-one patients with a history of a clinical malignant hyperthermia reaction together with a positive in vitro contracture test were included.

Levobupivacaine plasma concentrations following repeat caudal anesthetics.

Aim: A single caudal anesthetic at the start of lower abdominal surgery is unlikely to provide prolonged analgesia. A second caudal at the end of the procedure extends the analgesia duration but total plasma concentrations may be associated with toxicity. Our aim was to measure total plasma levobupivacaine concentrations after repeat caudal anesthesia in infants and to generate a pharmacokinetic model for prediction of plasma concentrations after repeat caudal anesthesia in neonates, infants and children.

Junctional membrane Ca dynamics in human muscle fibers are altered by malignant hyperthermia causative RyR mutation.

We used the nanometer-wide tubules of the transverse tubular (t)-system of human skeletal muscle fibers as sensitive sensors for the quantitative monitoring of the Ca-handling properties in the narrow junctional cytoplasmic space sandwiched between the tubular membrane and the sarcoplasmic reticulum cisternae in single muscle fibers. The t-system sealed with a Ca-sensitive dye trapped in it is sensitive to changes in ryanodine receptor (RyR) Ca leak, the store operated calcium entry flux, plasma membrane Ca pump, and sodium-calcium exchanger activities, thus making the sealed t-system a nanodomain Ca sensor of Ca dynamics in the junctional space. The sensor was used to assess the basal Ca-handling properties of human muscle fibers obtained by needle biopsy from control subjects and from people with a malignant hyperthermia (MH) causative RyR variant.

Self-Organized Nanostructure Modified Microelectrode for Sensitive Electrochemical Glutamate Detection in Stem Cells-Derived Brain Organoids.

Neurons release neurotransmitters such as glutamate to communicate with each other and to coordinate brain functioning. As increased glutamate release is indicative of neuronal maturation and activity, a system that can measure glutamate levels over time within the same tissue and/or culture system is highly advantageous for neurodevelopmental investigation. To address such challenges, we develop for the first time a convenient method to realize functionalized borosilicate glass capillaries with nanostructured texture as an electrochemical biosensor to detect glutamate release from cerebral organoids generated from human embryonic stem cells (hESC) that mimic various brain regions.

Generation of Adrenal Chromaffin-like Cells from Human Pluripotent Stem Cells.

Adrenomedullary chromaffin cells are catecholamine (CA)-producing cells originating from trunk neural crest (NC) via sympathoadrenal progenitors (SAPs). We generated NC and SAPs from human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) in vitro via BMP2/FGF2 exposure, ascertained by qPCR and immunoexpression of SOX10, ASCL1, TFAP2α, and PHOX2B, and by fluorescence-activated cell sorting selection for p75NTR and GD2, and confirmed their trunk-like HOX gene expression. We showed that continuing BMP4 and curtailing FGF2 in vitro, augmented with corticosteroid mimetic, induced these cells to upregulate the chromaffin cell-specific marker PNMT and other CA synthesis and storage markers, and we demonstrated noradrenaline and adrenaline by Faglu and high-performance liquid chromatography.

Functional Characterization of C-terminal Ryanodine Receptor 1 Variants Associated with Central Core Disease or Malignant Hyperthermia.

Background: Central core disease and malignant hyperthermia are human disorders of skeletal muscle resulting from aberrant Ca2+ handling. Most malignant hyperthermia and central core disease cases are associated with amino acid changes in the type 1 ryanodine receptor (RyR1), the skeletal muscle Ca2+-release channel. Malignant hyperthermia exhibits a gain-of-function phenotype, and central core disease results from loss of channel function.

Comparative Plasma and Cerebrospinal Fluid Pharmacokinetics of Paracetamol After Intravenous and Oral Administration.

Background: We compared plasma and cerebrospinal fluid (CSF) pharmacokinetics of paracetamol after intravenous (IV) and oral administration to determine dosing regimens that optimize CSF concentrations.

Methods: Twenty-one adult patients were assigned randomly to 1 g IV, 1 g oral or 1.5 g oral paracetamol.

Peritumoural glutamate correlates with post-operative seizures in supratentorial gliomas.

To examine the impact of glutamate on post-operative seizures and survival in a cohort of patients with grade II to IV supratentorial glioma. A retrospective analysis was performed on 216 patients who underwent surgery for supratentorial gliomas. Primary explanatory variables were peritumoural and/or tumoural glutamate concentrations, glutamate transporter expression (EAAT2 and SXC).

Pharmacokinetics of levobupivacaine following infant spinal anesthesia.

Background: Infant spinal anesthesia with levobupivacaine has been promoted as a technique to reduce both the risk of postoperative apnea and exposure to volatile anesthesia. There is, however, no pharmacokinetic data to support the currently recommended doses.

Aims: Our aim was to determine whether infant levobupivacaine spinal anesthesia is associated with plasma concentrations consistent with a low risk of local anesthetic systemic toxicity.

The peroxisome proliferator activated receptor gamma agonist pioglitazone increases functional expression of the glutamate transporter excitatory amino acid transporter 2 (EAAT2) in human glioblastoma cells.

Glioma cells release glutamate through expression of system xc-, which exchanges intracellular glutamate for extracellular cysteine. Lack of the excitatory amino acid transporter 2 (EAAT2) expression maintains high extracellular glutamate levels in the glioma microenvironment, causing excitotoxicity to surrounding parenchyma. Not only does this contribute to the survival and proliferation of glioma cells, but is involved in the pathophysiology of tumour-associated epilepsy (TAE).

Absorption characteristics of epidural levobupivacaine with adrenaline and clonidine in children.

Aim: To determine if the addition of adrenaline, clonidine, or their combination altered the pharmacokinetic profile of levobupivacaine administered via the caudal epidural route in children.

Methods: Children aged <18 years old scheduled to undergo sub-umbilical surgery were administered caudal levobupivacaine plain 2.5 mg · ml(-1) or with adjuvants adrenaline 5 mcg · ml(-1) or clonidine 2 mcg · ml(-1) or their combination.

Glutamate is associated with a higher risk of seizures in patients with gliomas.

Objective: To investigate the relationship of glutamate and glutamate transporter expression in human gliomas and surrounding peritumoral brain to the presence of tumor-associated seizures (TAS).

Methods: We studied a retrospective (group 1: 190 patients) and then a prospective (group 2: 98 patients) cohort of patients who underwent a craniotomy for a supratentorial glioma. Tumor and peritumor tissue specimens were assayed for glutamate concentration and expression of glial glutamate transporters.

Automated responsiveness monitor to titrate propofol sedation.

Background: In previous studies, we showed that failure to respond to automated responsiveness monitor (ARM) precedes potentially serious sedation-related adversities associated with loss of responsiveness, and that the ARM was not susceptible to false-positive responses. It remains unknown, however, whether loss and return of response to the ARM occur at similar sedation levels. We hypothesized that loss and return of response to the ARM occur at similar sedation levels in individual subjects, independent of the propofol effect titration scheme.

N-acetylcysteine attenuates the decline in muscle Na+,K+-pump activity and delays fatigue during prolonged exercise in humans.

Reactive oxygen species (ROS) have been linked with both depressed Na(+),K(+)-pump activity and skeletal muscle fatigue. This study investigated N-acetylcysteine (NAC) effects on muscle Na(+),K(+)-pump activity and potassium (K(+)) regulation during prolonged, submaximal endurance exercise. Eight well-trained subjects participated in a double-blind, randomised, crossover design, receiving either NAC or saline (CON) intravenous infusion at 125 mg kg(-1) h(-1) for 15 min, then 25 mg kg(-1) h(-1) for 20 min prior to and throughout exercise.

Nitrous oxide and anesthetic requirement for loss of response to command during propofol anesthesia.

The blood concentration associated with loss of response (LOR) to command in 50% of subjects (CP50(LOR)) is an important measure of anesthetic potency. We therefore determined the CP50(LOR) in 40 healthy surgical patients, aged 18-60 yr old, receiving propofol alone or propofol with 67% nitrous oxide (N2O). Patients were randomized to receive 100% oxygen or 67% N2O in oxygen via facemask.

Pharmacokinetics of intravenous N-acetylcysteine in men at rest and during exercise.

Objective: We aimed to determine the pharmacokinetics (PK) of N-acetylcysteine (NAC) at rest and during exercise when given by continuous intravenous infusion intended to maintain relatively constant plasma concentrations.

Methods: Plasma concentrations of NAC were measured in 24 healthy male subjects during and after a two-stage intravenous infusion designed to provide constant NAC concentrations during cycling exercise, including intense exercise to fatigue.

Results: A three-compartment, open PK model was the best fit using population PK analysis with NONMEM.

Induction speed is not a determinant of propofol pharmacodynamics.

Background: Evidence suggests that the rate at which intravenous anesthetics are infused may influence their plasma-effect site equilibration. The authors used five different rates of propofol administration to test the hypothesis that different sedation endpoints occur at the same effect site propofol concentration, independent of the infusion rate. The authors concurrently evaluated the automated responsiveness monitor (ARM) against other sedation measures and the propofol effect site concentration.

Latency of pupillary reflex dilation during general anesthesia.

Areas of insensibility produced by neuraxial anesthesia or peripheral nerve blocks can be detected during general anesthesia by failure of noxious stimulation to trigger pupillary reflex dilation. We examined the latency of pupillary reflex dilation and the effect of fentanyl on the latency of reflex dilation during anesthesia in nine volunteers. We hypothesized that the reflex was generated by slowly conducting C nociceptive fibers and would be significantly delayed if a distal dermatome (L(4)) was stimulated compared with a proximal dermatome (C(5)).

Dantrolene reduces the threshold and gain for shivering.

Unlabelled: Dantrolene is used for treatment of life-threatening hyperthermia, yet its thermoregulatory effects are unknown. We tested the hypothesis that dantrolene reduces the threshold (triggering core temperature) and gain (incremental increase) of shivering. Healthy volunteers were evaluated on 2 random days: control and dantrolene (approximately 2.

Effects of intravenous N-acetylcysteine infusion on time to fatigue and potassium regulation during prolonged cycling exercise.

The production of reactive oxygen species in skeletal muscle is linked with muscle fatigue. This study investigated whether the antioxidant compound N-acetylcysteine (NAC) augments time to fatigue during prolonged, submaximal cycling exercise. Seven men completed a double-blind, crossover study, receiving NAC or placebo before and during cycling exercise, comprising 45 min at 70% of peak oxygen consumption (Vo2 peak) and then to fatigue at 90% Vo2 peak.

Dexmedetomidine and meperidine additively reduce the shivering threshold in humans.

Background And Purpose: Hypothermia might prove to be therapeutically beneficial in stroke victims; however, even mild hypothermia provokes vigorous shivering. Meperidine and dexmedetomidine each linearly reduce the shivering threshold (triggering core temperature) with minimal sedation. We tested the hypothesis that meperidine and dexmedetomidine synergistically reduce the shivering threshold without producing substantial sedation or respiratory depression.

Mild core hypothermia and anesthetic requirement for loss of responsiveness during propofol anesthesia for craniotomy.

Unlabelled: Mild hypothermia may be induced during neurosurgery for brain protection. However, its effect on propofol requirement has not been defined. Accordingly, we tested the hypothesis that 3 degrees C of core hypothermia decreases the propofol blood concentration at which patients respond to command (CP50-awake) in neurosurgical patients.