Kirk Hogan

Consensus statement: First International Workshop on Anesthetics and Alzheimer's disease.

In order to review the current status of the potential relationship between anesthesia and Alzheimer’s disease, a group of scientists recently met in Philadelphia for a full day of presentations and discussions. This special article represents a consensus view on the possible link between Alzheimer’s disease and anesthesia and the steps required to test this more definitively.

Folate regulation of axonal regeneration in the rodent central nervous system through DNA methylation

The folate pathway plays a crucial role in the regeneration and repair of the adult CNS after injury. Here, we have shown in rodents that such repair occurs at least in part through DNA methylation. In animals with combined spinal cord and sciatic nerve injury, folate-mediated CNS axon regeneration was found to depend on injury-related induction of the high-affinity folate receptor 1 (Folr1). The activity of folate was dependent on its activation by the enzyme dihydrofolate reductase (Dhfr) and a functional methylation cycle. The effect of folate on the regeneration of afferent spinal neurons was biphasic and dose dependent and correlated closely over its dose range with global and gene-specific DNA methylation and with expression of both the folate receptor Folr1 and the de novo DNA methyltransferases. These data implicate an epigenetic mechanism in CNS repair. Folic acid and possibly other nontoxic dietary methyl donors may therefore be useful in clinical interventions to promote brain and spinal cord healing. If indeed the benefit of folate is mediated by epigenetic mechanisms that promote endogenous axonal regeneration, this provides possible avenues for new pharmacologic approaches to treating CNS injuries.

The effect of TOMM40 poly-T length on gray matter volume and cognition in middle-aged persons with APOE ɛ3/ɛ3 genotype

Apolipoprotein E (APOE) genotypes are associated with variable risk of developing late‐onset Alzheimers disease (LOAD), with APOE epsilon 4 (APOE ɛ4) having higher risk. A variable poly‐T length polymorphism at rs10524523, within intron 6 of the translocase of the outer mitochondrial membrane (TOMM40) gene, has been shown to influence age of onset in LOAD, with very long (VL) poly‐T length associated with earlier disease onset, and short poly‐T length associated with later onset. In this study, we tested the hypothesis that brain and cognitive changes suggestive of presymptomatic LOAD may be associated with this TOMM40 polymorphism.

Malignant hyperthermia, coexisting disorders, and enzymopathies: risks and management options.

Clinical episodes and abnormal laboratory tests compatible with a diagnosis of malignant hyperthermia have been observed in patients with a diversity of syndromes, enzymopathies, and coexisting disorders thereby raising the likelihood of causal associations and heightened perioperative risk in others carrying a shared diagnosis. In the present review, we survey available published series, case reports, and the results of contracture testing in patients identified by others to be potentially predisposed to malignant hyperthermia. For most conditions, evidence for a causal relationship with malignant hyperthermia susceptibility is weak. The review concludes with suggestions for clinical management when evidence for or against an association is uncertain.

Autosomal Dominant Canine Malignant Hyperthermia Is Caused by a Mutation in the Gene Encoding the Skeletal Muscle Calcium Release Channel (RYR1 )

BackgroundMalignant hyperthermia (MH) is an inherited disorder of skeletal muscle characterized by hypercarbia, rhabdomyolysis, generalized skeletal muscle contracture, cardiac dysrhythmia, and renal failure, that develops on exposure to succinylcholine or volatile anesthetic agents. All swine and up to 50% of human MH events are thought to be associated with mutations in the calcium release channel of the sarcoplasmic reticulum, also known as the ryanodine receptor (RYR1). Events resembling MH have been reported in other species, but none have undergone genetic investigation to date. MethodsTo determine the molecular basis of canine MH, a breeding colony was established with a male, mixed-breed, MH-susceptible (MHS) dog that survived an in vivo halothane–succinylcholine challenge. He was mated to three unaffected females to produce four litters and back-crossed to an affected daughter to produce one litter. One of his MHS sons was mated to an unaffected female to produce an additional litter. Forty-seven dogs were phenotyped with an in vitro contracture test and diagnosed as MHS or MH normal based on the North American in vitro contracture test protocol. Nine microsatellite markers in the vicinity of RYR1 on canine chromosome 1 (CFA01) were tested for linkage to the MHS phenotype. Mutational analysis in two MHS and two MH-normal dogs was performed with direct sequencing of polymerase chain reaction products and of cloned fragments that represent frequently mutated human RYR1 regions. A restriction fragment length polymorphism was chosen to detect the candidate mutation in the pedigree at large. ResultsPedigree inspection revealed that MHS in this colony is transmitted as an autosomal dominant trait. FH2294, the marker closest to RYR1, is linked to MHS at a &thgr; = 0.03 with a LOD score of 9.24. A T1640C mutation gives rise to an alanine for valine substitution of amino acid 547 in the RYR1 protein, generating a maximum LOD score of 12.29 at &thgr; = 0.00. All dogs diagnosed as MHS by in vitro contracture test were heterozygous for the mutation, and all MH-normal dogs were homozygous for the T1640 allele. ConclusionsThese results indicate that autosomal dominant canine MH is caused by a mutation in the gene encoding the skeletal muscle calcium release channel and that the MHS trait in this pedigree of mixed-breed dogs is in perfect cosegregation with the RYR1 V547A mutation.

Difficult laryngoscopy and diabetes mellitus

The incidence of difficult laryngoscopy urns determined retrospectively in 40 diabetic patients having pancreas transplantations and in 75 diabetic and 112 nondiabetic patients having kidney transplantations. Diabetes was associated with a significant increase in the proportion of patients having difficult laryngoscopies in patients having renal transplants: 0.027 in patients without diabetes; 0.320 in patients with diabetes. The incidence of difficult laryngoscopy in diabetic recipients of cadaveric kidneys (0.419) was not significantly different from that in diabetic recipients of pancreas transplants (0.40), but significantly higher than that in diabetics given kidneys from living donors (0.187). Although cadaveric recipients were older than recipients of kidneys from living donors (40.8 v. 31.6 years), age at the time of transplantation ions not a significant predictor of difficulty in laryngoscopy. Groups were otherwise matched for clinical, morphologic, hematologic, and biochemical indices. Diabetic stiff joint syndrome (S/S), which predisposes a subset of Type I diabetic patients to rapidly progressive microvascular disease and subsequent need for renal and/or pancreas transplantation, may lead to difficult laryngoscopy because of involvement of the atlanto-occipital joint.

Detection of Human P2X7 Nucleotide Receptor Polymorphisms by a Novel Monocyte Pore Assay Predictive of Alterations in Lipopolysaccharide-Induced Cytokine Production

The nucleotide receptor P2X7 is expressed by most leukocytes and initiates signaling events that amplify numerous LPS responses. We tested the hypothesis that loss-of-function polymorphisms in the human P2X7 gene predispose to the production of an anti-inflammatory mediator balance. Accordingly, we developed a novel P2X7 pore assay in whole blood that magnifies the activity from wild-type alleles and preserves the gene dosage effect for the 1513 C polymorphism (AA, 69 ± 4; AC, 42 ± 4; and CC, 6 ± 1-fold stimulation). Thirty of 200 healthy individuals were identified as having low P2X7 pore activity. Seven low pore subjects were 1513 CC, 3 and 11 participants had the other known variants 946 GA and 1729 TA respectively; the remaining 9 volunteers likely have novel polymorphisms. Because platelets are a large source of extracellular ATP during inflammation, whole blood was treated ex vivo with Salmonella typhimurium LPS in the absence of exogenous nucleotides. LPS-stimulated whole blood from individuals in the low pore activity group generated reduced plasma levels of TNF-α (p = 0.036) and higher amounts of IL-10 (p < 0.001) relative to the high pore controls. This reduction in the TNF-α to IL-10 ratio persisted to at least 24 h and is further decreased by cotreatment with 2-methylthio-ATP. The ability of P2X7 polymorphisms to regulate the LPS-induced TNF-α to IL-10 ratio suggests that 15% of healthy adults may exhibit anti-inflammatory mediator responses during major infectious perturbations of the immune system, which can be predicted by P2X7 pore activity.

Activation of the Ca2+ release channel of skeletal muscle sarcoplasmic reticulum by palmitoyl carnitine

Studies of [3H]ryanodine binding, 45Ca2+ efflux, and single channel recordings in planar bilayers indicated that the fatty acid metabolite palmitoyl carnitine produced a direct stimulation of the Ca2+ release channel (ryanodine receptor) of rabbit and pig skeletal muscle junctional sarcoplasmic reticulum. At a concentration of 50 microM, palmitoyl carnitine (a) stimulated [3H]ryanodine binding 1.6-fold in a competitive manner at all pCa in the range 6 to 3; (b) released approximately 65% (30 nmol) of passively loaded 45Ca2+/mg protein; and (c) increased 7-fold the open probability of Ca2+ release channels incorporated into planar bilayers. Neither carnitine nor palmitic acid could reproduce the effect of palmitoyl carnitine on [3H]ryanodine binding, 45Ca2+ release, or channel open probability. 45Ca2+ release was induced by several long-chain acyl carnitines (C14, C16, C18) and acyl coenzyme A derivatives (C12, C14, C16), but not by the short-chain derivative C8 or by free saturated fatty acids of chain length C8 to C18, at room temperature or 36 degrees C. This newly identified interaction of esterified fatty acids and ryanodine receptors may represent a pathway by which metabolism of skeletal muscle could influence intracellular Ca2+ and may be responsible for the pathophysiology of disorders of beta-oxidation such as carnitine palmitoyl transferase II deficiency.

Attenuated P2X7 Pore Function as a Risk Factor for Virus-induced Loss of Asthma Control

RATIONALE Upper respiratory tract infection is a guideline accepted risk domain for the loss of asthma control. The ionotrophic nucleotide receptor P2X(7) regulates compartmentalized acute inflammation and the immune response to airway pathogens. OBJECTIVES We hypothesized that variability in P2X(7) function contributes to neutrophilic airway inflammation during a cold and thereby is linked to acute asthma. METHODS Research volunteers with asthma were enrolled at the onset of a naturally occurring cold and monitored through convalescence, assessing symptoms, lung function, and airway inflammation. P2X(7) pore activity in whole blood samples was measured using a genomically validated flow cytometric assay. MEASUREMENTS AND MAIN RESULTS Thirty-five participants with mild to moderate allergic asthma were enrolled and 31 completed all visits. P2X(7) pore function correlated with the change in nasal lavage neutrophil counts during the cold (R(s) = 0.514, P = 0.004) and was inversely related to the change in asthma symptoms (R(s) = -0.486, P = 0.009). The change in peak expiratory flow recordings, precold use of inhaled corticosteroids, and P2X(7) pore function were multivariate predictors of asthma symptoms (P = 0.001, < 0.001 and = 0.003 respectively). Attenuated P2X(7) activity was associated with the risk of losing asthma control (crude odds ratio, 11.0; 95% confidence interval, 1.1-106.4) even after adjustment for inhaled corticosteroids and rhinovirus (odds ratio, 15.0). CONCLUSIONS A whole blood P2X(7) pore assay robustly identifies participants with loss-of-function genotypes. Using this assay as an epidemiologic tool, attenuated P2X(7) pore activity may be a novel biomarker of virus-induced loss of asthma control.

A cysteine-for-arginine substitution (R614C) in the human skeletal muscle calcium release channel cosegregates with malignant hyperthermia

A point mutation in the human gene for the skeletal muscle calcium release channel (ryanodine receptor [RYR1]) correlates with inheritance of malignant hyperthermia in a family of Northern European descent. The substitution of thymine for cytosine at position 1840 of the RYR1 transcript results in a cysteine-for-arginine substitution at position 614 (R614C) of the amino acid sequence. The mutation was absent in 59 normal individuals from the general population, in 61 additional unrelated malignant hyperthermia-susceptible patients, and in 18 patients with malignant hyperthermia associated with other inherited or congenital diseases. Together with reports of an equivalent mutation in six susceptible pig strains and an identical mutation in one other human pedigree, these findings suggest that the cysteine-for-arginine mutation represents a shared calcium release channel pathogenesis between porcine malignant hyperthermia and a subset of mutations responsible for the human malignant hyperthermia syndrome.