17q21.31 duplication causes prominent tau-related dementia with increased MAPT expression.

To assess the role of rare copy number variations in Alzheimer's disease (AD), we conducted a case-control study using whole-exome sequencing data from 522 early-onset cases and 584 controls. The most recurrent rearrangement was a 17q21.31 microduplication, overlapping the CRHR1, MAPT, STH and KANSL1 genes that was found in four cases, including one de novo rearrangement, and was absent in controls. The increased MAPT gene dosage led to a 1.6-1.9-fold expression of the MAPT messenger RNA. Clinical signs, neuroimaging and cerebrospinal fluid biomarker profiles were consistent with an AD diagnosis in MAPT duplication carriers. However, amyloid positon emission tomography (PET) imaging, performed in three patients, was negative. Analysis of an additional case with neuropathological examination confirmed that the MAPT duplication causes a complex tauopathy, including prominent neurofibrillary tangle pathology in the medial temporal lobe without amyloid-ß deposits. 17q21.31 duplication is the genetic basis of a novel entity marked by prominent tauopathy, leading to early-onset dementia with an AD clinical phenotype. This entity could account for a proportion of probable AD cases with negative amyloid PET imaging recently identified in large clinical series.

[Validation of the French version of the self-evaluation of negative symptoms (SNS)]. / Validation de la version française de l'échelle autoévaluation des symptômes négatifs (SNS).

INTRODUCTION: Schizophrenia is a disorder affecting 1% of the population and is associated with severe functional impairment. Negative symptoms are responsible for the majority of this impairment, and many patients with schizophrenia have negative symptoms. However, their evaluation is still a challenge. Thus, standardized assessments are needed to facilitate identification of these symptoms. Many tools have been developed, but most are based on observer ratings. Self-evaluation can provide an additional outcome measure and allow patients to be more engaged in their treatment. The Self-evaluation of Negative Symptoms (SNS) has been developed recently. This is a remarkably understandable instrument for patients with schizophrenia as it allows them to readily complete it without assistance, providing information with respect to their own perception of negative symptoms. The SNS is a self-assessment that permits patients to evaluate themselves in 5 dimensions of negative symptoms. This validation study for the SNS revealed good psychometric properties alongside satisfactory acceptance by patients. AIM: This study was to confirm the validation of the French version of the self-evaluation of negative symptoms (SNS). METHODS: Patients with schizophrenia or schizoaffective disorder according to the DSM-IV-R, with a stable regimen of anti-psychotic drugs for the last two months, aged more than 18 years old were eligible for the study. Symptoms were rated using the SNS, the Scale for the Assessment of Negative Symptoms (SANS), the Calgary Depression Scale for Schizophrenics (CDSS), the Brief Psychiatric Rating Scale (BPRS) and the Clinical Global Impression and Parkinsonism. Patients were asked to fulfill the SNS twice, 6 weeks apart. RESULTS: Sixty patients were evaluated. Cronbach's coefficient (α=0.8) showed good internal consistency. The SNS significantly correlated with the SANS (r=0.6), the negative sub-score of the BPRS (r=0.6) and the Clinician Global Impression on the severity of negative symptoms (r=0.7). SNS scores did not correlate with level of insight (r=0.08) or Brief Psychiatric Rating Scale positive sub-scores (r=0.2). SNS scores correlated with CDSS scores. However, we did not find correlation between the first item of the CDSS which evaluates depression and the "diminished emotional range" sub-score of SNS. The test-retest of SNS revealed no changes of scores at two evaluations 6 weeks apart. CONCLUSION: The acceptance by patients of the SNS was excellent. The French version of the SNS demonstrated a good internal consistency, good convergent validity and good discriminant validity. The study demonstrates the ability of patients with schizophrenia to accurately report their own experiences. Self-assessments of negative symptoms should be more widely employed in clinical practice because they may allow patients with schizophrenia to develop appropriate coping strategies.

Alzheimer disease: modeling an Aß-centered biological network.

In genetically complex diseases, the search for missing heritability is focusing on rare variants with large effect. Thanks to next generation sequencing technologies, genome-wide characterization of these variants is now feasible in every individual. However, a lesson from current studies is that collapsing rare variants at the gene level is often insufficient to obtain a statistically significant signal in case-control studies, and that network-based analyses are an attractive complement to classical approaches. In Alzheimer disease (AD), according to the prevalent amyloid cascade hypothesis, the pathology is driven by the amyloid beta (Aß) peptide. In past years, based on experimental studies, several hundreds of proteins have been shown to interfere with Aß production, clearance, aggregation or toxicity. Thanks to a manual curation of the literature, we identified 335 genes/proteins involved in this biological network and classified them according to their cellular function. The complete list of genes, or its subcomponents, will be of interest in ongoing AD genetic studies.

SORL1 rare variants: a major risk factor for familial early-onset Alzheimer's disease.

The SORL1 protein plays a protective role against the secretion of the amyloid ß peptide, a key event in the pathogeny of Alzheimer's disease. We assessed the impact of SORL1 rare variants in early-onset Alzheimer's disease (EOAD) in a case-control setting. We conducted a whole exome analysis among 484 French EOAD patients and 498 ethnically matched controls. After collapsing rare variants (minor allele frequency ≤1%), we detected an enrichment of disruptive and predicted damaging missense SORL1 variants in cases (odds radio (OR)=5.03, 95% confidence interval (CI)=(2.02-14.99), P=7.49.10(-5)). This enrichment was even stronger when restricting the analysis to the 205 cases with a positive family history (OR=8.86, 95% CI=(3.35-27.31), P=3.82.10(-7)). We conclude that predicted damaging rare SORL1 variants are a strong risk factor for EOAD and that the association signal is mainly driven by cases with positive family history.

A novel Alzheimer disease locus located near the gene encoding tau protein.

APOE ɛ4, the most significant genetic risk factor for Alzheimer disease (AD), may mask effects of other loci. We re-analyzed genome-wide association study (GWAS) data from the International Genomics of Alzheimer's Project (IGAP) Consortium in APOE ɛ4+ (10 352 cases and 9207 controls) and APOE ɛ4- (7184 cases and 26 968 controls) subgroups as well as in the total sample testing for interaction between a single-nucleotide polymorphism (SNP) and APOE ɛ4 status. Suggestive associations (P<1 × 10(-4)) in stage 1 were evaluated in an independent sample (stage 2) containing 4203 subjects (APOE ɛ4+: 1250 cases and 536 controls; APOE ɛ4-: 718 cases and 1699 controls). Among APOE ɛ4- subjects, novel genome-wide significant (GWS) association was observed with 17 SNPs (all between KANSL1 and LRRC37A on chromosome 17 near MAPT) in a meta-analysis of the stage 1 and stage 2 data sets (best SNP, rs2732703, P=5·8 × 10(-9)). Conditional analysis revealed that rs2732703 accounted for association signals in the entire 100-kilobase region that includes MAPT. Except for previously identified AD loci showing stronger association in APOE ɛ4+ subjects (CR1 and CLU) or APOE ɛ4- subjects (MS4A6A/MS4A4A/MS4A6E), no other SNPs were significantly associated with AD in a specific APOE genotype subgroup. In addition, the finding in the stage 1 sample that AD risk is significantly influenced by the interaction of APOE with rs1595014 in TMEM106B (P=1·6 × 10(-7)) is noteworthy, because TMEM106B variants have previously been associated with risk of frontotemporal dementia. Expression quantitative trait locus analysis revealed that rs113986870, one of the GWS SNPs near rs2732703, is significantly associated with four KANSL1 probes that target transcription of the first translated exon and an untranslated exon in hippocampus (P ⩽ 1.3 × 10(-8)), frontal cortex (P ⩽ 1.3 × 10(-9)) and temporal cortex (P⩽1.2 × 10(-11)). Rs113986870 is also strongly associated with a MAPT probe that targets transcription of alternatively spliced exon 3 in frontal cortex (P=9.2 × 10(-6)) and temporal cortex (P=2.6 × 10(-6)). Our APOE-stratified GWAS is the first to show GWS association for AD with SNPs in the chromosome 17q21.31 region. Replication of this finding in independent samples is needed to verify that SNPs in this region have significantly stronger effects on AD risk in persons lacking APOE ɛ4 compared with persons carrying this allele, and if this is found to hold, further examination of this region and studies aimed at deciphering the mechanism(s) are warranted.

Investigation of reference levels and radiation dose associated with abdominal EVAR (endovascular aneurysm repair) procedures across several European Centres.

OBJECTIVES: Endovascular aneurysm repair (EVAR) is considered the treatment of choice for abdominal aortic aneurysms with suitable anatomy. In order to improve radiation safety, European Directive (2013/59) requires member states to implement diagnostic reference levels (DRLs) in radio-diagnostic and interventional procedures. This study aimed to determine local DRLs for EVAR across five European centres and identify an interim European DRL, which currently remains unestablished. METHODS: Retrospective data was collected for 180 standard EVARs performed between January 2014 and July 2015 from five specialist centres in Ireland (n=2) and Italy (n=3). Data capture included: air kerma-area product (PKA), total air kerma at the reference point (Ka,r), fluoroscopic time (FT), number of acquisitions, frame rate of acquisition, type of acquisition, patient height, weight, and gender. RESULTS: The mean values for each site A, B, C, D, and E were: PKAs of 4343 ± 994 µGym2, 18,200 ± 2141 µGym2, 11,423 ± 1390 µGym2, 7796 ± 704 µGym2, 31,897 ± 5798 µGym2; FTs of 816 ± 92 s, 950 ± 150 s, 708 ± 70 s, 972 ± 61 s, 827 ± 118 s; and number of acquisitions of 6.72 ± 0.56, 10.38 ± 1.54, 4.74 ± 0.19, 5.64 ± 0.36, 7.28 ± 0.65, respectively. The overall pooled 75th percentile PKA was 15,849 µGym2. CONCLUSION: Local reference levels were identified. The pooled data has been used to establish an interim European DRL for EVAR procedures. KEY POINTS: • Abdominal endovascular aneurysm repair (EVAR) requires the use of ionising radiation. • EVAR is a minimally invasive procedure for the treatment of abdominal aortic aneurysms. • Diagnostic reference levels (DRLs) are used to monitor patient radiation exposure. • Radiation dose data was collected from five European centres for EVAR procedures. • Local DRLs have been determined and an interim European DRL is proposed.

[Association between the violence in the community and the aggressive behaviors of psychotics during their hospitalizations]. / Relation entre la violence intra-hospitalière des patients avec psychoses et la violence dans la communauté.

BACKGROUND: Violence is a common issue in psychiatry and has multiple determiners. The aim of this study is to assess the psychotic inpatients' violence in association with the violence of the neighborhood from which the patients are drawn and to estimate the impact of this environmental factor with regard to other factors. METHOD: A prospective multicenter study was led in nine French cities. Eligible patients were psychotic involuntary patients hospitalized in the cities' psychiatric wards. During their treatments, any kind of aggressive behavior by the patients has been reported by the Overt Aggression Scale (OAS). RESULTS: From June 2010 to May 2011, 95 patients have been included. Seventy-nine per cent of the patients were violent during their hospitalizations. In a bivariate analysis, inpatient violence was significantly associated with different factors: male gender, patient violence history, substance abuse, manic or mixed disorder, the symptoms severity measured by the BPRS, the insight degree and the city crime rate. In a multivariate analysis, the only significant factors associated with the patients' violence were substance abuse, the symptoms severity and the crime rates from the different patients' cities. CONCLUSION: These results suggest that violence within the psychotic patients' neighborhood could represent a risk of violence during their treatments.

De novo deleterious genetic variations target a biological network centered on Aß peptide in early-onset Alzheimer disease.

We hypothesized that de novo variants (DNV) might participate in the genetic determinism of sporadic early-onset Alzheimer disease (EOAD, onset before 65 years). We investigated 14 sporadic EOAD trios first by array-comparative genomic hybridization. Two patients carried a de novo copy number variation (CNV). We then performed whole-exome sequencing in the 12 remaining trios and identified 12 non-synonymous DNVs in six patients. The two de novo CNVs (an amyloid precursor protein (APP) duplication and a BACE2 intronic deletion) and 3/12 non-synonymous DNVs (in PSEN1, VPS35 and MARK4) targeted genes from a biological network centered on the Amyloid beta (Aß) peptide. We showed that this a priori-defined genetic network was significantly enriched in amino acid-altering DNV, compared with the rest of the exome. The causality of the APP de novo duplication (which is the first reported one) was obvious. In addition, we provided evidence of the functional impact of the following three non-synonymous DNVs targeting this network: the novel PSEN1 variant resulted in exon 9 skipping in patient's RNA, leading to a pathogenic missense at exons 8-10 junction; the VPS35 missense variant led to partial loss of retromer function, which may impact neuronal APP trafficking and Aß secretion; and the MARK4 multiple nucleotide variant resulted into increased Tau phosphorylation, which may trigger enhanced Aß-induced toxicity. Despite the difficulty to recruit Alzheimer disease (AD) trios owing to age structures of the pedigrees and the genetic heterogeneity of the disease, this strategy allowed us to highlight the role of de novo pathogenic events, the putative involvement of new genes in AD genetics and the key role of Aß network alteration in AD.

A new highly penetrant form of obesity due to deletions on chromosome 16p11.2.

Obesity has become a major worldwide challenge to public health, owing to an interaction between the Western 'obesogenic' environment and a strong genetic contribution. Recent extensive genome-wide association studies (GWASs) have identified numerous single nucleotide polymorphisms associated with obesity, but these loci together account for only a small fraction of the known heritable component. Thus, the 'common disease, common variant' hypothesis is increasingly coming under challenge. Here we report a highly penetrant form of obesity, initially observed in 31 subjects who were heterozygous for deletions of at least 593 kilobases at 16p11.2 and whose ascertainment included cognitive deficits. Nineteen similar deletions were identified from GWAS data in 16,053 individuals from eight European cohorts. These deletions were absent from healthy non-obese controls and accounted for 0.7% of our morbid obesity cases (body mass index (BMI) >or= 40 kg m(-2) or BMI standard deviation score >or= 4; P = 6.4 x 10(-8), odds ratio 43.0), demonstrating the potential importance in common disease of rare variants with strong effects. This highlights a promising strategy for identifying missing heritability in obesity and other complex traits: cohorts with extreme phenotypes are likely to be enriched for rare variants, thereby improving power for their discovery. Subsequent analysis of the loci so identified may well reveal additional rare variants that further contribute to the missing heritability, as recently reported for SIM1 (ref. 3). The most productive approach may therefore be to combine the 'power of the extreme' in small, well-phenotyped cohorts, with targeted follow-up in case-control and population cohorts.

Increased expression of BIN1 mediates Alzheimer genetic risk by modulating tau pathology.

Genome-wide association studies (GWAS) have identified a region upstream the BIN1 gene as the most important genetic susceptibility locus in Alzheimer's disease (AD) after APOE. We report that BIN1 transcript levels were increased in AD brains and identified a novel 3 bp insertion allele ∼28 kb upstream of BIN1, which increased (i) transcriptional activity in vitro, (ii) BIN1 expression levels in human brain and (iii) AD risk in three independent case-control cohorts (Meta-analysed Odds ratio of 1.20 (1.14-1.26) (P=3.8 × 10(-11))). Interestingly, decreased expression of the Drosophila BIN1 ortholog Amph suppressed Tau-mediated neurotoxicity in three different assays. Accordingly, Tau and BIN1 colocalized and interacted in human neuroblastoma cells and in mouse brain. Finally, the 3 bp insertion was associated with Tau but not Amyloid loads in AD brains. We propose that BIN1 mediates AD risk by modulating Tau pathology.

[Pharmacological treatments in patients with pervasive developmental disorders: A review]. / Efficacité des traitements pharmacologiques dans les troubles envahissants du développement : une revue de la littérature.

BACKGROUND: Pervasive developmental disorders (PDD) are neurodevelepmental disorders that are characterized by severe deficits in socialisation and communication, and the existence of repetitive and stereotyped interests and behaviours. It is estimated more than 60/100,000 children are suffering from PDD. Comorbid disorders are common in people with PDD, including intellectual deficiency, symptoms of attention deficit-hyperactivity, aggression and disruption, and pervasive repetitive behaviours or thoughts. These symptoms have a negative impact on the outcome and quality of life of the patients and their caregivers. The first-line management of comorbid disorders in PDD is behavioural intervention, but sometimes this is not sufficient, and the use of pharmacological treatment is needed. METHOD: We conducted a review of studies of medical treatments used in patients with PDD to establish which treatments show good evidence of efficacy in PDD. We used the Medline database and the following keywords "pervasive development disorders" or "autism spectrum disorders" or "autistic disorder" and "therapy" or "treatment". RESULTS: The treatments that showed the best efficacy on irritability in well-designed studies are second generation antipsychotics, risperidone and aripiprazole. Some studies indicate that haloperidol is efficient as well, but the very high frequency of extra-pyramidal effects limits its use. Methylphenidate has shown some efficacy on impulsivity and hyperactivity in randomised placebo-controlled studies. First data concerning atomoxetine are promising but better-designed studies are needed. Selective serotonin re-uptake inhibitors: fluvoxamine and fluoxetine have shown some efficacy in the treatment of serious and pervasive repetitive behaviours. Alpha-adrenergic treatments, clonidine and guanfacine, can help in the management of disruptive behaviours in patients with PDD. Data concerning naltrexone are contradictory, indeed many case reports of its efficacy on aggressive (mostly auto-aggressive) behaviours are reported in the literature, but well-designed studies do not find any improvement in patients treated with naltrexone compared with patients treated with placebo. First data concerning ocytocin are promising, indeed, if they were to be confirmed, that would be the first treatment efficient on the core symptoms of PDD.

Xq27 FRAXA locus is a strong candidate for dyslexia: evidence from a genome-wide scan in French families.

Dyslexia is a frequent neurodevelopmental learning disorder. To date, nine susceptibility loci have been identified, one of them being DYX9, located in Xq27. We performed the first French SNP linkage study followed by candidate gene investigation in dyslexia by studying 12 multiplex families (58 subjects) with at least two children affected, according to categorical restrictive criteria for phenotype definition. Significant results emerged on Xq27.3 within DYX9. The maximum multipoint LOD score reached 3,884 between rs12558359 and rs454992. Within this region, seven candidate genes were investigated for mutations in exonic sequences (CXORF1, CXORF51, SLITRK2, FMR1, FMR2, ASFMR1, FMR1NB), all having a role during brain development. We further looked for 5'UTR trinucleotide repeats in FMR1 and FMR2 genes. No mutation or polymorphism co-segregating with dyslexia was found. This finding in French families with Dyslexia showed significant linkage on Xq27.3 enclosing FRAXA, and consequently confirmed the DYX9 region as a robust susceptibility locus. We reduced the previously described interval from 6.8 (DXS1227-DXS8091) to 4 Mb also disclosing a higher LOD score.

High frequency of potentially pathogenic SORL1 mutations in autosomal dominant early-onset Alzheimer disease.

Performing exome sequencing in 14 autosomal dominant early-onset Alzheimer disease (ADEOAD) index cases without mutation on known genes (amyloid precursor protein (APP), presenilin1 (PSEN1) and presenilin2 (PSEN2)), we found that in five patients, the SORL1 gene harbored unknown nonsense (n=1) or missense (n=4) mutations. These mutations were not retrieved in 1500 controls of same ethnic origin. In a replication sample, including 15 ADEOAD cases, 2 unknown non-synonymous mutations (1 missense, 1 nonsense) were retrieved, thus yielding to a total of 7/29 unknown mutations in the combined sample. Using in silico predictions, we conclude that these seven private mutations are likely to have a pathogenic effect. SORL1 encodes the Sortilin-related receptor LR11/SorLA, a protein involved in the control of amyloid beta peptide production. Our results suggest that besides the involvement of the APP and PSEN genes, further genetic heterogeneity, involving another gene of the same pathway is present in ADEOAD.

Effect of timing of post-partum introduction to pasture and supplementation with Saccharomyces cerevisiae on milk production, metabolic status, energy balance and some reproductive parameters in early lactation dairy cows.

Dietary change, an inconsistent nutrient intake and high levels of milk production make the early post-partum period (PP) a challenging time for the lactating dairy cow. This experiment investigates the effects of two early PP nutritional management strategies (NM): abrupt introduction to pasture (AP) or a total mixed ration (TMR) for 21 days followed by a gradual introduction to pasture over 7 days (GP), with (Y) or without (C) live yeast (YS) on milk production, energy balance (EB) and selected metabolic and reproductive variables. Forty multiparous dairy cows were assigned to one of four dietary treatments in a two (AP vs. GP) by two (Y vs. C) factorial, randomized block design. The experiment was conducted from days 1 to 70 PP. Blood samples were taken on day 1, day 5 and every 10 days until day 45 to determine metabolites, whilst intake (DMI), and EB were determined during week 6 PP. Milk was sampled weekly for fat, protein and lactose. Trans-rectal scanning for reproductive variables commenced on day 10 PP. Animals in the GP group had a higher DMI (p = 0.04), higher fat yield (p = 0.08) and fewer days to first ovulation (p = 0.09) vs. those in the AP group. EB (-3.5 ± 0.67 units of energy for milk production) and body condition score loss (0.70 ± 0.09) were not affected by NM. However, non-esterified fatty acids (NEFA) (p < 0.01) were higher, and glucose (p = 0.02) was lower in the AP vs. the GP group. Supplementary YS tended to improve EB (p = 0.09) and reduced NEFA (p < 0.01) vs. non-supplemented animals. These data suggest that offering animals a nutritionally balanced TMR during the first 3 weeks PP followed by a gradual introduction to pasture can improve DMI vs. pasture-based diets. Additionally, the blood metabolic profile suggests a more favourable energy status in the GP group or where YS was supplemented during the early PP period.

[Alzheimer disease: autosomal dominant forms]. / Génétique de la maladie d'Alzheimer: formes autosomiques dominantes.

We propose a review devoted to the autosomal dominant forms of Alzheimer disease (AD). These forms are the consequences of either PSEN1 mutations (69%), APP mutations (1%), or APP duplication (7.5%), and exceptionally of PSEN2 mutations (2%). The main characteristic of these AD forms is the early age of onset usually before the age of 60 years. The first part of the review focuses on the identification of unusual clinical and neuropathological phenotypes enlarging the AD spectrum: intracerebral hemorrhages caused by severe amyloid angiopathy, spastic paraparesis, Lewy body dementia and exceptional cerebellar ataxia. The second part concerns the consequences of these mutations on A beta processing, thus demonstrating the key role of the causal "amyloid cascade".

Eosinophil-nerve interactions and neuronal plasticity in rat gut associated lymphoid tissue (GALT) in response to enteric parasitism.

Intestinal lymphoid tissues and Peyer's patches (PP) are innervated sites of immune surveillance in the gastrointestinal tract. Following infection with F. hepatica, neuronal hyperplasia and significantly increased eosinophil and mast cell trafficking to colonic PP sites were evident in rat tissues. Nerve-eosinophil associations were significantly elevated in infected colon and colonic PP, as were colonic tissue levels of the circulatory recruitment factors IL-5 and eotaxin. Increased immunoreactivity for neuronal plasticity markers GAP-43 and neural cell adhesion molecule (NCAM) was also found in infected tissues. Such neuronal alterations in the PP during enteric parasitism may have functional consequences on particular or pathogen uptake.

Resting membrane potential and ionic distribution in fast- and slow-twitch mammalian muscle.

The resting membrane potential and intracellular potassium and sodium concentration of three guinea pig hind limb muscles were studied. These properties are related to the gross color, the speed of contraction, and the biochemically defined fiber type composing the muscle. The resting membrane potential and intracellular content were: white vastus (grossly white, fast-twitch glycolytic) -85.3 mV. potassium 171.9 meq/liter; soleus (grossly red, slow-twitch oxidative) -69.7 mV, potassium 137.5 meq/liter; and red vastus lateralis (grossly red, fast-twitch oxidative glycolytic) -71.7 mV, potassium 139.6 meq/liter. In soleus and red vastus lateralis, the relative permeability of sodium to potassium was 0.041 and 0.036, while in white vastus it was 0.015. These results give us the first exception to the hypothesis that fast-twitch fibers have higher intracellular potassium and higher resting membrane potential than slow-twitch fibers.

Uric acid. Characterization of its interaction with human serum albumin.

Binding of sodium urate to human serum albumin (HSA) was measured by continuous ultrafiltration at pH 7.4 and ionic strength 0.16 over the concentration range 1-13 mg/100 ml. The percent sodium urate bound to 5 g/100 ml HSA was constant over this concentration range: 30.3 (SE+/-0.6)% being bound at 4 degrees C, 22.6+/-0.3% at 22.5 degrees C, and 19.6+/-0.3% at 37 degrees C. Derived association constants, assuming one binding site were 6.0 x 10(2) M(-1) (4 degrees C), 4.47 x 10(2) M(-1) (22.5 degrees C), and 3.88 x 10(2) M(-1) (37 degrees C).

Measurement of intracellular pH of skeletal muscle with pH-sensitive glass microelectrodes.

We used three methods to examine the relationship among intracellular pH, transmembrane potential, and extracellular pH. Single-barreled electrodes permitted the determination of resting potential and intracellular pH with a minimum of cellular injury. Double-barreled electrodes, which incorporated a reference as well as a pH-sensitive electrode in a single tip, facilitated the direct measurement of intracellular pH without the interposition of the transmembrane potential. Triple-barreled electrodes permitted measurement of intracellular pH during the controlled hyperpolarization or depolarization of the cell membrane. The results of all three methods were in close agreement and disclosed that the H(+) activity of intracellular and extracellular fluid is in electrochemical equilibrium at any given transmembrane potential. This implies that the determinants of intracellular pH are the transmembrane potential and the blood pH. The actual pH of the normal resting muscle cell is 5.99, as estimated from the normal transmembrane potential and blood pH, or as determined by direct measurements of intracellular pH.