Trypsin cleaves acid-sensing ion channel 1a in a domain that is critical for channel gating.

Acid-sensing ion channels (ASICs) are neuronal Na(+) channels that are members of the epithelial Na(+) channel/degenerin family and are transiently activated by extracellular acidification. ASICs in the central nervous system have a modulatory role in synaptic transmission and are involved in cell injury induced by acidosis. We have recently demonstrated that ASIC function is regulated by serine proteases. We provide here evidence that this regulation of ASIC function is tightly linked to channel cleavage. Trypsin cleaves ASIC1a with a similar time course as it changes ASIC1a function, whereas ASIC1b, whose function is not modified by trypsin, is not cleaved. Trypsin cleaves ASIC1a at Arg-145, in the N-terminal part of the extracellular loop, between a highly conserved sequence and a sequence that is critical for ASIC1a inhibition by the venom of the tarantula Psalmopoeus cambridgei. This channel domain controls the inactivation kinetics and co-determines the pH dependence of ASIC gating. It undergoes a conformational change during inactivation, which renders the cleavage site inaccessible to trypsin in inactivated channels.

Neuronal calcium channel mutation in a patient with congenital ataxia and attacks of hemiplegic migraine with cerebral edema

Background: Familial Hemiplegic Migraine (FHM), characterized by a prolonged unilateral hemiparesis, mainly results from mutations in the alpha-1a subunit of the calcium channel gene CACNA1A that can also cause two other dominantly inherited neurological disorders, Episodic Ataxia type 2 (EA2, with sometimes migrainous headaches) and Spinocerebellar Ataxia type 6 (SCA6, late-onset and progressive). A same mutation can have different clinical expression in a family (hemiplegic migraine, migraine-coma, cerebellar ataxia). CACNA1A mutations in FHM are usually missense, leading to gain-of-function, while truncating mutations leading to loss-of-function are usually associated with EA2. Case report: This 9-year-old girl was seen as a baby for hypotonia and transient vertical nystagmus. Her first brain MRI was normal. She evolved as a congenital ataxia, but since the age of two, she had attacks of coma, hemiparesis (either side), partial seizures, dystonic movements and fever. Attacks were initially triggered by minor head bumps, subsequently spontaneous. Brain MRIs in the acute stage always showed transient unilateral hemisphere swelling. Follow-up images revealed atrophic lesions in the temporo-occipital regions and cerebellar atrophy. A prophylactic trial with flunarizine was ineffective. Acetazolamide was recently introduced. Methods: Since our patient shared features of both FHM and EA2, we studied the CACNA1A gene by direct sequencing in the patient's and parents' DNA. Results: We identified an unreported de novo heterozygous deletion of three base pairs (c.4503_4505delCTT) predicting the deletion of one amino acid (p.Phe1502del). The CACNA1A protein contains 4 domains, each formed by six transmembrane segments. The deletion is located in a highly conserved region in segment 6 (S6) of the third domain. Mutations in S6 segments of calcium channels change single-channel conductance and channel selectivity, most resulting in loss-of-function. Outlook: In vitro expression studies of the identified mutation are underway, aiming at understanding its functional consequences and finding an efficient treatment.

Lag-one autocorrelation in short series: Estimation and hypothesis testing

In the first part of the study, nine estimators of the first-order autoregressive parameter are reviewed and a new estimator is proposed. The relationships and discrepancies between the estimators are discussed in order to achieve a clear differentiation. In the second part of the study, the precision in the estimation of autocorrelation is studied. The performance of the ten lag-one autocorrelation estimators is compared in terms of Mean Square Error (combining bias and variance) using data series generated by Monte Carlo simulation. The results show that there is not a single optimal estimator for all conditions, suggesting that the estimator ought to be chosen according to sample size and to the information available of the possible direction of the serial dependence. Additionally, the probability of labelling an actually existing autocorrelation as statistically significant is explored using Monte Carlo sampling. The power estimates obtained are quite similar among the tests associated with the different estimators. These estimates evidence the small probability of detecting autocorrelation in series with less than 20 measurement times.

Role of the epithelial sodium channel (ENaC) and its regulator CAP1/Prss8 in colon

Dans les cellules épithéliales sensibles à l'aldostérone, le canal sodique épithélial (ENaC) joue un rôle critique dans le contrôle de l'équilibre sodique, le volume sanguin, et la pression sanguine. Le rôle d'ENaC est bien caractérisé dans le rein et les poumons, cependant le rôle d'ENaC et son régulateur positif la protéase activatrice de canal 1 (CAP1 /Prss8) sur le transport sodique dans le côlon reste en grande partie inconnu. Nous avons étudié l'importance d'ENaC et de CAPMPrss8 dans le côlon. Les souris déficientes pour la sous- unité aENaC (souris ScnnlaKO) dans les cellules superficielles intestinales étaient viables et ne montraient pas de létalité embryonnaire ou postnatale. Sous diète normale (RS) ou pauvre en sodium (LS), la différence de potentiel rectale sensible à l'amiloride (APDamii) était drastiquement diminuée et son rythme circadien atténué. Sous diète normale (RS) ou diète riche en sodium (HS) ou fort chargement de potassium, le sodium et le potassium plasmatique et urinaire n'étaient pas significativement changé. Cependant, sous LS, les souris Senni aK0 perdaient des quantités significativement augmentées de sodium dans leurs fèces, accompagnées par de très hauts taux d'aldostérone plasmatique et une rétention urinaire en sodium augmentée. Les souris déficientes en CAPl/PmS (Prss8K0) dans les cellules superficielles intestinales étaient viables et ne montraient pas de létalité embryonnaire ou postnatale. Sous diètes RS et HS cependant, les souris Prss8KO montraient une diminution significative du APDamil dans l'après-midi, mais le rythme circadien était maintenu. Sous diète LS, la perte de sodium par les fèces était accompagnée par des niveaux d'aldostérone plasmatiques plus élevés. Par conséquent, nous avons identifié la protéase activatrice de canal CAP 1 IPrss8 comme un régulateur important d'ENaC dans le côlon in vivo. De plus, nous étudions l'importance d'ENaC et de CAPIIPrss8 dans les conditions pathologiques comme les maladies inflammatoires chroniques de l'intestin (MICI). Le résultat préliminaire out montre qu'une déficience d'Prss8 mènait à la détérioration de la colite induite par le DSS comparé aux modèles contrôles respectifs. En résumé, l'étude a montré que sous restriction de sel, l'absence d'ENaC dans Pépithélium de surface du côlon était compensée par 1'activation du système rénine-angiotensine- aldostérone (RAAS) dans le rein. Ceci a mené à un pseudohypoaldostéronisme de type I spécifique au côlon avec résistance aux minéralocorticoïdes sans signe d'altération de rétention de potassium. - In aldosterone-responsive epithelial cells of kidney and colon, the epithelial sodium channel (ENaC) plays a critical role in the control of sodium balance, blood volume, and blood pressure. The role of ENaC is well characterized in kidney and lung, whereas role of ENaC and its positive regulator channel-activating protease 1 (CAPl/PrasS) on sodium transport in colon is largely unknown. We have investigated the importance of ENaC and CAPI/Prss8 in colon for sodium and potassium balance. Mice lacking the aENaC subunit (Scnnla mice) in intestinal superficial cells were viable and did not show any fetal or perinatal lethality. Under regular (RS) or low salt (LS) diet, the amiloride sensitive rectal potential difference (APDamii) was drastically decreased and its circadian rhythm blunted. Under regular salt (RS) or high salt (HS) diets or under potassium loading, plasma and urinary sodium and potassium were not significantly changed. However, upon LS, the ScnnlaK0 mice lost significant amounts of sodium in their feces, accompanied by very high plasma aldosterone and increased urinary sodium retention. Mice lacking the CAPl/PrasS (Prss8K0) in intestinal superficial cells were viable and did not show any fetal or perinatal lethality. Upon RS and HS diets, however, Prss8K0 exhibited a significantly reduced APDamii in the afternoon, but its circadian rhythm was maintained. Upon LS diet, sodium loss through feces was accompanied by higher plasma aldosterone levels. Thus, we have identified the channel-activating protease CAPl/Prss8 as an important in vivo regulator of ENaC in colon. Furthermore, we are investigating the importance of ENaC and CAPI/Prss8 in pathological conditions like inflammatory bowel disease (IBD). Preliminary data showed that PmS-deficiency led to worsening of DSS-induced colitis as compared to their respective controls. Overall, the present study has shown that under salt restriction, the absence of ENaC in colonic surface epithelium was compensated by the activation of renin-angiotensin- aldosterone (RAAS) system in the kidney. This led to a colon specific pseudohypoaldosteroni sm type 1 with mineralocorticoid resistance without evidence of impaired potassium retention.

Role of the epithelial sodium channel (ENaC) in the epidermal barrier function of the skin

Abstract In humans, the skin is the largest organ of the body, covering up to 2m2 and weighing up to 4kg in an average adult. Its function is to preserve the body from external insults and also to retain water inside. This barrier function termed epidermal permeability barrier (EPB) is localized in the functional part of the skin: the epidermis. For this, evolution has built a complex structure of cells and lipids sealing the surface, the stratum corneum. The formation of this structure is finely tuned since it is not only formed once at birth, but renewed all life long. This active process gives a high plasticity and reactivity to skin, but also leads to various pathologies. ENaC is a sodium channel extensively studied in organs like kidney and lung due to its importance in regulating sodium homeostasis and fluid volume. It is composed of three subunits α, ß and r which are forming sodium selective channel through the cell membrane. Its presence in the skin has been demonstrated, but little is known about its physiological role. Previous work has shown that αENaC knockout mice displayed an abnormal epidermis, suggesting a role in differentiation processes that might be implicated in the EPB. The principal aim of this thesis has been to study the consequences for EPB function in mice deficient for αENaC by molecular and physiological means and to investigate the underlying molecular mechanisms. Here, the barrier function of αENaC knockout pups is impaired. Apparently not immediately after birth (permeability test) but 24h later, when evident water loss differences appeared compared to wildtypes. Neither the structural proteins of the epithelium nor the tights junctions showed any obvious alterations. In contrary, stratum corneum lipid disorders are most likely responsible for the barrier defect, accompanied by an impairment of skin surface acidification. To analyze in details this EPB defect, several hypotheses have been proposed: reduced sensibility to calcium which is the key activator far epidermal formation, or modification of ENaC-mediated ion fluxes/currents inside the epidermis. The cellular localization of ENaC and the action in the skin of CAPl, a positive regulator of ENaC, have been also studied in details. In summary, this study clearly demonstrates that ENaC is a key player in the EPB maintenance, because αENaC knockout pups are not able to adapt to the new environment (ex utero) as efficiently as the wildtypes, most likely due to impaired of sodium handling inside the epidermis. Résumé Chez l'homme, la peau est le plus grand organe, couvrant presque 2m2 et pesant près de 4kg chez l'adulte. Sa fonction principale est de protéger l'organisme des agressions extérieures mais également de conserver l'eau à l'intérieur du corps. Cette fonction nommée barrière épithéliale est localisée dans la partie fonctionnelle de la peau : l'épiderme. A cette fin, l'évolution s'est dotée d'une structure complexe composée de cellules et de lipides recouvrant la surface, la couche cornée. Sa formation est finement régulée, car elle n'est pas seulement produite à la naissance mais constamment renouvelée tout au long de la vie, ce qui lui confère une grande plasticité mais ce qui est également la cause de nombreuses pathologies. ENaC est un canal sodique très étudié dans le rein et le poumon pour son importance dans la régulation de l'homéostasie sodique et la régulation du volume du milieu intérieur. Il est composé de 3 sous unités, α, ß et y qui forment un pore sélectif pour le sodium dans les membranes. Ce canal est présent dans la peau mais sa fonction n'y est pas connue. Des travaux précédents ont pu montrer que les souris dont le gène codant pour αENaC a été invalidé présentent un épiderme pathologique, suggérant un rôle dans la différentiation et pourrait même être impliqué dans la barrière épithéliale. Le but de cette thèse fut l'étude de la barrière dans ces souris knockouts avec des méthodes moléculaires et physiologiques et la caractérisation des mécanismes moléculaire impliqués. Dans ce travail, il a été montré que les souris mutantes présentaient un défaut de la barrière. Ce défaut n'est pas visible immédiatement à la naissance (test de perméabilité), mais 24h plus tard, lorsque les tests de perte d'eau transépithéliale montrent une différence évidente avec les animaux contrôles. Ni les protéines de structures ni les jonctions serrées de l'épiderme ne présentaient d'imperfections majeures. A l'inverse, les lipides de la couche cornée présentaient un problème de maturation (expliquant le phénotype de la barrière), certainement consécutif au défaut d'acidification à la surface de la peau que nous avons observé. D'autres mécanismes ont été explorées afin d'investiguer cette anomalie de la barrière, comme la réduction de sensibilité au calcium qui est le principal activateur de la formation de l'épiderme, ou la modification des flux d'ions entre les couches de l'épiderme. La localisation cellulaire d'ENaC, et l'action de son activateur CAPl ont également été étudiés en détails. En résumé, cette étude démontre clairement qu'ENaC est un acteur important dans la formation de la barrière épithéliale, car la peau des knockouts ne s'adapte pas aussi bien que celle des sauvages au nouvel environnement ex utero à cause de la fonction d'ENaC dans les mouvements de sodium au sein même de l'épiderme. Résumé tout public Chez l'homme, la peau est le plus grand organe, couvrant presque 2m2 et pesant près de 4kg chez l'adulte. Sa fonction principale est de protéger l'organisme des agressions extérieures mais également de conserver l'eau à l'intérieur du corps. Cette fonction nommée barrière épithéliale est localisée dans la partie fonctionnelle de la peau : l'épiderme. A cette fin, l'évolution s'est dotée d'une structure complexe composée de cellules et de lipides recouvrant la surface, la couche cornée. Sa formation est finement régulée, car elle n'est pas seulement produite à la naissance mais constamment renouvelée tout au long de la vie, ce qui lui confère une grande plasticité mais ce qui est également la cause de nombreuses maladies. ENaC est une protéine formant un canal qui permet le passage sélectif de l'ion sodium à travers la paroi des cellules. Il est très étudié dans le rein pour son importance dans la récupération du sel lors de la concentration de l'urine. Ce canal est présent dans la peau mais sa fonction n'y est pas connue. Des travaux précédents ont pu montrer que les souris où le gène codant pour αENaC a été invalidé présentent un épiderme pathologique, suggérant un rôle dans la peau et plus particulièrement la fonction de barrière de l'épiderme. Le but de cette thèse fut l'étude de la fonction de barrière dans ces souris mutantes, au niveau tissulaire et cellulaire. Dans ce travail, il a été montré que les souris mutantes présentaient une peau plus perméable que celle des animaux contrôles, grâce à une machine mesurant la perte d'eau à travers la peau. Ce défaut n'est visible que 24h après la naissance, mais nous avons pu montrer que les animaux mutants perdaient quasiment 2 fois plus d'eau que les contrôles. Au niveau moléculaire, nous avons pu montrer que ce défaut provenait d'un problème de maturation des lipides qui composent la barrière de la peau. Cette maturation est incomplète vraisemblablement à cause d'un défaut de mouvement des ions dans les couches les plus superficielles de l'épiderme, et cela à cause de l'absence du canal ENaC. En résumé, cette étude démontre clairement qu'ENaC est un acteur important dans la formation de la barrière épithéliale, car la peau des mutants ne s'adapte pas aussi bien que celle des sauvages au nouvel environnement ex utero à cause de la fonction d'ENaC dans les mouvements de sodium au sein même de l'épiderme.

Scnn1 sodium channel gene family in genetically engineered mice.

The amiloride-sensitive epithelial sodium channel is the limiting step in salt absorption. In mice, this channel is composed of three subunits (alpha, beta, and gamma), which are encoded by different genes (Scnn1a, Scnn1b, and Scnn1c, respectively). The functions of these genes were recently investigated in transgenic (knockout) experiments, and the absence of any subunit led to perinatal lethality. More defined phenotypes have been obtained by introducing specific mutations or using transgenic rescue experiments. In this report, these approaches are summarized and a current gene-targeting strategy to obtain conditional inactivation of the channel is illustrated. This latter approach will be indispensable for the investigation of channel function in a wide variety of organ systems.

Comparison of methods for estimation of needle losses in Scots pine following defoliation by Bupalus piniaria

Abstract

Visibility and Speed Estimation of Iowa State Highway Commission Snowplows, HR-174, 1975

Many accidents involving Iowa snowplows have happened in recent years. This study investigated the influence of time of day, sex of subject, type of snowplow sign and snowplow speed on the criteria of oncoming driver reaction time and his estimate of snowplow speed. Film strips were made of a car passing a snow-Plow under various experimental conditions. These experimental movie strips were viewed in the laboratory by college student drivers who were asked to indicate their reaction time to slow down and to estimate the speed of the snowplow being passed. The generally best sign condition for the snowplow was to have a striped rear sign and a speed-proportional flashing light in addition to the standard rotating beacon on top of the truck. Several recommendations were made.

International union of basic and clinical pharmacology. XCI. structure, function, and pharmacology of acid-sensing ion channels and the epithelial Na+ channel.

The epithelial Na(+) channel (ENaC) and the acid-sensing ion channels (ASICs) form subfamilies within the ENaC/degenerin family of Na(+) channels. ENaC mediates transepithelial Na(+) transport, thereby contributing to Na(+) homeostasis and the maintenance of blood pressure and the airway surface liquid level. ASICs are H(+)-activated channels found in central and peripheral neurons, where their activation induces neuronal depolarization. ASICs are involved in pain sensation, the expression of fear, and neurodegeneration after ischemia, making them potentially interesting drug targets. This review summarizes the biophysical properties, cellular functions, and physiologic and pathologic roles of the ASIC and ENaC subfamilies. The analysis of the homologies between ENaC and ASICs and the relation between functional and structural information shows many parallels between these channels, suggesting that some mechanisms that control channel activity are shared between ASICs and ENaC. The available crystal structures and the discovery of animal toxins acting on ASICs provide a unique opportunity to address the molecular mechanisms of ENaC and ASIC function to identify novel strategies for the modulation of these channels by pharmacologic ligands.

Changes in Aortic Pulse Wave Velocity in Hypertension Post-Menopausal Women: Comparison Between Calcium Channel Blocker (CCB) Vs Angiotensin Receptor Blocker (ARB) Regimen

Objective: To compare effects of a non-renin-angiotensin system (RAS) blocker, using a CCB, or a RAS blocker, using an ARB regimen on the arterial stiffness reduction in postmenopausal hypertensive women. Methods: In this prospective study, a total of 125 hypertensive women (age: 61.4_6 yrs; 98% Caucasian; BW: 71.9_14 kg; BMI: 27.3_5 kg/m2; SBP/ DBP: 158_11/92_9 mmHg) were randomized between ARB (valsartan 320mg_HCTZ) and CCB (amlodipine 10mg _ HCTZ). The primary outcome was carotid-femoral pulse wave velocity (PWV) changes after 38 weeks of treatment. Results: There were no significant differences in baseline demographic data between the two groups. Both treatments effectively lowered BP at the end of the study with similar (p>0.05) reductions in the valsartan (_22.9/_10.9 mmHg) and amlodipine based (_25.2/_11.7 mmHg) treatment groups. Despite a lower (p<0.05 for DBP) central SBP/DBP in the CCB group (_19.2/_10.3 mmHg) compared to the valsartan group (_15.7/_7.6 mmHg) at week 38, a similar reduction in carotid-femoral PWV (_1.7 vs _1.9 m/sec; p>0.05) was observed between both groups. The numerically larger BP reduction observed in the CCB group was associated with a much higher incidence of peripheral edema (77% vs 14%) than the valsartan group. Conclusion: In summary, BP lowering in postmenopausal women led to a reduction in arterial stiffness assessed by PWV measurement. Both regimens reduced PWV at 38 weeks of treatment to a similar degree, despite differences in BP lowering suggesting that the effect of RAS blockade to influence PWV may partly be independent of BP.

Estimation du degré de couverture d'un registre pour les cancers notifiés au décès [Evaluation of the comprehensiveness of a cancer register from death certificates].

The comparison of cancer prevalence with cancer mortality can lead under some hypotheses to an estimate of registration rate. A method is proposed, where the cases with cancer as a cause of death are divided into 3 categories: (1) cases already known by the registry (2) unknown cases having occured before the registry creation date (3) unknown cases occuring during the registry operates. The estimate is then the number of cases in the first category divided by the total of those in categories 1 and 3 (these only are to be registered). An application is performed on the data of the Canton de Vaud. Survival rates of the Norvegian Cancer Registry are used for computing the number of unknown cases to be included in second and third category, respectively. The discussion focusses on the possible determinants of the obtained comprehensiveness rates for various cancer sites.

Indian Creek Channel: the evolution & significance of an historic public works administration flood control facility, Council Bluffs, Iowa, 2010

Plagued for nearly a century by the perennial flooding of Indian Creek, the City begins construction on a massive channelization project designed to confine the creek to its banks. Funded largely through a grant from the recently established Public Works Administration (PWA), the Indian Creek Channel, upon its completion two years later, would become the largest PWA undertaking in the State of Iowa. Though it did not completely end flooding in Council Bluffs, construction of the Indian Creek Channel did substantially reduce both the number and severity of the city's subsequent floods. It also profoundly impacted the residential and commercial development of Council Bluffs, as well as the city's sanitary conditions. The effects of the Indian Creek channelization, both practical and historical, are still realized today. In 2009, plans for a City road and bridge construction project at the intersection of North Broadway Street and Kanesville Boulevard proposed to replace a 221-foot-long segment of the Indian Creek Channel with a concrete box culvert. In compliance with the National Historic Preservation Act, a cultural resources study was conducted at the proposed construction site, the findings of which concluded that the historic character of the Indian Creek Channel would be compromised by the impending construction. As a means of mitigating these damages, an agreement was reached among the City, the Iowa State Historic Preservation Office, and the Federal Highway Administration that resulted in detailed research and documentation of the historical significance of the Indian Creek Channel. The findings of that study are summarized in this publication.

The estimation of PMP and PMF on alpine basins in Switzerland

This paper presents a very fine grid hydrological model based on the spatiotemporal repartition of precipitation and on the topography. The goal is to estimate the flood on a catchment area, using a Probable Maximum Precipitation (PMP) leading to a Probable Maximum Flood (PMF). The spatiotemporal distribution of the precipitation was realized using six clouds modeled by the advection-diffusion equation. The equation shows the movement of the clouds over the terrain and also gives the evolution of the rain intensity in time. This hydrological modeling is followed by a hydraulic modeling of the surface and subterranean flows, done considering the factors that contribute to the hydrological cycle, such as the infiltration, the exfiltration and the snowmelt. This model was applied to several Swiss basins using measured rain, with results showing a good correlation between the simulated and observed flows. This good correlation proves that the model is valid and gives us the confidence that the results can be extrapolated to phenomena of extreme rainfall of PMP type. In this article we present some results obtained using a PMP rainfall and the developed model.

Limitations and information needs for engineered nanomaterial-specific exposure estimation and scenarios: recommendations for improved reporting practices

The aim of this paper is to describe the process and challenges in building exposure scenarios for engineered nanomaterials (ENM), using an exposure scenario format similar to that used for the European Chemicals regulation (REACH). Over 60 exposure scenarios were developed based on information from publicly available sources (literature, books, and reports), publicly available exposure estimation models, occupational sampling campaign data from partnering institutions, and industrial partners regarding their own facilities. The primary focus was on carbon-based nanomaterials, nano-silver (nano-Ag) and nano-titanium dioxide (nano-TiO2), and included occupational and consumer uses of these materials with consideration of the associated environmental release. The process of building exposure scenarios illustrated the availability and limitations of existing information and exposure assessment tools for characterizing exposure to ENM, particularly as it relates to risk assessment. This article describes the gaps in the information reviewed, recommends future areas of ENM exposure research, and proposes types of information that should, at a minimum, be included when reporting the results of such research, so that the information is useful in a wider context.