Enhanced diastolic reflections on arterial pressure pulse during exercise recovery

RESUMEDurant la phase de récupération d'un exercice de course à pied d'intensité maximale ou submaximale, une augmentation de la pression artérielle systolique centrale (aortique) résultant de la réflexion des ondes de pouls sur l'arbre vasculaire est constatée chez l'individu en bonne santé. En diastole cependant, l'impact de la réflexion de ces ondes de pouls sur la pression centrale demeure inconnu durant la récupération d'un exercice.Nous avons évalué les ondes de pouls centrales systolique et diastolique chez onze athlètes d'endurance durant la phase de récupération d'un exercice de course à pied dans des conditions d'effort maximal (sur tapis de course) et lors d'un effort submaximal lors d'une course à pied de 4000 mètres en plein air sur terrain mixte.Pour chaque sujet et lors des deux exercices, l'onde de pouls a été mesurée au niveau radial par tonométrie d'aplanation durant une phase de repos précédant l'exercice, puis à 5, 15, 25, 35 et 45 minutes après la fin de l'exercice. En utilisant une fonction mathématique de transfert, l'onde de pouls centrale a été extrapolée à partir de l'onde de pouls radiale. En compilant la forme de l'onde de pouls centrale avec une mesure simultanée de la pression artérielle brachiale, un index d'augmentation de l'onde de pouls en systole (Alx) et en diastole (Als) peut être calculé, reflétant l'augmentation des pressions résultant de la réflexion des ondes sur l'arbre vasculaire périphérique.A 5 minutes de la fin de l'exercice, les deux index ont été mesurés moindres que ceux mesurés lors de la phase précédant celui-ci. Lors des mesures suivantes, Alx est resté bas, alors que Aid a progressivement augmenté pour finalement dépasser la valeur de repos après 45 minutes de récupération. Le même phénomène a été constaté pour les deux modalités d'exercice (maximal ou submaximal). Ainsi, au-delà de quelques minutes de récupération après un exercice de course d'intensité maximale ou submaximale, nous avons montré par ces investigations que les ondes de pouls réfléchies en périphérie augmentent de façon sélective la pression centrale en diastole chez l'athlète d'endurance.ABSTRACTDuring recovery from a maximal or submaximal aerobic exercise, augmentation of central (aortic) systolic pressure by reflected pressure waves is blunted in healthy humans. However, the extent to which reflected pressure waves modify the central pulse in diastole in these conditions remains unknown. We evaluated systolic and diastolic central reflected waves in 11 endurance-trained athletes on recovery from a maximal running test on a treadmill (treadmill-max) and a 4000m run in field conditions. On both occasions in each subject, the radial pulse was recorded with applanation tonometry in the resting preexercise state and then 5, 15, 25, 35, and 45 minutes after exercise termination. From the central waveform, as reconstructed by application of a generalized transfer function, we computed a systolic (Alx) and a diastolic index (Aid) of pressure augmentation by reflections. At 5 minutes, both indices were below preexercise. At further time-points, Alx remained low, while Aid progressively increased, to overshoot above preexercise at 45 minutes. The same behavior was observed with both exercise types. Beyond the first few minutes of recovery following either maximal or submaximal aerobic exercise, reflected waves selectively augment the central pressure pulse in diastole, at least in endurance- trained athletes.

The CNGCb and CNGCd genes from Physcomitrella patens moss encode for thermosensory calcium channels responding to fluidity changes in the plasma membrane.

Land plants need precise thermosensors to timely establish molecular defenses in anticipation of upcoming noxious heat waves. The plasma membrane-embedded cyclic nucleotide-gated Ca(2+) channels (CNGCs) can translate mild variations of membrane fluidity into an effective heat shock response, leading to the accumulation of heat shock proteins (HSP) that prevent heat damages in labile proteins and membranes. Here, we deleted by targeted mutagenesis the CNGCd gene in two Physcomitrella patens transgenic moss lines containing either the heat-inducible HSP-GUS reporter cassette or the constitutive UBI-Aequorin cassette. The stable CNGCd knockout mutation caused a hyper-thermosensitive moss phenotype, in which the heat-induced entry of apoplastic Ca(2+) and the cytosolic accumulation of GUS were triggered at lower temperatures than in wild type. The combined effects of an artificial membrane fluidizer and elevated temperatures suggested that the gene products of CNGCd and CNGCb are paralogous subunits of Ca(2+)channels acting as a sensitive proteolipid thermocouple. Depending on the rate of temperature increase, the duration and intensity of the heat priming preconditions, terrestrial plants may thus acquire an array of HSP-based thermotolerance mechanisms against upcoming, otherwise lethal, extreme heat waves.

Estimation of inelastic seismic material properties of a surgical sea-bed from multi-component marine seismic data

To date, state-of-the-art seismic material parameter estimates from multi-component sea-bed seismic data are based on the assumption that the sea-bed consists of a fully elastic half-space. In reality, however, the shallow sea-bed generally consists of soft, unconsolidated sediments that are characterized by strong to very strong seismic attenuation. To explore the potential implications, we apply a state-of-the-art elastic decomposition algorithm to synthetic data for a range of canonical sea-bed models consisting of a viscoelastic half-space of varying attenuation. We find that in the presence of strong seismic attenuation, as quantified by Q-values of 10 or less, significant errors arise in the conventional elastic estimation of seismic properties. Tests on synthetic data indicate that these errors can be largely avoided by accounting for the inherent attenuation of the seafloor when estimating the seismic parameters. This can be achieved by replacing the real-valued expressions for the elastic moduli in the governing equations in the parameter estimation by their complex-valued viscoelastic equivalents. The practical application of our parameter procedure yields realistic estimates of the elastic seismic material properties of the shallow sea-bed, while the corresponding Q-estimates seem to be biased towards too low values, particularly for S-waves. Given that the estimation of inelastic material parameters is notoriously difficult, particularly in the immediate vicinity of the sea-bed, this is expected to be of interest and importance for civil and ocean engineering purposes.

Propagation velocity kinetics and repolarization alternans in a free-behaving sheep model of pacing-induced atrial fibrillation.

AIMS: Experimental models have reported conflicting results regarding the role of dispersion of repolarization in promoting atrial fibrillation (AF). Repolarization alternans, a beat-to-beat alternation in action potential duration, enhances dispersion of repolarization when propagation velocity is involved. METHODS AND RESULTS: In this work, original electrophysiological parameters were analysed to study AF susceptibility in a chronic sheep model of pacing-induced AF. Two pacemakers were implanted, each with a single right atrial lead. Right atrial depolarization and repolarization waves were documented at 2-week intervals. A significant and gradual decrease in the propagation velocity at all pacing rates and in the right atrial effective refractory period (ERP) was observed during the weeks of burst pacing before sustained AF developed when compared with baseline conditions. Right atrial repolarization alternans was observed, but because of the development of 2/1 atrioventricular block with far-field ventricular interference, its threshold could not be precisely measured. Non-sustained AF was not observed at baseline, but appeared during the electrical remodelling in association with a decrease in both ERP and propagation velocity. CONCLUSION: We report here on the feasibility of measuring ERP, atrial repolarization alternans, and propagation velocity kinetics and their potential in predicting susceptibility to AF in a free-behaving model of pacing-induced AF using the standard pacemaker technology.

Early-onset acquired epileptic aphasia (Landau-Kleffner syndrome, LKS) and regressive autistic disorders with epileptic EEG abnormalities: the continuing debate.

Early-onset acquired epileptic aphasia (Landau-Kleffner syndrome) may present as a developmental language disturbance and the affected child may also exhibit autistic features. Landau-Kleffner is now seen as the rare and severe end of a spectrum of cognitive-behavioural symptoms that can be seen in idiopathic (genetic) focal epilepsies of childhood, the benign end being the more frequent typical rolandic epilepsy. Several recent studies show that many children with rolandic epilepsy have minor developmental cognitive and behavioural problems and that some undergo a deterioration (usually temporary) in these domains, the so-called "atypical" forms of the syndrome. The severity and type of deterioration correlate with the site and spread of the epileptic spikes recorded on the electroencephalogram within the perisylvian region, and continuous spike-waves during sleep (CSWS) frequently occur during this period of the epileptic disorder. Some of these children have more severe preexisting communicative and language developmental disorders. If early stagnation or regression occurs in these domains, it presumably reflects epileptic activity in networks outside the perisylvian area, i.e. those involved in social cognition and emotions. Longitudinal studies will be necessary to find out if and how much the bioelectrical abnormalities play a causal role in these subgroup of children with both various degrees of language and autistic regression and features of idiopathic focal epilepsy. One has to remember that it took nearly 40 years to fully acknowledge the epileptic origin of aphasia in Landau-Kleffner syndrome and the milder acquired cognitive problems in rolandic epilepsies.

Metamorphism and kinetics in the Torres del Paine contact aureole

Contact aureoles provide an excellent geologic environment to study the mechanisms of metamorphic reactions in a natural system. The Torres del Paine (TP) intrusion is one of the most spectacular natural laboratories because of its excellent outcrop conditions. It formed in a period from 12.59 to 12.43 Ma and consists of three large granite and four smaller mafic batches. The oldest granite is on top, the youngest at the bottom of the granitic complex, and the granites overly the mafic laccolith. The TP intruded at a depth of 2-3 km into regional metamorphic anchizone to greenschist facies pelites, sandstones, and conglomerates of the Cerro Toro and Punta Barrosa formations. It formed a thin contact aureole of 150-400 m width. This thesis focuses on the reaction kinetics of the mineral cordierite in the contact aureole using quantitative textural analysis methods. First cordierite was formed from chlorite break¬down (zone I, ca. 480 °C, 750 bar). The second cordierite forming reaction was the muscovite break-down, which is accompanied by a modal decrease in biotite and the appearance of k- feldspar (zone II, 540-550 °C, 750 bar). Crystal sizes of the roundish, poikiloblastic cordierites were determined from microscope thin section images by manually marking each crystal. Images were then automatically processed with Matlab. The correction for the intersection probability of each crystal radius yields the crystal size distribution in the rock. Samples from zone I below the laccolith have the largest crystals (0.09 mm). Cordierites from zone II are smaller, with a maximum crystal radius of 0.057 mm. Rocks from zone II have a larger number of small cordierite crystals than rocks from zone I. A combination of these quantitative analysis with numerical modeling of nucleation and growth, is used to infer nucleation and growth parameters which are responsible for the observed mineral textures. For this, the temperature-time paths of the samples need to be known. The thermal history is complex because the main body of the intrusion was formed by several intrusive batches. The emplacement mechanism and duration of each batch can influence the thermal structure in the aureole. A possible subdivision of batches in smaller increments, so called pulses, will focus heat at the side of the intrusion. Focusing all pulses on one side increases the contact aureole size on that side, but decreases it on the other side. It forms a strongly asymmetric contact aureole. Detailed modeling shows that the relative thicknesses of the TP contact aureole above and below the intrusion (150 and 400 m) are best explained by a rapid emplacement of at least the oldest granite batch. Nevertheless, temperatures are significantly too low in all models, compared to observed mineral assemblages in the hornfelses. Hence, an other important thermal mechanisms needs to take place in the host rock. Clastic minerals in the immature sediments outside the contact aureole are hydrated due to small amounts of expelled fluids during contact metamorphism. This leads to a temperature increase of up to 50 °C. The origin of fluids can be traced by stable isotopes. Whole rock stable isotope data (6D and δ180) and chlorine concentrations in biotite document that the TP intrusion induced only very small amounts of fluid flow. Oxygen whole rock data show δ180 values between 9.0 and 10.0 %o within the first 5 m of the contact. Values increase to 13.0 - 15.0 %o further away from the intrusion. Whole rock 6D values display a more complex zoning. First, host rock values (-90 to -70 %o) smoothly decrease towards the contact by ca. 20 %o, up to a distance of ca. 150 m. This is followed by an increase of ca. 20 %o within the innermost 150 m of the aureole (-97.0 to -78 %o at the contact). The initial decrease in 6D values is interpreted to be due to Rayleigh fractionation accompanying the dehydration reactions forming cordierite, while the final increase reflects infiltration of water-rich fluids from the intrusion. An over-estimate on the quantity and the corresponding thermal effect yields a temperature increase of less than 30 °C. This suggests that fluid flow might have contributed only for a small amount to the thermal evolution of the system. A combination of the numerical growth model with the thermal model, including the hydration reaction enthalpies but neglecting fluid flow and incremental growth, can be used to numerically reproduce the observed cordierite textures in the contact aureole. This yields kinetic parameters which indicate fast cordierite crystallization before the thermal peak in the inner aureole, and continued reaction after the thermal peak in the outermost aureole. Only small temperature dependencies of the kinetic parameters seem to be needed to explain the obtained crystal size data. - Les auréoles de contact offrent un cadre géologique privilégié pour l'étude des mécanismes de réactions métamorphiques associés à la mise en place de magmas dans la croûte terrestre. Par ses conditions d'affleurements excellentes, l'intrusion de Torres del Paine représente un site exceptionnel pour améliorer nos connaissances de ces processus. La formation de cette intrusion composée de trois injections granitiques principales et de quatre injections mafiques de volume inférieur couvre une période allant de 12.50 à 12.43 Ma. Le plus vieux granite forme la partie sommitale de l'intrusion alors que l'injection la plus jeune s'observe à la base du complexe granitique; les granites recouvrent la partie mafique du laccolite. L'intrusion du Torres del Paine s'est mise en place a 2-3 km de profondeur dans un encaissant métamorphique. Cet encaissant est caractérisé par un métamorphisme régional de faciès anchizonal à schiste vert et est composé de pélites, de grès, et des conglomérats des formations du Cerro Toro et Punta Barrosa. La mise en place des différentes injections granitiques a généré une auréole de contact de 150-400 m d'épaisseur autour de l'intrusion. Cette thèse se concentre sur la cinétique de réaction associée à la formation de la cordiérite dans les auréoles de contact en utilisant des méthodes quantitatives d'analyses de texture. On observe plusieurs générations de cordiérite dans l'auréole de contact. La première cordiérite est formée par la décomposition de la chlorite (zone I, environ 480 °C, 750 bar), alors qu'une seconde génération de cordiérite est associée à la décomposition de la muscovite, laquelle est accompagnée par une diminution modale de la teneur en biotite et l'apparition de feldspath potassique (zone II, 540-550 °C, 750 bar). Les tailles des cristaux de cordiérites arrondies et blastic ont été déterminées en utilisant des images digitalisées des lames minces et en marquant individuellement chaque cristal. Les images sont ensuite traitées automatiquement à l'aide du programme Matlab. La correction de la probabilité d'intersection en fonction du rayon des cristaux permet de déterminer la distribution de la taille des cristaux dans la roche. Les échantillons de la zone I, en dessous du lacolite, sont caractérisés par de relativement grands cristaux (0.09 mm). Les cristaux de cordiérite de la zone II sont plus petits, avec un rayon maximal de 0.057 mm. Les roches de la zone II présentent un plus grand nombre de petits cristaux de cordiérite que les roches de la zone I. Une combinaison de ces analyses quantitatives avec un modèle numérique de nucléation et croissance a été utilisée pour déduire les paramètres de nucléation et croissance contrôlant les différentes textures minérales observées. Pour développer le modèle de nucléation et de croissance, il est nécessaire de connaître le chemin température - temps des échantillons. L'histoire thermique est complexe parce que l'intrusion est produite par plusieurs injections successives. En effet, le mécanisme d'emplace¬ment et la durée de chaque injection peuvent influencer la structure thermique dans l'auréole. Une subdivision des injections en plus petits incréments, appelés puises, permet de concentrer la chaleur dans les bords de l'intrusion. Une mise en place préférentielle de ces puises sur un côté de l'intrusion modifie l'apport thermique et influence la taille de l'auréole de contact produite, auréole qui devient asymétrique. Dans le cas de la première injection de granite, une modélisation détaillée montre que l'épaisseur relative de l'auréole de contact de Torres del Paine au-dessus et en dessous de l'intrusion (150 et 400 m) est mieux expliquée par un emplacement rapide du granite. Néanmoins, les températures calculées dans l'auréole de con¬tact sont trop basses pour que les modèles thermiques soient cohérants par rapport à la taille de cette auréole. Ainsi, un autre mecanisme exothermique est nécessaire pour permettre à la roche encais¬sante de produire les assemblages observés. L'observation des roches encaissantes entourant les granites montre que les minéraux clastiques dans les sédiments immatures au-dehors de l'auréole sont hydratés suite à la petite quantité de fluide expulsée durant le métamorphisme de contact et/ou la mise en place des granites. Les réactions d'hydratation peuvent permettre une augmentation de la température jusqu'à 50 °C. Afin de déterminer l'origine des fluides, une étude isotopique de roches de l'auréole de contact a été entreprise. Les isotopes stables d'oxygène et d'hydrogène sur la roche totale ainsi que la concentration en chlore dans la biotite indiquent que la mise en place des granites du Torres del Paine n'induit qu'une circulation de fluide limitée. Les données d'oxygène sur roche totale montrent des valeurs δ180 entre 9.0 et 10.0%o au sein des cinq premiers mètres du contact. Les valeurs augmentent jusqu'à 13.0 - 15.0 plus on s'éloigne de l'intrusion. Les valeurs 5D sur roche totale montrent une zonation plus complexe. Les valeurs de la roche encaissante (-90 à -70%o) diminuent progressivement d'environ 20%o depuis l'extérieur de l'auréole jusqu'à une distance d'environ 150 m du granite. Cette diminution est suivie par une augmentation d'environ 20%o au sein des 150 mètres les plus proches du contact (-97.0 à -78%o au contact). La diminution initiale des valeurs de 6D est interprétée comme la conséquence du fractionnement de Rayleigh qui accompagne les réactions de déshydratation formant la cordiérite, alors que l'augmentation finale reflète l'infiltration de fluide riche en eau venant de l'intrusion. A partir de ces résultats, le volume du fluide issu du granite ainsi que son effet thermique a pu être estimé. Ces résultats montrent que l'augmentation de température associée à ces fluides est limitée à un maximum de 30 °C. La contribution de ces fluides dans le bilan thermique est donc faible. Ces différents résultats nous ont permis de créer un modèle thermique associé à la for¬mation de l'auréole de contact qui intègre la mise en place rapide du granite et les réactions d'hydratation lors du métamorphisme. L'intégration de ce modèle thermique dans le modèle numérique de croissance minérale nous permet de calculer les textures des cordiérites. Cepen¬dant, ce modèle est dépendant de la vitesse de croissance et de nucléation de ces cordiérites. Nous avons obtenu ces paramètres en comparant les textures prédites par le modèle et les textures observées dans les roches de l'auréole de contact du Torres del Paine. Les paramètres cinétiques extraits du modèle optimisé indiquent une cristallisation rapide de la cordiérite avant le pic thermique dans la partie interne de l'auréole, et une réaction continue après le pic thermique dans la partie la plus externe de l'auréole. Seules de petites dépendances de température des paramètres de cinétique semblent être nécessaires pour expliquer les don¬nées obtenues sur la distribution des tailles de cristaux. Ces résultats apportent un éclairage nouveau sur la cinétique qui contrôle les réactions métamorphiques.

ECG interpretation during the acute phase of coronary syndromes: in need of improvement?

QUESTION UNDER STUDY: Emergency room (ER) interpretation of the ECG is critical to assessment of patients with acute coronary syndromes (ACS). Our aim was to assess its reliability in our institution, a tertiary teaching hospital. METHODS: Over a 6-month period all consecutive patients admitted for ACS were included in the study. ECG interpretation by emergency physicians (EPs) was recorded on a preformatted sheet and compared with the interpretation of two specialist physicians (SPs). Discrepancies between the 2 specialists were resolved by an ECG specialist. RESULTS: Over the 6-month period, 692 consecutive patients were admitted with suspected ACS. ECG interpretation was available in 641 cases (93%). Concordance between SPs was 87%. Interpretation of normality or abnormality of the ECG was concordant between EPs and SPs in 475 cases (74%, kappa = 0.51). Interpretation of ischaemic modifications was concordant in 69% of cases, and as many ST segment elevations were unrecognised as overdiagnosed (5% each). The same findings occurred for ST segment depressions and negative T waves (12% each). CONCLUSIONS: Interpretation of the ECG recorded during ACS by 2 SPs was discrepant in 13% of cases. Similarly, EP interpretation was discrepant from SP interpretation in 25% of cases, equally distributed between over- and underdiagnosing of ischaemic changes. The clinical implications and impact of medical education on ECG interpretation require further study.

Clinical neurophysiological assessment of sepsis-associated brain dysfunction: a systematic review.

IntroductionSeveral studies have reported the presence of electroencephalography (EEG) abnormalities or altered evoked potentials (EPs) during sepsis. However, the role of these tests in the diagnosis and prognostic assessment of sepsis-associated encephalopathy remains unclear.MethodsWe performed a systematic search for studies evaluating EEG and/or EPs in adult (¿18 years) patients with sepsis-associated encephalopathy. The following outcomes were extracted: a) incidence of EEG/EP abnormalities; b) diagnosis of sepsis-associated delirium or encephalopathy with EEG/EP; c) outcome.ResultsAmong 1976 citations, 17 articles met the inclusion criteria. The incidence of EEG abnormalities during sepsis ranged from 12% to 100% for background abnormality and 6% to 12% for presence of triphasic waves. Two studies found that epileptiform discharges and electrographic seizures were more common in critically ill patients with than without sepsis. In one study, EEG background abnormalities were related to the presence and the severity of encephalopathy. Background slowing or suppression and the presence of triphasic waves were also associated with higher mortality. A few studies demonstrated that quantitative EEG analysis and EP could show significant differences in patients with sepsis compared to controls but their association with encephalopathy and outcome was not evaluated.ConclusionsAbnormalities in EEG and EPs are present in the majority of septic patients. There is some evidence to support EEG use in the detection and prognostication of sepsis-associated encephalopathy, but further clinical investigation is needed to confirm this suggestion.

Stoneley wave modeling in heterogeneous porous media with viscous pore fluids

We implemented Biot-type porous wave equations in a pseudo-spectral numerical modeling algorithm for the simulation of Stoneley waves in porous media. Fourier and Chebyshev methods are used to compute the spatial derivatives along the horizontal and vertical directions, respectively. To prevent from overly short time steps due to the small grid spacing at the top and bottom of the model as a consequence of the Chebyshev operator, the mesh is stretched in the vertical direction. As a large benefit, the Chebyshev operator allows for an explicit treatment of interfaces. Boundary conditions can be implemented with a characteristics approach. The characteristic variables are evaluated at zero viscosity. We use this approach to model seismic wave propagation at the interface between a fluid and a porous medium. Each medium is represented by a different mesh and the two meshes are connected through the above described characteristics domain-decomposition method. We show an experiment for sealed pore boundary conditions, where we first compare the numerical solution to an analytical solution. We then show the influence of heterogeneity and viscosity of the pore fluid on the propagation of the Stoneley wave and surface waves in general.

Long-term outcome after cognitive and behavioral regression in non-lesional epilepsy with CSWS

Purpose: To present the long-term outcome (LTO) of 10 adolescents and young adults with documented cognitive and behavioral regression as children due to non-lesional focal, mainly frontal epilepsy with continuous spike-waves during slow wave sleep (CSWS). Method: Past medical and EEG data of all patients were reviewed and neuropsychological tests exploring main cognitive functions were administered. Result: After a mean duration of follow-up of 15.6 years (range 8-23 years), none of the 10 patients had recovered fully, but four regained borderline to normal intelligence and were almost independent. Patients with prolonged global intellectual regression had the worst outcome, whereas those with more specific and short-lived deficits recovered best. The marked behavioral disorders that were so disturbing during the active period (AP) resolved in all but one patient. Executive functions were neither severely nor homogenously affected. Three patients with a frontal syndrome during the AP disclosed only mild residual executive and social cognition deficits. The main cognitive gains occurred shortly after the AP, but qualitative improvements continued to occur. LTO correlated best with duration of CSWS. Conclusion: Our findings emphasize that cognitive recovery after cessation of CSWS depends on the severity and duration of the initial regression. None of our patients had major executive and social cognition deficits with preserved intelligence as reported in adults with destructive lesions of the frontal lobes during childhood. Early recognition of epilepsy with CSWS and rapid introduction of effective therapy are crucial for a best possible outcome.

Pulse wave analysis of aortic pressure: diastole should also be considered.

BACKGROUND: : The systolic augmentation index (sAix), calculated from the central aortic pulse wave (reconstructed from the noninvasive recording of the radial pulse with applanation tonometry), is widely used as a simple index of central arterial stiffness, but has the disadvantage of also being influenced by the timing of the reflected with respect to the forward pressure wave, as shown by its inverse dependence on heart rate (HR). During diastole, the central aortic pulse also contains reflected waves, but their relationship to arterial stiffness and HR has not been studied. METHODS: : In 48 men and 45 women, all healthy, with ages ranging from 19 to 70 years, we measured pulse wave velocity (PWV, patients supine), a standard evaluator of arterial stiffness, and carried out radial applanation tonometry (patients sitting and supine). The impact of reflected waves on the diastolic part of the aortic pressure waveform was quantified in the form of a diastolic augmentation index (dAix). RESULTS: : Across ages, sexes, and body position, there was an inverse relationship between the sAix and the dAix. When PWV and HR were added as covariates to a prediction model including age, sex and body position as main factors, the sAix was directly related to PWV (P < 0.0001) and inversely to HR (P < 0.0001). With the same analysis, the dAix was inversely related to PWV (P < 0.0001) and independent of HR (P = 0.52). CONCLUSION: : The dAix has the same degree of linkage to arterial stiffness as the more conventional sAix, while being immune to the confounding effect of HR. The quantification of diastolic aortic pressure augmentation by reflected waves could be a useful adjunct to pulse wave analysis.

Twitch and M-wave potentiation induced by intermittent maximal voluntary quadriceps contractions: Differences between direct quadriceps and femoral nerve stimulation.

Introduction: To investigate differences in twitch and M-wave potentiation in the quadriceps femoris when electrical stimulation is applied over the quadriceps muscle belly versus the femoral nerve trunk. Methods: M-waves and mechanical twitches were evoked using direct quadriceps muscle and femoral nerve stimulation between 48 successive isometric maximal voluntary contractions (MVC) from 10 young, healthy subjects. Potentiation was investigated by analyzing the changes in M-wave amplitude recorded from the vastus medialis (VM) and vastus lateralis (VL) muscles and in quadriceps peak twitch force. Results: Potentiation of twitch, VM M-wave, and VL M-wave were greater for femoral nerve than for direct quadriceps stimulation (P<0.05). Despite a 50% decrease in MVC force, the amplitude of the M-waves increased significantly during exercise. Conclusions: In addition to enhanced electrogenic Na(+) -K(+) pumping, other factors (such as synchronization in activation of muscle fibers and muscle architectural properties) might significantly influence the magnitude of M-wave enlargement. © 2013 Wiley Periodicals, Inc.

Dynamic social representations of the 2009 H1N1 pandemic: Shifting patterns of sense-making and blame

We investigate dynamics of public perceptions of the 2009 H1N1 influenza pandemic to understand changing patterns of sense-making and blame regarding the outbreak of emerging infectious diseases. We draw on social representation theory combined with a dramaturgical perspective to identify changes in how various collectives are depicted over the course of the pandemic, according to three roles: heroes, villains and victims. Quantitative results based on content analysis of three cross-sectional waves of interviews show a shift from mentions of distant collectives (e.g., far-flung countries) at Wave 1 to local collectives (e.g., risk groups) as the pandemic became of more immediate concern (Wave 2) and declined (Wave 3). Semi-automated content analysis of media coverage shows similar results. Thematic analyses of the discourse associated with collectives revealed that many were consistently perceived as heroes, villains and victims.