Brownian motion exhibiting absolute negative mobility

We consider a single Brownian particle in a spatially symmetric, periodic system far from thermal equilibrium. This setup can be readily realized experimentally. Upon application of an external static force F, the average particle velocity is negative for F>0 and positive for F<0 (absolute negative mobility).Comment: 4 pages, 3 figures, to be published in PR

Disorder Induced Diffusive Transport In Ratchets

The effects of quenched disorder on the overdamped motion of a driven particle on a periodic, asymmetric potential is studied. While for the unperturbed potential the transport is due to a regular drift, the quenched disorder induces a significant additional chaotic ``diffusive'' motion. The spatio-temporal evolution of the statistical ensemble is well described by a Gaussian distribution, implying a chaotic transport in the presence of quenched disorder.Comment: 10 pages, 4 EPS figures; submitted to Phys. Rev. Letter

Severe Aortic Stenosis and Myocardial Function: Diagnostic and Prognostic Usefulness of Ultrasonic Integrated Backscatter Analysis

Background— The aim of this study was to assess the myocardial reflectivity pattern in severe aortic valve stenosis through the use of integrated backscatter (IBS) analysis. Patients with aortic stenosis (AS) were carefully selected in the Department of Cardiology. Methods and Results— Thirty-five subjects (AS: valve orifice ≤1 cm2; 12 female; mean age, 71.8±6.2 years) and 25 healthy subjects were studied. All subjects of the study had conventional 2D-Doppler echocardiography and IBS. Backscatter signal was sampled at the septum and posterior wall levels. Patients with AS were divided into 2 groups: 16 patients with initial signs of congestive heart failure and a depressed left ventricular systolic function (DSF) (ejection fraction [EF] range, 35% to 50%) and 19 asymptomatic patients with normal left ventricular systolic function (NSF) (EF >50%). Myocardial echo intensity (pericardium related) was significantly higher at the septum and posterior wall levels in DSF than in NSF and in control subjects. IBS variation, as an expression of variation of the signal, appeared to be significantly lower in AS with DSF than in NSF and in control subjects, at both the septum and posterior wall levels. Patients with DSF underwent aortic valve replacement, and, during surgical intervention, a septal myocardial biopsy was made for evaluation of myocardium/fibrosis ratio. Abnormally increased echo intensity was detected in left ventricular pressure overload by severe aortic stenosis and correlated with increase of myocardial collagen content (operating biopsy). Conclusions— One year after aortic valve replacement, we observed a significant reduction of left ventricular mass, and, only if pericardial indexed IBS value (reduction of interstitial fibrosis) decreased, it was possible to observe an improvement of EF and of IBS variation

Force and Motion Generation of Molecular Motors: A Generic Description

We review the properties of biological motor proteins which move along linear filaments that are polar and periodic. The physics of the operation of such motors can be described by simple stochastic models which are coupled to a chemical reaction. We analyze the essential features of force and motion generation and discuss the general properties of single motors in the framework of two-state models. Systems which contain large numbers of motors such as muscles and flagella motivate the study of many interacting motors within the framework of simple models. In this case, collective effects can lead to new types of behaviors such as dynamic instabilities of the steady states and oscillatory motion.Comment: 29 pages, 9 figure

Caveolin contributes to the modulation of basal and β-adrenoceptor stimulated function of the adult rat ventricular myocyte by simvastatin: A novel pleiotropic effect

The number of people taking statins is increasing across the globe, highlighting the Importance of fully understanding statins effects on the cardiovascular system. The beneficial impact of statins extends well beyond regression of atherosclerosis to include direct effects on tissues of the cardiovascular system (pleiotropic effects). Pleiotropic effects on the cardiac myocyte are often overlooked. Here we consider the contribution of the caveolin protein, whose expression and cellular distribution is dependent on cholesterol, to statin effects on the cardiac myocyte. Caveolin is a structural and regulatory component of caveolae, and is a key regulator of cardiac contractile function and adrenergic responsiveness. We employed an experimental model in which inhibition of myocyte HMG CoA reductase could be studied in the absence of paracrine influences from non-myocyte cells. Adult rat ventricular myocytes were treated with 10 μM simvastatin for 2 days. Simvastatin treatment reduced myocyte cholesterol, caveolin 3 and caveolar density. Negative inotropic and positive lusitropic effects (with corresponding changes in [Ca2]¡) were seen in statin-treated cells. Simvastatin significantly potentiated the inotropic response to β2-, but not β1-, adrenoceptor stimulation. Under conditions of β2-adrenoceptor stimulation, phosphorylation of phospholamban at Ser16and troponin I at Ser23/24was enhanced with statin treatment. Simvastatin increased NO production without significant effects on eNOS expression or phosphorylation (Ser1177), consistent with the reduced expression of caveolin 3, its constitutive Inhibitor. In conclusion, statin treatment can reduce caveolin 3 expression, with functional consequences consistent with the known role of caveolae in the cardiac cell. These data are likely to be of significance, particularly during the early phases of statin treatment, and in patients with heart failure who have altered ß-adrenoceptor signalling. In addition, as caveolin is ubiquitously expressed and has myriad tissue-specific functions, the impact of statin-dependent changes in caveolin is likely to have many other functional sequelae

Comparison between Airway Responses to High versus Low Molecular Weight Compounds in Occupational Asthma

Occupational asthma (OA) is a heterogeneous disease, and the characteristics of the sensitizer responsible for OA may induce different clinical, functional, and biological manifestations. We examined the characteristics of 74 patients with OA induced by low molecular weight compounds (LMWC) or by high molecular weight compounds (HMWC) and diagnosed by specific inhalation challenge (SIC). Patients with OA induced by LMWC had a longer occupational exposure before the beginning of symptoms, a lower sputum eosinophilia, and a higher prevalence of late airway response (LAR), in comparison with patients with OA induced by HMWC. Pulmonary function tended to be poorer and atopy tended to be less frequent in LMWC-induced OA than in HMWC-induced OA. These data confirm and extend previous observations showing that the characteristics of the specific sensitizer inducing OA may determine different clinical, functional, and biological features, probably related to the difference pathogenetic mechanisms underlying these different types of OA

Early and late improvement of global and regional left ventricular function after transcatheter aortic valve implantation in patients with severe aortic stenosis: an echocardiographic study.

The recent development of transcatheter aortic valve implantation (TAVI) for severe aortic stenosis (AS) treatment offers a viable option for high-risk patient categories. Our aim is to evaluate whether 2D strain and strain rate can detect subtle improvement in global and regional LV systolic function immediately after TAVI. 2D conventional and 2D strain (speckle analysis) echocardiography was performed before, at discharge and after three months in thirty three patients with severe AS. After TAVI, we assessed by conventional echocardiography an immediate reduction of transaortic peak pressure gradient (p<0.0001), of mean pressure gradient (p<0.0001) and a concomitant increase in aortic valve area (AVA: 1.08±0.31 cm(2)/m(2); p<0.0001). 2D longitudinal systolic strain showed a significant improvement in all patients, both at septal and lateral level, as early as 72 h after procedure (septal: -14.2±5.1 vs -16.7±3.7%, p<0.001; lateral: -9.4±3.9 vs -13.1±4.5%, p<0.001; respectively) and continued at 3 months follow-up (septal: -18.1±4.6%, p<0.0001; lateral: -14.8±4.4%, p<0.0001; respectively). Conventional echocardiography after TAVI proved a significant reduction of LV end-systolic volume and of LV mass with a mild improvement of LV ejection fraction (EF) (51.2±11.8 vs 52.9±6.4%; p<0.02) only after three months. 2D strain seems to be able to detect subtle changes in LV systolic function occurring early and late after TAVI in severe AS, while all conventional echo parameters seem to be less effective for this purpose. Further investigations are needed to prove the real prognostic impact of these echocardiographic findings