Non-monotonic variation with salt concentration of the second virial coefficient in protein solutions

The osmotic virial coefficient $B_2$ of globular protein solutions is calculated as a function of added salt concentration at fixed pH by computer simulations of the ``primitive model''. The salt and counter-ions as well as a discrete charge pattern on the protein surface are explicitly incorporated. For parameters roughly corresponding to lysozyme, we find that $B_2$ first decreases with added salt concentration up to a threshold concentration, then increases to a maximum, and then decreases again upon further raising the ionic strength. Our studies demonstrate that the existence of a discrete charge pattern on the protein surface profoundly influences the effective interactions and that non-linear Poisson Boltzmann and Derjaguin-Landau-Verwey-Overbeek (DLVO) theory fail for large ionic strength. The observed non-monotonicity of $B_2$ is compared to experiments. Implications for protein crystallization are discussed.Comment: 43 pages, including 17 figure

Adsorption of mono- and multivalent cat- and anions on DNA molecules

Adsorption of monovalent and multivalent cat- and anions on a deoxyribose nucleic acid (DNA) molecule from a salt solution is investigated by computer simulation. The ions are modelled as charged hard spheres, the DNA molecule as a point charge pattern following the double-helical phosphate strands. The geometrical shape of the DNA molecules is modelled on different levels ranging from a simple cylindrical shape to structured models which include the major and minor grooves between the phosphate strands. The densities of the ions adsorbed on the phosphate strands, in the major and in the minor grooves are calculated. First, we find that the adsorption pattern on the DNA surface depends strongly on its geometrical shape: counterions adsorb preferentially along the phosphate strands for a cylindrical model shape, but in the minor groove for a geometrically structured model. Second, we find that an addition of monovalent salt ions results in an increase of the charge density in the minor groove while the total charge density of ions adsorbed in the major groove stays unchanged. The adsorbed ion densities are highly structured along the minor groove while they are almost smeared along the major groove. Furthermore, for a fixed amount of added salt, the major groove cationic charge is independent on the counterion valency. For increasing salt concentration the major groove is neutralized while the total charge adsorbed in the minor groove is constant. DNA overcharging is detected for multivalent salt. Simulations for a larger ion radii, which mimic the effect of the ion hydration, indicate an increased adsorbtion of cations in the major groove.Comment: 34 pages with 14 figure

Physical therapy vs. internet-based exercise training (PATH-IN) for patients with knee osteoarthritis: study protocol of a randomized controlled trial

Abstract Background Physical activity improves pain and function among individuals with knee osteoarthritis (OA), but most people with this condition are inactive. Physical therapists play a key role in helping people with knee OA to increase appropriate physical activity. However, health care access issues, financial constraints, and other factors impede some patients from receiving physical therapy (PT) for knee OA. A need exists to develop and evaluate other methods to provide physical activity instruction and support to people with knee OA. This study is examining the effectiveness of an internet-based exercise training (IBET) program designed for knee OA, designed by physical therapists and other clinicians. Methods/Design This is a randomized controlled trial of 350 participants with symptomatic knee OA, allocated to three groups: IBET, standard PT, and a wait list (WL) control group (in a 2:2:1 ratio, respectively). The study was funded by the Patient Centered Outcomes Research Institute, which conducted a peer review of the proposal. The IBET program provides patients with a tailored exercise program (based on functional level, symptoms, and current activity), video demonstrations of exercises, and guidance for appropriate exercise progression. The PT group receives up to 8 individual visits with a physical therapist, mirroring standard practice for knee OA and with an emphasis on a home exercise program. Outcomes are assessed at baseline, 4 months (primary time point) and 12 months (to assess maintenance of treatment effects). The primary outcome is the Western Ontario and McMaster Universities Osteoarthritis Index, and secondary outcomes include objective physical function, satisfaction with physical function, physical activity, depressive symptoms and global assessment of change. Linear mixed models will be used to compare both the IBET and standard PT groups to the WL control group, examine whether IBET is non-inferior to PT (a treatment that has an established evidence base for knee OA), and explore whether participant characteristics are associated with differential effects of IBET and/or standard PT. This research is in compliance with the Helsinki Declaration and was approved by the Institutional Review Board of the University of North Carolina at Chapel Hill. Discussion The IBET program could be disseminated widely at relatively low cost and could be an important resource for helping patients with knee OA to adopt and maintain appropriate physical activity. This trial will provide an important evaluation of the effectiveness of this IBET program for knee OA. Trial registration NCT0231271

Hypertension-mediated organ damage regression associates with blood pressure variability improvement three years after successful treatment initiation in essential hypertension

Blood pressure variability (BPV) has been associated with the development, progression, and severity of cardiovascular (CV) organ damage and an increased risk of CV morbidity and mortality. We aimed to explore any association between short-term BPV reduction and hypertension-mediated organ damage (HMOD) regression in hypertensive patients 3-year post-treatment initiation regarding BP control. 24-h ambulatory blood pressure monitoring (24 h ABPM) was performed at baseline in 180 newly diagnosed and never-treated hypertensive patients. We measured 24 h average systolic (24 h SBP) and diastolic BP (24 h DBP) as well as 24 h systolic (sBPV) and diastolic BPV (dBPV). Patients were initially evaluated and 3 years later regarding arterial stiffness (PWV), left ventricular hypertrophy (LVMI), carotid intima-media thickness (cIMT), 24 h microalbumin levels (MAU), and coronary flow reserve (CFR). Successful BP treatment was defined as 24 h SBP/DBP < 130/80 mm Hg based on 2nd ABPM and subsequently, patients were characterized as controlled (n = 119, age = 53 ± 11 years) or non-controlled (n = 61, age = 47 ± 11 years) regarding their BP levels. In the whole population and the controlled group, 24 h SBP/DBP, sBPV/dBPV, LVMI, and IMT were decreased. Additionally, LVMI improvement was related with both sBPV (p <.001) and dBPV reduction (r =.18, p =.02 and r =.20, p =.03, respectively). In non-controlled hypertensives, PWV was increased. In multiple linear regression analysis, sBPV and dBPV reduction predicted LVMI improvement in total population and controlled group independently of initial office SBP, mean BP, and 24 h-SBP levels. In middle-aged hypertensive patients, a 3-year antihypertensive treatment within normal BP limits, confirmed by 24-h ABPM, leads to CV risk reduction associated with sBPV and dBPV improvement. © 2021 The Authors. The Journal of Clinical Hypertension published by Wiley Periodicals LLC

New Equations for Predicting Maximum Oxygen Uptake in Patients With Heart Failure

We obtained directly measured maximal oxygen uptake (VO2 max) by open-circuit spirometry in 1,453 patients with chronic heart failure (HF) who completed a treadmill test (n = 1,453) or cycle ergometry (n = 1,838), as participants in The Fitness Registry and the Importance of Exercise National Data Base (FRIEND) dataset. We developed a new equation to predict measured VO2 max in those using a treadmill by randomly sampling 70% of the participants from each of the following age categories: <40, 40 to 50, 50 to 70, and >70 and used the remaining 30% for validation. Multivariable linear regression analysis was applied to identify the most relevant variables and construct the best prediction model for VO2 max. Treadmill speed and treadmill speed * grade were considered in the final model as predictors of measured VO2 max and the following equation was generated: VO2 max in ml O2 kg/min = speed (m/min) * (0.17 + fractional grade * 0.32) +3.5. To assess the efficacy of the equation, we applied it to 1,612 patients in the HF-ACTION cohort. To assess the efficacy of the FRIEND cycle ergometry equation developed for healthy individuals we applied it to 1,838 HF patients in the FRIEND cohort and 306 patients in a Greek population of HF patients with directly measured VO2 max. The FRIEND equations were superior to ACSM equations in predicting VO2 max regardless of the cohort or exercise mode used (treadmill or cycle ergometry) to access VO2 max. © 2020 Elsevier Inc

HDL cholesterol levels and endothelial glycocalyx integrity in treated hypertensive patients

Endothelial dysfunction indicates target organ damage in hypertensive patients. The integrity of endothelial glycocalyx (EG) plays a vital role in vascular permeability, inflammation and elasticity, and finally to cardiovascular disease. The authors aimed to investigate the role of increased HDL cholesterol (HDL-C) levels, which usually are considered protective against cardiovascular disease, in EG integrity in older hypertensive patients. The authors studied 120 treated hypertensive patients older than 50 years were divided regarding HDL-C tertiles in group HDLH (HDL-C ≥ 71 mg/dL, upper HDL-C tertile) and group HDLL (HDL-C < 71 mg/dL, two lower HDL-C tertiles). Increased perfusion boundary region (PBR) of the sublingual arterial microvessels (ranging from 5 to 9 µm) using Sideview Darkfield imaging (Microscan, Glycocheck) was measured as a non-invasive accurate index of reduced EG thickness. PBR 5-9 was significantly decreased in group HDLH (P = 0.04). In the whole population, HDL-C was inversely but moderately related to PBR 5-9 (r = −0.22, P = 0.01). In a multiple linear regression analysis model, using age, BMI, smoking habit, HDL-C, LDL-C, and office SBP, as independent variables, the authors found that BMI (β = 0.25, P = 0.006) independently predicted PBR 5-9 in the whole population. In older hypertensive patients, HDL-C ranging between 71 and 101 mg/dL might moderately protect EG and subsequently endothelial function. Future studies in several groups of low- or high-risk hypertensives are needed in order to evaluate the beneficial role of extremely elevated HDL-C regarding cardiovascular risk evaluation as well as endothelial glycocalyx as a novel index of target organ damage in essential hypertension. ©2018 Wiley Periodicals, Inc

Diagnostic par courant de Foucault : separation et caracterisation des transitoires d'un signal par une methode numerique/symbolique

SIGLEAvailable at INIST (FR), Document Supply Service, under shelf-number : 26165 A, issue : a.1996 n.55 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc