Generalized Clausius relation and power dissipation in nonequilibrium stochastic systems

In the framework of the stochastic dynamics of open Markov systems, we derive an extension of the Clausius inequality for transitions between states of the system. We give a formula for the power produced when the system is in its stationary state and relate it to the dissipation of energy needed to maintain the system out of equilibrium. We deduce that, near equilibrium, maximal power production requires an energy dissipation of the same order of magnitude as the power production.

Performic acid (PFA): tests on an advanced primary effluent show promising disinfection performance

Performic acid, or PFA (CH(2)O(3)), is a well-known oxidizing agent and disinfectant in the medical field and food industry. It has recently become available on a commercial scale for potential use in wastewater disinfection. This study investigated its application to an advanced primary effluent which is recalcitrant to disinfection by UV and peracetic acid (PAA). Methods were developed for determining PFA concentrations in stock solutions as well as in residual concentrations in the wastewater. Batch and continuous-flow pilot studies showed a correlation between log fecal coliform removals and PFA doses. A PFA dose of approximately 3.4 mg/L and a contact time of 45 minutes could achieve 3-logs removal, and almost total disinfection could be achieved using a dose of 6 mg/L. The by-products of PFA addition are hydrogen peroxide and formic acid (CHOOH), neither of which is considered to be toxic to aquatic fauna at the doses required for disinfection.

Temporal assessment of bone marrow lesions on magnetic resonance imaging in a canine model of knee osteoarthritis: impact of sequence selection

OBJECTIVE

To assess the evolution of bone marrow lesions (BMLs) in a canine model of knee osteoarthritis (OA) using three different magnetic resonance imaging (MRI) sequences.

DESIGN

Three MRI sequences [coronal, T1-weighted three-dimensional fast gradient recalled echo (T1-GRE), sagittal fat-suppressed 3D spoiled gradient echo at a steady state (SPGR), and sagittal T2-weighted fast spin echo with fat saturation (T2-FS)] were performed at baseline, and at week 4, 8 and 26 in five dogs following transection of the anterior cruciate ligament. The same reader scored (0-3) subchondral BMLs twice, in blinded conditions, according to their extent in nine joint subregions, for all imaging sessions, and independently on the three MRI sequences. Correlation coefficients and Bland-Altman plots evaluated intra-reader repeatability. Readings scores were averaged and the nine subregions were summed to generate global BML scores.

RESULTS

BMLs were most prevalent in the central and medial portions of the tibial plateau. Intra-reader repeatability was good to excellent for each sequence (r(s)=0.87-0.97; P<0.001). Maximal intra-reader variability (24%) was reached on T2-FS and was associated to higher scores (P<0.05). Global BML scores increased similarly on all three sequences until week 8 (P<0.05). At week 26, score on T2-FS was decreased, being lower when compared to T1-GRE and SPGR (P<0.05).

CONCLUSION

In this canine OA model, the extent of BMLs varies in time on different MRI sequences. Until the complex nature of these lesions is fully resolved, it is suggested that to accurately assess the size and extent of BMLs, a combination of different sequences should be used.

The standardized Ginkgo biloba extract Egb-761 protects vascular endothelium exposed to oxidized low density lipoproteins

Dietary antioxidants are frequently proposed as protective agents for the vascular endothelium during the onset of atherosclerosis. This protection may occur at two distinct levels. First, they prevent oxidative modification of atherogenic lipoproteins (LDL). Second, they can provide a cellular protection against oxidized LDL-mediated endothelium dysfunction, although this mechanism remains poorly considered in many instances. To gain insight into the mechanism underlying such cellular protection against oxidized LDL, we examined the impact of a popular traditional medicine, an extract from Ginkgo biloba with well-known antioxidant properties, on two endothelial cells properties: cell adhesion and ionic homeostasis. Cellular lipoperoxides levels were also measured as a marker of cellular oxidative stress. Human umbilical-vein endothelial cells were exposed to native (nat-) or oxidized (ox-) LDL, the latter prepared to be compatible with clinically observed levels of oxidation. Although nat-LDL had little effect, ox-LDL increased endothelial adhesive properties (35%, p<0.01) and lipoperoxidation (45%, p<0.01). Na,K-ATPase activity, a key regulator of ionic homeostasis, was significantly decreased after exposure to nat-LDL (30%, p<0.01) and dramatically depressed after exposure to ox-LDL (65%, p<0.001). The standardized preparation of Ginkgo biloba EGb-761 totally protected adhesive properties and endothelial lipoperoxide levels. Moreover, it limited the decrease in Na,K-ATPase activity induced by ox-LDL to levels similar to nat-LDL. This suggests that EGb-761 protects endothelial adhesive properties and helps prevent the disruption of ionic homeostasis. The EGb-761-mediated inhibition of ox-LDL-induced lipoperoxide levels in endothelial cells appears to be an important mechanism by which Ginkgo biloba extract protects endothelial properties.

Optimizing intermittent reaction paths

Various examples of biochemical reactions in cells, such as DNA/protein interactions, reveal that in extremely diluted regimes reaction paths are not always simple brownian trajectories. They can rather be qualified as intermittent, since they combine slow diffusion phases on one hand and a second mode of faster transport on the other hand, which can be either a faster diffusion mode, as in the case of DNA-binding proteins, or a ballistic mode powered by molecular motors in the case of intracellular transport. In this article, we introduce simple theoretical models which permit to calculate explicitly the reaction rates for reactions limited by intermittent transport. This approach shows quantitatively that intermittent reaction pathways are actually very efficient, since they permit to significantly increase the reaction rates, which could explain why they are observed so often. Moreover, we give theoretical arguments which suggest that intermittent transport could also be useful for in vitro chemistry. Indeed, we show that intermittent transport naturally pops up in the context of reaction at interfaces, where reactants combine surface diffusion phases and bulk excursions, and could permit to enhance reactivity. In this case, adjusting chemically the affinity of reactants with the interface makes possible to optimize the reaction rate.

[Absolute risk fracture prediction by risk factors validation and survey of osteoporosis in a Brussels cohort followed during 10 years (FRISBEE study)]

Osteoporosis is a major public health problem. For the time being, the diagnosis of osteoporosis relies on densitometry (T-score < -2.5 by DXA), although the risk of fracture depends also on other factors than the bone mass. Osteoporosis diagnosis (DXA) must be distinguished from the individual risk assessment of fracture. Different risk factors complementary to bone mass have been already validated in different populations. These include an old age, a history of fracture after the age of 50, a familial history of hip fracture (father or mother), a low BMI (< 20), corticoid treatment (> 3 months), tabagism and excessive alcohol consumption. A WHO taskforce has combined these different factors in order to integrate them in a 10-years predictive risk model of fracture (FRAX**). This model should still be validated in different populations, especially in populations not included in its development, which is the case for Belgium. We are evaluating these different risk factors for fracture in a Brussels population of 5000 women (60-80 years) who will be followed each year during 10 years. We also assess the predictive value of other risk factors for fracture not included in the WHO model (tendency to fall, use of sleeping pills, early non substituted menopause, sedentarity, ...). In an interim analysis of the first 452 women included and with data yet available at the time of this writing, we could find a significant (P < 0.05) relationship between diagnosis of osteoporosis at DXA and the number of risk factors, age > 70 years, a personal history of fracture after 50 years and a BMI < 20.

N-acetyl-beta-D-glucosaminidase index as an early biomarker for chronic kidney disease in cats with hyperthyroidism

BACKGROUND

Hyperthyroid cats are at risk of developing azotemic chronic kidney disease (CKD) and diagnostic tools currently used to screen for CKD in hyperthyroid cats are either unreliable or impractical.

HYPOTHESIS

Urine N-acetyl-beta-D-glucosaminidase index (NAG(i)) is a good biomarker for azotemic CKD in hyperthyroid cats.

ANIMALS

Twenty-four newly diagnosed nonazotemic hyperthyroid cats and 10 healthy cats.

METHODS

All cats were evaluated for hyperthyroidism at baseline. Hyperthyroid cats were treated with methimazole and reevaluated once euthyroid. At the end of the study, cats were divided into 3 groups: healthy cats, nonazotemic, and azotemic euthyroid cats. Baseline group characteristics were compared to predict azotemic CKD. The influence of treatment on NAG(i) was evaluated.

RESULTS

Baseline NAG(i) was significantly different among groups (P= .004). Azotemic cats had a higher median value (13.12 U/g) when compared with healthy cats (1.38 U/g). With NAG(i) >2.76 U/g, negative and positive predictive values for development of azotemia were 77.7 and 50%, whereas the combination of a urine specific gravity (USG) <or=1.035 and T(4) >7.80 microg/dL enhanced predictive values to 88.9 and 83.3%, respectively. NAG(i) values decreased significantly over time in treated nonazotemic cats.

CONCLUSIONS AND CLINICAL RELEVANCE

Baseline NAG(i) did not differentiate azotemic from nonazotemic euthyroid cats. NAG(i) could be used to assess renal function during medical therapy allowing the clinician to adjust methimazole dosage accordingly. The combination of USG and T(4) could optimize identification of appropriate candidates for permanent treatment of hyperthyroidism.

Preliminary validation of curve progression model for brace treatment

Brace treatment is the most commonly used non-surgical treatment for adolescent idiopathic scoliosis (AIS). A brace compliance monitoring system consisting of a microcomputer and a force transducer was used to monitor how brace candidates used their braces during daily activates. A prediction model of the brace treatment outcome was developed based on 20 AIS subjects. Six subjects (1M, 5F) with AIS who had worn their braces for six weeks participated into this study. One month data was recorded during the study period. Knowing the risk progression at the beginning of brace treatment plus how brace subjects used their braces in terms of brace tightness and wear time during brace treatment yielded a predicted outcome which was compared to the final treatment outcomes with 2 years followed-up. This preliminary result demonstrated that the prediction model was able to predict the treatment outcome within +/-3.5 degrees.

Magnetic resonance imaging can accurately assess the long-term progression of knee structural changes in experimental dog osteoarthritis

OBJECTIVES

Osteoarthritis (OA) structural changes take place over decades in humans. MRI can provide precise and reliable information on the joint structure and changes over time. In this study, we investigated the reliability of quantitative MRI in assessing knee OA structural changes in the experimental anterior cruciate ligament (ACL) dog model of OA.

METHODS

OA was surgically induced by transection of the ACL of the right knee in five dogs. High resolution three dimensional MRI using a 1.5 T magnet was performed at baseline, 4, 8 and 26 weeks post surgery. Cartilage volume/thickness, cartilage defects, trochlear osteophyte formation and subchondral bone lesion (hypersignal) were assessed on MRI images. Animals were killed 26 weeks post surgery and macroscopic evaluation was performed.

RESULTS

There was a progressive and significant increase over time in the loss of knee cartilage volume, the cartilage defect and subchondral bone hypersignal. The trochlear osteophyte size also progressed over time. The greatest cartilage loss at 26 weeks was found on the tibial plateaus and in the medial compartment. There was a highly significant correlation between total knee cartilage volume loss or defect and subchondral bone hypersignal, and also a good correlation between the macroscopic and the MRI findings.

CONCLUSION

This study demonstrated that MRI is a useful technology to provide a non-invasive and reliable assessment of the joint structural changes during the development of OA in the ACL dog model. The combination of this OA model with MRI evaluation provides a promising tool for the evaluation of new disease-modifying osteoarthritis drugs (DMOADs).

Comparison of trot kinetics between dogs with stifle or hip arthrosis

The purposes of this study were: 1) to describe and compare the trotting gait of normal and lame dogs secondary to stifle (GONOA) or hip (COXOA) osteoarthritis (OA) using multiple ground reaction forces (GRF) parameters, and 2) to pinpoint any characteristic in gait profile ('signatures') which could help to discriminate a lameness secondary to GONOA or COXOA. Fifty-one large breed dogs with OA (19 GONOA, 32 COXOA) and 22 normal dogs were included in the study. The vertical and cranio-caudal (braking-propelling) GRF were collected. The total stance time, and for each orthogonal vector, the peak force, impulse, time to peak, and the rate of limb loading were recorded. Vertical and craniocaudal forces were found to be significantly decreased in both OA groups compared to normal dogs. Vertical, cranial and caudal limb loading were also most often lower for both OA groups. In addition, the vertical and cranial forces were significantly lower in dogs with GONOA compared to COXOA and normal dogs. This study has demonstrated that, at a trotting gait, OA dogs secondary to GONOA and COXOA load their affected limb, brake and propel earlier during the stance phase, but generally with less magnitude than normal dogs. Dogs affected by GONOA also present more severe gait alterations than dogs with COXOA. The vertical and braking specific GRF alterations described may be kinetic 'signatures' linked more to lame dogs secondary to GONOA versus COXOA. Finally, this study has also provided useful baseline GRF data for further clinical and research investigations.

Gliding arc discharge in the potato pathogen Erwinia carotovora subsp. atroseptica: mechanism of lethal action and effect on membrane-associated molecules

Gliding arc (glidarc) discharge is a physicochemical technique for decontamination at atmospheric pressure and ambient temperature. It leads to the destruction of bacterial phytopathogens responsible for important losses in industrial agriculture, namely, Erwinia spp., without the formation of resistant forms. We investigated the effect of a novel optimized prototype allowing bacterial killing without lag time. This prototype also decreases the required duration of treatment by 50%. The study of the time course effect of the process on bacterial morphology suggests that glidarc induces major alterations of the bacterial membrane. We showed that glidarc causes the release of bacterial genomic DNA. By contrast, an apparent decrease in the level of extractible lipopolysaccharide was observed; however, no changes in the electrophoretic pattern and cytotoxic activity of the macromolecule were noted. Analysis of extractible proteins from the outer membrane of the bacteria revealed that glidarc discharge induces the release of these proteins from the lipid environment, but may also be responsible for protein dimerization and/or aggregation. This effect was not observed in secreted enzymatic proteins, such as pectate lyase. Analysis of the data supports the hypothesis that the plasma generated by glidarc discharge is acting essentially through oxidative mechanisms. Furthermore, these results indicate that, in addition to effectively destroying bacteria, glidarc discharge should be used to improve the extraction of bacterial molecules.

Intermittent search process and teleportation

The authors study an intermittent search process combining diffusion and "teleportation" phases in a d-dimensional spherical continuous system and in a regular lattice. The searcher alternates diffusive phases, during which targets can be discovered, and fast phases (teleportation) which randomly relocate the searcher, but do not allow for target detection. The authors show that this alternation can be favorable for minimizing the time of first discovery, and that this time can be optimized by a convenient choice of the mean waiting times of each motion phase. The optimal search strategy is explicitly derived in the continuous case and in the lattice case. Arguments are given to show that much more general intermittent motions do provide optimal search strategies in d dimensions. These results can be useful in the context of heterogeneous catalysis or in various biological examples of transport through membrane pores.

Efficacy of licofelone in dogs with clinical osteoarthritis

To evaluate the effect of licofelone, an arachidonic acid substrate with combined inhibitory activity against 5-lipoxygenase and cyclooxygenases 1 and 2, a double-blind, randomised and placebo-controlled study was conducted in 33 client-owned dogs that were lame owing to hindlimb osteoarthritis. Seventeen of the dogs received a placebo and 16 were treated with 2.5 mg/kg licofelone twice a day for 28 days. The dogs' lameness was assessed on a visual analogue scale (vas), and by force plate analyses at baseline and 14 and 28 days after starting the treatment. After 14 days the mean (se) change in peak vertical force in the licofelone-treated dogs (1.7 [0.8] per cent bodyweight) was significantly greater (P<0.05) than in the placebo-treated dogs (-0.3 [0.6] per cent bodyweight), and after 28 days the difference had increased. In contrast, the dogs' lameness, as assessed by the vas values, had decreased significantly over baseline in both the treated and control groups.

Predicting bacteraemia following chemotherapy administration in patients with hematological cancer (HC)

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Background: Infections cause important morbidity and mortality in patients undergoing treatment for cancer. The type and the intensity of chemotherapy play an important role in the risk of infection which manifests itself most often as febrile neutropenia (FN) but regimen-specific risks are not well defined. Since bacteraemia is associated with increased mortality, we tried to determine predictors of it and to validate a classification of aggressiveness of a given chemotherapy regimen (CR) to be used in a risk prediction model in patients with HC. Methods: Patients older than 16 years, diagnosed with HC of any type were prospectively enrolled and followed at the “Institut Jules Bordet” and at the “Cliniques Universitaires Saint-Luc (UCL)” between 2001–2005. Out of the 266 patients, 22.9%, 43.6% and 33.5% were followed respectively during one cycle, 2 to 4 cycles and more than 4 cycles, totalizing 1053 cycles. Relevant patient’s information were collected at the beginning of the first cycle. Before each cycle, the CR score was computed, a blood examination performed and the temperature measured. Bacteraemia was defined according to IDSA criteria. FN was defined as a neutrophil count < 500/μl and fever. Generalized Estimating Equations (GEE) was used for the analysis. Results: Among 1017 evaluable cycles, 148 (14.5%) were followed by an episode of bacteraemia. Among the cycles with FN, 35.5% had bacteraemia. In the final model, adjusted for antimibrobial prophylaxis (R2=0.22), the CR score was the most important predictor of bacteraemia (OR 4.2 [95% CI, 2.3–7.6]), for patients given an aggressive regimen compared to the others. The other predictors associated with bacteraemia were: underlying disease (3.2 [1.9–5.2]), a baseline monocytopenia (<150/μL) (2.7 [1.6–4.3]), a baseline CRP >10 mg/L (2.1 [1.2–3.7]), the first cycle of patient’s treatment (0.3 [0.2–0.7]) and the administration of immunosuppressive agents (2.2 [1.2–4.0]). Conclusions: Bacteraemia was frequent in patients with HC undergoing myelosuppressive chemotherapy, especially in patients with FN. The CR plays an important role but further studies are needed to investigate yet unidentified additional risk factors. Grant given by the FNRS in Belgium (“Fonds National pour la Recherche Scientifique”)

No significant financial relationships to disclose.

High-avidity monoclonal antibodies against the human scavenger class B type I receptor efficiently block hepatitis C virus infection in the presence of high-density lipoprotein

The human scavenger class B type 1 receptor (SR-B1/Cla1) was identified as a putative receptor for hepatitis C virus (HCV) because it binds to soluble recombinant HCV envelope glycoprotein E2 (sE2). High-density lipoprotein (HDL), a natural SR-B1 ligand, was shown to increase the in vitro infectivity of retroviral pseudoparticles bearing HCV envelope glycoproteins and of cell culture-derived HCV (HCVcc), suggesting that SR-B1 promotes viral entry in an HDL-dependent manner. To determine whether SR-B1 participates directly in HCV infection or facilitates HCV entry through lipoprotein uptake, we generated a panel of monoclonal antibodies (MAbs) against native human SR-B1. Two of them, 3D5 and C167, bound to conformation-dependent SR-B1 determinants and inhibited the interaction of sE2 with SR-B1. These antibodies efficiently blocked HCVcc infection of Huh-7.5 hepatoma cells in a dose-dependent manner. To examine the role of HDL in SR-B1-mediated HCVcc infection, we set up conditions for HCVcc production and infection in serum-free medium. HCVcc efficiently infected Huh-7.5 cells in the absence of serum lipoproteins, and addition of HDL led to a twofold increase in infectivity. However, the HDL-induced enhancement of infection had no impact on the neutralization potency of MAb C167, despite its ability to inhibit both HDL binding to cells and SR-B1-mediated lipid transfer. Of note, MAb C167 also potently blocked Huh-7.5 infection by an HCV strain recovered from HCVcc-infected chimpanzees. These results demonstrate that SR-B1 is essential for infection with HCV produced in vitro and in vivo and suggest the possible use of anti-SR-B1 antibodies as therapeutic agents.

Scavenger receptor BI and BII expression levels modulate hepatitis C virus infectivity

Hepatitis C virus (HCV) enters cells via a pH- and clathrin-dependent endocytic pathway. Scavenger receptor BI (SR-BI) and CD81 are important entry factors for HCV internalization into target cells. The SR-BI gene gives rise to at least two mRNA splice variants, SR-BI and SR-BII, which differ in their C termini. SR-BI internalization remains poorly understood, but SR-BII is reported to endocytose via a clathrin-dependent pathway, making it an attractive target for HCV internalization. We demonstrate that HCV soluble E2 can interact with human SR-BI and SR-BII. Increased expression of SR-BI and SR-BII in the Huh-7.5 hepatoma cell line enhanced HCV strain J6/JFH and JFH infectivity, suggesting that endogenous levels of these receptors limit infection. Elevated expression of SR-BI, but not SR-BII, increased the rate of J6/JFH infection, which may reflect altered intracellular trafficking of the splice variants. In human plasma, HCV particles have been reported to be complexed with lipoproteins, suggesting an indirect interaction of the virus with SR-BI and other lipoprotein receptors. Plasma from J6/JFH-infected uPA-SCID mice transplanted with human hepatocytes demonstrates an increased infectivity for SR-BI/II-overexpressing Huh-7.5 cells. Plasma-derived J6/JFH infectivity was inhibited by an anti-E2 monoclonal antibody, suggesting that plasma virus interaction with SR-BI was glycoprotein dependent. Finally, anti-SR-BI antibodies inhibited the infectivity of cell culture- and plasma-derived J6/JFH, suggesting a critical role for SR-BI/II in HCV infection.

A smart orthosis for the treatment of scoliosis

The tightness of an orthosis for the treatment of scoliosis varies greatly during daily activities. To be effective the orthosis should be maintained at the prescribed tightness to optimize the active component of objective treatment. Subjective feeling is the most commonly used method to evaluate how patients tighten their orthoses. To provide an objective measure, a battery-powered microcomputer system was developed to monitor loads exerted by orthoses during daily living. The system not only records how well the orthosis has been used, but also helps patients wear the orthoses as prescribed. Four subjects have used the system for one month. The proportion of the time that the subject wore the orthosis at the prescribed level increased from 53&#177;10% to 69&#177;16%. The effectiveness of the smart orthosis is still under evaluation.

Wireless Surgical Tools for Mechanical Measurements during Scoliosis Surgery

Comprehensively understanding the mechanics of loads applied by orthopaedic surgeons and distributed to the spine during scoliosis corrective surgery may improve surgical outcome and patient safety. Instruments to measure forces applied by orthopaedic surgeons have been reported. This paper presents instrumented hooks and screws with a real time wireless data acquisition system to measure loads and moments distributed to the spine during scoliosis surgery. From laboratory tests, the maximum error of posterior/anterior forces and moments were 2-3% of the maximum loads during surgery. This study improves the understanding of mechanics during surgical correction.

Random walks and Brownian motion: a method of computation for first-passage times and related quantities in confined geometries

In this paper we present a computation of the mean first-passage times both for a random walk in a discrete bounded lattice, between a starting site and a target site, and for a Brownian motion in a bounded domain, where the target is a sphere. In both cases, we also discuss the case of two targets, including splitting probabilities and conditional mean first-passage times. In addition, we study the higher-order moments and the full distribution of the first-passage time. These results significantly extend our earlier contribution [Condamin, Phys. Rev. Lett. 95, 260601 (2005)].

LDL particle subspecies are distinct in their capacity to mediate free cholesterol efflux via the SR-BI/Cla-1 receptor

The human scavenger receptor SR-BI/Cla-1 promotes efflux of free cholesterol from cells to both high-density and low-density lipoproteins (HDL, LDL). SR-BI/Cla-1-mediated cholesterol efflux to HDL is dependent on particle size, lipid content and apolipoprotein conformation; in contrast, the capacity of LDL subspecies to accept cellular cholesterol via this receptor is indeterminate. Cholesterol efflux assays were performed with CHO cells stably transfected with Cla-1 cDNA. Expression of Cla-1 in CHO cells induced elevation in total cholesterol efflux to plasma, LDL and HDL. Such Cla-1-specific efflux was abrogated by addition of anti-Cla-1 antibody. LDL were fractionated into five subspecies either on the basis of hydrated density or size. Among LDL subfractions, small dense LDL (sdLDL) were 1.5-to 3-fold less active acceptors for Cla-1-mediated cellular cholesterol efflux. Equally, sdLDL markedly reduced Cla-1-specific cholesterol efflux to large buoyant LDL in a dose-dependent manner. Conversely, sdLDL did not influence efflux to HDL(2). These findings provide evidence that LDL particles are heterogeneous in their capacity to promote Cla-1-mediated cholesterol efflux. Relative to HDL(2), large buoyant LDL may constitute physiologically-relevant acceptors for cholesterol efflux via Cla-1.