Variance sum rule for entropy production.

Entropy production is the hallmark of nonequilibrium physics, quantifying irreversibility, dissipation, and the efficiency of energy transduction processes. Despite many efforts, its measurement at the nanoscale remains challenging. We introduce a variance sum rule (VSR) for displacement and force variances that permits us to measure the entropy production rate σ in nonequilibrium steady states. We first illustrate it for directly measurable forces, such as an active Brownian particle in an optical trap. We then apply the VSR to flickering experiments in human red blood cells. We find that σ is spatially heterogeneous with a finite correlation length, and its average value agrees with calorimetry measurements. The VSR paves the way to derive σ using force spectroscopy and time-resolved imaging in living and active matter.

Membrane stress and torque induced by Frank's nematic textures: A geometric perspective using surface-based constraints.

An elastic membrane with embedded nematic molecules is considered as a model of anisotropic fluid membrane with internal ordering. By considering the geometric coupling between director field and membrane curvature, the nematic texture is shown to induce anisotropic stresses additional to Canham-Helfrich elasticity. Building upon differential geometry, analytical expressions are found for the membrane stress and torque induced by splaying, twisting, and bending of the nematic director as described by the Frank energy of liquid crystals. The forces induced by prototypical nematic textures are visualized on the sphere and on cylindrical surfaces.

Bovine anaplasmosis and tick-borne pathogens in cattle of the Galapagos Islands.

A cross-sectional study was conducted to determine the species of Anaplasma spp. and estimate its prevalence in cattle of the three main cattle-producing Galapagos Islands (Santa Cruz, San Cristóbal and Isabela) using indirect PCR assays, genetic sequencing and ELISA. Ticks were also collected from cattle and scanned for 47 tick-borne pathogens in a 48 × 48 real-time PCR chip. A mixed effects logistic regression was performed to identify potential risk factors explaining Anaplasma infection in cattle. A. phagocytophilum was not detected in any of the tested animals. Genetic sequencing allowed detection of A. platys-like strains in 11 (36.7%) of the 30 Anaplasma spp.-positive samples analysed. A. marginale was widespread in the three islands with a global between-herd prevalence of 100% [89; 100]95% CI and a median within-herd prevalence of 93%. A significant association was found between A. marginale infection and age with higher odds of being positive for adults (OR = 3.3 [1.2; 9.9]95% Bootstrap CI ). All collected ticks were identified as Rhipicephalus microplus. A. marginale, Babesia bigemina, Borrelia theileri and Francisella-like endosymbiont were detected in tick pools. These results show that the Galapagos Islands are endemic for A. marginale.

Permeability modes in fluctuating lipid membranes with DNA-translocating pores.

Membrane pores can significantly alter not only the permeation dynamics of biological membranes but also their elasticity. Large membrane pores able to transport macromolecular contents represent an interesting model to test theoretical predictions that assign active-like (non-equilibrium) behavior to the permeability contributions to the enhanced membrane fluctuations existing in permeable membranes [Maneville et al. Phys. Rev. Lett. 82, 4356 (1999)]. Such high-amplitude active contributions arise from the forced transport of solvent and solutes through the open pores, which becomes even dominant at large permeability. In this paper, we present a detailed experimental analysis of the active shape fluctuations that appear in highly permeable lipid vesicles with large macromolecular pores inserted in the lipid membrane, which are a consequence of transport permeability events occurred in an osmotic gradient. The experimental results are found in quantitative agreement with theory, showing a remarkable dependence with the density of membrane pores and giving account of mechanical compliances and permeability rates that are compatible with the large size of the membrane pore considered. The presence of individual permeation events has been detected in the fluctuation time-series, from which a stochastic distribution of the permeation events compatible with a shot-noise has been deduced. The non-equilibrium character of the membrane fluctuations in a permeation field, even if the membrane pores are mere passive transporters, is clearly demonstrated. Finally, a bio-nano-technology outlook of the proposed synthetic concept is given on the context of prospective uses as active membrane DNA-pores exploitable in gen-delivery applications based on lipid vesicles.

Insectos de importancia forense en cadáveres de cerdo (sus scrofa ) en La Paz Bolivia / Forensic insects in pig carcasses (sus scrofa) in La Paz Bolivia

Resumen:La Entomología Forense es una ciencia que implica el estudio de las especies antropofágicas que practican un ciclo vital en el cadáver. Contribuye en la determinación del Intervalo posmortem. Los insectos de importancia forense que se estudiaron pertenecen a la orden Dípteros y Coleópteros. En el estudio realizado en el municipio de Pucarani, ubicado en la provinciaLos Andes del Departamento La Paz a 3852 m.s.n.m. entre otoño e invierno, se obtuvo dos ejemplares de cerdo S. scrofa, en dos ambientes: abierto (cerdo A) y cerrado: (cerdo B). Se identificó 339 especímenes entre dípteros y coleópteros. No se encontraron diferencias significativas en la sucesión de entomofauna entre ambos ambientes, sin embargo predominó la familia Fannide sp. en el lugar cerrado por ser un ambiente húmedo. Los dípteros de mayor importancia son: Sarconesia Chlorogaster, Clorobrachycoma splendida, que pertenecen a la familia Calliphoridae, que se mantuvo en constante actividaden su estadio larval y su forma adulta en los cuatro estados de descomposición a temperaturas de 14 - 16°C, humedad relativa de 30%; no se encontró a Calliphora nigribasis en la descomposición avanzada; Sarconesiopsis magellánica solo se presenta en la etapa Fresco. Entre los Coleópteros: Oxelitrum apicale apareció desde la etapa hinchado. La sucesión de entomofauna cadavérica y su particularidad en cada etapa de descomposición, es el elemento que nos ayudaría a determinar el IPM, que dependerá de las condiciones climáticas a gran altitud como Bolivia.

Abstract:Forensic entomology is a science that involves the study of the cannibalistic species that plays a vital cycle in the body. It helps to determinate the postmortem interval. Insects with forensic importance that were studied belong to the order Diptera and Coleoptera. In the study conducted in the Municipality of Pucarani, located in the province of Los Andes La Paz Department at 3852 meters between autumn and winter, two copies of pork S. scrofa was obtained in two environments: open (pork A), closed (pig B). 339 specimens between Diptera and Coleoptera were identified. No significant differences were found in the entomofauna sequence between the two environments, however the Fannide sp. In the place closed for being a humid environment. The most important dipterans are: Sarconesia Chlorogaster, Clorobrachycoma splendida, belonging to the family Calliphoridae, which remained in constant activity in its larval stage and its adult form in the four decaying states at temperatures of 14 - 16 ° C, humidity Relative to 30%; Calliphora nigribasis was not found in advanced decomposition; Magellanic sarconesiopsis only occurs in the Fresco stage. Among the Coleoptera: Oxelitrum apicale appeared from the swollen stage. The succession of cadaveric entomofauna and its particularity in each stage of decomposition is the element that would help us determine the MPI, which will depend on high altitude climatic conditions like Bolivia.

Susceptibility and possible resistance mechanisms in the palm species Phoenix dactylifera, Chamaerops humilis and Washingtonia filifera against Rhynchophorus ferrugineus (Olivier, 1790) (Coleoptera: Curculionidae).

Rhynchophorus ferrugineus, known as the Red Palm Weevil (RPW), is reported as a pest of up to 40 palm species. However, the susceptibility degree and the defense mechanisms of these species against this weevil are still poorly known. In Europe, the RPW is a major pest of Phoenix canariensis while other palm species, including the congeneric Phoenix dactylifera, seem to be less suitable hosts for this insect. The aim of our study was to compare the defensive response of P. dactylifera, Chamaerops humilis and Washingtonia filifera against R. ferrugineus and try to define the mechanisms of resistance that characterize these species. Bioassays were carried out to evaluate the mortality induced on RPW larvae by extracts from the leaf rachis of the studied palm species. Tests at semi-field scale were also conducted, based either on forced palm infestation, with larvae of RPW, or on natural infestation, with adult females. Rachis extracts from C. humilis and W. filifera caused 100% larval mortality after 2 days of exposure, while extracts of P. dactylifera did not impair larval survival. Independently of the effect of the leaf extracts, the weevils were unable to naturally infest the three palm species, although larval survival was high after forced infestation of the plants. We concluded that the observed lack of infestation of P. dactylifera by RPW is due to factors other than antibiosis. In W. filifera and C. humilis, although the presence of antixenosis mechanisms cannot be excluded, resistance to R. ferrugineus seems to rely on the presence of antibiosis compounds.

Thermomechanical transitions of egg-ceramide monolayers.

Ceramides have unique biophysical properties. Their high melting temperature and their ability to form lateral domains have converted ceramides into the paradigm of rigid lipids. Here, using shear surface rheology of egg-ceramide Langmuir monolayers, a solid to fluid transition was evidenced as a vanishing shear rigidity at lower temperatures than the lipid melting temperature. Such a mechanical transition, which depends on the lipid lateral pressure, was found in a broad range temperature (40-50 °C). The solid to fluid transition was correlated to a LC to LC+LE phase transition, as confirmed by BAM experiments. Interestingly, together with the softening transition, a supercooling process compatible with a glassy behavior was found upon freezing. A new phase scenario is then depicted that broadens the mechanical behavior of natural ceramides. The phase diversity of ceramides might have important implications in their physiological roles.

Marangoni stresses and surface compression rheology of surfactant solutions. Achievements and problems.

In the presence of soluble surfactants, the motion of liquid surfaces involves Marangoni effects. As a consequence, the surfaces exhibit elastic responses, even frequently behaving as rigid surfaces, especially at low surfactant concentration. The Marangoni effects can be conveniently quantified introducing surface viscoelastic compression parameters that characterize the mechanical response of the surface near equilibrium. Many experimental techniques allow measuring the viscoelastic parameters. However, many difficulties are encountered during the interpretation of the surface response in the various types of hydrodynamic velocity fields involved in the different techniques. The role of adsorption and desorption energy barriers appears crucial, despite the fact that little is known yet about their values. In this short review, we will present examples illustrating the different problems.

Membrane reconstitution of FtsZ-ZipA complex inside giant spherical vesicles made of E. coli lipids: large membrane dilation and analysis of membrane plasticity.

During the division process of Escherichia coli, the globular protein FtsZ is early recruited at the constriction site. The Z-ring, based on FtsZ filaments associated to the inner cell membrane, has been postulated to exert constriction forces. Membrane anchoring is mediated by ZipA, an essential transmembrane protein able to specifically bind FtsZ. In this work, an artificial complex of FtsZ-ZipA has been reconstituted at the inner side of spherical giant unilamellar vesicles made of E. coli lipids. Under these conditions, FtsZ polymerization, triggered when a caged GTP analogue is UV-irradiated, was followed by up to 40% vesicle inflation. The homogeneous membrane dilation was accompanied by the visualization of discrete FtsZ assemblies at the membrane. Complementary rheological data revealed enhanced elasticity under lateral dilation. This explains why vesicles can undergo large dilations in the regime of mechanical stability. A mechanical role for FtsZ polymers as promoters of membrane softening and plasticization is hypothesized.

Langmuir polymer films: recent results and new perspectives.

Langmuir polymer films (LPFs) are very interesting systems to probe quasi-two dimensional dynamics. Although adsorbed on water, the substrate is fluid enough to avoid irreversible pinning at adsorption sites, as with solid substrates. LPFs in dense states can exhibit a high degree of metastability, however reproducible measurements can be performed on films which have not been previously compressed. The shear rheology is one of the most active fields of research, especially because it allows investigation of flow behaviour in LPFs, thus of possible reptation motion in semidilute films under good solvent conditions. It also allows probing glassy behaviour in dense films under poor solvent conditions. In this perspective article, we review the recent literature and discuss unpublished results on the dynamics of the glass transition, recently observed in these quasi-2D systems at low temperatures. We conclude by listing new problems and open questions emerging from this research area.

Regulation of chemokine responses in intestinal epithelial cells by stress and Toxoplasma gondii infection.

Infection with Toxoplasma gondii induces chemokine up-regulation in several cell types. Here, we investigated the role of stress products (norepinephrine, NE) on chemokine production in mouse intestinal epithelial cells (IECs). Purified IECs were used to determine the expression levels of chemokines by real-time PCR. There was significantly increased expression in CCL2, CCL3, CCL5, CXCL2, CXCL9 and CXCL10 in IECs following peroral infection with T. gondii (INF) on day eight post-infection (PI) compared to infected mice subjected to cold-water stress (INF+CWS). In vitro studies using the MODE-K cell line showed increased chemokine mRNA and protein expression in infected but not in cells exposed to parasite antigen. Down-regulation of chemokine expression was more pronounced when active infection was used in combination with NE. Chemokine receptor expression was increased in IECs isolated from INF and decreased in the INF+CWS group. In MODE-K cells, there was decreased mRNA expression of chemokine receptors when incubated with ß-adrenergic antagonists. Neither, adrenergic antagonists blocked the effect of infection on chemokine receptor expression. Cold-water stress was able to decrease expression of chemokines and their receptors in IECs in vivo and in vitro. Cold-water stress-mediated modulation of innate intestinal responses are beneficial in C57BL/6 mice during T. gondii infection.

Amorphous freezing in two dimensions: from soft coils to rigid particles.

The topic of the gel transition in two dimensions is revisited by considering data on the shear elasticity of Langmuir monolayers of different spherical objects. Amorphous freezing can be associated to structural percolation in a lattice able to resist shear stresses. The shear modulus and its dependence on the packing fraction are found to strongly depend on the details of the interaction potential and largely differ from expectations for entropic networks. This behaviour can be interpreted in terms of more elaborated percolation theories including central forces and bond-bending forces.

Dissipative curvature fluctuations in bilayer vesicles: Coexistence of pure-bending and hybrid curvature-compression modes.

We have studied the relaxation dynamics of shape fluctuations in unilamellar lipid vesicles by neutron spin echo (NSE). The presence of a hybrid curvature-compression mode coexisting with the usual bending one has been revealed in the experimental relaxation functions at high q . Differently to the conventional relaxation approximately q (3) typical for bending modes, the hybrid mode was found to relax as approximately q (2) , which is compatible with a dissipation mechanism arising from intermonolayer friction. Complementary data obtained from flickering spectroscopy (FS) in giant unilamellar vesicles confirm the existence of both modes coexisting together. By combining NSE and FS data we have depicted the experimental bimodal dispersion diagram, which is found compatible with theoretical predictions for reliable values of the material parameters. From the present data two conventional dynamical methods (NSE and FS) have been shown to be suitable for measuring intermonolayer friction coefficients in bilayer vesicles.

Bimodal spectrum for the curvature fluctuations of bilayer vesicles: pure bending plus hybrid curvature-dilation modes.

We study thermal undulations of giant bilayer vesicles by flickering spectroscopy. The experimental fluctuation spectra are scrutinized in view of the classical Helfrich theory. Pure bending modes are revealed to be unable to predict the large fluctuations systematically found at a high wave vector. Hybrid curvature-dilational modes are then invoked as a more efficient mode of motion in producing high curvatures. A bimodal spectrum of the thermal undulations has been theoretically developed for the shell-like topology. Reconciliation between experiments and theory is achieved when this bimodal spectrum is considered.

Molecular weight dependence of the shear rheology of poly(methyl methacrylate) Langmuir films: a comparison between two different rheometry techniques.

The surface shear rheology of Langmuir monolayers of poly(methyl methacrylate) (PMMA) has been studied as a function of polymer concentration (Gamma) and molecular weight (N). Two different rheology techniques were used, one based on free damped oscillations of a ring with a sharp edge and the other based on a forced oscillation of a biconical disk. Both instruments were used in the oscillatory mode at comparable oscillation frequency and amplitude, which gave access to the viscoelastic shear modulus (S). The two instruments, working in different viscosity ranges, provide complementary and mutually compatible data. The results obtained for four PMMA samples of molecular weight between 8x10(3) and 2.7x10(5) g.mol(-1) show powerlike behavior as S approximately Gamma10 and S approximately N4. These strong dependences suggest a structural scenario based on the 2D percolation of the polymer pancakes.

Regulation of toll-like receptors in intestinal epithelial cells by stress and Toxoplasma gondii infection.

Intestinal epithelial cells (IECs) form a barrier between invading microorganisms and the underlying host tissues. IECs express toll-like receptors (TLRs) that recognize specific molecular signatures on microbes, which activate intracellular signalling pathways leading to production of proinflammatory cytokines and chemokines. Stress hormones play an important role in modulation of proinflammatory cytokines and down-regulation of immune responses. Here we demonstrated that expression levels of TLR-2, TLR-4, TLR-9 and TLR-11 were significantly increased in mouse IECs following infection with Toxoplasma gondii on day 8 postinfection. In contrast, expression of TLRs was significantly decreased in infected mice subjected to cold water stress (CWS + INF). Expression of TLR-9 and TLR-11 in the mouse MODE-K cell line was significantly increased after infection. Expression of TLR-9 and TLR-11 in cells exposed to norepinephrine (NE) and parasites was significantly decreased when compared to cells exposed to parasites only. A significant increase was observed in SIGIRR, a negative regulator of TLRs in the CWS + INF group when compared to the INF group. Stress components were able to decrease expression levels of TLRs in IECs, decrease parasite load, and increase expression of a negative regulator thereby ameliorating intestinal inflammatory responses commonly observed during per oral T. gondii infection in C57BL/6 mice.

Dilational rheology of monolayers of a miscible polymer blend: from good- to poor-solvent conditions.

The viscoelastic moduli (elasticity and dilational viscosity) of monolayers of PVAc + P4HS has been studied over a broad frequency range (0.1 mHz-200 kHz) using a combination of relaxation and capillary-waves techniques. The analysis of the surface pressure, the elasticity and the viscosity on the semidilute regime show that the air-water interface is a good solvent for the monolayers of PVAc-rich blends, and a poor (near-Theta) solvent for the monolayers of P4HS-rich blends. The solvent quality changes continuously over a broad concentration range. The results of viscoelastic moduli show that there is a broad relaxation process in the low-frequency range (omega < 1 Hz). While for PVAc-rich monolayers this relaxation process follows the reptation-like behavior described by Noskov, for P4HS-rich monolayers the model does not describe the amplitudes of the different relaxation modes. For PVAc-rich monolayers two processes are clearly distinguished at higher frequencies: one centered at around 500 Hz and another one at around 40 kHz. However, for P4HS-rich monolayers only one broad relaxation mode is found below 1 kHz. The crossover from one type of behavior to the other one takes place in a very narrow blend-composition range, and is not clearly related to the crossover from good- to poor-solvent condition.

Toxoplasma gondii: cold stress-induced modulation of antibody responses.

Physical or psychological stressors have been shown to have significant consequences in the immune function and the outcome of disease in human and animal models. Recent work has demonstrated that products released during stress, such as glucocorticoids and catecholamines, can profoundly influence the in vitro growth of pathogens by modulating immune responses. The present study examined the effects of a physical stressor (cold stress) on antigens of Toxoplasma gondii that elicits an antibody-mediated immune response during the acute and chronic phases of infection. Sera obtained from different groups of mice subjected to cold stress during the acute and chronic phases of T. gondii infection were used to measure the levels of antibodies and to localize by Western blot the dominant antigens eliciting IgG and IgM antibody responses. Serum antibodies collected from stressed and infected mice recognized antigens different from those recognized by infected mice without stress. During the acute phase, a stronger IgM antibody response against antigens of 30, 42, 54, and 60 kDa was detected in stressed animals at 3 weeks postinfection. In addition, a 5-kDa antigen was specifically detected in mice subjected to stress during the acute and chronic phases of infection. Levels of specific IgG were increased in infected and in infected and stressed animals that underwent stress in the chronic phase. IgM production did not increase following cold stress in the chronic phase. These results suggest that the strong antibody response in stressed animals is associated with longer parasite persistence in circulation. Stress modulated not only the host immune response but also the ability of parasite antigens to elicit specific antibody responses by the host.

Acute toxoplasmosis leads to lethal overproduction of Th1 cytokines.

Virulence in Toxoplasma gondii is strongly influenced by the genotype of the parasite. Type I strains uniformly cause rapid death in mice regardless of the host genotype or the challenge dose. In contrast, the outcome of infections with type II strains is highly dependent on the challenge dose and the genotype of the host. To understand the basis of acute virulence in toxoplasmosis, we compared low and high doses of the RH strain (type I) and the ME49/PTG strain (type II) of T. gondii in outbred mice. Differences in virulence were reflected in only modestly different growth rates in vivo, and both strains disseminated widely to different tissues. The key difference in the virulent RH strain was the ability to reach high tissue burdens rapidly following a low dose challenge. Lethal infections caused by type I (RH) or type II (PTG) strain infections were accompanied by extremely elevated levels of Th1 cytokines in the serum, including IFN-gamma, TNF-alpha, IL-12, and IL-18. Extensive liver damage and lymphoid degeneration accompanied the elevated levels of cytokines produced during lethal infection. Increased time of survival following lethal infection with the RH strain was provided by neutralization of IL-18, but not TNF-alpha or IFN-gamma. Nonlethal infections with a low dose of type II PTG strain parasites were characterized by a modest induction of Th1 cytokines that led to control of infection and minimal damage to host tissues. Our findings establish that overstimulation of immune responses that are normally necessary for protection is an important feature of acute toxoplasmosis.

Immunomodulatory effects of cold stress on mice infected intraperitoneally with a 50% lethal dose of Toxoplasma gondii.

UNLABELLED: Cofactors such as stress have been suspected to play a role in the susceptibility to opportunistic infections. Toxoplasma gondii is one of the major opportunistic infectious agents in immunocompromised individuals, and infection can be modulated by external factors such as stress. OBJECTIVE: The purpose of this study was to examine the in vivo and in vitro role of cold stress (CS) in the pathogenesis of T. gondii infection and its impact on regulatory cytokines in this model. METHODS: Mice subjected to CS and control animals were infected intraperitoneally with an LD(50) of PD2 T. gondii tachyzoites, and the outcome of the infection was determined. In addition, peritoneal macrophages obtained from CS and non-stressed mice were infected in vitro with T. gondii. The number of infected macrophages, the number of intracellular parasites and the production of interferon (IFN)-gamma, interleukin (IL)-12, and tumor necrosis factor (TNF)-alpha were determined. RESULTS: CS applied before intraperitoneal inoculation increased susceptibility against T. gondii infection. Peritoneal cells from CS mice contained significantly higher numbers of intracellular parasites and infected macrophages compared to those from non-stressed animals. IFN-gamma production was initially high in the CS group but decreased significantly after 36 h. Opposite results were found in the non-stressed group. Macrophages from CS mice persistently produced high levels of TNF-alpha and IL-12 and peaked after 36 h. Levels of these cytokines were lower or absent in the non-stressed group. CONCLUSION: These results suggest that CS increased the host susceptibility to intraperitoneal T. gondii infection by modulating the function of macrophages and the production of cytokines (IFN-gamma) involved in the early control of infection.