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An analysis of the development and current state of the main instruments of liberalization of currency regulation and currency control has been carried out. The relevance of the topic is explained by the tendency of many countries to remove restrictions on foreign exchange transactions and the movement of capital funds in order to build an economy that is attractive to foreign investors and resistant to external influences. The development of the principles of capital movement liberalization at the international level, starting with the adoption of the OECD Code in 1961, is briefly considered. The experience of liberalization of monetary and financial regulation at the level of individual countries and integration associations is analyzed and generalized on the example of the USA, the European Union and the BRICS countries. The shortcomings of the current legislation of the Russian Federation in this area are identified and the conclusion is made about the need for further improvement of legislation in order to create a financial system that is resistant to external shocks and international sanctions pressure. The main reason for this is that the measures taken by Russia in 2022 to respond to sanctions do not include reform of federal legislation, but are based on the introduction of temporary restrictions on the foreign exchange market and are somewhat contradictory. In the context of strengthening external restrictions, and the introduction of retaliatory counter-sanction measures, it is necessary to develop new strategic planning documents in the field of monetary and financial regulation in order to ensure the stable functioning of the monetary and financial system.

The article deals with different approaches of transition to the strategy of “green” growth as a part of systemic government policy. The relevance of the topic is justified not only by the global trend and concern for creating favorable environmental conditions, but also by considerations of the depletion of fossil sources which lead to a necessity to search for alternative energy development. The article presents the analysis of the “green” growth strategy implementation in some countries with their regularities and common features identified, such as setting a goal to achieve carbon neutrality and large-scale investments in the development of alternative energy. In Russia, this policy is now being formed and the main stake is still placed on the use of hydrocarbon raw materials. It is concluded that for the formation of a systemic policy of “green” growth in the Russian Federation, deep socio-economic transformations and changes in environmental and tax legislation are required in order to ensure economic growth without increasing the burden on the environment. The development of the “green” growth lags behind other countries and requires its inclusion in the governmental social and economic policy.

International audience; TrackMate is an automated tracking software used to analyze bioimages and is distributed as a Fiji plugin. Here, we introduce a new version of TrackMate. TrackMate 7 is built to address the broad spectrum of modern challenges researchers face by integrating state-of-the-art segmentation algorithms into tracking pipelines. We illustrate qualitatively and quantitatively that these new capabilities function effectively across a wide range of bio-imaging experiments.

Centrioles are formed by microtubule triplets in a nine-fold symmetric arrangement. In flagellated protists and in animal multiciliated cells, accessory structures tethered to specific triplets render the centrioles rotationally asymmetric, a property that is key to cytoskeletal and cellular organization in these contexts. In contrast, centrioles within the centrosome of animal cells display no conspicuous rotational asymmetry. Here, we uncover rotationally asymmetric molecular features in human centrioles. Using ultrastructure expansion microscopy, we show that LRRCC1, the ortholog of a protein originally characterized in flagellate green algae, associates preferentially to two consecutive triplets in the distal lumen of human centrioles. LRRCC1 partially co-localizes and affects the recruitment of another distal component, C2CD3, which also has an asymmetric localization pattern in the centriole lumen. Together, LRRCC1 and C2CD3 delineate a structure reminiscent of a filamentous density observed by electron microscopy in flagellates, termed the ‘acorn’. Functionally, the depletion of LRRCC1 in human cells induced defects in centriole structure, ciliary assembly and ciliary signaling, supporting that LRRCC1 cooperates with C2CD3 to organizing the distal region of centrioles. Since a mutation in the LRRCC1 gene has been identified in Joubert syndrome patients, this finding is relevant in the context of human ciliopathies. Taken together, our results demonstrate that rotational asymmetry is an ancient property of centrioles that is broadly conserved in human cells. Our work also reveals that asymmetrically localized proteins are key for primary ciliogenesis and ciliary signaling in human cells.

TrackMate is an automated tracking software used to analyze bioimages and distributed as a Fiji plugin. Here we introduce a new version of TrackMate rewritten to improve performance and usability, and integrating several popular machine and deep learning algorithms to improve versatility. We illustrate how these new components can be used to efficiently track objects from brightfield and fluorescence microscopy images across a wide range of bio-imaging experiments.

Significance Listeria monocytogenes (Lm) is a bacterial pathogen that causes listeriosis, a foodborne disease characterized by gastroenteritis, meningitis, bacteremia, and abortions in pregnant women. The most severe human listeriosis outbreaks are associated with a subset of Lm hypervirulent clones that encode the bacteriocin Listeriolysin S (LLS), which modifies the gut microbiota and allows efficient Lm gut colonization and invasion of deeper organs. Our present work identifies the killing mechanism displayed by LLS to outcompete gut commensal bacteria, demonstrating that it induces membrane permeabilization and membrane depolarization of target bacteria. Moreover, we show that LLS is a thiazole/oxazole–modified microcin that displays a contact-dependent inhibition mechanism., Listeriolysin S (LLS) is a thiazole/oxazole–modified microcin (TOMM) produced by hypervirulent clones of Listeria monocytogenes. LLS targets specific gram-positive bacteria and modulates the host intestinal microbiota composition. To characterize the mechanism of LLS transfer to target bacteria and its bactericidal function, we first investigated its subcellular distribution in LLS-producer bacteria. Using subcellular fractionation assays, transmission electron microscopy, and single-molecule superresolution microscopy, we identified that LLS remains associated with the bacterial cell membrane and cytoplasm and is not secreted to the bacterial extracellular space. Only living LLS-producer bacteria (and not purified LLS-positive bacterial membranes) display bactericidal activity. Applying transwell coculture systems and microfluidic-coupled microscopy, we determined that LLS requires direct contact between LLS-producer and -target bacteria in order to display bactericidal activity, and thus behaves as a contact-dependent bacteriocin. Contact-dependent exposure to LLS leads to permeabilization/depolarization of the target bacterial cell membrane and adenosine triphosphate (ATP) release. Additionally, we show that lipoteichoic acids (LTAs) can interact with LLS and that LTA decorations influence bacterial susceptibility to LLS. Overall, our results suggest that LLS is a TOMM that displays a contact-dependent inhibition mechanism.

Tip growth is critical for the lifestyle of many walled cells. In yeast and fungi, this process is typically associated with the polarized deposition of conserved tip factors, including landmarks, Rho GTPases, cytoskeleton regulators, and membrane and cell wall remodelers. Because tip growth speeds may vary extensively between life cycles or species, we asked whether the local amount of specific polar elements could determine or limit tip growth speeds. Using the model fission yeast, we developed a quantitative image analysis pipeline to dynamically correlate single tip elongation speeds and polar protein abundance in large data sets. We found that polarity landmarks are typically diluted by growth. In contrast, tip growth speed is positively correlated with the local amount of factors related to actin, secretion or cell wall remodeling, but, surprisingly, exhibits long saturation plateaus above certain concentrations of those factors. Similar saturation observed for Spitzenkörper components in much faster growing fungal hyphae suggests that elements independent of canonical surface remodelers may limit single tip growth. This work provides standardized methods and resources to decipher the complex mechanisms that control cell growth. This article has an associated First Person interview with Sarah Taheraly, joint first author of the paper.

The article presents an analysis of the development and current state of monetary and financial regulation in the context of the economic policies of Chile, Mexico and Brazil. The article is focused at the processes of liberalization of foreign exchange regulation in order to create more favorable conditions for the development of foreign trade, support for exporters and building a reliable prudential system. It is concluded that in the reviewed countries, the policy regarding the lifting of restrictions in order to support and develop export potential had been carried out consistently. The successful experience of these countries in the field of monetary and financial regulation deserves attention, as it shows their ability to maintain financial and economic stability, withstand external shocks and strengthen their positions in world trade.

International audience; Most animals exhibit mirror-symmetric body plans, yet the molecular constituents from which they are formed are often chiral. In planarian flatworms, centrioles are arranged in a bilaterally symmetric pattern across the ventral epidermis. Here, we found that this pattern is generated by a network of centrioles with prominent chiral asymmetric properties. We identify centriole components required for establishing asymmetric connections between centrioles and balancing their effects to align centrioles along polarity fields. SMED-ODF2, SMED-VFL1, and SMED-VFL3 affect the assembly of centriole appendages that tether cytoskeletal connectors to position the centrioles. We further show that the medio-lateral polarization of centrioles relies on mechanisms that are partly distinct on the left and right sides of the planarian body. Our findings shed light on how bilaterally symmetrical patterns can emerge from chiral cellular organizations.

The division patterns of early invertebrate and vertebrate embryos are key to the specification of cell fates and embryo body axes. We here describe a generic computational modeling method to quantitatively test mechanisms which specify successive division position and orientation of eggs and early blastomeres in 3D. This approach should serve to motivate and guide future experimental work on the mechanisms controlling early embryo morphogenesis.

International audience; The division patterns of early invertebrate and vertebrate embryos are key to the specification of cell fates and embryo body axes. We here describe a generic computational modeling method to quantitatively test mechanisms which specify successive division position and orientation of eggs and early blastomeres in 3D. This approach should serve to motivate and guide future experimental work on the mechanisms controlling early embryo morphogenesis.

SUMMARYHow growing cells cope with size expansion while ensuring mechanical integrity is not known. In walled cells, such as those of microbes and plants, growth and viability are both supported by a thin and rigid encasing cell wall (CW). We deciphered the dynamic mechanisms controlling wall surface assembly during cell growth, using a novel sub-resolution microscopy approach to monitor CW thickness in live rod-shaped fission yeast cells. We found that polar cell growth yielded wall thinning, and that thickness negatively influenced growth. Thickness at growing tips exhibited oscillating behavior with thickening phases followed by thinning phases, indicative of a delayed feedback promoting thickness homeostasis. This feedback was mediated by mechanosensing through the cell wall integrity pathway, which probes strain in the wall to adjust synthase localization and activity to surface growth. Mutants defective in thickness homeostasis lysed by rupturing the wall demonstrating its essential role for walled cell survival.

Most animals exhibit mirror-symmetric body plans, yet the molecular constituents from which they are formed are often chiral. In planarian flatworms, centrioles are arranged in a bilaterally symmetric pattern across the ventral epidermis. Here, we found that this pattern is generated by a network of centrioles with prominent left-right asymmetric properties. We identify centriole components required for establishing left-right asymmetric connections between centrioles and balancing their effects to align centrioles along polarity fields. We show that the asymmetry of the network is also compensated by specific interactions of its components with polarity cues on the left and right sides of the planarian body. Our findings shed new light on how bilateral symmetry can emerge from chiral cellular organizations.

Vegetation models are essential tools for projecting large-scale land-cover response to changing climate, which is expected to alter the distribution of biomes and individual species. A large-scale bioclimatic envelope model (RuBCliM) and an individual species based gap model (UVAFME) are used to simulate the Russian forests under current and future climate for two greenhouse gas emissions scenarios. Results for current conditions are compared between models and assessed against two independent maps of Russian forest biomes and dominant tree species. Comparisons measured with kappa statistics indicate good agreement between the models (kappa values from 0.76 to 0.69), as well as between the model results and two observation-based maps for both species presence and absence (kappa values from 0.70 to 0.43). Agreement between these multiple types of data on forest distribution provides confidence in the projected forest response to changing climate. For future conditions, both models indicate a shift in the dominant biomes from conifers to deciduous leaved species. These projections have implications for feedbacks between the energy budget, carbon cycle, and land cover in the boreal system. The distinct biome and species changes emphasize the need for continued investigation of this landmass that has the size necessary to influence regional and global climate.

In this paper we describe a new approach to quantify the stability and coalescence kinetics of thermally switchable emulsions using an imaging-based microcentrifugation method. We first show that combining synchronized high-speed imaging with microfluidic centrifugation allows the direct measurement of the thermodynamic stability of emulsions, as expressed by the critical disjoining pressure. We apply this to a thermoresponsive emulsion, allowing us to measure the critical disjoining pressure as a function of temperature. The same method, combined with quantitative image analysis, also gives access to droplet-scale details of the coalescence process. We illustrate this by measuring temperature-dependent coalescence rates and by analysing the temperature-induced switching between two distinct microscopic mechanisms by which dense emulsions can destabilise to form a homogeneous oil phase.

Surface charge is often hypothesized to influence toxicity of nanoparticles (NPs) including polymeric nanoparticles (PNPs) while oxidative stress is considered to be an important mode of action (MOA) for such toxicity. In order to investigate the role of membrane disturbance and oxidative stress in the MOA of PNPs, the cytotoxicity and a range of related cellular endpoints induced by monodisperse, fluorescent, cationic and anionic polystyrene nanoparticles (PSNPs) of 50 and 100 nm sizes were investigated in vitro in macrophage NR8383 cells. Only amine-terminated cationic PSNPs exhibited cytotoxicity which was accompanied by induction of intracellular reactive oxygen species (ROS), increased levels of cytoplasmic free calcium, a reduced phagocytic index, a reduced mitochondrial membrane potential (ΔΨm) and a decreased intracellular ATP content with the effects being more pronounced for 50 nm than 100 nm PSNPs. Both cationic and anionic PSNPs were found to increase the roughness of the cell membrane with the effect being more profound for cationic PSNPs. The pattern of protection by cellular antioxidants against the effects induced by positive PSNPs was similar to the pattern of protection against effects induced by the mitochondrial electron transport disrupting agent 2,4-dinitrophenol (DNP) and dissimilar to that for protection against the model compound for oxidative stress, i.e. hydrogen peroxide (H2O2). Surface charge influences the cellular interaction for NPs. The results collectively indicated that membrane interaction, and disturbance of the mitochondrial electronic transport chain (ETC) may represent a principal mechanism of toxicity for cationic PSNPs resulting in ROS production and oxidative stress as secondary effects.

Objects floating at a liquid interface, such as breakfast cereals floating in a bowl of milk or bubbles at the surface of a soft drink, clump together as a result of capillary attraction. This attraction arises from deformation of the liquid interface due to gravitational forces; these deformations cause excess surface area that can be reduced if the particles move closer together. For micrometer-sized colloids, however, the gravitational force is too small to produce significant interfacial deformations, so capillary forces between spherical colloids at a flat interface are negligible. Here, we show that this is different when the confining liquid interface has a finite curvature that is also anisotropic. In that case, the condition of constant contact angle along the three-phase contact line can only be satisfied when the interface is deformed. We present experiments and numerical calculations that demonstrate how this leads to quadrupolar capillary interactions between the particles, giving rise to organization into regular square lattices. We demonstrate that the strength of the governing anisotropic interactions can be rescaled with the deviatoric curvature alone, irrespective of the exact shape of the liquid interface. Our results suggest that anisotropic interactions can easily be induced between isotropic colloids through tailoring of the interfacial curvature.

We report an experimental method to investigate droplet dynamics in centrifuged emulsions and its application to study droplet compression and coalescence. The experimental setup permits in situ monitoring of an ensemble of droplets in a centrifuged monolayer of monodisperse emulsion droplets using optical microscopy. We studied a hexadecane-in-water emulsion stabilized by the ionic surfactant sodium-n-dodecyl sulfate as a model system. With a microfluidic T-junction emulsion droplets of 97 mm diameter are produced which are subsequently inserted into a rectangular glass chamber of 100 mm height. Using an emulsion which is stable against coalescence, we measured the steady-state oil volume fraction in the compressed layer as a function of the compressive force induced by centrifugation, and quantified the deformation of droplets upon compression. To induce coalescence, we decreased the SDS bulk concentration by dilution of the continuous phase with water before the start of centrifugation. The growth rate of the separated oil phase, which forms on top of the emulsion, and the extent of drop–drop coalescence in the droplet layer upon centrifugation were evaluated as a function of the radial acceleration. The potential of the method for studies in emulsion science and possible improvements of the experimental setup are discussed.

Microorganisms have developed an elaborate spectrum of mechanisms to respond and adapt to environmental stress conditions. Among these is the expression of dps , coding for the D NA-binding p rotein from s tarved cells. Dps becomes the dominant nucleoid-organizing protein in stationary-phase Escherichia coli cells and is required for robust survival under stress conditions, including carbon or nitrogen starvation, oxidative stress, metal exposure, and irradiation. To study the complex regulation of Dps in E. coli , we utilized time-lapse fluorescence microscopy imaging to examine the kinetics, input encoding, and variability of the Dps response in single cells. In the presence of an oxidative stressor, we observed a single pulse of activation of Dps production. Increased concentrations of H 2 O 2 led to increased intensity and duration of the pulse. While lower concentrations of H 2 O 2 robustly activated the Dps response with little effect on the growth rate, higher concentrations of H 2 O 2 resulted in dramatically lower and highly varied growth rates. A comparison of cells exposed to the same concentration of H 2 O 2 revealed that increased levels of Dps expression did not confer a growth advantage, indicating that recovery from stress may rely primarily upon variation in the amount of damage caused to individual cells. IMPORTANCE We show for the first time the response of the DNA-binding protein from starved cells (Dps) to oxidative stress in single cells of E. coli . Through time-lapse fluorescence microscopy, a single pulse of Dps production is observed in cells exposed to H 2 O 2 , with a duration and intensity of induction proportional to the concentration of the applied stress. More intense Dps expression did not provide a growth benefit to the bacteria, suggesting that healing from oxidative stress may largely depend upon the amount of damage in each individual cell.

International audience; To understand droplet formation and stabilisation, technologies are needed to measure interfacial tension at micrometer range and millisecond scale. In this paper, microtechnology is used, and that allows us to access these ranges and derive a model for surfactant free systems. The predicting power of the model was tested, and we found that it can be used to accurately (validated with >60 experiments) describe droplet size for a wide range of flow rates, interfacial tensions, and continuous phase viscosities. The model was used next to determine interfacial tensions in a system with hexadecane and sodium dodecylsulfate (SDS) solutions, and it was found that the model can be used for droplet formation times ranging from 0.4 to 9.4ms while using a wide range of process conditions. The method described here differs greatly from standard dynamic interfacial tension methods that use quiescent, mostly diffusion-limited situations. The effects that we measured are much faster due to enhanced mass transfer; this allows us to assess the typical time scales used in industrial emulsification devices.

This paper presents an overview of current satellite-based fire mapping activities at several institutions in Russia that provide operational fire monitoring at federal and regional levels. The current operational systems are based on data from the Advanced Very High Resolution Radiometer (AVHRR) and the TIROS Operational Vertical Sounder (TOVS) on the National Atmospheric and Oceanic Administration (NOAA) operational polar orbiting environmental satellite series. Detailed descriptions of the data acquisition and preprocessing systems, algorithms, and the suite of fire products are provided. Each institution has expertise in addressing a specific aspect of satellite-based fire mapping and monitoring. The methodologies described include proper georegistration of AVHRR data and elimination of false alarms while retaining a high active fire detection rate. Statistical and physical approaches are presented to account for, among other effects, reflection from bright surfaces and clouds, sun-glint, and atmospheric attenuation by smoke and haze. An approach for fire danger estimation is also presented. The fire mapping activities at the various institutions are being organized into a regional network within the international Global Observation of Forest and Landcover Dynamics (GOFC/GOLD) program. Concerted efforts will facilitate the implementation of processing systems for new and improved sensors, such as the Moderate Resolution Imaging Spectroradiometer (MODIS) on the experimental NASA Earth Observing System Terra and Aqua satellites and the Visible/Infrared/Imager/Radiometer Suite on the next generation National Polar Orbiting Environmental Satellite System (NPOESS).

Sensitivity of immune cells (coelomocytes) of Lumbricus rubellus earthworms was investigated for exposure to selected nanoparticles, in order to obtain further insight in mechanisms of effects observed after in vivo C60 exposure. In the in vivo study, tissue damage appeared to occur without accompanying increased immune responses. Coelomocytes exposed in vitro to C60 showed no decrease of their cellular viability, but demonstrated a decrease in gene expression of the cytokine-like protein CCF-1, indicating immunosuppression. Experiments with NR8383 rat macrophage cells and tri-block copolymer nanoparticles were used to compare sensitivity and to demonstrate the usefulness of coelomocytes as a test system for nano-immunotoxicity, respectively. Overall, the results imply that sensitivity towards nanoparticles differs between cell types and nanoparticles. Moreover, this study indicates that injuries in absence of an immune response, observed after in vivo C60 exposure in our earlier work, are caused by immunosuppression rather than coelomocyte mortality.

We report two different modes of phase inversion in surfactant-stabilized oil-in-water emulsions subjected to a unidirectional drying stress. Coalescence occurs either through a nucleation-and-growth mechanism, where coalesced pockets form and grow randomly throughout the sample, or through a coalescence front that propagates into the sample from the drying end. This drying-induced coalescence results from the development of a pressure gradient from the drying front into the bulk of the sample, established by limited water transport through the Plateau borders. Depending on the steepness of this pressure profile, coalescence occurs throughout the sample or only at the drying front. Moreover, we find that surfactant concentration plays a significant role through its effect on the critical disjoining pressure at which coalescence occurs. Very stable emulsions, characterized by a high critical pressure, tend to develop steep pressure profiles, which favours front-dominated coalescence, while unstable emulsions with low critical pressures develop shallow pressure gradients, favouring nucleation-and-growth dominated coalescence. These results offer new insights into the microscopic mechanisms governing the complex and poorly understood macroscopic phenomena during phase inversion of drying emulsions.

Rising temperatures may force boreal forests in central Siberia to transition to alternative ecological states, affecting species composition and carbon storage dynamics. A full understanding of how forests of different ages respond to warming remains elusive, despite being fundamental for proper forest management in the region. To document the sensitivity of Siberian forests of different successional stages to rising temperatures. We use the FAREAST forest gap model to investigate the variation in biophysical response of boreal forests of different stand ages as temperatures rise and question whether there is varying sensitivity at different successional states. Our model predicts that mid-successional forests are more resistant to warming temperatures in low-level warming scenarios and resist biophysical changes more so than forests over 200 years old. This response diminished in more intense warming scenarios. Specifically, forest biomass increased with temperature; however, dieback of Siberian larch and replacement by Siberian Silver birch and by Siberian pine in early-successional stands yielded a net decrease in carbon storage. Mid-succession and old growth forests did not transition to pine forests, however, and may serve as a location for refugia of northern boreal species.

BackgroundPolymer nanoparticles (PNP) are becoming increasingly important in nanomedicine and food-based applications. Size and surface characteristics are often considered to be important factors in the cellular interactions of these PNP, although systematic investigations on the role of surface properties on cellular interactions and toxicity of PNP are scarce.ResultsFluorescent, monodisperse tri-block copolymer nanoparticles with different sizes (45 and 90 nm) and surface charges (positive and negative) were synthesized, characterized and studied for uptake and cytotoxicity in NR8383 and Caco-2 cells. All types of PNP were taken up by the cells. The positive smaller PNP45(45 nm) showed a higher cytotoxicity compared to the positive bigger PNP90(90 nm) particles including reduction in mitochondrial membrane potential (ΔΨm), induction of reactive oxygen species (ROS) production, ATP depletion and TNF-α release. The negative PNP did not show any cytotoxic effect. Reduction in mitochondrial membrane potential (ΔΨm), uncoupling of the electron transfer chain in mitochondria and the resulting ATP depletion, induction of ROS and oxidative stress may all play a role in the possible mode of action for the cytotoxicity of these PNP. The role of receptor-mediated endocytosis in the intracellular uptake of different PNP was studied by confocal laser scanning microscopy (CLSM). Involvement of size and charge in the cellular uptake of PNP by clathrin (for positive PNP), caveolin (for negative PNP) and mannose receptors (for hydroxylated PNP) were found with smaller PNP45showing stronger interactions with the receptors than bigger PNP90.ConclusionsThe size and surface characteristics of polymer nanoparticles (PNP; 45 and 90 nm with different surface charges) play a crucial role in cellular uptake. Specific interactions with cell membrane-bound receptors (clathrin, caveolin and mannose) leading to cellular internalization were observed to depend on size and surface properties of the different PNP. These properties of the nanoparticles also dominate their cytotoxicity, which was analyzed for many factors. The effective reduction in the mitochondrial membrane potential (ΔΨm), uncoupling of the electron transfer chain in mitochondria and resulting ATP depletion, induction of ROS and oxidative stress likely all play a role in the mechanisms behind the cytotoxicity of these PNP.

There have been various attempts to investigate the mechanical properties of the actin cortex in cells, but the factors that control them remain poorly understood. To make progress, we develop a reconstituted model of the actin cortex that mimics its structure. We attach actin filaments to lipids lining the surface of an oil droplet using biotin–streptavidin bonds. In this way we can form a thin actin network that can be visualized and studied by confocal microscopy. Our approach allows incorporation of different actin-binding and motor proteins into this 2D network and characterization of their effect on its mechanical properties in a quantitative way. To study the viscoelasticity of the network, we use passive particle tracking microrheology, which allows storage and loss moduli to be extracted from the mean square displacement of tracer particles. We show that adding cross-linkers to the cortex increases its elasticity by several orders of magnitude and addition of myosin in the presence of ATP results in a strong and rapid stiffening of the network. This approach opens up a variety of possibilities to study viscoelastic properties of the actin cortex in vitro, allowing incorporation of any protein of interest into the system.

A series of monodisperse (45 ± 5 nm) fluorescent nanoparticles from tri-block copolymers (polymeric nanoparticles (PNPs)) bearing different surface charges were synthesised and investigated for cytotoxicity in NR8383 and Caco-2 cells. The positive PNPs were more cytotoxic and induced a higher intracellular reactive oxygen species production than the neutral and negative ones. The cytotoxicity of positive PNPs with quaternary ammonium groups decreased with increasing steric bulk. The intracellular uptake and cellular interactions of these different PNPs were also tested in NR8383 cells by confocal laser scanning microscopy, which revealed higher uptake for positive than for negative PNPs. Also positive PNPs were found to interact much more with cell membranes, whereas the negative PNPs were internalised mainly by lysosomal endocytosis. Uptake of positive PNPs decreased with increasing steric bulk around the positive charge. A surface charge-specific interaction of clathrin for positive PNPs and caveolin receptors for negative PNPs was observed. These findings confirm that surface charge is important for the cytotoxicity of these PNPs, while they additionally point to considerable additional effects of the steric shielding around positive charges on PNP cytotoxicity.

Biomass burning constitutes a major contribution to global emissions of carbon dioxide, carbon monoxide, methane, greenhouse gases and aerosols. Furthermore, biomass burning has an impact on health, transport, the environment and land use. Vegetation fires are certainly not recent phenomena and the impacts are not always negative. However, evidence suggests that fires are becoming more frequent and there is a large increase in the number of fires being set by humans for a variety of reasons. Knowledge of the interactions and feedbacks between biomass burning, climate and carbon cycling is needed to help the prediction of climate change scenarios. To obtain this knowledge, the scientific community requires, in the first instance, information on the spatial and temporal distribution of biomass burning at the global scale. This paper presents an inventory of burned areas at monthly time periods for the year 2000 at a resolution of 1 kilometer (km) and is available to the scientific community at no cost. The burned area products have been derived from a single source of satellite-derived images, the SPOT VEGETATION S1 1 km product, using algorithms developed and calibrated at regional scales by a network of partners. In this paper, estimates of burned area, number of burn scars and average size of the burn scar are described for each month of the year 2000. The information is reported at the country level. This paper makes a significant contribution to understanding the effect of biomass burning on atmospheric chemistry and the storage and cycling of carbon by constraining one of the main parameters used in the calculation of gas emissions.

[1] The scientific community interested in atmospheric chemistry, gas emissions from vegetation fires, and carbon cycling is currently demanding information on the extent and timing of biomass burning at the global scale. In fact, the area and type of vegetation that is burned on a monthly or annual basis are two of the parameters that provide the greatest uncertainty in the calculation of gas and aerosol emissions and burned biomass. To address this need, an inventory of burned areas at monthly time periods for the year 2000 at a resolution of 1 km2 has been produced using satellite data and has been made freely available to the scientific community. In this paper, estimates of burned area and number of burn scars for four broad vegetation classes and reported at the country level for the year 2000 are presented using data taken from the inventory. Over 3.5 million km2 of burned areas were detected in the year 2000, of which approximately 80% occurred in areas described as woodlands and shrublands. Approximately 17% of the burned area occurred in grasslands and croplands, the remaining 3% occurred in forests. Almost 600,000 separate burn scars were detected. Descriptions of vegetation burning activity are given for ten regions. Finally, monthly burned area estimates are presented for the Central African Republic to illustrate the usefulness of these data for understanding, monitoring and managing vegetation burning activities.

International audience; Asymmetric divisions are essential for the generation of cell fate and size diversity. They implicate cortical domains where minus end–directed motors, such as dynein, are activated to pull on microtubules to decenter asters attached to centrosomes, nuclei, or spindles. In asymmetrically dividing cells, aster decentration typically follows a centering phase, suggesting a time-dependent regulation in the competition between microtubule centering and decentering forces. Using symmetrically dividing sea urchin zygotes, we generated cortical domains of magnetic particles that spontaneously cluster endogenous dynein activity. These domains efficiently attract asters and nuclei, yielding marked asymmetric divisions. Remarkably, aster decentration only occurred after asters had first reached the cell center. Using intracellular force measurement and models, we demonstrate that this time-regulated imbalance results from a global reduction of centering forces rather than a local maturation of dynein activity at the domain. Those findings define a novel paradigm for the regulation of division asymmetry.

Summary Polar cell growth is a conserved morphogenetic process needed for survival, mating, and infection [ 1 , 2 ]. It typically implicates the assembly and spatial stabilization of a cortical polar domain of the active form of a small GTPase of the Rho family, such as Cdc42, which promotes cytoskeleton assembly and secretion needed for local surface expansion [ 3 , 4 , 5 , 6 ]. In multiple physiological instances, polarity domains may switch from being spatially unstable, exhibiting a wandering behavior around the cell surface, to being stable at a fixed cellular location [ 7 , 8 , 9 , 10 , 11 ]. Here, we show that the rate of surface growth may be a key determinant in controlling the spatial stability of active Cdc42 domains. Reducing the growth rate of single rod-shaped fission yeast cells using chemical, genetic, and mechanical means systematically causes polar domains to detach from cell tips and oscillate around the cell surface within minutes. Conversely, an abrupt increase in growth rate improves domain stabilization. A candidate screen identifies vesicular transport along actin cables as an important module mediating this process. Similar behavior observed in distant filamentous fungi suggests that this positive feedback between growth and polarity could represent a basal property of eukaryotic polarization, promoting persistent polar growth as well as growth redirection with respect to the mechanical environment of cells.

Hematopoietic stem and progenitor cells (HSPCs) emerge from the aorta and migrate to the caudal hematopoietic tissue (CHT) of zebrafish larvae, the hematopoietic equivalent of the mammalian fetal liver, for their proliferation and differentiation. We previously reported that somite-derived stromal cells were a key component of the CHT niche. Here we found that the cell adhesion protein protocadherin-18a (Pcdh18a) is expressed in the stromal cell progenitors (SCPs) emigrating from somites toward the future CHT. Deletion of most of the intracellular domain of Pcdh18a caused a decrease in the number of SCPs, the directionality of their migration, and the cell-contact mediated repulsion that normally occurs between migrating SCPs. These defects were followed by abnormal morphogenesis of the venous plexus that forms the CHT framework, and the inability of the resulting CHT to function as a niche for HSPCs. Finally, we found that the extracellular domain of Pcdh18a mediates trans heterophilic adhesion of stromal cells to endothelial cells in vivo and thereby the reticular vs. perivascular fate of SCPs. Our study demonstrates that Pcdh18a expression in SCPs is essential for the proper development of the hematopoietic niche.