Microstructural model for cyclic hardening in F-actin networks crosslinked by α-actinin

open2siThe rheology of F-actin networks has attracted a great attention during the last years. In order to gain a complete understanding of the rheological properties of these novel materials, it is necessary the study in a large deformations regime to alter their internal structure. In this sense, Schmoller et al. (2010) showed that the reconstituted networks of F-actin crosslinked with α-actinin unexpectedly harden when they are subjected to a cyclical shear. This observation contradicts the expected Mullins effect observed in most soft materials, such as rubber and living tissues, where a pronounced softening is observed when they are cyclically deformed. We think that the key to understand this stunning effect is the gelation process. To define it, the most relevant constituents are the chemical crosslinks - α-actinin -, the physical crosslinks - introduced by the entanglement of the semiflexible network - and the interaction between them. As a consequence of this interaction, a pre-stressed network emerges and introduces a feedback effect, where the pre-stress also regulates the adhesion energy of the α-actinin, setting the structure in a metastable reference configuration. Therefore, the external loads and the evolvement of the trapped stress drive the microstructural changes during the cyclic loading protocol. In this work, we propose a micromechanical model into the framework of nonlinear continuum mechanics. The mechanics of the F-actin filaments is modelled using the wormlike chain model for semiflexible filaments and the gelation process is modelled as mesoscale dynamics for the α-actinin and physical crosslink. The model has been validated with reported experimental results.López-Menéndez, Horacio; Rodríguez, José FélixLópez Menéndez, Horacio; RODRIGUEZ MATAS, JOSE FELI

Multiple particle tracking analysis in isolated nuclei reveals the mechanical phenotype of leukemia cells.

The nucleus is fundamentally composed by lamina and nuclear membranes that enclose the chromatin, nucleoskeletal components and suspending nucleoplasm. The functional connections of this network integrate external stimuli into cell signals, including physical forces to mechanical responses of the nucleus. Canonically, the morphological characteristics of the nucleus, as shape and size, have served for pathologists to stratify and diagnose cancer patients; however, novel biophysical techniques must exploit physical parameters to improve cancer diagnosis. By using multiple particle tracking (MPT) technique on chromatin granules, we designed a SURF (Speeded Up Robust Features)-based algorithm to study the mechanical properties of isolated nuclei and in living cells. We have determined the apparent shear stiffness, viscosity and optical density of the nucleus, and how the chromatin structure influences on these biophysical values. Moreover, we used our MPT-SURF analysis to study the apparent mechanical properties of isolated nuclei from patients of acute lymphoblastic leukemia. We found that leukemia cells exhibited mechanical differences compared to normal lymphocytes. Interestingly, isolated nuclei from high-risk leukemia cells showed increased viscosity than their counterparts from normal lymphocytes, whilst nuclei from relapsed-patient's cells presented higher density than those from normal lymphocytes or standard- and high-risk leukemia cells. Taken together, here we presented how MPT-SURF analysis of nuclear chromatin granules defines nuclear mechanical phenotypic features, which might be clinically relevant.post-print1994 K

Moulding hydrodynamic 2D-crystals upon parametric Faraday waves in shear-functionalized water surfaces.

Faraday waves, or surface waves oscillating at half of the natural frequency when a liquid is vertically vibrated, are archetypes of ordering transitions on liquid surfaces. Although unbounded Faraday waves patterns sustained upon bulk frictional stresses have been reported in highly viscous fluids, the role of surface rigidity has not been investigated so far. Here, we demonstrate that dynamically frozen Faraday waves—that we call 2D-hydrodynamic crystals—do appear as ordered patterns of nonlinear gravity-capillary modes in water surfaces functionalized with soluble (bio)surfactants endowing in-plane shear stiffness. The phase coherence in conjunction with the increased surface rigidity bears the Faraday waves ordering transition, upon which the hydrodynamic crystals were reversibly molded under parametric control of their degree of order, unit cell size and symmetry. The hydrodynamic crystals here discovered could be exploited in touchless strategies of soft matter and biological scaffolding ameliorated under external control of Faraday waves coherence.post-print3461 K

Alien species established in the Bay of Biscay suggest significant contribution of both fouling and dry ship compartments

IntroductionThe majority of studies on marine biosecurity focus on aquatic species, but invaders can also use dry ship compartments for dispersal; this pathway has been less explored than fouling or ballast water. Here we analysed the maritime traffic of the international Port of Gijon (south Bay of Biscay, Spain) as a case study.MethodsMain donor countries were identified from traffic data. From the Global Invasive Species Database, we detected a similar proportion of expected global alien invasive species (AIS) from fouling and containers pathways to be actually settled in the recipient region.ResultsThe AIS diversity transported via fouling was higher than that transported by containers. No significant difference between Australia, Brazil, Canada and South Africa in the proportion of global AIS actually transferred to Bay of Biscay supports the vision of port networks as a new ecosystem with multiple demes. Different AIS catalogues in the donor regions may explain a higher proportion of terrestrial AIS introduced via containers from Brazil and South Africa and marine AIS introduced via fouling.DiscussionA more careful surveillance of biota in dry ship compartments, including it in a future revision in the International Convention for Safe Containers, is recommended to reduce the contribution of shipping to biological invasions

Mechanics of epithelial closure over non-adherent environments

The closure of gaps within epithelia is crucial to maintain its integrity during biological processes such as wound healing and gastrulation. Depending on the distribution of extracellular matrix, gap closure occurs through assembly of multicellular actin-based contractile cables or protrusive activity of border cells into the gap. Here we show that the supracellular actomyosin contractility of cells near the gap edge exerts sufficient tension on the surrounding tissue to promote closure of non-adherent gaps. Using traction force microscopy, we observe that cell-generated forces on the substrate at the gap edge first point away from the centre of the gap and then increase in the radial direction pointing into the gap as closure proceeds. Combining with numerical simulations, we show that the increase in force relies less on localized purse-string contractility and more on large-scale remodelling of the suspended tissue around the gap. Our results provide a framework for understanding the assembly and the mechanics of cellular contractility at the tissue level

Mechanical stress confers nuclear and functional changes in derived leukemia cells from persistent confined migration

20 p.-8 fig.Nuclear deformability plays a critical role in cell migration. During this process, the remodeling of internal components of the nucleus has a direct impact on DNA damage and cell behavior; however, how persistent migration promotes nuclear changes leading to phenotypical and functional consequences remains poorly understood. Here, we described that the persistent migration through physical barriers was sufficient to promote permanent modifications in migratory-altered cells. We found that derived cells from confined migration showed changes in lamin B1 localization, cell morphology and transcription. Further analysis confirmed that migratory-altered cells showed functional differences in DNA repair, cell response to chemotherapy and cell migration in vivo homing experiments. Experimental modulation of actin polymerization affected the redistribution of lamin B1, and the basal levels of DNA damage in migratory-altered cells. Finally, since major nuclear changes were present in migratory-altered cells, we applied a multidisciplinary biochemical and biophysical approach to identify that confined conditions promoted a different biomechanical response of the nucleus in migratory-altered cells. Our observations suggest that mechanical compression during persistent cell migration has a role in stable nuclear and genomic alterations that might handle the genetic instability and cellular heterogeneity in aging diseases and cancer.Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature. This research was supported by a FPI Scholarship 2018 (Ministerio de Ciencia e Innovación/MICINN, Agencia Estatal de Investigación/AEI y Fondo Europeo de Desarrollo Regional/FEDER) to R.G.N.; JAE Intro 2022 (Agencia Estatal Consejo Superior de Investigaciones Científicas, Conexión CSIC Cancer, JAE-ICU-CC-34 and JAEINT22_EX_0263) to G.P.C. and M.P.C.R; grants from the Ministerio de Ciencia e Innovación (MICINN) Agencia Estatal de Investigación (AEI) (RTI2018-097267-B-I00), Asociación Española Contra el Cáncer (LAB AECC, LABAE211656TORR) and Beca FERO (BFERO2021.01) to V.T.; Comunidad de Madrid (Y2018/BIO-5207) and from the Ministerio de Ciencia e Innovación (MICINN) Agencia Estatal de Investigación (AEI) (PID2020-115444 GB-I00) to P.R.N; grants from the Ministerio de Ciencia e Innovación (MICINN) Agencia Estatal de Investigación (AEI) (TED2021-132296B-C52, PID2019-108391RB-100), and Comunidad de Madrid (Y2018/BIO-5207, S2018/NMT-4389 and REACT-EU program PR38-21–28 ANTICIPA-CM) to F.M.; and grants from 2020 Leonardo Grant for Researchers and Cultural Creators (BBVA Foundation), Ayuda de contratación de ayudante de investigación PEJ-2020-AI/BMD-19152 (Comunidad de Madrid), Comunidad de Madrid (Y2018/BIO-5207) and the Ministerio de Ciencia e Innovación (MICINN) Agencia Estatal de Investigación (AEI) (PID2020-118525RBI00, AEI/10.13039/501100011033) to J.R.M.Peer reviewe

Impact of COVID-19 on cardiovascular testing in the United States versus the rest of the world

Objectives: This study sought to quantify and compare the decline in volumes of cardiovascular procedures between the United States and non-US institutions during the early phase of the coronavirus disease-2019 (COVID-19) pandemic. Background: The COVID-19 pandemic has disrupted the care of many non-COVID-19 illnesses. Reductions in diagnostic cardiovascular testing around the world have led to concerns over the implications of reduced testing for cardiovascular disease (CVD) morbidity and mortality. Methods: Data were submitted to the INCAPS-COVID (International Atomic Energy Agency Non-Invasive Cardiology Protocols Study of COVID-19), a multinational registry comprising 909 institutions in 108 countries (including 155 facilities in 40 U.S. states), assessing the impact of the COVID-19 pandemic on volumes of diagnostic cardiovascular procedures. Data were obtained for April 2020 and compared with volumes of baseline procedures from March 2019. We compared laboratory characteristics, practices, and procedure volumes between U.S. and non-U.S. facilities and between U.S. geographic regions and identified factors associated with volume reduction in the United States. Results: Reductions in the volumes of procedures in the United States were similar to those in non-U.S. facilities (68% vs. 63%, respectively; p = 0.237), although U.S. facilities reported greater reductions in invasive coronary angiography (69% vs. 53%, respectively; p < 0.001). Significantly more U.S. facilities reported increased use of telehealth and patient screening measures than non-U.S. facilities, such as temperature checks, symptom screenings, and COVID-19 testing. Reductions in volumes of procedures differed between U.S. regions, with larger declines observed in the Northeast (76%) and Midwest (74%) than in the South (62%) and West (44%). Prevalence of COVID-19, staff redeployments, outpatient centers, and urban centers were associated with greater reductions in volume in U.S. facilities in a multivariable analysis. Conclusions: We observed marked reductions in U.S. cardiovascular testing in the early phase of the pandemic and significant variability between U.S. regions. The association between reductions of volumes and COVID-19 prevalence in the United States highlighted the need for proactive efforts to maintain access to cardiovascular testing in areas most affected by outbreaks of COVID-19 infection

Caminos Alternativos para la Sostenibilidad y el Buen Vivir

En este texto, las diversas perspectivas presentadas en el marco del desarrollo sostenible plantean un tránsito a la sustentabilidad, y de ahí que se considere como una alternativa al buen vivir. Se plantean propuestas a partir de casos documentados que la sociedad organizada trabaja y que brindan alternativas desde su propia racionalidad y sentir, así como el rol del Estado en los procesos sociales en los territorios rurales. Asimismo, se exponen algunos casos de intervención vía políticas públicas y de cuando la sociedad organizada es autogestionaria, y logra proyectos con resultados de impacto que, si bien no son espectaculares, sí dejan huella en su ámbito local de origen