How individual cells respond to mechanical forces is of considerable interest to biologists as force affects many aspects of cell behaviour. The application of force on integrins triggers ...cytoskeletal rearrangements and growth of the associated adhesion complex, resulting in increased cellular stiffness, also known as reinforcement. Although RhoA has been shown to play a role during reinforcement, the molecular mechanisms that regulate its activity are unknown. By combining biochemical and biophysical approaches, we identified two guanine nucleotide exchange factors (GEFs), LARG and GEF-H1, as key molecules that regulate the cellular adaptation to force. We show that stimulation of integrins with tensional force triggers activation of these two GEFs and their recruitment to adhesion complexes. Surprisingly, activation of LARG and GEF-H1 involves distinct signalling pathways. Our results reveal that LARG is activated by the Src family tyrosine kinase Fyn, whereas GEF-H1 catalytic activity is enhanced by ERK downstream of a signalling cascade that includes FAK and Ras.
Scholars have identified reflexivity, the ability to question what one might be taking for granted, as a critical meta-cognitive skill that management schools should cultivate amongst students. ...Reflexive learning though is a complex and idiosyncratic process. Little is known about how students experience this process, what they learn, or how a range of students representing different degrees of potential for reflexivity experience such a process differently. This article reports on a study using Kegan’s Constructive Developmental Theory to assess how masters students at a professional school studying leadership and representing different developmental stages experience the same teaching methods for cultivating reflexivity. This work illuminates how students at different stages of development experience the same teaching method for cultivating reflexivity quite differently. Results indicate that for students with limited potential for reflexivity, there is profound developmental growth. Other students who began the course with existing reflexive capacity did not initially demonstrate skills of reflexivity. However, this group of students learned to practice reflexivity without actually interrogating their own assumptions in a way that represents developmental growth. I share details of the study and conclude with implications for teaching reflexivity across a diverse range of experience.
Chronic kidney disease (CKD) affects over 10% of the global population and poses significant challenges for societies and health care systems worldwide. To illustrate these challenges and inform ...cost-effectiveness analyses, we undertook a comprehensive systematic scoping review that explored costs, health-related quality of life (HRQoL) and life expectancy (LE) amongst individuals with CKD. Costs were examined from a health system and societal perspective, and HRQoL was assessed from a societal and patient perspective. Papers published in English from 2015 onward found through a systematic search strategy formed the basis of the review. All costs were adjusted for inflation and expressed in US$ after correcting for purchasing power parity. From the health system perspective, progression from CKD stages 1-2 to CKD stages 3a-3b was associated with a 1.1-1.7 fold increase in per patient mean annual health care cost. The progression from CKD stage 3 to CKD stages 4-5 was associated with a 1.3-4.2 fold increase in costs, with the highest costs associated with end-stage renal disease at $20,110 to $100,593 per patient. Mean EuroQol-5D index scores ranged from 0.80 to 0.86 for CKD stages 1-3, and decreased to 0.73-0.79 for CKD stages 4-5. For treatment with renal replacement therapy, transplant recipients incurred lower costs and demonstrated higher HRQoL scores with longer LE compared to dialysis patients. The study has provided a comprehensive updated overview of the burden associated with different CKD stages and renal replacement therapy modalities across developed countries. These data will be useful for the assessment of new renal services/therapies in terms of cost-effectiveness.
Vinculin (Vcn) is a ubiquitously expressed cytoskeletal protein that links transmembrane receptors to actin filaments, and plays a key role in regulating cell adhesion, motility, and force ...transmission. Metavinculin (MVcn) is a Vcn splice isoform that contains an additional exon encoding a 68-residue insert within the actin binding tail domain. MVcn is selectively expressed at sub-stoichiometic amounts relative to Vcn in smooth and cardiac muscle cells. Mutations in the MVcn insert are linked to various cardiomyopathies. In vitro analysis has previously shown that while both proteins can engage filamentous (F)-actin, only Vcn can promote F-actin bundling. Moreover, we and others have shown that MVcn can negatively regulate Vcn-mediated F-actin bundling in vitro. To investigate functional differences between MVcn and Vcn, we stably expressed either Vcn or MVcn in Vcn-null mouse embryonic fibroblasts. While both MVcn and Vcn were observed at FAs, MVcn-expressing cells had larger but fewer focal adhesions per cell compared to Vcn-expressing cells. MVcn-expressing cells migrated faster and exhibited greater persistence compared to Vcn-expressing cells, even though Vcn-containing FAs assembled and disassembled faster. Magnetic tweezer measurements on Vcn-expressing cells show a typical cell stiffening phenotype in response to externally applied force; however, this was absent in Vcn-null and MVcn-expressing cells. Our findings that MVcn expression leads to larger but fewer FAs per cell, in conjunction with the inability of MVcn to bundle F-actin in vitro and rescue the cell stiffening response, are consistent with our previous findings of actin bundling deficient Vcn variants, suggesting that deficient actin-bundling may account for some of the differences between Vcn and MVcn.
The Rifle alluvial aquifer along the Colorado River in west central Colorado contains fine-grained, diffusion-limited sediment lenses that are substantially enriched in organic carbon and sulfides, ...as well as uranium, from previous milling operations. These naturally reduced zones (NRZs) coincide spatially with a persistent uranium groundwater plume. There is concern that uranium release from NRZs is contributing to plume persistence or will do so in the future. To better define the physical extent, heterogeneity and biogeochemistry of these NRZs, we investigated sediment cores from five neighboring wells. The main NRZ body exhibited uranium concentrations up to 100 mg/kg U as U(IV) and contains ca. 286 g of U in total. Uranium accumulated only in areas where organic carbon and reduced sulfur (as iron sulfides) were present, emphasizing the importance of sulfate-reducing conditions to uranium retention and the essential role of organic matter. NRZs further exhibited centimeter-scale variations in both redox status and particle size. Mackinawite, greigite, pyrite and sulfate coexist in the sediments, indicating that dynamic redox cycling occurs within NRZs and that their internal portions can be seasonally oxidized. We show that oxidative U(VI) release to the aquifer has the potential to sustain a groundwater contaminant plume for centuries. NRZs, known to exist in other uranium-contaminated aquifers, may be regionally important to uranium persistence.
The ability to measure dynamic structural changes within a cell under applied load is essential for developing more accurate models of cell mechanics and mechanotransduction. Atomic force microscopy ...is a powerful tool for evaluating cell mechanics, but the dominant applied forces and sample strains are in the vertical direction, perpendicular to the imaging plane of standard fluorescence imaging. Here we report on a combined sideways imaging and vertical light sheet illumination system integrated with AFM. Our system enables high frame rate, low background imaging of subcellular structural dynamics in the vertical plane synchronized with AFM force data. Using our system for cell compression measurements, we correlated stiffening features in the force indentation data with onset of nuclear deformation revealed in the imaging data. In adhesion studies we were able to correlate detailed features in the force data during adhesive release events with strain at the membrane and within the nucleus.
Use of nonlinear statistical methods and models are ubiquitous in scientific research. However, these methods may not be fully understood, and as demonstrated here, commonly-reported parameter ...p-values and confidence intervals may be inaccurate. The gentle introduction to nonlinear regression modelling and comprehensive illustrations given here provides applied researchers with the needed overview and tools to appreciate the nuances and breadth of these important methods. Since these methods build upon topics covered in first and second courses in applied statistics and predictive modelling, the target audience includes practitioners and students alike. To guide practitioners, we summarize, illustrate, develop, and extend nonlinear modelling methods, and underscore caveats of Wald statistics using basic illustrations and give key reasons for preferring likelihood methods. Parameter profiling in multiparameter models and exact or near-exact versus approximate likelihood methods are discussed and curvature measures are connected with the failure of the Wald approximations regularly used in statistical software. The discussion in the main paper has been kept at an introductory level and it can be covered on a first reading; additional details given in the Appendices can be worked through upon further study. The associated online Supplementary Information also provides the data and R computer code which can be easily adapted to aid researchers to fit nonlinear models to their data.
Using General Social Survey data, we examine perspectives on science and religion in the United States. Latent class analysis reveals three groups based on knowledge and attitudes about science, ...religiosity, and preferences for certain religious interpretations of the world. The traditional Perspective (43 percent) is marked by a preference for religion compared to science; the modern perspective (36 percent) holds the opposite view. A third perspective, which we call post-secular (21 percent), views both science and religion favorably. However, when faced with competing accounts of events such as creation and evolution, post-seculars root their views in religion rather than in mainstream science. Regression models indicate that perspectives on science and religion do not simply mirror other denominational or ideological differences. Furthermore, religio-scientific perspectives shape attitudes about political issues where scientific and some religious communities diverge, including on abortion rights and stem cell research. Overall, most individuals favor either scientific or religious ways of understanding, but many scientifically inclined individuals prefer certain religious accounts. This suggests that public divisions related to science and religion are cultural and epistemological. This article underscores the complexity of the boundary between reason and faith and highlights the roots of political conflict in perspectives on science and religion in the United States.
Since the 1995 publication of The American Library's Robert Frost: Collected Poems, Prose, and Plays and its restoration of Frost's intended punctuation, the dust has all but settled from the ...controversy over William Connery Lathem's aggressive emendations to Frost's punctuation, including the addition of hundreds of commas. At risk of stirring up a little more of that dust, I would like to revisit one of the two most attention-grabbing instances of Lathem's meddling. Lathem's addition of an Oxford comma after "dark" in "Stopping by Woods on a Snowy Evening" is perhaps the more notable: "The woods are lovely, dark, and deep." As explained by a number of commentators, that imposition deprives the line of its enriching complication of "lovely," as something "dark and deep." That case is closed.
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