Locomotion Guidance by Extracellular Matrix Is Adaptive and Can be Restored by a Transient Change in Ca2+ Level

Navigation of cell locomotion by gradients of soluble factors can be desensitized if the concentration of the chemo-attractant stays unchanged. It remains obscure if the guidance by immobilized extracellular matrix (ECM) as the substrate is also adaptive and if so, how can the desensitized ECM guidance be resensitized. When first interacting with a substrate containing micron-scale fibronectin (FBN) trails, highly motile fish keratocytes selectively adhere and migrate along the FBN paths. However, such guided motion become adaptive after about 10 min and the cells start to migrate out of the ECM trails. We found that a burst increase of intracellular calcium created by an uncaging technique immediately halts the undirected migration by disrupting the ECM-cytoskeleton coupling, as evidenced by the appearance of retrograde F-actin flow. When the motility later resumes, the activated integrin receptors render the cell selectively binding to the FBN path and reinitiates signaling events, including tyrosine phosphorylation of paxillin, that couple retrograde F-actin flow to the substrate. Thus, the calcium-resensitized cell can undergo a period of ECM-navigated movement, which later becomes desensitized. Our results also suggest that endogenous calcium transients as occur during spontaneous calcium oscillations may exert a cycling resensitization-desensitization control over cell's sensing of substrate guiding cues

New Strategies for Research in Clinical Practice: A focus on self–harm.

This article suggests new ways of approaching clinical-based research in an era of evidence-based practice. Using the example of self-harm, we identify three distinct problems with current dominant approaches to research in this area. These include insufficient clarity about target issues, an overreliance on predetermined outcomes which prioritise behavioural measures (such as self-harm cessation) and an undue focus on treatment techniques. We argue that clinical research requires flexible, user-centred and practice-based methods, informed by a focus on principles instead of techniques. Therefore, we outline key practice-based principles that we argue need to be embedded within clinical research strategies. We then demonstrate how traditional behavioural approaches to research can be enriched with more qualitative cognitive and emotionally based data. We conclude that such strategies provide thickened, meaningful and context-specific research which is more relevant for service commissioners, clinicians and service users

Killing activity of neutrophils is mediated through activation of proteases by K+ flux

According to the hitherto accepted view, neutrophils kill ingested microorganisms by subjecting them to high concentrations of highly toxic reactive oxygen species (ROS) and bringing about myeloperoxidase-catalysed halogenation. We show here that this simple scheme, which for many years has served as a satisfactory working hypothesis, is inadequate. We find that mice made deficient in neutrophil-granule proteases but normal in respect of superoxide production and iodinating capacity, are unable to resist staphylococcal and candidal infections. We also show that activation provokes the influx of an enormous concentration of ROS into the endocytic vacuole. The resulting accumulation of anionic charge is compensated for by a surge of K+ ions that cross the membrane in a pH-dependent manner. The consequent rise in ionic strength engenders the release of cationic granule proteins, including elastase and cathepsin G, from the anionic sulphated proteoglycan matrix. We show that it is the proteases, thus activated, that are primarily responsible for the destruction of the bacteria