Repellent and Attractant Guidance Cues Initiate Cell Migration by Distinct Rear-Driven and Front-Driven Cytoskeletal Mechanisms.

Attractive and repulsive cell guidance is essential for animal life and important in disease. Cell migration toward attractants dominates studies [1-8], but migration away from repellents is important in biology yet relatively little studied [5, 9, 10]. It is widely held that cells initiate migration by protrusion of their front [11-15], yet this has not been explicitly tested for cell guidance because cell margin displacement at opposite ends of the cell has not been distinguished for any cue. We argue that protrusion of the front, retraction of the rear, or both together could in principle break cell symmetry and start migration in response to guidance cues [16]. Here, we find in the Dictyostelium model [6] that an attractant-cAMP-breaks symmetry by causing protrusion of the front of the cell, whereas its repellent analog-8CPT-breaks symmetry by causing retraction of the rear. Protrusion of the front of these cells in response to cAMP starts with local actin filament assembly, while the delayed retraction of the rear is independent of both myosin II polarization and of motor-based contractility. On the contrary, myosin II accumulates locally in the rear of the cell in response to 8CPT, anticipating retraction and required for it, while local actin assembly is delayed and couples to delayed protrusion at the front. These data reveal an important new concept in the understanding of cell guidance

Tuning the endothelial response: differential release of exocytic cargos from Weibel-Palade bodies.

Essentials Endothelial activation initiates multiple processes, including hemostasis and inflammation. The molecules that contribute to these processes are co-stored in secretory granules. How can the cells control release of granule content to allow differentiated responses? Selected agonists recruit an exocytosis-linked actin ring to boost release of a subset of cargo. SUMMARY: Background Endothelial cells harbor specialized storage organelles, Weibel-Palade bodies (WPBs). Exocytosis of WPB content into the vascular lumen initiates primary hemostasis, mediated by von Willebrand factor (VWF), and inflammation, mediated by several proteins including P-selectin. During full fusion, secretion of this large hemostatic protein and smaller pro-inflammatory proteins are thought to be inextricably linked. Objective To determine if secretagogue-dependent differential release of WPB cargo occurs, and whether this is mediated by the formation of an actomyosin ring during exocytosis. Methods We used VWF string analysis, leukocyte rolling assays, ELISA, spinning disk confocal microscopy, high-throughput confocal microscopy and inhibitor and siRNA treatments to demonstrate the existence of cellular machinery that allows differential release of WPB cargo proteins. Results Inhibition of the actomyosin ring differentially effects two processes regulated by WPB exocytosis; it perturbs VWF string formation but has no effect on leukocyte rolling. The efficiency of ring recruitment correlates with VWF release; the ratio of release of VWF to small cargoes decreases when ring recruitment is inhibited. The recruitment of the actin ring is time dependent (fusion events occurring directly after stimulation are less likely to initiate hemostasis than later events) and is activated by protein kinase C (PKC) isoforms. Conclusions Secretagogues differentially recruit the actomyosin ring, thus demonstrating one mechanism by which the prothrombotic effect of endothelial activation can be modulated. This potentially limits thrombosis whilst permitting a normal inflammatory response. These results have implications for the assessment of WPB fusion, cargo-content release and the treatment of patients with von Willebrand disease.British Heart Foundation. Grant Number: PG/15/72/31732. Medical Research Council. Grant Numbers: MC_UU_12018/2, MR/M019179/1

The Role of Actin Turnover in Retrograde Actin Network Flow in Neuronal Growth Cones

The balance of actin filament polymerization and depolymerization maintains a steady state network treadmill in neuronal growth cones essential for motility and guidance. Here we have investigated the connection between depolymerization and treadmilling dynamics. We show that polymerization-competent barbed ends are concentrated at the leading edge and depolymerization is distributed throughout the peripheral domain. We found a high-to-low G-actin gradient between peripheral and central domains. Inhibiting turnover with jasplakinolide collapsed this gradient and lowered leading edge barbed end density. Ultrastructural analysis showed dramatic reduction of leading edge actin filament density and filament accumulation in central regions. Live cell imaging revealed that the leading edge retracted even as retrograde actin flow rate decreased exponentially. Inhibition of myosin II activity before jasplakinolide treatment lowered baseline retrograde flow rates and prevented leading edge retraction. Myosin II activity preferentially affected filopodial bundle disassembly distinct from the global effects of jasplakinolide on network turnover. We propose that growth cone retraction following turnover inhibition resulted from the persistence of myosin II contractility even as leading edge assembly rates decreased. The buildup of actin filaments in central regions combined with monomer depletion and reduced polymerization from barbed ends suggests a mechanism for the observed exponential decay in actin retrograde flow. Our results show that growth cone motility is critically dependent on continuous disassembly of the peripheral actin network

Discovery of biomarkers for the presence and progression of left ventricular diastolic dysfunction and HEart faiLure with Preserved ejection Fraction in patients at risk for cardiovascular disease: Rationale and design of the HELPFul case-cohort study in a Dutch cardiology outpatient clinic

Introduction Left ventricular diastolic dysfunction (LVDD) is a common condition in both sexes that may deteriorate into heart failure (HF) with preserved ejection fraction (pEF), although this seems to happen more often in women than in men. Both LVDD and HFpEF often go unrecognised, necessitating the discovery of biomarkers that aid both the identification of individuals with LVDD at risk of developing HF and identification of individuals most likely to benefit from treatment. Methods and analysis HELPFul is an ongoing case-cohort study at a Dutch cardiology outpatient clinic enrolling patients aged 45 years and older without history of cardiovascular disease, who were referred by the general practitioner for cardiac evaluation. We included a random sample of patients and enriched the cohort with cases (defined as an E/e’ ≥8 measured with echocardiography). Information about medical history, cardiovascular risk factors, electrocardiography, echocardiography, exercise test performance, common carotid intima-media thickness measurement and standard cardiovascular biomarkers was obtained from the routine care data collected by the cardiology outpatient clinic. Study procedure consists of extensive venous blood collection for biobanking and additional standardised questionnaires. Follow-up will consist of standardised questionnaires by mail and linkage to regional and national registries. We will perform cardiac magnetic resonance imaging and coronary CT angiography in a subgroup of patients to investigate the extent of macrovascular and microvascular coronary disease. Ethics and dissemination The study protocol was approved by the Institutional Review Board of the University Medical Center Utrecht. Results will be disseminated through national and international conferences and in peer-reviewed journals in cardiovascular disease

Shot noise in mesoscopic systems

This is a review of shot noise, the time-dependent fluctuations in the electrical current due to the discreteness of the electron charge, in small conductors. The shot-noise power can be smaller than that of a Poisson process as a result of correlations in the electron transmission imposed by the Pauli principle. This suppression takes on simple universal values in a symmetric double-barrier junction (suppression factor 1/2), a disordered metal (factor 1/3), and a chaotic cavity (factor 1/4). Loss of phase coherence has no effect on this shot-noise suppression, while thermalization of the electrons due to electron-electron scattering increases the shot noise slightly. Sub-Poissonian shot noise has been observed experimentally. So far unobserved phenomena involve the interplay of shot noise with the Aharonov-Bohm effect, Andreev reflection, and the fractional quantum Hall effect.Comment: 37 pages, Latex, 10 figures (eps). To be published in "Mesoscopic Electron Transport," edited by L. P. Kouwenhoven, G. Schoen, and L. L. Sohn, NATO ASI Series E (Kluwer Academic Publishing, Dordrecht

Supporting adherence for people starting a new medication for a long-term condition through community pharmacies: a pragmatic randomised controlled trial of the New Medicine Service

Objective: To examine the effectiveness of the New Medicine Service (NMS), a national community pharmacy service to support medicines-taking in people starting a new medicine for a long-term condition, compared with normal practice. Methods: Pragmatic patient-level parallel randomised controlled trial, in 46 community pharmacies in England. Patients 1:1 block randomisation stratified by drug/disease group within each pharmacy. 504 participants (NMS: 251) aged 14 years and over, identified in the pharmacy on presentation of a prescription for asthma/chronic obstructive pulmonary disease, hypertension, type 2 diabetes or an anticoagulant/antiplatelet agent. NMS intervention: One consultation 7–14 days after presentation of prescription followed by another 14–21 days thereafter to identify problems with treatment and provide support if needed. Controls received normal practice. Adherence, defined as missing no doses without the advice of a medical professional in the previous 7 days, was assessed through patient self-report at 10 weeks. Intention-to-treat analysis was employed, with outcome adjusted for recruiting pharmacy, NMS disease category, age, sex and medication count. Cost to the National Health Service (NHS) was collected. Results: At 10 weeks, 53 patients had withdrawn and 443 (85%) patients were contacted successfully by telephone. In the unadjusted analysis of 378 patients still taking the initial medicine, 61% (95% CI 54% to 67%) and 71% (95% CI 64% to 77%) patients were adherent in the normal practice and NMS arms, respectively (p=0.04 for difference). In the adjusted intention-to-treat analysis, the OR for increased adherence was 1.67 (95% CI 1.06 to 2.62; p=0.027) in favour of the NMS arm. There was a general trend to reduced NHS costs, albeit, statistically non-significant, for the NMS intervention: saving £21 (95% CI −£59 to £100, p=0.128) per patient. Conclusions: The NMS significantly increased the proportion of patients adhering to their new medicine by about 10%, compared with normal practice

The Netherlands Arrhythmogenic Cardiomyopathy Registry: design and status update

Background Clinical research on arrhythmogenic cardiomyopathy (ACM) is typically limited by small patient numbers, retrospective study designs, and inconsistent definitions. Aim To create a large national ACM patient cohort with a vast amount of uniformly collected high-quality data that is readily available for future research. Methods This is a multicentre, longitudinal, observational cohort study that includes (1) patients with a definite ACM diagnosis, (2) at-risk relatives of ACM patients, and (3) ACM-associated mutation carriers. At baseline and every follow-up visit, a medical history as well information regarding (non-)invasive tests is collected (e. g. electrocardiograms, Holter recordings, imaging and electrophysiological studies, pathology reports, etc.). Outcome data include (non-)sustained ventricular and atrial arrhythmias, heart failure, and (cardiac) death. Data are collected on a research electronic data capture (REDCap) platform in which every participating centre has its own restricted data access group, thus empowering local studies while facilitating data sharing. Discussion The Netherlands ACM Registry is a national observational cohort study of ACM patients and relatives. Prospective and retrospective data are obtained at multiple time points, enabling both cross-sectional and longitudinal research in a hypothesis-generating approach that extends beyond one specific research question. In so doing, this registry aims to (1) increase the scientific knowledge base on disease mechanisms, genetics, and novel diagnostic and treatment strategies of ACM; and (2) provide education for physicians and patients concerning ACM, e. g. through our website (www.acmregistry.nl) and patient conferences

Hypoxic regulation of RIOK3 is a major mechanism for cancer cell invasion and metastasis.

Hypoxia is a common feature of locally advanced breast cancers that is associated with increased metastasis and poorer survival. Stabilisation of hypoxia-inducible factor-1α (HIF1α) in tumours causes transcriptional changes in numerous genes that function at distinct stages of the metastatic cascade. We demonstrate that expression of RIOK3 (RIght Open reading frame kinase 3) was increased during hypoxic exposure in an HIF1α-dependent manner. RIOK3 was localised to distinct cytoplasmic aggregates in normoxic cells and underwent redistribution to the leading edge of the cell in hypoxia with a corresponding change in the organisation of the actin cytoskeleton. Depletion of RIOK3 expression caused MDA-MB-231 to become elongated and this morphological change was due to a loss of protraction at the trailing edge of the cell. This phenotypic change resulted in reduced cell migration in two-dimensional cultures and inhibition of cell invasion through three-dimensional extracellular matrix. Proteomic analysis identified interactions of RIOK3 with actin and several actin-binding factors including tropomyosins (TPM3 and TPM4) and tropomodulin 3. Depletion of RIOK3 in cells resulted in fewer and less organised actin filaments. Analysis of these filaments showed reduced association of TPM3, particularly during hypoxia, suggesting that RIOK3 regulates actin filament specialisation. RIOK3 depletion reduced the dissemination of MDA-MB-231 cells in both a zebrafish model of systemic metastasis and a mouse model of pulmonary metastasis. These findings demonstrate that RIOK3 is necessary for maintaining actin cytoskeletal organisation required for migration and invasion, biological processes that are necessary for hypoxia-driven metastasis

Unwanted effects: Is there a negative side of meditation? A multicentre survey

Objectives Despite the long-term use and evidence-based efficacy of meditation and mindfulness-based interventions, there is still a lack of data about the possible unwanted effects (UEs) of these practices. The aim of this study was to evaluate the occurrence of UEs among meditation practitioners, considering moderating factors such as the type, frequency, and lifetime duration of the meditation practices. Methods An online survey was developed and disseminated through several websites, such as Spanish-, English- and Portuguese-language scientific research portals related to mindfulness and meditation. After excluding people who did not answer the survey correctly or completely and those who had less than two months of meditation experience, a total of 342 people participated in the study. However, only 87 reported information about UEs. Results The majority of the practitioners were women from Spain who were married and had a University education level. Practices were more frequently informal, performed on a daily basis, and followed by focused attention (FA). Among the participants, 25.4% reported UEs, showing that severity varies considerably. The information requested indicated that most of the UEs were transitory and did not lead to discontinuing meditation practice or the need for medical assistance. They were more frequently reported in relation to individual practice, during focused attention meditation, and when practising for more than 20 minutes and alone. The practice of body awareness was associated with UEs to a lesser extent, whereas focused attention was associated more with UEs. Conclusions This is the first large-scale, multi-cultural study on the UEs of meditation. Despite its limitations, this study suggests that UEs are prevalent and transitory and should be further studied. We recommend the use of standardized questionnaires to assess the UEs of meditation practices