Myosin light chain kinase-driven myosin II turnover regulates actin cortex contractility during mitosis.

Force generation by the molecular motor myosin II (MII) at the actin cortex is a universal feature of animal cells. Despite its central role in driving cell shape changes, the mechanisms underlying MII regulation at the actin cortex remain incompletely understood. Here we show that myosin light chain kinase (MLCK) promotes MII turnover at the mitotic cortex. Inhibition of MLCK resulted in an alteration of the relative levels of phosphorylated regulatory light chain (RLC), with MLCK preferentially creating a short-lived pRLC species and Rho-associated kinase (ROCK) preferentially creating a stable ppRLC species during metaphase. Slower turnover of MII and altered RLC homeostasis on MLCK inhibition correlated with increased cortex tension, driving increased membrane bleb initiation and growth, but reduced bleb retraction during mitosis. Taken together, we show that ROCK and MLCK play distinct roles at the actin cortex during mitosis; ROCK activity is required for recruitment of MII to the cortex, while MLCK activity promotes MII turnover. Our findings support the growing evidence that MII turnover is an essential dynamic process influencing the mechanical output of the actin cortex.

Precise Tuning of Cortical Contractility Regulates Cell Shape during Cytokinesis.

The mechanical properties of the actin cortex regulate shape changes during cell division, cell migration, and tissue morphogenesis. We show that modulation of myosin II (MII) filament composition allows tuning of surface tension at the cortex to maintain cell shape during cytokinesis. Our results reveal that MIIA generates cortex tension, while MIIB acts as a stabilizing motor and its inclusion in MII hetero-filaments reduces cortex tension. Tension generation by MIIA drives faster cleavage furrow ingression and bleb formation. We also show distinct roles for the motor and tail domains of MIIB in maintaining cytokinetic fidelity. Maintenance of cortical stability by the motor domain of MIIB safeguards against shape instability-induced chromosome missegregation, while its tail domain mediates cortical localization at the terminal stages of cytokinesis to mediate cell abscission. Because most non-muscle contractile systems are cortical, this tuning mechanism will likely be applicable to numerous processes driven by myosin-II contractility.

A simple and flexible high-throughput method for the study of cardiomyocyte proliferation.

Cardiac muscle cells lack regenerative capacity in postnatal mammals. A concerted effort has been made in the field to determine regulators of cardiomyocyte proliferation and identify therapeutic strategies to induce division, with the ultimate goal of regenerating heart tissue after a myocardial infarct. We sought to optimize a high throughput screening protocol to facilitate this effort. We developed a straight-forward high throughput screen with simple readouts to identify small molecules that modulate cardiomyocyte proliferation. We identify human induced pluripotent stem cell-derived cardiomyocytes (hiCMs) as a model system for such a screen, as a very small subset of hiCMs have the potential to proliferate. The ability of hiCMs to proliferate is density-dependent, and cell density has no effect on the outcome of proliferation: cytokinesis or binucleation. Screening a compound library revealed many regulators of proliferation and cell death. We provide a comprehensive and flexible screening procedure and cellular phenotype information for each compound. We then provide an example of steps to follow after this screen is performed, using three of the identified small molecules at various concentrations, further implicating their target kinases in cardiomyocyte proliferation. This screening platform is flexible and cost-effective, opening the field of cardiovascular cell biology to laboratories without substantial funding or specialized training, thus diversifying this scientific community.

Effective Strategies to Spread Redesigning Care Processes Among Healthcare Teams.

PURPOSE: The purpose of this study was to describe how spread strategies facilitate the successful implementation of the Transforming Care at the Bedside (TCAB) program and their impact on healthcare workers and patients in a major Canadian healthcare organization. DESIGN: This study used a qualitative and descriptive design with focus groups and individual interviews held in May 2014. Participants included managers and healthcare providers from eight TCAB units in a university health center in Quebec, Canada. The sample was composed of 43 individuals. METHODS: The data were analyzed using NVivo according to the method proposed by Miles and Huberman. FINDINGS: The first two themes that emerged from the analysis are related to context (organizational transition requiring many changes) and spread strategies for the TCAB program (senior management support, release time and facilitation, rotation of team members, learning from previous TCAB teams, and engaging patients). The last theme that emerged from the analysis is the impact on healthcare professionals (providing front-line staff and managers with the training they need to make changes, team leadership, and increasing receptivity to hearing patients' and families' needs and requests). CONCLUSIONS: This study describes the perspectives of managers and team members to provide a better understanding of how spread strategies can facilitate the successful implementation of the TCAB program in a Canadian healthcare organization. CLINICAL RELEVANCE: Spread strategies facilitate the implementation of changes to improve the quality and safety of care provided to patients.

Transforming Care at the Bedside: managers' and health care providers' perceptions of their change capacities.

BACKGROUND: The Transforming Care at the Bedside (TCAB) project engages frontline health care providers as the leaders of change and improvement efforts in their work environment. This study explored how health care providers and managers from three TCAB units in a university-affiliated health care center perceived the development of their change capacities following their involvement in this program. METHOD: This descriptive, qualitative study involved focus groups and individual interviews. RESULTS: Participants learned to work as a team and to expand their outlook. They had access to processes and tools to learn new skills. New relationships also developed among the various players, and they shared new roles, which enabled them to translate the desired changes into action and make the results visible. CONCLUSION: The study showed the TCAB program helps develop health care providers' and managers' change capacities.

The effect of transforming care at the bedside initiative on healthcare teams' work environments.

BACKGROUND: Different initiatives have been implemented in healthcare organizations to improve efficiency, such as transforming care at the bedside (TCAB). However, there are important gaps in understanding the effect of TCAB on healthcare teams' work environments. AIM: The specific aim of the study is to describe findings regarding the TCAB initiative effects on healthcare teams' work environments. METHODS: A pretest and posttest study design was used for this study. The TCAB initiative was implemented in fall 2010 in a university health center in Montreal, Canada. The sample consisted of healthcare workers from four different care units. RESULTS: Statistically significant improvement was observed with the communicating specific information subscale from the measure of processes of care variable, and a significant difference was found between the support from colleagues variable, which was higher at baseline than postprogram. The differences for psychological demand, decisional latitude, and effort-reward were not significant. CONCLUSIONS: TCAB is an intervention that allows healthcare teams to implement change to improve patients' and families' outcomes. Ongoing energy should focus on how to improve communication among all members of the team and ensure their support.

A qualitative interpretive study exploring parents' perception of the parental role in the paediatric intensive care unit.

OBJECTIVES: The purpose of this study was to explore parents' perception of the parental role in a tertiary care Canadian university affiliated hospital's paediatric intensive care unit (PICU). RESEARCH METHODOLOGY: A descriptive interpretive design was used with a purposive heterogeneous sample to reflect the range of children and parents normally admitted to the PICU. Semi-structured interviews were conducted with seven parents. Interview data were collected and analysed using the constant comparative method. FINDINGS: Three main themes emerged: (1) being present and participating in the child's care; (2) forming a partnership of trust with the PICU health care team; and (3) being informed of the child's progress and treatment plan as the person who "knows" the child best. CONCLUSION: Enhanced understanding of the parental role in the PICU from the perspective of parents can help guide the development of strategies to more effectively support parents and promote parenting during this extremely stressful time.

Applications and extensions of Chao's moment estimator for the size of a closed population.

This article revisits Chao's (1989, Biometrics45, 427-438) lower bound estimator for the size of a closed population in a mark-recapture experiment where the capture probabilities vary between animals (model M(h)). First, an extension of the lower bound to models featuring a time effect and heterogeneity in capture probabilities (M(th)) is proposed. The biases of these lower bounds are shown to be a function of the heterogeneity parameter for several loglinear models for M(th). Small-sample bias reduction techniques for Chao's lower bound estimator are also derived. The application of the loglinear model underlying Chao's estimator when heterogeneity has been detected in the primary periods of a robust design is then investigated. A test for the null hypothesis that Chao's loglinear model provides unbiased abundance estimators is provided. The strategy of systematically using Chao's loglinear model in the primary periods of a robust design where heterogeneity has been detected is investigated in a Monte Carlo experiment. Its impact on the estimation of the population sizes and of the survival rates is evaluated in a Monte Carlo experiment.