Myosin-5 varies its step length to carry cargo straight along the irregular F-actin track.

Molecular motors employ chemical energy to generate unidirectional mechanical output against a track while navigating a chaotic cellular environment, potential disorder on the track, and against Brownian motion. Nevertheless, decades of nanometer-precise optical studies suggest that myosin-5a, one of the prototypical molecular motors, takes uniform steps spanning 13 subunits (36 nm) along its F-actin track. Here, we use high-resolution interferometric scattering microscopy to reveal that myosin takes strides spanning 22 to 34 actin subunits, despite walking straight along the helical actin filament. We show that cumulative angular disorder in F-actin accounts for the observed proportion of each stride length, akin to crossing a river on variably spaced stepping stones. Electron microscopy revealed the structure of the stepping molecule. Our results indicate that both motor and track are soft materials that can adapt to function in complex cellular conditions.

Structure of the shutdown state of myosin-2.

Myosin-2 is essential for processes as diverse as cell division and muscle contraction. Dephosphorylation of its regulatory light chain promotes an inactive, 'shutdown' state with the filament-forming tail folded onto the two heads1, which prevents filament formation and inactivates the motors2. The mechanism by which this happens is unclear. Here we report a cryo-electron microscopy structure of shutdown smooth muscle myosin with a resolution of 6 Å in the head region. A pseudo-atomic model, obtained by flexible fitting of crystal structures into the density and molecular dynamics simulations, describes interaction interfaces at the atomic level. The N-terminal extension of one regulatory light chain interacts with the tail, and the other with the partner head, revealing how the regulatory light chains stabilize the shutdown state in different ways and how their phosphorylation would allow myosin activation. Additional interactions between the three segments of the coiled coil, the motor domains and the light chains stabilize the shutdown molecule. The structure of the lever in each head is competent to generate force upon activation. This shutdown structure is relevant to all isoforms of myosin-2 and provides a framework for understanding their disease-causing mutations.

Functions and mechanics of dynein motor proteins.

Fuelled by ATP hydrolysis, dyneins generate force and movement on microtubules in a wealth of biological processes, including ciliary beating, cell division and intracellular transport. The large mass and complexity of dynein motors have made elucidating their mechanisms a sizable task. Yet, through a combination of approaches, including X-ray crystallography, cryo-electron microscopy, single-molecule assays and biochemical experiments, important progress has been made towards understanding how these giant motor proteins work. From these studies, a model for the mechanochemical cycle of dynein is emerging, in which nucleotide-driven flexing motions within the AAA+ ring of dynein alter the affinity of its microtubule-binding stalk and reshape its mechanical element to generate movement.

AAA+ Ring and linker swing mechanism in the dynein motor.

Dynein ATPases power diverse microtubule-based motilities. Each dynein motor domain comprises a ring-like head containing six AAA+ modules and N- and C-terminal regions, together with a stalk that binds microtubules. How these subdomains are arranged and generate force remains poorly understood. Here, using electron microscopy and image processing of tagged and truncated Dictyostelium cytoplasmic dynein constructs, we show that the heart of the motor is a hexameric ring of AAA+ modules, with the stalk emerging opposite the primary ATPase site (AAA1). The C-terminal region is not an integral part of the ring but spans between AAA6 and near the stalk base. The N-terminal region includes a lever-like linker whose N terminus swings by approximately 17 nm during the ATPase cycle between AAA2 and the stalk base. Together with evidence of stalk tilting, which may communicate changes in microtubule binding affinity, these findings suggest a model for dynein's structure and mechanism.

100 years of Emil Wolf: introduction.

The groundbreaking research and ideas introduced by Emil Wolf continue to inspire researchers and motivate ongoing research in the wave properties of light. This special issue commemorates the legacy of Emil Wolf with research in physical optics, with specific focus on those areas where Wolf was active, such as optical coherence theory, inverse problems, singular optics, imaging, and polarization, and the intersection of these fields of study. Here we discuss the life of Emil Wolf and his influence on optical science and the optics community.

Preoperative anemia management program reduces blood transfusion in elective cardiac surgical patients, improving outcomes and decreasing hospital length of stay.

BACKGROUND: Anemia is an independent risk factor for hospitalization, readmission, prolonged length of stay (LOS), diminished quality of life, and mortality. A multidisciplinary program was implemented to manage anemia preoperatively as a patient blood management (PBM) initiative. METHODS AND MATERIALS: From March 2016 to August 2018, 240 patients were screened for anemia during their preoperative cardiovascular visit. About 52/240 (22%) were found to be anemic and met out inclusion criteria. Also, 45/52 (87%) had iron deficiency anemia and 7 (13%) had anemia without iron deficiency. A similar historical cohort of patients undergoing elective cardiovascular surgery with hemoglobin (Hb) < 12 g/dl from September 2014 to February /2016 (n = 52) served as control group. The primary outcome was perioperative red blood cell (RBC) transfusion. Secondary outcomes were date-of-surgery Hb, intensive care unit (ICU) and hospital LOS, complication rates, and transfusion cost. RESULTS: The two most common treatments were IV iron ± folate (n = 36/45; 80%) and oral iron (n = 9/45; 20%). As compared to historical patients, study patients had significantly higher day-of-surgery Hb (10.6 ± 1.4 vs. 9.8 ± 1.3 g/dl, p < .001), lower utilization of RBC transfusion (0.86 ± 1.4 vs. 2.78 ± 2.4, p < .001), fewer days in the ICU (2.1 ± 2.0 vs. 4.0 ± 3.5, p = .002), and shorter total LOS (6.9 ± 4.8 vs. 12.9 ± 6.8, p < .0001). Study patients also showed lower overall complication rates (p < .0001). Analysis of RBC acquisition cost and transfusion cost also showed significant saving of 69% ($293 vs. $945 and $656 vs. $2116, respectively). CONCLUSION: When corrected for type of procedures and surgeon, our pilot anemia program in elective cardiovascular surgeries showed higher day-of-surgery Hb and significant reduction in RBC transfusion rates, ICU and hospital LOS, and overall complication rates.

Impact of COVID-19 on care-home mortality and life expectancy in Scotland.

BACKGROUND: COVID-19 deaths are commoner among care-home residents, but the mortality burden has not been quantified. METHODS: Care-home residency was identified via a national primary care registration database linked to mortality data. Life expectancy was estimated using Makeham-Gompertz models to (i) describe yearly life expectancy from November 2015 to October 2020 (ii) compare life expectancy (during 2016-18) between care-home residents and the wider population and (iii) apply care-home life expectancy estimates to COVID-19 death counts to estimate years of life lost (YLL). RESULTS: Among care-home residents, life expectancy in 2015/16 to 2019/20 ranged from 2.7 to 2.3 years for women and 2.3 to 1.8 years for men. Age-sex-specific life expectancy in 2016-18 in care-home residents was lower than in the Scottish population (10 and 2.5 years in those aged 70 and 90, respectively). Applying care home-specific life expectancies to COVID-19 deaths yield mean YLLs for care-home residents of 2.6 and 2.2 for women and men, respectively. In total YLL care-home residents have lost 3,560 years in women and 2,046 years in men. Approximately half of deaths and a quarter of YLL attributed to COVID-19 were accounted for by the 5% of over-70s who were care-home residents. CONCLUSION: COVID-19 infection has led to the loss of substantial years of life in care-home residents aged 70 years and over in Scotland. Prioritising the 5% of older adults who are care-home residents for vaccination is justified not only in terms of total deaths, but also in terms of YLL.

Role of Automated Suturing Technology in Minimally Invasive Aortic and Mitral Valve Surgery.

Minimally invasive cardiac surgery continues to evolve and expand as technology and surgeon experience develops. Among the barriers to the adoption of non-sternotomy minimally invasive valve surgery are the challenges associated with suture placement. Automated technology enables ergonomic remote suture placement that allows for reproducible results while shortening the learning curve. The objective of this review is to describe the latest advancements in automated suturing technology for minimally invasive valve surgery.

A novel model for minimally invasive left ventricular assist device implantation training.

Background: Significant advances in minimally invasive implantation of mechanical circulatory support devices have been made. These approaches are technically challenging and associated with a learning curve. Simulation and training opportunities in these techniques are limited. We developed a high-fidelity novel model for minimally invasive left ventricular assist device implantation.Material and methods: Using a modified inanimate simulator (LSI SOLUTIONS®) and an animal tissue model, a hybrid simulator was created, with a porcine ex vivo heart secured within the inanimate simulator in the normal anatomic position. Key components of the minimally invasive left ventricular assist device implantation were performed, including left ventricular apical coring, attachment of the apical ring, attachment of the assist device, and creation of the aortic-outflow graft anastomosis.Results: A novel composite inanimate and tissue model for minimally invasive left ventricular assist device implantation was successfully developed. These simulation techniques were reproducible, and the model demonstrated ability to successfully simulate key components of the procedure.Conclusions: This high-fidelity, reproducible hybrid model allows for crucial components of minimally invasive LVAD implantation to be performed. This model has the potential to be used as an adjunct to surgical training, providing a safe and controlled learning environment for trainees to acquire skills in minimally invasive LVAD implantation.

Implementation of a Standardized Transfusion Protocol for Cardiac Patients Treated With Venoarterial Extracorporeal Membrane Oxygenation Is Associated With Decreased Blood Component Utilization and May Improve Clinical Outcome.

BACKGROUND: Extracorporeal membrane oxygenation supplies oxygenated blood to the body supporting the heart and lungs. Survival rates of 20% to 50% are reported among patients receiving ECMO for cardiac arrest, severe cardiogenic shock, or failure to wean from cardiopulmonary bypass following cardiac surgery. Bleeding is one of the most common complications in ECMO patients due to coagulopathy, systemic anticoagulation, and the presence of large bore cannulas at systemic pressure. Absence of a standardized transfusion protocol in this population leads to inconsistent transfusion practices. Here, we assess a newly developed dedicated transfusion protocol in this clinical setting. METHODS: Data were retrospectively reviewed for the first 30 consecutive cardiac ECMO patients prior and post implementation of the ECMO transfusion protocol. Diagnoses, laboratory results, blood component utilization, and outcomes were collected and analyzed. RESULTS: Comorbidities were similar between the 2 eras, as well as the pre-ECMO ejection fraction (P = .568) and duration on ECMO (P = .278). Transfusion utilization data revealed statistically significant decreases in almost all blood components and a savings in blood component acquisition costs of 51% ($175, 970). In addition, an almost 2-fold increase in survival rate was observed in the post-ECMO transfusion protocol era (63% vs 33%; relative risk = 1.82; 95% confidence interval, 1.07-3.10; P = .028). CONCLUSIONS: Our data indicate that implementation of a standardized transfusion protocol, using more restrictive transfusion indications in cardiac ECMO patients, was associated with reduced blood product utilization, decreased complications, and improved survival. This multidepartmental approach facilitates better communication and adherence to consensus clinical decision making between intensive care unit, surgery, and transfusion service and optimizes care of complicated and acutely ill patients.

Weighing benefits and risks in aspects of security, privacy and adoption of technology in a value-based healthcare system.

BACKGROUND: Technology can potentially enable the implementation of a value-based healthcare system, where the impact of quality of care is offered at optimised cost for maximised patient benefit. Technology can deliver value by aiding in data collection to evaluate outcomes and measure costs on a patient and population level. Healthcare organisations, however, face several challenges and risks that result almost exclusively from the use of these technologies. DISCUSSION: Some challenges associated with healthcare technology include their unsustainability, due to lack of scale-up plans and timely evaluations. Other risks include noncompliance with data protection policies, inadequate data governance, and overestimated expectations resulting from the rapid introduction of new technologies. CONCLUSION: Organisations need to consider the risks and challenges associated with the use of technology and develop comprehensive strategies that mitigate factors leading to non-adoption and to realise benefits for achieving a value-based healthcare system.

Role of cAMP-phosphodiesterase 1C signaling in regulating growth factor receptor stability, vascular smooth muscle cell growth, migration, and neointimal hyperplasia.

RATIONALE: Neointimal hyperplasia characterized by abnormal accumulation of vascular smooth muscle cells (SMCs) is a hallmark of occlusive disorders such as atherosclerosis, postangioplasty restenosis, vein graft stenosis, and allograft vasculopathy. Cyclic nucleotides are vital in SMC proliferation and migration, which are regulated by cyclic nucleotide phosphodiesterases (PDEs). OBJECTIVE: Our goal is to understand the regulation and function of PDEs in SMC pathogenesis of vascular diseases. METHODS AND RESULTS: We performed screening for genes differentially expressed in normal contractile versus proliferating synthetic SMCs. We observed that PDE1C expression was low in contractile SMCs but drastically elevated in synthetic SMCs in vitro and in various mouse vascular injury models in vivo. In addition, PDE1C was highly induced in neointimal SMCs of human coronary arteries. More importantly, injury-induced neointimal formation was significantly attenuated by PDE1C deficiency or PDE1 inhibition in vivo. PDE1 inhibition suppressed vascular remodeling of human saphenous vein explants ex vivo. In cultured SMCs, PDE1C deficiency or PDE1 inhibition attenuated SMC proliferation and migration. Mechanistic studies revealed that PDE1C plays a critical role in regulating the stability of growth factor receptors, such as PDGF receptor ß (PDGFRß) known to be important in pathological vascular remodeling. PDE1C interacts with low-density lipoprotein receptor-related protein-1 and PDGFRß, thus regulating PDGFRß endocytosis and lysosome-dependent degradation in an low-density lipoprotein receptor-related protein-1-dependent manner. A transmembrane adenylyl cyclase cAMP-dependent protein kinase cascade modulated by PDE1C is critical in regulating PDGFRß degradation. CONCLUSIONS: These findings demonstrated that PDE1C is an important regulator of SMC proliferation, migration, and neointimal hyperplasia, in part through modulating endosome/lysosome-dependent PDGFRß protein degradation via low-density lipoprotein receptor-related protein-1.

Cannulation-Related Complications on Veno-Arterial Extracorporeal Membrane Oxygenation: Prevalence and Effect on Mortality.

Cannulation-related complications are a known source of morbidity in patients supported on veno-arterial extracorporeal membrane oxygenation (VA-ECMO). Despite its prevalence, little is known regarding the outcomes of patients who suffer such complications. This is a single institution review of cannulation-related complications and its effect on mortality in patients supported on VA-ECMO from January 2010-2015 using three cannulation strategies: axillary, femoral, and central. Complications were defined as advanced if they required major interventions (fasciotomy, amputation, site conversion). Patients were divided into two groups (complication present vs. not present) and Kaplan-Meier analysis was performed to determine any differences in their survival distributions. There were 103 patients supported on VA-ECMO: 41 (40%), 36 (35%), and 26 (25%) were cannulated via axillary, femoral, and central access, respectively. Cannulation-related complications occurred in 33 (32%) patients and this did not differ significantly between either axillary (34%), femoral (36%), or central (23%) strategies (P = 0.52). The most common complications encountered were hemorrhage and limb ischemia in 19 (18%) and 11 (11%) patients. Hemorrhagic complications did not differ between groups (P = 0.37), while limb ischemia and hyperperfusion were significantly associated with femoral and axillary cannulation, at a rate of 25% (P < 0.01) and 15% (P = 0.01), respectively. There was no difference in the incidence of advanced complications between cannulation groups: axillary (12%) vs. femoral (14%) vs. central (8%; P = 0.75). In addition, no increase in mortality was noted in patients who developed a cannulation-related complication by Kaplan-Meier estimates (P = 0.37). Cannulation-related complications affect a significant proportion of patients supported on VA-ECMO but do not differ in incidence between different cannulation strategies and do not affect patient mortality. Improved efforts at preventing these complications need to be developed to avoid the additional morbidity in an already critical patient population.

The Inner Centromere Protein (INCENP) Coil Is a Single α-Helix (SAH) Domain That Binds Directly to Microtubules and Is Important for Chromosome Passenger Complex (CPC) Localization and Function in Mitosis.

The chromosome passenger complex (CPC) is a master regulator of mitosis. Inner centromere protein (INCENP) acts as a scaffold regulating CPC localization and activity. During early mitosis, the N-terminal region of INCENP forms a three-helix bundle with Survivin and Borealin, directing the CPC to the inner centromere where it plays essential roles in chromosome alignment and the spindle assembly checkpoint. The C-terminal IN box region of INCENP is responsible for binding and activating Aurora B kinase. The central region of INCENP has been proposed to comprise a coiled coil domain acting as a spacer between the N- and C-terminal domains that is involved in microtubule binding and regulation of the spindle checkpoint. Here we show that the central region (213 residues) of chicken INCENP is not a coiled coil but a ∼ 32-nm-long single α-helix (SAH) domain. The N-terminal half of this domain directly binds to microtubules in vitro. By analogy with previous studies of myosin 10, our data suggest that the INCENP SAH might stretch up to ∼ 80 nm under physiological forces. Thus, the INCENP SAH could act as a flexible "dog leash," allowing Aurora B to phosphorylate dynamic substrates localized in the outer kinetochore while at the same time being stably anchored to the heterochromatin of the inner centromere. Furthermore, by achieving this flexibility via an SAH domain, the CPC avoids a need for dimerization (required for coiled coil formation), which would greatly complicate regulation of the proximity-induced trans-phosphorylation that is critical for Aurora B activation.

Cavity-Free Scheme for Nondestructive Detection of a Single Optical Photon.

Detecting a single photon without absorbing it is a long-standing challenge in quantum optics. All experiments demonstrating the nondestructive detection of a photon make use of a high quality cavity. We present a cavity-free scheme for nondestructive single-photon detection. By pumping a nonlinear medium we implement an interfield Rabi oscillation which leads to a ∼π phase shift on a weak probe coherent laser field in the presence of a single signal photon without destroying the signal photon. Our cavity-free scheme operates with a fast intrinsic time scale in comparison with similar cavity-based schemes. We implement a full real-space multimode numerical analysis of the interacting photonic modes and confirm the validity of our nondestructive scheme in the multimode case.

An evaluation of the psychometric properties of the Indicator of Relative Need (IoRN) instrument.

BACKGROUND: The Indicator of Relative Need (IoRN) instrument is designed for both health and social care services to measure function and dependency in older people. To date, the tool has not undergone assessment of validity. We report two studies aimed to evaluate psychometric properties of the IoRN. METHODS: The first study recruited patients receiving social care at discharge from hospital, those rehabilitating in intermediate care, and those in a rehabilitation at home service. Participants were assessed using the IoRN by a single researcher and by the clinical team at baseline and 8 weeks. Comparator instruments (Barthel ADL, Nottingham Extended ADL and Townsend Disability Scale) were also administered. Overall change in ability was assessed with a 7 point Likert scale at 8 weeks. The second study analysed linked routinely collected, health and social care data (including IoRN scores) to assess the relationship between IoRN category and death, hospitalisation and care home admission as a test of external validity. RESULTS: Ninety participants were included in the first study, mean age 77.9 (SD 12.0). Cronbach's alpha for IoRN subscales was high (0.87 to 0.93); subscales showed moderate correlation with comparator tools (r = 0.43 to 0.63). Cohen's weighted kappa showed moderate agreement between researcher and clinician IoRN category (0.49 to 0.53). Two-way intraclass correlation coefficients for IoRN subscales in participants reporting no change in ability were high (0.88 to 0.98) suggesting good stability; responsiveness coefficients in participants reporting overall change were equal to or better than comparator tools. 1712 patients were included in the second study, mean age 81.0 years (SD 7.7). Adjusted hazard ratios for death, care home admission and hospitalisation in the most dependent category compared to the least dependent IoRN category were 5.9 (95 % CI 2.0-17.0); 7.2 (95 % CI 4.4-12.0); 1.1 (95 % CI 0.5-2.6) respectively. The mean number of allocated hours of care 6 months after assessment was higher in the most dependent group compared to the least dependent group (5.6 vs 1.4 h, p = 0.005). CONCLUSIONS: Findings from these analyses support the use of the IoRN across a range of clinical environments although some limitations are highlighted.

Percutaneous Decompression of the Left Ventricle in Cardiogenic Shock Patients on Venoarterial Extracorporeal Membrane Oxygenation.

OBJECTIVE: Extracorporeal membrane oxygenation is an important therapeutic option for patients with refractory cardiogenic shock. Adequate decompression of the left ventricular in these patients is a key predictor of successful recovery. The currently available percutaneous decompression techniques are limited by their partial unloading capability. METHOD: We describe a series of four consecutive patients with refractory cardiogenic shock in whom adequate left ventricular decompression was achieved by integrating a transseptally placed left ventricular cannula into the existing extracorporeal membrane oxygenation circuit. RESULTS: From May to June 2015, four consecutive patients underwent transvenous transseptal left ventricular decompression with a 22 French cannula that was integrated into the extracorporeal membrane oxygenation circuit in a Y fashion. The mean age was 47.5 ± 20 years. All patients had refractory shock, and three patients failed prior decompression with an intra-aortic balloon pump. Fluoroscopy time was 12.15 ± 2.6 minutes. No procedural complications were noted. All patients had significant reduction in their pulmonary capillary wedge pressure and resolution of their pulmonary edema. Two patients died during the hospitalization due to sepsis and/or multiorgan failure. CONCLUSION: Antegrade transseptal left ventricular decompression is feasible in patients on extracorporeal membrane oxygenation and persistent pulmonary edema.

Improving Outcomes through Transformational Health and Social Care Integration - The Scottish Experience.

The Scottish Parliament recently passed legislation on integrating healthcare and social care to improve the quality and outcomes of care and support for people with multiple and complex needs across Scotland. This ambitious legislation provides a national framework to accelerate progress in person-centred and integrated care and support for the growing number of people who have multiple physical and mental health conditions and complex needs. Additional investment and improvement capacity is helping to commission support and services that are designed and delivered with people in local communities and in partnership with housing, community, voluntary and independent sectors.

Stable single α-helices are constant force springs in proteins.

Single α-helix (SAH) domains are rich in charged residues (Arg, Lys, and Glu) and stable in solution over a wide range of pH and salt concentrations. They are found in many different proteins where they bridge two functional domains. To test the idea that their high stability might enable these proteins to resist unfolding along their length, the properties and unfolding behavior of the predicted SAH domain from myosin-10 were characterized. The expressed and purified SAH domain was highly helical, melted non-cooperatively, and was monomeric as shown by circular dichroism and mass spectrometry as expected for a SAH domain. Single molecule force spectroscopy experiments showed that the SAH domain unfolded at very low forces (<30 pN) without a characteristic unfolding peak. Molecular dynamics simulations showed that the SAH domain unfolds progressively as the length is increased and refolds progressively as the length is reduced. This enables the SAH domain to act as a constant force spring in the mechanically dynamic environment of the cell.