Atomic force microscopy-based mechanobiology

Mechanobiology emerges at the crossroads of medicine, biology, biophysics and engineering and describes how the responses of proteins, cells, tissues and organs to mechanical cues contribute to development, differentiation, physiology and disease. The grand challenge in mechanobiology is to quantify how biological systems sense, transduce, respond and apply mechanical signals. Over the past three decades, atomic force microscopy (AFM) has emerged as a key platform enabling the simultaneous morphological and mechanical characterization of living biological systems. In this Review, we survey the basic principles, advantages and limitations of the most common AFM modalities used to map the dynamic mechanical properties of complex biological samples to their morphology. We discuss how mechanical properties can be directly linked to function, which has remained a poorly addressed issue. We outline the potential of combining AFM with complementary techniques, including optical microscopy and spectroscopy of mechanosensitive fluorescent constructs, super-resolution microscopy, the patch clamp technique and the use of microstructured and fluidic devices to characterize the 3D distribution of mechanical responses within biological systems and to track their morphology and functional state.Peer ReviewedPostprint (published version

Evolutionary conserved NSL complex/BRD4 axis controls transcription activation via histone acetylation

Cells rely on a diverse repertoire of genes for maintaining homeostasis, but the transcriptional networks underlying their expression remain poorly understood. The MOF acetyltransferase-containing Non-Specific Lethal (NSL) complex is a broad transcription regulator. It is essential in Drosophila, and haploinsufficiency of the human KANSL1 subunit results in the Koolen-de Vries syndrome. Here, we perform a genome-wide RNAi screen and identify the BET protein BRD4 as an evolutionary conserved co-factor of the NSL complex. Using Drosophila and mouse embryonic stem cells, we characterise a recruitment hierarchy, where NSL-deposited histone acetylation enables BRD4 recruitment for transcription of constitutively active genes. Transcriptome analyses in Koolen-de Vries patient-derived fibroblasts reveals perturbations with a cellular homeostasis signature that are evoked by the NSL complex/BRD4 axis. We propose that BRD4 represents a conserved bridge between the NSL complex and transcription activation, and provide a new perspective in the understanding of their functions in healthy and diseased states

Angiotensin 1-7 Rescues Cognitive Decline and Neuronal Loss Following Traumatic Brain Injury in Mice

Purpose of study: Traumatic brain injury (TBI) is a leading cause of death and disability in the U.S., accounting for approximately 30% of all injury deaths and 3 million TBI-related emergency visits yearly. There is limited research in the area of mitigating the post-inflammatory effects of non-fatal traumatic brain injury. Angiotensin 1-7, an endogenous peptide that acts on the MAS receptor, has recently shown to be anti-inflammatory, anti-oxidative, and vasodilatory unlike its relative, angiotensin II. We asked the question of whether Ang 1-7 modulates neuroinflammation and improves cognitive function in mice following traumatic brain injury. Methods: A controlled cortical impactor with a retractable piston was used to model a mild traumatic brain injury (mTBI). Mice either received Ang 1-7 (1 mg/kg, n=12) or normal saline (0.9%, n=12) 2 hours post-TBI and 30 minutes prior to novel objection recognition (NOR) testing on days 1, 3, 7, 14 post-TBI with tissue harvesting for hematoxylin and eosin (H&E) staining. Results: Between-group studies showed that Ang 1-7 treated mice showed significantly higher NOR ratios compared to that of the control group. Additionally, statistically significant higher neuronal count in the ipsilateral hippocampal and cortical tissues days 1, 3, 7, and 14 post-TBI was observed in the Ang-1-7 group. Conclusion: Together, these results demonstrate that Ang 1-7 significantly improves cognitive function and rescues further cell loss against secondary intrinsic injury following extrinsic mTBI and suggest that it may be a novel therapy to the effects of mild traumatic brain injury

Understanding Body-Worn Camera Diffusion in U.S. Policing

By 2016, approximately one half of American police agencies had adopted body-worn cameras (BWCs). Although a growing body of research has examined the impact of BWCs on outcomes such as use of force, complaints, and perceptions of police, few have considered how and why some agencies adopted BWCs, while others have not. With guidance from the diffusion of innovations paradigm, this study explores variation in BWC adoption by police agencies. Drawing on a survey administered to a national probability sample of 665 municipal police executives in the spring of 2018, we found agency size, region, and the demographic composition of municipalities were associated with BWC usage. We then examined executives’ support for (or opposition to) legislation that would require BWC footage to be released publicly. Results suggest (a) a variety of environmental factors were associated with support and (b) the correlates of support varied across agencies of different sizes

Inertial picobalance reveals fast mass fluctuations in mammalian cells

The regulation of size, volume and mass in living cells is physiologically important, and dysregulation of these parameters gives rise to many diseases. Cell mass is largely determined by the amount of water, proteins, lipids, carbohydrates and nucleic acids present in a cell, and is tightly linked to metabolism, proliferation and gene expression. Technologies have emerged in recent years that make it possible to track the masses of single suspended cells and adherent cells. However, it has not been possible to track individual adherent cells in physiological conditions at the mass and time resolutions required to observe fast cellular dynamics. Here we introduce a cell balance (a 'picobalance'), based on an optically excited microresonator, that measures the total mass of single or multiple adherent cells in culture conditions over days with millisecond time resolution and picogram mass sensitivity. Using our technique, we observe that the mass of living mammalian cells fluctuates intrinsically by around one to four per cent over timescales of seconds throughout the cell cycle. Perturbation experiments link these mass fluctuations to the basic cellular processes of ATP synthesis and water transport. Furthermore, we show that growth and cell cycle progression are arrested in cells infected with vaccinia virus, but mass fluctuations continue until cell death. Our measurements suggest that all living cells show fast and subtle mass fluctuations throughout the cell cycle. As our cell balance is easy to handle and compatible with fluorescence microscopy, we anticipate that our approach will contribute to the understanding of cell mass regulation in various cell states and across timescales, which is important in areas including physiology, cancer research, stem-cell differentiation and drug discovery

The relations between DISC-IV DSM diagnoses of ADHD and multi-informant CBCL-AP syndrome scores

Background: Previous studies have examined the relation between attention problems (APs) obtained with the Child Behavior Checklist (CBCL) and attention deficit hyperactivity disorder (ADHD) assessed with the Diagnostic and Statistical Manual of Mental Disorders (DSM). We will examine this relation across sex using multi-informant data. Methods: Parents of 12 538 twins, aged 7, 10, and 12 years, and teachers of twins, aged 10 years, completed the questionnaires. The mothers of a sample of 283 boys and 291 girls who scored either low or high on longitudinal maternal CBCL-AP were interviewed. Results: Children with a low AP score obtained a negative ADHD diagnosis in 96% of cases. Children with a high AP score obtained a positive diagnosis in 36% (girls) and 59% (boys) of cases. The association between paternal and maternal AP ratings and ADHD was the same, whereas the association between teacher AP ratings and ADHD was low. Conclusions: The association between AP and ADHD is higher in boys than girls, possibly because of a bias toward the male manifestation of ADHD. © 2006 Elsevier Inc. All rights reserved

Study of user-experience of an objective test (QbTest) to aid ADHD assessment and medication management: a multi-methods approach

Background The diagnosis and monitoring of Attention deficit hyperactivity disorder (ADHD) typically relies on subjective reports and observations. Objective continuous performance tests (CPTs) have been incorporated into some services to support clinical decision making. However, the feasibility and acceptability of adding such a test into routine practice is unknown. The study aimed to investigate the feasibility and acceptability of adding an objective computerised test to the routine assessment and monitoring of attention deficit hyperactivity disorder (ADHD). Methods Semi-structured interviews were conducted with clinicians (n = 10) and families (parents/young people, n = 20) who participated in a randomised controlled trial. Additionally, the same clinicians (n = 10) and families (n = 76) completed a survey assessing their experience of the QbTest. The study took place in child and adolescent mental health and community paediatric clinics across the UK. Interview transcripts were thematically analysed. Results Interviewed clinicians and families valued the QbTest for providing an objective, valid assessment of symptoms. The QbTest was noted to facilitate communication between clinicians, families and schools. However, whereas clinicians were more unanimous on the usefulness of the QbTest, survey findings showed that, although the majority of families found the test useful, less than half felt the QbTest helped them understand the clinician’s decision making around diagnosis and medication. The QbTest was seen as a potentially valuable tool to use early in the assessment process to streamline the care pathway. Although clinicians were conscious of the additional costs, these could be offset by reductions in time to diagnosis and the delivery of the test by a Healthcare Assistant. Conclusions The findings indicate the QbTest is an acceptable and feasible tool to implement in routine clinical settings. Clinicians should be mindful to discuss the QbTest results with families to enable their understanding and engagement with the process. Further findings from definitive trials are required to understand the cost/benefit; however, the findings from this study support the feasibility and acceptability of integrating QbTest in the ADHD care pathway

Assessment and Etiology of Attention Deficit Hyperactivity Disorder and Oppositional Defiant Disorder in Boys and Girls

Attention deficit hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD) are more common in boys than girls. In this paper, we investigated whether the prevalence differences are attributable to measurement bias. In addition, we examined sex differences in the genetic and environmental influences on variation in these behaviors. Teachers completed the Conners Teacher Rating Scale-Revised:Short version (CTRS-R:S) in a sample of 800 male and 851 female 7-year-old Dutch twins. No sex differences in the factor structure of the CTRS-R:S were found, implying the absence of measurement bias. The heritabilities for both ADHD and ODD were high and were the same in boys and girls. However, partly different genes are expressed in boys and girls

Active microrheology and simultaneous visualization of sheared phospholipid monolayers

Two-dimensional films of surface-active agents—from phospholipids and proteins to nanoparticles and colloids—stabilize fluid interfaces, which are essential to the science, technology and engineering of everyday life. The 2D nature of interfaces present unique challenges and opportunities: coupling between the 2D films and the bulk fluids complicates the measurement of surface dynamic properties, but allows the interfacial microstructure to be directly visualized during deformation. Here we present a novel technique that combines active microrheology with fluorescence microscopy to visualize fluid interfaces as they deform under applied stress, allowing structure and rheology to be correlated on the micron-scale in monolayer films. We show that even simple, single-component lipid monolayers can exhibit viscoelasticity, history dependence, a yield stress and hours-long time scales for elastic recoil and aging. Simultaneous visualization of the monolayer under stress shows that the rich dynamical response results from the cooperative dynamics and deformation of liquid-crystalline domains and their boundaries