Membrane protein sequestering by ionic protein–lipid interactions.

Neuronal exocytosis is catalyzed by the SNARE protein syntaxin-1A(1). Syntaxin-1A is clustered in the plasma membrane at sites where synaptic vesicles undergo exocytosis(2,3). However, how syntaxin-1A is sequestered is unknown. Here, we show that syntaxin clustering is mediated by electrostatic interactions with the strongly anionic lipid phosphatidylinositol-4,5-bisphosphate (PIP2). We found with super-resolution STED microscopy on the plasma membrane of PC12 cells that PIP2 is the dominant inner-leaflet lipid in ~73 nm-sized microdomains. This high accumulation of PIP2 was required for syntaxin-1A sequestering, as destruction of PIP2 by the phosphatase synaptojanin-1 reduced syntaxin-1A clustering. Furthermore, co-reconstitution of PIP2 and the C-terminal part of syntaxin-1A in artificial giant unilamellar vesicles resulted in segregation of PIP2 and syntaxin-1A into distinct domains even when cholesterol was absent. Our results demonstrate that electrostatic protein-lipid interactions can result in the formation of microdomains independent of cholesterol or lipid phases

Managing the complexity of doing it all : an exploratory study on students' experiences when trained stepwise in conducting consultations

Background: At most medical schools the components required to conduct a consultation, medical knowledge, communication, clinical reasoning and physical examination skills, are trained separately. Afterwards, all the knowledge and skills students acquired must be integrated into complete consultations, an art that lies at the heart of the medical profession. Inevitably, students experience conducting consultations as complex and challenging. Literature emphasizes the importance of three didactic course principles: moving from partial tasks to whole task learning, diminishing supervisors' support and gradually increasing students' responsibility. This study explores students' experiences of an integrated consultation course using these three didactic principles to support them in this difficult task. Methods: Six focus groups were conducted with 20 pre-clerkship and 19 clerkship students in total. Discussions were audiotaped, transcribed and analysed by Nvivo using the constant comparative strategy within a thematic analysis. Results: Conducting complete consultations motivated students in their learning process as future physician. Initially, students were very much focused on medical problem solving. Completing the whole task of a consultation obligated them to transfer their theoretical medical knowledge into applicable clinical knowledge on the spot. Furthermore, diminishing the support of a supervisor triggered students to reflect on their own actions but contrasted with their increased appreciation of critical feedback. Increasing students' responsibility stimulated their active learning but made some students feel overloaded. These students were anxious to miss patient information or not being able to take the right decisions or to answer patients' questions, which sometimes resulted in evasive coping techniques, such as talking faster to prevent the patient asking questions. Conclusion: The complex task of conducting complete consultations should be implemented early within medical curricula because students need time to organize their medical knowledge into applicable clinical knowledge. An integrated consultation course should comprise a step-by-step teaching strategy with a variety of supervisors' feedback modi, adapted to students' competence. Finally, students should be guided in formulating achievable standards to prevent them from feeling overloaded in practicing complete consultations with simulated or real patients

Familial analysis of MMN in cannabis users: A case study

Abstract presented at the 23rd Australasian Society for Psychophysiology Conference, 20-22 Nov 2013, Wollongong, Australi

Therapeutic Effects of Prolonged Cannabidiol Treatment on Psychological Symptoms and Cognitive Function in Regular Cannabis Users: A Pragmatic Open-Label Clinical Trial.

Introduction: Chronic cannabis use has been associated with impaired cognition and elevated psychological symptoms, particularly psychotic-like experiences. While Δ9-tetrahydrocannabinol (THC) is thought to be primarily responsible for these deleterious effects, cannabidiol (CBD) is purported to have antipsychotic properties and to ameliorate cognitive, symptomatic, and brain harms in cannabis users. However, this has never been tested in a prolonged administration trial in otherwise healthy cannabis users. Here, we report the first study of prolonged CBD administration to a community sample of regular cannabis users in a pragmatic trial investigating potential restorative effects of CBD on psychological symptoms and cognition. Materials and Methods: Twenty frequent cannabis users (16 male, median age 25 years) underwent a 10-week open-label trial of 200 mg of daily oral CBD treatment, while continuing to use cannabis as usual. The majority of participants were daily cannabis users who had used cannabis for several years (median 5.5 years of regular use). Participants underwent psychological and cognitive assessments at baseline (BL) and post-treatment (PT) and were monitored weekly throughout the trial. Results: CBD was well tolerated with no reported side effects; however, participants retrospectively reported reduced euphoria when smoking cannabis. No impairments to cognition were found, nor were there deleterious effects on psychological function. Importantly, participants reported significantly fewer depressive and psychotic-like symptoms at PT relative to BL, and exhibited improvements in attentional switching, verbal learning, and memory. Increased plasma CBD concentrations were associated with improvements in attentional control and beneficial changes in psychological symptoms. Greater benefits were observed in dependent than in nondependent cannabis users. Conclusions: Prolonged CBD treatment appears to have promising therapeutic effects for improving psychological symptoms and cognition in regular cannabis users. Our findings require replication given the lack of a placebo control in this pragmatic trial, but suggest that CBD may be a useful adjunct treatment for cannabis dependence

Algorithmic corrections for localization microscopy with sCMOS cameras - characterisation of a computationally efficient localization approach

Modern sCMOS cameras are attractive for single molecule localization microscopy (SMLM) due to their high speed but suffer from pixel non-uniformities that can affect localization precision and accuracy. We present a simplified sCMOS non-uniform noise model that incorporates pixel specific read-noise, offset and sensitivity variation. Using this model we develop a new weighted least squared (WLS) fitting method designed to remove the effect of sCMOS pixel non-uniformities. Simulations with the sCMOS noise model, performed to test under which conditions sCMOS specific localization corrections are required, suggested that pixel specific offsets should always be removed. In many applications with thick biological samples photon fluxes are sufficiently high that corrections of read-noise and sensitivity correction may be neglected. When correction is required, e.g. during fast imaging in thin samples, our WLS fit procedure recovered the performance of an equivalent sensor with uniform pixel properties and the fit estimates also attained the Cramer-Rao lower bound. Experiments with sub-resolution beads and a DNA origami test sample confirmed the results of the simulations. The WLS localization procedure is fast to converge, compatible with 2D, 3D and multi-emitter localization and thus provides a computationally efficient sCMOS localization approach compatible with most SMLM modalities

Monte Carlo Simulations indicate that Chromati: Nanostructure is accessible by Light Microscopy

A long controversy exists about the structure of chromatin. Theoretically, this structure could be resolved by scattering experiments if one determines the scattering function - or equivalently the pair distribution function - of the nucleosomes. Unfortunately, scattering experiments with live cells are very difficult and limited to only a couple of nucleosomes

Influence of Reoperations on Long-Term Quality of Life After Restrictive Procedures: A Prospective Study

Quality of life improves after bariatric surgery. However, long-term results and the influence of reoperations are not well known. A prospective quality of life assessment before, 1 and 7 years after laparoscopic adjustable gastric banding (LAGB) and vertical banded gastroplasty (VBG) was performed in order to determine the influence of reoperations during follow-up. One hundred patients were included in the study. Fifty patients underwent VBG and 50 LAGB. Patients completed the quality of life questionnaires prior to surgery and two times during follow-up. Health-related quality of life (HRQoL) questionnaires included the Nottingham Health Profile I and II and the Sickness Impact Profile 68. Follow-up was 84% with a mean duration of 84 months (7 years). During follow-up, 65% of VBG patients underwent conversion to Roux-en-Y gastric bypass while 44% of LAGB patients underwent a reoperation or conversion. One year after the procedure, nearly all quality-of-life parameters significantly improved. After 7 years, the Nottingham Health Profile (NHP)-I domain “physical ability”, the NHP-II and the SIP-68 domains “mobility control”, “social behavior”, and “mobility range” were still significantly improved in both groups. The domains “emotional reaction”, “social isolation” (NHP-I), and “emotional stability” (SIP-68) remained significantly improved in the VBG group while this was true for the domain “energy level” (NHP-I) in the LAGB group. Both the type of procedure and reoperations during follow-up were not of significant influence on the HRQoL results. Weight loss and decrease in comorbidities were the only significant factors influencing quality of life. Restrictive bariatric surgery improves quality of life. Although results are most impressive 1 year after surgery, the improvement remains significant after long-term follow-up. Postoperative quality of life is mainly dependent on weight loss and decrease in comorbidities and not on the type of procedure or surgical complications

The reliability of in-training assessment when performance improvement is taken into account

During in-training assessment students are frequently assessed over a longer period of time and therefore it can be expected that their performance will improve. We studied whether there really is a measurable performance improvement when students are assessed over an extended period of time and how this improvement affects the reliability of the overall judgement. In-training assessment results were obtained from 104 students on rotation at our university hospital or at one of the six affiliated hospitals. Generalisability theory was used in combination with multilevel analysis to obtain reliability coefficients and to estimate the number of assessments needed for reliable overall judgement, both including and excluding performance improvement. Students’ clinical performance ratings improved significantly from a mean of 7.6 at the start to a mean of 7.8 at the end of their clerkship. When taking performance improvement into account, reliability coefficients were higher. The number of assessments needed to achieve a reliability of 0.80 or higher decreased from 17 to 11. Therefore, when studying reliability of in-training assessment, performance improvement should be considered