Similar Endothelial Glycocalyx Structures in Microvessels from a Range of Mammalian Tissues: Evidence for a Common Filtering Mechanism?

AbstractThe glycocalyx or endocapillary layer on the luminal surface of microvessels has a major role in the exclusion of macromolecules from the underlying endothelial cells. Current structural evidence in the capillaries of frog mesentery indicates a regularity in the structure of the glycocalyx, with a center-to-center fiber spacing of 20 nm and a fiber width of 12 nm, which might explain the observed macromolecular filtering properties. In this study, we used electron micrographs of tissues prepared using perfusion fixation and tannic acid treatment. The digitized images were analyzed using autocorrelation to find common spacings and to establish whether similar structures, hence mechanisms, are present in the microvessel glycocalyces of a variety of mammalian tissues. Continuous glycocalyx layers in mammalian microvessels of choroid, renal tubules, glomerulus, and psoas muscle all showed similar lateral spacings at ∼19.5 nm (possibly in a quasitetragonal lattice) and longer spacings above 100 nm. Individual glycocalyx tufts above fenestrations in the first three of these tissues and also in stomach fundus and jejunum showed evidence for similar short-range structural regularity, but with more disorder. The fiber diameter was estimated as 18.8 (± 0.2) nm, but we believe this is an overestimate because of the staining method used. The implications of these findings are discussed

Patient, health service factors and variation in mortality following resuscitated out-of-hospital cardiac arrest in acute coronary syndrome : analysis of the Myocardial Ischaemia National Audit Project

Aims To determine patient and health service factors associated with variation in hospital mortality among resuscitated cases of out-of-hospital cardiac arrest (OHCA) with acute coronary syndrome (ACS). Methods In this cohort study, we used the Myocardial Ischaemia National Audit Project database to study outcomes in patients hospitalised with resuscitated OHCA due to ACS between 2003 and 2015 in the United Kingdom. We analysed variation in inter-hospital mortality and used hierarchical multivariable regression models to examine the association between patient and health service factors with hospital mortality. Results We included 17604 patients across 239 hospitals. Overall hospital mortality was 28.7%. In 94 hospitals that contributed at least 60 cases, mortality by hospital ranged from 10.7% to 66.3% (median 28.6%, IQR 23.2% to 39.1%)). Patient and health service factors explained 36.1% of this variation. After adjustment for covariates, factors associated with higher hospital mortality included increasing serum glucose, ST-Elevation myocardial infarction (STEMI) diagnosis, and initial admission to a primary percutaneous coronary intervention (pPCI) capable hospital. Hospital OHCA volume was not associated with mortality. The key modifiable factor associated with lower mortality was early reperfusion therapy in STEMI patients. Conclusion There was wide variation in inter-hospital mortality following resuscitated OHCA due to ACS that was only partially explained by patient and health service factors. Hospital OHCA volume and pPCI capability were not associated with lower mortality. Early reperfusion therapy was associated with lower mortality in STEMI patients

Scale-free memory model for multiagent reinforcement learning. Mean field approximation and rock-paper-scissors dynamics

A continuous time model for multiagent systems governed by reinforcement learning with scale-free memory is developed. The agents are assumed to act independently of one another in optimizing their choice of possible actions via trial-and-error search. To gain awareness about the action value the agents accumulate in their memory the rewards obtained from taking a specific action at each moment of time. The contribution of the rewards in the past to the agent current perception of action value is described by an integral operator with a power-law kernel. Finally a fractional differential equation governing the system dynamics is obtained. The agents are considered to interact with one another implicitly via the reward of one agent depending on the choice of the other agents. The pairwise interaction model is adopted to describe this effect. As a specific example of systems with non-transitive interactions, a two agent and three agent systems of the rock-paper-scissors type are analyzed in detail, including the stability analysis and numerical simulation. Scale-free memory is demonstrated to cause complex dynamics of the systems at hand. In particular, it is shown that there can be simultaneously two modes of the system instability undergoing subcritical and supercritical bifurcation, with the latter one exhibiting anomalous oscillations with the amplitude and period growing with time. Besides, the instability onset via this supercritical mode may be regarded as "altruism self-organization". For the three agent system the instability dynamics is found to be rather irregular and can be composed of alternate fragments of oscillations different in their properties.Comment: 17 pages, 7 figur

The effect of neprilysin inhibition on left ventricular remodeling in patients with asymptomatic left ventricular systolic dysfunction late after myocardial infarction

Background: Patients with left ventricular systolic dysfunction (LVSD) following myocardial infarction (MI) are at high risk of developing heart failure. The addition of neprilysin inhibition to renin angiotensin system (RAS) inhibition may result in greater attenuation of adverse LV remodeling due to increased levels of substrates for neprilysin with vasodilatory, anti-hypertrophic, anti-fibrotic and sympatholytic effects. Methods: We performed a prospective, multi-center, randomized, double-blind, active-comparator trial comparing sacubitril/valsartan 97/103mg twice daily with valsartan 160mg twice daily in patients ≥3 months following MI with a LV ejection fraction (LVEF) ≤40% who were taking a RAS inhibitor (equivalent dose of ramipril ≥2.5mg twice daily), and a beta-blocker unless contraindicated or intolerant. Patients in New York Heart Association functional classification ≥II or with signs and symptoms of HF were excluded. The primary outcome was change from baseline to 52-weeks in LV end-systolic volume index (LVESVI) measured using cardiac magnetic resonance imaging (MRI). Secondary outcomes included other MRI measurements of LV remodeling, change in N-terminal prohormone of B-type natriuretic peptide (NT-proBNP) and high-sensitivity cardiac troponin I (hs-TnI), and a patient global assessment of change questionnaire. Results: From July 2018 to June 2019, 93 patients were randomized: mean age 60.7±10.4 years, median time from MI 3.6 years (IQR 1.2-7.2), mean LVEF 36.8%±7.1, median NT-proBNP 230pg/mL (124-404). Sacubitril/valsartan, compared with valsartan, did not significantly reduce LVESVI; adjusted between-group difference -1.9mL/m2 (95%CI -4.9, 1.0); p=0.19. There were no significant between-group differences in NT-proBNP, hs-TnI, LV end-diastolic volume index, left atrial volume index, LVEF, LV mass index, or patient global assessment of change. Conclusions: In patients with asymptomatic LVSD following MI, treatment with sacubitril/valsartan did not have a significant reverse remodeling effect compared with valsartan. Clinical Trial Registration: URL: https://www.clinicaltrials.gov Unique identifier: NCT0355257

Effects of sleep deprivation on neural functioning: an integrative review

Sleep deprivation has a broad variety of effects on human performance and neural functioning that manifest themselves at different levels of description. On a macroscopic level, sleep deprivation mainly affects executive functions, especially in novel tasks. Macroscopic and mesoscopic effects of sleep deprivation on brain activity include reduced cortical responsiveness to incoming stimuli, reflecting reduced attention. On a microscopic level, sleep deprivation is associated with increased levels of adenosine, a neuromodulator that has a general inhibitory effect on neural activity. The inhibition of cholinergic nuclei appears particularly relevant, as the associated decrease in cortical acetylcholine seems to cause effects of sleep deprivation on macroscopic brain activity. In general, however, the relationships between the neural effects of sleep deprivation across observation scales are poorly understood and uncovering these relationships should be a primary target in future research

Integrating sequence and array data to create an improved 1000 Genomes Project haplotype reference panel

A major use of the 1000 Genomes Project (1000GP) data is genotype imputation in genome-wide association studies (GWAS). Here we develop a method to estimate haplotypes from low-coverage sequencing data that can take advantage of single-nucleotide polymorphism (SNP) microarray genotypes on the same samples. First the SNP array data are phased to build a backbone (or 'scaffold') of haplotypes across each chromosome. We then phase the sequence data 'onto' this haplotype scaffold. This approach can take advantage of relatedness between sequenced and non-sequenced samples to improve accuracy. We use this method to create a new 1000GP haplotype reference set for use by the human genetic community. Using a set of validation genotypes at SNP and bi-allelic indels we show that these haplotypes have lower genotype discordance and improved imputation performance into downstream GWAS samples, especially at low-frequency variants. © 2014 Macmillan Publishers Limited. All rights reserved