An investigation into regional ventilation in infants and children; its distribution and determinants

Changing body position is commonly used in the management of individuals with respiratory diseases and those receiving mechanical ventilation, in order to optimise ventilation and oxygenation. In acute respiratory distress syndrome (ARDS), prone positioning is reported to improve oxygenation by recruiting collapsed dorsal lung regions, although this has not been confirmed in children. Ventilation distribution is well established in adults as being gravity dependent. Clinical practice in the paediatric population has been guided by the notion that all children, irrespective of the presence or absence of disease and age, consistently demonstrate the opposite ventilation distribution pattern to adults and this pattern is said to occur until the second decade of life. Studies in the paediatric population are limited to a few reported from the 1980's, on very heterogeneous populations. With advances in technology, new methods of examining regional ventilation, such as electrical impedance tomography (EIT), have become available. Recent neonatal studies using EIT have reported a dissimilar ventilation distribution to the conventional paediatric pattern. Despite a growing number of studies examining the effects of various interventions on ventilation distribution, very few exist in infants and children older than 6 months of age. Furthermore, differing methodologies and the manner in which ventilation distribution is described and analysed makes pooling the available data in the paediatric population extremely difficult. An understanding of how ventilation is distributed under normal conditions is imperative when examining the effects of different interventions and medical conditions on ventilation distribution. This thesis aimed to describe the effects of body position, head position, age, and respiratory muscle activity on ventilation distribution in children between six months and nine years of age under normal conditions, with respiratory disease, neuromuscular disease, and during mechanical ventilation. Furthermore, the effect on ventilation distribution of prone positioning in children with ARDS was evaluated. Regional ventilation distribution was measured using thoracic EIT and respiratory muscle activity was measured using surface electromyography (sEMG) using standardised methodology. Results of a series of sub-studies indicate that ventilation distribution is more complex and variable than previously thought, with no standard "paediatric pattern" of ventilation. Overall, greater ventilation occurred in the right and dorsal lungs, respectively, in different positons. Head position did not affect regional ventilation in the children studied. Age had a variable effect on ventilation distribution, with healthy children under 12 months of age more likely to follow the paediatric pattern, particularly in side lying positions; however the response was not uniform. The presence of mechanical ventilation, disease state and respiratory muscle activity did not affect ventilation distribution with these children also showing variable patterns of regional ventilation distribution. Data suggests that turning children with ARDS into the prone position does not result in recruitment of the dorsal lung regions, but rather more homogenous ventilation throughout the lungs. Furthermore, results suggest that children with greater ventilation inhomogeneity at baseline are more likely to respond positively (improvement in oxygenation index) to prone positioning. This research provides novel insights into ventilation distribution and respiratory muscle activity in infants and children older than six months of age under a number of different conditions. These results contribute to a better understanding of the factors influencing the distribution of regional ventilation and the mechanisms by which prone positioning in ARDS may improve oxygenation in this population. These findings have potentially important clinical implications, as well as providing baseline data for future clinical studies. Given the variability observed, these studies highlight the potential clinical utility of EIT to monitor different interventions and outcomes. An important strength of the studies presented in this thesis, is that they were performed in a standardised manner, using relatively homogenous individual populations and validated measures of describing ventilation distribution. This methodology could provide a template for future studies in the paediatric population, to allow for comparison between studies

Caspase-1 cleavage of the TLR adaptor TRIF inhibits autophagy and β-interferon production during pseudomonas aeruginosa infection

Bacterial infection can trigger autophagy and inflammasome activation, but the effects of inflammasome activation on autophagy are unknown. We examined this in the context of Pseudomonas aeruginosa macrophage infection, which triggers NLRC4 inflammasome activation. P. aeruginosa induced autophagy via TLR4 and its adaptor TRIF. NLRC4 and caspase-1 activation following infection attenuated autophagy. Caspase-1 directly cleaved TRIF to diminish TRIF-mediated signaling, resulting in inhibition of autophagy and in reduced type I interferon production. Expression of a caspase-1 resistant TRIF mutant enhanced autophagy and type I interferon production following infection. Preventing TRIF cleavage by caspase-1 in an in vivo model of P. aeruginosa infection resulted in enhanced bacterial autophagy, attenuated IL-1β production, and increased bacterial clearance. Additionally, TRIF cleavage by caspase-1 diminished NLRP3 inflammasome activation. Thus, caspase-1 mediated TRIF cleavage is a key event in controlling autophagy, type I interferon production, and inflammasome activation with important functional consequences

Mitochondrial damage contributes to Pseudomonas aeruginosa activation of the inflammasome and is downregulated by autophagy.

The nucleotide-binding domain, leucine-rich repeat containing family caspase recruitment domain containing 4 (NLRC4) inflammasome can be activated by pathogenic bacteria via products translocated through the microbial type III secretion apparatus (T3SS). Recent work has shown that activation of the NLRP3 inflammasome is downregulated by autophagy, but the influence of autophagy on NLRC4 activation is unclear. We set out to determine how autophagy might influence this process, using the bacterium Pseudomonas aeruginosa, which activates the NLRC4 inflammasome via its T3SS. Infection resulted in T3SS-dependent mitochondrial damage with increased production of reactive oxygen intermediates and release of mitochondrial DNA. Inhibiting mitochondrial reactive oxygen release or degrading intracellular mitochondrial DNA abrogated NLRC4 inflammasome activation. Moreover, macrophages lacking mitochondria failed to activate NLRC4 following infection. Removal of damaged mitochondria by autophagy significantly attenuated NLRC4 inflammasome activation. Mitochondrial DNA bound specifically to NLRC4 immunoprecipitates and transfection of mitochondrial DNA directly activated the NLRC4 inflammasome; oxidation of the DNA enhanced this effect. Manipulation of autophagy altered the degree of inflammasome activation and inflammation in an in vivo model of P. aeruginosa infection. Our results reveal a novel mechanism contributing to NLRC4 activation by P. aeruginosa via mitochondrial damage and release of mitochondrial DNA triggered by the bacterial T3SS that is downregulated by autophagy

International consensus guideline for reporting transmission electron microscopy results in the diagnosis of Primary Ciliary Dyskinesia (BEAT PCD TEM Criteria)

Primary Ciliary Dyskinesia (PCD) is a heterogeneous genetic condition. European and North American diagnostic guidelines recommend transmission electron microscopy (TEM) as one of a combination of tests to confirm a diagnosis. However, there is no definition of what constitutes a defect or consensus on reporting terminology. The aim of this project was to provide an internationally agreed ultrastructural classification for PCD diagnosis by TEM. A consensus guideline was developed by PCD electron microscopy experts representing 18 centres in 14 countries. An initial meeting and discussion were followed by a Delphi consensus process. The agreed guideline was then tested, modified and retested through exchange of samples and electron micrographs between the 18 diagnostic centres. The final guideline a) Provides agreed terminology and a definition of class 1 defects which are diagnostic for PCD; b) Identifies class 2 defects which can indicate a diagnosis of PCD in combination with other supporting evidence; c) Describes features which should be included in a ciliary ultrastructure report to assist multidisciplinary diagnosis of PCD d) Defines adequacy of a diagnostic sample. This tested and externally validated statement provides a clear guideline for the diagnosis of PCD by TEM which can be used to standardise diagnosis internationally.</p

Risk, reassurance and routine: a qualitative study of narrative understandings of the potential for HIV self-testing among men who have sex with men in England

BACKGROUND: HIV testing has seen a rapid evolution over the last decade with multiple modalities now in use globally. In recent years HIV self-testing (HIVST) has been legalised in the UK paving the way for further expansion of testing. Interventions are delivered in particular social contexts which shape uptake. It is therefore important to understand how novel interventions are likely to be received by their intended users. This study aims to understand how HIVST compliments existing testing strategies considered or adopted by men who have sex with men (MSM). We do this by analysing normative discourses surrounding HIV testing and their perceptions of HIVST's potential future roles. METHODS: Six focus group discussions (FGDs) were conducted with 47 MSM in London, Manchester and Plymouth. One focus group included only MSM who reported higher risk behaviours and one with those who had never tested for HIV. Data were analysed through a thematic framework analysis. RESULTS: Three main narratives for testing for HIV were identified: (i) testing in response to a specific risk event; (ii) as reassurance when there was a small amount of doubt or anxiety related to HIV; and (iii) in response to social norms perpetuated through peers, HIV community groups and the medical establishment to test regularly for HIV. HIVST had limited utility for men when testing in response to specific risk events except in the case of significant structural barriers to other testing opportunities. HIVST was considered to have utility when seeking reassurance, and was thought to be very useful when testing to satisfy the needs and expectations of others around regular testing. There was some ambivalence about the incursion of a clinical intervention into the home. CONCLUSIONS: HIVST following risk events will likely be limited to those for whom existing service provision is insufficient to meet immediate needs based on structural or personal barriers to testing. Obligations of biological citizenship are central to MSM's understanding of the utility of HIVST. In the context of discourses of biocitizenship, men perceive HIVST to have dual roles: firstly as a tool to manage (mild) anxiety around one's HIV status based on an acknowledgment of HIV vulnerability arising from being homosexually active. Secondly, HIVST is useful in complying with social norms and meeting the perceived demands of biomedicine

Mendelian adult-onset leukodystrophy genes in Alzheimer´s disease. Critical influence of CSF1R and NOTCH3

Mendelian adult-onset leukodystrophies are a spectrum of rare inherited progressive neurodegenerative disorders affecting the white matter of the central nervous system. Among these, Cerebral Autosomal Dominant and Recessive Arteriopathy with Subcortical Infarcts and Leukoencephalopathy (CADASIL and CARASIL), Cerebroretinal vasculopathy (CRV), Metachromatic leukodystrophy (MLD), Hereditary diffuse Leukoencephalopathy with spheroids (HDLS), Vanishing white matter disease (VWM) present with rapidly progressive dementia as dominant feature and are caused by mutations in NOTCH3, HTRA1, TREX1, ARSA, CSF1R, EIF2B1, EIF2B2, EIF2B3, EIF2B4, EIF2B5, respectively. Given the rare incidence of these disorders and the lack of unequivocally diagnostic features, leukodystrophies are frequently misdiagnosed with common sporadic dementing diseases such as Alzheimer’s disease (AD), raising the question of whether these overlapping phenotypes may be explained by shared genetic risk factors. To investigate this intriguing hypothesis, we have combined gene expression analysis 1) in 6 different AD mouse strains (APPPS1, HOTASTPM, HETASTPM, TPM, TAS10 and TAU), at 5 different developmental stages (Embryo [E15], 2 months, 4 months, 8 months and 18 months), 2) in APPPS1 primary cortical neurons under stress conditions (oxygen-glucose deprivation) and single-variant and single-gene (c-alpha and SKAT tests) based genetic screening in a cohort composed of 332 Caucasian late-onset AD patients and 676 Caucasian elderly controls. Csf1r was significantly overexpressed (Log2FC>1, adj. p-val<0.05) in the cortex and hippocampus of aged HOTASTPM mice with extensive Aβ core dense plaque pathology. We identified 3 likely pathogenic mutations in CSF1R TK domain (p.L868R, p.Q691H and p.H703Y) in our discovery and validation cohort, composed of 465 AD and MCI Caucasian patients from the UK. Moreover, NOTCH3 was a significant hit in the c-alpha test (adj p-val = 0.01). Adult onset Mendelian leukodystrophy genes are not common factors implicated in AD. Nevertheless, our study suggests a potential pathogenic link between NOTCH3, CSF1R and sporadic LOAD, that warrants further investigation

ABCA7 p.G215S as potential protective factor for Alzheimer’s disease

Genome-wide association studies (GWASs) have been effective approaches to dissect common genetic variability underlying complex diseases in a systematic and unbiased way. Recently, GWASs have led to the discovery of over 20 susceptibility loci for Alzheimer’s disease (AD). Despite the evidence showing the contribution of these loci to AD pathogenesis, their genetic architecture has not been extensively investigated, leaving the possibility that low frequency and rare coding variants may also occur and contribute to the risk of disease. We have used exome and genome sequencing data to analyse the single independent and joint effect of rare and low frequency protein coding variants in 9 AD GWAS loci with the strongest effect sizes after APOE (BIN1, CLU, CR1, PICALM, MS4A6A, ABCA7, EPHA1, CD33, CD2AP) in a cohort of 332 sporadic AD cases and 676 elderly controls of British and North American ancestry. We identified coding variability in ABCA7 as contributing to AD risk. This locus harbors a low frequency coding variant (p.G215S, rs72973581, MAF=4.3%) conferring a modest but statistically significant protection against AD (p-value= 6x10-4, OR=0.57, 95% CI 0.41-0.80). Notably, our results are not driven by an enrichment of loss of function variants in ABCA7, recently reported as main pathogenic factor underlying AD risk at this locus. In summary, our study confirms the role of ABCA7 in AD and provide new insights that should address functional studies

Ceremonies and Time in Shakespeare

This essay considers some moments in Shakespeare's texts which exemplify the Janus-faced quality of ceremonies: their enactment in the present looking backwards to past traditions and forwards to inaugurate new social relations. The argument draws on Victor Turner's theorization of ritual as an event that gives shape to “liminality,” that which “eludes or slips through the network of classification that normally locate states and positions in cultural space,” and argues that this applies to time as well. It also considers the construction of time in terms of kairos, a moment of time infused with meaning. The essay analyses ceremony in three Shakespearean genres. First, it examines Bertram's and Helena's ring exchange in All's Well That Ends Well as a “distended” ritual that collapses time. It then turns to Richard III, unpacking its complex sequence of ceremonies of betrothal, mourning, and sovereignty that are “continuously disrupted”. The final section describes the ceremonial time of romance in The Winter's Tale, unfolding the power invested in the kairotic time evoked by the oracle of Delphi, the sheep-shearing ceremony, and Paulina's “resurrection” of Hermione