Human platelet activation by Escherichia coli: roles for FcγRIIA and integrin αIIbβ3

Gram-negative Escherichia coli cause diseases such as sepsis and hemolytic uremic syndrome in which thrombotic disorders can be found. Direct platelet–bacterium interactions might contribute to some of these conditions; however, mechanisms of human platelet activation by E. coli leading to thrombus formation are poorly understood. While the IgG receptor FcγRIIA has a key role in platelet response to various Gram-positive species, its role in activation to Gram-negative bacteria is poorly defined. This study aimed to investigate the molecular mechanisms of human platelet activation by E. coli, including the potential role of FcγRIIA. Using light-transmission aggregometry, measurements of ATP release and tyrosine-phosphorylation, we investigated the ability of two E. coli clinical isolates to activate platelets in plasma, in the presence or absence of specific receptors and signaling inhibitors. Aggregation assays with washed platelets supplemented with IgGs were performed to evaluate the requirement of this plasma component in activation. We found a critical role for the immune receptor FcγRIIA, αIIbβ3, and Src and Syk tyrosine kinases in platelet activation in response to E. coli. IgG and αIIbβ3 engagement was required for FcγRIIA activation. Moreover, feedback mediators adenosine 5’-diphosphate (ADP) and thromboxane A₂ (TxA₂) were essential for platelet aggregation. These findings suggest that human platelet responses to E. coli isolates are similar to those induced by Gram-positive organisms. Our observations support the existence of a central FcγRIIA-mediated pathway by which human platelets respond to both Gram-negative and Gram-positive bacteria

The origins of intensive marine fishing in medieval Europe: the English evidence

The catastrophic impact of fishing pressure on species such as cod and herring is well documented. However, the antiquity of their intensive exploitation has not been established. Systematic catch statistics are only available for ca. 100 years, but large-scale fishing industries existed in medieval Europe and the expansion of cod fishing from the fourteenth century (first in Iceland, then in Newfoundland) played an important role in the European colonization of the Northwest Atlantic. History has demonstrated the scale of these late medieval and post-medieval fisheries, but only archaeology can illuminate earlier practices. Zooarchaeological evidence shows that the clearest changes in marine fishing in England between AD 600 and 1600 occurred rapidly around AD 1000 and involved large increases in catches of herring and cod. Surprisingly, this revolution predated the documented post-medieval expansion of England's sea fisheries and coincided with the Medieval Warm Period-when natural herring and cod productivity was probably low in the North Sea. This counterintuitive discovery can be explained by the concurrent rise of urbanism and human impacts on freshwater ecosystems. The search for 'pristine' baselines regarding marine ecosystems will thus need to employ medieval palaeoecological proxies in addition to recent fisheries data and early modern historical records

Genetic analysis of radiation resistance in Haloferax volcanii

Archaea,considered as the third domain of life alongside bacteria and eukaryotes, represent a highly diverse group of organisms. Attention to archaeal DNA repair pathways has been considerable for a long time and many archaeal species inhabit extreme environmental niches where there is a higher rate of genomic insult. It is therefore thought that such archaea possess efficient and robust novel DNA repair pathways, allowing survival in such conditions. Such extreme conditions can also be found beyond Earth, such as on the surface of Mars and investigation into DNA repair in the archaea represents a pivotal stepping stone to understanding how organisms adapt to “Martian” conditions. In the work presented here, the gene encoding a XerCD-like integrase, found within the integrated prophage on the main chromosome of Haloferax volcanii was isolated from a genomic library and overexpression leads to increased resistance to genotoxic stress imposed by ultraviolet light and mitomycin C. Deletion of this gene does not impact the growth rate or sensitivity to DNA damaging agents, likely due to the presence of an additional eleven homologs within the genome. Deletion of the entire prophage region does not delete all XerCD homologs, yet shows an even larger increase in cell survival after UV and MMC treatment. Genetic analysis suggests that XerCD may interact, directly or indirectly, with UvrC as overexpression of XerCD somewhat mitigates the UV sensitivity seen in a UvrC deleted strain. The defect is not fully complemented, so further study is required. Previous data has shown that various XerCD-like integrases are upregulated in the presence of MMC. Real-time PCR carried out here indicates that phage induction may occur when cells are treated with DNA damaging agents, which may contribute to the cell death seen, and therefore strains deleted for the integrated prophage may be more beneficial to use for DNA damaging assays due to increased cellular survival. Replication Protein A transcripts are upregulated in response to MMC, aiding in interstrand crosslink repair. The interplay between XerCD-like integrases, that usually function in DNA replication, and DNA repair warrants further study

Exploring the Psychopysiological Indices of Perceived Effort and its Self-Regulation

Effort involves the application of physical and mental resources towards a task. Individuals perceive effort during task engagement like exercise with a conscious sensation of how hard, heavy, and strenuous the exercise consciously feels to drive the working muscles and for breathing. Accordingly, individuals' decisions are thought to be guided by their perceived effort. In turn, there are numerous psychophysiological characteristics that underpin the perceived effort phenomenon which can also play a role in the overall decision-making processes and self-regulation of behaviour. However, it is often difficult to capture the underlying mechanisms of decision-making processes due to their erratic and complex nature. Consequently, there is scant literature on the psychophysiological indices of set perceived effort intensities and underlying decision-making processes during self-regulation of perceived effort. Yet, a small sample of studies have demonstrated that concurrent mixed-methods/process-tracing approaches can delve more into complex decision-making processes involved with regulating perceived effort and exercise behaviour. Subsequently, the main aim of the present thesis was to explore the psychophysiological indices of perceived effort and its self-regulation. This thesis comprises three separate studies. In Study 1, the reliability of a novel fixed perceived effort cycling task was investigated. Results demonstrated that a novel fixed perceived effort trial that corresponded ratings of perceived effort to a known physiological threshold was reliably produced over numerous bouts and elicited a consistent psychophysiological response for each perceived effort intensity. A following study (Study 2, Part A) also probed the psychophysiological responses associated with two intensities of fixed perceived effort. During these studies it appeared that physical outputs at a set perceived effort intensity would decrease over time to maintain the same perception of effort. Meanwhile, certain psychophysiological markers showed characteristic increases (e.g., heart rate) or decreases (e.g., affective valence) as the fixed perceived effort exercise progressed. As a result, specific intensities of perceived effort appear to exhibit different power output and psychophysiological responses in terms of magnitude and changes over time. This could possibly then be linked to different ways that perceived effort is self-regulated. It was also of interest how individuals self-regulated during fixed perceived effort exercise. To achieve this, Study 2 utilised a think aloud protocol to understand the behavioural and cognitive self-regulatory strategies that were used by participants at different fixed perceived effort intensities (Part A) as well as any differences in self-regulation between experienced and inexperienced cyclists (Part B). Within Part A, it was found that there was a greater change in power output during the higher intensity fixed perceived effort cycle, signifying a greater amount of behavioural self-regulation. Furthermore, the activation of cognitive strategies was also greater in the higher intensity fixed perceived effort task. When assessing differences between experience levels of participants, there were no significant differences in power output or major secondary themes of the think aloud protocol suggesting participants of any experience level may self-regulate perceived effort similarly. However, closer examination of the primary themes from the think aloud data suggest experience level may affect the cognitive self-regulatory strategies that are used during a prolonged fixed perceived effort intensity exercise. Finally, this thesis then explored any changes in self-regulation of perceived effort after an intervention which involved experimentally induced muscle pain. In addition, this study also incorporated the use of functional near infrared spectroscopy to assess the cognitive effort applied to activate cognitive self-regulation strategies during fixed perceived effort exercise. It was found that the presence of elevated muscle pain due to an intramuscular hypertonic saline injection cause a significantly lower power output than an isotonic placebo-control condition. In addition, near infrared spectroscopy data showed a greater change in deoxyhaemoglobin between condition suggesting a greater use of cognitive self-regulatory strategies as part of executive function when experiencing elevated muscle pain compared to a placebo-control. Overall, this thesis firstly found a novel fixed perceived effort exercise to be reliable. Using this task paradigm, additional studies show that specific intensities of perceived effort seem to elicit different power output and psychophysiological responses in terms of magnitude (e.g., higher/lower between intensities) and changes over time (condition x time interactions). Subsequently, data concerning the self-regulation of perceived effort shows that participants employ a mixture of behavioural (i.e., changing power output) and cognitive (i.e., engaging in reappraisal and/or self-talk) strategies to self-regulate perceived effort. In addition, there was a difference in self-regulatory strategies between conditions which involved elevated muscle pain (hypertonic saline injection) or a no elevated muscle pain (isotonic saline injection). Therefore, the self-regulation of perceived effort is likely context dependent and there are also likely to be some individual preferences towards how perceived effort is self-regulated

Genetic analysis of radiation resistance in Haloferax volcanii

Archaea,considered as the third domain of life alongside bacteria and eukaryotes, represent a highly diverse group of organisms. Attention to archaeal DNA repair pathways has been considerable for a long time and many archaeal species inhabit extreme environmental niches where there is a higher rate of genomic insult. It is therefore thought that such archaea possess efficient and robust novel DNA repair pathways, allowing survival in such conditions. Such extreme conditions can also be found beyond Earth, such as on the surface of Mars and investigation into DNA repair in the archaea represents a pivotal stepping stone to understanding how organisms adapt to “Martian” conditions. In the work presented here, the gene encoding a XerCD-like integrase, found within the integrated prophage on the main chromosome of Haloferax volcanii was isolated from a genomic library and overexpression leads to increased resistance to genotoxic stress imposed by ultraviolet light and mitomycin C. Deletion of this gene does not impact the growth rate or sensitivity to DNA damaging agents, likely due to the presence of an additional eleven homologs within the genome. Deletion of the entire prophage region does not delete all XerCD homologs, yet shows an even larger increase in cell survival after UV and MMC treatment. Genetic analysis suggests that XerCD may interact, directly or indirectly, with UvrC as overexpression of XerCD somewhat mitigates the UV sensitivity seen in a UvrC deleted strain. The defect is not fully complemented, so further study is required. Previous data has shown that various XerCD-like integrases are upregulated in the presence of MMC. Real-time PCR carried out here indicates that phage induction may occur when cells are treated with DNA damaging agents, which may contribute to the cell death seen, and therefore strains deleted for the integrated prophage may be more beneficial to use for DNA damaging assays due to increased cellular survival. Replication Protein A transcripts are upregulated in response to MMC, aiding in interstrand crosslink repair. The interplay between XerCD-like integrases, that usually function in DNA replication, and DNA repair warrants further study

Instanton test of non-supersymmetric deformations of the AdS_5 x S^5

We consider instanton effects in a non-supersymmetric gauge theory obtained by marginal deformations of the N=4 SYM. This gauge theory is expected to be dual to type IIB string theory on the AdS_5 times deformed-S^5 background. From an instanton calculation in the deformed gauge theory we extract the prediction for the dilaton-axion field \tau in dual string theory. In the limit of small deformations where the supergravity regime is valid, our instanton result reproduces the expression for \tau of the supergravity solution found by Frolov.Comment: 15 page

The biomechanics of chewing and suckling in the infant: A potential mechanism for physiologic metopic suture closure

Craniosynostosis is a condition with neurologic and aesthetic sequelae requiring invasive surgery. Understanding its pathobiology requires familiarity with the processes underlying physiologic suture closure. Animal studies have shown that cyclical strain from chewing and suckling influences the closure of cranial vault sutures, especially the metopic, an important locus of craniosynostosis. However, there are no human data correlating strain patterns during chewing and suckling with the physiologically early closure pattern of the metopic suture. Furthermore, differences in craniofacial morphology make it challenging to directly extrapolate animal findings to humans. Eight finite-element analysis (FEA) models were built from craniofacial computer tomography (CT) scans at varying stages of metopic suture closure, including two with isolated non-syndromic metopic craniosynostosis. Muscle forces acting on the cranium during chewing and suckling were simulated using subject-specific jaw muscle cross-sectional areas. Chewing and suckling induced tension at the metopic and sagittal sutures, and compressed the coronal, lambdoid, and squamous sutures. Relative to other cranial vault sutures, the metopic suture experienced larger magnitudes of axial strain across the suture and a lower magnitude of shear strain. Strain across the metopic suture decreased during suture closure, but other sutures were unaffected. Strain patterns along the metopic suture mirrored the anterior to posterior sequence of closure: strain magnitudes were highest at the glabella and decreased posteriorly, with minima at the nasion and the anterior fontanelle. In models of physiologic suture closure, increased degree of metopic suture closure correlated with higher maximum principal strains across the frontal bone and mid-face, a strain regime not observed in models of severe metopic craniosynostosis. In summary, our work provides human evidence that bone strain patterns from chewing and suckling correlate with the physiologically early closure pattern of the metopic suture, and that deviations from physiologic strain regimes may contribute to clinically observed craniofacial dysmorphism

A Framework for Auditable Synthetic Data Generation

Synthetic data has gained significant momentum thanks to sophisticated machine learning tools that enable the synthesis of high-dimensional datasets. However, many generation techniques do not give the data controller control over what statistical patterns are captured, leading to concerns over privacy protection. While synthetic records are not linked to a particular real-world individual, they can reveal information about users indirectly which may be unacceptable for data owners. There is thus a need to empirically verify the privacy of synthetic data -- a particularly challenging task in high-dimensional data. In this paper we present a general framework for synthetic data generation that gives data controllers full control over which statistical properties the synthetic data ought to preserve, what exact information loss is acceptable, and how to quantify it. The benefits of the approach are that (1) one can generate synthetic data that results in high utility for a given task, while (2) empirically validating that only statistics considered safe by the data curator are used to generate the data. We thus show the potential for synthetic data to be an effective means of releasing confidential data safely, while retaining useful information for analysts

One-Loop MHV Amplitudes in Supersymmetric Gauge Theories

Using CSW rules for constructing scalar Feynman diagrams from MHV vertices, we compute the contribution of $\mathcal {N}=1$ chiral multiplet to one-loop MHV gluon amplitude. The result agrees with the one obtained previously using unitarity-based methods, thereby demonstrating the validity of the MHV-diagram technique, in the case of one-loop MHV amplitudes, for all massless supersymmetric theories.Comment: 20 pages, 5 figure