Hammersmith Hospital Campus
Hammersmith Hospital Campus
Takahashi Y.,Tohoku University |
Shevchuk A.I.,University of Southampton |
Novak P.,Imperial College London |
Babakinejad B.,Imperial College London |
And 7 more authors.
Proceedings of the National Academy of Sciences of the United States of America | Year: 2012
We describe voltage-switching mode scanning electrochemical microscopy (VSM-SECM), in which a single SECM tip electrode was used to acquire high-quality topographical and electrochemical images of living cells simultaneously. This was achieved by switching the applied voltage so as to change the faradaic current from a hindered diffusion feedback signal (for distance control and topographical imaging) to the electrochemical flux measurement of interest. This imaging method is robust, and a single nanoscale SECM electrode, which is simple to produce, is used for both topography and activity measurements. In order to minimize the delay at voltage switching, we used pyrolytic carbon nanoelectrodes with 6.5-100 nm radii that rapidly reached a steady-state current, typically in less than 20 ms for the largest electrodes and faster for smaller electrodes. In addition, these carbon nanoelectrodes are suitable for convoluted cell topography imaging because the RG value (ratio of overall probe diameter to active electrode diameter) is typically in the range of 1.5-3.0. We first evaluated the resolution of constant-current mode topography imaging using carbon nanoelectrodes. Next, we performed VSM-SECM measurements to visualize membrane proteins on A431 cells and to detect neurotransmitters from a PC12 cells. We also combined VSM-SECM with surface confocal microscopy to allow simultaneous fluorescence and topographical imaging. VSM-SECM opens up new opportunities in nanoscale chemical mapping at interfaces, and should find wide application in the physical and biological sciences.
Kamourieh S.,Imperial College London |
Braga R.M.,Imperial College London |
Leech R.,Imperial College London |
Newbould R.D.,Imperial College London |
And 3 more authors.
Cerebral Cortex | Year: 2015
Rememberingwhat a speaker said depends on attention. During conversational speech, the emphasis is onworkingmemory, but listening to a lecture encourages episodicmemory encoding.With simultaneous interference from background speech, the need for auditory vigilance increases.We recreated these context-dependent demands on auditory attention in 2ways. The firstwas to require participants to attend to one speaker in either the absence or presence of a distracting background speaker. The second was to alter the task demand, requiring either an immediate or delayed recall of the content of the attended speech. Across 2 fMRI studies, common activated regions associated with segregating attended from unattended speech were the right anterior insula and adjacent frontal operculum (aI/FOp), the left planum temporale, and the precuneus. In contrast, activity in a ventral right frontoparietal systemwas dependent on both the task demand and the presence of a competing speaker. Additionalmultivariate analyses identified other domain-general frontoparietal systems, where activity increased during attentive listening but was modulated little by the need for speech stream segregation in the presence of 2 speakers. These results make predictions about impairments in attentive listening in different communicative contexts following focal or diffuse brain pathology. © The Author 2015. Published by Oxford University Press.
Leiper J.,Hammersmith Hospital Campus |
Nandi M.,King's College London
Nature Reviews Drug Discovery | Year: 2011
Asymmetric dimethylarginine (ADMA) a naturally occurring amino acid that is a product of protein breakdown is released into the cytoplasm following the post-translational methylation of arginine residues within proteins and the subsequent proteolysis of these arginine-methylated proteins. ADMA inhibits all three isoforms of nitric oxide synthase and therefore has the potential to produce diverse biological effects, particularly in the cardiovascular system. In addition to its renal clearance, endogenously produced ADMA is metabolized to L-citrulline and dimethylamine by the dimethylarginine dimethylaminohydrolase (DDAH) enzymes. Pharmacological modification of DDAH has therefore been proposed as a mechanism for manipulating endogenous ADMA concentrations and regulating the production of nitric oxide in situations where alterations in nitric oxide signalling have been shown to contribute to pathophysiology. This Review describes the biology of ADMA and the potential therapeutic utility of manipulating DDAH activity. © 2011 Macmillan Publishers Limited. All rights reserved.
Sharp P.S.,Hammersmith Hospital Campus |
Bye-A-Jee H.,Hammersmith Hospital Campus |
Wells D.J.,Hammersmith Hospital Campus |
Wells D.J.,Royal Veterinary College
Molecular Therapy | Year: 2011
Antisense-induced exon skipping can restore the open reading frame, and thus correct the dystrophin deficiency that causes Duchenne muscular dystrophy (DMD), a lethal muscle wasting condition. Successful proof-of-principle in preclinical models has led to human clinical trials. However, it is still not known what percentage of dystrophin-positive fibers and what level of expression is necessary for functional improvement. This study directly address these key questions in the mdx mouse model of DMD. To achieve a significant variation in dystrophin expression, we locally administered into tibialis anterior muscles various doses of a phosphorodiamidate morpholino oligomer (PMO) designed to skip the mutated exon 23 from the mRNA of murine dystrophin. We found a highly significant correlation between the number of dystrophin-positive fibers and resistance to contraction-induced injury, with a minimum of 20% of dystrophin-positive fibers required for meaningful improvement. Furthermore, our results also indicate that a relatively low level of dystrophin expression in muscle fibers may have significant clinical benefits. In contrast, improvements in muscle force were not correlated with either the number of positive fibers or total dystrophin levels, which highlight the need to conduct appropriate functional assessments in preclinical testing using the mdx mouse. © The American Society of Gene & Cell Therapy.
Hellyer P.J.,Hammersmith Hospital Campus |
Leech R.,Hammersmith Hospital Campus |
Ham T.E.,Hammersmith Hospital Campus |
Bonnelle V.,Hammersmith Hospital Campus |
And 2 more authors.
Annals of Neurology | Year: 2013
Objective: Traumatic brain injury (TBI) often results in traumatic axonal injury (TAI). This can be difficult to identify using conventional imaging. Diffusion tensor imaging (DTI) offers a method of assessing axonal damage in vivo, but has previously mainly been used to investigate groups of patients. Machine learning techniques are increasingly used to improve diagnosis based on complex imaging measures. We investigated whether machine learning applied to DTI data can be used to diagnose white matter damage after TBI and to predict neuropsychological outcome in individual patients. Methods: We trained pattern classifiers to predict the presence of white matter damage in 25 TBI patients with microbleed evidence of TAI compared to neurologically healthy age-matched controls. We then applied these classifiers to 35 additional patients with no conventional imaging evidence of TAI. Finally, we used regression analyses to predict indices of neuropsychological outcome for information processing speed, executive function, and associative memory in a group of 70 heterogeneous patients. Results The classifiers discriminated between patients with microbleeds and age-matched controls with a high degree of accuracy, and outperformed other methods. When the trained classifiers were applied to patients without microbleeds, patients having likely TAI showed evidence of greater cognitive impairment in information processing speed and executive function. The classifiers were also able to predict the extent of impairments in information processing speed and executive function. Interpretation: The work provides a proof of principle that multivariate techniques can be used with DTI to provide diagnostic information about clinically significant TAI. © 2013 American Neurological Association.
Nijjer S.S.,Hammersmith Hospital Campus |
Watson G.,Hammersmith Hospital Campus |
Athanasiou T.,Imperial College London |
Malik I.S.,Hammersmith Hospital Campus
European Heart Journal | Year: 2011
Aims Guidelines suggest that patients should discontinue clopidogrel for 5 days prior to coronary artery bypass grafting (CABG) where possible. Those with acute coronary syndrome (ACS) are at elevated risk of further myocardial infarction (MI) and death without clopidogrel. This meta-analysis Aims to determine the risk of CABG in ACS patients while continuing clopidogrel. Method and results Thirty-four studies with 22 584 patients undergoing CABG were assessed. Patients with recent clopidogrel exposure (CL) were compared with those without recent clopidogrel (NC). Although mortality is increased in CL vs. NC [odds ratio (OR) 1.6, 95 CI 1.301.96, P < 0.00001], it is influenced by the ACS status and case urgency in these mainly non-randomized studies. In ACS patients, there is no significant difference in mortality (OR 1.44, 95 CI 0.972.1, P = 0.07) or in postoperative MI (OR 0.57, 95 CI 0.311.07, P = 0.08) and stroke rates (OR 1.23, 95 CI 0.662.29, P = 0.52). Combined major adverse cardiovascular event (stroke, MI, and death) was not different in the two groups (OR 1.10, 95 CI 0.871.41, P = 0.43). Reoperation rates are elevated on clopidogrel but have reduced over time, and were specifically not different in ACS patients (OR 1.5, 95 CI 0.882.54, P = 0.13). Conclusion Previous studies focused on surrogate endpoints and compared higher risk ACS patients with elective cases. However, many patients have safely undergone CABG on clopidogrel and surgical expertise is growing. Multinational trials are required to fully determine the balance of ischaemia and bleeding. While results are awaited we suggest ACS patients requiring urgent CABG proceed with surgery without delay for a clopidogrel-free period. © 2011 The Author.
Leech R.,Hammersmith Hospital Campus |
Braga R.,Hammersmith Hospital Campus |
Braga R.,Imperial College London |
Sharp D.J.,Hammersmith Hospital Campus
Journal of Neuroscience | Year: 2012
There is considerable uncertainty about the function of the posterior cingulate cortex (PCC). The PCC is a major node within the default mode network (DMN) and has high metabolic activity and dense structural connectivity to widespread brain regions, which suggests it has a role as a cortical hub. The region appears to be involved in internally directed thought, for example, memory recollection. However, recent nonhuman primate work provides evidence for a more active role in the control of cognition, through signaling an environmental change and the need to alter behavior. For an organism to flexibly react to a changing environment, information processed in functionally distinct brain networks needs to be integrated by such a cortical hub. If the PCC is involved in this process, its brain activity should show a complex and dynamic pattern that partially reflects activity in other brain networks. Using fMRI in humans and a multivariate analysis, we demonstrate that the PCC shows this type of complex functional architecture, where echoes of multiple other brain networks are seen in separable yet overlapping subregions. For example, a predominantly ventral region shows strong functional connectivity to the rest of the DMN, whereas two subregions within the dorsal PCC show high connectivity to frontoparietal networks involved in cognitive control. PCC subregions showed distinct patterns of activity modulation during the performance of an attentionally demanding task, suggesting that parts of the dorsal PCC interact with frontoparietal networks to regulate the balance between internally and externally directed cognition. ©2012 the authors.
De Giorgio A.,Hammersmith Hospital Campus |
Castellano L.,Hammersmith Hospital Campus |
Krell J.,Hammersmith Hospital Campus |
Stebbing J.,Hammersmith Hospital Campus
Oncogene | Year: 2014
A molecular environment that promotes vascularization around human carcinomas can materialise rapidly, and has been termed the angiogenic switch. Turning this switch toward a proangiogenic state involves an altered interplay between tumor cells and multiple components of the surrounding stroma. The regulatory landscape of these interactions in cervical cancer is now investigated by Huang et al. in this issue of Oncogene, who demonstrate that the microRNA miR-126 is downregulated during cancer progression, particularly in stromal cells. Such a reduction of miR-126 is shown to free at least one target, the proangiogenic adrenomedullin, from repression, enhancing vascular growth especially at the in situ to invasive carcinoma transition. The study implicates the temporal, spatial and progressive nature of tumor-stroma interactions during carcinogenesis, while in turn suggesting therapeutic strategies. © 2014 Macmillan Publishers Limited.
Reynolds R.,Hammersmith Hospital Campus |
Roncaroli F.,Hammersmith Hospital Campus |
Nicholas R.,Hammersmith Hospital Campus |
Radotra B.,Hammersmith Hospital Campus |
And 2 more authors.
Acta Neuropathologica | Year: 2011
Multiple sclerosis is the major inflammatory condition affecting the central nervous system (CNS) and is characterised by disseminated focal immune-mediated demyelination. Demyelination is accompanied by variable axonal damage and loss and reactive gliosis. It is this pathology that is thought to be responsible for the clinical relapses that often respond well to immunomodulatory therapy. However, the later secondary progressive stage of MS remains largely refractory to treatment and it is widely suggested that accumulating axon loss is responsible for clinical progression. Although initially thought to be a white matter (WM) disease, it is increasingly apparent that extensive pathology is also seen in the grey matter (GM) throughout the CNS. GM pathology is characterised by demyelination in the relative absence of an immune cell infiltrate. Neuronal loss is also seen both in the GM lesions and in unaffected areas of the GM. The slow progressive nature of this later stage combined with the presence of extensive grey matter pathology has led to the suggestion that neurodegeneration might play an increasing role with increasing disease duration. However, there is a paucity of studies that have correlated the pathological features with clinical milestones during secondary progressive MS. Here, we review the contributions that the various types of pathology are likely to make to the increasing neurological deficit in MS. © 2011 Springer-Verlag.
Surani M.A.,University of Cambridge |
Hajkova P.,Hammersmith Hospital Campus
Cold Spring Harbor Symposia on Quantitative Biology | Year: 2010
Primordial germ cells (PGCs), the precursors of sperm and eggs, are the route to totipotency and require establishment of a unique epigenome in this lineage. The genetic program for PGC specification in the mouse also initiates epigenetic reprogramming that continues when PGCs migrate into the developing gonads. Among these later events is active and genomewide DNA demethylation, which is linked to extensive chromatin remodeling. These extensive epigenetic changes erase most, if not all, of the existing epigenetic information, which resets the epigenome for totipotency. Recent evidence suggests that active DNA demethylation involves a base excision repair (BER) pathway. BER is mechanistically linked to DNA demethylation, but what triggers BER is currently under investigation. The methylated cytosine (5mC) could be modified by deamination or to 5hmC, which could induce BER. Detection of Tet1 expression specifically and coincidentally, at the time of BER in PGCs, suggests that conversion of 5mC to 5hmC might be involved, at least in part, during epigenetic reprogramming and DNA demethylation in germ cells. © 2010 Cold Spring Harbor Laboratory Press.