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Search Results: 1 - 10 of 133077 matches for " David W. Carmichael "
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Network connectivity in epilepsy: Resting state-fMRI and EEG-fMRI contributions
Maria Centeno,David W. Carmichael
Frontiers in Neurology , 2014, DOI: 10.3389/fneur.2014.00093
Abstract: There is a growing body of evidence pointing towards large scale networks underlying the core phenomena in epilepsy, from seizure generation to cognitive dysfunction or response to treatment. The investigation of networks in epilepsy has become a key concept to unlock a deeper understanding of the disease. Functional imaging can provide valuable information to characterise network dysfunction; in particular resting state fMRI (RS-fMRI) which is increasingly being applied to study brain networks in a number of diseases. In patients with epilepsy, network connectivity derived from RS- fMRI has found connectivity abnormalities in a number of networks; these include the epileptogenic, cognitive and sensory processing networks. However, in majority of these studies, the effect of epileptic transients in the connectivity of networks has been neglected. EEG-fMRI has frequently shown networks related to epileptic transients that in many cases are concordant with the abnormalities shown in RS studies. This points towards a relevant role of epileptic transients in the network abnormalities detected in RS-fMRI studies. In this review, we summarize the network abnormalities reported by these two techniques side by side, provide evidence of their overlapping findings, and discuss their significance in the context of the methodology of each technique. A number of clinically relevant factors that have been associated with connectivity changes are in turn associated with changes in the frequency of epileptic transients. These factors include different aspects of epilepsy ranging from treatment effects, cognitive processes or transition between different alertness states (i.e. awake-sleep transition). For RS-fMRI to become a more effective tool to investigate clinically relevant aspects of epilepsy it is necessary to understand connectivity changes associated with epileptic transients, those associated with other clinically relevant factors and the interaction between them wh
Relating resting-state fMRI and EEG whole-brain connectomes across frequency bands
Fani Deligianni,Maria Centeno,David W. Carmichael,Jonathan D. Clayden
Frontiers in Neuroscience , 2014, DOI: 10.3389/fnins.2014.00258
Abstract: Whole brain functional connectomes hold promise for understanding human brain activity across a range of cognitive, developmental and pathological states. So called resting-state (rs) functional MRI studies have contributed to the brain being considered at a macroscopic scale as a set of interacting regions. Interactions are defined as correlation-based signal measurements driven by blood oxygenation level dependent (BOLD) contrast. Understanding the neurophysiological basis of these measurements is important in conveying useful information about brain function. Local coupling between BOLD fMRI and neurophysiological measurements is relatively well defined, with evidence that gamma (range) frequency EEG signals are the closest correlate of BOLD fMRI changes during cognitive processing. However, it is less clear how whole-brain network interactions relate during rest where lower frequency signals have been suggested to play a key role. Simultaneous EEG-fMRI offers the opportunity to observe brain network dynamics with high spatio-temporal resolution. We utilize these measurements to compare the connectomes derived from rs-fMRI and EEG band limited power (BLP). Merging this multi-modal information requires the development of an appropriate statistical framework. We relate the covariance matrices of the Hilbert envelope of the source localized EEG signal across bands to the covariance matrices derived from rs-fMRI with the means of statistical prediction based on sparse Canonical Correlation Analysis (sCCA). Subsequently, we identify the most prominent connections that contribute to this relationship. We compare whole-brain functional connectomes based on their geodesic distance to reliably estimate the performance of the prediction. The performance of predicting fMRI from EEG connectomes is considerably better than predicting EEG from fMRI across all bands, whereas the connectomes derived in low frequency EEG bands resemble best rs-fMRI connectivity.
Correlation Between Segment Length and Spine Counts in Two SpiderSpecies of Araneus (Araneae: Araneidae)
L. David Carmichael
Psyche , 1973, DOI: 10.1155/1973/47592
Causal Hierarchy within the Thalamo-Cortical Network in Spike and Wave Discharges
Anna E. Vaudano, Helmut Laufs, Stefan J. Kiebel, David W. Carmichael, Khalid Hamandi, Maxime Guye, Rachel Thornton, Roman Rodionov, Karl J. Friston, John S. Duncan, Louis Lemieux
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0006475
Abstract: Background Generalised spike wave (GSW) discharges are the electroencephalographic (EEG) hallmark of absence seizures, clinically characterised by a transitory interruption of ongoing activities and impaired consciousness, occurring during states of reduced awareness. Several theories have been proposed to explain the pathophysiology of GSW discharges and the role of thalamus and cortex as generators. In this work we extend the existing theories by hypothesizing a role for the precuneus, a brain region neglected in previous works on GSW generation but already known to be linked to consciousness and awareness. We analysed fMRI data using dynamic causal modelling (DCM) to investigate the effective connectivity between precuneus, thalamus and prefrontal cortex in patients with GSW discharges. Methodology and Principal Findings We analysed fMRI data from seven patients affected by Idiopathic Generalized Epilepsy (IGE) with frequent GSW discharges and significant GSW-correlated haemodynamic signal changes in the thalamus, the prefrontal cortex and the precuneus. Using DCM we assessed their effective connectivity, i.e. which region drives another region. Three dynamic causal models were constructed: GSW was modelled as autonomous input to the thalamus (model A), ventromedial prefrontal cortex (model B), and precuneus (model C). Bayesian model comparison revealed Model C (GSW as autonomous input to precuneus), to be the best in 5 patients while model A prevailed in two cases. At the group level model C dominated and at the population-level the p value of model C was ~1. Conclusion Our results provide strong evidence that activity in the precuneus gates GSW discharges in the thalamo-(fronto) cortical network. This study is the first demonstration of a causal link between haemodynamic changes in the precuneus - an index of awareness - and the occurrence of pathological discharges in epilepsy.
Cyanobacteria toxins in the Salton Sea
Wayne W Carmichael, RenHui Li
Aquatic Biosystems , 2006, DOI: 10.1186/1746-1448-2-5
Abstract: From November 1999 to April 2001, 247 water and sediment samples were received for phytoplankton identification and cyanotoxin analyses. Immunoassay (ELISA) screening of these samples found that eighty five percent of all water samples contained low but detectable levels of the potent cyclic peptide liver toxin called microcystins. Isolation and identification of cyanobacteria isolates showed that the picoplanktonic Synechococcus and the benthic filamentous Oscillatoria were dominant. Both organisms were found to produce microcystins dominated by microcystin-LR and YR. A laboratory strain of Synechococcus was identified by PCR as being closest to known marine forms of this genus. Analyses of affected grebe livers found microcystins at levels that may account for some of the acute mortalities.The production of microcystins by a marine Synechococcus indicates that microcystins may be a more common occurrence in marine environments – a finding not recognized before this work. Further research should be done to define the distribution of microcystin producing marine cyanobacteria and to determine exposure/response effects of microcystins and possibly other cyanotoxins in the Salton Sea. Future efforts to reduce avian mortalities and remediate the Salton Sea should evaluate vectors by which microcystins enter avian species and ways to control and mitigate toxic cyanobacteria waterblooms at the Salton Sea.Beginning in the 1990's, massive avian and fish epornitics have occurred in the Salton Sea and over 200,000 eared grebes have died [1]. The largest single epizootic occurred in 1992 when an estimated 155,000 birds, primarily eared grebes (Podiceps nigricollis), died from an undiagnosed cause. The cause of these massive grebe epornitics remains unknown, although several diseases such as avian botulism and avian cholera have been diagnosed [2]. Algal biotoxins, especially those produced by dinoflagellates, have also been listed as a possible contributing cause [3], but non
Design and implementation of a generalized laboratory data model
Michael C Wendl, Scott Smith, Craig S Pohl, David J Dooling, Asif T Chinwalla, Kevin Crouse, Todd Hepler, Shin Leong, Lynn Carmichael, Mike Nhan, Benjamin J Oberkfell, Elaine R Mardis, LaDeana W Hillier, Richard K Wilson
BMC Bioinformatics , 2007, DOI: 10.1186/1471-2105-8-362
Abstract: We describe a general modeling framework for laboratory data and its implementation as an information management system. The model utilizes several abstraction techniques, focusing especially on the concepts of inheritance and meta-data. Traditional approaches commingle event-oriented data with regular entity data in ad hoc ways. Instead, we define distinct regular entity and event schemas, but fully integrate these via a standardized interface. The design allows straightforward definition of a "processing pipeline" as a sequence of events, obviating the need for separate workflow management systems. A layer above the event-oriented schema integrates events into a workflow by defining "processing directives", which act as automated project managers of items in the system. Directives can be added or modified in an almost trivial fashion, i.e., without the need for schema modification or re-certification of applications. Association between regular entities and events is managed via simple "many-to-many" relationships. We describe the programming interface, as well as techniques for handling input/output, process control, and state transitions.The implementation described here has served as the Washington University Genome Sequencing Center's primary information system for several years. It handles all transactions underlying a throughput rate of about 9 million sequencing reactions of various kinds per month and has handily weathered a number of major pipeline reconfigurations. The basic data model can be readily adapted to other high-volume processing environments.Over the past several decades, many of the biomedical sciences have been transformed into what might be called "high-throughput" areas of study, e.g., DNA mapping and sequencing, gene expression, and proteomics. In a number of cases, the rate at which data can now be generated has increased by several orders of magnitude. This scale-up has contributed to the rise of "big biology" projects of the type that
Overheating and Hospitals - What do we know?
Catriona Carmichael,Graham Bickler,Sari Kovats,David Pencheon
Journal of Hospital Administration , 2012, DOI: 10.5430/jha.v2n1p1
Abstract: Heatwaves have well described impacts on human health and wellbeing. Heatwaves also have impacts on hospitals. Patients, visitors, equipment, medication and IT systems have all been affected or compromised during episodes of extreme heat. High indoor temperatures are also of concern for the comfort, efficiency, and occupational health of staff. The Heatwave Plan for England describes actions to prepare for and be taken in the event of a heatwave. Advice for a hospital is so far limited and not evidence based. In this paper, we review what is currently known about the impacts of heatwaves on hospitals and identify several important information gaps. Improved responses to hot weather could improve patient care and staff comfort. If seen as part of a wider approach to sustainability, proper planning will also enable hospitals to reduce health care costs, increase efficiency and meet carbon reduction targets.
A Putative Gene Cluster from a Lyngbya wollei Bloom that Encodes Paralytic Shellfish Toxin Biosynthesis
Troco K. Mihali,Wayne W. Carmichael,Brett A. Neilan
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0014657
Abstract: Saxitoxin and its analogs cause the paralytic shellfish-poisoning syndrome, adversely affecting human health and coastal shellfish industries worldwide. Here we report the isolation, sequencing, annotation, and predicted pathway of the saxitoxin biosynthetic gene cluster in the cyanobacterium Lyngbya wollei. The gene cluster spans 36 kb and encodes enzymes for the biosynthesis and export of the toxins. The Lyngbya wollei saxitoxin gene cluster differs from previously identified saxitoxin clusters as it contains genes that are unique to this cluster, whereby the carbamoyltransferase is truncated and replaced by an acyltransferase, explaining the unique toxin profile presented by Lyngbya wollei. These findings will enable the creation of toxin probes, for water monitoring purposes, as well as proof-of-concept for the combinatorial biosynthesis of these natural occurring alkaloids for the production of novel, biologically active compounds.
Lanreotide depot deep subcutaneous injection: a new method of delivery and its associated benefits
Carmichael JD
Patient Preference and Adherence , 2012, DOI: http://dx.doi.org/10.2147/PPA.S20783
Abstract: nreotide depot deep subcutaneous injection: a new method of delivery and its associated benefits Review (2074) Total Article Views Authors: Carmichael JD Published Date January 2012 Volume 2012:6 Pages 73 - 82 DOI: http://dx.doi.org/10.2147/PPA.S20783 Received: 27 October 2011 Accepted: 24 November 2011 Published: 18 January 2012 John D Carmichael Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, CA, USA Abstract: Acromegaly is a rare disease characterized by excessive growth hormone secretion, usually from a pituitary tumor. Treatment options include surgery, medical therapy, and in some cases, radiation therapy. Current medical therapy consists of treatment with somatostatin analog medications or a growth hormone receptor antagonist. There are two somatostatin analogs currently in use, octreotide and lanreotide. Both are supplied in long-acting formulations and are of comparable biochemical efficacy. Lanreotide is supplied in a prefilled syringe and is injected into deep subcutaneous tissue. Studies have been conducted to assess the efficacy of self- or partner administration, and have demonstrated that injection of lanreotide can be accomplished reliably and safely outside a physician's office. For patients who have achieved biochemical control with lanreotide, the FDA has recently approved an extended dosing interval. Selected patients may be able to receive the medication less frequently with injections of 120 mg administered every 6 or 8 weeks. This review focuses on the use of lanreotide in the treatment of acromegaly, the safety and efficacy of the drug, and the benefits afforded to patients because of unique aspects of the delivery of lanreotide.
XML und qualitative Datenanalyse Extensible Markup Language and Qualitative Data Analysis Extensible Markup Language" y análisis de datos cualitativos
Patrick Carmichael
Forum : Qualitative Social Research , 2002,
Abstract: Die zunehmende Popularit t von XML (Extensible Markup Language) und die Verfügbarkeit von Software, die XML-Dokumente lesen und editieren kann, bietet die M glichkeit, Instrumente der qualitativen Datenanalyse in "groupware"-Anwendungen wie gemeinsam benutzte Arbeitsbereiche oder Datenbanken einzubinden, welche dann mittels Netzwerken innerhalb von Organisationen oder über das Internet zug nglich gemacht werden k nnen. In der Vergangenheit waren kollaborative Systeme im Allgemeinen darauf ausgerichtet, Dokumente als Ganzes zu apportieren und zu pr sentieren. Es war zwar prinzipiell m glich, innerhalb dieser Systeme Dokumente zu annotieren und zu diskutieren, aber die M glichkeiten einer "Bleistift-Level"-Analyse (wie in den meisten CAQDAS Programmen üblich) war nicht gegeben. XML kann, wenn mit einer Skriptsprache wie Perl kombiniert, dazu verwendet werden, einfache QDA-Funktionen wie das Retrieval von Textsegmenten auf der Basis von Zeichenketten und Schlüsselw rtern, das Verknüpfen von Memos zu Textfragmenten und die Generierung von überblicksdaten durchzuführen – und dies mittels eines Standard-Webbrowsers. URN: urn:nbn:de:0114-fqs0202134 The increasing popularity of Extensible Markup Language (XML) and the availability of software capable of reading and editing XML documents present opportunities for Qualitative Data Analysis (QDA) facilities to be incorporated into "groupware" applications such as collaborative workspaces and "document bases", and to be made available across networks both within organisations and across the Internet. Collaborative systems have, in the past, characteristically, been geared to retrieve and present whole documents, and while annotation and discussion of documents has been possible within such systems, the "pencil-level" analysis commonplace in CAQDAS (Computer Assisted Qualitative Data Analysis Software) has been lacking. XML, when combined with a scripting language such as Perl, can be used to offer basic QDA functionality—retrieval by text and codes, attachment of memos to text fragments, and the generation of summary data—via a standard web-browser. URN: urn:nbn:de:0114-fqs0202134 La creciente popularidad del Extensible Markup Language (XML) y la disponibilidad de programas capaces de leer y editar documentos XML, ofrece oportunidades para que las facilidades del Análisis de Datos Cualitativos (ADC) sean incorporadas en las aplicaciones de dispositivos para grupos tales como los espacios de trabajo colaborativo y las "bases de documentos", y para hacerlas disponibles en las redes de trabajo de las organizaciones y
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