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Search Results: 1 - 10 of 224026 matches for " Ronald C. Petersen "
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Identification of Altered Metabolic Pathways in Plasma and CSF in Mild Cognitive Impairment and Alzheimer’s Disease Using Metabolomics
Eugenia Trushina, Tumpa Dutta, Xuan-Mai T. Persson, Michelle M. Mielke, Ronald C. Petersen
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0063644
Abstract: Alzheimer’s Disease (AD) currently affects more than 5 million Americans, with numbers expected to grow dramatically as the population ages. The pathophysiological changes in AD patients begin decades before the onset of dementia, highlighting the urgent need for the development of early diagnostic methods. Compelling data demonstrate that increased levels of amyloid-beta compromise multiple cellular pathways; thus, the investigation of changes in various cellular networks is essential to advance our understanding of early disease mechanisms and to identify novel therapeutic targets. We applied a liquid chromatography/mass spectrometry-based non-targeted metabolomics approach to determine global metabolic changes in plasma and cerebrospinal fluid (CSF) from the same individuals with different AD severity. Metabolic profiling detected a total of significantly altered 342 plasma and 351 CSF metabolites, of which 22% were identified. Based on the changes of >150 metabolites, we found 23 altered canonical pathways in plasma and 20 in CSF in mild cognitive impairment (MCI) vs. cognitively normal (CN) individuals with a false discovery rate <0.05. The number of affected pathways increased with disease severity in both fluids. Lysine metabolism in plasma and the Krebs cycle in CSF were significantly affected in MCI vs. CN. Cholesterol and sphingolipids transport was altered in both CSF and plasma of AD vs. CN. Other 30 canonical pathways significantly disturbed in MCI and AD patients included energy metabolism, Krebs cycle, mitochondrial function, neurotransmitter and amino acid metabolism, and lipid biosynthesis. Pathways in plasma that discriminated between all groups included polyamine, lysine, tryptophan metabolism, and aminoacyl-tRNA biosynthesis; and in CSF involved cortisone and prostaglandin 2 biosynthesis and metabolism. Our data suggest metabolomics could advance our understanding of the early disease mechanisms shared in progression from CN to MCI and to AD.
New Species of Lentaria (Fungi: Aphyllophorales): redescription and mating systems of L. surculus and L. byssiseda
Petersen,Ronald H;
Revista de Biología Tropical , 2000,
Abstract: the following names are proposed for species of lentaria new to science: l. boletosporioides from new zealand with stout basidiomata and boletoid basidiospores; l. caribbeana from caribbean islands and circum-caribbean landmasses, with large basidiomata and large basidiospores; l. glaucosiccescens from new zealand, with basidiomata turning grey-green upon drying; and l. rionegrensis from argentina, with densely branched, ruddy basidiomata. lentaria javanica nom. nov. is proposed to substitute for clavaria compressa, a later homonym. basidiospore statistics indicate infraspecific differentiation within l. surculus and two morphological variants are described. lentaria surculus and l. byssiseda exhibit tetrapolar mating systems, and the two species are sexually interincompatible.
New Species of Lentaria (Fungi: Aphyllophorales): redescription and mating systems of L. surculus and L. byssiseda
Ronald H Petersen
Revista de Biología Tropical , 2000,
Abstract: The following names are proposed for species of Lentaria new to science: L. boletosporioides from New Zealand with stout basidiomata and boletoid basidiospores; L. caribbeana from Caribbean islands and circum-Caribbean landmasses, with large basidiomata and large basidiospores; L. glaucosiccescens from New Zealand, with basidiomata turning grey-green upon drying; and L. rionegrensis from Argentina, with densely branched, ruddy basidiomata. Lentaria javanica nom. nov. is proposed to substitute for Clavaria compressa, a later homonym. Basidiospore statistics indicate infraspecific differentiation within L. surculus and two morphological variants are described. Lentaria surculus and L. byssiseda exhibit tetrapolar mating systems, and the two species are sexually interincompatible. Se proponen los siguientes nombres para las especies de Lentaria nuevas para la ciencia: L. boletosporioides de Nueva Zelandia, L. caribbeana del Caribe y regiones vecinas, L. glaucosiccescens de Nueva Zelandia, y L rionegrensis de Argentina. Se propone a Lentaria javanica nom. nov., como nombre substituto para Clavaria compressa, un homónimo tardío de su nomenclatura. Se discute el agrupamiento infraespecífico dentro de L. surculus basado en estadísticas de las mediciones de las esporas. Se describen los sistemas reproductivos para L. surculus y L. byssiseda, y se encontró que éstas dos especies son sexualmente interincompatibles.
Non-Stationarity in the “Resting Brain’s” Modular Architecture
David T. Jones, Prashanthi Vemuri, Matthew C. Murphy, Jeffrey L. Gunter, Matthew L. Senjem, Mary M. Machulda, Scott A. Przybelski, Brian E. Gregg, Kejal Kantarci, David S. Knopman, Bradley F. Boeve, Ronald C. Petersen, Clifford R. Jack
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0039731
Abstract: Task-free functional magnetic resonance imaging (TF-fMRI) has great potential for advancing the understanding and treatment of neurologic illness. However, as with all measures of neural activity, variability is a hallmark of intrinsic connectivity networks (ICNs) identified by TF-fMRI. This variability has hampered efforts to define a robust metric of connectivity suitable as a biomarker for neurologic illness. We hypothesized that some of this variability rather than representing noise in the measurement process, is related to a fundamental feature of connectivity within ICNs, which is their non-stationary nature. To test this hypothesis, we used a large (n = 892) population-based sample of older subjects to construct a well characterized atlas of 68 functional regions, which were categorized based on independent component analysis network of origin, anatomical locations, and a functional meta-analysis. These regions were then used to construct dynamic graphical representations of brain connectivity within a sliding time window for each subject. This allowed us to demonstrate the non-stationary nature of the brain’s modular organization and assign each region to a “meta-modular” group. Using this grouping, we then compared dwell time in strong sub-network configurations of the default mode network (DMN) between 28 subjects with Alzheimer’s dementia and 56 cognitively normal elderly subjects matched 1:2 on age, gender, and education. We found that differences in connectivity we and others have previously observed in Alzheimer’s disease can be explained by differences in dwell time in DMN sub-network configurations, rather than steady state connectivity magnitude. DMN dwell time in specific modular configurations may also underlie the TF-fMRI findings that have been described in mild cognitive impairment and cognitively normal subjects who are at risk for Alzheimer’s dementia.
FDG PET and MRI in Logopenic Primary Progressive Aphasia versus Dementia of the Alzheimer’s Type
Ajay Madhavan, Jennifer L. Whitwell, Stephen D. Weigand, Joseph R. Duffy, Edythe A. Strand, Mary M. Machulda, Nirubol Tosakulwong, Matthew L. Senjem, Jeffrey L. Gunter, Val J. Lowe, Ronald C. Petersen, Clifford R. Jack, Keith A. Josephs
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0062471
Abstract: Objectives The logopenic variant of primary progressive aphasia is an atypical clinical variant of Alzheimer’s disease which is typically characterized by left temporoparietal atrophy on magnetic resonance imaging and hypometabolism on F-18 fluorodeoxyglucose positron emission tomography. We aimed to characterize and compare patterns of atrophy and hypometabolism in logopenic primary progressive aphasia, and determine which brain regions and imaging modality best differentiates logopenic primary progressive aphasia from typical dementia of the Alzheimer’s type. Methods A total of 27 logopenic primary progressive aphasia subjects underwent fluorodeoxyglucose positron emission tomography and volumetric magnetic resonance imaging. These subjects were matched to 27 controls and 27 subjects with dementia of the Alzheimer’s type. Patterns of atrophy and hypometabolism were assessed at the voxel and region-level using Statistical Parametric Mapping. Penalized logistic regression analysis was used to determine what combinations of regions best discriminate between groups. Results Atrophy and hypometabolism was observed in lateral temporoparietal and medial parietal lobes, left greater than right, and left frontal lobe in the logopenic group. The logopenic group showed greater left inferior, middle and superior lateral temporal atrophy (inferior p = 0.02; middle p = 0.007, superior p = 0.002) and hypometabolism (inferior p = 0.006, middle p = 0.002, superior p = 0.001), and less right medial temporal atrophy (p = 0.02) and hypometabolism (p<0.001), and right posterior cingulate hypometabolism (p<0.001) than dementia of the Alzheimer’s type. An age-adjusted penalized logistic model incorporating atrophy and hypometabolism achieved excellent discrimination (area under the receiver operator characteristic curve = 0.89) between logopenic and dementia of the Alzheimer’s type subjects, with optimal discrimination achieved using right medial temporal and posterior cingulate hypometabolism, left inferior, middle and superior temporal hypometabolism, and left superior temporal volume. Conclusions Patterns of atrophy and hypometabolism both differ between logopenic primary progressive aphasia and dementia of the Alzheimer’s type and both modalities provide excellent discrimination between groups.
Bisphenyl-Polymer/Carbon-Fiber-Reinforced Composite Compared to Titanium Alloy Bone Implant
Richard C. Petersen
International Journal of Polymer Science , 2011, DOI: 10.1155/2011/168924
Abstract: Aerospace/aeronautical thermoset bisphenyl-polymer/carbon-fiber-reinforced composites are considered as new advanced materials to replace metal bone implants. In addition to well-recognized nonpolar chemistry with related bisphenol-polymer estrogenic factors, carbon-fiber-reinforced composites can offer densities and electrical conductivity/resistivity properties close to bone with strengths much higher than metals on a per-weight basis. In vivo bone-marrow tests with Sprague-Dawley rats revealed far-reaching significant osseoconductivity increases from bisphenyl-polymer/carbon-fiber composites when compared to state-of-the-art titanium-6-4 alloy controls. Midtibial percent bone area measured from the implant surface increased when comparing the titanium alloy to the polymer composite from 10.5% to 41.6% at 0.8?mm, , and 19.3% to 77.7% at 0.1?mm, . Carbon-fiber fragments planned to occur in the test designs, instead of producing an inflammation, stimulated bone formation and increased bone integration to the implant. In addition, low-thermal polymer processing allows incorporation of minerals and pharmaceuticals for future major tissue-engineering potential. 1. Introduction Foremost advancements are expected in stem-cell/osteoprogenitor/osteoblast tissue-engineering for the next generation of bone implants as a result of new materials available from the stealth-electronic technology aeronautical/aerospace era. Through a better understanding of the microstructure and electron-transfer properties for matter, polymer-based fiber-reinforced materials can be bioengineered to provide important new materials for broad significant bone implant applications. In the world of materials, fibers are the strongest and possibly stiffest known forms of a substance matter [1]. When combined into an appropriate matrix like a polymer, much of the fiber mechanical-strength properties can be transferred through the bulk material [1, 2]. Such multiconstituent materials, referred to as composites, have led the way in the aeronautical/aerospace age, primarily as a means to provide stronger lighter structural parts. The basic polymer used for advanced design capability has been a class of thermosetting organic resins that cure by electron free-radical crosslinking [1, 2]. The thermoset resins generally contain similar interconnecting bisphenyl double-aromatic ring molecules that can be reinforced by chemical coupling with fibers for highly developed mechanical properties [1, 2]. The bisphenol-derived polymer function was further identified in 1936 through a pharmaceutical study
Mental health service delivery in South Africa from 2000 to 2010: One step forward, one step back
I Petersen, C Lund
South African Medical Journal , 2011,
Abstract: Objectives. To identify progress and challenges in mental healthcare in South Africa, as well as future mental health services research priorities. Method. A systematic review of mental health services research. Literature searches were conducted in Medline, PsychInfo and Sabinet databases from January 2000 to October 2010 using key phrases. Hand searches of key local journals were also conducted. Of 215 articles retrieved, 92 were included. Data were extracted onto a spreadsheet and analysed thematically. Results. While progress in epidemiological studies has been good, there is a paucity of intervention and economic evaluation studies. The majority of studies reviewed were on the status of mental healthcare services. They indicate some progress in decentralised care for severe mental disorders, but also insufficient resources to adequately support community-based services, resulting in the classic revolving-door phenomenon. Common mental disorders remain largely undetected and untreated in primary healthcare. Cross-cutting issues included the need for promoting culturally congruent services as well as mental health literacy to assist in improving help-seeking behaviour, stigma reduction, and reducing defaulting and human rights abuses. Conclusion. While there has been some progress in the decentralisation of mental health service provision, substantial gaps in service delivery remain. Intervention research is needed to provide evidence of the organisational and human resource mix requirements, as well as cost-effectiveness of a culturally appropriate, task shifting and stepped care approach for severe and common mental disorders at primary healthcare level.
Free-Radical Polymer Science Structural Cancer Model: A Review
Richard C. Petersen
Scientifica , 2013, DOI: 10.1155/2013/143589
Free-Radical Polymer Science Structural Cancer Model: A Review
Richard C. Petersen
Scientifica , 2013, DOI: 10.1155/2013/143589
Abstract: Polymer free-radical lipid alkene chain-growth biological models particularly for hypoxic cellular mitochondrial metabolic waste can be used to better understand abnormal cancer cell morphology and invasive metastasis. Without oxygen as the final electron acceptor for mitochondrial energy synthesis, protons cannot combine to form water and instead mitochondria produce free radicals and acid during hypoxia. Nonuniform bond-length shrinkage of membranes related to erratic free-radical covalent crosslinking can explain cancer-cell pleomorphism with epithelial-mesenchymal transition for irregular membrane borders that “ruffle” and warp over stiff underlying actin fibers. Further, mitochondrial hypoxic conditions produce acid that can cause molecular degradation. Subsequent low pH-activated enzymes then provide paths for invasive cell movement through tissue and eventually blood-born metastasis. Although free-radical crosslinking creates irregularly shaped membranes with structural actin-polymerized fiber extensions as filopodia and lamellipodia, due to rapid cell division the overall cell modulus (approximately stiffness) is lower than normal cells. When combined with low pH-activated enzymes and lower modulus cells, smaller cancer stem cells subsequently have a large advantage to follow molecular destructive pathways and leave the central tumor. In addition, forward structural spike-like lamellipodia protrusions can leverage to force lower-modulus cancer cells through narrow openings. By squeezing and deforming even smaller to allow for easier movement through difficult passageways, cancer cells can travel into adjacent tissues or possibly metastasize through the blood to new tissue. 1. Introduction Cancer Fundamentals. Cancer is a pathological condition related to malignant uncontrolled rapid cell growth proliferation, invasive cell movement into adjacent tissues, and occasional metastatic spread through blood and lymph to more distant locations [1–4]. Conversely, benign tumors represent uncontrolled cell growth that does not invade other tissues [1–4]. Cancers are the result of progressive accumulations in genetic mutations through cell interactions with carcinogens such as tobacco, sunlight, radiation, infectious microbes, or certain chemicals/material [1–4]. Some genetic changes can be added by being passed along from one generation to another to increase cancer risk [1–4]. Although normal cells have limits to replication or the number of cell divisions to control growth by apoptosis cell death when necessary with a cascade of caspase enzymes, cancer
Measurement of the W mass with the ATLAS detector
Troels C. Petersen
Physics , 2008,
Abstract: We investigate the posibility of improving the W mass measurement at ATLAS. Given the high statistics of both W and Z bosons expected at the LHC, we estimate that a precision of 7 MeV per channel can be reached with 10 fb-1 of data.
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