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Search Results: 1 - 10 of 462132 matches for " A. Erickson "
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Paradoxos de Decis o Social
Genn W. Erickson,John A. Fossa
Princípios : Revista de Filosofia , 1996,
Sobre a Classifica o de Triangulos Pitagóricos
John A. Fossa,Glenn W. Erickson
Princípios : Revista de Filosofia , 2001,
Uma Heurística Plat nica para Termos Pitagóricos
John A. Fossa,Glenn W. Erickson
Princípios : Revista de Filosofia , 1997,
Brain microvascular pericytes are immunoactive in culture: cytokine, chemokine, nitric oxide, and LRP-1 expression in response to lipopolysaccharide
Andrej Kovac, Michelle A Erickson, William A Banks
Journal of Neuroinflammation , 2011, DOI: 10.1186/1742-2094-8-139
Abstract: Supernatants were collected from primary cultures of mouse brain pericytes. Release of nitric oxide (NO) was measured by the Griess reaction and the level of S-nitrosylation of pericyte proteins measured with a modified "biotin-switch" method. Specific mitogen-activated protein kinase (MAPK) pathway inhibitors were used to determine involvement of these pathways on NO production. Cytokines and chemokines were analyzed by multianalyte technology. The expression of both subunits of LRP-1 was analyzed by western blot.Lipopolysaccharide (LPS) induced release of NO by pericytes in a dose-dependent manner that was mediated through MAPK pathways. Nitrative stress resulted in S-nitrosylation of cellular proteins. Eighteen of twenty-three cytokines measured were released constitutively by pericytes or with stimulation by LPS, including interleukin (IL)-12, IL-13, IL-9, IL-10, granulocyte-colony stimulating factor, granulocyte macrophage-colony stimulating factor, eotaxin, chemokine (C-C motif) ligand (CCL)-3, and CCL-4. Pericyte expressions of both subunits of LRP-1 were upregulated by LPS.Our results show that cultured mouse brain microvascular pericytes secrete cytokines, chemokines, and nitric oxide and respond to the innate immune system stimulator LPS. These immune properties of pericytes are likely important in their communication within the neurovascular unit and provide a mechanism by which they participate in neuroinflammatory processes in brain infections and neurodegenerative diseases.The blood-brain barrier (BBB) is a selective barrier that is created by the endothelial cells in cerebral microvessels. Endothelial cells and supporting cells such as astrocytes, pericytes, neurons, and perivascular microglia are organized together to form the "neurovascular unit" which is essential for induction, function, and support of the BBB [1]. In contrast to the considerable knowledge characterizing the crosstalk among brain endothelial cells, astrocytes, and microglia within
Lifespan Psychomotor Behaviour Profiles of Multigenerational Prenatal Stress and Artificial Food Dye Effects in Rats
Zachary T. Erickson, Erin A. Falkenberg, Gerlinde A. S. Metz
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0092132
Abstract: The consumption of artificial food dye (AFD) during childhood and adolescence has been linked to behavioural changes, such as hyperactivity. It is possible that the vulnerability to AFDs is modified by prenatal stress. Common consequences of prenatal stress include hyperactivity, thus potentially leading to synergistic actions with AFDs. Here, we investigated the compounding effect of multigenerational prenatal stress (MPS) and AFD consumption on the development of hyperactivity and anxiety-related behaviours across the lifespan in male rats. MPS treatment involved a family history of four consecutive generations of prenatal stress (F4 generation). AFD treatment included a 4%-concentration of FD&C Red 40, FD&C Yellow 5, FD&C Yellow 6, and FD&C Blue 1 in the drinking water from postnatal days 22 to 50 to resemble juvenile and adolescent dietary exposure. Using several exploration tasks, animals were tested in motor activity and anxiety-like behaviours from adolescence to 13 months of age. MPS resulted in hyperactivity both early (50 days) and later in life (13 months), with normalized activity patterns at reproductive age. AFD consumption resulted in hyperactivity during consumption, which subsided following termination of treatment. Notably, both MPS and AFD promoted risk-taking behaviour in young adults (3 months). There were few synergistic effects between MPS and AFD in this study. The findings suggest that AFDs exert the most noticeable effects at the time of exposure. MPS, however, results in a characteristic lifespan profile of behavioural changes, indicating that development and aging represent particularly vulnerable periods in life during which a family history of prenatal stress may precipitate.
Age-Related Decline in Controlled Retrieval: The Role of the PFC and Sleep
Kristine A. Wilckens,Kirk I. Erickson,Mark E. Wheeler
Neural Plasticity , 2012, DOI: 10.1155/2012/624795
Abstract: Age-related cognitive impairments often include difficulty retrieving memories, particularly those that rely on executive control. In this paper we discuss the influence of the prefrontal cortex on memory retrieval, and the specific memory processes associated with the prefrontal cortex that decline in late adulthood. We conclude that preretrieval processes associated with preparation to make a memory judgment are impaired, leading to greater reliance on postretrieval processes. This is consistent with the view that impairments in executive control significantly contribute to deficits in controlled retrieval. Finally, we discuss age-related changes in sleep as a potential mechanism that contributes to deficiencies in executive control that are important for efficient retrieval. The sleep literature points to the importance of slow-wave sleep in restoration of prefrontal cortex function. Given that slow-wave sleep significantly declines with age, we hypothesize that age-related changes in slow-wave sleep could mediate age-related decline in executive control, manifesting a robust deficit in controlled memory retrieval processes. Interventions, like physical activity, that improve sleep could be effective methods to enhance controlled memory processes in late life. 1. Introduction Age-related cognitive impairments often include decline in executive control critical for strategic controlled memory retrieval [1–4]. Volumetric studies have suggested that atrophy of the prefrontal cortex (PFC) mediates age-related decline in executive control [5, 6]. Impairments in executive control include difficulties selecting relevant and inhibiting irrelevant information and actions, and difficulties monitoring and updating information [7, 8]. Further, white matter in older adults is particularly compromised in anterior brain regions. This has been shown with white matter lesions [9] as well as white matter integrity assessed using diffusion tensor imaging (DTI) [10–12]. Such white matter breakdown disrupts the connectivity between frontal and other cortical regions, ultimately affecting executive control. These PFC changes tend to manifest themselves in a range of cognitive tasks including memory retrieval [3, 13, 14]. Given that decline in memory can be particularly debilitating in older adults, determining factors that contribute to PFC decline is of utmost importance. The prevalence of sleep disruption in older adults [15–17] and its negative impact on cognition [18, 19] suggest that sleep may play an important role in the extent to which older adults exhibit decline
BtubA-BtubB Heterodimer Is an Essential Intermediate in Protofilament Assembly
Christopher A. Sontag, Harvey Sage, Harold P. Erickson
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0007253
Abstract: Background BtubA and BtubB are two tubulin-like genes found in the bacterium Prosthecobacter. Our work and a previous crystal structure suggest that BtubB corresponds to α?tubulin and BtubA to β?tubulin. A 1:1 mixture of the two proteins assembles into tubulin-like protofilaments, which further aggregate into pairs and bundles. The proteins also form a BtubA/B heterodimer, which appears to be a repeating subunit in the protofilament. Methodology/Principal Findings We have designed point mutations to disrupt the longitudinal interfaces bonding subunits into protofilaments. The mutants are in two classes, within dimers and between dimers. We have characterized one mutant of each class for BtubA and BtubB. When mixed 1:1 with a wild type partner, none of the mutants were capable of assembly. An excess of between-dimer mutants could depolymerize preformed wild type polymers, while within-dimer mutants had no activity. Conclusions An essential first step in assembly of BtubA + BtubB is formation of a heterodimer. An excess of between-dimer mutants depolymerize wild type BtubA/B by sequestering the partner wild type subunit into inactive dimers. Within-dimer mutants cannot form dimers and have no activity.
Microfabricated Physical Spatial Gradients for Investigating Cell Migration and Invasion Dynamics
Michael Mak,Cynthia A. Reinhart-King,David Erickson
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0020825
Abstract: We devise a novel assay that introduces micro-architectures into highly confining microchannels to probe the decision making processes of migrating cells. The conditions are meant to mimic the tight spaces in the physiological environment that cancer cells encounter during metastasis within the matrix dense stroma and during intravasation and extravasation through the vascular wall. In this study we use the assay to investigate the relative probabilities of a cell 1) permeating and 2) repolarizing (turning around) when it migrates into a spatially confining region. We observe the existence of both states even within a single cell line, indicating phenotypic heterogeneity in cell migration invasiveness and persistence. We also show that varying the spatial gradient of the taper can induce behavioral changes in cells, and different cell types respond differently to spatial changes. Particularly, for bovine aortic endothelial cells (BAECs), higher spatial gradients induce more cells to permeate (60%) than lower gradients (12%). Furthermore, highly metastatic breast cancer cells (MDA-MB-231) demonstrate a more invasive and permeative nature (87%) than non-metastatic breast epithelial cells (MCF-10A) (25%). We examine the migration dynamics of cells in the tapered region and derive characteristic constants that quantify this transition process. Our data indicate that cell response to physical spatial gradients is both cell-type specific and heterogeneous within a cell population, analogous to the behaviors reported to occur during tumor progression. Incorporation of micro-architectures in confined channels enables the probing of migration behaviors specific to defined geometries that mimic in vivo microenvironments.
Cheek swabs, SNP chips, and CNVs: Assessing the quality of copy number variant calls generated with subject-collected mail-in buccal brush DNA samples on a high-density genotyping microarray
Stephen W Erickson, Stewart L MacLeod, Charlotte A Hobbs
BMC Medical Genetics , 2012, DOI: 10.1186/1471-2350-13-51
Abstract: To demonstrate the quality of CNV calls generated from DNA extracted from buccal samples, compared to calls generated from blood samples, we evaluated the concordance of calls from individuals who provided both sample types. The Illumina Human660W-Quad BeadChip was used to determine SNPs and CNVs of 39 Arkansas participants in the National Birth Defects Prevention Study (NBDPS), including 16 mother-infant dyads, who provided both whole blood and buccal brush DNA samples.We observed a 99.9% concordance rate of SNP calls in the 39 blood–buccal pairs. From the same dataset, we performed a similar analysis of CNVs. Each of the 78 samples was independently segmented into regions of like copy number using the Optimal Segmentation algorithm of Golden Helix SNP & Variation Suite 7.Across 640,663 loci on 22 autosomal chromosomes, segment-mean log R ratios had an average correlation of 0.899 between blood-buccal pairs of samples from the same individual, while the average correlation between all possible blood-buccal pairs of samples from unrelated individuals was 0.318. An independent analysis using the QuantiSNP algorithm produced average correlations of 0.943 between blood-buccal pairs from the same individual versus 0.332 between samples from unrelated individuals.Segment-mean log R ratios had an average correlation of 0.539 between mother-offspring dyads of buccal samples, which was not statistically significantly different than the average correlation of 0.526 between mother-offspring dyads of blood samples (p=0.302).We observed performance from the subject-collected mail-in buccal brush samples comparable to that of blood. These results show that such DNA samples can be used for genome-wide scans of both SNPs and CNVs, and that high rates of CNV concordance were achieved whether using a change-point-based algorithm or one based on a hidden Markov model (HMM).
Full-thickness abdominal skin graft for long-segment urethral stricture reconstruction
Meeks, Joshua J.;Erickson, Bradley A.;Gonzalez, Chris M.;
International braz j urol , 2008, DOI: 10.1590/S1677-55382008000500009
Abstract: multiple tissue sources have been used for urethral reconstruction in adults. patients with lichen sclerosis (ls), long segment strictures, or prior oral graft use have less available tissue for urethroplasty. we describe a technique for the use of a full-thickness skin graft of hairless abdominal skin for long segment urethroplasty.
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