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Search Results: 1 - 10 of 208539 matches for " Bangyan L. Stiles "
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Short Term Feeding of a High Fat Diet Exerts an Additive Effect on Hepatocellular Damage and Steatosis in Liver-Specific PTEN Knockout Mice
Colin T. Shearn, Kelly E. Mercer, David J. Orlicky, Leah Hennings, Rebecca L. Smathers-McCullough, Bangyan L. Stiles, Martin J. J. Ronis, Dennis R. Petersen
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0096553
Abstract: Background Hepatospecific deletion of PTEN results in constitutive activation of Akt and increased lipogenesis. In mice, the addition of a high fat diet (HFD) downregulates lipogenesis. The aim of this study was to determine the effects of a HFD on hepatocellular damage induced by deletion of PTEN. Methods 12 Week old male flox/flox hepatospecific PTEN mice (PTENf/f) or Alb-Cre controls were fed a HFD composed of 45% fat-derived calories (from corn oil) or a normal chow. Animals were then analyzed for hepatocellular damage, oxidative stress and expression of enzymes involved in fatty acid metabolism. Results In the Alb-Cre animals, the addition of a HFD resulted in a significant increase in liver triglycerides and altered REDOX capacity as evidenced by increased GPX activity, decreased GST activity and decreased hepatic concentrations of GSSG. In addition, SCD2, ACLY and FASN were all downregulated by the addition of HFD. Furthermore, expression of PPARα and PPARα-dependent proteins Cyp4a and ACSL1 were upregulated. In the PTENf/f mice, HFD resulted in significant increased in ALT, serum triglycerides and decreased REDOX capacity. Although expression of fatty acid synthetic enzymes was elevated in the chow fed PTENf/f group, the addition of HFD resulted in SCD2, ACLY and FASN downregulation. Compared to the Alb-Cre HFD group, expression of PGC1α, PPARα and its downstream targets ACSL and Cyp4a were upregulated in PTENf/f mice. Conclusions These data suggest that during conditions of constitutive Akt activation and increased steatosis, the addition of a HFD enhances hepatocellular damage due to increased CD36 expression and altered REDOX status. In addition, this work indicates HFD-induced hepatocellular damage occurs in part, independently of Akt signaling.
Maf1 Is a Novel Target of PTEN and PI3K Signaling That Negatively Regulates Oncogenesis and Lipid Metabolism
Beth M. Palian equal contributor,Aarti D. Rohira equal contributor,Sandra A. S. Johnson equal contributor,Lina He,Ni Zheng,Louis Dubeau,Bangyan L. Stiles,Deborah L. Johnson
PLOS Genetics , 2014, DOI: doi/10.1371/journal.pgen.1004789
Abstract: Maf1 was initially identified as a transcriptional repressor of RNA pol III-transcribed genes, yet little is known about its other potential target genes or its biological function. Here, we show that Maf1 is a key downstream target of PTEN that drives both its tumor suppressor and metabolic functions. Maf1 expression is diminished with loss of PTEN in both mouse models and human cancers. Consistent with its role as a tumor suppressor, Maf1 reduces anchorage-independent growth and tumor formation in mice. PTEN-mediated changes in Maf1 expression are mediated by PTEN acting on PI3K/AKT/FoxO1 signaling, revealing a new pathway that regulates RNA pol III-dependent genes. This regulatory event is biologically relevant as diet-induced PI3K activation reduces Maf1 expression in mouse liver. We further identify lipogenic enzymes as a new class of Maf1-regulated genes whereby Maf1 occupancy at the FASN promoter opposes SREBP1c-mediated transcription activation. Consistent with these findings, Maf1 inhibits intracellular lipid accumulation and increasing Maf1 expression in mouse liver abrogates diet-mediated induction of lipogenic enzymes and triglycerides. Together, these results establish a new biological role for Maf1 as a downstream effector of PTEN/PI3K signaling and reveal that Maf1 is a key element by which this pathway co-regulates lipid metabolism and oncogenesis.
Robust Spatial Filters on Three-Class Motor Imagery EEG Data Using Independent Component Analysis  [PDF]
Bangyan Zhou, Xiaopei Wu, Lei Zhang, Zhao Lv, Xiaojing Guo
Journal of Biosciences and Medicines (JBM) , 2014, DOI: 10.4236/jbm.2014.22007

Independent Component Analysis (ICA) was often used to separate movement related independent components (MRICs) from Electroencephalogram (EEG) data. However, to obtain robust spatial filters, complex characteristic features, which were manually selected in most cases, have been commonly used. This study proposed a new simple algorithm to extract MRICs automatically, which just utilized the spatial distribution pattern of ICs. The main goal of this study was to show the relationship between spatial filters performance and designing samples. The EEG data which contain mixed brain states (preparing, motor imagery and rest) were used to design spatial filters. Meanwhile, the single class data was also used to calculate spatial filters to assess whether the MRICs extracted on different class motor imagery spatial filters are similar. Furthermore, the spatial filters constructed on one subject’s EEG data were applied to extract the others’ MRICs. Finally, the different spatial filters were then applied to single-trial EEG to extract MRICs, and Support Vector Machine (SVM) classifiers were used to discriminate left handright-hand and foot imagery movements of BCI Competition IV Dataset 2a, which recorded four motor imagery data of nine subjects. The results suggested that any segment of finite motor imagery EEG samples could be used to design ICA spatial filters, and the extracted MRICs are consistent if the position of electrodes are the same, which confirmed the robustness and practicality of ICA used in the motor imagery Brain Computer Interfaces (MI-BCI) systems.

Cognitive Control Functions in Unipolar Major Depression with and without Co-Morbid Anxiety Disorder
Pia Lyche,Rune Jonassen,Tore C. Stiles,P?l Ulleberg,Nils I. Landr?
Frontiers in Psychiatry , 2010, DOI: 10.3389/fpsyt.2010.00149
Abstract: Background: Impaired cognitive control functions have been demonstrated in both major depression (MDD) and anxiety disorder (A), but few studies have systematically examined the impact of MDD with co-morbid A (MDDA), which is the main aim of this study. Method: We compared patients with MDD with (MDDA; n = 24) and without co-morbid A (n = 37) to a group of healthy controls (HC; n = 92) on three subtests from the Cambridge Neuropsychological Test Automated Battery; intra–extra dimensional, stop signal task, and spatial working memory. These tasks correspond to a theoretical model consisting of three separable but interrelated executive control functions: Shifting, Inhibition, and Updating. A simple psychomotor speed measure was also included. Results: After controlling for age, gender, and education level, the results showed that the MDDA group displayed significantly impaired performance on the functions Shifting and Updating compared to HC. There emerged no significant differences between any of the patient groups and HC regarding Inhibition. The pure MDD group did not display dysfunctions relative to the HC group on the main executive control variables, but displayed slowed psychomotor speed. Contrary to expectation there were no significant differences between the MDDA and the MDD groups. Conclusion: Co-morbid anxiety should be taken into account when studying cognitive control functions in major depression.
?Qué requiere un estudio de caso para ser investigación cientifica?
Stiles,William B.;
Subjetividad y procesos cognitivos , 2009,
Abstract: i propose this answer to the title question: when observations of the case are explicitly brought to bear on a theory. i will first try to describe briefly what i mean by scientific research and how case studies can fit the description. then, as an illustration, i will describe the assimilation model, a theory about how people change in therapy (stiles, 2001, 2002; stiles et al., 1990), and give some examples of how case studies have been brought to bear on it. in this article, i focus on the scientific purposes of case studies. i acknowledge, however, that case studies may be interesting or enriching independently of their contribution to scientific theory (stiles, 2003).
Insecticide resistance in malaria vector mosquitoes at four localities in Ghana, West Africa
Richard H Hunt, Godwin Fuseini, Steve Knowles, Joseph Stiles-Ocran, Rolf Verster, Maria L Kaiser, Kwang Choi, Lizette L Koekemoer, Maureen Coetzee
Parasites & Vectors , 2011, DOI: 10.1186/1756-3305-4-107
Abstract: This paper presents baseline entomological data obtained during surveys conducted for four mining operations in Ghana, West Africa.The vast majority of the samples were identified as Anopheles gambiae S form with only a few M form specimens being identified from Tarkwa. Plasmodium falciparum infection rates ranged from 4.5 to 8.6% in An. gambiae and 1.81 to 8.06% in An. funestus. High survival rates on standard WHO bioassay tests were recorded for all insecticide classes except the organophosphates that showed reasonable mortality at all locations (i.e. > 90%). The West African kdr mutation was detected and showed high frequencies in all populations.The data highlight the complexity of the situation prevailing in southern Ghana and the challenges facing the malaria vector control programmes in this region. Vector control programmes in Ghana need to carefully consider the resistance profiles of the local mosquito populations in order to base their resistance management strategies on sound scientific data.Malaria remains today the biggest killer of children in Africa [1] and it demands increased attention from control authorities in affected countries. Multi-national corporations operating in Africa recognize the burden malaria places on their staff and its impact on their commercial operations [2,3]. There is an increasing move by these multi-nationals to control malaria within the boundaries of their activities, and in many cases, extending this control to the surrounding communities [4,5].The traditional methods of protecting work-forces using fogging, prophylaxis, repellents and handing out insecticide treated bed nets to workers (ITNs), have clearly not resulted in the desired outcome and companies are now implementing malaria control through the use of indoor residual house spraying [2,3]. Key to the success of these measures is knowledge of the local vector populations, the species identity, role in transmission and susceptibility to the four classes of insecti
Construyendo puentes: Diálogo entre un clínico y un investigador Building bridges: Dialog between a clinician and a researcher
William B Stiles,Patricio Olivos
Revista Chilena de Neuro-Psiquiatría , 2009,
Temperature dependence of the diffusive conductivity of bilayer graphene
Shaffique Adam,M. D. Stiles
Physics , 2009, DOI: 10.1103/PhysRevB.82.075423
Abstract: Assuming diffusive carrier transport and employing an effective medium theory, we calculate the temperature dependence of bilayer graphene conductivity due to Fermi-surface broadening as a function of carrier density. We find that the temperature dependence of the conductivity depends strongly on the amount of disorder. In the regime relevant to most experiments, the conductivity is a function of T/T*, where T* is the characteristic temperature set by disorder. We demonstrate that experimental data taken from various groups collapse onto a theoretically predicted scaling function.
Evaluating the locality of intrinsic precession damping in transition metals
Keith Gilmore,Mark D. Stiles
Physics , 2009, DOI: 10.1103/PhysRevB.79.132407
Abstract: The Landau-Lifshitz-Gilbert damping parameter is typically assumed to be a local quantity, independent of magnetic configuration. To test the validity of this assumption we calculate the precession damping rate of small amplitude non-uniform mode magnons in iron, cobalt, and nickel. At scattering rates expected near and above room temperature, little change in the damping rate is found as the magnon wavelength is decreased from infinity to a length shorter than features probed in recent experiments. This result indicates that non-local effects due to the presence of weakly non-uniform modes, expected in real devices, should not appreciably affect the dynamic response of the element at typical operating temperatures. Conversely, at scattering rates expected in very pure samples around cryogenic temperatures, non-local effects result in an order of magnitude decrease in damping rates for magnons with wavelengths commensurate with domain wall widths. While this low temperature result is likely of little practical importance, it provides an experimentally testable prediction of the non-local contribution of the spin-orbit torque-correlation model of precession damping. None of these results exhibit strong dependence on the magnon propagation direction.
Ab initio studies of the spin-transfer torque in tunnel junctions
Christian Heiliger,M. D. Stiles
Physics , 2007, DOI: 10.1103/PhysRevLett.100.186805
Abstract: We calculate the spin-transfer torque in Fe/MgO/Fe tunnel junctions and compare the results to those for all-metallic junctions. We show that the spin-transfer torque is interfacial in the ferromagnetic layer to a greater degree than in all-metallic junctions. This result originates in the half metallic behavior of Fe for the $\Delta_1$ states at the Brillouin zone center; in contrast to all-metallic structures, dephasing does not play an important role. We further show that it is possible to get a component of the torque that is out of the plane of the magnetizations and that is linear in the bias. However, observation of such a torque requires highly ideal samples. In samples with typical interfacial roughness, the torque is similar to that in all-metallic multilayers, although for different reasons.
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