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Search Results: 1 - 10 of 173723 matches for " Paul H Davis "
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Toxoplasma on the Brain: Understanding Host-Pathogen Interactions in Chronic CNS Infection
Sushrut Kamerkar,Paul H. Davis
Journal of Parasitology Research , 2012, DOI: 10.1155/2012/589295
Abstract: Toxoplasma gondii is a prevalent obligate intracellular parasite which chronically infects more than a third of the world’s population. Key to parasite prevalence is its ability to form chronic and nonimmunogenic bradyzoite cysts, which typically form in the brain and muscle cells of infected mammals, including humans. While acute clinical infection typically involves neurological and/or ocular damage, chronic infection has been more recently linked to behavioral changes. Establishment and maintenance of chronic infection involves a balance between the host immunity and parasite evasion of the immune response. Here, we outline the known cellular interplay between Toxoplasma gondii and cells of the central nervous system and review the reported effects of Toxoplasma gondii on behavior and neurological disease. Finally, we review new technologies which will allow us to more fully understand host-pathogen interactions. 1. Introduction Toxoplasma gondii belongs to the phylum Apicomplexa, which consists of intracellular parasites having a characteristically polarized cell structure and a complex cytoskeletal and organellar arrangement at their apical end [1]. This obligate intracellular parasite can infect and replicate within virtually any nucleated mammalian or avian cell [2, 3]. It is believed that the major transmission method of T. gondii to humans is the consumption of raw or rare meat [4–6]. In addition, vertical transmission of T. gondii is also possible, occurring when a female receives a primary infection while pregnant which can lead to fetal morbidity such as hydrocephaly. Indeed, T. gondii infection is a primary cause of fetal malformations in the United States [7]. Up to 80% of a population may be infected, depending on eating habits and exposure to felines, which serve as the definitive hosts and shed environmentally robust oocysts in feces [7, 8]. Oocysts can be stable in the environment for up to a year, may contaminate food or water supplies, and infect other warm blooded vertebrates [9]. A recent study suggested that oocyst-acquired infections are the most clinically severe form of infection, which may occur not just through direct cat fecal exposure, but contamination of municipal drinking water [10]. Two critical intracellular stages in the pathogenesis and transmission of Toxoplasma gondii are the rapidly replicating tachyzoite stage and the slower growing, cyst-forming bradyzoite stage. Initially, latent infections in humans were assumed to be largely asymptomatic. However, during the initial AIDS crisis, Toxoplasma became known as a
Social function in schizophrenia and schizoaffective disorder: Associations with personality, symptoms and neurocognition
Paul H Lysaker, Louanne W Davis
Health and Quality of Life Outcomes , 2004, DOI: 10.1186/1477-7525-2-15
Abstract: A self-report measure of the five factor model of personality was gathered along with ratings of social function, symptoms and assessments of neurocognition for 65 participants with schizophrenia or schizoaffective disorder.Univariate correlations and stepwise multiple regression indicated that frequency of social interaction was predicted by higher levels of the trait of Agreeableness, fewer negative symptoms, better verbal memory and at the trend level, lesser Neuroticism (R2 = .42, p < .0001). In contrast, capacity for intimacy was predicted by fewer negative symptoms, higher levels of Agreeableness, Openness, and Conscientiousness and at the trend level, fewer positive symptoms (R2 = .67, p < .0001).Taken together, the findings of this study suggest that person-centered variables such as personality, may account for some of the broad differences seen in outcome in schizophrenia spectrum disorders, including social outcomes. One interpretation of the results of this study is that differences in personality combine with symptoms and neurocognitive deficits to affect how persons with schizophrenia are able to form and sustain social connections with others.Interest has increasingly grown in understanding how differences in personality may affect outcome in schizophrenia [1,2]. Just as in a wide range of other severe and debilitating medical conditions [3-7], the manner in which people interpret and respond to a life touched by schizophrenia may deeply impact upon the recovery process [8-11].To date, one model of personality that has shown some promise in helping to systematically document the types of individual differences that help or hinder outcome in schizophrenia, is the "Five factor" model [12]. This model posits five endogenous traits [13] along which all persons vary, regardless of their socioeconomic status or culture and which exert an enduring impact on behavior, affect and cognition across the lifespan [14]. These five dimensions are Neuroticism, or vul
The University of Texas Millimeter Wave Observatory
Paul A. Vanden Bout,John H. Davis,Robert B. Loren
Physics , 2013,
Abstract: This is an account of the Millimeter Wave Observatory, a 4.9 meter diameter antenna facility that pioneered continuum observations of planets and interstellar molecular spectroscopy from 1971 to 1988. The circumstances of its founding, development of its instrumentation, and major research contributions are discussed. The MWO role in training of personnel in this new field is illustrated by a listing of student and postdoctoral observers, with titles of PhD theses that included MWO data.
A Killing tensor for higher dimensional Kerr-AdS black holes with NUT charge
Paul Davis
Mathematics , 2006, DOI: 10.1088/0264-9381/23/10/023
Abstract: In this paper, we study the recently discovered family of higher dimensional Kerr-AdS black holes with an extra NUT-like parameter. We show that the inverse metric is additively separable after multiplication by a simple function. This allows us to separate the Hamilton-Jacobi equation, showing that geodesic motion is integrable on this background. The separation of the Hamilton-Jacobi equation is intimately linked to the existence of an irreducible Killing tensor, which provides an extra constant of motion. We also demonstrate that the Klein-Gordon equation for this background is separable.
Separability of multi-charge black holes in supergravity
Paul Davis
Mathematics , 2006, DOI: 10.1088/0264-9381/23/23/014
Abstract: In this paper, we show that some five-dimensional rotating black hole solutions of both gauged and ungauged supergravity, with independent rotation parameters and three charges admit separable solutions to the massless Hamilton-Jacobi and Klein-Gordon equations. This allows us to write down a conformal Killing tensor for the spacetime. Conformal Killing tensors obey an equation involving a co-vector field. We find this co-vector field in three specific examples, and also give a general formula for it.
Disentangling electronic and vibrational coherence in the Phycocyanin-645 light-harvesting complex
Gethin H. Richards,Krystyna E. Wilk,Paul M. G. Curmi,Jeffrey A. Davis
Physics , 2013, DOI: 10.1021/jz402217j
Abstract: Energy transfer between chromophores in photosynthesis proceeds with near unity quantum efficiency. Understanding the precise mechanisms of these processes is made difficult by the complexity of the electronic structure and interactions with different vibrational modes. Two-dimensional spectroscopy has helped resolve some of the ambiguities and identified quantum effects that may be important for highly efficient energy transfer. Many questions remain, however, including whether the coherences observed are electronic and/or vibrational in nature and what role they play. We utilise a two-colour four-wave mixing experiment with control of the wavelength and polarization to selectively excite specific coherence pathways. For the light-harvesting complex PC645, from cryptophyte algae, we reveal and identify specific contributions from both electronic and vibrational coherences and determine an excited state structure based on two strongly-coupled electronic states and two vibrational modes. Separation of the coherence pathways also uncovers the complex evolution of these coherences and the states involved.
On-Chip Cavity Optomechanical Coupling
Bradley D Hauer,Paul H Kim,Callum Doolin,Allison JR MacDonald,Hugh Ramp,John P Davis
Physics , 2014, DOI: 10.1140/epjti4
Abstract: On-chip cavity optomechanics, in which strong co-localization of light and mechanical motion is engineered, relies on efficient coupling of light both into and out of the on-chip optical resonator. Here we detail our particular style of tapered and dimpled optical fibers, pioneered by the Painter group at Caltech, which are a versatile and reliable solution to efficient on-chip coupling. First, a brief overview of tapered, single mode fibers is presented, in which the single mode cutoff diameter is highlighted. The apparatus used to create a dimpled tapered fiber is then described, followed by a comprehensive account of the procedure by which a dimpled tapered fiber is produced and mounted in our system. The custom-built optical access vacuum chambers in which our on-chip optomechanical measurements are performed are then discussed. Finally, the process by which our optomechanical devices are fabricated and the method by which we explore their optical and mechanical properties is explained. It is our expectation that this manuscript will enable the novice to develop advanced optomechanical experiments.
Evolution of Bacterial Phosphoglycerate Mutases: Non-Homologous Isofunctional Enzymes Undergoing Gene Losses, Gains and Lateral Transfers
Jeremy M. Foster,Paul J. Davis,Sylvine Raverdy,Marion H. Sibley,Elisabeth A. Raleigh,Sanjay Kumar,Clotilde K. S. Carlow
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0013576
Abstract: The glycolytic phosphoglycerate mutases exist as non-homologous isofunctional enzymes (NISE) having independent evolutionary origins and no similarity in primary sequence, 3D structure, or catalytic mechanism. Cofactor-dependent PGM (dPGM) requires 2,3-bisphosphoglycerate for activity; cofactor-independent PGM (iPGM) does not. The PGM profile of any given bacterium is unpredictable and some organisms such as Escherichia coli encode both forms.
Proteomic Comparison of Entamoeba histolytica and Entamoeba dispar and the Role of E. histolytica Alcohol Dehydrogenase 3 in Virulence
Paul H. Davis,Minghe Chen,Xiaochun Zhang,C. Graham Clark,R. Reid Townsend,Samuel L. Stanley Jr.
PLOS Neglected Tropical Diseases , 2009, DOI: 10.1371/journal.pntd.0000415
Abstract: The protozoan intestinal parasite Entamoeba histolytica infects millions of people worldwide and is capable of causing amebic dysentery and amebic liver abscess. The closely related species Entamoeba dispar colonizes many more individuals, but this organism does not induce disease. To identify molecular differences between these two organisms that may account for their differential ability to cause disease in humans, we used two-dimensional gel-based (DIGE) proteomic analysis to compare whole cell lysates of E. histolytica and E. dispar. We observed 141 spots expressed at a substantially (>5-fold) higher level in E. histolytica HM-1:IMSS than E. dispar and 189 spots showing the opposite pattern. Strikingly, 3 of 4 proteins consistently identified as different at a greater than 5-fold level between E. histolytica HM-1:IMSS and E. dispar were identical to proteins recently identified as differentially expressed between E. histolytica HM-1:IMSS and the reduced virulence strain E. histolytica Rahman. One of these was E. histolytica alcohol dehydrogenase 3 (EhADH3). We found that E. histolytica possesses a higher level of NADP-dependent alcohol dehydrogenase activity than E. dispar and that some EhADH3 can be localized to the surface of E. histolytica. Episomal overexpression of EhADH3 in E. histolytica trophozoites resulted in only subtle phenotypic differences in E. histolytica virulence in animal models of amebic colitis and amebic liver abscess, making it difficult to directly link EhADH3 levels to virulence differences between E. histolytica and less-pathogenic Entamoeba.
Differences in the transcriptome signatures of two genetically related Entamoeba histolytica cell lines derived from the same isolate with different pathogenic properties
Laura Biller, Paul H Davis, Manuela Tillack, Jenny Matthiesen, Hannelore Lotter, Samuel L Stanley, Egbert Tannich, Iris Bruchhaus
BMC Genomics , 2010, DOI: 10.1186/1471-2164-11-63
Abstract: To obtain a comprehensive picture of the differences between the cell lines, we compared their transcriptomes using an oligonucleotide-based microarray and confirmed findings with quantitative real-time PCR. Out of 6242 genes represented on the array, 87 are differentially transcribed (≥two-fold) in the two cell lines. Approximately 50% code for hypothetical proteins. Interestingly, only 19 genes show a five-fold or higher differential expression. These include three rab7 GTPases, which were found with a higher abundance in the non-pathogenic cell line A. The aig1-like GTPasesare of special interest because the majority of them show higher levels of transcription in the pathogenic cell line B. Only two molecules were found to be differentially expressed between the two cell lines in both this study and our previous proteomic approach.In this study we have identified a defined set of genes that are differentially transcribed between the non-pathogenic cell line A and the pathogenic cell line B of E. histolytica. The identification of transcription profiles unique for amoebic cell lines with pathogenic phenotypes may help to elucidate the transcriptional framework of E. histolytica pathogenicity and serve as a basis for identifying transcriptional markers and virulence factors.The human protozoan parasite E. histolytica resides in the large bowel and can persist there for months or even years, causing asymptomatic luminal gut infection. Occasionally, E. histolytica trophozoites penetrate the intestinal mucosa, causing amoebic colitis and spread via portal circulation to other organs, most commonly to the liver, where they induce abscess formation.Currently, the factors determining the clinical outcome of E. histolytica infection are unknown, although a number of different hypotheses have been made. Host or parasite genetic factors could play a role, but so could the nature of the immune response, as well as concomitant infections or even diet.The mechanisms and proces
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