OALib Journal期刊

ISSN: 2333-9721

費用:99美元

投稿

時間不限

2020 ( 225 )

2019 ( 543 )

2018 ( 583 )

2017 ( 621 )

自定義范圍…

匹配條件: “Peter S. Holt” ,找到相關結果約354970條。
列表顯示的所有文章,均可免費獲取
第1頁/共354970條
每頁顯示
Frequency and Persistence of Fecal Shedding Following Exposure of Laying Hens to Different Oral Doses of Salmonella enteritidis
Richard K. Gast,Rupa Guraya,Peter S. Holt
International Journal of Poultry Science , 2011,
Abstract: Infection of egg-laying poultry with Salmonella enteritidis and the associated transmission of illness to consumers of contaminated eggs has been a prominent international public health concern for many years. Testing and risk reduction programs for laying flocks have been implemented in many nations with some success. However, several critical parameters of S. enteritidis infections in chickens, including the relationship between the magnitude of oral exposure and the frequency and duration of bacterial shedding in voided feces, remain incompletely defined or explained. In the present study, groups of laying hens were experimentally infected with oral doses of 104, 106, or 108 CFU of a phage type 13a strain of S. enteritidis and the frequency at which the pathogen was shed in voided feces was determined at 8 weekly post-inoculation intervals. At 1 wk post-inoculation, the frequency of fecal shedding of S. enteritidis ranged from 23.8% for the 104 CFU dose to 87.5% for the 108 CFU dose. No fecal shedding was detected after 3 wk post-inoculation from hens inoculated with 104 CFU, but a small proportion (2.5% to 5.0%) of hens that received doses of 106 or more CFU of S. enteritidis were still shedding at 8 wk post-inoculation. The results of this study indicate that the oral exposure dose can significantly influence the frequency and duration of S. enteritidis fecal shedding into the environment by infected laying hens. A more complete understanding of how different levels of exposure are detected by particular sampling methods will support the effective application and interpretation of testing protocols for controlling poultry infections and preventing transmission to humans.
Changes in Peyers Patch and Cecal Tonsil B Lymphocytes in Laying Hens Following Challenge with Salmonella enterica Serovar Enteritidis
Peter S. Holt,Lara E. Vaughn,Richard K. Gast
International Journal of Poultry Science , 2011,
Abstract: Two trials were conducted to determine B cell changes in Peyers Patches (PP) and Cecal Tonsils (CT) of specific-pathogen-free Single Comb White Leghorn hens challenged with Salmonella enterica Serovar Enteritidis (SE). Prior to challenge and then weekly post challenge, 4 or 3 hens in Trials 1 and 2, respectively, were sacrificed and their intestinal tracts excised. Cells were purified from proximal and distal PP along with both CT and then aliquots of cells were incubated with antibodies to chicken immunoglobulins IgM, IgG and IgA. The B cells expressing the different immunoglobulin isotopes were identified via flow cytometric analysis. B lymphocytes expressing IgM were most prevalent, representing 40-60% and 30-50% of CT and PP B cells, respectively, while 20-30% of CT and PP lymphocytes expressed IgA. Only a small percentage of CT and PP lymphocytes, <10%, expressed IgG. Significantly more IgM+ cells were detected in CT vs proximal and distal PP and proximal PP in trials 1 and 2, respectively. Significantly more IgA+ cells were observed in proximal PP vs distal PP and CT in trial 1 but not in trial 2. Following SE infection, these differences were no longer observed. For IgG+ cells, however, no significant differences between tissues were observed prior to challenge but significantly more IgG+ cells were observed in both PP vs CT at weeks 1 and 3 post challenge in trial 1 and week 1 post challenge in trial 2. These results indicate that B lymphocyte differences do occur in PP vs CT in adult chickens and these populations can change in response to stimuli such as intestinal infection.
Frequency and Magnitude of Internal Organ Colonization Following Exposure of Laying Hens to Different Oral Doses of Salmonella enteritidis
Richard K. Gast,Rupa Guraya,Jean Guard,Peter S. Holt
International Journal of Poultry Science , 2011,
Abstract: Contaminated eggs produced by infected laying hens continue to pose a significant public health concern as a leading source of transmission of Salmonella enteritidis infections to humans. A recently implemented national regulatory program for egg-producing poultry in the United States seeks to control egg-borne transmission of illness to consumers via a diverse program of mandatory risk reduction practices plus testing to detect infected flocks. However, many aspects of S. enteritidis infections in laying hens, including the precise relationship between the magnitude of oral exposure and infection parameters such as the numbers of bacteria that reach internal tissues, remain unresolved. In the present study, groups of laying hens were experimentally infected with oral doses of 104, 106, or 108 CFU of a phage type 13a strain of S. enteritidis and the number of S. enteritidis cells in the livers of infected hens was determined at 5 d and 20 d post-inoculation. The frequency of S. enteritidis recovery from livers ranged from 30% (104 CFU dose) to 90% (108 CFU dose) at 5d post-inoculation and from 0% (104 CFU dose) to 40% (108 CFU dose) at 20 d post-inoculation. Significantly (p<0.05) greater numbers of S. enteritidis were isolated from livers at both 5 d and 20 d post-inoculation following inoculation with 108 CFU than after administration of either of the two lower doses. These results demonstrate that the oral exposure dose significantly affects important parameters of S. enteritidis infection in laying hens and could thereby influence the outcome of testing efforts. Interpreting the potential implications of testing results and improving the effectiveness of testing protocols are both contingent on understanding how different levels of exposure are likely to be detected by particular sampling methods
A novel form of the membrane protein CD147 that contains an extra Ig-like domain and interacts homophilically
S Hanna, Peter Kirk, Oliver J Holt, Michael J Puklavec, Marion H Brown, A Barclay
BMC Biochemistry , 2003, DOI: 10.1186/1471-2091-4-17
Abstract: We report the characterisation of a form of CD147 with an additional membrane-distal Ig-like domain. In contrast to the two domain form, this three domain form of CD147 interacts homophilically. Surface plasmon resonance analysis using recombinant proteins showed that the interaction was of low affinity (KD ~ 40 μM) and this is typical of many interactions between membrane proteins. cDNA for the 3 domain form are rare but have been identified in human and mouse retina.The finding that the three domain form of CD147 has an extracellular ligand, that is it interacts homophilically, suggests this interaction may be important in aligning lactate transporters in the retina where lactate is an important metabolite.CD147 is a widely expressed membrane glycoprotein (also called OX47, basigin, EMMPRIN and HT7) and has been implicated in matrix metalloproteinase induction, cell adhesion, retinal cell development, HIV attachment, embryonic development, and T cell activation [1-5]. The transmembrane region has a very high degree of cross species homology, being identical between chicken and rat and containing a centrally positioned glutamic acid. This is crucial for its lateral association with monocarboxylate transport molecules MCT1 and MCT4 [6]. MCT1 and MCT4 are proton-coupled transporters of monocarboxylates, principally the metabolic intermediate lactate [7]. It may be that some of the diverse functions attributed to CD147 are due to effects on the carboxylate transporters.The extracellular region of CD147 contains 2 Ig-like domains. This is very common in leukocyte membrane proteins and these proteins often interact with other cell surface proteins [8]. No extracellular ligand has yet been identified for CD147 although an interaction with cyclophilin has been shown to be mediated by glycosaminoglycans [2]. Despite extensive studies using a variety of constructs for recombinant proteins we have not found any cellular ligands (unpublished data) and it may be that the role
Effect of Prior Passage Through Laying Hens on Invasion of Reproductive Organs by Salmonella enteritidis
Richard K.Gast,Jean Guard-Bouldin,Rupa Guraya,Peter S. Holt
International Journal of Poultry Science , 2009,
Abstract: The colonization of reproductive tissues in infected laying hens is a pivotal stage in the production of contaminated eggs that can transmit Salmonella enteritidis infections to humans. In an earlier study, a series of passages through infected laying hens increased the frequency at which an S. enteritidis isolate was deposited inside eggs. The present study evaluated the effect of in vivo passage of an S. enteritidis isolate on its ability to invade to internal tissues, including three different regions of the reproductive tract. In each of three trials, a group of laying hens was infected orally with a PT13a strain of S. enteritidis (prepared from a separate stock culture each time). After internal organ samples were removed from this first passage group for culturing at 7 days post-inoculation, an S. enteritidis isolate from the upper oviduct of an extensively infected hen was used to infect another (second passage) group of hens in each trial. The overall frequency of S. enteritidis isolation from internal organs increased between passages in only one of the three trials and no increases were observed between passages in the frequency of S. enteritidis recovery from any of the three reproductive tissue sites. Therefore, passage of S. enteritidis through infected chickens did not always select for either higher overall invasiveness or for a higher ability to colonize reproductive organs in the present study.
Development of Recombinant Flagellar Antigens for Serological Detection of Salmonella enterica Serotypes Enteritidis, Hadar, Heidelberg, and Typhimurium in Poultry
Joseph Minicozzi,Susan Sanchez,Margie D. Lee,Peter S. Holt,Charles L. Hofacre,John J. Maurer
Agriculture , 2013, DOI: 10.3390/agriculture3030381
Abstract: Accurate and fast detection of harmful Salmonella is a major concern of food safety. Common Salmonella serotypes responsible for human associated foodborne outbreaks are S. Enteritidis, S. Hadar, S. Heidelberg, and S. Typhimurium are also commonly isolated from poultry. Serology is commonly used to monitor disease in poultry, therefore application of Salmonella serotype-specific test will have added value in Salmonella surveillance or monitoring vaccine efficacy. Recombinant flagellins were purified to be used as antigens in an ELISA. In this study, an ELISA was developed for the serological detection of S. Enteritidis. Once optimized, 500 ng of purified recombinant S. Enteritidis flagellin and a 1:64 dilution were determined to be optimal for testing sera. A negative baseline cutoff was calculated to be an optical density (OD) of 0.35. All sera from birds with history of S. Enteritidis exposure tested positive and all sera from chickens with no exposure tested negative to this Salmonella serotype. Current ELISA for serological detection of Salmonella suffers from cross reactivity inherent in lipopolysaccharide (LPS) or whole cell antigen based serological tests. This new ELISA eliminates common cross reactivity by focusing specifically on the flagellins of the Salmonella serotypes common in poultry and associated with foodborne outbreaks.
New insights into calcium, dairy and colon cancer
Peter R Holt
World Journal of Gastroenterology , 2008,
Abstract: This paper is to review recent information about the relationship of calcium and dairy foods to colon cancer. The review focuses on primary prevention, discusses the potential components in dairy foods that might be anti-neoplastic, reviews the epidemiologic information and describes intervention studies demonstrating efficacy of calcium and vitamin D in reducing colorectal polyp recurrence. Since vitamin D is important in cancer prevention, pertinent data is discussed and potential mechanisms of actions presented. Calcium and vitamin D are important agents for the primary prevention of colorectal neoplasia.
Sacred Cows and Sympathetic Squirrels: The Importance of Biological Diversity to Human Health
Andy Dobson ,Isabella Cattadori,Robert D Holt,Richard S Ostfeld,Felicia Keesing,Kristle Krichbaum,Jason R Rohr,Sarah E Perkins,Peter J Hudson
PLOS Medicine , 2006, DOI: 10.1371/journal.pmed.0030231
Abstract:
Safety and Immunogenicity of Neonatal Pneumococcal Conjugate Vaccination in Papua New Guinean Children: A Randomised Controlled Trial
William S. Pomat, Anita H. J. van den Biggelaar, Suparat Phuanukoonnon, Jacinta Francis, Peter Jacoby, Peter M. Siba, Michael P. Alpers, John C. Reeder, Patrick G. Holt, Peter C. Richmond, Deborah Lehmann, for the Neonatal Pneumococcal Conjugate Vaccine Trial Study Team
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0056698
Abstract: Background Approximately 826,000 children, mostly young infants, die annually from invasive pneumococcal disease. A 6-10-14-week schedule of pneumococcal conjugate vaccine (PCV) is efficacious but neonatal PCV may provide earlier protection and better coverage. We conducted an open randomized controlled trial in Papua New Guinea to compare safety, immunogenicity and priming for memory of 7-valent PCV (PCV7) given in a 0-1-2-month (neonatal) schedule with that of the routine 1-2-3-month (infant) schedule. Methods We randomized 318 infants at birth to receive PCV7 in the neonatal or infant schedule or no PCV7. All infants received 23-valent pneumococcal polysaccharide vaccine (PPV) at age 9 months. Serotype-specific serum IgG for PCV7 (VT) serotypes and non-VT serotypes 2, 5 and 7F were measured at birth and 2, 3, 4, 9, 10 and 18 months of age. Primary outcomes were geometric mean concentrations (GMCs) and proportions with concentration ≥0.35 μg/ml of VT serotype-specific pneumococcal IgG at age 2 months and one month post-PPV. Results We enrolled 101, 105 and 106 infants, respectively, into neonatal, infant and control groups. Despite high background levels of maternally derived antibody, both PCV7 groups had higher GMCs than controls at age 2 months for serotypes 4 (p<0.001) and 9V (p<0.05) and at age 3 months for all VTs except 6B. GMCs for serotypes 4, 9V, 18C and 19F were significantly higher (p<0.001) at age 2 months in the neonatal (one month post-dose2 PCV7) than in the infant group (one month post-dose1 PCV7). PPV induced significantly higher VT antibody responses in PCV7-primed than unprimed infants, with neonatal and infant groups equivalent. High VT and non-VT antibody concentrations generally persisted to age 18 months. Conclusions PCV7 is well-tolerated and immunogenic in PNG neonates and young infants and induces immunologic memory to PPV booster at age 9 months with antibody levels maintained to age 18 months. Trial Registration ClinicalTrials.gov NCT00219401NCT00219401
Controlling and Evaluating the Structure and Morphology of Polymers on Multiple Scales  [PDF]
Geoffrey R. Mitchell, Ana Tojeira, Thomas Gkourmpis, James J. Holt, Peter Harris, Marilena Pezzuto
Journal of Materials Science and Chemical Engineering (MSCE) , 2015, DOI: 10.4236/msce.2015.312009
Abstract:

Crystalline polymers spontaneously form hierarchical structures although the precise manner in which these scales of structure are interconnected especially terms of the formation and evolution of the complete structure remains unclear. We have set out to control these scales of structure by introducing additional components which self-assemble in to nano-scale units which then direct the crystallisation of the polymer matrix. In other words, we first assemble a low concentration top-level structure which is designed to template or direct the sub-sequent crystallisation of the matrix polymer. This top level structure takes on the role of controlling the structure. We have set out to both establish the design principles of such structures and to develop experimental procedures which allow us to follow the formation of such complex hierarchical polymer structures. In particular we focus of the relationships between these different levels of structure and time sequence of events required for the structure to evolve in the targeted manner. In this programme, we have exploited time-resolving small-angle X-ray scattering and electron microscopy together with neutron scattering to probe and quantify the different scales of structure and their evolution. We highlight new neutron scattering instrumentation which we believe have great potential in the growing field of hierarchical structures in polymers. The addition of small quantities of nanoparticles to conventional and sustainable thermoplastics leads to property enhancements with considerable potential in a number of areas Most engineered nano-particles are highly stable and these exist as nano-particles prior to compounding with the polymer resin, they remain as nano- particles during the active use as well as in the subsequent waste and recycling streams. In this work we also explore the potential for constructing nano-particles within the polymer matrix during processing from organic compounds selected to provide nanoparticles which can effectively control the subsequent crystallization process. Typically these nano-particles are rod-like in shape.

第1頁/共354970條
每頁顯示


Home
Copyright ? 2008-2017 Open Access Library. All rights reserved.

久草在现在线中文字幕