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排序方式: 共有713条查询结果,搜索用时 15 毫秒
41.
Nigel J Clarke Andy J Tomlinson Yasumasa Ohyagi Steven Younkin Stephen Naylor 《FEBS letters》1998,430(3):147
A quantitative method for detection of amyloid β peptides using immunoprecipitation-HPLC-mass spectrometry (IP-LC-MS) is described. Comparison of IP-LC-MS with sandwich ELISA revealed comparable results in the analysis of Aβ 1–40 and Aβ 1–42 derived from fetal guinea pig cell media and cell lysates. The use of IP-LC-MS not only allows a quantitative method for Aβ 1–40 and Aβ 1–42 peptides present in Alzheimer's disease (AD), but allows detection of other Aβ peptide species that may also play a role in the onset of AD in humans. 相似文献
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A survey was conducted to determine the levels of fumonisins B1 and B2 in corn and corn-based products available in Colombia
for human and animal consumption. A total of 120 samples were analyzed by acetonitrile-water extraction, cleanup with a strong-anion-exchange
column, and liquid chromatography with o-phthaldialdehyde-2-mercaptoethanol derivatization and fluorescence detection. The
samples of corn and corn-based products for animal intake were taken at different feed manufacturing plants, whereas the samples
used for human foods where purchased from local retail stores. The number of positive samples for fumonisin B1 was 20.0% higher
in corn and corn-based products for animal intake (75.0%) than in corn and corn-based products for human consumption (55.0%).
The levels of fumonisin B1 were also higher in corn and corn-based products for animal intake (mean = 694 μg/kg; range = 32–2964
μg/kg), than in corn and corn-based products for human intake (mean = 218 μg/kg; range = 24–2170 μg/ kg). The incidence and
levels of fumonisin B2 were lower than those for fumonisin B1. Corn and corn-based products for animal consumption had an
incidence of fumonisin B2 of 58.3%, with a mean value of 283 μg/kg, and a range of 44–987 μg/kg. The incidence of fumonisin
B2 in corn-based products for human intake was 35.0%, with a mean value of 118 μg/kg and a range of 21–833 μg/kg. The highest
incidence and levels of fumonisins were found in samples of hominy feed, with concentrations ranging from 86 to 2964 μg/kg
fumonisin B1 and 57 to 987 μg/kg fumonisin B2. 相似文献
44.
Naylor SW Nart P Sales J Flockhart A Gally DL Low JC 《Applied and environmental microbiology》2007,73(5):1493-1500
Enterohemorrhagic Escherichia coli O157:H7 is an important intestinal pathogen of humans with a main reservoir of domesticated ruminants, particularly cattle. It is anticipated that the risk of human infection can be reduced by controlling the organism within its reservoir hosts. Several options for the control of E. coli O157:H7 in cattle have been proposed, but none have been demonstrated to be successful in the field. Here we describe a novel experimental method, based on the terminal-rectum-restricted colonization described previously, to eliminate fecal carriage of E. coli O157:H7. In experimentally challenged calves, direct application to the rectal mucosa of either of two therapeutic agents, polymyxin B or chlorhexidine, greatly reduced bacterial shedding levels in the immediate posttreatment period. The most efficacious therapeutic agent, chlorhexidine, was compared in orally and rectally challenged calves. The treatment eliminated high-level shedding and reduced low-level shedding by killing bacteria at the terminal rectum. A rapid-detection system based on the ability to identify E. coli O157:H7 from swabs of the rectal mucosa was also assessed. This test was sufficiently sensitive to identify high-level bacterial carriage. Thus, a combination of the detection method and treatment regimens could be used in the field to eliminate high-level fecal excretion of E. coli O157:H7, so greatly reducing its prevalence within this host and the risk of human infection. 相似文献
45.
Sexual conflict can produce several evolutionary outcomes, one of which is female-limited trait polymorphism. We examine the African bat bug Afrocimex constrictus (Cimicidae), a species where both sexes are subjected to traumatic intromission from males. We show that males possess female genital structures that in related species ameliorate the costs of traumatic insemination. Moreover, the male form of these structures differs morphologically from the standard female form. Examination of females in our isolated study population revealed a discrete polymorphism in female genitalia. Some females had the typical cimicid form, while others had genitalia that more closely resembled the distinctive male form. Males, as well as females with the distinctive male form, experienced fewer traumatic copulations than the typical female morph. We propose that some females mimic the bizarre male condition in order to reduce the frequency of costly traumatic inseminations. To our knowledge this is the first example of a distinct female-limited genital polymorphism: its nature, as well as its association with traumatic sexual interactions, strongly suggests that sexual conflict underpins this unique phenomenon. 相似文献
46.
Saltatory conduction in myelinated axons requires organization of the nodes of Ranvier, where voltage-gated sodium channels are prominently localized [1]. Previous results indicate that alphaII-spectrin, a component of the cortical cytoskeleton [2], is enriched at the paranodes [3, 4], which flank the node of Ranvier, but alphaII-spectrin's function has not been investigated. Starting with a genetic screen in zebrafish, we discovered in alphaII-spectrin (alphaII-spn) a mutation that disrupts nodal sodium-channel clusters in myelinated axons of the PNS and CNS. In alphaII-spn mutants, the nodal sodium-channel clusters are reduced in number and disrupted at early stages. Analysis of chimeric animals indicated that alphaII-spn functions autonomously in neurons. Ultrastructural studies show that myelin forms in the posterior lateral line nerve and in the ventral spinal cord in alphaII-spn mutants and that the node is abnormally long; these findings indicate that alphaII-spn is required for the assembly of a mature node of the correct length. We find that alphaII-spectrin is enriched in nodes and paranodes at early stages and that the nodal expression diminishes as nodes mature. Our results provide functional evidence that alphaII-spectrin in the axonal cytoskeleton is essential for stabilizing nascent sodium-channel clusters and assembling the mature node of Ranvier. 相似文献
47.
Nicoud M Kong J Iqball S Kan O Naylor S Gouras P Allikmets R Binley K 《The journal of gene medicine》2007,9(12):1015-1023
BACKGROUND: We wanted to investigate the ability of recombinant equine infectious anemia virus (EIAV) vectors to transduce photoreceptor cells by developing a series of photoreceptor-specific promoters that drive strong gene expression in photoreceptor cells. METHODS: Promoter fragments derived from the rhodopsin (RHO), the beta phosphodiesterase (PDE) and the retinitis pigmentosa (RP1) genes were cloned in combination with an enhancer element, derived from the interphotoreceptor retinoid-binding protein gene (IRBP), into luciferase reporter plasmids. An in vitro transient reporter assay was carried out in the human Y-79 retinoblastoma cell line. The optimal promoters from this screen were then cloned into the recombinant EIAV vector for evaluation in vivo following subretinal delivery into mice. RESULTS: All promoters maintained a photoreceptor-specific expression profile in vitro and the gene expression was further enhanced in combination with the IRBP enhancer. The use of IRBP-combined RHO or PDE promoters showed modest but exclusive expression in photoreceptors following subretinal delivery to mice. By contrast an EIAV vector containing the cytomegalovirus (CMV) promoter drove reporter gene expression in both photoreceptors and retinal pigment epithelium. CONCLUSIONS: It may be possible to use recombinant EIAV vectors containing photoreceptor-specific promoters to drive therapeutic gene expression to treat a range of retinal degenerative diseases where the photoreceptor cell is the primary disease target. 相似文献
48.
Gary Klečka Jack Zabik Kent Woodburn Carter Naylor Charles Staples Brent Huntsman 《人类与生态风险评估》2007,13(4):792-822
This study was conducted to develop a statistical understanding of exposures to C8- and C9-alkylphenol ethoxylates (APEO) and their metabolites (APEM) in U.S. surface waters. Concentrations of APEO/APEM (all analytes) in freshwater have been reported by 19 investigations over the past 15 years. Only limited data are available for sediments and marine ecosystems. Based on the frequency of detection in surface waters, 67% of all analytes were below their detection limits. Although maximum reported concentrations varied with time, the average and 90th centile concentrations have remained relatively constant. Examination of frequency distributions for nonylphenol (NP) concentrations indicated that 99% of the levels in fresh surface waters are below the U.S. Environmental Protection Agency's Aquatic Life Ambient Chronic Water Quality Criteria for NP (6.6 μg/L). A conservative evaluation of aggregated NPEO/NPEM concentrations suggested that 97% of the samples contained aggregate NP equivalent concentrations that are also below 6.6 μg/L. These results suggest that on a nationwide basis, the likelihood of surface water concentrations exceeding the chronic USEPA Water Quality Criterion for NP is low. 相似文献
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