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Falush D Wirth T Linz B Pritchard JK Stephens M Kidd M Blaser MJ Graham DY Vacher S Perez-Perez GI Yamaoka Y Mégraud F Otto K Reichard U Katzowitsch E Wang X Achtman M Suerbaum S 《Science (New York, N.Y.)》2003,299(5612):1582-1585
Helicobacter pylori, a chronic gastric pathogen of human beings, can be divided into seven populations and subpopulations with distinct geographical distributions. These modern populations derive their gene pools from ancestral populations that arose in Africa, Central Asia, and East Asia. Subsequent spread can be attributed to human migratory fluxes such as the prehistoric colonization of Polynesia and the Americas, the neolithic introduction of farming to Europe, the Bantu expansion within Africa, and the slave trade. 相似文献
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GI Gellene 《Science (New York, N.Y.)》1996,274(5291):1344-1346
Application of a theory of nuclear symmetry-based reaction restrictions to the O2 + O --> O3 reaction provides a potential explanation for the symmetry-induced isotopic enrichment observed for laboratory and atmospherically produced O3. Within this theory, the rate of formation of O3 from collisions of O and isotopically homonuclear O2 depends on whether the O2 molecule is in an f (allowed) or an e (restricted) parity label state. The restriction can be relaxed by various potential energy surface coupling terms, and the assumption that approximately 78 percent of the restricted O2(e) levels produce O3 with the same efficiency as the allowed O2(f) levels can account for laboratory-observed isotopic fractionation. In particular, the theory explains the special enhanced formation of the completely asymmetric isotopomer 16O17O18O. 相似文献
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D. Perez-Perez G.H. Bechara R.Z. Machado G.M. Andrade R.E.M. del Vecchio M.S. Pedroso M.V. Hernández O. Farnós 《Veterinary parasitology》2010,167(2-4):321-326
The Bm86 antigen has been used to control ticks of the Boophilus genera in integrated programs that also include the use of acaricides. Because of recent phylogenetic studies have lead to the inclusion of all Boophilus species within the Rhipicephalus genera, we aimed to investigate the efficacy of the Bm86 antigen on the biotic potential of Rhipicephalus sanguineus. Domestic dogs were vaccinated with Bm86 and challenged with the three instars of R. sanguineus. Male and female mongrel dogs were divided into two groups of four animals each, comprising non-vaccinated and vaccinated animals. Immunized dogs were given two doses of an experimental formulation containing 50 μg of recombinant Bm86, at 21 days interval while the other group was given placebo, consisting of the same preparation without Bm86. Each dog was challenged 21 days after the last dose with 250 larvae, 100 nymphs and 55 adults (25 females and 30 males) released inside feeding chambers (one per instar) glued to their shaved flank. The effect of the vaccination was evaluated by determining biological parameters of ticks including the yield rates of larvae, nymphs and adult females. Adult females engorged weight, egg mass weight, efficiency rate of conversion to eggs (ERCE) and hatchability. In addition, sera were collected from dogs at 0, 21, 36, 45 and 75 days after the vaccination and used for the detection of specific antibodies by ELISA. Collection rates of larvae, nymphs and adult females fed on vaccinated dogs were significantly (p < 0.05) reduced by 38%, 29% and 31%, respectively, as compared with non-vaccinated controls. Significant reductions were also observed in weight of engorged females and egg mass, in ERCE, but not in the hatch rate of ticks fed on immunized dogs. ELISA data revealed a marked and significant increase in optical densities of sera from vaccinated animals after the second dose of Bm86. We concluded that the Bm86 antigen used as a vaccine for dogs reduced the viability and biotic potential of the R. sanguineus. 相似文献
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Aspholm-Hurtig M Dailide G Lahmann M Kalia A Ilver D Roche N Vikström S Sjöström R Lindén S Bäckström A Lundberg C Arnqvist A Mahdavi J Nilsson UJ Velapatiño B Gilman RH Gerhard M Alarcon T López-Brea M Nakazawa T Fox JG Correa P Dominguez-Bello MG Perez-Perez GI Blaser MJ Normark S Carlstedt I Oscarson S Teneberg S Berg DE Borén T 《Science (New York, N.Y.)》2004,305(5683):519-522
Adherence by Helicobacter pylori increases the risk of gastric disease. Here, we report that more than 95% of strains that bind fucosylated blood group antigen bind A, B, and O antigens (generalists), whereas 60% of adherent South American Amerindian strains bind blood group O antigens best (specialists). This specialization coincides with the unique predominance of blood group O in these Amerindians. Strains differed about 1500-fold in binding affinities, and diversifying selection was evident in babA sequences. We propose that cycles of selection for increased and decreased bacterial adherence contribute to babA diversity and that these cycles have led to gradual replacement of generalist binding by specialist binding in blood group O-dominant human populations. 相似文献
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KEE WOONG PARK SUNG HWAN CHOI JAE YOUNG AHN YOUNG GEOL SOHN CHANG‐GI KIM JEUNG JOO LEE 《Weed Biology and Management》2011,11(4):235-240
The herbicidal action of clove oil on cucumber seedlings was characterized under light and dark conditions. Paraquat showed herbicidal activity only under the light condition, whereas the clove oil displayed herbicidal activity in both the light and the dark condition. Specifically, wilting and water content reduction progressed rapidly under both the light and the dark condition 1 h after the clove oil treatment, whereas the paraquat damage occurred only under the light condition 5 h after treatment. The malondialdehyde concentration increased more with the clove oil treatment than with the paraquat treatment under the light and dark conditions. The superoxide dismutase (SOD) activity was stimulated, but the catalase activity decreased in the clove oil treatment. In contrast, both the SOD and catalase activity decreased in the paraquat treatment. These results suggest that clove oil exerts herbicidal effects through a mechanism that is different from that of paraquat. 相似文献
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SM Ossedryver GI Baldwin BM Stone RA McKenzie AW van Eps S Murray MT Fletcher 《Australian veterinary journal》2013,91(4):143-149
Three ponies continuously grazed a pasture containing an estimated 24% Indigofera spicata (wet weight basis) for 4–6 weeks in April and May 2004. They developed ataxia, paresis, depression, muscle fasciculations, dysphagia, ptyalism and halitosis. Two also developed corneal opacity. One pony recovered with supportive treatment, but the other two were euthanased and necropsied. Neuropathology was not present in either case, but both livers had periacinar and periportal lymphocytic infiltrations and hydropic degeneration of mid‐zonal hepatocytes, with mild to moderate periacinar necrosis also evident in one. The I. spicata contained 2.66 mg 3‐nitropropionic acid (3‐NPA)/g dry matter and 1.5 mg indospicine/g dry matter. Indospicine, but not 3‐NPA, was detected in serum from both of the euthanased ponies and indospicine was detected in heart, liver and muscle from the one pony in which this assay was performed. The clinical syndrome closely resembled ‘Birdsville horse disease’ caused by I. linnaei and was similar to that reported in horses poisoned by the closely related species I. hendecaphylla and to 3‐NPA poisoning of other animals, including humans. 3‐NPA is thought to cause this neurological syndrome. To our knowledge, this is the first authenticated report of I. spicata poisoning in grazing animals. We also report here the first published evidence that 3‐NPA and indospicine exist in naturalised I. spicata in Australia and of the formation of indospicine residues in tissues of animals grazing paddocks infested with I. spicata. 相似文献