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1.
Altered acetylcholinesterase (AChE) has been identified in numerous arthropod species resistant to organophosphate (OP) and carbamate insecticides. The New World screwworm (NWS) Cochliomyia hominivorax (Coquerel), one of the most important myiasis-causing flies in the Neotropics, has been controlled mainly by the application of OP insecticides in its current geographical distribution. However, few studies have investigated insecticide resistance in this species. Based on previous studies about mutations conferring OP resistance in related dipteran species, AChE cDNA was sequenced allowing a survey for mutations (I298V, G401A, F466Y) in NWS populations. In addition, the G137D mutation in the carboxylesterase E3 gene, also associated with OP resistance, was analyzed in the same NWS populations. Only 2/135 individuals presented an altered AChE gene (F466Y). In contrast, a high frequency of the G137D mutation in the E3 gene was found in some localities of Brazil and Uruguay, while the mutant allele was not found in Cuba, Venezuela or Colombia. These findings suggest that the alteration in the carboxylesterase E3 gene may be one of the main resistance mechanisms selected in this ectoparasite. The knowledge of the frequency of these resistance-associated mutations in the NWS natural populations may contribute to the selection of appropriate chemicals for control as part of pest management strategies. 相似文献
2.
This paper combines the results from a preliminary survey of occurrence of Cryptosporidium species in faecal samples from a range of wild mammal species inhabiting mainland Britain with a tabulated literature review of world-wide reports of the parasite in those British mammals. In the literature, C. parvum was reported from 11 wild mammals found in Britain and elsewhere, mainly in rodents but also in insectivores, lagomorphs and ungulates. C. muris has been reported only in wild rodents. The sample survey detected C. parvum in seven additional British species, including carnivores. Overall, 12% of 184 faecal samples tested with a genus-specific monoclonal antibody contained oocysts of C. parvum. The results further emphasise the widespread distribution of Cryptosporidium amongst wild mammals in Britain, highlight the potential for transmission between host species and warn of the possibility of direct exposure for anybody using the countryside for professional or recreational purposes (e.g. farmers and ramblers) to previously unregarded sources of infection. It seems increasingly likely that most, if not all, mammalian species can be infected with C. parvum. 相似文献
3.
We evaluated the ability of hen-egg antibodies (HEA) to reduce intestinal colonization by Clostridium perfringens in broiler chickens. Antibodies against C. perfringens or cholera toxin (negative control) were obtained from the eggs of laying hens hyperimmunized using a C. perfringens bacterin or cholera toxin. Eggs were collected, pooled, and egg antibodies were concentrated by polyethylene-glycol precipitation. An initial experiment was conducted to determine the in vivo activity of the administered antibody along the length of the intestine. Thereafter, two feeding trials were performed to assess the efficacy of feed amended with the egg antibodies in reducing the level of colonization of C. perfringens in challenged birds. Antibody activity declined from proximal to distal regions of the intestine but remained detectable in the cecum. In the first experiment there was no significant reduction in the number of C. perfringens in the birds fed the diet amended with the anti-C. perfringens egg antibody, compared to the birds that received the anti-cholera toxin egg antibody (n = 10), at any of the sampling times. In the second experiment there was a significant decrease in C. perfringens intestinal populations 72 h after treatment (n = 15) as assessed by culture-based enumeration, but there was no decrease as measured by quantitative PCR based on the C. perfringens phospholipase C gene. Intestinal-lesion scores were higher in the birds that received the anti-C. perfringens HEA. Our work suggests that administration of HEA did not reduce the level of C. perfringens intestinal colonization and conversely might exacerbate necrotic enteritis. 相似文献
4.
目前物种的相对多度与种间关系的内部联系如何影响物种共存仍不清楚。为探讨植物群落物种间关系强度的多度不对称性及其对载畜率的响应,本研究以内蒙古短花针茅(Stipa breviflora)荒漠草原植物群落为对象,分析了对照、轻度、中度及重度放牧下群落物种的多度及其频率。结果表明：随载畜率的增大,物种数呈现出降低的趋势。不同载畜率下同分布指数CO均存在明显的多度依赖性;常见种(如短花针茅、无芒隐子草(Cleistogenes songorica)及刺穗藜(Chenopodum aristatum))对其他物种的作用强度普遍较强。不同载畜率下短花针茅对无芒隐子草及刺穗藜的作用强度均高于其二者对短花针茅的强度,表现出种间强度的不对称性。此外,放牧使得短花针茅对无芒隐子草的作用强度呈现出增大的趋势,使得无芒隐子草对短花针茅的作用强度呈现出降低的趋势。因此,物种间存在多度的不对称性,而放牧进一步造成其物种间作用强度的变化。 相似文献
5.
A study was made of alkaline and acid phosphatase isoenzymes and non-specific esterases in homogenates of the trematodes Fasciola hepatica and Dicrocoelium dendriticum obtained from infected tissues of Capra hircus and Ovis aries using horizontal polyacrylamide gel electrophoresis.
The esterase patterns in F. hepatica and D. dendriticum were different. Homogenate of F. hepaticafrom both hosts gave four enzyme bands. For D. dendriticum, however, while homogenates of parasites from C. hircus also gave four bands, those of O. aries gave only three bands.
Acid and alkaline phosphatases in homogenates of both parasites showed three enzyme bands, but there was a host species difference betwen the enzyme patterns of specimens collected from C. hircus versus O. aries. 相似文献
6.
驼绒藜属3种植物开花习性及雌花柱头微形态研究 总被引：9，自引：0，他引：9
研究驼绒藜属3种植物开花规律、开花日动态、结实率及柱头微形态。结果表明,华北驼绒藜和驼绒藜雄花开花高峰均在上午8:00～10:00,有利于传粉和受精,而北美驼绒藜雄花在中午11:00～13:00达开放高峰,其雌雄花开花高峰期不一致,不利于传粉、受精,从而降低结实率。三者的开花最适温度基本一致,都在20～24℃。三者的雌花均在下午14:00左右达到开放高峰。雌花柱头微形态研究结果表明,华北驼绒藜的柱头有利于接受花粉,而北美驼绒藜的柱头不利于接受花粉。此外,华北驼绒藜与驼绒藜的雌、雄花花期相遇结实率较高,而北美驼绒藜因花期不遇,故导致结实率低。 相似文献
7.
为探究不同载畜率对荒漠草原群落建群种与优势物种间的关系及其空间分布的影响，于2020年7-9月在内蒙古四子王旗短花针茅荒漠草原进行野外调查，以建群种短花针茅及优势种无芒隐子草和冷蒿为研究对象，设置不放牧对照（CK）、轻度（LG）、中度（MG）和重度放牧（HG）载畜率水平（分别放牧0、4、8和12只羊），结合常规方法与地统计学方法分析建群种及优势种出现频率、多度、种间关系强度及空间分布特征。结果表明：1）与CK相比，LG下冷蒿出现频率仅在7月显著降低了50.55%（P<0.05），而MG和HG在7-9月均显著降低（P<0.05），7-9月平均降低77.76%和97.53%；而不同处理及月份下短花针茅和无芒隐子草出现频率无显著差异（P>0.05）。 2）与CK相比，各处理在7-9月时短花针茅种群多度均显著增加（P<0.05），LG、MG和HG分别在7-9月平均增加37.34%、75.72%和99.32%；冷蒿种群多度均显著降低（P<0.05），分别降低61.26%、66.32%和99.31%；无芒隐子草除LG在9月无显著变化外，各处理在7-9月时种群多度均显著增加（P<0.05）。3）短花针茅与无芒隐子草主要表现为亲和关系，而在9月时从CK的亲和关系转化为HG的竞争关系；短花针茅与冷蒿主要表现为竞争关系，放牧未改变其种间关系。4）短花针茅与无芒隐子草对冷蒿的作用强度较大，而冷蒿对短花针茅和无芒隐子草的作用强度较小。5）模拟9月物种间空间分布发现，CK中短花针茅种群多度随无芒隐子草种群多度增加而增加，随冷蒿种群多度增加而呈降低的趋势；HG中冷蒿种群多度不随短花针茅与无芒隐子草的变化而变化，但随着无芒隐子草种群多度增加，短花针茅种群多度整体上呈波动下降的趋势，表明短花针茅与无芒隐子草之间的关系由CK中的亲和关系转变为HG下的竞争关系。综上，放牧会改变物种的种群多度及物种间的关系。 相似文献
8.
试验旨在研究酵母多糖对空肠弯曲菌感染獭兔生产性能、载菌量、盲肠和皮肤抗菌肽的影响。选取断奶獭兔180只,随机分为5组,每组6个重复,每个重复6只。对照组饲喂基础日粮,其他4组空肠弯曲菌感染,并于基础日粮中分别添加0、200、400、600 mg/kg酵母多糖。饲养试验起始日诱导空肠弯曲菌感染,饲养试验持续35 d。结果显示,空肠弯曲菌感染降低了獭兔结束体重、日增重和日采食量,提高了料重比（P < 0.05）,添加酵母多糖改善了这些指标（P < 0.05）,且日增重和料重比达到了对照组水平。酵母多糖降低了獭兔盲肠食糜、皮肤、肝脏、脾脏的空肠弯曲菌载菌量（P < 0.05）。空肠弯曲菌感染诱导内源性抗菌肽的Cathelicidin、Galectin-3和LEAP2基因表达量显著上调（P < 0.05）,对DEFA4基因无显著影响,而添加酵母多糖对基因表达量具有进一步上调作用（P < 0.05）。酵母多糖添加剂量与结束体重、日增重呈现线性和平方效应关系（P<0.05）;与皮肤、肝脏和脾脏载菌量呈现线性效应（P<0.05）;与盲肠和皮肤抗菌肽Cathelicidin和Galectin-3基因表达水平呈现线性效应（P<0.05）;与盲肠抗菌肽Galectin-3、LEAP2和DEFA4基因呈现平方效应（P<0.05）。表明日粮添加酵母多糖可以降低空肠弯曲菌感染獭兔组织载菌量,提高内源抗菌肽活性,不影响獭兔生产性能。 相似文献
9.
Insecticidal ear tags impregnated with organophosphate (OP) insecticides were used each year from 1989 to 1998 at Rosepine, LA. Weekly fly counts were conducted to evaluate control efficacy of the treatments, and bioassays were conducted at least twice per year to measure fly susceptibility to OP and pyrethroid insecticides. Between 1989 and 1992, the efficacy of 20% diazinon-impregnated ear tags was reduced from >20 to just 1 week of control. A high risk of control failure was observed when a resistance frequency of approximately 5% was measured in pre-season bioassays. Resistance to diazinon, fenthion, ethion, pirimiphos-methyl, and tetrachlorvinphos was observed. Esterase activity toward alpha-naphthyl acetate was significantly higher in flies collected at Rosepine in 1997 than in flies from a laboratory colony and from a susceptible field population. 相似文献
10.
A total of 469 fecal samples were collected from American minks (Mustela vison) on a farm in Hebei Province in China and examined for Cryptosporidium by Sheather's sugar flotation technique and 8 Cryptosporidim isolates were obtained. The partial 18S rRNA, 70 kDa heat shock protein (HSP70), Cryptosporidium oocyst wall protein (COWP) and actin genes of six isolates were sequenced. Sequence data were analyzed together with known Cryptosporidium spp. and genotypes. Results of this multi-locus genetic characterization indicated that the six Cryptosporidium isolates in this study shared the same sequences of the genes studied and were different from known Cryptosporidium species and genotypes. The closest relative was Cryptosporidium ferret genotype with 7, 22, 2 and 2 nucleotide differences in the 18S rRNA, HSP70, COWP and actin genes, respectively. The homology to ferret genotype at the 18S rRNA locus was 99.1%, which is comparable to that between C. parvum and C. hominis (99.2%), or between C. muris and C. andersoni (99.4%). Therefore, the Cryptosporidium in minks in this study is considered a new genotype, the Cryptosporidium mink genotype. 相似文献
11.
Temeyer KB Li AY Lohmeyer KH Chen AC Olafson PU Sanson DW Foil LD 《Veterinary parasitology》2008,154(3-4):300-310
Acetylcholinesterase (AChE) cDNA from individual field-collected diazinon-resistant horn flies was amplified by RT-PCR. Sequencing of the amplification products revealed that 8/12 of the diazinon-resistant horn flies contained a point mutation previously associated with resistance to organophosphates in house flies and Drosophila, strongly suggesting that this cDNA encodes the AChE that is the target site for organophosphate (OP) pesticide. The point mutation (G262A) resulted in a shift from glycine to alanine in the mature HiAChE amino acid sequence at position 262. Allele-specific PCR and RLFP assays were developed to diagnose the presence or absence of the G262A mutation in individual flies. Use of the allele-specific assays each demonstrated the presence of the G262A mutation in 10 of 12 individual field-collected flies, demonstrating higher sensitivity than direct sequencing of RT-PCR amplification products. The G262A mutation was found in additional fly populations previously characterized as OP-resistant, further supporting that this AChE is the target site for OP pesticide. The allele-specific assay is a useful tool for quantitative assay of the resistance allele in horn fly populations. 相似文献
12.
The aim of this study was to isolate and characterize the causal pathogen and study the biological characteristics of sclerotinia rot of Codonopsis pilosula. Pathogen material was obtained by tissue isolation. The isolated fungal species were comprehensively evaluated in terms of their morphology，rDNA-ITS sequence，RPB2 gene of RNA polymerase Ⅱ，and biological characteristics. The pathogens were identified as Sclerotinia nivalis and Sclerotinia sclerotiorum，and of the two，S. nivalis was the dominant species. The optimum temperatures for mycelium growth and sclerotia formation of S. nivalis were 20 and 15 ℃，respectively，while corresponding values for S. sclerotiorum were 25 and 25 ℃ . The optimum pH for mycelium growth was 6 for both species，while optimum pH for sclerotia formation was 6 for S. nivalis and 7 for S. sclerotiorum. The optimum culture medium was 100% potato dextrose agar（PDA）. The mycelial growth rate approach was applied to test the toxicity of adiacylamine， which exhibited inhibitory activity with EC50 on S. nivalis at 0. 2625 mg·L-1 and on and S. sclerotiorum at 0. 4165 mg·L-1. In summary，this is the first report of S. nivalis and S. sclerotiorum causing sclerotinia rot on C. pilosula in China，and the data presented provide a reliable scientific proof of the pathogen diagnosis and a theoretical basis for the development of prevention measures. © 2022 Editorial Office of Acta Prataculturae Sinica. All rights reserved. 相似文献
13.
本研究自陕西省富平县某规模化关中奶山羊养殖场腹泻奶山羊肛门拭子中分离到5株产气荚膜梭菌,命名为21-D-1~21-D-5。毒素基因检测表明,其均为携带etx的D型产气荚膜梭菌,且21-D-5携带食源性致病毒素基因cpe。全基因组序列测定显示,5株D型产气荚膜梭菌基因组大小、GC含量和基因数量稳定;单核苷酸多态性（SNPs）分析显示,21-D-1和21-D-2以及21-D-3和21-D-4之间的SNPs差异极低（<25）,表明其大概率属于相同的产气荚膜梭菌菌株。分离的D型产气荚膜梭菌基因组中共检测到15种毒素基因,其中,毒素基因etx在分离的D型菌株中高度保守、基因环境相似,且在菌株21-D-5中毒素基因cpe位于etx下游。此外,包括噁唑烷酮类耐药基因optrA在内的9种耐药基因也在分离株中被检测到,并且erm（A）、optrA和fexA具有共同传播的可能性。本研究为国内首次对D型产气荚膜梭菌进行全基因组序列测定分析,结果对产气荚膜梭菌疾病的防治和基因组的进一步研究具有参考价值。 相似文献
14.
Fecal samples were collected from 325 adult cattle and 108 pigs in a slaughterhouse in Hokkaido, the northern island of Japan. Five adult cattle were found to be positive for oocysts of Cryptopsoridium (1.5%). The oocysts were morphologically similar to those of Cryptosporidium andersoni. The partial sequence of the 18S rRNA gene of the isolate was 100% identical with that of the C. andersoni Kawatabi strain. SCID mice were infected after oral administration. Based on the morphology of the oocysts, the sequence of the 18S rRNA gene and the infectivity to SCID mice, the isolate was concluded to be of the same type as the C. andersoni Kawatabi strain that has been isolated in Honshu, the main island of Japan. 相似文献
15.
In order to study the occurrence and co-infection of different species of Campylobacter, enteric Helicobacter and Anaerobiospirillum in dogs and cats and define a possible association between these microrganisms and gastrointestinal disorders, 190 dogs and 84 cats, either healthy or with diarrhea, were sampled between 2002 and 2003. Thirty-three C. upsaliensis, 17 C. jejuni, 2 C. helveticus, 1 C. lari isolates from dogs and 14 C. helveticus, 7 C. jejuni, 6 C. upsaliensis isolates from cats were identified using species-specific PCR and phenotypic tests. Whole cell protein profile analysis, phenotypic tests, PCR-RFLP of gyrB and a phylogenetic study of partial groEL and 16S rRNA sequences were used to identify 37 H. bilis, 22 H. canis and 14 H. cinaedi in dogs and 12 H. canis, 5 H. bilis and 2 H. cinaedi in cats. Whole cell protein profile analysis, phenotypic tests and species-specific PCR of 16S rRNA were used to identify 14 A. succiniciproducens, 12 A. thomasii isolates and one unidentified Anaerobiospirillum sp. isolate in dogs and 3 A. thomasii isolates in cats. Fifty-two animals (19%) were positive for the isolation of more than one genus. No significant statistical correlation was found between any isolates of Campylobacter, Helicobacter or Anaerobiospirillum spp. or the various co-infection rates, and the presence of diarrhea in either dogs or cats. Campylobacter isolates were also tested for antibiotic resistance using the agar dilution method. 相似文献
16.
超干贮藏对菊苣种子活力与抗氧化性的影响 总被引：5，自引：3，他引：2
研究超干处理对菊苣种子活力和抗氧化性的影响,采用硅胶干燥法超干处理菊苣种子,分别得到8.45%,5.17%,3.64%,2.33%和1.69%含水量的种子,密封于双层铝箔袋内放在50℃恒温箱内进行人工老化处理10 d,回水后测量种子活力及抗氧化酶等指标,结果显示老化前超干种子与未超干种子各项指标无明显差异,老化后超干处理的菊苣种子的发芽率、活力指数、脱氢酶、过氧化物酶和过氧化氢酶均高于对照,电导率、丙二醛含量低于对照,在超干种子中含水量为2.33%时贮藏效果优于其他含水量的种子。表明适度含水量的超干处理可以使菊苣种子保持较高的活力,提高了其耐贮藏性,为探讨菊苣种子的适宜贮藏方法提供依据。 相似文献
17.
近年来，少花蒺藜草（Cenchrus pauciflorus）的发生面积逐年增加，给当地农牧业生产带来严重危害。本文综述了少花蒺藜草入侵现状、适应机制和防控策略的相关研究，并展望了该领域未来应着重考虑的科学问题。受农作措施和干扰的影响，不同生境少花蒺藜草的土壤种子库的差异较大。自然状态下，水热条件、种子类型、盐胁迫和干旱胁迫是少花蒺藜种子萌发的限制因素，土壤质地和埋种深度对种子萌发几乎无影响。少花蒺藜草具有较强的表型可塑性，生活周期与降雨期高度吻合和对光能的高效利用使其在较短的时间内完成生活史。生物防控、机械防除和化学药剂防除是少花蒺藜草的主要防控方式，但每种方式适用的生境不同。少花蒺藜草对降水与氮沉降的响应和表型可塑性的调控机理、对胁迫和干扰的响应机制，以及探索不同生境少花蒺藜草的科学防控方法在未来研究应优先考虑。 相似文献
18.
Giardia duodenalis and Cryptosporidium spp. are intestinal protozoan parasites that infect a wide range of host species, including humans. Molecular characterization of these parasites has demonstrated that a number of genotypes and species are common to both humans and animals, and that zoonotic transmission may occur. Numerous studies have reported a high prevalence of G. duodenalis and Cryptosporidium spp. in cattle, particularly calves, and these animals are frequently associated with zoonotic transmission. In the present study, a total of 143 faecal samples from adults, heifers and calves were collected from two dairy cattle farms in eastern Ontario, Canada. The prevalence and molecular characteristics of G. duodenalis and Cryptosporidium spp. in these animals were determined in order to investigate the potential for transmission between cattle and humans in this region. Following DNA extractions from faecal samples, nested-PCR protocols were used to amplify fragments of the 16S rRNA gene and the heat-shock protein 70 (HSP-70) gene for determining the prevalence of G. duodenalis and Cryptosporidium spp. infections, respectively. Genotypes of G. duodenalis, and species of Cryptosporidium, were determined by means of DNA sequencing of amplicons, and subsequent sequence alignment. Cattle on both farms showed a high prevalence of G. duodenalis (42.0%) and Cryptosporidium spp. (27.3%). G. duodenalis infections were more prevalent in calves and heifers than in adults, and Cryptosporidium spp. infections were only observed in calves and heifers. The zoonotic genotype, G. duodenalis Assemblage B was isolated from 24.5% of the cattle tested, while G. duodenalis Assemblage E was found in 17.5% of the cattle tested. The overall prevalence of the zoonotic species Cryptosporidium parvum in the animals tested was found to be 21.7%, while only 1.4% were infected with C. bovis. These findings suggest that there is a potential risk of zoonotic and/or zooanthroponotic transmission of G. duodenalis and C. parvum infections between cattle and humans in eastern Ontario, likely by means of contaminated water or food, or through direct faecal-oral transmission in the case of farmers and veterinary staff. 相似文献
19.
内蒙古典型草原小叶锦鸡儿灌丛地上净初级生产力和种群结构对火烧的响应 总被引：3，自引：1，他引：2
针对全球范围内由于长期过度放牧引起的草原群落灌丛化问题,本研究以内蒙古锡林河流域小叶锦鸡儿灌丛化的羊草草原为研究对象,通过连续2年的人为控制火烧实验,从株丛和群落2个组织水平研究了火烧对小叶锦鸡儿的影响。结果表明,1)在内蒙古锡林河流域的退化恢复草原群落中,小叶锦鸡儿种群属于增长型的种群,中、小株丛所占的比例较大。实验区内所调查的6588个株丛中,冠幅为0～50cm的株丛占30%,50～150cm的株丛占49%,>150cm的株丛仅占21%;2)在群落水平上,一年火烧和连续2年火烧对小叶锦鸡儿株丛的生长均具有显著的抑制作用,其地上净初级生产力比火烧前分别减少了27%和66%;3)火烧显著地增加了小叶锦鸡儿的枝条密度和茎的生物量分配,减少了叶的生物量分配,使茎叶比由1∶4.4升高为1∶1.1;4)同50～150和>150cm2个冠幅组的大株丛相比,火烧对0～50cm小灌丛影响最为明显,一年火烧和连续2年火烧使其地上净生物量分别下降了57%和60%。实验结果表明,火烧显著地削弱了小叶锦鸡儿的生活力,有效地抑制了其小株丛的生长,对控制灌丛的进一步扩张具有明显的作用。 相似文献
20.
蒙古莸(Caryopteris mongolica)是干旱半干旱区具有较高经济价值和生态价值的小灌木,其地理分布范围日渐缩小,成为濒危植物。为了探究蒙古莸地理分布格局形成演化过程,以蒙古莸49个分布点的环境因子数据为变量,通过建立MaxEnt生态位模型,探明影响蒙古莸地理分布的主要环境因子,模拟蒙古莸在当代和未来的潜在地理分布,结果表明：最冷季度降水量、最冷季度平均温、年平均气温、季节性降水量变异系数是影响蒙古莸分布的主要生态因子;适宜蒙古莸存活的年平均气温为2.26℃～8.90℃,最干季度平均温为-15.31℃～-5.02℃,最冷季度降水量为1.42～9.97 mm;未来气候变化条件下,蒙古莸潜在分布区面积呈增加趋势;蒙古莸分布核心区域的变化受到年均降水量和温度影响,在RCP 4.5气候变化情景下向北迁移。RCP 8.5气候变化情景下先向东北方向迁移之后沿原途径返回。 相似文献