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1.
流感病毒的血凝素(HA)与宿主细胞表面糖链末端唾液酸(SA)的结合对流感病毒感染宿主起着至关重要的作用。禽流感病毒对SAα2-3Galβ糖链以及人流感病毒对SAα2-6Galβ糖链的结合特异性使跨种属传播受阻,但不同的流感病毒在猪和陆地家禽等中间宿主体内发生基因重配作用后,可使部分禽流感病毒获得适应性感染人的能力,另一方面,流感病毒自身的基因突变,尤其是受体结合部位周围的特定位点,可导致流感病毒受体结合特异性发生转变,而病毒的变异伴随着自身糖修饰和抗原表位的改变,使机体对其免疫识别结合的能力也随之发生变化。这些分子水平的改变都将对病毒相关的宿主受体结合和免疫应答反应产生影响。  相似文献   

2.
HA蛋白位点变异影响H7N9亚型流感病毒特性的研究进展   总被引：2，自引：2，他引：0  
2013年春，我国首次出现人感染H7N9亚型禽流感疫情，对家禽养殖和公众健康均产生了严重危害，并且在第5波流行期又演变出血凝素（hemagglutinin，HA）蛋白裂解位点处存在插入突变的高致病性禽流感病毒株。HA作为A型流感病毒表面表达丰度最高的糖蛋白，在介导病毒与宿主细胞表面受体的结合、促进病毒囊膜与细胞膜的融合、刺激机体产生中和抗体等方面具有至关重要的作用。本文围绕H7N9病毒，简要综述了HA蛋白的结构与功能，及其关键功能氨基酸位点变异影响病毒生物学特性的研究进展，以期为深入解析HA蛋白在H7N9病毒感染致病中的作用提供重要参考。  相似文献   

3.
禽流感综述及其危机   总被引：2，自引：0，他引：2  
禽流感病毒的HA和NA都容易发生抗原漂移和抗原转换,有可能突变出快速感染人类并致病的亚型,特别是H5N1具有从其它感染动物种属的流感病毒中获得基因并转变迅速的能力,使人类健康面临重大威胁。本文就禽流感的病毒学特征,微观的机理及其防治还有鸟类迁徙对其全球范围的传播的影响进行了综述。1禽流感病毒1.1禽流感病毒的生物学性状禽流感(Avian influenza),俗称鸡瘟。历史上最早记载是1878年在意大利发生的鸡群大量死亡。其致病原直到1955年才被科学家证实为甲型流感病毒,这种疾病随后命名为禽流感[1]。流感病毒,隶属ss-RNA负链病毒目正…  相似文献   

4.
禽流感病毒不断重排和变异导致新型流感病毒不断出现,其中有些毒株已经获得了感染哺乳动物的能力,严重危害人类公共卫生安全。近年来,对于禽流感病毒致宿主特异性和致病性的研究取得了一定进展。病毒蛋白某些氨基酸位点的突变就能够改变病毒的宿主特异性,使病毒能够跨宿主传播。而且,病毒的RNA聚合酶、NS1非结构蛋白和几种新发现的病毒蛋白都与病毒的致病性密切相关。论文阐述了禽流感病毒宿主特异性与致病性的分子基础,为禽流感跨物种传播机制研究及防控工作提供参考。  相似文献   

5.
最近,关于禽流感病毒如何与人的受体结合并感染人的研究又取得了新的进展。据美国庥省理工学院的科学家2008年1月6日表示,他们发现了感染禽类的病毒和感染人类的病毒之间存在的关键性差别。对于感染人类的病毒,其感染能力取决于人类呼吸系统细胞表面受体是否有能够同病毒结合的特定形状。这项新的研究更详细地揭示出,正是由于流感病毒与特定的α-2,6半乳糖受体的特定形状结合的能力,决定了它是否能够感染人类。α-2,6半乳糖受体有两种形状——其中一种类似于伞形,另一种类似于圆锥。研究发现,流感病毒如果要感染人类,它们必须与伞形的α-2,6半乳糖受体结合。文中指出,虽然禽流感病毒通过家禽适应人并变为人传人需要一个过程,但是,这种演变进化的适应过程似乎有加快脚步的迹象。2007年10月4日,美国威斯康星——麦迪逊大学的一位科学家说：“我们已经检测到禽流感病毒的一种特殊变异,它能使病毒适应人类上呼吸道的生存环境”,也就是说,新的变异让H5N1型禽流感病毒能够在更低的温度下存活。尽管还没有转变为可以在人类间传播的病毒,但至少可以表明,H5N1型禽流感病毒正在向这个方向演变进化。这对人类是一个危险的信号。  相似文献   

6.
目前临床所用控制流感病毒的药物和疫苗受到病毒耐药性、疫苗滞后性等诸多因素的限制,使能阻止病毒侵入宿主细胞的抑制剂成为当前研究的热点。唾液酸是流感病毒囊膜表面血凝素（HA）的受体,但研究表明唾液酸并不适合作为研制流感病毒侵入宿主细胞抑制剂的结构模型。研究发现流感病毒的HA 受体结合位点必须外露才能与宿主细胞受体结合,因此 HA 受体结合位点可以被宿主免疫系统监视,成为抗体潜在的靶向契合位点。随后发现的 HA 受体结合位点抗体能与 HA 受体结合位点的保守氨基酸残基结合,能有效阻止流感病毒感染宿主。因此,可用 HA 受体结合位点抗体作为流感病毒感染抑制剂的模型,研制流感病毒抑制剂。论文就流感病毒 HA 的分子结构和功能,HA 结合受体的机制,HA 受体结合位点抗体以及该类抗体对流感病毒的抑制效果进行了阐述,以期对以 HA 受体结合位点抗体为模型研制流感病毒感染抑制剂提供帮助。  相似文献   

7.
基于2008~2012年我国及周边国家禽流感病毒血凝素(HA)核酸在线BLAST,及MEGA5.1Bate4选取病案样本比对等方法,对我国与周边国家(地区)H5N1亚型禽流感病毒血凝素演变进行了研究。结果显示,各样本均具有与禽受体特异性结合的特性,但部分样本在对病毒受体结合特异性有影响的位点发生氨基酸替换,2010年和2011年我国家禽和人样本HA抗原表位关键位点氨基酸与参考疫苗有较大变异,部分样本与中国香港和越南野鸟样本抗原匹配较高;回顾性分析表明,我国人和家禽在面临原有病毒株感染的同时增加了感染境外来源病毒株和中国香港、青海野鸟毒株的风险,应加强对H5N1亚型禽流感病毒变异和境外毒株向我国境内传播的监测,及时研制新的疫苗以应对新毒株类型。  相似文献   

8.
自1997年以来,发现H5 N1、H9N2、H7N7亚型的禽流感病毒都能感染人。通常认为禽流感病毒在人体内复制受细胞受体和呼吸道细胞外抑制物的限制,但其确切机制却还不清楚。最近,科学家通过体外培养不同的人呼吸道上皮细胞,发现人流感病毒和禽流感病毒分别感染不同的靶细胞。在单周期感染(single- cycle infection)过程中,人流感病毒主要感染无纤毛细胞(non-ciliated cells) ,而禽流感病毒和在鸡胚适应的具有禽流感病毒样受体特异性的人流感病毒主要感染有纤毛的细胞,这与无纤毛细胞上主要有人流感病毒受体(2 - 6位交联的唾液酸) ,有纤毛细胞上…  相似文献   

9.
为研究两株H7亚型流感病毒A/chicken/Jilin/SD020/2014(H7N2)(简称JL/020)和A/Anhui/1/2013(H7N9)(简称AH/1)受体结合特异性差异的影响机制,本实验利用反向遗传操作技术,构建一系列重配病毒和HA基因点突变病毒,检测其对受体结合特性的影响。固相ELISA检测结果表明血凝素蛋白(HA)中的57和312位氨基酸不影响流感病毒的受体结合特性,而神经氨酸酶蛋白(NA)使r-JL/020(AH/1骨架)结合SAα2,3Gal受体的结合能力高于r-AH/1(R57K/R312K),表明NA影响了流感病毒受体结合特性;同源建模进一步发现HA中的57和312位点与流感病毒受体结合结构域相距较远;交叉血凝抑制试验(HI)结果表明,H7单因子血清和H7N9全病毒血清对拯救的JL/020和AH/1病毒株的抑制价没有差异,而N2单因子血清对病毒的抑制能力存在差异。以上结果表明,NA蛋白影响了流感病毒的受体结合特性。本研究表明,除HA以外,NA也能够影响流感病毒的受体结合特性,该实验为进一步研究流感病毒受体结合特性提供了实验依据。  相似文献   

10.
禽流感病毒(Avian influenza virus,AIV)属于正黏病毒科(Orthomyxoviridae),A型流感病毒属(Influenzavirus A)。禽流感至今仍无法有效控制的主要原因是其表面蛋白极易发生变异。而基因的变异往往会引起病毒的抗原发生改变,从而产生新的毒株。文章从禽流感病毒抗原变异的方式,禽流感病毒抗原变异与宿主免疫状态的关系,以及变异后流感病毒受体结合发生改变等方面归纳了禽流感病毒抗原变异的机制和影响。  相似文献   

11.
试验选用96头平均体重14.82 kg左右的杜×长×大断奶仔猪,随机分成4组,每组3栏,每栏8头(公母各半)。对照组饲喂基础日粮,试验1、2、3组分别添加1%80目白术、0.2%白术多糖和1%微米白术。试验期30 d。结果表明:在生长性能方面,与对照组相比,1%微米白术添加组可显著提高日增重(P0.05)、降低饲料增重比和腹泻率,而且效果优于1%80目白术组和0.2%白术多糖组,在肠道形态和肠道微生态区系方面,与对照组相比,日粮添加1%80目白术、0.2%白术多糖、1%微米白术均可不同程度的提高十二指肠和空肠的绒毛高度,加深十二指肠和空肠的隐窝深度,并且增加肠道微生态区系的多样性,其中以1%微米白术添加组的效果最佳。  相似文献   

12.
Sissay, M.M., Uggla, A. and Waller, P.J., XXXX. Prevalence and seasonal incidence of nematode parasites and fluke infections of sheep and goats in eastern Ethiopia. Tropical Animal Health and Production, XXXX. A 2-year abattoir survey was carried out to determine the prevalence, abundance and seasonal incidence of gastro-intestinal (GI) nematodes and trematodes (flukes) of sheep and goats in the semi-arid zone of eastern Ethiopia. During May 2003 to April 2005, viscera including liver, lungs and GI tracts were collected from 655 sheep and 632 goats slaughtered at 4 abattoirs located in the towns of Haramaya, Harar, Dire Dawa and Jijiga in eastern Ethiopia. All animals were raised in the farming areas located within the community boundaries for each town. Collected materials were transported within 24 h to the parasitology laboratory of Haramaya University for immediate processing. Thirteen species belonging to 9 genera of GI nematodes (Haemonchus contortus, Trichostrongylus axei, T. colubriformis, T. vitrinus, Nematodirus filicollis, N. spathiger, Oesophagostomum columbianum, O. venulosum, Strongyloides papillosus, Bunostomum trigonocephalum, Trichuris ovis, Cooperia curticei and Chabertia ovina), and 4 species belonging to 3 genera of trematodes (Fasciola hepatica, F. gigantica, Paramphistomum {Calicohoron} microbothrium and Dicrocoelium dendriticum) were recorded in both sheep and goats. All animals in this investigation were infected with multiple species to varying degrees. The mean burdens of adult nematodes were generally moderate in both sheep and goats and showed patterns of seasonal abundance that corresponded with the bi-modal annual rainfall pattern, with highest burdens around the middle of the rainy season. In both sheep and goats there were significant differences in the mean worm burdens and abundance of the different nematode species between the four geographic locations, with worm burdens in the Haramaya and Harar areas greater than those observed in the Dire Dawa and Jijiga locations. Similar seasonal variations were also observed in the prevalence of flukes. But there were no significant differences in the prevalence of each fluke species between the four locations. Overall, the results showed that Haemonchus, Trichostrongylus, Nematodirus, Oesophagostomum, Fasciola and Paramphistomum species were the most abundant helminth parasites of sheep and goats in eastern Ethiopia.  相似文献   

13.
Tropical Animal Health and Production -  相似文献   

14.
1-(2-Chloroethyl)3-cyclohexyl-1-nitrosourea (CCNU) is an alkylating agent in the nitrosourea subclass. A prospective evaluation of CCNU was done to determine the maximally tolerated dosage of CCNU in tumor-bearing cats. Response data were obtained when available. Twenty-five cats were treated with CCNU at a dosage of 50-60 mg/m3 body surface area. Complete hematologic data were available for 13 cats. Neutropenia was the acute dose-limiting toxicity. The median neutrophil count at the nadir was 1,000 cells/microL (mean, 2,433 cells/microL; range, 0-9,694 cells/microL). The time of neutrophil nadir was variable, occurring 7-28 days after treatment, and counts sometimes did not return to normal for up to 14 days after the nadir. Based on these findings, a 6-week dosing interval and weekly hematologic monitoring after the 1st treatment with CCNU are recommended. The nadir of the platelet count may occur 14-21 days after treatment. The median platelet count at the nadir was 43,500 cells/microL. No gastrointestinal, renal, or hepatic toxicities were observed after a single CCNU treatment, and additional studies to evaluate the potential for cumulative toxicity should be performed. Five cats with lymphoma and 1 cat with mast cell tumor had measurable responses to CCNU. Phase II studies to evaluate antitumor activity should be completed with a dosing regimen of 50-60 mg/m3 every 6 weeks.  相似文献   

15.
Our particular attention in this article was given to natural mediators for macrophages isolated from the sites of tissue injury. A number of chemotactic factors, which may satisfy many criteria making them acceptable as inflammatory leucocyte chemotactic factors, has been separated. Among them, our laboratory has isolated three macrophage (monocyte) chemotactic factors (MCF-a, -b and -c). Their purification, characterization and functional specificity are discussed.  相似文献   

16.
Genetic variations in chromosome Y are enabling researchers to identify paternal lineages, which are informative for introgressions and migrations. In this study, the male‐specific region markers, sex‐determining region‐Y (SRY), amelogenin (AMELY) and zinc finger (ZFY) were analysed in seven Turkish native goat breeds, Angora, Kilis, Hair, Honaml?, Norduz, Gürcü and Abaza. A SNP in the ZFY gene defined a new haplotype Y2C. All domestic haplogroups originate from Capra aegagrus, while the finding of Y1A, Y1B, Y2A and Y2C in 32, 4, 126 and 2 Turkish domestic goats, respectively, appears to indicate a predomestic origin of the major haplotypes. The occurrence of four haplotypes in the Hair goat and, in contrast, a frequency of 96% of Y1A in the Kilis breed illustrate that Y‐chromosomal variants have a more breed‐dependent distribution than mitochondrial or autosomal DNA. This probably reflects male founder effects, but a role in adaptation cannot be excluded.  相似文献   

17.
Human and equine athletes are reported to have a high prevalence of gastric disease, and anecdotal evidence suggests a similar phenomenon applies to racing sled dogs. To investigate the prevalence of gastric disease in racing sled dogs, we conducted 2 gastroscopy studies on dogs competing in the annual Iditarod Sled Dog Race. A pilot study of dogs that were either dropped from the 2000 Iditarod Sled Dog Race because of illness or that finished the race indicated that, approximately 5 days after competing, 10 of 28 dogs (35%) had endoscopic evidence of gastric ulceration, erosion, or hemorrhage. The next year, an endoscopic study of 73 dogs participating in the 2001 Iditarod race was performed in order to evaluate a larger population of dogs. Data from 70 of these dogs could be used; 34 (48.5%) had ulceration, erosion, gastric hemorrhage, or some combination of these findings. When this group of 70 dogs was compared retrospectively to a control group of 87 dogs presented to the Texas A&M University (TAMU) Veterinary Medical Teaching Hospital, the Iditarod sled dogs had a significantly higher prevalence (P = .049) of gastric lesions. These findings suggest that, similar to athletes of other species, elite canine athletes have an increased prevalence of gastric disease compared to the canine population at large.  相似文献   

18.
Continuous rate infusion (CRI) of furosemide in humans is considered superior to intermittent administration (IA). This study examined whether furosemide CRI, compared with IA, would increase diuretic efficacy with decreased fluid and electrolyte fluctuations and activation of the renin-angiotensin-aldosterone system (RAAS) in the horse. Five mares were used in a crossover-design study. During a 24-hour period, each horse received a total of 3 mg/kg furosemide by either CRI (0.12 mg/kg/h preceded by a loading dose of 0.12 mg/kg IV) or IA (1 mg/kg IV q8h). There was not a statistically significant difference in urine volume over 24 hours between methods; however, urine volume was significantly greater after CRI compared with IA during the first 8 hours ([median 25th percentile, 75th percentile]: 9.6 L [8.9, 14.4] for CRI versus 5.9 L [5.3, 6.0] for IA). CRI produced a more uniform urine flow, decreased fluctuations in plasma volume, and suppressed renal concentrating ability throughout the infusion period. Potassium, Ca, and Cl excretion was greater during CRI than IA (1,133 mmol [1.110, 1,229] versus 764 mmol [709, 904], 102.7 mmol [96.0, 117.2] versus 73.3 mmol [65.0, 73.5], and 1,776 mmol [1,657, 2.378] versus 1,596 mmol [1,457, 1,767], respectively). Elimination half-lives of furosemide were 1.35 and 0.47 hours for CRI and IA, respectively. The area under the excretion rate curve was 1,285.7 and 184.2 mL x mg/mL for CRI and IA, respectively. Furosemide CRI (0.12 mg/kg/h) for 8 hours, preceded by a loading dose (0.12 mg/kg), is recommended when profound diuresis is needed acutely in horses.  相似文献   

19.
The objective of this report was to characterize 20-year changes in proportion of calcium oxalate (CaOx) calculi and struvite calculi in dogs, and associations with breed, age, and sex. In this retrospective study, results of analysis of urinary calculi from dogs were reviewed for specimens received between July 1, 1981, and December 31, 2001. Breed, sex, age, year of submission of the specimen, and mineral type(s) were analyzed statistically. CaOx or Struvite or both were contained in 18,966 of 20,884 (91%) specimens. For both sexes, a 20-year statistically significant increase was observed in the proportion of calculus specimens that contained CaOx. The increase in this proportion was greater in females (1% to 31%) than in males (18% to 82%). From 1998 to 2001, when proportions may have plateaued, the odds of specimens containing CaOx were markedly higher in 18 breeds, markedly lower in 5 breeds, and not significantly different in 13 breeds compared with crossbreds. For both sexes, a 20-year statistically significant decrease was observed in the proportion of calculus specimens that contained struvite. This decrease in proportion was greater for males (79-16%) than for females (97-68%). From 1998 to 2001, when proportions plateaued, the odds of calculi containing struvite were markedly lower in 20 breeds, markedly higher in 1 breed, and not significantly different in 15 breeds when compared with crossbreds. Breed, age, and sex were associated statistically with CaOx or struvite urolithiasis. In conclusion, there appears to have been a long-term increase in the proportion of specimens of canine urinary calculi that contain CaOx as well as a long-term decrease in the proportion of specimens of calculi that contain struvite for both male and female dogs. The rate of change appeared to begin leveling off in the period 1998 to 2001. The recent proportion of dogs with either CaOx- or struvite-associated urolithiasis may depend on breed, age, and sex, and on interactions among these 3 factors.  相似文献   

20.
<正>1.INTRODUCTION Ensuring transportation network security is one Of the most daunting challenges confronting homeland security agencies today.Significant research has been dedicated.To model and analyze the vulnerability of transportation systems,while notably fewer studies propose specific strategies for deploying defensive technologies to safeguard these systems.  相似文献   

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