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1.
疟原虫裂殖子入侵红细胞是在受体介导下完成的,目前研究较多的是恶性疟和间日疟受体。一般认为,恶性疟原虫裂殖子受体主要是红细胞膜上的血型蛋白A(GPA),GPA分子中的NeuNAC、GleNAc以及T1和T6结构均可能参与其活性中心的组成。Duffy血型抗原可能作为间日疟原虫裂殖子受体,但至今对其化学本质的了解远不如GPA清楚,又由于间日疟原虫在体外培养未获成功,故对间日疟原虫受体及其活性中心的研究进  相似文献   

2.
中华血簇虫在其无脊椎动物寄主中的发育已另有文描述。这里报道的是中华血簇虫在中华鳖中的发育。这一时期包括三个阶段:组织细胞内裂体增殖、深部血红细胞内的裂体增殖和外周血红细胞内的裂体增殖。组织细胞内裂殖体产生14—32个裂殖子。深部血红细胞内的裂殖体分为两类:一类是X裂殖体,它产生14—18个小裂殖子;另一类是Y裂殖体,它产生4—6个大裂殖子。外周血红细胞内的初期裂殖体可产生多至14个裂殖子,而随后的裂体增殖却产生越来越少的裂殖子,且裂殖体和裂殖子的大小也渐趋变小。外周血晚期的裂殖体只形成2个裂殖子。配子母细胞来源于Y裂殖子。营养体是由上一代裂殖子向下一代裂殖体发育的中间时期。  相似文献   

3.
入侵疟原虫与红细胞膜的相互作用   总被引:1,自引:0,他引:1  
疟疾是广泛传播的人类严重寄生虫病。近十年来,从分子水平探索疟疾的发病机制和治疗、预防手段都取得了可喜的进展,尤其恶性疟原虫全基因组的成功测序为疟疾疫苗的设计和试制开拓了新途径。该文就疟原虫裂殖子入侵红细胞表面过程的生化背景,裂殖子与红细胞的配体-受体相互作用,疟原虫向红细胞输出的蛋白质,以及疟疾感染所致红细胞的遗传障碍等方面的近期有关报道作一简介,试图从细胞与分子机制讨论被感染红细胞的膜蛋白与膜骨架的某些改变。  相似文献   

4.
疟疾是疟原虫通过雌性按蚊为媒介传播的寄生虫病,是当今世界公共卫生的突出问题.寄生于人体的疟原虫主要包括恶性疟原虫、间日疟原虫、三日疟原虫、卵形疟原虫和诺氏疟原虫5种,其中,恶性疟原虫的致病性最为强烈,是导致全球疟疾发病和死亡的重要病原体.硫化肝素是广泛分布于脊椎动物细胞表面的无支链多糖,为疟原虫入侵宿主红细胞的一个重要受体,在疟原虫入侵过程中发挥着重要的作用.疟原虫入侵宿主红细胞是一个快速而复杂的过程,恶性疟原虫入侵相关蛋白质在疟原虫入侵过程中具有重要的作用,主要参与黏附宿主红细胞、形成移动连接复合体、形成和修饰纳虫空泡等过程.黏附是恶性疟原虫入侵宿主红细胞的第一步,入侵相关蛋白质与宿主红细胞表面硫化肝素受体结合,继而完成后续的入侵.综合国内外文献,本文围绕肝素/硫化肝素在治疗恶性疟疾中的应用、与恶性疟原虫入侵相关蛋白质的结合以及恶性疟原虫入侵相关蛋白质在裂殖子入侵宿主红细胞过程中的作用机制等研究方面进行综述,为恶性疟原虫入侵过程中相关蛋白质与肝素结合的分子机制提供理论依据,同时也为新型抗疟药物和疫苗的研制以及治疗提供参考.  相似文献   

5.
在疟疾免疫学研究中,为了制备裂殖子抗原,需要从感染血中分离出裂殖体期疟原虫昕寄生的红细胞,并对其进行短期培养,以收集细胞外的游离裂殖子。我们借用木下喜博用阿拉伯胶液密度梯度离心分离淋巴细胞的方法,分离诺氏疟原虫裂殖体期感染的红细胞。获得了一些初步结果。  相似文献   

6.
在体外培养的牛外周血白细胞中,环形泰勒焦虫裂殖子与裂殖体寄生于宿主细胞的细胞质中,并且随着宿主细胞的分裂而分到两个子细胞中。焦虫染色质粒的分裂方式为二分裂,随着焦虫颗粒的不断增殖,逐渐发育为成熟的裂殖体。体外培养感染焦虫的牛白细胞可通过伪足与细胞裂解两种途径向培养液中释放焦虫颗粒。释放到培养液中的焦虫颗粒对体外培养的健康牛外周血白细胞具有感染能力,感染细胞能在体外连续传代培养。  相似文献   

7.
贝氏隐孢子虫在北京鸭体内发育的超微结构研究   总被引:11,自引:1,他引:10  
贝氏隐孢子虫各期虫体均位于宿主粘膜上皮细胞的带虫空泡中。在虫体与上皮细胞接触处,虫体表膜反复折迭形成营养器。子孢子或裂殖子与粘膜上皮细胞接触后,逐步过渡为球形的滋养体;滋养体经2—3次核分裂、产生含4或8个裂殖子的两代裂殖体,裂殖体以外出芽方式产生裂殖子;裂殖子无微孔,顶端表皮形成3—4个环嵴,裂殖子进一步发育成为配子体;大配子体含有两种类型的成囊体。小配子呈楔形,无鞭毛和顶体,有一个致密的长椭圆形细胞核,小配子表膜内侧有9根膜下微管;孢子化卵囊内含四个裸露的子孢子和一个大残体。本文是有关鸭体内隐孢子虫超微结构的首次报导。  相似文献   

8.
张龙现  宁长申  蒋金书 《动物学研究》2001,22(6):511-515,T001
取 2日龄海兰雏鸡 5 0只 ,分为 5组 ,分别接种 0、 0 8× 10 6、 1 6× 10 6、 3 2× 10 6、 6 4× 10 6个鸭源贝氏隐孢子虫 (Cryptosporidiumbaileyi)卵囊。接种后在不同的时间间隔内剖杀雏鸡 ,取法氏囊、气管和喉头。扫描电镜观察发现贝氏隐孢子虫主要寄生在鸡的喉头、法氏囊、气管。裂殖体有 2种类型 :Ⅰ型裂殖体含 8个裂殖子 ,Ⅱ型裂殖体含 4个裂殖子。子孢子或裂殖子在钻入过程中 ,虫体逐渐由香蕉形过渡到鼓槌形 ,最后形成球形的滋养体。带虫空泡分为有球形残体的带虫空泡和无球形残体的带虫空泡。观察到小配子的释放和虫体寄生于杯状细胞的现象。贝氏隐孢子虫寄生于气管引起纤毛倒伏、排列紊乱、纤毛融合、脱落 ;致使法氏囊上皮肿胀 ,法氏囊粘膜表面形成皱褶 ,微绒毛脱落、融合、排列紊乱 ,粘液性分泌物增多 ,炎性细胞渗出  相似文献   

9.
利用透射电镜对寄生于北京鸭小肠的毁灭泰泽球虫的裂殖生殖过程进行了观察。滋养体内未见多糖颗粒、脂肪体和致密体,在细胞质的被膜空泡内发现退化的微线和棒状体。在裂殖体核分裂过程中,出现典型的球虫型有丝分裂装置(如中心粒、中心锥、纺锤体)。裂殖子的发生是外瓣生方式,裂殖子在裂殖体的表面形成,并以母细胞的限制膜为外膜。  相似文献   

10.
作者利用致乏库蚊(Culex fatigans)作为实验媒介,把寄生在灰鼠蛇(Ptyas korros)的广东肝血簇虫(Hepatozoon guangdongensis)感染到无虫的灰鼠蛇(渔游蛇(Natrix piscator)、三索锦蛇(Elaphe radita)和中国水蛇(Enhydris chinesis);观察其生活史。首次描述了由x裂殖体产生的小裂殖子,进入红细胞,经滋养体和幼小配子母体阶段发育成配子母体的过程,以及由y裂殖体产生的大裂殖子继续在内脏进行无性生殖的细节;在对广东肝血簇虫生活史进行研究的基础上,提出一种新的肝血簇虫在脊椎动物体内发育的模式和血液时期各期虫体划分的形态学标准。  相似文献   

11.
Invasion of erythrocytes by malaria parasites is known to be blocked by proteolytic digestion of merozoite receptors allegedly present in red cell membranes. This information was used in the present work to develop a simple and convenient assay for parasite invasion into red blood cells and for evaluating the role played by red cell membrane components in this process. Synchronized in vitro cultures of Plasmodium falciparum containing only ring stages were subjected to either trypsin or pronase digestion, a treatment that neither affected ring development into schizonts nor mature merozoite release. Cells from this culture were not invaded by the released merozoites. However, upon addition of untreated human red blood cells, marked invasion was observed, either microscopically or as [3H]isoleucine incorporation. The new assay circumvents the need for separating schizonts from uninfected cells and provides a convenient means for assessing how chemical and biochemical manipulation of red blood cells affects their invasiveness by parasites. Using this assay, we verified that sheep and rabbit erythrocytes were resistant to invasion, as were human erythrocytes which had been treated with trypsin, pronase or neuraminidase. Chymotrypsin digestion of human erythrocytes was without effect on invasion. Human erythrocytes which were chemically modified with the impermeant amino reactive reagent H2DIDS, or with the crosslinker of spectrin, TCEA, were found to resist invasion. The results underscore the involvement of surface membrane components as well as of elements of the cytoskeleton in the process of parasite invasion into erythrocytes.  相似文献   

12.
Invasion of erythrocytes by malaria parasites is known to be blocked by proteolytic digestion of merozoite receptors allegedly present in red cell membranes. This information was used in the present work to develop a simple and convenient assay for parasite invasion into red blood cells and for evaluating the role played by red cell membrane components in this process. Synchronized in vitro cultures of Plasmodium falciparum containing only ring stages were subjected to either trypsin or pronase digestion, a treatment that neither affected ring development into schizonts nor mature merozoite release. Cells from this culture were not invaded by the released merozoites. However, upon addition of untreated human red blood cells, marked invasion was observed, either microscopically or as [3H]isoleucine incorporation. The new assay circumvents the need for separating schizonts from uninfected cells and provides a convenient means for assessing how chemical and biochemical manipulation of red blood cells affects their invasiveness by parasites. Using this assay, we verified that sheep and rabbit erythrocytes were resistant to invasion, as were human erythrocytes which had been treated with trypsin, pronase or neuraminidase. Chymotrypsin digestion of human erythrocytes was without effect on invasion. Human erythrocytes which were chemically modified with the impermeant amino reactive reagent H2DIDS, or with the crosslinker of spectrin, TCEA, were found to resist invasion. The results underscore the involvement of surface membrane components as well as of elements of the cytoskeleton in the process of parasite invasion into erythrocytes.  相似文献   

13.
Babesia bovis merozoites, externalized by removal of infected erythrocytes from ordinary culture conditions, were completely separated from red blood cells and stroma by centrifugation in a Percoll gradient. A merozoite band formed at a point corresponding to about 1.087 g/ml specific density. Infected red blood cells were concentrated approximately fourfold to obtain greater than 49.0% parasitemia after centrifugation in Percoll. Most highly enriched fractions positioned between 1.121 and 1.123 g/ml specific density. Full parasite viability was retained.  相似文献   

14.
J Schrével  A Deguercy  R Mayer  M Monsigny 《Blood cells》1990,16(2-3):563-84; discussion 585-90
The discrimination between erythrocyte and Plasmodium proteases is now made easier by using synthetic fluorogenic substrates, high-pressure liquid chromatography, reliable methods of cell preparation, as well as radiolabeled extracts from in vitro cultures of P. falciparum. The reinvasion process of an erythrocyte by a merozoite involves specific proteinases, which were recently identified using fluorogenic peptidyl-AEC substrates and by analysis of schizont and merozoite extracts with the gelatin-SDS-PAGE method. The biological targets of both host and parasite proteinases are not yet well characterized because Plasmodium-infected red blood cells contain at least four compartments with different pH values, which could modulate the proteinase activities according to their pH range activity. The processing of the precursor for the major merozoite surface antigens involves cleavage of very specific peptidic bonds by, so far unknown, proteinases. The depletion of the erythrocyte cytoskeleton could depend on a 37 kD proteinase, which cleaves spectrin and the 4.1 component, as shown in P. berghei and P. falciparum species. In contrast to leupeptin, which inhibits the merozoite release from schizont-infected erythrocytes, the structural inhibitor analogous to the Val-Leu-Gly-Lys (or Arg) P. falciparum neutral proteinase substrates appears to block the invasion step of erythrocytes by merozoites and may open new trends in chemotherapeutical strategies.  相似文献   

15.
We describe how to obtain an increased merozoite invasion of Plasmodium falciparum into human erythrocytes during short periods of time. Using this procedure, infected erythrocytes show multiple invasions (2-4 merozoites per erythrocyte), amplifying, several times, the effects of parasite entry into host cells. The procedure yields synchronous cultures (2-h age range) with parasitemia as high as 15%. It is possible to reach parasitemia of 50% or higher allowing for a 6-h invasion period.  相似文献   

16.
17.
Plasmodium malaria parasites multiply within erythrocytes and possess a repertoire of proteins whose function is to recognize and invade these vertebrate host cells. One such protein involved in erythrocyte invasion is the micronemal protein, Erythrocyte Binding-Like (EBL), which has been studied as a potential target of vaccine development in Plasmodium vivax (PvDBP) and Plasmodium falciparum (EBA-175). In the rodent malaria parasite model Plasmodium yoelii, specific substitutions in the EBL regions responsible for intracellular trafficking (17XL parasite line) or receptor recognition (17X1.1pp. parasite line), paradoxically increase invasion ability and virulence rather than abolish EBL function. Attempts to disrupt the ebl gene locus in the 17XL and 17XNL lines were unsuccessful, suggesting EBL essentiality. To understand the mechanisms behind these potentially conflicting outcomes, we generated 17XL-based transfectants in which ebl expression is suppressed with anhydrotetracycline (ATc) and investigated merozoite behavior during erythrocyte invasion. In the absence of ATc, EBL was secreted to the merozoite surface, whereas following ATc administration parasitemia was negligible in vivo. Merozoites lacking EBL were unable to invade erythrocytes in vitro, indicating that EBL has a critical role for erythrocyte invasion. Quantitative time-lapse imaging revealed that with ATc administration a significant number of merozoites were detached from the erythrocyte after the erythrocyte deformation event and no echinocytosis was observed, indicating that EBL is required for merozoites to establish an irreversible connection with erythrocytes during invasion.  相似文献   

18.
We describe how to obtain an increased merozoite invasion of Plasmodium falciparum into human erythrocytes during short periods of time. Using this procedure, infected erythrocytes show multiple invasions (2–4 merozoites per erythrocyte), amplifying, several times, the effects of parasite entry into host cells. The procedure yields synchronous cultures (2-h age range) with parasitemia as high as 15%. It is possible to reach parasitemia of 50% or higher allowing for a 6-h invasion period.  相似文献   

19.
Invasion of erythrocytes by Plasmodium merozoites is a complex process that is mediated by specific molecular interactions. Here, we review recent studies on interactions between erythrocyte binding antigens (EBA) and PfRH proteins from the parasite and erythrocyte receptors involved in invasion. The timely release of these parasite ligands from internal organelles such as micronemes and rhoptries to the merozoite surface is critical for receptor-engagement leading to successful invasion. We review information on signaling mechanisms that control the regulated secretion of parasite proteins during invasion. Erythrocyte invasion involves the formation and movement of a junction between the invading merozoite and host erythrocyte. We review recent studies on the molecular composition of the junction and the molecular motor that drives movement of the junction.  相似文献   

20.
Plasmodium falciparum merozoites engage the erythrocyte surface through several receptor (host)-ligand (parasite) interactions during a brief exchange that results in parasite invasion of the red blood cell. Tens of thousands of these events occur during the initial cycle of blood-stage infections but advance towards billions as the parasite becomes visible to microscopists attempting to diagnose the underlying cause of illness in febrile patients. Advancing blood-stage infection leads to massive proportions of erythrocytes that rupture during repetitive cycles of asexual reproduction. As the infection leads to illness, non-immune or semi-immune individuals can suffer from life-threatening consequences of severe malarial anemia that play a leading role in pathogenesis. Through natural selection, some erythrocyte membrane polymorphisms are likely to have reduced the invasion success of the P. falciparum merozoite and increased the fitness of the human host population.  相似文献   

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