Intracellular parasite invasion strategies

Intracellular parasites use various strategies to invade cells and to subvert cellular signaling pathways and, thus, to gain a foothold against host defenses. Efficient cell entry, ability to exploit intracellular niches, and persistence make these parasites treacherous pathogens. Most intracellular parasites gain entry via host-mediated processes, but apicomplexans use a system of adhesion-based motility called "gliding" to actively penetrate host cells. Actin polymerization-dependent motility facilitates parasite migration across cellular barriers, enables dissemination within tissues, and powers invasion of host cells. Efficient invasion has brought widespread success to this group, which includes Toxoplasma, Plasmodium, and Cryptosporidium.     

植物传染性病害发生型浅析

本文通过病例资料分析，根据植物传染性病害病原物的寄生性、寄主植物的感病性和环境条件变化对其发生的影响作用等，提出植物传染性病害发生型理论，初步将植物传染性病害的发生情况分为：１）强寄生性－寄主主导作用发生型；２）强寄生性－环境主导作用发生型；３）强寄生性－寄主与环境协同作用发生型；４）强寄生性－全期侵染作用发生型；５）强寄生性－系统侵染作用发生型；６）弱寄生性－伤口主导作用发生型；７）弱寄生性－环境主导作用发生型；８）弱寄生性－伤口与环境协同作用发生型；９）弱寄生性－寄主衰老或衰弱诱促作用发生型等９种类型．植物传染性病害发生型理论，从“植病三角”关系探讨和揭示了不同传染性病害发生的特点与规律，对做好病害发生的预测预报和制订有效防治措施具有重要的理论意义和实践价值．     

绒山羊多头蚴病的诊治报告

多头蚴常寄生于牛羊脑和脊髓,引起疾病.脑多头蚴病又称脑共尾蚴或脑包虫病,主要寄生于绵羊、山羊、黄羊、牦牛、偶见于骆驼、猪、马以及其他野生反刍动物的脑和脊髓中,尤以两岁以下的绵羊易感,极少见于人.是危害羔羊和犊牛的一种重要的人畜共患寄生虫病.本病呈世界性分布,我国各省、市、区均有报道,但多呈地方性流行,并可引起动物死亡.     

Parasites as a viability cost of sexual selection in natural populations of mammals

Sexual selection in mammals has resulted in the evolution of sexual size dimorphism (SSD), with males usually being the larger sex. Comparative analyses indicate that the evolution of SSD is associated with the evolution of male-biased mortality, suggesting a possible causal link between the two. Here, we use a comparative approach to investigate the possible role of parasites in generating this relation. We show that there is a robust association between male-biased parasitism and the degree of sexual selection, as measured by mating system (monogamous or polygynous) and by the degree of SSD. There is also a positive correlation, across taxa, between male-biased mortality and male-biased parasitism. These results are consistent with the hypothesis that parasites contribute to the observed association between SSD and male-biased mortality.     

西宁地区麦油田蚜虫蚜茧蜂田间寄生率调查初报

对我省西宁地区麦、油田内蚜虫蚜茧蜂的寄生率进行了调查,调查结果表明,麦田蚜茧寄生率在5.66%~8.39%之间,油菜田蚜茧蜂寄生率在7.83%~21.19%,油菜田蚜茧蜂的田间寄生率明显高于麦田蚜茧蜂的寄生率。     

湖北地区山羊体外寄生虫病的防治

湖北省地处长江中下游,气候温暖潮湿,有利于寄生虫的滋生,特别是山羊体外寄生虫分布广,种类多,易滋生,难消灭,给山羊养殖业带来了巨大的困扰和损失。但这些体外寄生虫受季节和气候的影响很大,常随着季节的到来而暴发,随季节的更替而减弱。因此充分了解寄生虫的生活特性和治疗方法,制定科学合理的防治方案将有利于该类寄生虫病的控制,促进山羊养殖业的健康发展。     

3种牡蛎原虫的流行情况调查及多重PCR检测方法

应用聚合酶链式反应(PCR)方法对福建、广东和海南等地沿海的养殖牡蛎进行包拉米虫、派琴虫和单孢子虫检测.结果表明,这些地区的牡蛎均不同程度地感染这些原虫,经鉴定病原为牡蛎包拉米虫、奥尔森派琴虫和尼氏单孢子虫.根据基因库中奥尔森派琴虫和尼氏单孢子虫的基因序列设计多对特异性引物,检测包拉米虫的引物采用世界动物卫生组织推荐引物,通过对多重PCR反应条件的优化,建立可同时检测这3种原虫的多重PCR方法.运用该方法对样品中的牡蛎包拉米虫、奥尔森派琴虫和尼氏单孢子虫进行扩增,结果得到与试验设计相符的303、480和749 bp 3条特异性扩增条带,对其他贝类病原核酸的扩增均为阴性.多重PCR方法最低能检测到10 pg牡蛎包拉米虫、奥尔森派琴虫和尼氏单孢子虫DNA,表明该方法适用于这3种原虫的快速检测和鉴别诊断.     

Genetic analysis of the human malaria parasite Plasmodium falciparum

Malaria parasites are haploid for most of their life cycle, with zygote formation and meiosis occurring during the mosquito phase of development. The parasites can be analyzed genetically by transmitting mixtures of cloned parasites through mosquitoes to permit cross-fertilization of gametes to occur. A cross was made between two clones of Plasmodium falciparum differing in enzymes, drug sensitivity, antigens, and chromosome patterns. Parasites showing recombination between the parent clone markers were detected at a high frequency. Novel forms of certain chromosomes, detected by pulsed-field gradient gel electrophoresis, were produced readily, showing that extensive rearrangements occur in the parasite genome after cross-fertilization. Since patients are frequently infected with mixtures of genetically distinct parasites, mosquito transmission is likely to provide the principal mechanisms for generating parasites with novel genotypes.     

New applications of microbial products

Microbial secondary metabolites are now being used for applications other than as antibacterial, antifungal, and antitumor agents. These applications include use against parasites (coccidia, helminths) and insects as well as for animal and plant growth stimulation, immunosuppression, uterocontraction, and other pharmacological activities. Further applications are possible in various areas of pharmacology and agriculture, a development catalyzed by the use of simple enzyme assays for screening prior to testing in intact animals or in the field.     

Controlling and coordinating development in vector-transmitted parasites

Vector-borne parasites cause major human diseases of the developing world, including malaria, human African trypanosomiasis, Chagas disease, leishmaniasis, filariasis, and schistosomiasis. Although the life cycles of these parasites were defined over 100 years ago, the strategies they use to optimize their successful transmission are only now being understood in molecular terms. Parasites are now known to monitor their environment in both their host and vector and in response to other parasites. This allows them to adapt their developmental cycles and to counteract any unfavorable conditions they encounter. Here, I review the interactions that parasites engage in with their hosts and vectors to maximize their survival and spread.     

Xylem-tapping mistletoes: water or nutrient parasites?

Most mistletoes parasitize higher plants by tapping the xylem (a conduction tissue) of their hosts. Field observations of diurnal gas exchange parameters and carbon isotope ratios in xylem-tapping mistletoes from three continents support the hypotheses that water use efficiency and carbon isotope composition are related and that mistletoes which are parasitic for water are also nutrient parasites, differing in their water use efficiency relative to that of their hosts on the basis of host nitrogen supply in the transpiration stream.     

Thomy-headed worm infection in north american prehistoric man

Examination of ova and parasites from coprolites of probable human origin revealed eggs of the phylum Acanthocephala. Specimens were gathered from Danger Cave in Utah, an area heavily populatd with definitive rodent hosts for the Acanthocephala species Moniliformis clarki. It is postulated that prehistoric man developed Acanthocephala infection by ingesting the arthropod intermediate host, or that he was a victim of false parasitism by ingesting the whole rodent.     

佳木斯地区土地利用方式对土壤线虫群落组成的影响

[目的]对佳木斯地区5种土地利用类型的土壤线虫群落组成进行研究。[方法]采用5点取样法取样,采用淘洗-过筛-蔗糖离心法分离线虫,同时对线虫进行科属鉴定。[结果]土壤线虫25科36属,植物寄生线虫比例较高,共有优势属为盘旋属和野外垫刃属。土壤线虫总数、植物寄生线虫和食细菌线虫数量在土地利用类型间差异在0.05水平显著,赤小豆地和玉米地线虫数量多于林地和林边湿地;盘旋属集中分布于赤小豆地和玉米地;林地和林边湿地土壤生态系统的多样性和稳定性高于玉米地。[结论]土地利用方式对土壤线虫群落组成有一定影响。     

南京地区豆秆黑潜蝇寄生蜂发生情况调查

在南京地区寄生于豆秆黑潜蝇的寄生蜂计有8种,其中寄生率最高的是豆秆蝇瘿蜂与豆秆蝇茧蜂。若将寄当年滞育至翌年羽化的被寄生的蝇蛹计算在内,寄生蜂在后期(9月)对存活蝇的寄生率接近于100％。各种寄生蜂的寄生数量与大豆植株不同部位之间的联系十分显著。豆秆蝇瘿蜂在大豆主茎内最多,叶柄内最少;长腹金小蜂与两色金小蜂则在叶柄内最多,主茎内最少;其他蜂种在植株各部位的数量差异不显著。8种寄生蜂在田间的分布型经卡方检验与Taylor指数法则的测定,在各个时期和大、小样本均属泊松型。     

Sex determination in malaria parasites

A century ago, W. G. MacCallum identified distinct male and female forms in malaria parasites of both birds and humans. Since then, scientists have been puzzled by the high female-to-male ratios of parasites in Plasmodium infections and by the mechanism of sex determination. The sex ratio of malaria parasites was shown to become progressively more male as conditions that allow motility and subsequent fertilization by the male parasites become adverse. This resulted from an increased immune response against male gametes, which coincides with intense host erythropoietic activity. Natural and artificial induction of erythropoiesis in vertebrate hosts provoked a shift toward male parasite production. This change in parasite sex ratio led to reduced reproductive success in the parasite, which suggests that sex determination is adaptive and is regulated by the hematologic state of the host.     

Research toward malaria vaccines

Malaria exacts a toll of disease to people in the Tropics that seems incomprehensible to those only familiar with medicine and human health in the developed world. The methods of molecular biology, immunology, and cell biology are now being used to develop an antimalarial vaccine. The Plasmodium parasites that cause malaria have many stages in their life cycle. Each stage is antigenically distinct and potentially could be interrupted by different vaccines. However, achieving complete protection by vaccination may require a better understanding of the complexities of B- and T-cell priming in natural infections and the development of an appropriate adjuvant for use in humans.     

稻飞虱卵寄生蜂—缨小蜂生物学特性及保护利用的探讨

1977—1980年在福建闽北对稻飞虱卵寄生蜂——缨小蜂的种类、寄生率、生物学特性、种群数量动态、农药对缨小蜂毒性及保护利用等方面进行了研究。缨小蜂的优势种——稻虱缨小蜂的群体数量大,效能高,年发生20代,5—7月是一年中出现蜂量最大的时期,主要对早稻田发生的灰飞虱、白背飞虱和晚稻田后发的褐飞虱起显著的抑制作用。长管稻虱缨小蜂则年发生15代,7—9月上旬为群体数量的高峰期,主要对早稻后期、晚秧田和晚稻前期发生的白背飞虱起显著的抑制作用。拟稻虱缨小蜂年发生14代,10月间为群体数量高峰期,主要对晚稻田后发的褐飞虱起一定的抑制作用。田边禾本科杂草各种飞虱卵,是缨小蜂的过渡寄主。飞虱卵寄生率:秧田高于本田,早稻田高于晚稻田,上半年卵寄生率高达70％左右,下半年约为20—30％。保护利用途径是:(1) 保护田边杂草飞虱卵中的丰富蜂源。(2) 选用乐果、杀虫双等对飞虱卵内寄生物毒性低的农药。(3) 飞虱卵盛孵始期至盛孵高峰期施药,可与缨小蜂羽化高峰期错开。建议改变过去习惯上制定的飞虱2—3龄若虫期为施药适期的提法。(4) 下午施药可以避过缨小蜂羽化高峰时刻。稻飞虱天敌种类甚多,其中卵期寄生性天敌——缨小蜂对稻飞虱发生数量起显著的自然抑制作用,是一类较有利用价值的天敌类群。本文是四年来构初步研究总结,其中大部分是1979—1980年的研究结果。     

额尔齐斯河河鲈寄生虫种类及区系研究

【目的】对额尔齐斯河(中国段)河鲈(Percafluviatilis Linnaeus)的寄生虫组成进行调查研究。【方法】按照鱼类寄生虫的常规调查及研究方法。【结果】检查及解剖鱼体标本171尾,共发现寄生虫8种,分别为鲈锚钩吸虫(Ancyrocephalus percae Eegens)、复殖吸虫幼虫未定种(Trematoda larva sp.)、复口吸虫未定种(Diplostomulum sp.)、三枝钩绦虫幼虫(Triaenophorus Rudolphi larva)、湖沼驼形线虫(Camallanus Lacustris)、泡吻棘头虫(Pomphorhynchus laevis)、椭圆尾鲺(Argulus ellipticaudatus)、锚头鳋未定种(Lerraea cyprinacea sp.),隶属于3门、5纲、8目、8科、8属。【结论】根据S~2/X的判别原则,8种寄生虫在河鲈种群中的分布情况只有椭圆尾鲺为均匀分布,其他7种寄生虫分布均为聚集分布;其中复口吸虫未定种和三枝钩绦虫幼虫的年感染率分别大于10%,为河鲈寄生虫群落的核心种;复口吸虫的优势度指数d为0.76,为优势种。     

小菜蛾寄生性天敌的动态调查与作用分析

停止使用化学杀虫剂1年后,调查梅菜不同品种上小菜蛾寄生性天敌的寄生作用。结果表明,菜蛾绒茧蜂(Cotesia plutellae)在矮脚白梗仔、三联种上发生2个世代,高峰期分别为11月中下旬与1月上中旬,其平均寄生率分别为20.83%与31.73%、16.71%与22.63%。菜蛾啮小蜂(Oomyzus sokolowskii)在矮脚白梗仔、三联种上发生1代,高峰期为11月20日,寄生率分别达28.75%、26.00%。将寄生性天敌的作用合并,早中熟品种上寄生性天敌的作用比晚熟品种强。其中以矮脚白梗仔和大梗齐尾品种上的寄生作用最大,排除作用控制指数EIPC(Exclusive index of population control)分别为2.634 1和2.355 0,即如果排除寄生性天敌,小菜蛾将分别增长2.634 1倍、2.355 0倍。晚熟品种矮脚黒叶仔、陂(B)种上寄生作用较强,EIPC分别为1.639 9和1.589 4。     

The malaria parasite monitored by photoacoustic spectroscopy

Noninvasive photoacoustic spectroscopy was used to study the malaria parasites Plasmodium chabaudi and Plasmodium berghei, their pigment, and ferriprotoporphyrin IX, which is a by-product of the hemoglobin that the parasite ingests. The results indicate that the pigment consists of ferriprotophorphyrin self-aggregates and a noncovalent complex of ferriprotoporphyrin and protein. Spectra of chloroquine-treated parasites reveal in situ interaction between the drug and ferriprotoporphyrin. Chloroquine-resistant parasites, readily distinguishable by this method, appear to degrade hemoglobin only partially.