Hemoglobins S and C interfere with actin remodeling in Plasmodium falciparum-infected erythrocytes

The hemoglobins S and C protect carriers from severe Plasmodium falciparum malaria. Here, we found that these hemoglobinopathies affected the trafficking system that directs parasite-encoded proteins to the surface of infected erythrocytes. Cryoelectron tomography revealed that the parasite generated a host-derived actin cytoskeleton within the cytoplasm of wild-type red blood cells that connected the Maurer's clefts with the host cell membrane and to which transport vesicles were attached. The actin cytoskeleton and the Maurer's clefts were aberrant in erythrocytes containing hemoglobin S or C. Hemoglobin oxidation products, enriched in hemoglobin S and C erythrocytes, inhibited actin polymerization in vitro and may account for the protective role in malaria.     

Reversal of chloroquine resistance in Plasmodium falciparum by verapamil

The parasite Plasmodium falciparum, like neoplastic cells, develops resistance to multiple structurally unrelated drugs. If the mechanisms by which P. falciparum and neoplastic cells become resistant are similar, then it may be possible to reverse the resistance in the two types of cells by the same pharmacological agents. Verapamil, a calcium channel blocker, completely reversed chloroquine resistance in two chloroquine-resistant P. falciparum clones from Southeast Asia and Brazil. Verapamil reversed chloroquine resistance at the same concentration (1 X 10(-6)M) as that at which it reversed resistance in multidrug-resistant cultured neoplastic cells. This same concentration of verapamil had no effect on chloroquine-sensitive parasites. Hence, chloroquine resistance in P. falciparum may fit the criteria for the multidrug-resistant phenotype.     

Reversal of chloroquine resistance in malaria parasite Plasmodium falciparum by desipramine

Desipramine and several other tricyclic antidepressant drugs reverse chloroquine resistance in Plasmodium falciparum in vitro at concentrations observed in the plasma of human patients treated for depression. Reversal of resistance is associated with increased chloroquine accumulation in the parasite, probably because of inhibition of a putative chloroquine efflux pump. When owl monkeys (Aotus lemurinus lemurinus) infected with chloroquine-resistant Plasmodium falciparum were treated with chloroquine plus desipramine, their parasitemias were rapidly suppressed. Desipramine was found to be one of the most effective compounds yet described for the reversal of chloroquine resistance both in vitro and in vivo.     

A Plasmodium falciparum antigen that binds to host erythrocytes and merozoites

Antigens that bind to erythrocytes were identified in the supernatant fluids of a cultured human malaria parasite (Plasmodium falciparum). A 175-kilodalton (175K) antigen bound only to erythrocytes susceptible to invasion. The 175K antigen from the Camp or the FCR-3 strain also bound to merozoites. However, the antigen did not bind to merozoites when merozoites and supernatant antigens were from different strains unless proteinase inhibitors were present. Moreover, erythrocytes coated with supernatant antigens from the Camp or FCR-3 strain were invaded normally by merozoites of the homologous strain but were partially resistant to invasion by merozoites of the heterologous strain. The 175K antigen may be a receptor acting as a "bridge" between erythrocytes and merozoites.     

Plasmodium falciparum malaria: band 3 as a possible receptor during invasion of human erythrocytes

Human erythrocyte band 3, a major membrane-spanning protein, was purified and incorporated into liposomes. These liposomes, at nanomolar concentrations of protein, inhibited invasion of human erythrocytes in vitro by the malaria parasite Plasmodium falciparum. Liposomes containing human band 3 were ten times more effective in inhibiting invasion than those with pig band 3 and six times more effective than liposomes containing human erythrocyte glycophorin. Liposomes alone or liposomes containing erythrocyte glycolipids did not inhibit invasion. These results suggest that band 3 participates in the invasion process in a step involving a specific, high-affinity interaction between band 3 and some component of the parasite.     

玉米和类玉米杂交后代异染色质纽重复序列的遗传稳定性

【目的】探究异染色质纽在玉米、类玉米及其杂种后代染色体上分布的特点及遗传稳定性。【方法】利用组成玉米异染色质纽的180-bp重复序列和TR-1元件对二倍体多年生类玉米（Zea diploperennis, DP）、玉米自交系330及其远缘杂交后代异源种质纯系540的有丝分裂中期染色体进行荧光原位杂交,观察杂交信号在3个材料染色体上的位置、强弱及分布数量。【结果】玉米自交系330的第2、3、5、6、7号染色体长臂的近末端区显示较强杂交信号。DP的第2、3、5、6、7、8、9号染色体的长臂末端检测出异染色质纽,其中2号染色体在短臂的末端也检测到异染色质纽杂交信号。杂交后代540的第2、5、7染色体长臂近末端区检测到较强的杂交信号;3个材料的第6染色体短臂末端的随体上均显示强杂交信号。【结论】玉米大部分异染色质纽成分不能稳定遗传,其表现出来的多态性可以作为鉴定玉米和类玉米杂种后代的细胞学标记。     

再探偏好逆转现象

通过两个实验,探讨了不同性质问题下的偏好逆转现象.实验一结果发现,在两种不同的决策方式下,在两类性质的问题上都出现了偏好逆转现象;实验二在控制了决策方式的情况下发现,仅在个体问题上存在偏好逆转现象,而群体问题上并没有出现偏好逆转现象.研究结果说明,决策方式和问题性质可能都会影响人们的决策偏向.     

再探偏好逆转现象

通过两个实验,探讨了不同性质问题下的偏好逆转现象.实验一结果发现,在两种不同的决策方式下,在两类性质的问题上都出现了偏好逆转现象;实验二在控制了决策方式的情况下发现,仅在个体问题上存在偏好逆转现象,而群体问题上并没有出现偏好逆转现象.研究结果说明,决策方式和问题性质可能都会影响人们的决策偏向.     

Correction on the nomenclature of human Plasmodium

In the nomenclatorial and zoological confusion in the names for the human malaria parasites (Sabrosky and Usinger. Science, 1944, 100, 190-192; Beltran. Gaceta Med. Mexico, 1944, 74, 61-74), one further point has been discovered. It has usually been considered that there were only two different proposals involving malariae as a new specific name-Oscillaria malariae Laveran, 1881, and Haemamoeba malariae Feletti and Grassi, 1890. Actually it now appears that there were three!     

Effects of mosquito genes on Plasmodium development

Malaria parasites must complete a complex developmental cycle in an Anopheles mosquito vector before transmission to a vertebrate host. Sexual development of the parasite in the midgut is initiated in the lumen immediately after the mosquito ingests infected blood, and the resulting ookinetes must traverse the surrounding epithelial layer before transforming into oocysts. The innate immune system of the mosquito is activated during midgut invasion, but to date, no evidence has been published identifying mosquito immune genes that affect parasite development. Here, we show by gene silencing that an Anopheles gambiae leucine rich-repeat protein acts as an antagonist and two C-type lectines act as protective agonists on the development of Plasmodium ookinetes to oocysts.     

Reversal of phenylalkylamine tachyphylaxis by norepinephrine

Since the responses to "neurosympathomimetic amines" are reduced in the reserpinized animal and restored by norepinephrine administration, it was postulated that norepinephrine might also affect the development of their tachyphylaxis. We found that norepinephrine infusion restored, at least partially, certain tachyphylactic responses to amphetamine or ephedrine and fully prevented the development of tachyphylaxis to tyramine.     

Reversal of thyroxine-induced hypermetabolism by puromycin

Previous studies have demonstrated that in addition to its effects on metabolic rate, thyroxine stimulates protein biosynthesis. The administration of puromycin, a drug which blocks protein synthesis and, therefore, the thyroxine effect on protein synthesis, acutely reverses the hypermetabolism induced in rats by prior administration of thyroxine and restores the oxygen consumption of the thyrotoxic rats to the euthyroid level. The results suggest that a larger fraction of the total body basal oxygen consumption in hyperthyroidism is related to the process of protein synthesis than in the euthyroid state and that the calorigenic effect of thyroxine is secondary to its effect on protein synthesis.     

薰衣草玻璃化组培苗逆转技术研究

[目的]比较研究不同培养基对薰衣草玻璃化组培苗形态及生理效应,为抑制组培苗生产中玻璃化现象及实施玻璃化苗逆转技术提供科学参考.[方法]以薰衣草玻璃化组培苗为材料,对培养基中MS大量元素、蔗糖、活性炭、聚乙烯吡咯烷酮(PVP)等因素进行不同浓度L9(34)正交试验比较分析,在此基础上,比较研究不同激素培养基对玻璃化苗形态生理效应.[结果]从逆转率分析得知,PVP和MS大量元素对逆转率影响分别达到极显著和显著,蔗糖和活性炭不显著;而综合评分分析可知,PVP对组培苗的逆向生长具有极显著效果,MS、蔗糖和活性炭不显著.不同浓度6-BA和KT对于玻璃化苗的逆转均有显著影响,彼此间表现极显著,KT逆转效果优于6-BA,分裂素浓度越高玻璃化越严重.[结论]配方:1/3MS+ KT(0.1)+IBA(0.05)+PVP(2 g/L)+活性炭(0.6;),不仅可显著抑制玻璃化苗的产生,而且对已经玻璃化的组培苗有显著逆转效果,逆转后的组培苗生长良好.     

适应度代价对大肠杆菌药物敏感性恢复的作用

通过测定野生型大肠杆菌对氟喹诺酮类药物敏感的、耐药的以及从耐药诱导恢复敏感的3种菌株的生长曲线,探讨适应度代价对细菌耐药性变化的影响。结果表明:对氟喹诺酮类药物耐药的大肠杆菌C02的生长速率远低于敏感菌株C01和恢复敏感性后菌株C03;而敏感菌株C01和敏感性恢复菌株C03的细菌生长曲线相近,说明在无药物选择压力环境中,适应度代价高的耐药菌生存竞争力低于适应度代价低的敏感菌,敏感菌逐渐取代耐药菌,使菌群对药物的敏感性得以恢复。     

土壤电动修复中电极切换对土壤微生物群落的影响

通过细菌计数和Biolog方法,研究了在3.0 V·cm-1的电压梯度下,不同电场切换周期(24 h、5 h、10min和1 min)对土壤微生物群落的影响.结果表明,电压梯度为3.0 V·cm-1的电场作用能够促进土壤微生物的活性,但会轻微地降低土壤微生物功能多样性,电场切换不能改变这种电场对微生物群落的影响;长时间的电场处理下,电极反应对微生物数量和功能多样性损害严重,切换电场电极能有效消除电极效应,电场电极切换周期≤5 h时,可保护电极附近土壤微生物多样性,当切换周期≤10min时,不仅可保护土壤微生物多样性,而且可以保护微生物数量.研究结果说明了电场电极切换能有效降低电极反应对微生物群落的影响,揭示了电场电极切换对土壤微生物群落影响的规律,为电场电极切换方法在污染土壤电动强化生物修复技术中的深化和应用提供理论依据.     

三氯杀螨醇对中华蟾蜍成体外周血红细胞的影响

用5种不同剂量的三氯杀螨醇(d icofo l,DCF)分别对48只中华蟾蜍(B uf o g arg arizans)成体进行体腔注射法染毒1~4次,观察并统计中华蟾蜍成体外周血红细胞产生微核、核异常及细胞异常的细胞数。结果表明,注射DCF后所有剂量组均能引起中华蟾蜍红细胞微核细胞率显著升高;除5,10 m g/kg剂量组在第1次注射后较对照组低外,其他注射剂量和次数均引起核异常细胞率升高,DCF对细胞膜与细胞质的影响小于其对细胞核的影响,在4次注射中以第2次注射后对红细胞的毒性效应最大。说明DCF是一种强诱变剂,对中华蟾蜍成体外周血红细胞具有较强的遗传毒性。     

黄鳝性逆转研究进展

黄鳝具有与其他脊椎动物不同的生理特性,即性逆转现象,这种独特的生理现象使它成为研究者热衷的研究对象之一。近年来,由于黄鳝的自然资源日趋下降,使得明确其性逆转的生物学机制日益重要,以解决市场对黄鳝苗种的需求。从组织学、内分泌学和分子生物学的角度综述黄鳝性逆转的研究现状。