城市血吸虫病综合防治措施的研究

目的探索快速控制城市血吸虫病流行的综合措施。方法在城市血吸虫病流行区选择3个试点现场,南津港、太平桥2个点采取以化疗为主的综合防治措施,小柳叶洲点采取以环境改造灭螺为主的综合防治措施。结果南津港点3年居民血吸虫感染率分别为2.80%、2.60%和2.24%,并发生急性血吸虫病2例;感染螺平均密度分别为0.0009、0.0027、0.0020只/0.1m2。小柳叶洲点3年无居民粪检阳性者,无急性血吸虫病例,哨鼠感染率为0,没有查到感染性钉螺。太平桥点3年居民感染率分别为1.18%、0.20%和0.26%,无急性血吸虫病例,家畜感染率分别为6.35%、3.57%和3.85%,2004年发现感染性钉螺,平均密度为0.0001只/0.1m2。结论在城市血吸虫病流行区,采取以环境改造灭螺为主、人群化疗、健康教育、药物灭螺灭蚴的综合防治措施能快速控制疫情。采取以化疗为主的综合防治措施,难以有效控制疫情。     

Mechanisms of antagonistic action of internal Ca2+ on serotonin-induced potentiation of Ca2+ currents in Helix neurones

The influence of internal Ca²⁺ ions has been investigated during intracellular perfusion of isolated neurones from pedal ganglia of Helix pomatia in which serotonin (5-HT) induces a cyclic-adenosine-monophosphate-(cAMP)-dependent enhancement of high-threshold Ca²⁺ current (I _Ca). Internal free Ca²⁺ ([Ca²⁺]_i) was varied between 0.01 and 10 M by addition of Ca²⁺-EGTA [ethylenebis(oxonitrilo)tetraacetate] buffer. Elevation of [Ca²⁺]_i depressed the 5-HT effect. The dose/ effect curve for the Ca²⁺ blockade had a biphasic character and could be described by the sum of two Langmuir's isotherms for tetramolecular binding with dissociation constants K _d1=0.063 M and K _d2=1 M. Addition of calmodulin (CM) antagonists (50 M trifluoperazine or 50 M chlorpromazine), phosphodiesterase (PDE) antagonists [100 M isobutylmethylxanthine (IBMX) or 5 mM theophylline] and protein phosphatase antagonists [2 M okadaic acid (OA)] in the perfusion solution caused anticalcium action and modified the Ca²⁺ binding isotherm. Using the effect of OA and IBMX, two components of the total Ca²⁺ inhibition were separated and evaluated. In the presence of one of these blockers tetramolecular curves with K _d1=0.04 M and K _d2=0.69 M were obtained describing the activation of the retained unblocked enzyme — PDE or calcineurin (CN) correspondingly. The sum of these isotherms gave a biphasic curve similar to that in control. Leupeptin (100 M), a blocker of Ca²⁺-dependent proteases did not influence the amplitude of 5-HT effect, indicating that channel proteolysis is not involved in the depression. Our findings show that the molecular mechanism of Ca²⁺-induced suppression of the cAMP-dependent upregulation of Ca²⁺ channels is due to involvement of two Ca²⁺-CM-dependent enzymes: PDE reducing the cAMP level, and CN causing channel dephosphorylation. No other processes are involved in the investigated phenomenon at a Ca²⁺ concentration of less than or equal to 10 M.     

Comparison of simultaneous pH measurements made with 8-hydroxypyrene-1,3,6-trisulphonic acid (HPTS) and pH-sensitive microelectrodes in snail neurones

 We have evaluated the pyrene-based ratiometric fluorescent dye, 8-hydroxypyrene-1,3,6-trisulphonic acid (HPTS), by using it in conjunction with glass pH-sensitive microelectrodes to measure intracellular pH (pH_i) in voltage-clamped snail neurones. Intracellular acidification with propionic acid, and alkalinization following the activation of H⁺ channels allowed the calibration of the dye to be compared with that of the pH microelectrode over the pH range 6.50–7.50. HPTS calibrated in vitro and glass pH-sensitive microelectrodes produced similar absolute resting pH_i values, 7.16±0.05 (n=10) and 7.17±0.06 (n=9) respectively in nominally CO₂/HCO₃ ^–-free saline. At both extremes of the pH range there were small discrepancies. At acidic pH_i, 6.87±0.09 (n=5), the intracellular HPTS measurement differed by –0.08±0.03 pH units from the pH-sensitive microelectrode measurement. At alkaline pH_i,7.32±0.10 (n=5), HPTS measurements produced pH values that differed by +0.07±0.04 pH units from those of the pH-sensitive microelectrode. Some of the discrepancy could be accounted for by the slow response of the recessed-tip pH-sensitive microelectrode (time constant 77±15 s, n=3). Further experiments showed that HPTS, used at an intracellular concentration of 200 μM to 2 mM, did not block activity-dependent pH_i changes. The intracellular HPTS concentration was calculated by measurement of intracellular chloride during a series of HPTS-KCl injections. Comparison of HPTS with 2′,7′-bis(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF), at the same concentration, showed that HPTS produces a larger change in ratio over the pH range 6.00–8.00. Received: 19 February 1998 / Received after revision and accepted: 22 April 1998     

Differential action of TEA+ on two K+-current components of a molluscan neurone

Summary Snail neuronal membranes have two distinct outward current components. Both components are carried by K⁺-ions. They are, however, differentially influenced by Tetraethylammonium. At low concentrations in the external bath (5 mM), TEA⁺ blocks the delayed outward current only. The fast outward current is affected if higher TEA⁺ concentrations are used. Intracellular TEA⁺, applied iontophoretically, blocks both current components in a similar manner.     

Parathyroid hormone enhances calcium current in snail neurones — Simulation of the effect by phorbol esters

Effects of parathyroid hormone substance (PTH) on the voltage-activated calcium current (I _Ca) were studied on intracellularly perfused neurones of the snail, Helix pomatia, under voltage-clamp conditions. Application of 0.1 nM PTH produced a marked potentiation of the current. The effect developed slowly (60–70 min) and remained after removal of PTH. Potentiation could be observed in most neurones, but varied considerably from cell to cell; in some neurones I _Ca was increased 2- to 3-fold. Addition of ethylenebis(oxonitrilo)tetraacetate (EGTA, 10 mM) to, or removal of adenosine 5-triphosphate (ATP, 2 mM) from the intracellular perfusing solution resulted in a suppression or attenuation of the potentiating effect. The effect could be reproduced by the synthetic 1–34 amino acid fragment of PTH. Extracellularly applied protein kinase-C (PK-C) activator phorbol ester phorbol 12-myristate 13-acetate (PMA, 0.1–10 M) produced a similar slow increase in I _Ca (up to 1.5- to 2-fold), while its inactive analogue (4-phorbol ester) had no effect on I_Ca. The effects of PTH and PMA were not additive. PK-C inhibitors [1-(5-isoquinoline-sulphonyl)-2-methylpiperazine hydrochloride] (H-7, 100 M) and staurosporine (100 M) as well as calcium channel antagonists Cd²⁺, verapamil, nifedipine and nimodipine depressed the effect of PTH. The chloride channel blocker 4,4-diisothiocyanato-stilbene-2,2-disulphonic acid (DIDS, 1 mM) did not affect the potentiating action of PTH. Activation of the adelylate cyclase system also potentiated I _Ca in some neurones, but this effect had a different time course and was additive to the effect of PTH. A conclusion is made that activation of PK-C may mediate the slowly developing enhancement of I _Ca by PTH.     

血水草杀螺成分-血水草生物碱(ECA)的提取

目的 从血水草中提取杀螺有效成分—血水草生物碱(ECA)。方法 采用70％乙醇渗漉提取，用减压浓缩、酸解、盐析等方法纯化，提取ECA原粉。结果 ECA原粉的提取率为1.009％．结论 本提取方法可靠，设备及工艺流程简单，提取条件易控制，且成本低，便于开发应用。     

Comparative Studies of the Anti-A Agglutinins from Dolichos biflorus and Certain Snails

Abstract. Heterophile anti-A reagents from Dolichos biflorus and several snails were compared with each other by immunodiffusion and immunelectrophoresis. The differences between the lectin and the snail agglutinins were pointed out. Fewer dissimilarities were obtained in hemagglutination inhibition tests using several compounds with α or β-linked N-acetyl-D- galactosamine. In general it was found, that the crude snail anti-A reagents reacted much better with the A determinant, either cellular or soluble, than the purified lectin.     

常州市有螺环境现状调查分析

目的 调查常州市有螺环境改造现状,为螺情监测提供依据.方法 收集全市有螺环境资料,对所有有螺环境进行现场调查并进行环境分类,建立数据库分析各类环境特点,并应用Google Earth软件绘制分布图.结果 常州市有螺环境共计6 174个,面积3 911.97万m2,分布于7市(县、区)的51个乡(镇)、414个村.根据环境分类,Ⅱ类环境最多,Ⅰ、Ⅱ、Ⅲ、Ⅳ类环境面积的构成比分别为24.8％、54.4％、11.3％、9.5％.金坛市、武进区、溧阳市的有螺环境面积最大,分别占全市总面积的31.0％、24.4％、24.0％.金坛市、溧阳市、武进区、新北区以现况Ⅱ类环境居多,天宁区、钟楼区、戚墅堰区以现况Ⅰ类环境居多.Ⅳ类环境主要分布在武进区和新北区,分别占68.3％、25.9％.江湖滩、内陆和山丘3种类型流行区有螺环境面积的构成比分别为9.9％、49.8％、40.3％.3种类型流行区均以Ⅱ类环境居多,面积分别占52.3％、50.1％、60.2％,Ⅳ类环境所占比例分别为22.5％、14.1％、0.7％.结论 常州市有螺环境分布广,面积大,应重点加强对Ⅲ类、ⅣV类环境的监测.     

血吸虫中间宿主的研究进展

近年来,在WHO倡导的血吸虫病二元化防治策略的指导下,血吸虫中间宿主的研究日渐深入,研究者力求从分子生物学水平阐述其遗传、进化、生物地理分布、生殖、免疫、代谢、诊断机制,探求其如何成为血吸虫的适宜中间宿主。随着全球经济技术的不断发展,遥感技术为监测血吸虫病的流行提供便捷服务,但大型水利建设项目为血防工作带来不确定影响,其长期效应仍在观测之中。在灭螺方面,高效低毒的化学灭螺药在继续筛选中,生物灭螺和无害化钉螺的研究进展值得关注。该文主要对血吸虫中间宿主的最新研究进展作一综述。