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1.
Ionic mechanisms controlling behavioral responses of paramecium to mechanical stimulation 总被引：10，自引：0，他引：10
A mechanical stimulus applied to the anterior part of Paramecium causes a transient increase in membrane permeability to calcium. This permits a calcium current to flow into the cell, causing the membrane potential to approach the equilibrium level for calcium. The transient depolarization which results elicits a reversal in the direction of ciliary beat. When the organisms are free-swimming this is seen as the reversed locomotion of Jennings' "avoiding reaction." In contrast, a mechanical stimulus applied to the posterior part results in increased permeability to potassium ions, and hence an outward potassium current. The hyperpolarization which results causes an increase in the frequency of ciliary beat in the normal direction. In free-swimming specimens this is seen as an increase in the velocity of forward locomotion. 相似文献
2.
The binding constants and the number of binding sites for insulin, glucagon, epinephrine, cyclic adenosine monophosphate, and calcium ions for the plasma membrane of rat liver were determined by Scatchard plots. The plots are biphasic or multiphasic, an indication of at least two types of binding sites for each ligand. At least three types of binding sites were found for insulin. In the concentration range of 10(-6) to 10(-8) molar, glucagon, epinephrine, and hydro-cortisone increased calcium ion binding to the plasma membrane, whereas insulin decreased this binding. At hormone concentrations of 10(-6) to 10(-7) molar, glucagon was the most effective in increasing calcium binding, but at a hormone concentration of 10(-8) molar, hydrocortisone was the most effective in stimulating calcium binding. Adenosine triphosphate reversed the effect of insulin and inhibited the effect of the other hormones. These studies suggest a relation between hormones and calcium with respect to membrane structure and function. 相似文献
3.
Ciliated epithelial cells in the oviduct of Necturus maculosus were stimulated mechanically by brief dimpling with a microstylus. This treatment produlced a transient depolarization of the membrane, and a transient increase in the frequency of ciliary beating. The increase in frequency of ciliary beating was related to the concentration of extracellular calcium ion, decreasing with reductiotn in calcium. Addition of lanthanum was followed by a decrease in spontaneous ciliary aictivity and a hyperpolarization of the membrane. In the presence of lanthanum, the transietnt depolarization in response to mechanical stimulation had a shorter timte course, and the concomitant increase in ciliary frequency was greatly reduced. It is concluded that calciuml ions enter the cell as a result of mechanical stimulationi of the membrane, and that calcium influx leads to an increase in the frequency of ciliary activity. 相似文献
4.
Reversal response elicited in nonbeating cilia of paramecium by membrane depolarizatin 总被引：6，自引：0，他引：6
Y Naitoh 《Science (New York, N.Y.)》1966,154(749):660-662
Ciliary reversal occurs in response to electrical and chemical stimuli in specimens of Paramecium caudatum in which ciliary beat has been completely inhibited by external application of nickel ions. The mechanism underlying ciliary reversal appears, therefore, to differ from that of ciliary beat. The cessation of ciliary beat has no effect on the intracellular potential of Paramecium. However, depolarizing action potentials are associated with ciliary reversals in paramecia, treated with nickel, without ciliary beat. Thus, membrane depolarization in this species seems specifically concerned with the ciliary reversal, and not with ciliary beat. 相似文献
5.
6.
运用簇分析区分不同时间段降水的化学变化,将单个降水事件作为变量来分析,每次降水测量的9项主要离子指定为簇分析的观察值,簇分析完成后,保留6类簇作为描述对象.根据簇中各离子浓度的高低,将各簇概括为:氢离子簇(簇1);无特征离子簇(簇2);氯离子、钠离子簇(簇3);硫酸根、铵根离子簇(簇4);钙、镁离子簇(簇5);硝酸根、钾离子簇(簇6).显然,簇1属酸性降水簇,簇3是海洋型降水簇,簇2、5为中间过渡型,簇4、6为高离子浓度簇,强酸性降水与高离子浓度降水并不属于同一类,降水的酸性与降水中的碱性组分密切相关,降水的酸度仅当NH4+、Ca2+离子浓度尤其是NH4+离子浓度较低时才表现为强酸性.由东北季风气流和锋面系统控制的降水(簇1、2、3)是污染物经较长距离迁移造成的强酸性降水,簇4、簇5、簇6的降水受局地污染源影响,所含的离子浓度较高. 相似文献
7.
研究了工业碳酸锂中微量钙的测定方法。采用偶氮氯磷Ⅲ［２，７－双－（４－氯─２－膦苯偶氮）－１，８－二羟基苯酚－３，６－二磺酸］作显色剂，在ｐＨ＝２．３─２．７条件下，钙离子与偶氮氯磷Ⅲ生成水溶性蓝色配合物，最适测定波长为λ＝６５８ｎｍ，摩尔吸光系数ε＝３．１×１０４，有色溶液稳定６小时，钙含量在０─１μｇ／ｍＬ范围内服从比耳定律。该显色剂用于工业碳酸锂中微量钙的测定与原子吸收法相比较，结果一致。 相似文献
8.
以薄皮甜瓜"M15"和"M43"子叶节为外植体,研究激素浓度、卡那霉素浓度和消毒时间等对甜瓜子叶节再生及农杆菌介导遗传转化的影响。结果表明,诱导甜瓜子叶节不定芽分化最佳激素组合为0.5 mg·L~(-1)6-BA+0.05 mg·L~(-1)IAA,芽伸长激素为0.05 mg·L~(-1)6-BA,生根激素为0.1 mg·L~(-1)IAA。农杆菌介导甜瓜转化最佳条件为预培养48 h,OD_(600)=0.6农杆菌菌液侵染15 min,黑暗条件下共培养48～72 h,头孢抑菌浓度500 mg·L~(-1),卡那霉素浓度75 mg·L~(-1)。PCR检测卡那霉素抗性苗,验证外源基因已整合进入甜瓜基因组,"M15"和"M43"抗性植株阳性率分别为84.2%和77.4%。 相似文献
9.
NaCl胁迫对葡萄砧木光合特性与叶绿素荧光参数的影响 总被引：2，自引：2，他引：0
为探究葡萄（Vitis sp.）砧木对盐胁迫的响应机制,以耐盐葡萄砧木品种101-14M（V. riparia×V. rupestris）和盐敏感品种188-08（V. berlandieri × V. riparia）的一年生苗为试材,比较研究了0、4、6、8、10 g·kg-1的NaCl胁迫对2种砧木叶片叶绿素含量、光合气体交换参数和叶绿素荧光参数的影响。结果表明：随着盐浓度升高,净光合速率、气孔导度、胞间二氧化碳浓度和蒸腾速率显著下降,同时最大荧光产量、最大光化学效率、实际光化学效率和光化学淬灭系数也呈下降趋势,初始荧光产量、非光化学淬灭系数和叶绿素含量表现为先升高后降低。在6 g·kg-1 NaCl胁迫下,188-08光合速率降低主因由气孔限制转向叶绿素限制,并在8 g·kg-1 NaCl胁迫下PSⅡ受到严重损伤;而101-14M叶片在8 g·kg-1盐胁迫下主要因叶绿素限制造成光合受限,并在10 g·kg-1盐胁迫下PSⅡ反应中心遭受损伤。 相似文献
10.
化学杀虫剂对绿僵菌的影响及菌药混用研究 总被引：10，自引：1，他引：10
研究 6种化学杀虫剂对金龟子绿僵菌分生孢子萌发的影响 ,结果表明 6种化学杀虫剂皆对绿僵菌分生孢子有程度不同的抑制作用 ,浓度愈高 ,抑制作用愈强 ,但氧化乐果对绿僵菌孢子萌发抑制作用最小 .对马尾松毛虫的生物测定结果表明 :绿僵菌 (含孢量为 1 .9× 1 0 10个· L-1)与敌杀死 ( 1∶ 60 0 0 0 ) ,辛硫磷 ( 1∶ 1 0 0 0 0 ) ,灭杀毙 ( 1∶ 2 5 0 0 0 )和灭幼脲 ( 1∶ 1 5 0 0 0 )混用有明显的增效作用 ,其 LT50 值比单用绿僵菌 (含孢量为 1 .9× 1 0 10个· L-1)分别提前了 7、6、5和 3d 相似文献
11.
[目的]建立以新疆紫草毛状根愈伤组织为基础的细胞悬浮体系.[方法]以新疆紫草毛状根为外植体,探讨激素、培养基、蔗糖、钙离子等对愈伤组织诱导、生长的影响.[结果]MS附加2,4-D 1.0 mg/L+ KT0.5 mg/L的愈伤组织诱导率为100;;钙离子浓度为250 mg/L时的B5 +6- BA0.1+ NAA 0.5愈伤鲜重最多,愈伤增殖倍数为9.63倍;愈伤组织在P-1中的生长量均较小,但愈伤的颜色普遍较红,当钙离子浓度为250mg/L、P-1附加1.0 mg/L KT的处理愈伤最红.[结论]毛状根是诱导新疆紫草的最佳外植体.研究为利用新疆紫草毛状根进行细胞悬浮培养提供了理论依据. 相似文献
12.
[目的]研究超高压下不同浓度Ca2+与Na+对甜菜果胶结构及流变性质的影响,为甜菜果胶在食品中的应用提供理论依据。[方法]甜菜果胶用浓度0.05 mol·L-1的Tris-HCl溶液溶解,添加不同浓度Ca2+(2、12和20mmol·L-1)和Na+(0.05、0.1和0.6 mol·L-1),配制成1%(w/v)甜菜果胶溶液后进行超高压处理,然后分别对甜菜果胶分子量、微观结构、黏度和动态粘弹性进行测定。[结果]与常压下相比,在450 MPa条件下处理不同时间(10、20、30和50 min)后,甜菜果胶在1 550 cm-1处均出现新的吸收峰,甜菜果胶溶液的屈服应力σ0显著增加,但不同超高压处理时间之间无显著差异。添加不同浓度Ca2+或Na+的甜菜果胶在450 MPa条件下处理30 min,其结构及流变性的变化有所不同。相对于未添加Ca2+或Na+的甜菜果胶,添加2 mmol·L-1 Ca2+离子使甜菜果胶溶液屈服应力σ0、储能模量G’和损耗模量G"均明显增加,当Ca2+浓度增加到12 mmol·L-1和20 mmol·L-1时,果胶的流变性质变化不显著;添加2 mmol·L-1 Ca2+使甜菜果胶分子发生明显的交联。果胶分子量由只高压处理的2.25×105 Da显著增加到6.07×105 Da,Ca2+的添加浓度增加到20 mmol·L-1,果胶的分子量变为5.99×105 Da,与添加2mmol·L-1 Ca2+时没有显著差异,其流变性质变化亦不显著。相对于未添加Ca2+或Na+的甜菜果胶,添加0.05 mol·L-1 Na+也使甜菜果胶的屈服应力σ0显著增加,并且随着Na+浓度的持续增加,果胶的屈服应力σ0显著增加;而只有当Na+浓度增加到0.6 mol·L-1时,甜菜果胶储能模量G’和损耗模量G"才发生明显增加。添加0.1 mmol·L-1 Na+的甜菜果胶,其果胶分子链相互交联成网状,果胶分子发生明显聚集,果胶分子量显著增加到11.95×105 Da;而当Na+浓度增加到0.6 mol·L-1时,果胶链呈棒状结构,果胶分子量显著降低到5.53×105 Da。[结论]超高压下Ca2+与Na+可能与甜菜果胶分子结合使其结构发生改变,进而影响甜菜果胶的结构及流变性质。 相似文献
13.
Promotion of tubulin assembly by aluminum ion in vitro 总被引：12，自引：0，他引：12
It has been proposed that aluminum ion is a contributing factor in a variety of neurological diseases. In many of these diseases, aberrations in the cytoskeleton have been noted. The effects of aluminum ion on the in vitro assembly of tubulin into microtubules has been examined by determining the association constants for the metal ion-guanosine triphosphate-tubulin ternary complex required for polymerization. The association constant for aluminum ion was approximately 10(7) times that of magnesium ion, the physiological mediator of microtubule assembly. In addition, aluminum ion at 4.0 X 10(-10) mole per liter competed effectively with magnesium ion for support of tubulin polymerization when magnesium ion falls below 1.0 millimole per liter. The microtubules produced by aluminum ion were indistinguishable from those produced by magnesium ion when viewed by electron microscopy, and they showed identical critical tubulin concentrations for assembly and sensitivities to cold-induced depolymerization. However, the rate of guanosine triphosphate hydrolysis and the sensitivity to calcium ion-induced depolymerization, critical regulatory processes of microtubules in vivo, were markedly lower for aluminum ion microtubules than for magnesium ion microtubules. 相似文献
14.
《Science (New York, N.Y.)》1989,243(4897):1420
Table 1 of the report "Reversible cleavage and ligation of hepatitis delta virus RNA" by H.-N. Wu and M. M. C. Lai (3 Feb., p. 652) contained an error. The religation percentage when the concentration of Mg(2+) in the cleavage reaction was 2.4 mM and the concentration of EDTA was 3.0 mM should have been 10. The correct table is printed below. 相似文献
15.
【目的】聚肌胞（Poly I:C）是聚肌苷酸和聚胞苷酸的共聚物,能够模拟病毒感染后所形成的dsRNA,刺激机体产生抗病毒免疫反应和炎症反应。利用Poly I:C作为免疫刺激剂对猪外周血单核细胞（Peripheral blood mononuclear cells,PBMC）的免疫刺激试验中Poly I:C的最佳作用浓度和体外免疫刺激培养时间的研究还未见报道。本研究探讨不同的Poly I:C免疫剂量和免疫刺激时间对猪PBMC各细胞因子和受体基因表达的影响,确定Poly I:C进行免疫试验的最佳作用浓度和体外免疫刺激培养时间,为利用Poly I:C进行RNA病毒感染的免疫应答调控机理研究提供试验依据。【方法】以长白仔猪为研究对象,利用分离的PBMC和1﹕5稀释的EDTA-抗凝血,设置Poly I:C浓度梯度（0、10、20和40 μg·mL-1）和不同的体外免疫刺激培养时间（4、8、12和24 h）,通过荧光定量PCR方法测定Poly I:C免疫刺激下机体激活或者诱导表达的主要细胞因子（IL6,IL8,TNFα,IL10,IRF3,IFNα和IFNγ）和模式识别受体（TLR3和TLR4）的相对表达量,分析利用Poly I:C对猪全血和PBMC进行免疫刺激试验的最佳作用浓度和时间。【结果】猪PBMC中细胞因子和受体基因的表达量受Poly I:C浓度和免疫刺激时间的影响。各基因具有特征性的表达量变化曲线,达到最高表达变化倍数的浓度和体外培养时间各不相同。对于两个干扰素基因IFNα和IFNγ,最高表达量出现在Poly I:C免疫刺激培养4 h,而后随着培养时间的延长表达量逐渐降低,而其他5个细胞因子（IL6,IL8,TNFα,IL10和IRF3）和2个模式识别受体（TLR3和TLR4）基因随着Poly I:C浓度的增加和免疫刺激时间的延长变化倍数逐渐增加,在Poly I:C浓度为20-40 μg·mL-1,免疫刺激时间为12-24 h达到最高表达量。但是,对于最高表达量出现在浓度20 μg·mL-1和培养时间12 h的基因,其在浓度为40 μg·mL-1和培养时间24 h表达变化量只有小幅下降。另外本研究还对比检测了1﹕5稀释血在Poly I:C免疫刺激下主要细胞因子和受体的表达变化,结果表明全血中各细胞因子和受体的整体表达变化倍数比PBMC低很多,特别是对于IL6和IL8这两个PBMC中表达变化很大的基因,全血中表达变化量不仅很小,而且变化趋势相反。相对于PBMC,稀释全血完整地保存了机体的原始状态,但是利用全血进行免疫试验的主要缺点是抗凝剂保留在全血中。研究中EDTAK2抗凝剂能与血液中的钙离子结合成为螯合物,从而阻止血液凝固,但是钙离子是细胞的重要信号分子,钙离子与EDTA的结合对后续的细胞功能可能产生一定的影响。另外,全血中的某些化合物与血浆蛋白的等成分可能参与免疫细胞对Poly I:C免疫刺激的调节,减少了对Poly I:C免疫刺激的应答。【结论】（1）综合分析所检测的细胞因子和受体的变化趋势,利用Poly I:C进行猪PBMC免疫刺激试验的最佳浓度和体外培养时间分别为20 μg·mL-1和24 h。（2）1﹕5稀释的EDTA-抗凝血对Poly I:C免疫反应反应小,与PBMC对Poly I:C免疫应答有不同的应答反应趋势。 相似文献
16.
Krimigis SM Armstrong TP Axford WI Bostrom CO Fan CY Gloeckler G Lanzerotti LJ Keath EP Zwickl RD Carbary JF Hamilton DC 《Science (New York, N.Y.)》1979,206(4421):977-984
Measurements of the hot (electron and ion energies >/=20 and >/= 28 kiloelectron volts, respectively) plasma environment at Jupiter by the low-energy charged particle (LECP) instrument on Voyager 2 have revealed several new and unusual aspects of the Jovian magnetosphere. The magnetosphere is populated from its outer edge into a distance of at least approximately 30 Jupiter radii (R(J)) by a hot (3 x 10(8) to 5 x 10(8) K) multicomponent plasma consisting primarily of hydrogen, oxygen, and sulfur ions. Outside approximately 30 R(J) the hot plasma exhibits ion densities from approximately 10(-1) to approximately 10(-6) per cubic centimeter and energy densities from approximately 10(-8) to 10(-13) erg per cubic centimeter, suggesting a high beta plasma throughout the region. The plasma is flowing in the corotation direction to the edge of the magnetosphere on the dayside, where it is confined by solar wind pressure, and to a distance of approximately 140 to 160 R(J) on the nightside at approximately 0300 local time. Beyond approximately 150 R(J) the hot plasma flow changes into a "magnetospheric wind" blowing away from Jupiter at an angle of approximately 20 degrees west of the sun-Jupiter line, characterized by a temperature of approximately 3 x 10(8) K (26 kiloelectron volts), velocities ranging from approximately 300 to > 1000 kilometers per second, and composition similar to that observed in the inner magnetosphere. The radial profiles of the ratios of oxygen to helium and sulfur to helium (相似文献
17.
Scanning electron microscopic study of tile pattern of ciliary coordination and the form of the ciliary beat is now possible. Rapid fixation stops tile ciliary activity instantaneously, and critical point drying avoids distortion of the cilia by surface tension forces. Such stuidies have been made on the ciliate Opalina with this new technique. 相似文献
18.
Reversal of chloroquine resistance in Plasmodium falciparum by verapamil 总被引：30，自引：0，他引：30
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. 相似文献
19.
The effects of calcium removal on the voltage-dependent potassium channels of isolated squid neurons were studied with whole cell patch-clamp techniques. When the calcium ion concentration was lowered from 10 to 0 millimolar (that is, no added calcium), potassium channel activity, identified from its characteristic time course, disappeared within a few seconds and there was a parallel increase in resting membrane conductance and in the holding current. The close temporal correlation of the changes in the three parameters suggests that potassium channels lose their ability to close in the absence of calcium and simultaneously lose their selectivity. If potassium channels were blocked by barium ion before calcium ion was removed, the increases in membrane conductance and holding current were delayed or prevented. Thus calcium is an essential cofactor in the gating of potassium channels in squid neurons. 相似文献
20.
John W.PATRICK 《浙江大学学报(农业与生命科学版)》1990,(4)
The instablity of the stimulation of photosynthate unloading from seed coats of Phaseolus vulgaris by abscisic acid (ABA ) and benzylamino purine ( BAP ) was studied in terms of experimental conditions. ABA stimulated photosynthate unloading at pH 6 and pH 8 without close dependence upon pH. ABA at a concentration range of 10-5-10-4 mol/L displayed stimulatory effect. However, BAP revealed no effect at a concentration range of 10-6-10-4 mol/L. Experiments designed with different transport time of 14C-photosynthate indicated that ABA might act at the plasma membrane of the unloading cells. Reducing endogenous ABA level by diminishing leaf area did not facilitate the manifestation of exogenous ABA function. Potassium ion stimulated photosynthate unloading from seed coats with highest promotion at 100 mmol/L K . However, no dependence of ABA stimulation of photosynthate unloading on K was found. 相似文献