Reactivated triton-extracted models o paramecium: modification of ciliary movement by calcium ions

Triton-extracted models of Paramecium were reactivated to swim in solutions of adenosine triphosphate and magnesium ions. The cilia beat in the normal direction (toward the rear) when the calcium ion concentration was less than 10-(6)M, and they beat in the "reversed" direction (toward the front) when calcium ion concentration was raised above 10-(6)M. These results support the proposal that ciliary reversal, hence backward swimming, of live paramecia is mediated by an increased cytoplasmic calcium concentration around the ciliary system by calcium-dependent membrane responses to external stimuli.     

Ionic mechanisms controlling behavioral responses of paramecium to mechanical stimulation

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.     

An ultrastructural correlate of the membrane mutant "paranoiac" in Paramecium

The highly organized array of intramembranous particles, the ciliary plaque, varies from the wild type in size and organization in two stocks of the Paramecium behavioral mutant, paranoiac. In one of these stocks, the alteration is dramatic.     

Critical point drying for scanning electron microscopic sthdy of ciliary motion

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.     

Ciliastatic components in the gas phase of cigarette smoke

The gas phase of cigarette smoke, separated into its components by gas chromatography, was passed across a ciliated specimen. The acetaldehyde, acrolein, and hydrogen cyanide produced strong inhibition of the ciliary beat. A filter which removed most of the acetaldehyde and acrolein from smoke did not reduce the inhibitory effect of the gas phase of that smoke, whereas a filter that removed most of the hydrogen cyanide did reduce inhibition.     

A magnesium current in Paramecium

Recent reappraisals of the role of ionized magnesium in cell function suggest that many cells maintain intracellular free Mg2+ at low concentrations (0.1 to 0.7 mM) and that external agents can influence cell function via changes in intracellular Mg2+ concentration. Depolarization and hyperpolarization of voltage-clamped Paramecium elicited a Mg2(+)-specific current, IMg. Both Co2+ and Mn2+ were able to substitute for Mg2+ as charge carriers, but the resultant currents were reduced compared with Mg2+ currents. Intracellular free Mg2+ concentrations were estimated from the reversal potential of IMg to be about 0.39 mM. The IMg was inhibited when external Ca2+ was removed or a Ca2+ chelator was injected, suggesting that its activation was Ca2(+)-dependent.     

Calmodulin activation of calcium-dependent sodium channels in excised membrane patches of Paramecium

Calmodulin is a calcium-binding protein that participates in the transduction of calcium signals. The electric phenotypes of calmodulin mutants of Paramecium have suggested that the protein may regulate some calcium-dependent ion channels. Calcium-dependent sodium single channels in excised patches of the plasma membrane from Paramecium were identified, and their activity was shown to decrease after brief exposure to submicromolar concentrations of calcium. Channel activity was restored to these inactivated patches by adding calmodulin that was isolated from Paramecium to the cytoplasmic surface. This restoration of channel activity did not require adenosine triphosphate and therefore, probably resulted from direct binding of calmodulin, either to the sodium channel itself or to a channel regulator that was associated with the patch membrane.     

高效氯氰菊酯对草履虫的毒性研究

[目的]探究高效氯氰菊酯对草履虫的急慢性毒性影响,为了解拟除虫菊酯类农药的毒性机理提供参考。[方法]用不同浓度梯度的高效氯氰菊酯培养草履虫,观察草履虫的死亡状况及种群增长情况。[结果]高效氯氰菊酯对草履虫的1 h急性毒性作用(LC50)为27.536 mg/L,95%置信区间为26.290~28.841 mg/L。慢性毒性试验表明,低浓度的高效氯氰菊酯促进草履虫种群增长,高浓度又抑制其增长。[结论]低浓度的高效氯氰菊酯对草履虫可能具有环境类内分泌干扰物的作用。     

Nonlinear mixing of electromagnetic waves in plasmas

Recently, a strong research effort has been focused on applications of beat waves in plasma interactions. This research has important implications for various aspects of plasma physics and plasma technology. This article reviews the present status of the field and comments on plasma probing, heating of magnetically confined and laser plasmas, ionospheric plasma modification, beat-wave particle acceleration, beat-wave current drive in toroidal devices, beat wave-driven free-electron lasers, and phase conjugation with beat waves.     

Restoration by calmodulin of a Ca2+-dependent K+ current missing in a mutant of Paramecium

A combination of genetics, biochemistry, and biophysics was used to show that calmodulin is involved in the regulation of an ion channel. Calmodulin restored the Ca2+-dependent K+ current in pantophobiac, a mutant in Paramecium that lacks this current. The restoration of the current occurred within 2 hours after the injection of 1 picogram of wild-type calmodulin into the mutant. The current remained for approximately 30 hours before the mutant phenotype returned. The injection of calmodulin isolated from pantophobiac had no effect. These results imply that calmodulin is required for the function or regulation of the Ca2+-dependent K+ current in Paramecium.     

深鰕虎鱼心电图的研究

本文报道了小型鱼类深虎鱼(Bathygobius fuscus)的心电图。采用双电极接近围心腔的方法导出,向口内灌流水模拟鱼的呼吸运动。实验表明心脏搏动电位与灌流强度成正比关系;心搏率几乎与灌流强度无关,主要受水温的影响,随着水温的升高,心搏率明显增加。本种鱼与陆上一般动物不同,其心搏率几乎与运动强度无关。     

基于高SBS阈值的HNLF产生高重复频率超短光脉冲

基于光纤中的四波混频(FWM)产生高重复频率超短光脉冲的原理,并为抑制光纤中的受激Brillouin散射(SBS),采用非均匀掺杂高SBS阈值非线性光纤,通过FWM对双拍频信号进行整形压缩,实验上获得了100GHz的高重复率超短光脉冲序列,进而分析了入纤功率对输出光脉冲的影响。     

Cilia: activation coupled to mechanical stimulation by calcium influx

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.     

Woodruffia metabolica: an exception to the rule of desmodexy

Woodruffia metabolica (Protozoa, Ciliophora) has a compound fiber on the left side of its ciliary rows composed of parallel, overlapping ribbons of kinetosome-based microtubules. No similar structure is found connecting the kinetosomes on the right side of the ciliary rows. This arrangement is in opposition to the rule of desmodexy.     

毒死蜱农药对草履虫的毒性研究

研究了有机磷农药毒死蜱对草履虫的急慢性毒性作用。结果表明:毒死蜱溶液的不同浓度对草履虫的生长有极显著影响,浓度越高毒性作用越大,毒死蜱对草履虫的1h急性毒性作用LC50为0.0435 9mg/L,最大无致死浓度为0.002 5mg/L,最小全致死浓度为1.29mg/L。回归分析结果显示,草履虫种群增长率和毒死蜱溶液浓度呈线性相关。慢性毒性试验结果显示,毒死蜱浓度在0.005~1.29mg/L范围内,浓度对数越小(即毒死蜱浓度越小)种群增长率越大,说明毒死蜱溶液在一定低浓度范围内可能具有环境内分泌干扰物效应。     

市场化进程、股权结构特征与亏损逆转程度——基于2003~2011年中国亏损上市公司的经验证据

以股权结构特征对上市公司亏损逆转程度的影响进行理论分析，选取中国证券市场上2003~2011年发生亏损的1508家公司年样本进行实证研究，其结果表明：上市公司的股权结构特征对其亏损逆转程度会产生一定的影响。其中，国有股比例对上市公司的亏损逆转程度产生显著的正面影响，管理层持股与否对上市公司的亏损逆转程度产生显著的负面影响，第一大股东持股比例和控制权市场并没有对亏损上市公司的亏损逆转程度产生明显的影响。进一步的研究还表明，市场化进程会对股权结构特征与亏损逆转程度之间的相关程度产生影响，即在市场化进程较慢的地区，上市公司的股权结构特征对其亏损逆转程度的影响较强；反之，在市场化进程较快的地区，上市公司的股权结构特征对其亏损逆转程度的影响较弱。     

Sebertia acuminata: A Hyperaccumulator of Nickel from New Caledonia

Sebertia acuminata (Sapotaceae) from New Caledonia has been shown to be a hyperaccumulator of nickel. The nickel content of the latex (25.74 percent on a dry weight basis) is easily the highest nickel concentration ever found in living material. The nickel is in the form of a low-molecular-weight, water-soluble organic complex.     

镀液组成对木材化学镀镍金属沉积速率的影响

为了确定镀液组成对木材化学镀镍金属沉积速率的影响,本文用点滴法加入镀液的方法进行了木材化学镀镍实验,分析了木材化学镀镀镍镀液的主盐浓度、还原剂浓度、络合剂浓度等对金属镍沉积速率的影响,从而得出木材化学镀镍比较理想的镀液组成。这对于利用化学镀镍这一金属加工技术对木材进行化学镀,对进一步研究木材与金属的复合以及开发功能性木质复合材料具有重要的实际意义。     

Axotomy mimicked by localized colchicine application

Comparable depression of synaptic transmission in the avian ciliary ganglion resulted from either section or localized colchicine treatment of the ciliary nerves. Both colchicine treatment and axotomny produced similar changes in RNA distribution in the cell bodies as well. Colchicine did not directly affect transmission, and action potential propagation along the ciliary nerves was normal. Interference with axoplasmic transport of material in both cases is postulated to signal the observed chromatolytic changes.     

Temperature-sensitive pawns: conditional behavioral mutants of Paramecium aurelia

"Pawns" are mutants of Paramecium aurelia in which the process of calcium activation during membrane excitation is genetically impaired, with a corresponding loss of avoiding reactions. Mutants are selected that behave normally when grown at 23 degrees C but as pawns at 35 degrees C. The normal excitation can now be disrupted and restored in the same strain at will.