Pollen Tubes: a Model System for Plant Cell Growth*

Recent observations of pollen tubes show that these tubes may grow in a pulsatory fashion (Pierson et al., 1995; Plyushch et al., 1995; Li et al., 1996; Geitmann et al., 1996a, 1996b), in which phases of fast and slow growth alternate regularly. The occurrence of pulsatory growth has been used by Geitmann and coworkers (1996b) to study factors that might control growth. Their results emphasize the role of the cell wall and secretory events in regulating pollen tube growth. Here we will briefly review recent results related to the role of exocytosis, cytoskeleton, calcium and the cell wall in pollen tube growth.     

Plant Growth Inhibition and Membrane Penetration by a Homologous Series of Dichlorobenzoate Esters

The homologous series of n-alkyl esters (C₁–C₁₀) of 3,4-dichlorobenzoic acid was synthesized and their effects in inhibiting the growth of Nicotiana meristems were studied. The inhibition of growth was considered in terms of penetration of chemicals into the plant tissue and subsequent cell membrane disruption. Penetration was investigated by applying the emulsified ester to the meristem and then measuring the compound recovered with the isolated surface lipids. Decreasing amounts of 3,4-dichlorobenzoate esters penetrated into the plant as the alkyl chain length of the ester moeity was increased. Essentially no penetration occurred with the n-C₇ through C₁₀ esters tested. The effect of the ester homologues on cell membranes was studied by measuring the efflux of betacyanin from beet root cells. Decreasing amounts of pigments were released as the alkyl chain length of the ester was increased. Minimal cell membrane disruption was found for the C₇–C₁₀ esters. Inhibition of the plant meristem may result from the more rapid penetration of the short chain ester homologues into the plant.     

PFA: Program for the Quantitative Assessment of Cell Metabolism by Spectral Data Analysis

Assessment of mitochondrial oxidative metabolism has wide-ranging importance, from pharmacokinetic analysis to studies in cell viability and apoptosis. Here we present the Perfusion File Analyzer (PFA) application for the real-time analysis of spectral data to measure cytochrome c reduction, cytochrome a3 reduction, and other parameters important to cellular metabolism, which are collected during tissue perfusion experiments. Our current efforts are focused on quantitating changes in mitochondrial function by normalizing baseline drift of spectral data while addressing two major challenges: (1) a lack of real-time feedback from the system when aiming is compromised, and (2) an inability to adjust calculated data in the event of spectral shift. PFA has been developed to address these issues, and is currently used for quality assessment of human islets prior to clinical transplantation.     

Plant Growth Analysis: Additive and Multiplicative Components of Growth

Three techniques used to investigate whole-plant growth areplant growth analysis, yield component analysis and demographicanalysis. Each subdivides growth into morphological or physiologicalcomponents. This paper derives several relationships which definethe contributions made by components to the performance of thewhole plant. For example, the additive contributions by differentplant parts to overall unit leaf rate may be determined. Also,for multiplicative components, the relative growth rate of yieldis the sum of the relative growth rates of yield components.The relationships developed here serve to link different approachesto growth analysis, and they are illustrated using data fromgrowth studies of bean and sunflower. Plant growth analysis, yield component analysis, demographic analysis, Phaseolus vulgaris L., Helianthus annus L.     

Correlation between Plant Growth Regulator Release Rate and Bioactivity for the Series of Newly Synthesized Phytoactive Polymers

Phytoactive polymers are high molecular weight systems in which a plant growth regulator (PGR) unit is attached to the polymeric chain by a hydrolyzable chemical bond. The release rate of the PGR is linked to the biological activity of the phytoactive polymer and can be controlled by properties inherent in the whole macromolecular system. In this study the correlation of biological activity and plant growth regulator hydrolytic release rate was investigated for the series of newly synthesized 2,4-dichlorophenoxyacetic acid (2,4-D) polymeric esters. The polymers synthesized differ in their molecular weight, side group structure, and 2,4-D residue content. The influence of these polymer characteristics on the 2,4-D hydrolytic release was investigated, and it was demonstrated that hydrolysis rate substantially depends on the polymer molecular weight, side group structure, and 2,4-D residue content. It was also demonstrated that phytoactive polymer bioactivity depends on the hydrolysis rate of the polymers, and in dependence of this parameter can provide stimulating or inhibiting activity. Biological activity was illustrated by the elongation of wheat and barley coleoptiles.     

Current-Voltage Curves for Plant Membrane Studies: A Critical Analysis of the Method

The evolution of the steady-state current-voltage (I/V) methodis followed to its present sophistication of bipolar staircase.When applied to Chara plasmalemma the resultant I/V characteristicsvary enormously depending on the physiological state of themembrane (which is, in turn, dictated by the outside conditions).This variety of response makes formulation of ‘correct’,that is artefact-free, I/V technique quite a challenge. Thetime-dependence of the clamp current in each electrophysiologicalstate is different and this must be taken into considerationwhen steady-state I/V is investigated. Clamping of the plasmalemmaalone is also necessary, as under some conditions the conductanceof the two membranes becomes similar and the effects of thetonoplast can no longer be neglected when both membranes areclamped in series. The data obtained by point clamping and spaceclamping are compared. The use of bipolar staircase introducesmore subtle artifacts: the I/V profiles can be severely misinterpreteddue to transient conductance changes arising from the excitationor the outward and inward rectifier currents. The excitationcan be blocked by temporary exposure to lanthanum ion, but theconcentration must be carefully chosen. It is necessary to optimizethe staircase parameters to allow the rectifier currents toreturn to resting level before the next staircase pulse. Finally,brief comparison of the Chara I/Vprofile to that of other cellsis included and the relevance to patch clamp studies discussed. Key words: Current-voltage characteristics, Chara, space clamp, lanthanum blockade     

植物ms 级叶绿素荧光动力学数据采集和分析软件

本文介绍了一套可在IBM PC(兼容)微机上运行的植物ms级荧光动力学数据采集和分析软件。本软件用C语言写成,具有汉化界面、菜单驱动、彩色人机对话窗口、操作简便、灵活,兼容性好等优点。本文着重讨论了本软件如何减少荧光动力学测量中的误差、在不过分占用内存的情况下扩大采样时间范围以及如何精确测量固定荧光(Fo)和偏转荧光(Fi)等问题。本软件和我们自行组装的植物ms级动力学荧光计——植物产量荧光计PFM-101型可广泛应用于农业、植物生态学及植物生理学的光合测量和研究。     

Bailey’s方法在生境选择研究中的应用

使用已经发表的4组生境选择数据计算Bonferroni和Bailey’s置信区间,以比较分析Bailey’s方法在研究“利用－可利用型”生境选择数据时的优势。用Bailey’s方法对4组数据中的两组做出了与Bonferroni方法不同的统计推断,特别是当Bonferroni方法对其中的一组数据无法对动物是否具有生境选择性做出判断时,而Bailey’s方法却发现了差异。如同Cherry(1996)指出的,Bonferroni方法是基于拟合优度卡方检验的,要求大样本的独立数据,当出现小样本时会因为连续性和一致性缺失而做出错误推断。Bailey’s方法因为使用了连续性校正因子克服了这一缺陷,而且使用时无须进行拟合优度卡方检验,是一种简便可靠的生境选择数据分析方法。建议在推荐Bailey’s方法的同时,应适当增大样本量、控制同时分析的生境类型数量,以控制分析时I类和II类的错误率。     

Biological Time Series Analysis Using a Context Free Language: Applicability to Pulsatile Hormone Data

We present a novel approach for analyzing biological time-series data using a context-free language (CFL) representation that allows the extraction and quantification of important features from the time-series. This representation results in Hierarchically AdaPtive (HAP) analysis, a suite of multiple complementary techniques that enable rapid analysis of data and does not require the user to set parameters. HAP analysis generates hierarchically organized parameter distributions that allow multi-scale components of the time-series to be quantified and includes a data analysis pipeline that applies recursive analyses to generate hierarchically organized results that extend traditional outcome measures such as pharmacokinetics and inter-pulse interval. Pulsicons, a novel text-based time-series representation also derived from the CFL approach, are introduced as an objective qualitative comparison nomenclature. We apply HAP to the analysis of 24 hours of frequently sampled pulsatile cortisol hormone data, which has known analysis challenges, from 14 healthy women. HAP analysis generated results in seconds and produced dozens of figures for each participant. The results quantify the observed qualitative features of cortisol data as a series of pulse clusters, each consisting of one or more embedded pulses, and identify two ultradian phenotypes in this dataset. HAP analysis is designed to be robust to individual differences and to missing data and may be applied to other pulsatile hormones. Future work can extend HAP analysis to other time-series data types, including oscillatory and other periodic physiological signals.     

时间序列数据记忆性的判别方法

目的：发展时间序列数据记忆的判别方法并用于离子通道数据记忆性的判别研究。方法：应用Pearson检验与曲线拟合的方法,识别数据的记忆性。结果：得到数据记忆性的判别方法,讨论了离子通道记忆性。结论：Pearson检验与曲线拟合法简单易用,离子通道具有记忆性。     

Seriation of Anthropological Data: A Computer Program for Matrix-Ordering

A new digital computer program has been developed for the seriation of anthropological data. The program facilitates and refines procedures in the application of certain matrix-ordering approaches, such as the Brainerd-Robinson technique. The new program has special advantages for obtaining the best ordering of a case that is inherent in the data, together with special provisions for experimentation. Some of the innovations consist of working with the whole matrix pattern from start to finish, more exhaustive row-column comparisons, provision for specifying different ordering criteria, consistent utilization of a chosen criterion for matrix evaluation as well as for row-column placement, and a means of lessening the effect of input-order bias. The program is designed to produce a close approximation of an ideal model in order to place data collections as accurately as possible on a continuum of similarity for purposes such as chronological ordering and the expression of intercultural relationships.     

Time Series Analysis of Particle Tracking Data for Molecular Motion on the Cell Membrane

Biophysicists use single particle tracking (SPT) methods to probe the dynamic behavior of individual proteins and lipids in cell membranes. The mean squared displacement (MSD) has proven to be a powerful tool for analyzing the data and drawing conclusions about membrane organization, including features like lipid rafts, protein islands, and confinement zones defined by cytoskeletal barriers. Here, we implement time series analysis as a new analytic tool to analyze further the motion of membrane proteins. The experimental data track the motion of 40 nm gold particles bound to Class I major histocompatibility complex (MHCI) molecules on the membranes of mouse hepatoma cells. Our first novel result is that the tracks are significantly autocorrelated. Because of this, we developed linear autoregressive models to elucidate the autocorrelations. Estimates of the signal to noise ratio for the models show that the autocorrelated part of the motion is significant. Next, we fit the probability distributions of jump sizes with four different models. The first model is a general Weibull distribution that shows that the motion is characterized by an excess of short jumps as compared to a normal random walk. We also fit the data with a chi distribution which provides a natural estimate of the dimension d of the space in which a random walk is occurring. For the biological data, the estimates satisfy 1<d<2, implying that particle motion is not confined to a line, but also does not occur freely in the plane. The dimension gives a quantitative estimate of the amount of nanometer scale obstruction met by a diffusing molecule. We introduce a new distribution and use the generalized extreme value distribution to show that the biological data also have an excess of long jumps as compared to normal diffusion. These fits provide novel estimates of the microscopic diffusion constant.     

Studies on the Analysis of Fluorescence Decay Data by the Method of Moments

The method of moments, as presented by Isenberg and Dyson (1969; Biophys. J. 9:1337) has been shown to be a reliable way of obtaining the amplitudes and time constants of several simultaneously emitting species, even in the presence of an overlapping excitation. Recent improvements in the method include (a) a component incrementation test for determining the number of relaxations, (b) a procedure, which we call exponential depression, for dramatically improving convergence, and (c) a new algorithm for implementing the method of moments on a digital computer with a high degree of flexibility and efficiency. These improvements, as well as new general theory, are described and tested using both synthetic and real experimental data. Component incrementation consists of examining models with increasing numbers of exponential terms. Given adequate precision, we find that an analysis for N + 1 components, of data that are actually represented by N components, provides the correct amplitudes and time constants plus an N + 1 term with an insignificant amplitude. Exponential depression is a transformation in which the original excitation and fluorescence, E(t) and F(t), are multiplied by exp (-λt), where λ is an arbitrary parameter. While the convolution is invariant to this transformation, the proper choice of λ greatly reduces the number of iterations necessary to obtain the amplitudes and time constants and may even improve their accuracy. In addition, an appendix by John P. Mullooly presents a statistical analysis of the effect of counting error on the method of moments estimates of fluorescence decay parameters, applicable when data are obtained by the monophoton technique. Formulas are derived that give the approximate precision of the decay parameters for the general case of N exponential components, with calculational details for one and two component systems.     

用EXCEL中的VBA编写“多项式的三角函数拟合单峰曲线”程序

Excel是常用的电子表格处理软件,笔者采用基于Excel的VBA编程方法,编写了“多项式的三角函数拟合单峰曲线”程序,经教学科研工作中使用,获得了理想的效果。文中发表了该程序的源代码及使用方法,供广大科教人员下载使用。     

Thematic Minireview Series: Complexities of Cellular Signaling Revealed by Simple Model Organisms*

All cells discriminate environmental signals and generate appropriate intracellular responses. Our understanding of these signal transduction mechanisms has benefitted from studies across the kingdoms of life, from fungi and fish to mice and men. This thematic minireview series examines lessons learned from three of the simplest (and best understood) eukaryotic model organisms. The first article focuses on the mating pheromone pathway in budding yeast Saccharomyces cerevisiae. The second describes stress-mediated signaling in the roundworm Caenorhabditis elegans. The third outlines some of the signaling pathways that dictate growth and development in the fruit fly Drosophila melanogaster. Each system has provided unique insights into hormone and neurotransmitter signaling mechanisms, in particular those mediated by the MAPKs. The advances described in these articles will continue to improve our understanding of human physiology and pharmacology.     

用于植物挥发物分析的PoraPakTM Q吸附管快速活化方法

为提高PoraPakTM Q吸附剂的活化速度及降低活化成本,更好地应用于植物挥发物的吸附分析,本研究设计组装简易的氮气吹扫装置,并选择合适的淋洗溶剂、氮气流量、活化温度和时间。结果表明,选用100 mg PoraPakTM Q吸附剂制作吸附管,以5 mL丙酮和5 mL正己烷作为淋洗溶剂,氮气流量80 mL·min-1,活化温度200 ℃,活化时间30 min,可实现对PoraPakTM Q吸附剂的快速活化并用于挥发物吸附分析。