Theoretical analysis of the Ca2+ spark amplitude distribution
Theoretical analysis of the Ca2+ spark amplitude distribution
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DOI：
10.1016/s0006-3495(98)74034-2
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发表时间：
1998-09-01
影响因子：
3.4
通讯作者：
Balke, CW
中科院分区：
文献类型：
--
作者：
Izu, LT;Wier, WG;Balke, CW
使用共聚焦显微镜研究Ca2+火花的一个困难是相对于Ca2+释放源的线能位置的不确定性。线扫描的随机放置预计会导致测量到的Ca2+火花振幅的广泛分布(a)，即使所有的Ca2+火花产生相同。因此，由于共聚焦线扫描仪和Ca2+释放位点之间的位置差异而引起的Ca2+火花振幅的变化与Ca2+释放特性的内在差异引起的变化交织在一起。为了分离Ca2+火花振幅的这两种变化源，我们确定了通道电流或通道打开时间的影响变化-统称为源强度α -对测量的Ca2+火花振幅直方图N(a)的影响。这是通过1)模拟Ca2+释放，Ca2+和氟3扩散，以及Ca2+结合反应；2)用共聚焦显微镜模拟Ca2+火花的成像；3)使用一种新型的自动Ca2+火花探测器，从这些结果中，我们推导了一个关于源强度的概率密度函数f α (α)到N(a)的积分方程，该方程考虑了源和线扫描之间的随机位置变化。在Ca2+结合的fluo-3的空间分布是高斯分布的特殊但重要的情况下，我们展示了以下内容：I)由于位置或内在差异导致的Ca2+火花振幅的变化可以分离，并且2)f α (α)原则上可以从Ca2+火花振幅直方图中计算，因为N(a)是移位双曲线的总和，其中移位的幅度和权重取决于f α (α)。特别是，如果所有的Ca2+火花产生相同，那么1/N(a)对a的曲线将是一条直线。1/N(a)图中的不连续显示了携带不同电流的多个通道群。3)虽然Ca2+火花振幅与衰减时间之间的反比关系可以用于区分不同通道种群的Ca2+火花，但噪声会使测量的衰减时间对小振幅Ca2+火花没有意义。
A difficulty of using confocal microscopy to study Ca2+ sparks is the uncertainty of the linescan position with respect to the source of Ca2+ release. Random placement of the linescan is expected to result in a broad distribution of measured Ca2+ spark amplitudes (a) even if all Ca2+ sparks were generated identically. Thus variations in Ca2+ spark amplitude due to positional differences between confocal linescans and Ca2+ release site are intertwined with variations due to intrinsic differences in Ca2+ release properties. To separate these two sources of variations on the Ca2+ spark amplitude, we determined the effect changes of channel current or channel open time-collectively called the source strength, alpha-had on the measured Ca2+ spark amplitude histogram, N(a). This was done by 1) simulating Ca2+ release, Ca2+ and fluo3 diffusion, and Ca2+ binding reactions; 2) simulation of image formation of the Ca2+ spark by a confocal microscope; and 3) using a novel automatic Ca2+ spark detector, From these results we derived an integral equation relating the probability density function of source strengths, f alpha(alpha), to N(a), which takes into account random positional variations between the source and linescan. In the special, but important, case that the spatial distribution of Ca2+-bound fluo-3 is Gaussian, we show the following: I)variations of Ca2+ spark amplitude due to positional or intrinsic differences can be separated, and 2) f alpha(alpha) can, in principle, be calculated from the Ca2+ spark amplitude histogram since N(a) is the sum of shifted hyperbolas, where the magnitudes of the shifts and weights depend on f alpha(alpha). In particular, if all Ca2+ sparks were generated identically, then the plot of 1/N(a) against a will be a straight line. Multiple populations of channels carrying distinct currents are revealed by discontinuities in the 1/N(a) plot. 3) Although the inverse relationship between Ca2+ spark amplitude and decay time might be used to distinguish Ca2+ sparks from different channel populations, noise can render the measured decay times meaningless for small amplitude Ca2+ sparks.