What is the optimal value of the g-ratio for myelinated fibers in the rat CNS? A theoretical approach.
What is the optimal value of the g-ratio for myelinated fibers in the rat CNS? A theoretical approach.
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DOI：
10.1371/journal.pone.0007754
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发表时间：
2009-11-13
期刊：
影响因子：
3.7
通讯作者：
Hu B
中科院分区：
文献类型：
--
作者：
Chomiak T;Hu B
轴突髓鞘形成的生物学过程是复杂的，往往容易受伤和疾病。轴突内径与总外径之比或g比被广泛用作最佳轴突髓鞘形成的功能和结构指标。根据纤维传导的速度，拉什顿是第一个推导出最佳g比为0.6的理论估计值的人。这个理论极限很好地解释了一些外周纤维获得的有髓轴突的实验数据，但似乎显着低于CNS纤维。然而，这并不奇怪，因为在CNS中，轴突髓鞘形成必须实现多个目标，包括减少传导延迟，促进传导保真度，降低能量成本和节省空间。在这项研究中，我们探索的概念，平衡的设定点可以在功能水平上实现的微观结构的个别轴突变得最优化，特别是对于中央系统，轴突往往是较小的，他们的髓鞘薄。我们使用了一种直观而新颖的理论方法，该方法基于描述轴突结构和功能的基本生物物理特性，以表明可以为中枢神经系统定义最佳g比（0.77）。此外，通过将体积约束对结构设计的影响减少约40%，该方法还可以预测在某些外围纤维中观察到的g比（g = 0.6）。这些结果支持神经系统设计和构造的优化理论的概念，也可能有助于解释为什么中央和外周系统由于体积限制而进化出不同的g比。
The biological process underlying axonal myelination is complex and often prone to injury and disease. The ratio of the inner axonal diameter to the total outer diameter or g-ratio is widely utilized as a functional and structural index of optimal axonal myelination. Based on the speed of fiber conduction, Rushton was the first to derive a theoretical estimate of the optimal g-ratio of 0.6. This theoretical limit nicely explains the experimental data for myelinated axons obtained for some peripheral fibers but appears significantly lower than that found for CNS fibers. This is, however, hardly surprising given that in the CNS, axonal myelination must achieve multiple goals including reducing conduction delays, promoting conduction fidelity, lowering energy costs, and saving space. In this study we explore the notion that a balanced set-point can be achieved at a functional level as the micro-structure of individual axons becomes optimized, particularly for the central system where axons tend to be smaller and their myelin sheath thinner. We used an intuitive yet novel theoretical approach based on the fundamental biophysical properties describing axonal structure and function to show that an optimal g-ratio can be defined for the central nervous system (≈0.77). Furthermore, by reducing the influence of volume constraints on structural design by about 40%, this approach can also predict the g-ratio observed in some peripheral fibers (≈0.6). These results support the notion of optimization theory in nervous system design and construction and may also help explain why the central and peripheral systems have evolved different g-ratios as a result of volume constraints.
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影响因子：
4.2
作者：
Elder, GA;Friedrich, VL;Lazzarini, RA
通讯作者：
Lazzarini, RA
影响因子：
5.3
作者：
Balabanov, Roumen;Strand, Krystal;Popko, Brian
通讯作者：
Popko, Brian
DOI：
10.1007/bf00305041
发表时间：
1988-01-01
期刊：
ANATOMY AND EMBRYOLOGY
影响因子：
--
作者：
ADAM, A;FRIEDE, RL
通讯作者：
FRIEDE, RL
影响因子：
3.3
作者：
BLIGHT, AR
通讯作者：
BLIGHT, AR
影响因子：
5.3
作者：
Benninger, Yves;Colognato, Holly;Relvas, Joao B.
通讯作者：
Relvas, Joao B.