Sperry D G
School of Life and Health Sciences, University of Delaware, Newark 19716.
J Comp Neurol. 1988 Nov 22;277(4):499-508. doi: 10.1002/cne.902770404.
This study was undertaken to determine how increasing ploidy in Xenopus laevis affected the size of the lumbar lateral motor column (L-LMC) motoneuron population, the size of representative hindlimb muscles, and the relationship between these features in animals at the completion of metamorphosis. Triploids were produced by exposing fertilized diploid eggs to increased hydrostatic pressure. In the triploids, L-LMC motoneuron number was significantly reduced and motoneuron nuclear cross-sectional area was significantly increased. Both L-LMC length and the total L-LMC size (neuron number x mean nuclear size) were roughly equal in diploids and triploids. No ploidy-related differences in fiber number were observed in two representative thigh muscles. In diploid animals, motoneuron number is significantly correlated with both muscle fiber number and with body size. The latter two variables are also significantly correlated with one another, making it possible that a feature related to muscle fiber number or one related to body size or both are significant in determining motoneuron number. In triploid animals, motoneuron number was significantly correlated with body size but not with muscle fiber number. This suggests that the feature significant in determining motoneuron number may be one related to body size rather than to muscle fiber number. If a feature related to muscle fiber number were the primary determinant of motoneuron number, one would have expected in addition similar average changes in the two variables in comparing diploids and triploids. That this was not observed provides further reason to suspect muscle fiber numbers may not be a primary determinant of motoneuron number. In both diploids and triploids, total L-LMC size (a value combining neuron number and neuron size) was highly correlated with body size, but again, not with muscle fiber number. The average total L-LMC size and the average body size were equal in diploids and triploids while average motoneuron number was significantly different. What this suggests is that in discussing possible mechanisms to account for correspondences between central and peripheral sizes, the relevant variable for the former may be total L-LMC size rather than motoneuron number.
本研究旨在确定非洲爪蟾倍性增加如何影响变态完成时动物的腰外侧运动柱（L-LMC）运动神经元群体大小、代表性后肢肌肉大小以及这些特征之间的关系。通过将受精二倍体卵暴露于增加的静水压力来产生三倍体。在三倍体中，L-LMC运动神经元数量显著减少，运动神经元核横截面积显著增加。二倍体和三倍体的L-LMC长度和L-LMC总体大小（神经元数量×平均核大小）大致相等。在两块代表性大腿肌肉中未观察到与倍性相关的纤维数量差异。在二倍体动物中，运动神经元数量与肌纤维数量和体型均显著相关。后两个变量之间也显著相关，这使得与肌纤维数量相关的特征、与体型相关的特征或两者在决定运动神经元数量方面可能具有重要意义。在三倍体动物中，运动神经元数量与体型显著相关，但与肌纤维数量无关。这表明在决定运动神经元数量方面起重要作用的特征可能是与体型相关的特征，而非与肌纤维数量相关的特征。如果与肌纤维数量相关的特征是运动神经元数量的主要决定因素，那么在比较二倍体和三倍体时，预计这两个变量还会有类似的平均变化。未观察到这种情况进一步表明肌纤维数量可能不是运动神经元数量的主要决定因素。在二倍体和三倍体中，L-LMC总体大小（一个结合了神经元数量和神经元大小的值）与体型高度相关，但同样与肌纤维数量无关。二倍体和三倍体的平均L-LMC总体大小和平均体型相等，而平均运动神经元数量显著不同。这表明在讨论解释中枢和外周大小对应关系的可能机制时，对于前者而言，相关变量可能是L-LMC总体大小而非运动神经元数量。
