Nudo R J, Masterton R B
Department of Psychology, Florida State University, Tallahassee 32306-1051.
J Comp Neurol. 1988 Nov 1;277(1):53-79. doi: 10.1002/cne.902770105.
In order to estimate the qualitative commonalities and range of variation among major descending spinal pathways relevant to mankind's ancestral lineage, the supraspinal cell groups originating fibers descending directly to the spinal cord were examined in 22 mammalian species. In a standardized retrograde tract-tracing procedure, flakes of raw HRP were applied directly to the freshly cut fibers of the spinal cord after it had been hemisected at the C1-C2 junction. After a 72-hour survival period, brain and spinal cord tissues were processed by conventional HRP-processing techniques. This procedure was performed on 94 individual animals. Of this total, 41 individual cases were eliminated by a rigorous culling procedure. The results are based on 53 individuals representing 15 species selected for their successive kinship with mankind and seven species in two other lineages selected for the convergence of their visual or sensorimotor systems with anthropoids. The 22 species represent 19 genera, 14 families, eight orders, and two subclasses of Mammalia. The results show that at least 27 supraspinal cell groups, each containing intensely labeled cells, can be readily identified in each of the species. Despite vast quantitative differences in cell number and cell size, this qualitative uniformity among the relatively large number of diverse taxa suggests that the same pathways were probably present in the extinct ancestors throughout mankind's mammalian lineage and are probably still present in extant viviparous mammals as well. If so, these pathways are as old in phylogenetic history as the last common ancestor of marsupial and placental mammals--dating from the late Jurassic to early Cretaceous, perhaps 145-120 million years ago. Further comparison of the results with similar experimental findings in members of other vertebrate classes supports the notion that several of these same pathways can be traced to even more remote ancestry, with some possibly as old as the entire vertebrate subphylum--dating from the early Devonian or before, perhaps 430 million years ago. Within mankind's ancestral lineage, from the appearance of vertebrates to the appearance of mammals, there seems to have been an irregular stepwise augmentation of the set of descending pathways until the full mammalian complement was finally attained with the appearance of the corticospinal tract.
为了评估与人类祖先谱系相关的主要下行脊髓通路之间的定性共性和变异范围，我们在22种哺乳动物中检查了直接向脊髓发出下行纤维的脊髓上细胞群。在标准化的逆行束路追踪程序中，在脊髓于C1 - C2交界处进行半切后，将未加工的HRP薄片直接应用于新鲜切断的脊髓纤维。在72小时的存活期后，通过传统的HRP处理技术对脑和脊髓组织进行处理。该程序在94只个体动物上进行。在这总数中，通过严格的筛选程序排除了41个个体病例。结果基于53只个体，它们代表了15个因其与人类的连续亲缘关系而被选择的物种，以及另外两个谱系中的7个物种，这7个物种因其视觉或感觉运动系统与类人猿趋同而被选择。这22个物种代表了哺乳纲的19个属、14个科、8个目和2个亚纲。结果表明，在每个物种中都可以很容易地识别出至少27个脊髓上细胞群，每个细胞群都含有大量标记的细胞。尽管细胞数量和细胞大小存在巨大的数量差异，但在相对大量的不同分类群中的这种定性一致性表明，相同的通路可能在人类整个哺乳动物谱系的已灭绝祖先中就已存在，并且可能在现存的胎生哺乳动物中仍然存在。如果是这样，这些通路在系统发育史上与有袋类和胎盘类哺乳动物的最后共同祖先一样古老——可追溯到侏罗纪晚期至白垩纪早期，大约在1.45 - 1.2亿年前。将结果与其他脊椎动物类群成员的类似实验结果进行进一步比较，支持了这样一种观点，即这些相同通路中的一些可以追溯到更遥远的祖先，有些可能与整个脊椎动物亚门一样古老——可追溯到泥盆纪早期或更早，大约在4.3亿年前。在人类的祖先谱系中，从脊椎动物出现到哺乳动物出现，下行通路的集合似乎存在不规则的逐步增加，直到随着皮质脊髓束的出现最终达到完整的哺乳动物补充。
