CYTOLOGICAL AND QUANTITATIVE CHARACTERISTICS OF 4 CEREBRAL COMMISSURES IN THE RHESUS-MONKEY
CYTOLOGICAL AND QUANTITATIVE CHARACTERISTICS OF 4 CEREBRAL COMMISSURES IN THE RHESUS-MONKEY
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DOI：
10.1002/cne.902910404
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发表时间：
1990-01-22
影响因子：
2.5
通讯作者：
RAKIC, P
中科院分区：
文献类型：
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作者：
LAMANTIA, AS;RAKIC, P
用电镜和免疫细胞化学方法对成年恒河猴（Macacamulatta）4个脑连合中不同类型的轴突和胶质细胞的数量、类型和分布进行了研究。两个新皮质连合，胼胝体和前连合包含小但细胞学上不同的蛛网膜皮质成分：海马连合，位于胼胝体压部的腹侧，和基底端脑连合，在前连合的前缘形成一个小新月。每一个原皮质通路都由一个胶质囊从相邻的新皮质连合处划定。形成这一边界的胶质细胞与针对胶质细胞酸性蛋白（GFAP）的抗血清呈免疫反应性，并发出长突起，彼此形成许多桥粒连接。这些胶质细胞的编织过程中，包被轴突束内的archicortical连合。 相反，胼胝体和前连合的GFAP阳性细胞是随机分布的细胞，具有相对短的星状突起，不形成轴突束周围的边界。定量电子显微镜分析显示，大约有6000万个轴突连接两个大脑半球：胼胝体含有5600万个。3.8 100万个轴突（n = 8），前连合包含315万个。0.24百万个轴突（n = 8），海马连合具有237，000个轴突。31，000个（n = 6），并且基底端脑连合具有193，000个轴突。28，000例（n = 5）。轴突的数量是不直接成比例的横截面积在任何连合，因为轴突组成的变化。基于猴子皮层中大约30亿个神经元的估计（Shariff，“53），我们估计所有皮层神经元中有2%到3%投射到对侧大脑半球。胼胝体的亚区以及其他连合的每一个都由五类轴突的特征子集组成，并含有不同比例的有髓纤维和无髓纤维。最大的有髓轴突和最小比例的无髓轴突（约6%）存在于携带来自初级感觉皮层的投射的胼胝体区域中，而最小的有髓轴突和最大比例的无髓轴突（约6%）存在于胼胝体区域中。30%）被发现在胼胝体的区域，携带来自联合皮层的投射。轴突组成的前连合是均匀的，类似于胼胝体部门，包含联合预测。海马连合主要包含小和中等大小的有髓鞘轴突和很少的无髓鞘轴突（approxeq.而端脑连合基底部由80%的无髓轴突和20%的最小口径的有髓轴突组成。不同类别的轴突沿着胼胝体前后轴的差异分布与功能和细胞结构不同的新皮质区的投射分离有关。这种定量细胞学数据的意义进行了讨论的背景下，皮层生理，大脑的优势，性别二型性，和端脑的进化。
The number, types, and distribution of distinct classes of axons and glia in four cerebral commissures of the adult rhesus monkey (Macaca mulatta) were determined using electron microscopic and immunocytochemical methods. The two neocortical commissures, the corpus callosum, and the anterior commissure contain small but cytologically distinct arachicortical components: the hippocampal commissure, which lies ventral to the splenium of the corpus callosum, and the basal telencephalic commissure, which forms a small crescent at the anterior margin of the anterior commissure. Each archicortical pathway is delineated from the adjacent neocortical commissure by a glial capsule. The glia cells that form this border are immunoreactive with antisera directed against glial fibrillary acidic protein (GFAP) and issue long processes that form numerous desmosomal junctions with one another. Braids of these glial processes envelop axonal fascicles within the archicortical commissures. In contrast, the GFAP-positive cells of the corpus callosum and anterior commissure are randomly distributed cells with relatively short stellate processes that do not form boundaries around axon fascicles. Quantitiative electron microscopic analysis reveals that approximately 60 million axons connect the two cerebral hemispheres: the corpus callosum contains 56.0 million .+-. 3.8 million axons (n = 8), the anterior commissure contains 3.15 million .+-. 0.24 million axons (n = 8), the hippocampal commissure has 237,000 axons .+-. 31,000 (n = 6), and the basal telencephalic commissure has 193,000 axons .+-. 28,000 (n = 5). The number of axons is not directly proportional to the cross-sectional area in any of the commissures because of variation in axonal composition. On the basis of an estimate of approximately 3 billion neurons in the monkey cortex (Shariff, ''53), we estimate that between 2 and 3% of all cortical neurons project to the opposite cerebral hemisphere. Subregions of the corpus callosum as well as each of the other commissures consist of characteristic subsets of five classes of axons and contain different proportions of myelinated to unmyelinated fibers. The largest myelinated axons and the smallest proportion of unmyelinated axons (.apprxeq. 6%) are found in regions of the corpus callosum that carry projections from primary sensory cortices, whereas the smallest myelinated axons and largest proportion of unmyelinated axons (.apprxeq. 30%) are found in regions of the corpus callosum that carry projections from association cortices. Axon composition in the anterior commissure is uniform and resembles that of callosal sectors that contain association projections. The hippocampal commissure contains predominantly small and medium-sized myelinated axons and few unmyelinated axons (.apprxeq. 10%), whereas the basal telencephalic commissure is composed of 80% unmyelinated axons and 20% of the smallest caliber myelinated axons. The differential distribution of distinct classes of axons along the anterior posterior axis of the corpus callosum is in register with the segregation of projections from functionally and cytoarchitectonically distinct neocortical areas. The significance of this quantitative cytological data is discussed in the context of cortical physiology, cerebral dominance, sexual dimorphism, and telencephalic evolution.