A QUANTITATIVE-ANALYSIS OF THE DEVELOPMENT OF THE PYRAMIDAL TRACT IN THE CERVICAL SPINAL-CORD IN THE RAT
A QUANTITATIVE-ANALYSIS OF THE DEVELOPMENT OF THE PYRAMIDAL TRACT IN THE CERVICAL SPINAL-CORD IN THE RAT
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DOI：
10.1007/bf00305064
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发表时间：
1989-01-01
期刊：
影响因子：
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通讯作者：
NIEUWENHUYS, R
中科院分区：
文献类型：
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作者：
GORGELS, TGMF;DEKORT, EJM;NIEUWENHUYS, R
对从出生之日到三个月大的大鼠的第三颈椎节段水平的锥体束的发育进行了定量电子显微镜分析。轴突数量计算为轴突密度和束面积的乘积，轴突密度是在电子显微照片的系统随机样本中确定的。在出生后第一周，纤维束含有薄的无髓鞘轴突和生长锥。新生大鼠体内生长锥丰富，但在出生后第一周结束时仍可偶尔观察到，表明出生后第一周锥体束轴突持续增加。髓鞘形成在 P10 左右开始。到出生后第一个月末，大约 50% 的轴突已经形成髓鞘。髓鞘化在进一步成熟过程中继续进行，但在三个月大的大鼠中，28% 的轴突仍然没有髓鞘化。轴突总数在出生后迅速增加，在出生后第四天达到 153,000 个。随后，成年大鼠的轴突数量减少了近 50%，达到 79,000 个。轴突损失在出生后第二周最为明显，此时有 32,000 个轴突被消除，但会以较慢的速度持续数周。
A quantitative electron microscopic analysis was undertaken of the development of the pyramidal tract, at the level of the third cervical spinal segment, in rats ranging in age from the day of birth to three months old. The axon number was calculated as the product of axon density, determined in a systematic random sample of electron micrographs, and tract area. During the first postnatal week the tract contains thin unmyelinated axons and growth cones. Growth cones are abundant in neonatal rats, but can still be observed occasionally at the end of the first postnatal week, indicating a continuous addition of pyramidal tract axons during the first postnatal week. Myelination starts around P10. By the end of the first postnatal month approximately 50% of the axons have already been myelinated. Myelination proceeds during further maturation, but in the three month old rat 28% of the axons are still unmyelinated. The total number of axons increases rapidly after birth up to 153,000 at the fourth postnatal day. Subsequently, the number of axons is reduced by nearly 50% to 79,000 in the adult rat. The axon loss is most prominent during the second postnatal week, when 32,000 axons are eliminated, but continues for several weeks at a slower rate.