Maturation of the corpus callosum of the rat: I. Influence of thyroid hormones on the topography of callosal projections
Maturation of the corpus callosum of the rat: I. Influence of thyroid hormones on the topography of callosal projections
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大鼠胼胝体的成熟：一、甲状腺激素对胼胝体突起形貌的影响
DOI：
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
R. Hawkes
中科院分区：
文献类型：
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作者：
C. Gravel;R. Hawkes
正常成年大鼠胼胝体含有许多轴突轮廓，这些轴突轮廓对神经丝三联体（NF-H）的高分子量亚基具有免疫反应性。 NF-H 免疫反应性在出生后 2 周内逐渐发展。在新生儿用丙硫氧嘧啶治疗导致甲状腺功能减退的大鼠中，NF-H免疫反应性的表达几乎完全受到抑制。为了确保细胞骨架缺陷是由于甲状腺激素缺乏所致，而不是由于丙硫氧嘧啶的非特异性毒性作用，每天给以丙硫氧嘧啶饮食的甲状腺功能减退动物注射恢复性甲状腺素。此类动物表达正常水平的 NF-H。这表明胼胝体轴突可能在发育的不成熟阶段被阻止。甲状腺功能减退胼胝体的不成熟程度也可以通过比较正常大鼠、甲状腺功能减退大鼠和甲状腺素治疗后甲状腺功能减退大鼠的胼胝体髓磷脂含量来揭示。甲状腺功能减退大鼠严重缺乏髓磷脂，这种缺陷可以通过出生后甲状腺素治疗来纠正。在正常的胼胝体发育过程中，经胼胝体投射存在逐渐的空间限制，这种限制在由胼胝体区域插入的胼胝体突出皮层的成人斑块中产生。鉴于甲状腺功能减退胼胝体轴突的结构不成熟，研究其地形的发育状态很有趣。为此，将小麦胚芽凝集素-辣根过氧化物酶多次注射到成年甲状腺功能减退动物的枕叶和顶叶皮质中。在正常大鼠中，大多数视觉胼胝体投射细胞位于三组：18b 区、17 区和 18a 区的边界处以及 18a 区的外侧部分。在这些区域内，突出细胞集中在 II 层、III、Va 和 Vc-VIa 层。胼胝体轴突末端集中在这些相同区域，呈层状分布，直至胞体加 I 层。在区域 17 和 18a 的中部，发现较少的胼胝细胞，它们主要占据 Vchyphen;VIa 层，与这些相同区域中的末端的情况一样。在顶叶皮层中，胼胝体细胞和末梢以垂直阵列排列，与几乎空的区域交替。大多数集中在第 III 层和第 V 层。胼胝体轴突末端区域的地形不受甲状腺功能减退的影响。然而，胼胝体突出的细胞体发生了显着的重新分布。尽管它们采用与正常动物相同的径向分布，但它们现在在整个视觉和体感区域中排列成连续的切向层，并且不存在正常的无胼胝斑。这种排列类似于早期新生儿的情况，其中胼胝体突出细胞的体细胞也排列成连续的切向层。人们认为胼胝体投射域的逐渐限制是通过选择性轴突消除而发生的。因此，由于正常消除机制对甲状腺激素的依赖性，甲状腺功能减退动物似乎保留了不适当的未成熟胼胝体突出。
The normal adult rat corpus callosum contains numerous axonal profiles that are immunoreactive for the high molecular weight subunit of the neurofilament triplet (NF‐ H). NF‐H immunoreactivity develops gradually during the first 2 postnatal weeks. The expression of NF ‐ H immunoreactivity is almost completely suppressed in rats rendered hypothyroid by neonatal treatment with propylthiouracil. To ensure that the cytoskeletal deficit was due to a shortage of thyroid hormones rather than to unspecific, toxic effects of propylthiouracil, hypothyroid animals kept on the propylthiouracil diet were given restorative thyroxine injections daily. Such animals express NF‐H at normal levels. This suggests that the callosal axons may be arrested at an immature stage of development. The immaturity of the hypothyroid corpus callosum can also be revealed by a comparison of the myelin content in the corpus callosum between normal rats, hypothyroid rats, and hypothyroid rats under thyroxine therapy. Hypothyroid rats are severely deficient in myelin, and again this deficit can be corrected by postnatal thyroxine treatment. During normal callosal development, there is a progressive spatial restriction of the transcallosal projection that creates in the adult patches of callosally projecting cortex interposed by acallosal regions. Given the structural immaturity of the hypothyroid callosal axons, it was interesting to investigate the state of development of their topography. For this purpose, multiple injections of wheat germ agglutinin‐horseradish peroxidase were made into the occipital and parietal cortices of adult hypothyroid animals. In normal rats, the majority of visual callosally projecting cells are located in three groups–in area 18b, at the boundary of area 17 and 18a, and in the lateral portion of area 18a. Within these areas projecting cells are concentrated in layers IIhyphen;III, Va, and Vc‐VIa. The callosal axon terminals are concentrated in these same regions, with a laminar distribution as far as the somata plus layer I. In the midportion of areas 17 and 18a, fewer callosal cells are found, and they occupy mainly layers Vchyphen;VIa, as is the case for terminals in these same areas. In the parietal cortex, callosal cells and terminals are disposed in vertical arrays alternating with almost empty zones. Most are concentrated in layers III and V. The topography of the callosal axon terminal fields is unaffected by hypothyroidism. However, there is a dramatic redistribution of the callosally projecting cell somata. Although these adopt the same radial distribution as seen in the normal animals, they are now arranged in continuous tangential laminae throughout both visual and somatosensory areas, and the normal acallosal patches are absent. This arrangement resembles the situation in the early neonate where the somata of callosally projecting cells are also arranged in continuous tangential laminae. The progressive restriction of callosal projection domains has been thought to occur through selective axon elimination. It therefore appears that hypothyroid animals retain inappropriate immature callosal projections due to the thyroid hormone dependence of the normal elimination mechanisms.
出生当天接受视辐射横断的仓鼠视觉胼胝体投射神经元的分布。
影响因子：
2.9
作者：
Rhoades,RW;Fish,SE;Mooney,RD;Chiaia,NL
通讯作者：
Chiaia,NL