Yasuda Y, Konishi H, Kihara T, Tanimura T
Department of Anatomy (1st Division), Kinki University School of Medicine, Osaka, Japan.
Teratology. 1990 Mar;41(3):257-74. doi: 10.1002/tera.1420410303.
This report shows by light microscopy the appearance of secondary neurulation separated from primary neurulation and its developmental fate in the spinal cord of mice exposed to retinoic acid in utero. The embryos and fetuses were derived from pregnant mice (ICR strain) given 60, 40, or 0 mg/kg of retinoic acid in olive oil on day 8 of gestation orally and killed 1, 2, or 10 days later. Separation of the primary neural fold from the secondary neural tube was seen in 9- and 10-day-old embryos: the caudal part of the neuroepithelium of the primary neural fold was disarranged with non-closed posterior neuropore, and underneath it the secondary neural tissue extended caudally with abnormal notochord. At term, fetuses showed spina bifida, including myeloschisis, myelocele, and diplomyelia (diastematomyelia) with abnormal distribution of ganglionic cells. These cord lesions were located between the third lumbar and second coccygeal levels. The former two cord anomalies were associated with diplomyelia and split the dorsal and ventral portions of the spinal cord with an overlapping zone between the third lumbar and third sacral levels. These findings suggest that the separation from primary neurulation is due to the lesions in both primary neural folds and notochord induced by retinoic acid and that the spinal cord caudal to the third lumbar level originates from both neuroectoderm and mesenchyme-like cells while that caudal to the third sacral level originates from mesenchyme-like cells only.
本报告通过光学显微镜展示了在子宫内暴露于视黄酸的小鼠脊髓中，继发性神经胚形成与原发性神经胚形成分离的外观及其发育命运。胚胎和胎儿来自妊娠第8天口服给予60、40或0mg/kg视黄酸（溶于橄榄油）的怀孕小鼠（ICR品系），并在1、2或10天后处死。在9日龄和10日龄胚胎中可见原发性神经褶与继发性神经管分离：原发性神经褶神经上皮的尾部部分排列紊乱，后神经孔未闭合，其下方继发性神经组织随着异常脊索向尾部延伸。足月时，胎儿出现脊柱裂，包括脊髓裂、脊髓脊膜膨出和脊髓纵裂（脊髓分裂症），神经节细胞分布异常。这些脊髓病变位于第三腰椎和第二尾骨水平之间。前两种脊髓异常与脊髓纵裂相关，并在第三腰椎和第三骶骨水平之间的重叠区域将脊髓的背侧和腹侧部分分开。这些发现表明，与原发性神经胚形成的分离是由于视黄酸诱导的原发性神经褶和脊索中的病变，并且第三腰椎水平以下的脊髓起源于神经外胚层和间充质样细胞，而第三骶骨水平以下的脊髓仅起源于间充质样细胞。
