Dpto. de Biología Celular y Patología, Universidad de Salamanca, Instituto de Neurociencias de Castilla y León, Salamanca, Spain
Neurotoxicol Teratol. 2011 Nov-Dec;33(6):686-97. doi: 10.1016/j.ntt.2011.06.001. Epub 2011 Jun 12.
Embryonic exposure to ethanol leads to malformations such as cyclopia. Cyclopic embryos present fused eyes and lack of the ventral specification of the brain, with physiological and morphological defects in the visual system, which provides a useful model for teratology and neurotoxicity assessments. We analysed the differentiation of the visual areas in the ethanol-induced cyclopic animals. For this purpose we exposed zebrafish embryos to 1.5% ethanol from 4 hours post-fertilisation (hpf) to 24 hpf in order to get cyclopic embryos. We monitored cytoarchitecture and quantified both the proliferation rate and cell differentiation from 2 days post-fertilisation (dpf) onwards, focusing on the main components of the visual system (retina, optic nerve and optic tectum) of normal and cyclopic zebrafish embryos. The visual system of the zebrafish embryos is affected by exposure to ethanol; two optic nerves that fuse before leaving the eyes are present in cyclopic specimens but an optic chiasm is not evident. Cell differentiation is severely delayed throughout the visual system at 2 dpf. At 5 dpf, lamination in the cyclopic retina and optic tectum is completed, but they are filled with pyknotic nuclei demonstrating cell death. At this stage the proliferation rate and expression patterns are unaltered and glial and neuronal neurochemical differentiations are similar to untreated animals. We found that the alterations produced by exposure to ethanol are not only cell-selective, but also tissue-selective. Cyclopia is the most severe phenotype induced by ethanol, although cell differentiation and proliferation can reach normal patterns after a certain period of time, which points to a neural plasticity process. Zebrafish embryos may possess a compensation mechanism against the ethanol effect, which would account for their use for pharmacogenetic and chemical screenings in the analysis of new molecules that could improve visual problems.
胚胎暴露于乙醇会导致畸形，如独眼畸形。独眼畸形胚胎的眼睛融合，缺乏大脑的腹侧特征，视觉系统存在生理和形态缺陷，为畸形学和神经毒性评估提供了有用的模型。我们分析了乙醇诱导的独眼畸形动物中视觉区域的分化。为此，我们从受精后 4 小时（hpf）到 24 hpf 用 1.5%乙醇处理斑马鱼胚胎，以获得独眼畸形胚胎。我们从受精后 2 天（dpf）开始监测细胞结构，并量化增殖率和细胞分化，重点关注正常和独眼畸形斑马鱼胚胎的主要视觉系统组件（视网膜、视神经和视顶盖）。乙醇暴露会影响斑马鱼胚胎的视觉系统；在独眼畸形标本中，两个在离开眼睛之前融合的视神经存在，但没有明显的视交叉。细胞分化在 2 dpf 时整个视觉系统严重延迟。在 5 dpf 时，独眼畸形视网膜和视顶盖的分层完成，但充满了凋亡核，表明细胞死亡。在这个阶段，增殖率和表达模式没有改变，胶质细胞和神经元神经化学分化与未处理的动物相似。我们发现，乙醇暴露引起的改变不仅是细胞选择性的，而且是组织选择性的。虽然细胞分化和增殖在一段时间后可以达到正常模式，但独眼畸形是乙醇诱导的最严重表型，这表明存在神经可塑性过程。斑马鱼胚胎可能具有对抗乙醇效应的补偿机制，这可以解释它们在分析新分子时用于遗传药理学和化学筛选的原因，这些新分子可以改善视觉问题。
