NUCLEAR MAGNETIC RESONANCE AND EMBRYONIC DEVELOPMENT

核磁共振（NMR）成像是一种强大的诊断工具， 广泛的潜在应用。目前，关于 核磁共振的生物效应是不完整的，不确定的，主要局限于 成熟的动物太少的研究已经做了评估的风险核磁共振 在发展过程中暴露。因为发育中的胎儿最容易受到 致畸胎剂，并可能对静态和动态磁性保持物起反应， 并且涉及在NMR期间由射频辐射产生的组织加热 exposure.一项系统的研究，以调查核磁共振的相对安全性 需要在显影期间曝光。拟议的研究将 确定：1）任何敏感性的关键时期; 2）统计 任何结构异常的发生; 3）任何功能和行为 在显影过程中暴露于NMR之后出现异常。此外，本发明还提供了一种方法， 核磁共振对发育中的神经系统的影响， 是最易受任何致畸因素影响的。更 具体而言，NMR对三个关键过程的影响， 高度精确的神经系统将被评估：1）神经迁移 嵴细胞; 2）轴突生长的投射模式和时间; 3） 特异性突触形成。 任何科学研究的关键是实验模型系统。在这 在研究中，选择鸡胚具有明显的优势。1)卵内 胚胎不受母体宿主的影响， 直接与致畸剂接触; 2）可以使用大样本人群 提供统计学上有意义的结果; 3）鸡胚已被 在所有阶段中仔细描述 发展，以确定任何变化后， NMR暴露; 4）鹌鹑细胞可用作研究的天然标记物 神经嵴移位最后选择鸡交感神经系统 神经发育的研究，因为：1）它是不太复杂的比较 2）广泛的发育研究表明， 3）交感神经系统的研究 小鸡和哺乳动物相似。 这项研究的具体目标将以非常敏感的方式进行。 技术和结果将被盲目分析，以避免偏见。 将对形态异常进行显微镜检查和分析 根据既定的发展标准。行为测试将 并仔细分析。发展中国家的研究 神经系统将利用我们日常生活中的技术， 实验室因此，神经嵴细胞的迁移模式将是 通过鹌鹑-小鸡移植技术确定。轴突投射 将通过辣根过氧化物酶（HRP）轴突追踪技术标记 并确定特定神经节细胞神经支配的模式 通过细胞内记录技术。本系统研究的结果 为核磁共振的风险评估提供了重要的数据基础 胚胎发育过程中的暴露。

Nuclear magnetic resonance (NMR) imaging is a powerful diagnostic tool with widespread potential applications. Currently, the literature on the bioeffects of NMR is incomplete, inconclusive, and mostly confined to mature animals. Too few studies have been done to evaluate the risks of NMR exposure during development. Since the developing fetus is most susceptible to teratogenic agents, and may react to static and dynamic mapetic helds, and to tissue heating produced by radiofrequency radiation during NMR exposure. a systematic study to investigate the relative safety of NMR exposure during development is required. Tbe proposed research will determine: 1) any critical periods of sensitivity; 2) the statistical occurrence of any structural abnormality; 3) any functional and behavioral abnormalities subsequent to NMR exposure during development. In addition, the effects of NMR on the developing nervous system, an organ system that is most suseeptible to any teratogeztic agenu, will be investigated. More specifically, NMR effects on three critical processes that give rite to the highly precise nervous system will be evaluated: 1) the migration of neural crest cells; 2) the projection pattem and timing of axonal growth; 3) specific synapse formation. Crucial to any scientific study is the experimental model system. In this study, the chick embryo was chosen for obvious advantages. 1) The in ovo embryo is not affected by a matemal host and reacts directly to teratogenic agents; 2) A large sample population can be used to provide statistically meaningful results; 3) The chick embryo has been carefully described throughout all stages of development, allowing for the identification of any changes subsequent to NMR exposure; 4) Quail cells can be used as natural markers to study neural crest migration. Finally, the chick sympathetic system was chosen for studies of neural development because: 1) It is less complex compared to the central nervous system; 2) Extensive devclopmental studies have already been done in our laboratory; 3) The sympathetic system of the chick is similar to that of the mammal. The specific aims of this research will be pursued with very sensitive techniques and the results will be analyzed blindly to avoid bias. Morphological abnormalities will be microscopically examined and analyzed according to established developmental criteria. Behavioral tests will be recorded on videotape and carefully analyzed. Studies on the developing nervous system wifl utilize techniques that are routine in our laboratory. Thus, the migratory pattem of neural crest celis will be determined by a quail-chick transplantation technique. Axonal projections will be labeled by horseradish peroxidase (HRP) axonal tracing techniques and the pattern of specific ganglion cell innervation will be determined by intracellular recording techniques. Results of this systematic study should provide an important data base for the assessment of risks on NMR exposure during embryonic development.