Adaptations to Counter Diffusional Constraints in Muscle of Channichthyid Icefishes

南极鱼类已经进化了4000万年， 体温几乎恒定，约为0摄氏度。 暴露于 慢性感冒需要适应性的适应来克服热 细胞过程的敏感性，并允许保留 这些特征在体温升高时会致命。 这些特点将在本项目中讨论，重点是 无血红蛋白的冰鱼科。 虽然它是公认的 这些冰鱼缺乏血红蛋白， 细胞内呼吸色素，肌红蛋白尚未被 作为家族特征解决。 初步证据显示， 这表明肌红蛋白只在一个 一种冰鱼的组织 本结论的有效性 将使用免疫学方法进行测试， 明确肌红蛋白是否在氧化肌肉中表达 海峡鱼科的物种。 还将确定是否 肌红蛋白的蛋白质编码序列中的点突变 基因解释了该蛋白在组织中的表达缺失 表达/不表达肌红蛋白。 蛋白质特性 这些结构是细胞内 脂肪酸结合蛋白在冷细胞温度下， 检查;这种蛋白质增强跨细胞运动， 代谢重要的脂肪酸和细胞保护剂 功能 协同超微结构和生化 测量冰鱼的糖酵解肌肉将确定 在冰鱼的组织中发生的适应性变化。 这些 实验将测试所提出的范式，适应 克服扩散限制是确保生命的根本 在细胞低温下。 这些研究将增加对 高等脊椎动物肌肉的适应性反应， 了解代谢的南极鱼类，一组 对南大洋的营养结构很重要。

Antarctic fish species have evolved over 40 million years at nearly constant body temperatures of about 0 C. Exposure to chronic cold has required adaptations to overcome thermal sensitivities of cellular processes and to permit retention of characteristics that would be lethal at warmer body temperatures. Such features will be addressed in this project which focuses on a hemoglobinless icefish family. Although it is well established that these icefishes lack hemoglobin, the presence/absence of the intracellular respiratory pigment, myoglobin has not been resolved as a familial characteristic. Preliminary evidence is presented that suggests myoglobin is expressed exclusively in one tissue of a single icefish species. Validity of this conclusion will be tested using immunological methods to establish definitively whether myoglobin is expressed in oxidative muscles of channichthyid species. It will also be determined whether point mutations in the protein encoding sequence of the myoglobin gene account for lack of the protein's expression mRNA in tissues that do/do not express myoglobin. Characteristics in protein structure that are necessary for function of the intracellular fatty acid binding protein at cold cell temperatures will be examined; this protein enhances transcellular movement of metabolically important fatty acids and serves a cytoprotectant function. Coordinated ultrastructural and biochemical measurements of icefish glycolytic muscle will identify adaptations that have occurred in the tissues of icefish. These experiments will test the proposed paradigm that adaptations to overcome diffusional limitations are fundamental to ensure life at cold cellular temperatures. The studies will add insight into adaptive responses of muscle in higher vertebrates and increase understanding of the metabolism of antarctic fishes, a group important to the trophic structure of the Southern Ocean.