Energetic and Respiratory Role of Lipids in Thermally Acclimated Fish

大多数鱼类都是恒温的，即它们的体温是直接决定的，与它们所生活的水的温度没有显著差异。这意味着，对于许多温带鱼类来说，细胞温度会随季节变化20摄氏度。尽管温度降低对生物化学反应有显著的抑制作用，但许多鱼类在温暖和寒冷的温度下表现出相对稳定的生物活性，这种行为需要细胞和生物化学水平的适应性反应。特别是，迄今为止所描述的鱼类对低温的许多适应与哺乳动物物种（包括人类）对不同生理刺激的适应非常相似，例如耐力训练。赛德尔博士将利用更容易研究的鱼类肌肉系统：1)定义脂肪燃料代谢的适应性，以支持鱼类的运动，以及该系统如何受到体温变化的影响；2)评估低温诱导细胞内脂肪含量增加对氧气通过肌肉运动的适应性意义。他的实验将集中在条纹鲈鱼（Morone saxatilis）上，这是一种具有相当经济重要性的洄游鱼类。研究者将利用气相色谱法来确定体温的变化如何影响血源性分子组成和脂质（脂肪）燃料的储存沉积。从条纹鲈鱼有氧肌肉中提纯脂肪燃料分解的限速酶——肉碱长链脂肪酰基转移酶。他将通过酶动力学分析和分离组织的代谢实验来确定通常可用的脂肪酸燃料在不同温度下代谢得最好。他还将量化温度适应鱼肌肉中细胞内脂肪酸结合蛋白（FABP）的浓度。FABPs与加速脂肪酸的细胞内运动有关。热适应动物组织中FABPs的滴度将与这些组织代谢脂肪的能力相关。FABP将进一步纯化并用于实验，以直接确定该蛋白质是否能促进水溶液中脂肪化合物的运动。氧电极将用于确定细胞中脂滴的存在（在体温较低时积聚在肌肉中）是否能提高氧气从毛细血管向细胞利用部位线粒体扩散的速度。这些研究结果将更好地确定温度的季节性循环对脂质利用的影响，脂质是水生环境中重要的热量资源。研究结果可能适用于不太容易研究的肌肉系统的生理学，这些系统显示出非常相似的治疗效果。

Most fish species are ectothermic, i.e. their body temperature is directly determined and not significantly different from that of the water in which they live. This means that, for many temperate zone fish species, cell temperatures many vary seasonally by 20 degrees centigrade. Although decreasing temperature has a significant depressing effect upon biochemical reactions, many of these fish species display relatively constant biological activity at warm and cold temperatures, behavior which requires adaptive responses at the cellular and biochemical level. In particular, many adaptations of fishes to cold body temperature described to date are very similar to those shown by mammalian species (including man) to different physiological stimuli - e.g. endurance training. Dr. Sidell will utilize the more easily studied fish muscle system to : 1) define adaptations for metabolism of fatty fuels to support locomotion in fishes and how this system is influenced by changes in body temperature, and; 2) evaluate the adaptive significance of cold temperature-induced increases in intracellular fat content upon movement of oxygen through muscle. His experiments will focus upon striped bass (Morone saxatilis), a migratory fish of considerable economic importance. The investigator will utilize gas chromatography to determine how changes in body temperature affect the molecular composition of blood-borne and storage deposits of lipid (fat) fuels. The rate-limiting enzyme in breakdown of fatty fuels, carnitine long chain fatty acyltransferase, will be purified from aerobic muscle of striped bass. He will determine by enzyme kinetic analyses and metabolic experiments with isolated tissues which normally available fatty acid fuels are best metabolized at different temperatures. He will also quantify the concentrations of an intracellular fatty acid binding protein (FABP) in muscles of temperature acclimated fish. FABPs have been implicated in accelerating the intracellular movement of fatty acids. Titers of FABPs in tissues of thermally-acclimated animals will be correlated with the ability of these tissues to metabolize fats. FABP further will be purified and used to perform experiments that will directly resolve whether this protein can facilitate movement of fatty compounds in aqueous solution. Oxygen electrodes will be used to determine whether the presence of lipid droplets in cells (which accumulate in muscle at cold body temperature) can enhance the rate of diffusion of oxygen from capillaries to its site of cellular utilization, the mitochondria. Results from these studies will better define effects of seasonal cycles in temperature upon utilization of lipids which are important caloric resources in the aquatic environment. Findings may apply to the physiology of less easily studied muscle systems which show very similar treatment effects.