The Integrative Aspects of Fluid and Electrolyte Balance in Birds

小行星9515450 在哺乳动物中，肾脏是负责调节身体的水和盐含量的唯一器官，并且哺乳动物具有膀胱，在膀胱中储存肾脏的输出（尿），直到膀胱可以在方便和安全的时间排空。 另一方面，在鸟类中，肾脏与下胃肠道（GI）一起发挥作用，以调节体内的盐和水含量。 这是因为鸟类没有膀胱来储存尿液。 相反，尿液进入胃肠道的末端部分，泄殖腔。 尿液不会留在这里排泄，而是通过泄殖腔和结肠的肌肉收缩进入胃肠道（结肠）。 在结肠中，尿液的成分可以被构成结肠衬里的细胞改变。 因此，肾脏必须与下胃肠道一起工作，以维持液体和盐的平衡。 如何控制这种功能的整合是拟议研究的主要重点之一。 更好地了解鸟类如何调节水盐平衡对于商业目的的鸟类种植者至关重要，特别是家禽业，其中鸡群中水盐平衡的频繁干扰可能会产生重大的经济影响。 拟议工作的另一个重点是鸟类如何排泄作为新陈代谢副产品形成的氮。 哺乳动物以尿素的形式排出氮，尿素易溶于水，除非有严重的肾损伤，否则很少引起问题。 另一方面，鸟类以尿酸的形式排出多余的氮，尿酸是一种几乎不溶于水的化合物，往往会从溶液中沉淀出来，形成大的片状晶体。 然而，当检查鸟尿时，尽管尿酸浓度很高，但没有发现尿酸晶体。 尿液中没有晶体，而是含有小球体，小到足以沿着肾小管通过而不会堵塞肾小管。 我们已经确定这些小球是尿酸和蛋白质。 很少有人知道这些尿酸球是通过什么机制形成的，以及在肾脏的什么地方形成的。 鸟类不经常形成肾结石，目前还不清楚为什么结石在尿液中含有大量尿酸的情况下不更普遍。 然而，肾结石的爆发确实发生在商业鸡群中，具有灾难性的影响。 了解鸟类肾脏如何处理尿酸的基本过程将有助于人们更有效地处理商业鸟群和与外来鸟类打交道的贸易中的肾结石破裂。 总之，研究结果应有助于更好地了解鸟类的肾功能，以及肾脏如何与下胃肠道一起发挥作用，以维持整个动物的水和盐平衡。

9515450 Dantzler In mammals the kidney is the sole organ responsible for regulating the water and salt content of the body and mammals have a urinary bladder in which to store the output of the kidneys (urine) until the bladder can be emptied at a convenient and safe time. In birds on the other hand, the kidneys function together with the lower gastrointestinal (GI) tract to regulate the salt and water content of the body. This is because birds do not have a urinary bladder in which to store urine. Instead, the urine enters the terminal portion of the GI tract, the cloaca. The urine does not remain here to be excreted, but is moved into the GI tract ( the colon) by muscular contractions of the cloaca and colon. In the colon, the composition of the urine can be modified by the cells that make up the lining of the colon. Thus, the kidney must work together with the lower GI tract to maintain the fluid and salt balance. How this integration of function is controlled is one of the major emphasis of the proposed research. A better understanding of how birds regulate water and salt balance is of major importance to growers of birds for commercial purposes, especially the poultry industry where quite frequently disturbances of water and salt balance in flocks can have significant economic impact. Another emphasis of the proposed work deals with how birds excrete the nitrogen that is formed as a by product of metabolism. Mammals excrete nitrogen as urea which is quite soluble in water and seldom causes problems unless there has been major kidney damage. Birds on the other hand excrete their excess nitrogen as uric acid, a compound that is virtually insoluble in water and tends to precipitate from solution and form large plate-like crystals. However, when bird urine is examined no crystals of uric acid are found despite of very high concentrations of uric acid. Instead of crystals the urine contains small spheres that are sufficiently small to pass along the kidney tubules without pl ugging the tubules. We have already determined that these small spheres are up of uric acid and protein. Very little is known by what mechanism and where in the kidney these spheres of uric acid form. Birds do not often form kidney stones, and it is not understood why stones are not more prevalent with the large amount of uric acid in the urine. However, out breaks of kidney stones do occur in commercial flocks with disastrous effects. Understanding the basic process of how bird kidneys handle uric acid will help people to deal more efficiently with out breaks of kidney stones in commercial flocks and in the trade that deals with exotic birds. In summary, the results of the studies should lead to a better understanding of kidney function in birds and how the kidneys function together with the lower GI tract to maintain whole animal water and salt balance.