Changes in Insect Epithelial Metabolism and Active Ion Transport

9407313 Chamberlin大多数人都知道发生在幼虫鳞翅目（毛虫）变成蛹（蛹或茧），然后变成成虫（蛾或蝴蝶）的戏剧性转变。昆虫的这种重塑激发了大量关于表皮发育变化的研究。另一方面，昆虫生长发育过程中内部组织的生理和代谢变化还不清楚。拟议中的研究将揭示在幼虫生长、蜕皮和变态过程中，中肠组织功能的变化。待研究的昆虫是烟草天蛾（Manduca sexta）。这种毛毛虫本质上是一个“进食机器”，消耗大量的食物来支持其惊人的增长速度。在幼虫（毛虫）生命的前16天，昆虫的大小增加了近10，000倍。这种快速的生长速度部分是由于它的大中肠的功能，它吸收和吸收摄入的食物。中肠也参与高速率的活性离子转运，正是这个过程是拟议研究的重点。在幼虫生长过程中，M. sexta蜕皮四次才变成蛹。在每次蜕皮之前，肠道被净化，并且在蜕皮过程中，新的细胞被添加到中肠。这项拟议中的研究将确定中肠离子运输是否随着幼虫的生长而变化，以及中肠在蜕皮过程中是否暂时停止参与主动离子运输。在第五和最后的幼虫阶段，大型幼虫中肠被破坏，取而代之的是一个较小的蛹上皮。PI已经证明，中肠主动离子转运在这一时期的后半部分大大减少。拟议的研究将扩大Chamberlin的这项工作，通过测量蜕皮后到第五阶段以及随后几天的几个时间点的中肠活性离子运输。这些研究将精确地确定在昆虫的变态过程中，主动离子运输何时下降。主动离子转运的能量由有氧代谢提供，因此中肠代谢的变化可能会影响主动离子转运。幼虫生长和发育期间中肠的代谢组织将通过测量代谢物水平、关键代谢酶的最大活性和分离的线粒体的呼吸来确定，线粒体是负责为主动离子运输提供大部分能量的细胞器。对中肠离子转运和代谢的研究将有助于阐明昆虫生长发育过程中内部组织的功能变化。由于蜕皮和变态是所有昆虫共同的过程，因此拟议的研究将提供与了解所有昆虫生理学相关的基本信息。***

9407313 Chamberlin Most people are aware of the dramatic transformation that takes place as a larval lepidopteran (caterpillar) changes to a pupa (chrysalis or cocoon) and then to an adult (moth or butterfly). This remodeling of the insect has inspired a great deal of research on the developmental changes in epidermis. On the other hand, changes in the physiology and metabolism of internal tissues during insect growth and development are not well-understood. The proposed research will reveal changes in the functioning of one such tissue, the midgut, during larval growth, molting and metamorphosis. The insect to be studied is the tobacco hornworm (Manduca sexta). This caterpillar is essentially an "eating machine" that consumes large quantities of food to support its phenomenal growth rate. During the first 16 days of larval (caterpillar) life, the insect increases in size nearly 10,000-fold. This rapid growth rate is due, in part, to the functioning of its large midgut which digests and absorbs the ingested food. The midgut also engages in high rates of active ion transport and it is this process that is the focus of the proposed research. During larval growth, M. sexta molts four times before it metamorphoses into a pupa. Prior to each molt the gut is purged and during the molting process new cells are added to the midgut. The proposed research will determine whether midgut ion transport changes as the larva grows and whether the midgut temporarily ceases to engage in active ion transport during the molting process. During the fifth and final larval stage, the large larval midgut is destroyed and replaced by a smaller pupal epithelium. The PI has demonstrated that midgut active ion transport is greatly diminished in the last half of this period. The proposed research will expand upon this work of Chamberlin by measuring active ion transport across midgut just after the molt to the fifth stage and at several time points during the subsequent days . These studies will precisely determine when, in the metamorphosis of the insect, active ion transport declines. The energy for active ion transport is supplied by aerobic metabolism and therefore changes in midgut metabolism may affect active ion transport. The metabolic organization of the midgut during larval growth and development will be determined by measuring metabolite levels, maximal activities of key metabolic enzymes, and the respiration of isolated mitochondria, the organelle responsible for providing most of the energy for active ion transport. These studies on midgut ion transport and metabolism will elucidate the functional changes in an internal tissue during insect growth and development. Since molting and metamorphosis are processes common to all insects, the proposed research will provide fundamental information pertinent to understanding the physiology of all insects. ***