Newborn brain oxygenation and cellular injury

描述（由申请人提供）：重复性呼吸暂停通常与围产期有关。据报道，所有胎龄小于34周的婴儿都会发生呼吸暂停发作时间超过15秒并伴有缺氧或心动过缓。出生时体重小于1500 g的存活婴儿中至少有50%发生需要呼吸支持或药物干预的呼吸暂停发作。短暂但反复呼吸暂停的累积效应可能对以后的神经功能有临床意义。然而，呼吸暂停发作的生理机制仍然知之甚少，部分原因是缺乏对大脑氧合的可靠测量。在这些研究中，氧依赖的磷光猝灭，在我们的实验室开发的一种非侵入性的光学方法来测量氧气，将用于测量脑组织的微血管中的氧气。该方法将允许在呼吸暂停和呼吸暂停后恢复期间连续评估组织氧合状态。因此，这将是第一次，全面分析在呼吸暂停和恢复过程中大脑中发生的氧气压力的变化。我们的实验模型将是新生仔猪。在呼吸暂停模型和呼吸暂停后恢复期间使用的不同吸入氧气水平将代表临床相关状况。氧气测量将与脑代谢状态和脑损伤程度的测量相结合。将在细胞和分子水平上检查呼吸暂停诱导的细胞功能障碍和/或损伤的机制。通过体内微透析测量的多巴胺和羟基自由基的细胞外水平的变化将用作组织缺氧和细胞功能障碍的标志物。多巴胺和羟基自由基在脑损伤中的作用也将被确定。扩增反义RNA（aRNA）技术将用于筛选呼吸暂停和恢复期间表达水平可能发生变化的多个基因。所选的基因直接或间接与多巴胺有关。将使用Fluoro-Jade标准组织学染色以及APP/APLP和GFAP抗体确定形态学、免疫组织化学、时间模式和损伤严重程度。这些研究将导致更好地理解导致脑损伤的机制，以响应重复性呼吸暂停，并提供了一种方法来评估旨在尽量减少这种损伤的程序改变的有效性。

DESCRIPTION (provided by applicant): Repetitive apnea is commonly associated with the perinatal period. Apneic episodes longer than 15 s and accompanied by hypoxia or bradycardia have been reported to occur in all infants with gestational ages less than 34 weeks. Apneic episodes requiring ventilatory support or pharmacologic intervention occur in at feast 50% of surviving infants weighing less than 1500 g at birth. The cumulative effect of brief but repetitive apnea may have clinical significance for later neurological function. The physiological mechanisms of apneic spells, however, are still poorly understood, due in part to the lack of reliable measurements of oxygenation of the brain. In these studies, the oxygen dependent quenching of phosphorescence, a noninvasive optical method for measuring oxygen developed in our laboratory, will be used to measure the oxygen in the microvasculature of the brain tissue. This method will allow continuous evaluation of the status of tissue oxygenation during apnea and post-apneic recovery. Thus, it will be possible, for the first time, to comprehensively analyze the changes in oxygen pressure that occur in the brain during apnea and recovery. Our experimental model will be newborn piglets. The different levels of inspired oxygen used during apnea models and post-apnetic recovery will represent clinically relevant conditions. The oxygen measurements will be coupled with measurements of the status of brain metabolism and the extent of brain injury. The mechanism(s) of cellular dysfunction and/or injury induced by the apnea will be examined at both the cellular and molecular levels. Changes in extracellular levels of dopamine and hydroxyl radicals, measured by in vivo microdialysis, will be used as markers of tissue hypoxia and a cellular dysfunction. The role of dopamine and hydroxyl radicals in brain injury will be also determined. The amplified antisense RNA (aRNA) technique will be used to screen multiple genes that may be altered in expression level during apnea and recovery. The genes which were chosen are directly or indirectly associated with dopamine. The morphological, immunohistochemical, temporal patterns and the severity of damage will be determined using standard histologic staining with Fluoro-Jade, and antibodies against APP/APLP and GFAP. These studies will result in a better understanding of the mechanisms causing the brain injury in response to repetitive apnea and provide an approach to evaluating the efficacy of procedural alterations designed to minimize this injury.