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周的婴儿均可出现长于15秒并伴有缺氧或心动过缓的呼吸暂停发作。在出生时体重小于1500克的存活婴儿中，至少有50%发生需要呼吸机支持或药物干预的呼吸暂停发作。短暂而反复的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，由于缺乏对大脑氧合的可靠测量，人们对窒息发作的生理机制仍然知之甚少。在这些研究中，磷光的氧依赖猝灭是我们实验室开发的一种测量氧气的无创光学方法，将用于测量脑组织微血管中的氧气。这种方法将允许在呼吸暂停和呼吸暂停后恢复期间持续评估组织氧合状态。因此，这将有可能首次全面分析在呼吸暂停和恢复期间发生在大脑中的氧压变化。我们的实验模型是新生仔猪。在呼吸暂停模型和呼吸后恢复期间使用的不同水平的吸入氧将代表临床相关条件。氧气测量将与脑代谢状态和脑损伤程度的测量相结合。由呼吸暂停引起的细胞功能障碍和/或损伤的机制将在细胞和分子水平上进行检查。通过体内微透析测量的细胞外多巴胺和羟基自由基水平的变化将被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）技术将用于筛选在呼吸暂停和恢复期间可能改变表达水平的多个基因。被选择的基因与多巴胺直接或间接相关。形态学，免疫组织化学，时间模式和损伤的严重程度将使用标准的Fluoro-Jade组织学染色，以及针对APP/APLP和GFAP的抗体来确定。这些研究将有助于更好地了解重复性呼吸暂停导致脑损伤的机制，并提供一种方法来评估旨在减少这种损伤的程序改变的效果。

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.