Newborn brain oxygenation and cellular injury

描述(申请人提供)：反复呼吸暂停通常与围产期有关。据报道，所有胎龄在34周以下的婴儿都会发生窒息发作，时间超过15天，并伴有缺氧或心动过缓。50%的存活婴儿出生时体重低于1500克，会出现需要呼吸机支持或药物干预的呼吸暂停发作。短暂但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，窒息发作的生理机制仍然知之甚少，部分原因是缺乏可靠的大脑氧合测量。在这些研究中，我们实验室开发的一种非侵入性光学测量氧气的方法--磷光依赖氧猝灭将被用于测量脑组织微血管中的氧。这种方法将允许持续评估呼吸暂停和呼吸暂停后恢复期间的组织氧合状态。因此，这将是第一次全面分析呼吸暂停和恢复期间大脑中氧分压的变化。我们的实验模型将是新生的小猪。在呼吸暂停模型和呼吸暂停后恢复过程中使用的不同水平的吸入氧气将代表临床相关的情况。氧气测量将与大脑新陈代谢状态和脑损伤程度的测量结合在一起。呼吸暂停引起的细胞功能障碍和/或损伤的机制(S)将从细胞和分子水平进行研究。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。多巴胺和羟基自由基在脑损伤中的作用也将被确定。扩增的反义RNA(ARNA)技术将被用来筛选在呼吸暂停和恢复过程中表达水平可能改变的多个基因。所选择的基因与多巴胺直接或间接相关。形态、免疫组织化学、时间模式和损伤的严重程度将使用标准的组织学染色和抗APP/APLP和GFAP抗体来确定。这些研究将有助于更好地了解反复呼吸暂停导致脑损伤的机制，并为评估旨在将这种损伤降至最低的程序性改变的疗效提供一种方法。

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.