ASTROGLIAL REACTION TO ISCHEMIC BRAIN INJURY

星形胶质细胞是高度互动和反应性的脑细胞， 对大脑功能至关重要。 因此，对大脑的损害将会发展 或者这些细胞会改变它们的 对邻近细胞损伤的反应。 审查如何 星形胶质细胞对脑缺血损伤的反应， 了解这种疾病的细胞发病机制。 这种哲学 指导这个项目的长期目标：了解星形胶质细胞如何 对缺血性脑损伤的反应以及酸碱波动如何参与 在他们的回应中。 星形胶质细胞要么因严重缺血（即梗死）而退化，要么 通过流动中的低致死性还原转化为活性物质。 几乎没有生理信息存在，这两个细胞的特点 改变或暗示导致改变的原因。 因为H+i和K+i 调节真核细胞的生命活动， 星形胶质细胞，并且是由这些细胞调节的两种主要离子种类， 星形胶质细胞H ~+i和K ~+i变化与缺血性损伤的关系 将在这里详细研究。 离子选择性微电极用于pH，K+， 以及新开发的三重桶微电极阵列敏感 pH值和CO 32，将被用来关联模式的星形胶质细胞酸- 碱和K+从缺血的变化，与结构 这些细胞的标记物（即，细胞体大小、 DNA复制、GFAP染色强度和分布以及 局部脑GFAP含量的变化）。 星形胶质细胞的退化 使用局灶性梗死的啮齿动物模型进行体内研究，因为这种类型的 缺血性脑损伤在临床上最为普遍。 星形胶质细胞成为 严重酸中毒，并失去他们的过程中梗死从全球 缺血，可能是因为[HCO 3-]i的关键减少。 如何 星形胶质细胞pHi、[HCO 3-]I和形态学改变与局灶性梗死 未知，将被确定。 星形胶质细胞H+i和K+i的变化 与反应性星形胶质细胞增多症相关的研究将在体内使用全球 缺血，并与上述星形胶质细胞增生的结构标志物相关。 此外，低温的影响，延缓神经元的破坏， 从全球缺血，对离子和结构变量与 反应性星形细胞增多症将被检查，因为这种破坏被认为是 是星形胶质细胞增殖所必需的。 此外，由于星形胶质细胞 pHi在反应性星形细胞增多症发作时升高，这是高碳酸血症的影响， 将对酸化这些细胞的物质进行研究。 最后，体外大脑 切片制备将用于测定基于质膜的 与星形胶质细胞pHi和K+i变化相关的机制。

Astrocytes are highly interactive and reactive brain cells that are essential for brain function. Accordingly, damage to brain will evolve directly from injury to astrocytes or these cells will modify their behavior in response to injury of adjacent cells. Examination of how astrocytes respond to injury from brain ischemia should lead to an improved understanding of the cellular pathogenesis of this malady. This philosophy guides the long term goal of this project: To understand how astrocytes respond to ischemic brain injury and how acid-base fluctuations participate in their response. Astrocytes either degenerate from severe ischemia (i.e. infarction) or they are transformed into reactive species by less lethal reduction in flow. Little physiologic information exists that characterizes these two cell changes or alludes to what causes the alterations. Since H+i and K+i modulate vital activities in eukaryotic cells, are interrelated in astrocytes, and are two principal ionic species regulated by these cells, the interrelation of changes in astrocytic H+i and K+i to ischemic injury will be examined in detail here. Ion-selective microelectrodes for pH, K+, as well as a newly developed triple barrel microelectrode array sensitive to pH & CO32, will be used to correlate the patterns of astrocytic acid- base and K+ change from ischemia that are associated with structural markers for these cells (i.e measurements of the cell body size, degree of DNA replication, intensity and distribution of GFAP staining as well as change in regional brain GFAP content). Degeneration of astrocytes will be studied in vivo using a rodent model of focal infarction since this type of ischemic brain injury is clinically most prevalent. Astrocytes become severely acidotic and lose their processes during infarction from global ischemia, perhaps because of a critical reduction in [HCO3-]i. How astrocytic pHi, [HCO3-]I and morphology change with focal infarction is unknown and will be determined. Astrocytic changes in H+i and K+i associated with reactive astrocytosis will be studied in vivo using global ischemia and correlated to the above structural markers of astrocytosis. Furthermore, the effect of hypothermia, which retards neuronal destruction from global ischemia, on ionic and structural variables associated with reactive astrocytosis will be examined since such destruction is thought to be necessary for astrocytic proliferation. Additionally, since astroglial pHi rises at the onset of reactive astrocytosis, the effect of hypercarbia, which acidifies these cells will be studied. Finally, the in vitro brain slice preparation will be used to determine plasma membrane-based mechanisms which interrelate changes in astrocytic pHi and K+i.