NEUTROPHIL TRANSMIT THROUGH THE PULMONARY MICROVASCULATURE

肺微血管含有约60%的中性粒细胞， 是在全身大血管中观察到的浓度的两倍， 嗜中性粒细胞的毛细血管通过时间比红细胞长 红细胞（RBC）。这些长的过境时间是由于 毛细血管和中性粒细胞的机械特性， 特别是毛细血管段和嗜中性粒细胞的尺寸， 与RBC相比，中性粒细胞的变形时间更长， 毛细血管床独特的多节段解剖结构， 为红细胞提供了许多平行的通路， 被中性粒细胞暂时阻塞的节段。拟议 研究将调查中性粒细胞通过肺部的转运 微血管的机械性能， 毛细血管和中性粒细胞。我们的核心假设是， 正常的肺，中性粒细胞通过肺转运 微血管系统的几何形状和顺应性决定 毛细管床，毛细管上的压力梯度 段，和中性粒细胞的机械特性。研究 具体目标中所述将提供有关以下方面的新信息 每个促成因素并将开始检查它们的作用。目的 1将确定毛细管段的顺应性， 共聚焦显微镜通过测量横截面积 不同透壁压和肺容积下的毛细血管段 在呼吸期间发生的范围内。Aim 2将开发一个 计算模型来估计压力梯度、血流 以及血液通过单个毛细血管的时间分布 节段和模拟的动脉-静脉通路， 呼吸，以及确定中性粒细胞的作用， 临时遮挡相邻区域中这些参数上的段 片段目的3将确定中性粒细胞在 中性粒细胞和毛细血管段的床和形状变化， 共聚焦显微镜目标4将确定机械性能 静止和激活的中性粒细胞，无论是在他们的外周， 在他们的细胞质中，使用磁扭曲细胞仪， 探讨了以前没有研究过的中性粒细胞力学的各个方面。的 细胞骨架在决定力学性能中的作用 也将被审查。目标5将比较计算值和观察值 中性粒细胞通过时间的分布，以确定 中性粒细胞结构的力学模型与 在体内观察到的中性粒细胞通过时间的分布。 是否中性粒细胞的机械性质的变化诱导 炎症刺激可以解释它们在体内的隔离 还将评价毛细管床。这些研究将 提供了有关机械性能的新信息， 单个毛细管段和整个床，以及 中性粒细胞的机械特性以及它们如何通过 正常的毛细血管床，并将有助于集中未来的研究 中性粒细胞结构和转运。这些机械事件也是 在炎症过程中至关重要， 中性粒细胞引起其机械特性的改变， 水肿形成改变毛细血管的顺应性。

The pulmonary microvasculature contains neutrophils in about 60 times the concentration observed in the large systemic vessels due to longer capillary transit times of neutrophils than red blood cells (RBC). These long transit times are attributed to the mechanical characteristics of capillaries and neutrophils, particularly the dimensions of capillary segments and neutrophils, the longer deformation times of neutrophils compared to RBC, and the unique multisegmented anatomy of the capillary bed that provides numerous parallel pathways for RBC to detour around segments temporarily obstructed by neutrophils. The proposed studies will investigate neutrophil transit though the pulmonary microvasculature by examining the mechanical properties of capillaries and neutrophils. Our central hypothesIs is that, in normal lungs, neutrophil transit through the pulmonary microvasculature is determined by the geometry and compliance of the capillary bed, the pressure gradient across a capillary segment, and the mechanical properties of neutrophils. The studies described in the specific aims will provide new information about each contributing factor and will begin to examine their roles. Aim 1 will determine the compliance of capillary segments using confocal microscopy by measuring the cross-sectional area of capillary segments at several transmural pressures and lung volumes within ranges that occur during breathing. Aim 2 will develop a computational model to estimate the pressure gradients, blood flow and distribution of blood transit times across individual capillary segments and simulated arteriolar-venular pathways during breathing, as well as determining the effect of a neutrophil temporarily occluding a segment on these parameters in adjacent segments. Aim 3 will determine the site of neutrophils within the bed and shape changes in neutrophils and capillary segments using confocal microscopy. Aim 4 will determine the mechanical properties of quiescent and activated neutrophils, both at their periphery and within their cytoplasm, using magnetic twisting cytometry, which probes facets of neutrophil mechanics not previously studied. The role of the cytoskeleton in determining the mechanical properties will also be examined. Aim 5 will compare computed and observed distributions of neutrophil transit times to determine which mechanical model of neutrophil structure is most consistent with the distribution of neutrophil transit times observed in vivo. Whether changes in the mechanical properties of neutrophils induced by inflammatory stimuli can account for their sequestration within the capillary bed will also be evaluated. These studies will provide new information about the mechanical behavior of the individual capillary segments and the entire bed, as well as the mechanical properties of neutrophils and how they pass through the normal capillary bed, and will help to focus future studies of neutrophil structure and transit. These mechanical events are also critical during the inflammatory process, where activation of neutrophils causes alterations in their mechanical properties and edema formation alters compliance of capillaries.