CAPILLARY HEMATOCRIT AND GAS EXCHANGE

这项建议的主要目标是确定 毛细血管线形红细胞密度(Droc)对扩散性气体输送的影响 组织。毛细血管指标--毛细血管线形红细胞密度 红细胞压积，可以在3倍的范围内迅速变化 条件。然而，它在气体交换中的确切作用目前尚不清楚。 对两栖动物皮肤的研究将确定：1)扩散的依赖性 在不同的表皮厚度下，Droc上通过表皮的气体流量， 2)毛细血管内红细胞间距的异质性及其影响 这种非均质性对扩散气体传输的影响，以及3)对 无基质替代红细胞的组织扩散能力 血红蛋白溶液。这将通过测试以下各项来实现 关于青蛙皮肤的假设：1)Droc的变化影响组织扩散 低Droc时的CO容量(DtCO)高于高Droc时的DtCO2)作为表皮 厚度增加，Droc的变化对DtCO的影响较小。3) 毛细血管红细胞间距的不均一性是影响 DtCO。4)用无基质的血红蛋白溶液替代红细胞 增加D，Co.5)随着表皮厚度的增加，取代红细胞 使用无基质的血红蛋白溶液对DtCO影响较小。6) 结合真实几何并通过有限元求解的数学模型 元素分析可以描述两栖动物皮肤上的气体扩散通量。 所有实验都将在麻醉的(氨基甲酸酯)两栖动物上进行。公司 将通过质谱仪测量一小块皮肤上的通量 DtCO的计算。同时，下列微循环 参数将用荧光在皮肤的同一区域进行测量 视频显微镜： Droc、毛细血管细胞间距、毛细血管灌流密度、红细胞速度 和毛细血管体积。在测试假设1-3时，~~将被更改 血液稀释和血液浓缩。在测试假设4和5时，RED 细胞将被一种无基质的人血红蛋白交叉溶液所取代- 链接在阿尔法链之间。这种血红蛋白已经被用于 试验性地作为血液替代品。不同种类的两栖动物 表皮厚度的比例将被测试和比较。 这项对两栖动物皮肤的研究将提供独特的信息 有助于理解哺乳动物气体交换的基本问题 尚未在实验中访问，因为大多数 纸巾。这项研究的结果将有助于更好地理解 1)毛细血管红细胞压积和极大红细胞压积的意义 此参数中发生的快速变化，以及2) 血液替代品在扩散的气体运输上。

The primary goal of this proposal is to determine the precise effect of the lineal red cell density in capillaries (droc) on diffusive gas transport in tissue. Capillary lineal red cell density, an index of capillary tube hematocrit, can vary rapidly over a 3-fold range under different conditions. However, its precise role in gas exchange is presently unclear. Studies on amphibian skin will determine: 1) the dependence of diffusive gas flux across the epidermis on droc at different epidermal thicknesses, 2)the heterogeneity in red cell spacing within capillaries and the effects of this heterogeneity on diffusive gas transport, and 3) the effect on tissue diffusing capacity of replacing red cells with a stroma-free hemoglobin solution. This will be accomplished by testing the following hypotheses on frog skin: 1) Changes in droc affect the tissue diffusing capacity to CO (DtCO) more at low droc than at high droc. 2) As epidermal thickness increases, changes in droc have less effect on DtCO. 3) The heterogeneity of capillary red cell spacing is an important determinant of DtCO. 4) Replacement of red cells with a stroma-free hemoglobin solution augments D,CO. 5) As epidermal thickness increases, replacing red cells with a stroma-free hemoglobin solution has less effect on DtCO. 6) Mathematical models incorporating realistic geometries and solved by finite element analysis can describe diffusive gas flux across amphibian skin. All experiments will be performed on anesthetized (urethane) amphibians. CO flux will be measured across a small patch of skin by mass spectrometry for calculation of DtCO. Simultaneously, the following microcirculatory parameters will be measured on the same region of skin with fluorescent video microscopy: droc, capillary cell spacing, perfused capillary density, red cell velocity and capillary volume. In testing Hypotheses 1-3, ~~ will be altered by hemodilution and hemoconcentration. In testing Hypotheses 4 and 5, red cells will be replaced by a stroma-free solution of human hemoglobin cross- linked between the alpha chains. This hemoglobin has been used experimentally as a blood substitute. Different amphibians with a variety of epidermal thicknesses will be tested and compared. This investigation of amphibian skin will provide unique information helpful to the understanding of basic issues in mammalian gas exchange that have not been experimentally accessible because of the complexity of most tissues. The results of this research will lead to a better understanding of 1) the significance of capillary hematocrit and the very large and rapid changes that occur in this parameter, and 2) the precise effects of blood substitutes on diffusive gas transport.