MICROVASCULAR DIMENSIONS AND GAS EXCHANGE

微血管大小与血管密度之间的精确关系 气体交换器官扩散特征不佳 明白了。这在很大程度上是由于制造的困难。 气体交换和血管的直接、同时测量 肺部的大小。然而，这样的测量可以很容易地 是在不同的呼吸器官上制造的，两栖动物的皮肤。这 格兰特建议评估气体交换的一些基本原则 通过对两栖动物皮肤进行直接测量来确定 膜对一氧化碳(DMCO)的扩散能力 受毛细血管直径、密度变化的影响 毛细血管灌流，血-气扩散的厚度 障碍。一种使用所有活体测量的新方法将是 进行以确定DMCO和气体吸收能力 当红细胞流过毛细血管时。这些 决定将检验以下假设：1)变化 单独的毛细管径对DMCO没有影响，2)变化 在毛细血管灌流密度方面有较大的影响 在低毛细管密度下的DMCO比在高毛细管密度下的DMCO。 3)随着血-气扩散屏障厚度的增加， 改变灌流后的毛细血管密度对 DMCO公司。扩散能力变化在调控中的作用 还将评估02和CO2在两栖动物皮肤中的交换。 最后，将利用已知的知识开发一个数学模型 描述扩散气体流量的管道热流关系式 穿过两栖动物的皮肤。 实验将在有刺的无尾两栖动物身上进行。这个 C0、C02和02的净通量将通过一个小的 用质谱仪测定皮肤的斑块。DMCO和皮肤电导 至02和二氧化碳将被确定。与这些通量同步 测量，毛细管径和毛细密度 同样的皮肤区域将由视频显微镜确定。 局部应用可引起毛细血管密度的变化 苯肾上腺素对皮肤的影响。毛细管径将会改变 使用泵灌流的皮肤制剂，其中血管内 压力是可以调节的。血-气的厚度 扩散屏障将使用标准组织学方法进行测量 技巧。不同的两栖动物具有不同的表皮 厚度将进行测试和比较。 这项对两栖动物皮肤的研究将提供独特的 有助于理解以下基本问题的信息 尚未在实验中进行的哺乳动物气体交换 由于哺乳动物肺的复杂性，所以可以进入。

Precise relationships between microvascular dimensions and the diffusion characteristics of gas exchange organs are not well understood. This is due, in large part, to difficulties in making direct, simultaneous measurements of gas exchange and vascular dimensions in the lung. Such measurements, however, can readily be made on a different respiratory organ, amphibian skin. This grant proposes to evaluate some basic principles of gas exchange by making direct measurements on amphibian skin to determine how the membrane diffusing capacity to carbon monoxide (DMCO) is affected by changes in capillary diameter, the density of perfused capillaries, the thickness of the blood-air diffusion barrier. A new method using all in vivo measurements will be performed to determine DMCO and the gas uptake capacity of erythrocytes while they flow through capillaries. These determinations will test the following hypotheses: 1) Changes solely in capillary diameter have no affect on DMCO, 2) Changes in the density of perfused capillaries have a larger effect on DMCO at low capillary density than at higher capillary densities. 3) As the thickness of the blood-air diffusion barrier increases, changes in the density of perfused capillaries have less effect on DMCO. The role of diffusing capacity changes in the regulation of 02 and C02 exchange in amphibian skin will also be evaluated. Finally, a mathematical model will be developed using known relationships of heat flux from pipes to describe diffusive gas flux across amphibian skin. Experiments will be performed on pithed anuran amphibians. The net fluxes of C0, C02 and 02 will be measured across a small patch of skin by mass spectrometry. DMCO and skin conductance to 02 and C02 will be determined. Simultaneous with these flux measurements, capillary diameter and capillary density in the same region of skin will be determined by video microscopy. Changes in capillary density will be elicited by topical application of phenylephrine to the skin. Capillary diameters will be altered using a pump-perfused skin preparation in which intravascular pressure can be modulated. The thickness of the blood-air diffusion barrier will be measured using standard histological techniques. Different amphibians with a variety of epidermal thickness 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 the mammalian lung.