Figure 1.

Baseline pO₂ relative to diving arterioles and surfacing venules. A, An image of the surface vasculature calculated as a maximum intensity projection of an image stack 0–300 μm in depth obtained using a 4× objective. Individual images were acquired every 10 μm. The fluorescent contrast is due to intravascular FITC. The image on the right shows a zoomed-in view of the region within the red square on the left at the depth plane of pO₂ measurements, 200 μm below the surface. A, Diving arteriole; V, surfacing venule. B, A grid of measured pO₂ values superimposed on the vascular reference image. C, pO₂ as a function of the radial distance from the center of a blood vessel: diving arterioles (left) or surfacing venules (right). The pO₂ values were obtained from grid measurements, as with the example in A and B. Data from multiple vessels from multiple animals are overlaid on each plot.