Philip C. Withers

The effects of erythrocythemia on blood viscosity, maximal systemic oxygen transport capacity and maximal rates of oxygen consumption in an amphibian.

Summary1.Graded erythrocythemia was induced by isovolemic loading of packed red blood cells in the toad,Bufo marinus. Blood viscosity, hematocrit, hemoglobin concentration, maximal aortic blood flow rate and maximal rates of oxygen consumption were determined after each load.2.Blood viscosity was related to hematocrit in the expected exponential manner; ln η=0.43+0.035 Hct (Fig. 2).3.Maximal blood flow rates in the dorsal aorta were inversely proportional to blood viscosity and fit predictions of the Poiseuille-Hagen flow formula (Fig. 3). The effect of increased blood viscosity was to reduce aortic pulse volume, but not maximal heart rate (Figs. 4, 5).4.Maximal systemic oxygen transport capacity (aortic blood flow rate x hemoglobin concentration x O2 binding capacity of hemoglobin) was linearly correlated with the maximal rate of oxygen consumption (Fig. 6).5.These data indicate that optimal hematocrit theory is applicable for maximal blood flow rates in vivo, and that systemic oxygen transport is the primary limitation to aerial n

The hemodynamic consequences of hemorrhage and hypernatremia in two amphibians

dot V_{O_2 }

Allometry of respiratory and haematological parameters of arctic mammal

n max in amphibians.

Effects of activity, hemorrhage, and dehydration on plasma catecholamine levels in the marine toad (Bufo marinus)

Summary1.The rate of oxygen consumption for honeybees hovering at normal air pressure was 94.3 ml O2 g−1 h−1. The rate of oxygen consumption declined for honeybees hovering at higher air pressures, and declined for bees hovering at pressures less than 600 Torr.2.The rate of oxygen consumption by resting honeybees was slightly, but significantly, affected by air pressure. Mean resting rate of oxygen consumption at normal air pressure was 12.3 ml O2 g−1 h−1.3.The rate of oxygen consumption for honeybees during a 30 min peroid after hovering was 3.0 ml O2 g−1 h−1 at normal pressure, and increased slightly but significantly, at lower pressures.4.Thoracic temperature was maintained relatively constant at 31–33°C during hovering, and was slightly, but significantly, elevated at lower air pressures.5.The decline in rate of oxygen consumption for honeybees hovering at high pressure is attributed to decreased power requirements for flight, whereas the decline in rate of oxygen consumption at low pressures is attributed to the limitation of lown

The effects of hypoxia on pulmonary function and maximal rates of oxygen consumption in two anuran amphibians

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Optimal hematocrit theory during activity in the bullfrog (Rana catesbeiana)

n to oxygen transport capacity.6.The rate of change in oxygen consumption at low air pressures suggests that the inertial power requirement for hovering flight is about 60 ml O2 g−1 h−1 whereas the aerodynamic power requirement is about 33 ml O2 g−1 h−1.