Respiration in heat stressed camels.

Respiration and heat exchange in relation to brain temperature (Th) and body temperature (Tb) were investigated in four heat stressed camels subjected daily to high temperature (47 degrees C) in a climate chamber while resting when hydrated and dehydrated by approximately 10%, 15% and 20% of initial weight. Diurnally Tb followed patterns described previously. Th was usually 0.

Lung volume changes during respiration in ducks.

The avian lung has been considered to be rigid and to remain isovolumetric during the respiratory cycle. We tested this hypothesis by implanting radiopaque markers of tantalum on the dorsal pulmonary surfaces and ventral pulmonary aponeuroses of Pekin ducks (Anas platyrhynchos) and measuring changes in lung thickness during the respiratory cycle using high speed cineradiography. We found small but regular changes in lung thickness that were synchronous with respiratory phase.

Panting in the emu causes arterial hypoxemia.

The purpose of this study was to determine the effect of heavy thermal panting on arterial oxygen (PaO2) and carbon dioxide (PaCO2) tension in emus. The birds showed no significant change in body temperature during a 3-4 h heat stress caused by increasing ambient air temperature from 21 to 46 degrees C. However, the emus increased their respiratory frequency 10-fold (from 5.

Control of air flow in bird lungs: radiographic studies.

The complex pattern of air flow in the respiratory system of birds suggests that certain sites function as valves. To examine the possibility of mechanical valving, rather than aerodynamic valving, we recorded radiographic images of the orifices where the medioventral secondary bronchi branch from the primary bronchus in resting Pekin ducks. Analysis of the images indicated that the orifices do not change size or shape during the respiratory cycle, suggesting that they function as aerodynamic rather than mechanical valves in directing air flow through the lung.

Desaturation of exhaled air in camels.

We have found that camels can reduce the water loss due to evaporation from the respiratory tract in two ways: (1) by decreasing the temperature of the exhaled air and (2) by removal of water vapour from this air, resulting in the exhalation of air at less than 100% relative humidity (r.h.).

Respiratory water loss in camels.

Rates of oxygen consumption and respiratory water loss were studied in camels that were exposed to desert heat and water deprivation. We found that changes in body temperature are accompanied by considerable changes in respiratory water loss. Body temperature fluctuations are greatest in dehydrated camels (up to 7 degrees C), and in these the respiratory water loss might vary from abut 0.

Nasal heat exchange in the giraffe and other large mammals.

The respiratory air of the giraffe is exhaled at temperatures substantially below body core temperature. As a consequence, the water content of the exhaled air is reduced to levels below that in pulmonary air, resulting in substantial reductions in respiratory water loss. Measurements under outdoor conditions showed that at an ambient air temperature of 24 degrees C, the exhaled air was 7 degrees C below body core temperature, and at ambient air temperature of 17 degrees C, the exhaled air was 13 degrees C below core temperature.

Avian cerebral blood flow: influence of the Bohr effect on oxygen supply.

To clarify the problems of altitude tolerance in birds, we studied the combined effect of hypocapnia and hypoxia on cerebral blood flow (CBF) in ducks. CBF was measured by the xenon clearance method. Normocapnic hypoxia causes CBF to increase when the arterial O2 tension (PaO2) falls below 60--70 mmHg.

Cerebral blood flow in birds: effect of hypoxia.

The effect of hypoxia on cerebral blood flow in ducks was investigated by the rate at which arterially injected xenon-133 was cleared from the duck's brain. A two-component clearance curve resulted, which we have attributed to flow through the grey and white matter. Decreasing the arterial oxygen tension (PaO2) to 75 mmHg had no effect on cerebral blood flow.

Effect of simulated altitude on blood gas transport in the pigeon.

Unacclimated pigeons were exposed to various simulated altitudes. Arterial and mixed venous blood gas levels were measured. At the highest altitude 9150m (Pb = 235 mm Hg) a remarkable degree of alkalosis was tolerated for several hours without ill effecrtant factor in the bird's ability to survive such altitudes.

Effect of arterial carbon dioxide on cerebral blood flow in ducks.

The purpose of this study was to determine the effect of arterial PCO2 on blood flow to the avian brain. Cerebral blood flow was measured on curarized, artificially ventilated Pekin ducks by the rate at which intra-arterially injected xenon-133 was cleared from the duck's brain. A two-component clearance curve resulted: the blood flow calculated from the fast and slow components was similar to the blood flow to mammalian grey and white matter, respectively.

Respiratory responses of ducks to simulated altitude.

Domestic ducks were exposed to simulated altitudes of 0, 3000, 6000, and 9000 m in order to study the respiratory changes that take place. We found that the respiratory minute volume (VE,BTPS) increased with altitude, the increase being due to increased respiratory frequency while tidal volume (VT, BTPS) showed only minor changes. The quantity of air moved (VE, STPD), however, remained nearly unchanged with increasing altitude.

Terrestrial locomotion in penguins: it costs more to waddle.

The energetic cost for walking is relatively higher for penguins than for other birds or for quadrupeds of similar body mass. The morphology of penguins seems to represent a compromise between aquatic and terrestrial locomotion wherein both energy economy and speed suffer when the birds move on land.

Energy expenditure for thermoregulation and locomotion in emperor penguins.

During the antarctic winter emperor penguins (Aptenodytes forsteri) spend up to four mo fasting while they breed at rookeries 80 km or more from the sea, huddling close together in the cold. This breeding cycle makes exceptional demands on their energy reserves, and we therefore studied their thermoregulation and locomotion. Rates of metabolism were measured in five birds (mean body mass, 23.

Heat loss from feet of herring gulls at rest and during flight.

The role of the feet of herring gulls (Larus argentatus) in heat dissipation was estimated during rest and wind-tunnel flight. We determined the blood flow to the feet and the arteriovenous temperature difference and thus estimated heat loss from the feet. Determinations of oxygen consumption and respiratory water loss at rest gave a heat production of about 8 W; 37-56% of this heat was lost from the feet (air temp = 10-35 degrees C).

Scaling in biology: the consequences of size.

A review of major ideas pertaining to the importance of the body size of animals. It discusses the size range of living organisms and the possibilities and constraints that result from the design of animals and the materials used in their supporting structures. The change in size of similarly organized animals is considered in the light of the principles of scaling, with examples chosen both from morphology and physiology.