Comparison of erythrocyte osmotic fragility among ectotherms and endotherms at three temperatures.

1. Comparison of erythrocyte osmotic fragility (EOF) between various ectotherms and endotherms was investigated at 5, 25, and 38 degrees C. 2. We hypothesized that ectotherms might possess erythrocytes whose osmotic fragility would be less affected by temperature than those of endotherms. 3. Ectotherm erythrocytes were much more osmotically resistant than those of endotherms. 4. The EOF of ectotherms and endotherms showed similar responses to temperature. 5. It does not appear that the osmotic fragility of erythrocytes from ectotherms in this study are adapted to be less affected by temperature than those of endotherms. The highly osmotic resistant erythrocytes of ectotherms may alleviate the need for further adaptation for osmotic resistance.

Blood viscosity and hematological changes during prolonged submergence in normoxic water of northern and southern musk turtles (Sternotherus odoratus).

Musk turtles (Sternotherus odoratus) can survive at least 150 days of submergence in normoxic water at 3 degreesC, during which time there are large increases in packed cell volume (PCV). We investigated the effects of submergence in normoxic water at 3 degreesC on the blood viscosity of musk turtles from northern (Massachusetts) and southern (Alabama) locales. Blood was collected from air-breathing turtles and after 20, 50, 100, and 150 days of submergence in normoxic water at 3 degreesC. Hematological responses to submergence were similar in the two groups, therefore the results were combined. Packed cell volume increased steadily above that of controls after 20, 50, 100, and 150 days of submergence. Hemoglobin concentration also progressively increased above that of controls after 20, 50, and 100 days of submergence but declined to near control values after 150 days. Blood viscosity increased with increasing PCV; however, blood viscosity of musk turtles appears less affected by PCV than is blood viscosity of mammalian species. As such, musk turtles appear to be able to maintain adequate blood flow to tissues while increasing the oxygen carrying capacity of the blood during prolonged submergence. However, after 150 days submergence, oxygen delivery should decrease due to a reduced oxygen carrying capacity of the blood and an increased resistance to blood flow, which may limit the length of time these turtles can remain viable during hibernation.

Comparison of blood viscosity in red-eared sliders (Trachemys scripta) adapted to cold and room temperature.

Red-eared sliders (Trachemys scripta) in their northern range undergo hibernation at temperatures of about 5 degrees C, which may result in a profound bradycardia and a drop in blood pressure leading to very slow blood flows. Blood viscosity increases with decreasing temperature and at low shear rates associated with slow blood flows. To investigate the effects of temperature on the blood viscosity of these animals, 20 red-eared sliders were randomly assigned to each of two groups, cold environment (5 degrees C) or room-temperature environment (25 degrees C). At the end of 5 months treatment, hematocrit values, plasma protein concentration, and whole-blood viscosity values were determined for each turtle. Blood viscosity measurements were determined at five shear rates (3.75, 15, 30, 75, and 150 s-1) at 5 degrees C and 25 degrees C for all animals. No significant differences were found in hematocrit or plasma protein values between cold-adapted and room temperature-adapted animals. Whole-blood viscosity between groups at any shear rate at a temperature of 5 degrees C was also nonsignificant. The only significant difference in blood viscosity between turtles adapted to cold and room temperature occurred at a shear rate of 3.75 s-1 at 25 degrees C. The whole-blood viscosity of red-eared sliders, whether adapted to cold or to room temperature, tended to be lower as compared to other vertebrates under similar conditions of temperature, shear rate, and hematocrit. This innate lower blood viscosity may compensate for the potential detrimental effects on blood viscosity brought about by the low temperatures and decreased shear rates that occur in these animals during hibernation.

Stress protein induction in skeletal muscle: comparison of laboratory models to naturally occurring hypertrophy.

The purpose of the study was to compare stress protein [heat shock protein (HSP) 72] response in laboratory models of hypertrophy to naturally occurring work-induced hypertrophy. Two laboratory models of hypertrophy inducement, namely, compensatory hypertrophy and stretch hypertrophy, were compared with hypertrophy resulting from migratory flight in the blue-winged teal. We hypothesized that HSP 72 would be expressed more strongly in hypertrophied muscle than in control muscle. Furthermore, we hypothesized that changes occurring in laboratory models would also occur in work-induced enlargement. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blot analyses were used to assess HSP 72 levels in control and hypertrophied muscle. Laboratory models elicited similar responses, with increased HSP 72 content in hypertrophied muscle. Work-induced hypertrophy or disuse atrophy did not change the degree of HSP 72 expression in the blue-winged teal. The presence of HSP 72 in these conditions may indicate that stressors eliciting changes in muscle protein expression, including the loss of muscle mass, may elicit HSP 72 synthesis.

Exercise performance of birds.

Birds are excellent endurance athletes. Not only do many birds undertake long migratory flights, but many do so under extreme environmental conditions: excessive heat, extreme cold, and the hypoxic conditions of high altitude. We are just now starting to understand the physiological adaptations these animals possess for surviving and thriving in these environments. Still, relatively few studies have actually been performed on exercising birds, particularly on birds flying under the conditions mentioned here. Furthermore, not all birds are capable of sustained exercise in hypoxia, heat, and cold. More work is needed to increase our understanding of the differences in the physiological systems that allow some birds to be better able to exercise under such conditions.