Normothermic Squirrels Research Articles

Ground squirrel splenic macrophages bind lipopolysaccharide over a wide range of temperatures at all phases of their annual hibernation cycle

This study evaluates binding of bacterial lipopolysaccharide (LPS) by splenic macrophages from golden-mantled ground squirrels (Spermophilus lateralis, GMGS), a hibernating mammal, at a variety of in vitro incubation temperatures to determine whether this aspect of immune function is effective at low body temperatures. LPS-binding by ground squirrel macrophages was compared to that of rat splenic macrophages. Macrophages were collected from squirrels at discreet stages in their annual cycle and incubated with fluorescein-labeled LPS (LPS-FITC). The percentage of GMGS that bound LPS-FITC did not change as a function of hibernation season or as a function of incubation temperature. The total amount of LPS-FITC bound per cell was similarly unaffected by season or temperature, however, macrophages from torpid squirrels bound more LPS-FITC than cells from normothermic squirrels. Macrophages of golden-mantled ground squirrels bind LPS at a wide range of temperatures throughout their annual cycle; an ability shared between hibernators and non-hibernators alike.

Urine concentrating ability of arousing and normothermic ground squirrels ( Spermophilus columbianus)

1. 1. Determinations of T CH 2O indicate that the urine concentrating ability of ground squirrels ( Spermophilus columbianus) arousing from torpor is similar to that of normothermic squirrels. 2. 2. When squirrels were infused with an osmotic diuretic (1·5% NaCl) the arousing animals demonstrated a maximum T CH 2O whereas no maximum was reached at similar urine flows induced in normothermic squirrels. 3. 3. Urea clearances in infused arousing squirrels were generally much less than those in normothermic squirrels at high urine flows suggesting that restoration of the renal medullary osmotic gradient of arousing animals may be slowed by infusion.

Gluconeogenesis during hibernation and arousal from hibernation

1. 1. In the ground squirrel, Citellus tridecemlineatus, liver glycogen and blood glucose decreased during hibernation. Two hours after arousal, liver glycogen remained low but blood glucose was normal. 2. 2. When incubated at 6°C, kidney cortex slices from hibernating animals had a greater capacity for gluconeogenesis from α-ketoglutarate, l-glutamate, l-aspartate, glycerol, oxaloacetate, l-lactate and pyruvate than renal tissue from normothermic squirrels. At 40°C, glucose synthesis from l-aspartate, glycerol, l-lactate, oxaloacetate and pyruvate was significantly increased in renal tissue from hibernating and arousing animals. 3. 3. Hibernation and arousal were associated with significantly increased hepatic and renal lactic dehydrogenase and hepatic glutamic-oxaloacetic transaminase activities but glucose-6-phosphatase and fructose-1,6-diphosphatase activities remained unchanged. 4. 4. The role of gluconeogenesis during hibernation and arousal is discussed.