Roy F. Burlington

Gluconeogenesis during hibernation and arousal from hibernation.

Abstract 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.

Low-Temperature Performance of Isolated Working Hearts from a Hibernator and a Nonhibernator

An isolated working heart preparation was used to measure the effect of low temperatures on cardiac output (CO), oxygen consumption (

Distribution and activity of lactic dehydrogenase isozymes in tissues from a hibernator and a non-hibernator.

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Red cell 2,3-diphosphoglycerate in hibernating ground squirrels

), coronary flow (CF), and aortic systolic and diastolic pressure development in hearts from rats and 13-lined ground squirrels (Spermophilus tridecemlineatus). Cardiac efficiency (CE) was calculated using these data (CE = energy output [KCal/h/g]/energy input [KCal/h/ g]). Below 20 C, rat hearts became arrhythmic and were unable to produce CO. Cardiac arrest occurred at 16.5 ± 0.8 C. Squirrel heart CO decreased progressively as temperature was lowered, but these hearts produced CO at 7 C. A declining spontaneous heart rate was compensated for by increased stroke volume. Mean aortic pressure (MAP) declined in rat hearts between 37 and 20 C, but MAP was maintained in squirrel hearts regardless of temperature. Cardiac efficiency increased slightly (10%-18%) in hearts from both species as temperature was lowered from 37 to 27 C, but squirrel heart CE increased by 60% when temperature was reduced from 17 to 7 C. The proportion of CO devoted to CF was significantly increased at lower temperatures in squirrel hearts but not in rat hearts. The ground squirrel heart has an intrinsic capacity to reapportion CF, make a more efficient use of metabolic fuel, and maintain CO and MAP at low temperatures. These adaptations support survival during deep and sustained hibernation.

Lipid changes in isolated brown fat cells from hibernating and aroused thirteen-lined ground squirrels (Citellus tridecemlineatus).

1. 1. The total enzyme activity and the electrophoretic distribution of lactic dehydrogenase (LDH) isozymes were determined in heart, brain, liver and skeletal muscle from normothermic and hibernating ground squirrels (Citellus tridecemlineatus) and normothermic albino rats. 2. 2. During hibernation, the proportion of M-type subunits increased significantly in cardiac tissue. When measured at 32°C, total and M-type LDH activity was increased markedly in liver, brain and heart tissue from hibernating animals. These differences were not apparent in the heart and brain at 15°C. 3. 3. LDH isozyme distribution and enzyme activity appear to be associated with adaptive metabolic changes during hibernation.

Anaerobic glycolysis in cardiac tissue from a hibernator and non-hibernator as effected by temperature and hypoxia

Abstract 1. 1. Red cell 2, 3-diphosphoglycerate (2,3-DPG) and hemoglobin were measured in blood from hibernating and normothermic thirteen-lined ground squirrels (Citellus tridecemlineatus) and golden-mantled ground squirrels (Citellus lateralis). 2. 2. Blood from hibernating animals contained significantly less 2, 3-DPG but hemoglobin content was not different. These data provide a basis for the hypothesis that hemoglobin from hibernating animals has an increased affinity for oxygen at 37°C.

Effect of hypoxia on glycolysis in perfused hearts from rats and ground squirrels (Citellus lateralis)

Abstract 1. 1. Increased brown fat mass occurs in mammalian hibernators after cold exposure. 2. 2. The increased tissue mass results primarily from deposition of neutral lipids in existing fat cells and from increased tissue water. 3. 3. Arousal from hibernation elicits mobilization of neutral lipids which are presumably utilized to support thermogenesis.

The Effect of Temperature on Glycolysis in Brain and Skeletal Muscle from a Hibernator and a Non-Hibernator

Abstract 1. 1. Rates of anaerobic glycolysis were measured in cardiac tissue from hypoxic ground squirrels (Citellus tridecemlineatus) and albino rats. 2. 2. After hypoxia glycolysis increased significantly in both species at 38°C. At temperatures from 5 to 38°C glycolytic rates were significantly higher in tissue from control active (summer) or hibernating (winter) ground squirrels as compared to control rats. Glycolysis increased significantly during hibernation. 3. 3. At low temperatures energies of activation (EA) for glycolysis in rat tissue were higher than those in ground squirrel tissue. 4. 4. Interspecific differences in glycolytic rates support the hypothesis that the hibernator is better adapted to hypoxia and hypothermia than the homeotherm.

EFFECT OF HYPOXIA ON CEREBRAL ANAEROBIC GLYCOLYSIS IN THE HIBERNATOR AND INFANT OR ADULT HOMEOTHERM.

Abstract 1. 1. Tissue levels of adenine nucleotides and selected glycotic intermediates were measured in isolated hearts from rats and squirrels during the transition from aerobiosis to anaerobiosis. 2. 2. Hypoxia elicited significant decreases in ATP and creatine phosphate with concomitant increases in ADP, AMP and inorganic phosphate. Compared to controls, the apparent activity of phosphofructokinase (PFK) increased markedly in hypoxic hearts from both species. Durong hypoxia, significantly higher PFK activity and lactate production were observed in the rat heart. 3. 3. During hypoxia, the rate of anaerobic glycolysis is greater in rat myocardial tissue. Control of glycolysis at the PFK reaction is similar in both species.

A quantitative evaluation of pollution effects on stream communities

M AMMALIAN hibernation represents a unique adaptation to extended periods of thermal stress. Natural hibernators attain a state of deep torpor during the winter, and their physiological integrity is maintained at body temperatures (5 + 3 C) that adult homeotherms cannot survive. Thus it seems reasonable to postulate that hibernators possess cellular adaptations to cold that are not found in the non-hibernator. This hypothesis is supported by South (1958), who investigated oxygen consumption in heart ventricle tissue from hamsters and albino