Liver energy metabolism during hibernation in the golden-mantled ground squirrel, Spermophilus lateralis

1997 ◽  
Vol 75 (7) ◽  
pp. 1059-1065 ◽  
Author(s):  
James F. Staples ◽  
Peter W. Hochachka
Keyword(s):  
Ground Squirrels ◽  
Atp Production ◽  
Spermophilus Lateralis ◽  
Energy Demands ◽  
Hormone Status ◽  
Consumption Rates ◽  
Lower Temperature ◽  
Production Capacities ◽  
Deep Hibernation ◽  
Normothermic Condition

Large changes in ATP production capacities and rates have been reported in mammalian hibernators throughout the different stages of the hibernation cycle. In this study we showed that total extractable liver [ATP], [ADP], and [ATP]/[ADP] do not differ among summer normothermic, hibernating, and aroused golden-mantled ground squirrels, Spermophilus lateralis, indicating that metabolism remains well balanced throughout the hibernation cycle. This implies that rates of ATP consumption must be down-regulated during deep hibernation in order to maintain this balance. Despite this, basal oxygen-consumption rates [Formula: see text] of hepatocytes isolated from hibernating, aroused, and summer cold-acclimated ground squirrels were 22.4–35.1% higher than those from ground squirrels in the summer normothermic condition when measured at 37 °C. The relatively high hepatocyte [Formula: see text] may help to minimize interbout arousal times, reducing energy demands during the hibernation season. At 7 °C, hepatocyte [Formula: see text] values do not differ among the four groups; however, the Q10 for hepatocyte [Formula: see text] is significantly lower for the summer group, suggesting lower temperature sensitivity. Despite the seasonal changes in thyroid hormone status known to occur in scuirid hibernators, the proportion of hepatocyte [Formula: see text] attributed to Na+,K+-ATPase, estimated by inhibition with 1 mM ouabain, is only around 15% and does not differ among hibernation/seasonal conditions.

Are ground squirrels sleep deprived during hibernation?

1991 ◽  
Vol 260 (6) ◽  
pp. R1123-R1129 ◽  
Author(s):  
L. Trachsel ◽  
D. M. Edgar ◽  
H. C. Heller
Keyword(s):  
Slow Wave ◽  
Slow Wave Sleep ◽  
Ground Squirrels ◽  
Wave Intensity ◽  
Spermophilus Lateralis ◽  
Sleep Debt ◽  
Function Of Sleep ◽  
Deep Hibernation ◽  
To Receive ◽  
Periodic Arousals

Hibernation is an adaptation for energy conservation, which probably evolved as an extension of non-rapid-eye-movement sleep mechanisms. Yet, during periodic arousals from bouts of deep hibernation, ground squirrels (Spermophilus lateralis) spend most of their time asleep. Spectral analysis of the electroencephalogram revealed that cortical slow-wave intensity during sleep is high at the beginning of a euthermic period and declines thereafter. Sleep slow-wave intensity is greater after longer bouts of hibernation than after shorter bouts. We hypothesize that low body temperatures during hibernation are incompatible with the restorative function of sleep as reflected in cortical slow-wave activity. Animals must incur the energetic costs of periodic arousals from hibernation to receive the restorative benefits of euthermic slow-wave sleep. The timing of arousals from hibernation may be a function of accumulated sleep debt.

Neuronal activity during sleep and complete bouts of hibernation

1988 ◽  
Vol 255 (6) ◽  
pp. R1008-R1019 ◽  
Author(s):  
B. L. Krilowicz ◽  
S. F. Glotzbach ◽  
H. C. Heller
Keyword(s):  
Eye Movement ◽  
Neuronal Activity ◽  
Neural Control ◽  
Nrem Sleep ◽  
Ground Squirrels ◽  
Homogeneous State ◽  
Rapid Eye Movement ◽  
Spermophilus Lateralis ◽  
Regulatory Systems ◽  
Deep Hibernation

Changes in arousal state in a euthermic mammal exert powerful influences on major neural regulatory systems. Changes in behavioral state occur at body temperature (Tb) greater than 25 degrees C during hibernation. However, no information exists regarding alterations in arousal states during deep torpor. In this study we used a combination of electroencephalographic, electromyographic, and posterior thalamic neuronal activity in ground squirrels (Spermophilus lateralis) to evaluate arousal states during deep hibernation. No state homologous to rapid-eye-movement sleep was observed below Tb = 21 degrees C during hibernation. However, the animals did continue to cycle through states homologous to electrophysiologically defined wakefulness (AW) and non-rapid-eye-movement (NREM) sleep at all temperatures examined (Tb = 14-36 degrees C). These results extend previous observations that hibernation is not a homogeneous state. Instead, deep torpor consists primarily of a state similar to NREM sleep, interrupted periodically by short intervals of a form of AW. These periodic alterations in state should be accompanied by changes in the properties of many regulatory systems and must be accounted for in any theory of the neural control of hibernation.

scholarly journals Bottlenecks and rescue effects in a fluctuating population of golden-mantled ground squirrels (Spermophilus lateralis)

2010 ◽  
Vol 12 (1) ◽  
pp. 285-296 ◽  
Author(s):  
Mary Brooke McEachern ◽  
Dirk H. Van Vuren ◽  
Chris H. Floyd ◽  
Bernie May ◽  
John M. Eadie
Keyword(s):  
Ground Squirrels ◽  
Spermophilus Lateralis

scholarly journals Bone strength is maintained after 8 months of inactivity in hibernating ground squirrels, Spermophilus lateralis

2008 ◽  
Vol 22 (S1) ◽  
Author(s):  
Jenifer C. Utz ◽  
Stacy Nelson ◽  
Brendan J. O'toole ◽  
Frank Breukelen
Keyword(s):  
Bone Strength ◽  
Ground Squirrels ◽  
Spermophilus Lateralis

Abstract 16: Progressive Alterations Of Mitochondrial Bioenergetics In The Kidney During The Development Of Salt-induced Hypertension

Hypertension ◽  
2020 ◽  
Vol 76 (Suppl_1) ◽  
Author(s):  
Namrata Tomar ◽  
Sunil M Kandel ◽  
Xiao Zhang ◽  
Nadezhda Zheleznova ◽  
Allen W Cowley ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Complex Disease ◽  
Atp Synthesis ◽  
Control Group ◽  
Mitochondrial Uncoupling ◽  
Knock Out ◽  
Atp Production ◽  
Consumption Rates ◽  
Mitochondrial Efficiency ◽  
Salt Sensitive Hypertension

Hypertension is a complex disease and a leading cause of morbidity and mortality globally. Although oxidative stress and mitochondrial dysfunction have been found in the kidney in various models of hypertension, progressive alteration of mitochondrial oxidative phosphorylation (OxPhos) in the kidney during the development of salt-sensitive hypertension has not been characterized. The present study determined changes of OxPhos in kidneys of Dahl salt-sensitive (SS) rats before (0.4% NaCl diet; LS) and after switching to a high salt diet (4.0% NaCl; HS) during the development of hypertension. Mitochondria were isolated from the outer medulla (OM) and cortex of the kidney of SS rats fed a LS diet since weaning and studied at days 3, 7, 14 & 21 of a HS diet feeding. Oxygen consumption rates (OCR) were measured in mitochondria energized with pyruvate + malate as substrates for three different respiratory states using an Oroboros Oxygraph-2k Instrument. This includes i) leak state (in the absence of ADP), ii) ADP-stimulated state, and iii) uncoupled state (in the presence of an uncoupler FCCP). A biphasic pattern of ADP-stimulated OCR with progressive uncoupling was observed in both the renal OM and cortex. Mitochondrial efficiency for ATP synthesis was increased in the early phases of hypertension (3 & 7 days) but was severely compromised in the established phases of hypertension (14 & 21 days). This decreased mitochondrial efficiency was associated with uncoupling of OxPhos and high levels of oxidative stress which we hypothesized were due to mitochondrial ROS stimulation of membrane NOXs. To test this, experiments were performed in SS rats with double knock out (DKO) of the cytosolic subunit of NOX2 (p67 phox ) and NOX4 (SS p67phox-/-/Nox4-/- ). DKO SS rats were fed a HS diet and OCR of renal cortical and OM mitochondria was determined at days 7 and 14. In contrast to SS rats, the DKO SS rats fed a HS diet showed no significant differences in mitochondrial OCR in the cortex or OM, nor to a control group maintained on a LS diet. HS diet in SS rats initially increases the efficiency of renal cortical and medullary mitochondrial ATP production (days 1-7) followed by an enhanced ROS production with mitochondrial uncoupling and reduced efficiency of ATP production by the third week.

Rates of glucose utilization in brain of active and hibernating ground squirrels

1995 ◽  
Vol 268 (2) ◽  
pp. R445-R453 ◽  
Author(s):  
K. U. Frerichs ◽  
G. A. Dienel ◽  
N. F. Cruz ◽  
L. Sokoloff ◽  
J. M. Hallenbeck
Keyword(s):  
Glucose Utilization ◽  
Specific Activity ◽  
Ground Squirrels ◽  
Cold Adapted ◽  
Precursor Pool ◽  
Glucose Levels ◽  
Operational Equation ◽  
Dg Method ◽  
Deep Hibernation ◽  
Cerebral Structures

Rates of glucose utilization (CMRGlc) were determined in some cerebral structures of active warm- and cold-adapted ground squirrels and hibernating ground squirrels with [14C]deoxyglucose (DG) by direct chemical measurement of precursor and products in samples dissected from funnel-frozen brain. The rate of supply relative to demand of glucose and [14C]DG in brain of hibernating animals was similar to or greater than that of controls. [14C]DG cleared from the plasma in hibernators much more slowly than in active animals, and the level of unmetabolized [14C]DG in brain and the integrated specific activity of the precursor pool in plasma exceeded those of the active animals by 4- to 10-fold. At 45 min after an intravenous pulse of [14C]DG, the unmetabolized [14C]DG remaining in the brains of the hibernators accounted for approximately 96% of the total 14C compared with approximately 10-15% in the active animals. The value of lambda, a factor contained in the lumped constant of the operational equation of the [14C]DG method, was estimated for each animal and found to be relatively constant over the sixfold range of glucose levels in the brains of all animals. Calculated CMRGlc in squirrels in deep hibernation was only 1-2% of the values in active animals.

scholarly journals Spatial control of neuronal metabolism through glucose-mediated mitochondrial transport regulation

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Anamika Agrawal ◽  
Gulcin Pekkurnaz ◽  
Elena F Koslover
Keyword(s):  
Spatial Organization ◽  
Metabolic Response ◽  
Limited Range ◽  
Projection Neurons ◽  
Glucose Levels ◽  
Energy Demands ◽  
Consumption Rates ◽  
Mitochondrial Distribution ◽  
Organelle Trafficking ◽  
Spatially Varying

Eukaryotic cells modulate their metabolism by organizing metabolic components in response to varying nutrient availability and energy demands. In rat axons, mitochondria respond to glucose levels by halting active transport in high glucose regions. We employ quantitative modeling to explore physical limits on spatial organization of mitochondria and localized metabolic enhancement through regulated stopping of processive motion. We delineate the role of key parameters, including cellular glucose uptake and consumption rates, that are expected to modulate mitochondrial distribution and metabolic response in spatially varying glucose conditions. Our estimates indicate that physiological brain glucose levels fall within the limited range necessary for metabolic enhancement. Hence mitochondrial localization is shown to be a plausible regulatory mechanism for neuronal metabolic flexibility in the presence of spatially heterogeneous glucose, as may occur in long processes of projection neurons. These findings provide a framework for the control of cellular bioenergetics through organelle trafficking.

Increased heat loss affects hibernation in golden-mantled ground squirrels

2004 ◽  
Vol 287 (1) ◽  
pp. R167-R173 ◽  
Author(s):  
Alexander S. Kauffman ◽  
Matthew J. Paul ◽  
Irving Zucker
Keyword(s):  
Food Intake ◽  
Heat Loss ◽  
Body Mass ◽  
Complete Removal ◽  
Ground Squirrels ◽  
Control Procedure ◽  
Ambient Temperatures ◽  
Spermophilus Lateralis ◽  
Maintain Body Temperature ◽  
Body Heat

During hibernation at ambient temperatures (Ta) above 0°C, rodents typically maintain body temperature (Tb) ∼1°C above Ta, reduce metabolic rate, and suspend or substantially reduce many physiological functions. We tested the extent to which the presence of an insulative pelage affects hibernation. Tb was recorded telemetrically in golden-mantled ground squirrels ( Spermophilus lateralis) housed at a Ta of 5°C; food intake and body mass were measured at regular intervals throughout the hibernation season and after the terminal arousal. Animals were subjected to complete removal of the dorsal fur or a control procedure after they had been in hibernation for 3–4 wk. Shaved squirrels continued to hibernate with little or no change in minimum Tb, bout duration, duration of periodic normothermic bouts, and food intake during normothermia. Rates of rewarming from torpor were, however, significantly slower in shaved squirrels, and rates of body mass loss were significantly higher, indicating increased depletion of white adipose energy stores. An insulative pelage evidently conserves energy over the course of the hibernation season by decreasing body heat loss and reducing energy expenditure during periodic arousals from torpor and subsequent intervals of normothermia. This prolongs the hibernation season by several weeks, thereby eliminating the debilitating consequences associated with premature emergence from hibernation.

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