Comparing hypothermia in the human and the black bear (<i>Ursus americanus</i>)

Buresh, Christopher; Folk, G. Edgar; Dickson, Eric W.; Thrift, Diana L.

doi:10.1080/09291010802568756

Cited by 4 publications

(2 citation statements)

References 11 publications

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“…Bears, like most mammals, suffer cardiac electrical disturbances during hypothermia and typically succumb to fatal arrhythmia or asystole at about 18-218C (Buresh et al 2010). It thus appears that only hibernators with small body-mass to surfacearea ratios and small heart sizes, and who inhabit cold environments, display electrophysiological adaptations that allow for continued cardiac function at extremely low body temperatures.…”

Section: Adaptations To Coldmentioning

confidence: 99%

Organ Protective Mechanisms Common to Extremes of Physiology: A Window through Hibernation Biology

Quiñones

Zhang

et al. 2014

Integrative and Comparative Biology

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Supply and demand relationships govern survival of animals in the wild and are also key determinants of clinical outcomes in critically ill patients. Most animals' survival strategies focus on the supply side of the equation by pursuing territory and resources, but hibernators are able to anticipate declining availability of nutrients by reducing their energetic needs through the seasonal use of torpor, a reversible state of suppressed metabolic demand and decreased body temperature. Similarly, in clinical medicine the majority of therapeutic interventions to care for critically ill or trauma patients remain focused on elevating physiologic supply above critical thresholds by increasing the main determinants of delivery of oxygen to the tissues (cardiac output, perfusion pressure, hemoglobin concentrations, and oxygen saturation), as well as increasing nutritional support, maintaining euthermia, and other general supportive measures. Techniques, such as induced hypothermia and preconditioning, aimed at diminishing a patient's physiologic requirements as a short-term strategy to match reduced supply and to stabilize their condition, are few and underutilized in clinical settings. Consequently, comparative approaches to understand the mechanistic adaptations that suppress metabolic demand and alter metabolic use of fuel as well as the application of concepts gleaned from studies of hibernation, to the care of critically ill and injured patients could create novel opportunities to improve outcomes in intensive care and perioperative medicine.

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Section: Adaptations To Coldmentioning

confidence: 99%

Organ Protective Mechanisms Common to Extremes of Physiology: A Window through Hibernation Biology

Quiñones

Zhang

et al. 2014

Integrative and Comparative Biology

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“…The authors concluded that the regulation of T b cycles is not a passive process but rather active regulation. Even though bears do not show periods of arousal, such as other smaller hibernators ( Tøien et al, 2015 ), bears might still need to actively regulate their T b in order to maintain homeostasis and avoid T b below a certain but not fixed threshold, which may lead to cardiac arrhythmia ( Buresh et al, 2010 ). Depending on the insulating properties of the den and snow combination, period lengths of T b may vary between 1.5 and 7 days with an average of 5 days ( Table 3 ).…”

Section: Discussionmentioning

confidence: 99%

Seasonality in Biological Rhythms in Scandinavian brown Bears

et al. 2022

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Biological rhythms, such as rhythms in activity and body temperature, are usually highly synchronized and entrained by environmental conditions, such as photoperiod. However, how the expression of these rhythms changes during hibernation, when the perception of environmental cues is limited, has not yet been fully understood for all hibernators, especially in the wild. The brown bear (Ursus arctos) in Scandinavia lives in a highly seasonal environment and adapts to harsh winter conditions by exhibiting hibernation, characterized by reduced metabolism and activity. In this study, we aimed to explore the expression of biological rhythms in activity, body temperature and heart rate of free-ranging brown bears over the annual cycle, including active, hibernation and the transition states around den entry and exit. We found that rhythms in physiology and activity are mostly synchronized and entrained by the light-dark cycle during the bears’ active state with predominantly diel and ultradian rhythms for body temperature, activity and heart rate. However, during hibernation, rhythms in body temperature and heart rate were considerably slowed down to infradian rhythms, influenced by the amount of snow in the denning area, whereas rhythms in activity remained diel. Rhythms in the transition states when bears prepared for entering or coming out of hibernation state displayed a combination of infradian and diel rhythms, indicating the preparation of the body for the change in environmental conditions. These results reveal that brown bears adjust their biological rhythms to the seasonal environment they inhabit. Rhythms in physiology and activity show simultaneity during the active state but are partly disconnected from each other during hibernation, when bears are most sheltered from the environment.

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Muscle Protein and Strength Retention by Bears During Winter Fasting and Starvation

Harlow

2012

Comparative Physiology of Fasting, Starvation, and Food Limitation

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Comparing hypothermia in the human and the black bear (Ursus americanus)

Cited by 4 publications

References 11 publications

Organ Protective Mechanisms Common to Extremes of Physiology: A Window through Hibernation Biology

Organ Protective Mechanisms Common to Extremes of Physiology: A Window through Hibernation Biology

Seasonality in Biological Rhythms in Scandinavian brown Bears

Muscle Protein and Strength Retention by Bears During Winter Fasting and Starvation

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