Homeostasis during hibernation in the golden-mantled ground squirrel, Citellus lateralis

Pengelley, Eric T.; Asmundson, Sally J.; Uhlman, Christine

doi:10.1016/0300-9629(71)90131-9

Cited by 15 publications

(9 citation statements)

References 10 publications

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“…Bears maintain constant serum calcium levels even though they are anuric and do not eat or drink during hibernation (Nelson, 1987;Floyd et al, 1990), and thus may have evolved the ability to maintain balanced bone remodeling to prevent hypercalcemia during hibernation. In contrast, other hibernators, such as ground squirrels, interrupt torpor bouts with periodic arousals to euthermia, during which they excrete calcium-containing waste (Hock, 1957;Bruce and Wiebers, 1970;Lesser et al, 1970;Pengelley et al, 1971). This provides a potential avenue for calcium and other products of bone catabolism to be excreted from the body, as occurs during other disuse situations such as human bedrest (LeBlanc et al, 1995;Inoue et al, 2000).…”

Section: Discussionmentioning

confidence: 99%

“…In contrast, small hibernating mammals arouse, raise their body temperature and excrete waste every 3-25days during hibernation (Hock, 1957;Lesser et al, 1970;Carey et al, 2003). Urination, for example, occurs during interbout arousal periods in Columbian ground squirrels (Moy, 1971), and urine produced during hibernation is known to contain calcium (Pengelley et al, 1971;Shackelford and Caire, 1993). Thus, small mammals have a mechanism by which calcium liberated from bone during hibernation could be excreted from the body, and therefore these animals may not have evolved the ability to maintain balanced bone remodeling activity and prevent bone loss as hibernating bears do .…”

Section: Introductionmentioning

confidence: 99%

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Thirteen-lined ground squirrels (Ictidomys tridecemlineatus) show microstructural bone loss during hibernation but preserve bone macrostructural geometry and strength

McGee‐Lawrence

Stoll

Mantila

et al. 2011

Journal of Experimental Biology

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SUMMARYLack of activity causes bone loss In most animals. Hibernating bears have physiological processes to prevent cortical and trabecular bone loss associated with reduced physical activity, but different mechanisms of torpor among hibernating species may lead to differences in skeletal responses to hibernation. There are conflicting reports regarding whether small mammals experience bone loss during hibernation. To investigate this phenomenon, we measured cortical and trabecular bone properties in physically active and hibernating juvenile and adult 13-lined ground squirrels (Ictidomys tridecemlineatus, previous genus name Spermophilus). Cortical bone geometry, strength and mineral content were similar in hibernating compared with active squirrels, suggesting that hibernation did not cause macrostructural cortical bone loss. Osteocyte lacunar size increased (linear regression, P0.001) over the course of hibernation in juvenile squirrels, which may indicate an osteocytic role in mineral homeostasis during hibernation. Osteocyte lacunar density and porosity were greater (+44 and +59%, respectively; P<0.0001) in hibernating compared with active squirrels, which may reflect a decrease in osteoblastic activity (per cell) during hibernation. Trabecular bone volume fraction in the proximal tibia was decreased (-20%; P0.028) in hibernating compared with physically active adult squirrels, but was not different between hibernating and active juvenile squirrels. Taken together, these data suggest that 13-lined ground squirrels may be unable to prevent microstructural losses of cortical and trabecular bone during hibernation, but importantly may possess a biological mechanism to preserve cortical bone macrostructure and strength during hibernation, thus preventing an increased risk of bone fracture during remobilization in the spring.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Thirteen-lined ground squirrels (Ictidomys tridecemlineatus) show microstructural bone loss during hibernation but preserve bone macrostructural geometry and strength

McGee‐Lawrence

Stoll

Mantila

et al. 2011

Journal of Experimental Biology

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“…The effects of hibernation on serum calcium levels are difficult to discern because considerable variation is reported in the literature. Compared with active controls, serum calcium is elevated in hibernating hamsters (54), has been reported to either increase (20,99) or decrease (151,152) in hibernating little brown bats, and remains constant in hibernating ground squirrels during 6 days of continuous torpor and during extended hibernation interrupted by periodic arousals (144). Variation between studies is likely influenced by factors like species differences, food availability, hibernation length, and sampling time relative to interbout arousal periods.…”

Section: Calcium Recycling and Hibernation-induced Bone Lossmentioning

confidence: 97%

“…Small mammals excrete waste, which contains calcium, during interbout arousals from torpor (20,(143)(144)(145)161). This calcium may be liberated from bone as a direct response to reduced skeletal loading during hibernation.…”

Section: Calcium Recycling and Hibernation-induced Bone Lossmentioning

confidence: 98%

Mammalian hibernation as a model of disuse osteoporosis: the effects of physical inactivity on bone metabolism, structure, and strength

McGee‐Lawrence¹,

Carey²,

Donahue³

2008

American Journal of Physiology-Regulatory, Integrative and Comp

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Reduced skeletal loading typically leads to bone loss because bone formation and bone resorption become unbalanced. Hibernation is a natural model of musculoskeletal disuse because hibernating animals greatly reduce weight-bearing activity, and therefore, they would be expected to lose bone. Some evidence suggests that small mammals like ground squirrels, bats, and hamsters do lose bone during hibernation, but the mechanism of bone loss is unclear. In contrast, hibernating bears maintain balanced bone remodeling and preserve bone structure and strength. Differences in the skeletal responses of bears and smaller mammals to hibernation may be due to differences in their hibernation patterns; smaller mammals may excrete calcium liberated from bone during periodic arousals throughout hibernation, leading to progressive bone loss over time, whereas bears may have evolved more sophisticated physiological processes to recycle calcium, prevent hypercalcemia, and maintain bone integrity. Investigating the roles of neural and hormonal control of bear bone metabolism could give valuable insight into translating the mechanisms that prevent disuse-induced bone loss in bears into novel therapies for treating osteoporosis.

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“…This means that individuals challenged at the same time with the same antigen may not produce a peak immune response at the same time. Continuous monitoring of circulating antibodies via a method such as aortic cannulation (Pengelley, Asmundson & Uhlman 1971) would help to determine the peak of humoral response in hibernators.…”

mentioning

confidence: 99%

Does immune challenge affect torpor duration?

Burton

Reichman

1999

Functional Ecology

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Summary 1.Hibernation may alter the relationship between pathogens and their hosts; low host temperatures can prevent pathogen replication. Therefore, manipulating the timing and duration of torpor bouts could allow animals to gain an advantage over pathogens. 2. Thirty-two Turkish Hamsters (Mesocricetus brandti) were placed in short-day, cold conditions. After 10 weeks, 20 animals were challenged with an antigen to simulate a pathogen infection. Ten of these animals were returned to the cold ('cold-challenged'). The other 10 animals were placed in warm conditions ('warm-challenged'). Twelve animals received saline injections and were returned to the cold ('cold-control'). Coldchallenged animals spent significantly more time in torpor than did cold-control animals. 3. After 6·5 weeks, all animals were housed in warm conditions and ceased torpor. Both cold-challenged and warm-challenged animals received a second injection of antigen. There was no correlation between time spent euthermic and level of secondary humoral response of cold-challenged animals. The secondary humoral response of the cold-challenged animals was significantly lower than that of warm-challenged animals. 4. In this study immune status influenced torpor duration, and torpor caused immunosuppression. Hibernators may manipulate body temperature in order to combat pathogens while their own immune systems are suppressed.

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Homeostasis during hibernation in the golden-mantled ground squirrel, Citellus lateralis

Cited by 15 publications

References 10 publications

Thirteen-lined ground squirrels (Ictidomys tridecemlineatus) show microstructural bone loss during hibernation but preserve bone macrostructural geometry and strength

Thirteen-lined ground squirrels (Ictidomys tridecemlineatus) show microstructural bone loss during hibernation but preserve bone macrostructural geometry and strength

Mammalian hibernation as a model of disuse osteoporosis: the effects of physical inactivity on bone metabolism, structure, and strength

Does immune challenge affect torpor duration?

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