Ventilatory responses of the ground squirrel, Spermophilus tridecemlineatus, to various levels of hypoxia

Davies, D. G.; Schadt, James C.

doi:10.1016/0300-9629(89)90162-x

Cited by 13 publications

(8 citation statements)

References 7 publications

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“…Thus, it is not clear whether it is the capacity for heterothermy or the chronic hypoxia of a fossorial life that results in hypoxia tolerance. A number of semi-fossorial, as well as nonfossorial, heterotherms exhibit tolerance to hypoxia comparable with fossorial species (Hiestand et al, 1950; Biörck et al, 1956; Burlington et al, 1971;Davies and Schadt, 1989;Mortola, 1991;Walsh et al, 1996; Boggs et al, 1999;Frappell et al, 2002). Such tolerance does not necessarily depend on exposure to chronic hypoxia, as it is also expressed in adults not exposed to hypoxia during development (Mortola, 1991).…”

Section: Hypoxia Tolerance As An Adaptation To Heterothermy Per Sementioning

confidence: 99%

Hypoxia tolerance in mammalian heterotherms

Drew

Harris

LaManna

et al. 2004

Journal of Experimental Biology

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Heterothermic mammals tolerate severe hypoxia, as well as a variety of central nervous system insults, better than homeothermic mammals. Tolerance to hypoxia may stem from adaptations associated with the ability to survive hibernation and periodic arousal thermogenesis. Here, we review evidence and mechanisms of hypoxia tolerance during hibernation, euthermy and arousal in heterothermic mammals and consider potential mechanisms for regenerative-like processes, such as synaptogenesis, observed within hours of hypoxic stress associated with arousal thermogenesis. 3156hypothermia and metabolic suppression in ground squirrels as it does in hypoxia-tolerant turtles and fish (Bullard et al., 1960). Additional adaptations in heterothermic mammals may synergize with hypothermia and metabolic suppression to attenuate the cytotoxic cascade. Because many of these protective mechanisms such as hypothermia, metabolic suppression, immunosuppression/leukocytopenia and increased antioxidant defenses differ between hibernating (torpid) and euthermic animals, we will discuss hypoxia tolerance in hibernating animals separately from hypoxia tolerance in euthermic animals (Fig.·1; reviewed in Drew et al., 2001).Hypoxia tolerance in the hibernating state: evidence and mechanisms Reports dating back to the early 1800s describe hypoxia tolerance in the hibernating state in bats, marmots and ground squirrels and show that tolerance displayed during hibernation exceeds tolerance observed during euthermy (Spallanzani et al., 1803; Carlisle, 1805; cited in Biörck et al., 1956; reviewed in Bullard et al., 1960). Biörck et al. (1956) confirmed these initial observations and reported that hibernating hedgehogs (Erinaceus europaeus) survive 50-120·min of 100% N2, in most cases without apparent damage.Interestingly, many hibernating species in steady-state torpor are not hypoxic despite 10-fold or greater decreases in respiratory rates. During torpor, Arctic ground squirrels (Spermophilus parryii), as well as other species of ground squirrel, are well oxygenated with normal to above normal arterial oxygen pressures (Frerichs et al., 1994; Y. L. Ma, X. Zhu, P. M. Rivera, O. Toien, B. M. Barnes, J. C. LaManna, M. A. Smith and K. L. Drew, manuscript submitted for publication). By contrast, other heterothermic species, such as golden-mantled ground squirrels (Spermophilus lateralis) and hedgehogs (E. europaeus), may become hypoxic during torpor owing to long periods of apnea. These species often breathe intermittently during hibernation, waiting up to 30·min or longer between breaths. In hedgehogs, arterial oxygen partial pressure (PaO∑), sampled from chronic aorta cannula, is higher in torpor than in the active state (120 vs 105·mmHg; 160 vs 14.0·kPa) but K. L. Drew and others Release of neurotransmitters, including the excitotoxin glutamate, and activation of NMDA and AMPA receptors contribute to the flood of Ca 2+ from extra-and intracellular stores, which leads to calcium overload (4). Activated microglia release inflammatory cytokines and ni...

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Section: Hypoxia Tolerance As An Adaptation To Heterothermy Per Sementioning

confidence: 99%

Hypoxia tolerance in mammalian heterotherms

Drew

Harris

LaManna

et al. 2004

Journal of Experimental Biology

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“…The naked mole rat has an extremely low basal metabolic rate for a eutherian mammal of its size with previously reported values within its thermoneutral zone (28–34 °C) ranging between 0.66 mL/g/h, 0.75 mL/g/h, and 1.0 mL/g/h (Buffenstein and Yahav, 1991; Goldmans et al, 1999; McNab, 1966). Furthermore, this species has a lower resting body temperature (33 °C) than most normothermic mammals (Davies and Schadt, 1989). Interestingly, the naked mole rat can regulate its metabolism to maintain the preferred Tb when Ta falls below its ideal range (Buffenstein and Woodley, 2001; Buffenstein and Yahav, 1991).…”

Section: Introductionmentioning

confidence: 99%

Effect of hypoxia on metabolic rate, core body temperature, and c‐fos expression in the naked mole rat

Nathaniel

Otukonyong

Abdellatif

et al. 2012

Intl J of Devlp Neuroscience

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Recent investigations of hypoxia physiology in the naked mole rat have opened up an interesting line of research into the basic physiological and genomic alterations that accompany hypoxia survival. The extent to which such findings connect the effect of hypoxia to metabolic rate (O₂ consumption), core body temperature (Tb), and transcripts encoding the immediate early gene product (such as c-fos) under a constant ambient temperature (Ta) is not well known. We investigated this issue in the current study. Our first sets of experiments measured Tb and metabolic rates during exposure of naked mole rats to hypoxia over a constant Ta. Hypoxia significantly decreased metabolic rates in the naked mole rat. Although core Tb also decreased during hypoxia, the effect of hypoxia in suppressing core Tb was not significant. The second series of experiments revealed that c-fos protein and mRNA expression in the hippocampus neurons (CA1) increased in naked mole rats that were repeatedly exposed to 3% O₂ for 60 min per day for 5 days when compared to normoxia. Our findings provide evidence for the up-regulation of c-fos and suppression of metabolic rate in hypoxia tolerating naked mole rats under constant ambient temperature. Metabolic suppression and c-fos upregulation constitute part of the physiological complex associated with adaptation to hypoxia.

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“…25 In addition, a subset of heterotherms, including AGS, are fossorial, and fossorial animals display hypoxia tolerance. 26 However, it has yet to be shown whether fossorial animals in general tolerate ischemia as well as hypoxia. Evidence from other hypoxic-tolerant species suggests that some of the adaptations are similar but perhaps not sufficient to promote ischemic tolerance.…”

Section: Dave Et Al Euthermic Ags Brain Is Resistant To Cardiac Arrestmentioning

confidence: 99%

The Arctic Ground Squirrel Brain Is Resistant to Injury From Cardiac Arrest During Euthermia

Dave

Prado

Raval

et al. 2006

Stroke

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Background and Purpose-Hetereothermic mammals tolerate hypoxia during euthermy and torpor, and evidence suggests this tolerance may extend beyond hypoxia to cerebral ischemia. During hibernation, CA1 hippocampal neurons endure extreme fluctuations in cerebral blood flow during transitions into and out of torpor as well as reductions in cerebral blood flow during torpor. In vitro studies likewise show evidence of ischemia tolerance in hippocampal slices harvested from euthermic ground squirrels; however, no studies have investigated tolerance in a clinically relevant model of in vivo global cerebral ischemia. The purpose of the present study was to test the hypothesis that the euthermic Arctic ground squirrel (AGS; Spermophillus parryii) is resistant to injury from asphyxial cardiac arrest (CA). Methods-Estrous-matched female rats were used as a positive control. Female euthermic AGS and rats were subjected to 8-minute CA. At the end of 7 days of reperfusion, AGS and rats were fixed for histopathological assessment. Results-In rats subjected to CA, the number of ischemic neurons was significantly higher (PϽ0.001) compared with control rats in hippocampus and striatum. Cortex was mildly injured. Surprisingly, neuronal counts in AGS were not significantly different in CA and control groups in these brain regions. Conclusion-These data demonstrate that AGS are remarkably tolerant to global cerebral ischemia during euthermia. A better understanding of the mechanisms by which AGS tolerate severe reductions in blood flow during euthermia may provide novel neuroprotective strategies that may translate into significant improvements in human patient outcomes after CA. (Stroke. 2006;37:1261-1265.)

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Ventilatory responses of the ground squirrel, Spermophilus tridecemlineatus, to various levels of hypoxia

Cited by 13 publications

References 7 publications

Hypoxia tolerance in mammalian heterotherms

Hypoxia tolerance in mammalian heterotherms

Effect of hypoxia on metabolic rate, core body temperature, and c‐fos expression in the naked mole rat

The Arctic Ground Squirrel Brain Is Resistant to Injury From Cardiac Arrest During Euthermia

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