Burrowing star-nosed moles (Condylura cristata) are not hypoxia tolerant

ABSTRACT Star-nosed moles (Condylura cristata) have an impressive diving performance and burrowing lifestyle, yet no ventilatory data are available for this or any other talpid mole species. We predicted that, like many other semi-aquatic and fossorial small mammals, star-nosed moles would exhibit: (i) a blunted (i.e. delayed or reduced) hypoxic ventilatory response, (ii) a reduced metabolic rate and (iii) a lowered body temperature (Tb) in hypoxia. We thus non-invasively measured these variables from wild-caught star-nosed moles exposed to normoxia (21% O2) or acute graded hypoxia (21–6% O2). Surprisingly, star-nosed moles did not exhibit a blunted HVR or decreased Tb in hypoxia, and only manifested a significant, albeit small (<8%), depression of metabolic rate at 6% O2 relative to normoxic controls. Unlike small rodents inhabiting similar niches, star-nosed moles are thus intolerant to hypoxia, which may reflect an evolutionary trade-off favouring the extreme sensory biology of this unusual insectivore.

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Increased HVR in pregnancy: relationship to hormonal and metabolic changes

Journal of Applied Physiology ◽

10.1152/jappl.1987.62.1.158 ◽

1987 ◽

Vol 62 (1) ◽

pp. 158-163 ◽

Cited By ~ 79

Author(s):

L. G. Moore ◽

R. E. McCullough ◽

J. V. Weil

Keyword(s):

Metabolic Rate ◽

Shape Parameter ◽

Ventilatory Response ◽

Co2 Production ◽

Hormonal Changes ◽

Hypoxic Ventilatory Response ◽

Additional Increase ◽

Arterial Ph ◽

Partial Pressure Of Co2 ◽

Low Altitude

In prior studies at high altitude, we have found that pregnancy increases maternal hypoxic ventilatory response (HVR) but the factors responsible are unknown. Changes in metabolic rate and hormones that occur during pregnancy have previously been shown to influence HVR. We therefore sought to determine the contribution of metabolic rate and hormonal changes to the pregnancy-associated rise in HVR. Pregnancy increased HVR in each of 20 normal, low-altitude (1,600 m) residents. As measured by the shape parameter A, HVR at week 36 was 237 +/- 26 (SE) or twofold higher than the 124 +/- 13 value measured 3 mo postpartum (P less than 0.01) despite the presence of the potentially depressant effects of hypocapnia [change in alveolar partial pressure of CO2 (delta PACO2) = -4 +/- 1 mmHg] and alkalosis [change in arterial pH (delta pHa) = 0.02 +/- 0.01 U] during pregnancy. Sixty percent of the increase in HVR values had occurred by week 20 of gestation at which time O2 consumption (VO2) and CO2 production (VCO2) were unchanged relative to values measured postpartum. The remaining 40% rise in HVR paralleled increases in VO2 and VCO2, and further elevation in VO2 and VCO2 with moderate exercise produced an additional increase in HVR. Serum estradiol and progesterone levels increased with pregnancy, but levels did not correlate with HVR. The women reporting the greatest symptoms of dyspnea had higher HVR A values at week 36 than the least dyspneic women (285 +/- 28 vs. 178 +/- 34, respectively, P less than 0.05). We concluded that factors intrinsic to pregnancy in combination with increased metabolic rate raised HVR twofold with pregnancy and may have contributed to the often-reported symptoms of dyspnea in pregnant women.

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Hypoxic metabolic response of the golden-mantled ground squirrel

Journal of Applied Physiology ◽

10.1152/jappl.2001.91.2.603 ◽

2001 ◽

Vol 91 (2) ◽

pp. 603-612 ◽

Cited By ~ 52

Author(s):

Renata C. H. Barros ◽

Mary E. Zimmer ◽

Luiz G. S. Branco ◽

William K. Milsom

Keyword(s):

Heart Rate ◽

Body Temperature ◽

Metabolic Rate ◽

Small Mammals ◽

Ground Squirrel ◽

Metabolic Response ◽

Ground Squirrels ◽

Metabolic Rates ◽

The Relationship ◽

Primary Strategy

We examined the magnitude of the hypoxic metabolic response in golden-mantled ground squirrels to determine whether the shift in thermoregulatory set point (Tset) and subsequent fall in body temperature (Tb) and metabolic rate observed in small mammals were greater in a species that routinely experiences hypoxic burrows and hibernates. We measured the effects of changing ambient temperature (Ta; 6–29°C) on metabolism (O2 consumption and CO2 production), Tb, ventilation, and heart rate in normoxia and hypoxia (7% O2). The magnitude of the hypoxia-induced falls in Tb and metabolism of the squirrels was larger than that of other rodents. Metabolic rate was not simply suppressed but was regulated to assist the initial fall in Tb and then acted to slow this fall and stabilize Tb at a new, lower level. When Ta was reduced during 7% O2, animals were able to maintain or elevate their metabolic rates, suggesting that O2 was not limiting. The slope of the relationship between temperature-corrected O2 consumption and Taextrapolated to a Tset in hypoxia equals the actual Tb. The data suggest that Tset was proportionately related to Ta in hypoxia and that there was a shift from increasing ventilation to increasing O2extraction as the primary strategy employed to meet increasing metabolic demands under hypoxia. The animals were neither hypothermic nor hypometabolic, as Tb and metabolic rate appeared to be tightly regulated at new but lower levels as a result of a coordinated hypoxic metabolic response.

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Postnatal development of metabolic rate during normoxia and acute hypoxia in rats: implication for a sensitive period

Journal of Applied Physiology ◽

10.1152/japplphysiol.90949.2008 ◽

2009 ◽

Vol 106 (4) ◽

pp. 1212-1222 ◽

Cited By ~ 31

Author(s):

Qiuli Liu ◽

Charles Fehring ◽

Timothy F. Lowry ◽

Margaret T. T. Wong-Riley

Keyword(s):

Metabolic Rate ◽

Respiratory Quotient ◽

Critical Period ◽

Ventilatory Response ◽

Minute Ventilation ◽

Acute Hypoxia ◽

Sensitive Period ◽

Metabolic Rates ◽

Hypoxic Ventilatory Response ◽

Neurochemical Changes

Previously, we reported that the hypoxic ventilatory response (HVR) in rats was weakest at postnatal day (P) P13, concomitant with neurochemical changes in respiratory nuclei. A major determinant of minute ventilation (V̇e) is reportedly the metabolic rate [O2consumption (V̇o2) and CO2production (V̇co2)]. The present study aimed at testing our hypothesis that daily metabolic rates changed in parallel with ventilation during development and that a weak HVR at P13 was attributable mainly to an inadequate metabolic rate in hypoxia. Ventilation and metabolic rates were monitored daily in P0–P21 rats. We found that 1) ventilation and metabolic rates were not always correlated, and V̇e/V̇o2and V̇e/V̇co2ratios were not constant during development; 2) metabolic rate and V̇e/V̇o2and V̇e/V̇co2ratios at P0–P1 were significantly different from the remaining first postnatal week in normoxia and hypoxia; 3) at P13, metabolic rates and V̇e/V̇o2and V̇e/V̇co2ratios abruptly increased in normoxia and were compromised in acute hypoxia, unlike more stable trends during the remaining second and third postnatal weeks; and 4) the respiratory quotient (V̇co2/V̇o2) was quite stable in normoxia and fluctuated slightly in hypoxia from P0 to P21. Thus our data revealed heretofore unsuspected metabolic adjustments at P0–P1 and P13. At P0–P1, ventilation and metabolic rates were uncorrelated, whereas at P13, they were closely correlated under normoxia and hypoxia. The findings further strengthened the existence of a critical period of respiratory development around P13, when multiple physiological and neurochemical adjustments occur simultaneously.

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Extended Lowered Body Temperature Increases Effective CS-US Interval in Conditioned Taste Aversion for Adult Rats

PsycEXTRA Dataset ◽

10.1037/e413792005-070 ◽

2000 ◽

Cited By ~ 1

Author(s):

Mark Goodhart ◽

James R. Misanin ◽

Charles R. Hinderliter

Keyword(s):

Body Temperature ◽

Taste Aversion ◽

Conditioned Taste Aversion ◽

Adult Rats ◽

Lowered Body

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Torpor and hibernation

10.1093/oso/9780199551668.003.0011 ◽

2017 ◽

Author(s):

Andrew Clarke

Keyword(s):

Body Temperature ◽

Small Mammals ◽

Energy Input ◽

The Arctic ◽

Arid Areas ◽

Daily Torpor ◽

High Latitudes ◽

Small Species ◽

Universal Feature ◽

Deep Hibernation

A diurnal (circadian) rhythm in body temperature is a widespread, and possibly universal, feature of endotherms. Some mammals and birds down-regulate their metabolic rate significantly by night, allowing their body temperature to drop sufficiently that they become inactive and enter torpor. Both the minimum temperature achieved and the duration of torpor are highly variable. Daily torpor is principally a response to reduced energy intake, and a drop in ambient temperature. Hibernation is essentially an extreme form of torpor. Small mammals hibernating at high latitudes have regular arousals during which they urinate and may feed. Bears hibernate with relatively high body temperature, and do not undergo arousal. Only one bird, the poorwill, is known to hibernate. Rewarming during arousal may be fuelled exclusively by metabolism (for example in small mammals in the Arctic) or with significant energy input from basking (for example in subtropical arid areas). The capacity for torpor appears to be an ancestral character in both mammals and birds, possibly related to the origin of endothermy in small species subject to marked diurnal and/or seasonal variation in body temperature. Both deep hibernation and strict endothermy are probably derived characteristics.

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