Brain cooling and respiratory heat exchange in camels during rest and exercise

Schroter, R. C.; Robertshaw, David; Filali, R. Z.

doi:10.1016/0034-5687(89)90145-x

Cited by 17 publications

(9 citation statements)

References 7 publications

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“…Compared with euhydration, dehydrated goats and sheep increased selective brain cooling with no alteration in the threshold body temperature at which selective brain cooling was implemented. When animals were not heat stressed and were able to lose heat through non-evaporative avenues, two restrained camels at rest showed no obvious difference in brain and blood temperatures between hydrated and dehydrated states (Schroter et al, 1989). We conclude that the Arabian oryx uses selective brain cooling to facilitate homeostasis in hot and dry environments.…”

Section: Discussionmentioning

confidence: 77%

Selective brain cooling in Arabian oryx (Oryx leucoryx): a physiological mechanism for coping with aridity?

Hetem

Strauss

Fick

et al. 2012

Journal of Experimental Biology

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SUMMARYSelective brain cooling is a thermoregulatory effector proposed to conserve body water and, as such, may help artiodactyls cope with aridity. We measured brain and carotid blood temperature, using implanted data loggers, in five Arabian oryx (Oryx leucoryx) in the desert of Saudi Arabia. On average, brain temperature was 0.24±0.05°C lower than carotid blood temperature for four oryx in April. Selective brain cooling was enhanced in our Arabian oryx compared with another species from the same genus (gemsbok Oryx gazella gazella) exposed to similar ambient temperatures but less aridity. Arabian oryx displayed a lower threshold (37.8±0.1°C vs 39.8±0.4°C), a higher frequency (87±6% vs 15±15%) and a higher maximum magnitude (1.2±0.2°C vs 0.5±0.3°C) of selective brain cooling than did gemsbok. The dominant male oryx displayed less selective brain cooling than did any of the other oryx, but selective brain cooling was enhanced in this oryx as conditions became hotter and drier. Enhanced selective brain cooling in Arabian oryx supports the hypothesis that selective brain cooling would bestow survival advantages for artiodactyl species inhabiting hot hyper-arid environments.

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Section: Discussionmentioning

confidence: 77%

Selective brain cooling in Arabian oryx (Oryx leucoryx): a physiological mechanism for coping with aridity?

Hetem

Strauss

Fick

et al. 2012

Journal of Experimental Biology

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“…Respiratory heat exchange occurs in many mammalian species that primarily employ nasal breathing (42). In large mammals such as the camel (41) and the horse (24,34), ventilation during heat stress serves to maintain brain temperature as much as several degrees Celsius below core body temperature (34,49). Although horses employ a robust sweating response (rates of Ͼ30 l/h) that works in concert with the respiratory system to dissipate heat during exercise (24), these responses are not adequate to prevent heat storage during exercise, in part due to a relatively low surface area-to-body mass ratio in the racing horse.…”

Section: Discussionmentioning

confidence: 99%

Ventilatory dynamics and control of blood gases after maximal exercise in the Thoroughbred horse

Padilla¹,

McDonough²,

Kindig³

et al. 2004

Journal of Applied Physiology

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Despite enormous rates of minute ventilation (Ve) in the galloping Thoroughbred (TB) horse, the energetic demands of exercise conspire to raise arterial Pco(2) (i.e., induce hypercapnia). If locomotory-respiratory coupling (LRC) is an obligatory facilitator of high Ve in the horse such as those found during galloping (Bramble and Carrier. Science 219: 251-256, 1983), Ve should drop precipitously when LRC ceases at the galloptrot transition, thus exacerbating the hypercapnia. TB horses (n = 5) were run to volitional fatigue on a motor-driven treadmill (1 m/s increments; 14-15 m/s) to study the dynamic control of breath-by-breath Ve, O(2) uptake, and CO(2) output at the transition from maximal exercise to active recovery (i.e., trotting at 3 m/s for 800 m). At the transition from the gallop to the trot, Ve did not drop instantaneously. Rather, Ve remained at the peak exercising levels (1,391 +/- 88 l/min) for approximately 13 s via the combination of an increased tidal volume (12.6 +/- 1.2 liters at gallop; 13.9 +/- 1.6 liters over 13 s of trotting recovery; P < 0.05) and a reduced breathing frequency [113.8 +/- 5.2 breaths/min (at gallop); 97.7 +/- 5.9 breaths/min over 13 s of trotting recovery (P < 0.05)]. Subsequently, Ve declined in a biphasic fashion with a slower mean response time (85.4 +/- 9.0 s) than that of the monoexponential decline of CO(2) output (39.9 +/- 4.7 s; P < 0.05), which rapidly reversed the postexercise arterial hypercapnia (arterial Pco(2) at gallop: 52.8 +/- 3.2 Torr; at 2 min of recovery: 25.0 +/- 1.4 Torr; P < 0.05). We conclude that LRC is not a prerequisite for achievement of Ve commensurate with maximal exercise or the pronounced hyperventilation during recovery.

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“…baileyi ), kit fox ( V. macrotis ), and grizzly bear ( U. arctos ), which they attribute to climate‐mediated demands for respiratory heat and moisture exchange (see also Van Valkenburgh, Theodor, Friscia, Pollack, & Rowe, ; Yokley, ). Further, numerous studies (MacMillen & Hinds, ; Owerkowicz, Musinsky, Middleton, & Crompton, ; Schmidt‐Nielsen, Hainsworth, & Murrish, ; Schmidt‐Nielsen, Schroter, & Shkolnik, ; Schroter et al, ; Schroter, Robertshaw, & Filali, ; Walsberg, ) have argued that expansion of the maxilloturbinate facilitates the recapture of moisture during expiration among mammals inhabiting arid environments. Similarly, the retrieval of moisture during expiration has also been posited as an important factor in human nasal evolution in order to reduce the “respiratory cost” of breathing relatively dry air (Carey & Steegmann, ; Franciscus & Long, ; Franciscus & Trinkaus, ).…”

Section: Introductionmentioning

confidence: 99%

Climatic adaptation in human inferior nasal turbinate morphology: Evidence from Arctic and equatorial populations

Marks

Maddux

Butaric

et al. 2019

American J Phys Anthropol

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Objectives: The nasal turbinates directly influence the overall size, shape, and surface area of the nasal passages, and thus contribute to intranasal heat and moisture exchange. However, unlike the encapsulating walls of the nasal cavity, ecogeographic variation in nasal turbinate morphology among humans has not yet been established.Here we investigate variation in inferior nasal turbinate morphology in two populations from climatically extreme environments.Materials and methods: Twenty-three linear measurements of the inferior turbinate, nasal cavity walls, and airway passages were collected from CT scans of indigenous modern human crania from Equatorial Africa (n = 35) and the Arctic Circle (n = 35).MANOVA and ANCOVA were employed to test for predicted regional and sex differences in morphology between the samples.Results: Significant morphological differences were identified between the two regional samples, with no evidence of significant sexual dimorphism or region-sex interaction effect. Individuals from the Arctic Circle possessed superoinferiorly and mediolaterally larger inferior turbinates compared to Equatorial Africans. In conjunction with the surrounding nasal cavity walls, these differences in turbinate morphology produced airway dimensions that were both consistent with functional expectations and more regionally distinct than either skeletal component independently. Conclusion:This study documents the existence of ecogeographic variation in human nasal turbinate morphology reflecting climate-mediated evolutionary demands on intranasal heat and moisture exchange. Humans adapted to cold-dry environments exhibit turbinate morphologies that enhance contact between respired air and nasal mucosa to facilitate respiratory air conditioning. Conversely, humans adapted to hothumid environments exhibit turbinate morphologies that minimize air-to-mucosa contact, likely to minimize airflow resistance and/or facilitate expiratory heat-shedding. K E Y W O R D S conchae, human variation, nose, respiratory tract, thermoregulation

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Brain cooling and respiratory heat exchange in camels during rest and exercise

Cited by 17 publications

References 7 publications

Selective brain cooling in Arabian oryx (Oryx leucoryx): a physiological mechanism for coping with aridity?

Selective brain cooling in Arabian oryx (Oryx leucoryx): a physiological mechanism for coping with aridity?

Ventilatory dynamics and control of blood gases after maximal exercise in the Thoroughbred horse

Climatic adaptation in human inferior nasal turbinate morphology: Evidence from Arctic and equatorial populations

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