Circulatory Changes During Process of Arousal in the Hibernating Hamster

Chatfield, Paul O.; Lyman, Charles P.

doi:10.1152/ajplegacy.1950.163.3.566

Cited by 59 publications

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“…Total peripheral vascular resistance rises during hibernation in ground squirrels and hedgehogs, in part due to modest peripheral vasoconstriction, but primarily due to the large increase in blood viscosity at low body temperatures (Johansen, 1967; Kirkebö, 1968a; Kirkebö, 1968b;Maclean, 1981). Even though systemic arterial blood pressure overall decreases during hibernation compared with the active state (Chatfield and Lyman, 1950; Johansen, 1967; Kirkebö, 1968a), the slower rate of cardiac contraction combined with increased peripheral vascular resistance results in a slower diastolic flow movement down the arterial system. The windkessel effect promotes blood flow along vessels but with the prolonged diastole of slow heart rates, diastolic flow movement down the system does not proceed rapidly.…”

mentioning

confidence: 99%

Increase in cardiac myosin heavy-chain (MyHC) alpha protein isoform in hibernating ground squirrels, with echocardiographic visualization of ventricular wall hypertrophy and prolonged contraction.

Nelson

Rourke

2013

Journal of Experimental Biology

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SUMMARYDeep hibernators such as golden-mantled ground squirrels (Callospermophilus lateralis) have multiple challenges to cardiac function during low temperature torpor and subsequent arousals. As heart rates fall from over 300 beats min -1 to less than 10, chamber dilation and reduced cardiac output could lead to congestive myopathy. We performed echocardiography on a cohort of individuals prior to and after several months of hibernation. The left ventricular chamber exhibited eccentric and concentric hypertrophy during hibernation and thus calculated ventricular mass was ~30% greater. Ventricular ejection fraction was mildly reduced during hibernation but stroke volumes were greater due to the eccentric hypertrophy and dramatically increased diastolic filling volumes. Globally, the systolic phase in hibernation was ~9.5 times longer, and the diastolic phase was 28× longer. Left atrial ejection generally was not observed during hibernation. Atrial ejection returned weakly during early arousal. Strain echocardiography assessed the velocity and total movement distance of contraction and relaxation for regional ventricular segments in active and early arousal states. Myocardial systolic strain during early arousal was significantly greater than the active state, indicating greater total contractile movement. This mirrored the increased ventricular ejection fraction noted with early arousal. However, strain rates were slower during early arousal than during the active period, particularly systolic strain, which was 33% of active, compared with the rate of diastolic strain, which was 67% of active. As heart rate rose during the arousal period, myocardial velocities and strain rates also increased; this was matched closely by cardiac output. Curiously, though heart rates were only 26% of active heart rates during early arousal, the cardiac output was nearly 40% of the active state, suggesting an efficient pumping system. We further analyzed proportions of cardiac myosin heavy-chain (MyHC) isoforms in a separate cohort of squirrels over 5 months, including time points before hibernation, during hibernation and just prior to emergence. Hibernating individuals were maintained in both a 4°C cold room and a 20°C warm room. Measured by SDS-PAGE, relative percentages of cardiac MyHC alpha were increased during hibernation, at both hibernacula temperatures. A potential increase in contractile speed, and power, from more abundant MyHC alpha may aid force generation at low temperature and at low heart rates. Unlike many models of cardiomyopathies where the alpha isoform is replaced by the beta isoform in order to reduce oxygen consumption, ground squirrels demonstrate a potential cardioprotective mechanism to maintain cardiac output during torpor. Received 25 March 2013; Accepted 4 September 2013Key words: hibernation, MyHC, echocardiogram, atrial contraction, cardiac function. Echocardiogram and myosin of hibernatorsThe myosin heavy-chain isoforms (MyHC) are crucial determinants of contractile performance in cardiac muscle t...

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confidence: 99%

Increase in cardiac myosin heavy-chain (MyHC) alpha protein isoform in hibernating ground squirrels, with echocardiographic visualization of ventricular wall hypertrophy and prolonged contraction.

Nelson

Rourke

2013

Journal of Experimental Biology

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“…However in all instances, once animals become committed to the arousal process, heart rate, ventilation rate and metabolism increase rapidly and simultaneously (Chatfield & Lyman, 1950;Eliassen, 1960;Kirkebo, 1968) prior to any changes in body temperature ( Fig. 1) (Strumwasser, 1959).…”

Section: Vagal Control Of Cardiorespiratory Function During Arousal Fmentioning

confidence: 99%

Physiological Society Symposium – Vagal Control: From Axolotl to Man

Milsom

Zimmer

Harris

2001

Experimental Physiology

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“…Food intake and gut function are suspended and renal function is reduced. Arousal is rapid and starts with an increase in heart rate, respiration and oxygen consumption, followed by a rise in body temperature and regulation of vasodilatation which leads to an increase in blood pressure and blood flow (Chatfield & Lyman, 1950 ;Lyman, 1965 ;Lyman & O'Brien, 1988).…”

Section: mentioning

confidence: 99%

Electron‐immunocytochemical studies of perivascular nerves of mesenteric and renal arteries of golden hamsters during and after arousal from hibernation

Saitongdee¹,

Milner²,

Loesch³

et al. 1999

Journal of Anatomy

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Electron immunocytochemistry was used to examine perivascular nerves of hamster mesenteric and renal arteries during hibernation and 2 h after arousal from hibernation. Vessels from cold-exposed but nonhibernating, and normothermic control hamsters were also examined. During hibernation the percentage of axon profiles in mesenteric and renal arteries that were immunopositive for markers of sympathetic nerves, tyrosine hydroxylase (TH) and neuropeptide Y (NPY), were increased 2-3 fold compared with normothermic and cold control animals. This increase was reduced markedly only 2 h after arousal from hibernation. The small percentage of nitric oxide synthase-1-positive axon profiles found in mesenteric (but not renal) arteries was also increased during hibernation and returned towards control values after arousal. In contrast, the percentage of perivascular axons immunostaining for vasoactive intestinal polypeptide (VIP), a marker for parasympathetic nerves, was reduced in mesenteric arteries during hibernation. There was no labelling of perivascular nerves for substance P in either mesenteric or renal arteries. It is suggested that the increase in percentage of TH-and NPY-immunostained perivascular nerves may account for the increased vasoconstriction associated with high vascular resistance that is known to occur during hibernation. The reduction in the percentage of axons positive for VIP in hibernating animals would contribute to this mechanism since this neuropeptide is a vasodilator.Key words : Tyrosine hydroxylase ; neuropeptide Y ; vasoactive intestinal peptide ; substance P ; nitric oxide synthase. In mammals, hibernation represents an effective strategy for surviving periods of harsh ecological conditions, a scarcity of food and adverse low temperature weather conditions. The physiological change from the normothermic condition to the state of hibernation is characterised by a decrease in metabolic rate and body temperature to below 10 mC, a reduced heart rate to below 10 beats\min, reduced respiratory rate of less than 3 breaths\min, a decrease in systemic blood pressure to about 50 mmHg, but an increase in peripheral vascular resistance (Lyman,

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Circulatory Changes During Process of Arousal in the Hibernating Hamster

Cited by 59 publications

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Increase in cardiac myosin heavy-chain (MyHC) alpha protein isoform in hibernating ground squirrels, with echocardiographic visualization of ventricular wall hypertrophy and prolonged contraction.

Increase in cardiac myosin heavy-chain (MyHC) alpha protein isoform in hibernating ground squirrels, with echocardiographic visualization of ventricular wall hypertrophy and prolonged contraction.

Physiological Society Symposium – Vagal Control: From Axolotl to Man

Electron‐immunocytochemical studies of perivascular nerves of mesenteric and renal arteries of golden hamsters during and after arousal from hibernation

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