Mammals exposed to cold weather must cope with it in some way. Some small mammals such as mice and voles do not enter hibernation or torpor. However, maintaining body temperature is a core homeostatic function. The left ventricles in winter mice and voles enlarge, and this is thought to occur because the heart must pump warmth and nutrients into the rest of the body to compensate for cold environmental temperatures. An alternative hypothesis is that the growth may be caused by the oxidative stress that the mice experience when in cold conditions. This enlargement is called cardiac hypertrophy. This growth is caused by physiological, healthy factors such as exercise and pregnancy or by pathological, disease-state factors such as obesity and hypertension. Our lab is establishing cold-exposure as a model system for studying cardiac hypertrophy, and one major knowledge gap is how well mice maintain internal body temperatures when exposed to ecologically relevant temperatures. A temperature PIT tag was implanted intraperitoneally into 8, male 10-week-old mice. The mice were given 3 days of recovery. Half of the mice were ramped down to 4℃ and the other half were kept in warm conditions (25℃) across 2 weeks. The body temperature was recorded every minute for 2 weeks. We found that mice are able to maintain their internal body temperatures when challenged by cold environmental temperatures, and that their overall circadian temperature rhythm is more constrained than in control conditions. In control conditions, the highest temperature recorded was 38.5℃ and the lowest was 30.8℃. In cold conditions, the highest temperature was 39.2℃ and the lowest was 31.8℃.
Authors: Jess Guilfoyle, McKenna Burns, Paul Schaeffer
Advisor(s): Paul Schaeffer, Biology
McKenna Burns, Biology
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