QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online August 4, 2005
Journal of Experimental Biology 208, 3159-3167 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01703

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Schaeffer, P. J. Articles by Lindstedt, S. L. Search for Related Content PubMed PubMed Citation Articles by Schaeffer, P. J. Articles by Lindstedt, S. L. Social Bookmarking                         What's this?

Cost of transport is increased after cold exposure in Monodelphis domestica: training for inefficiency

Paul J. Schaeffer^1,2,*, Jason J. Villarin^1,, David J. Pierotti¹, Daniel P. Kelly^2,3 and Stan L. Lindstedt¹

¹ Department of Biological Sciences, Physiology and Functional Morphology Group, Northern Arizona University, Flagstaff, AZ 86011, USA
² Center for Cardiovascular Research and Department of Medicine, Washington University School of Medicine, St Louis, MO 63110, USA
³ Department of Molecular Biology and Pharmacology, and Department of Pediatrics, Washington University School of Medicine, St Louis, MO 63110, USA

View larger version (16K): [in a new window]   Fig. 1. Cost of transport during locomotion. Using an open flow metabolic system, O2 was measured as a function of running speed on a motorized treadmill. The cold-acclimated animals had significantly higher O2 utilization as a function of speed such that on average 15% more oxygen was consumed while running at the same speed as thermoneutral controls. Values are means ± S.E.M. at each speed. CS, cold, sedentary; CT, cold, trained; TnS, thermoneutral, sedentary; TnT, thermoneutral, trained.

View larger version (12K): [in a new window]   Fig. 2. Kinetics of single twitch contractions. (A) Time to peak tension per gram of force produced (TPTg) for single twitches of the semitendinosus muscle by the four experimental groups (as in Table 1) was significantly increased by cold acclimation but not by exercise training. There is a trend for increased time required to generate force with either the TnT or CS treatment group, but only those animals subjected to both treatments (CT) showed a statistically significant slowing of twitch speed. (B) Half relaxation time per gram of force produced (RTg) for single twitches by semitendinosus muscles of the four experimental groups. The RTg was significantly longer in cold-acclimated but not by exercise-trained animals. Both cold groups had a longer relaxation rate; however, post-hoc pairwise comparison showed this effect was only statistically significant in the CT group. Values are means ± S.E.M. and different superscripted letters indicate significant pairwise differences between groups. CS, cold, sedentary; CT, cold, trained; TnS, thermoneutral, sedentary; TnT, thermoneutral, trained.

View larger version (8K): [in a new window]   Fig. 3. Maximal shortening velocity. Maximal muscle shortening velocity (vmax, muscle lengths ML s–1) was significantly lower following both cold acclimation and exercise training. The extent of the effect tended to increase more with cold acclimation than with exercise training. Values are means ± S.E.M. and different superscripted letters indicate significant pairwise differences between groups. CS, cold, sedentary; CT, cold, trained; TnS, thermoneutral, sedentary; TnT, thermoneutral, trained.

View larger version (9K): [in a new window]   Fig. 4. Fatigue index. The fatigue index is a measure of the percent of force production capacity remaining after a fatiguing series of contractions, and is thus a measure of muscle endurance. The fatigue index of semitendinosus muscles from the four groups was significantly increased only by cold acclimation, and the CT group showed the highest resistance to fatigue. Values are means ± S.E.M. and different superscripted letters indicate significant pairwise differences between groups. CS, cold, sedentary; CT, cold, trained; TnS, thermoneutral, sedentary; TnT, thermoneutral, trained.

View larger version (63K): [in a new window]   Fig. 5. Monodelphis domestica UCP-3 expression. The expression of the mRNA encoding a putative homolog of uncoupling protein 3 (Md-UCP3) was induced in hindlimb skeletal muscle of cold-acclimated animals, as detected by northern blot. Intensity of 28S RNA, stained with Ethidium Bromide, is included as a loading control.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

Twitter