Physiology Commons^™

In Vivo Potentiation Of Muscle Torque Is Enhanced In Female Mice Through Estradiol-Estrogen Receptor Signaling, Gengyun Le, Cory W. Baumann, Dawn A. Lowe, Gordon L. Warren

Biology Faculty Publications

Estradiol affects several properties of skeletal muscle in females including strength. Here, we developed an approach to measure in vivo posttetanic twitch potentiation (PTP) of the anterior crural muscles of anesthetized mice and tested the hypothesis that 17b-estradiol (E2) enhances PTP through estrogen receptor (ER) signaling. Peak torques of potentiated twitches were 40%–60% greater than those of unpotentiated twitches and such PTP was greater in ovary-intact mice, or ovariectomized (Ovx) mice treated with E2, compared with Ovx mice (P < 0.047). PTP did not differ between mice with and without ERa ablated in skeletal muscle fibers (P = 0.347). Treatment of ovary-intact and Ovx mice with ERb antagonist and agonist (PHTPP and DPN, respectively) did not affect PTP (P = 0.258). Treatment with G1, an agonist of the G protein-coupled estrogen receptor (GPER), significantly increased PTP in Ovx mice from 41 ± 10% to 66 ± 21% (means ± SD; P = 0.034). Collectively, these data indicate that E2 signals through GPER, and not ERa or ERb, in skeletal muscles of female mice to augment an in vivo parameter of strength, namely, PTP.

Rapid And Direct Action Of Lipopolysaccharide (Lps) On Skeletal Muscle Of Larval Drosophila, Rachel Potter, Alexis Meade, Samuel Potter, Robin L. Cooper

Biology Faculty Publications

The endotoxin lipopolysaccharide (LPS) from Gram-negative bacteria exerts a direct and rapid effect on tissues. While most attention is given to the downstream actions of the immune system in response to LPS, this study focuses on the direct actions of LPS on skeletal muscle in Drosophila melanogaster. It was noted in earlier studies that the membrane potential rapidly hyperpolarizes in a dose-dependent manner with exposure to LPS from Pseudomonas aeruginosa and Serratia marcescens. The response is transitory while exposed to LPS, and the effect does not appear to be due to calcium-activated potassium channels, activated nitric oxide synthase …

Do Hypothermic Tissue Tolerances Limit Torpor Expression?, Clark J. Cotton, Henry J. Harlow

Biology Faculty Publications

1. Arrest temperatures and Q₁₀ values for extensor digitorum longus (EDL), soleus, trabecula, and jejunum muscle twitch strength, contraction time, and 0.5 relaxation time were calculated for a deep torpor hibernator, white-tailed prairie dog (WTPD) (Cynomys leucurus), a shallow torpor hibernator, black-tailed prairie dog (BTPD) (Cynomys ludovicianus), and a non-hibernator, lab rat (Rattus norvegicus) to test the hypothesis that tissue temperature tolerances limit the depth of expressed torpor.

2. There were no temperature tolerance differences between the tissues of the two species of hibernators. Both hibernating species had arrest temperatures and Q_{10 …}