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Maternal obesity is associated with increased rates of labor induction, dysfunctional labor requiring intrapartum cesarean delivery, and postpartum hemorrhage, implying that maternal obesity has an inhibitory effect on myometrial function and its ability to respond to oxytocin. This study aimed to use an in vitro model to investigate the relationship between maternal body mass index (BMI) and the ability of myometrium to contract spontaneously and in response to oxytocin. Linear mixed effects regression modeling was applied to contractile data from 609 strips from 85 women. No correlation was found between maternal BMI and any indices of spontaneous myometrial activity. A single addition of oxytocin increased contractility, however, this was not related to maternal BMI. Similarly, oxytocin concentration-response curves were unrelated to BMI. Overall, the results from this in vitro study suggest that the observed implications of obesity on parturition in vivo cannot be explained by a direct effect on myometrial contractile mechanisms per se.

Objectives: Recent clinical trials have demonstrated a beneficial effect of supplementation with progesterone to prevent preterm labor. We aimed to determine the effects of progesterone treatment in vitro and in vivo and 17alpha-hydroxyprogesterone caproate (17OHPC) in vitro on myometrial contractions., Methods: Myometrial strips were taken from women undergoing cesarean delivery at term. We also obtained myometrial biopsies from women participating in a clinical trial of progesterone to prevent preterm labor in twins (STOPPIT). After establishment of spontaneous contractions, strips were exposed to progesterone or 17OHPC. Separate strips were exposed to oxytocin and tocolytics alone and in combination with progesterone. Potassium channel blockers were added in conjunction with progesterone. STOPPIT samples were used to compare the effects of in vivo progesterone and placebo. We measured amplitude, frequency and activity integral of contractions., Results: Maximum inhibition of contraction amplitude was 93 +/- 2% and 67 +/- 14% for progesterone at 30 microM and vehicle (70% ethanol), respectively, P < 0.05. 17OHPC did not exert an inhibitory effect. Water soluble progesterone exerted a maximal inhibitory effect on amplitude of contractions of 82 +/- 10% at 100 microM, P < 0.05. The inhibitory effect of progesterone was unaffected by potassium channel blockers. There was no difference between in vivo placebo and progesterone-treated groups in either amplitude or frequency of contractions, nor was there any difference in the response to oxytocin or the tocolytic drugs., Conclusions: Progesterone exerts rapid inhibition of the amplitude of myometrial contractions in vitro but 17OHPC does not. The action of progesterone does not appear to operate via potassium channels nor does it enhance the activity of certain tocolytic drugs.

The hair follicle has the unique capacity to undergo periods of growth, regression, and rest before regenerating itself to restart the cycle. This dynamic cycling capacity enables mammals to change their coats, and for hair length to be controlled on different body sites. More recently, the process of club fiber shedding has been described as a distinct cycle phase known as exogen, and proposed to be an active phase of the hair cycle. This review focuses on the importance of the shedding phase of the hair cycle and, in the context of current literature, analyzes the processes of club fiber formation, retention, and release, which may influence progression through exogen, particularly in relation to human hair.