Biomechanical analysis of gait adaptation in the nematode Caenorhabditis elegans

To navigate different environments, an animal must be able to adapt its locomotory gait to its physical surroundings. The nematode Caenorhabditis elegans, between swimming in water and crawling on surfaces, adapts its locomotory gait to surroundings that impose approximately 10,000-fold differences in mechanical resistance. Here we investigate this feat by studying the undulatory movements of C. elegans in Newtonian fluids spanning nearly five orders of magnitude in viscosity. In these fluids, the worm undulatory gait varies continuously with changes in external load: As load increases, both wavelength and frequency of undulation decrease. We also quantify the internal viscoelastic properties of the worm's body and their role in locomotory dynamics. We incorporate muscle activity, internal load, and external load into a biomechanical model of locomotion and show that (i) muscle power is nearly constant across changes in locomotory gait, and (ii) the onset of gait adaptation occurs as external load becomes comparable to internal load. During the swimming gait, which is evoked by small external loads, muscle power is primarily devoted to bending the worm's elastic body. During the crawling gait, evoked by large external loads, comparable muscle power is used to drive the external load and the elastic body. Our results suggest that C. elegans locomotory gait continuously adapts to external mechanical load in order to maintain propulsive thrust.     

Effectiveness of nifedipine versus atosiban for tocolysis in preterm labour: a meta-analysis with an indirect comparison of randomised trials

Objective To explore the effectiveness of nifedipine compared with atosiban for tocolysis in preterm labour.
Design A systematic review of randomised controlled trials with meta-analysis using adjusted indirect comparison.
Population Six hundred and seventy-nine women recruited in nine randomised trials evaluating the effectiveness of nifedipine versus β-agonists, and 852 women recruited in four trials of atosiban versus β-agonists. There were no trials comparing nifedipine directly with atosiban.
Methods We performed meta-analysis with a technique involving an adjusted indirect comparison between nifedipine and atosiban using β-agonists as the common comparator. This approach preserves the benefit accrued by randomisation in the original comparisons.
Main outcome measures Reduction in neonatal respiratory distress syndrome and delay in delivery by 48 hours.
Results Nifedipine tocolysis was associated with a significant reduction in respiratory distress syndrome compared with atosiban (OR 0.55, 95% CI 0.32–0.97). It also increased the number of women whose delivery was delayed by 48 hours (OR 1.20, 95% CI 0.73–1.95), although this result was not statistically significant.
Conclusions When indirectly compared with atosiban, nifedipine tocolysis is more effective. In the absence of a direct comparison, our analysis provides a way to explore the potential benefits of nifedipine versus atosiban.     

A diacylglycerol kinase modulates long-term thermotactic behavioral plasticity in C. elegans

A memory of prior thermal experience governs Caenorhabditis elegans thermotactic behavior. On a spatial thermal gradient, C. elegans tracks isotherms near a remembered temperature we call the thermotactic set-point (T(S)). The T(S) corresponds to the previous cultivation temperature and can be reset by sustained exposure to a new temperature. The mechanisms underlying this behavioral plasticity are unknown, partly because sensory and experience-dependent components of thermotactic behavior have been difficult to separate. Using newly developed quantitative behavioral analyses, we demonstrate that the T(S) represents a weighted average of a worm's temperature history. We identify the DGK-3 diacylglycerol kinase as a thermal memory molecule that regulates the rate of T(S) resetting by modulating the temperature range of synaptic output, but not temperature sensitivity, of the AFD thermosensory neurons. These results provide the first mechanistic insight into the basis of experience-dependent plasticity in this complex behavior.     

A randomized controlled trial of prophylactic antibiotics (co-amoxiclav) prior to embryo transfer

BACKGROUND: Bacterial contamination of the transfer catheter during embryo transfer is associated with poor clinical outcomes. Antibiotics at the time of embryo transfer may improve outcomes. We evaluated the effect of co-amoxiclav on the rates of bacterial contamination of transfer catheters and clinical pregnancy. METHODS: On the day of oocyte collection, 350 patients were randomized, with sequentially numbered opaque-sealed envelopes containing treatment allocation assigned randomly by computer, to receive co-amoxiclav on the day before and the day of embryo transfer, or no antibiotics. Following transfer, the catheter tips were cultured and assessed to identify the organism(s) isolated and to quantify the level of the contamination. Couples were followed for 8 weeks to determine whether they had achieved clinical pregnancy. Outcome assessors were blinded to the treatment allocation, and the analysis was by intention to treat. RESULTS: Antibiotics significantly reduced catheter contamination rates (49.4 versus 62.3%, RR = 0.79, 95% CI: 0.64, 0.97, P = 0.03). There was no difference detected in clinical pregnancy rates between the two groups (36.0 versus 35.5%, P = 0.83) although there was a significant (P = 0.03) association between the level of bacterial contamination and clinical pregnancy rates. CONCLUSIONS: Co-amoxiclav reduces catheter contamination, but this is not translated into better clinically relevant outcomes such as clinical pregnancy rates. Our findings do not support the routine use of antibiotics at embryo transfer.