Timing of induction of labor and association with nighttime delivery: a retrospective cohort.

OBJECTIVE: To assess the risk of nighttime delivery associated with timing and method of labor induction. STUDY DESIGN: We reviewed records of 692 patients undergoing full, late or post-term labor induction at two large hospitals. Primary independent variables were start time (morning or evening) and method (prostaglandin or oxytocin). Relative risk was assessed for the primary outcome of nighttime delivery. RESULT: Two hundred and ninety-seven (42.9%) patients experienced nighttime delivery. The relative risk of nighttime delivery adjusted for age in multiparous women using oxytocin in the morning compared with oxytocin inductions in the evening was 0.31 (95% confidence interval (CI): 0.22 to 0.45). Among nulliparous women in the same group, the adjusted relative risk was 0.65 (95% CI: 0.36 to 1.19). For prostaglandin inductions, there was no difference in the risk of nighttime delivery based on timing of the induction in the evening (relative risk: 0.89; 95% CI: 0.71 to 1.10). CONCLUSION: The method used and the time at which induction is started affect risk of nighttime delivery. For multiparous patients receiving oxytocin, morning induction carries lower risk of nighttime delivery. For prostaglandins, timing of initiation did not affect risk of nighttime delivery.

Seed longevity and fire: germination responses of an exotic perennial herb in NW Patagonian grasslands (Argentina).

Fire affects grassland composition by selectively influencing recruitment. Some exotic species can increase their abundance as a consequence of fire-stimulated seed germination, but response may depend on seed age. Rumex acetosella L. (Polygonaceae, sheep's sorrel) is a cosmopolitan herb that has invaded NW Patagonia's grasslands. This species forms persistent soil seed banks and increases after disturbances, particularly fire. We studied how fire and seed longevity influence R. acetosella germination. In 2008, we conducted laboratory experiments where we exposed different-aged seeds (up to 19 years old) to heat, smoke, charcoal, ash and control treatments. Total percentage germination and mean germination time depended on both seed age and fire treatment. Germination of younger seeds decreased with increasing temperature. There was no general pattern in germination responses of different-aged seeds to smoke, charcoal and ash. While smoke improved the germination of fresh seeds, charcoal decreased germination. Germination of untreated seeds was negatively correlated with seed age, and mean germination time increased with seed age. In most treatments, fresh seeds had lower germination than 1-5-year-old seeds, indicating an after-ripening requirement. Smoke stimulates R. acetosella germination, causing successful recruitment during post-fire conditions. Fresh seeds are particularly responsive to fire factors, possibly because they have not experienced physical degradation and are more receptive to environmental stimuli. Knowing the colonisation potential from the soil seed bank of this species during post-fire conditions will allow us to predict their impact on native communities.

Growth advantage of fast lactose-fermenting mutants of slow lactose-fermenting coliform bacteria in gnotobiotic rats and mice.

When germ-free rats or mice were mono-associated with either Escherichia coli lac(-) (ATCC 15939) or a slow lactose-fermenting coliform (Paracolobactrum coliforme ATCC 11605), fast lactose-fermenting mutants overgrew the parent organisms.