Background and Aims In some clinical studies men and women have been found to differ in their ability to quit smoking, perhaps as a result of progesterone. The primary aim of this study was to provide a preliminary test of whether progesterone (PRO), compared with placebo (PBO), was more effective for smoking cessation in men and women. Design Pilot double‐blind, placebo‐controlled randomized clinical trial. Setting Minneapolis/St Paul metro area, Minnesota, USA. Participants A total of 216 participants were randomized, including 113 men (18–60 years; PRO = 56, PBO = 57) and 103 women (18–50 years, pre‐menopausal with self‐reported regular menstrual cycles; PRO = 51, PBO = 52). Intervention Participants were randomized (1 : 1 within sex group) to either PRO (200 mg twice daily) or PBO. Participants were assigned a quit date approximately 7 days after starting medication (luteal phase for women) and were followed for 12 weeks to assess relapse. Measurements The primary outcome was self‐reported 7‐day point prevalence abstinence (PPA) at week 4. Secondary outcomes included 7‐day PPA at weeks 8 and 12, prolonged abstinence, continuous abstinence, urine cotinine < 50 ng/ml, expired carbon monoxide ≤ 5 parts per million (p.p.m.) and days to relapse. Findings There was a significant difference in 7‐day PPA at week 4 among women [PRO: 18 (35.3%) versus PBO: 9 (17.3%), odds ratio (OR) = 2.61, 95% confidence interval (CI) = 1.04, 6.54, P = 0.041], but not among men [PRO: 13 (23.2%) versus PBO: 12 (21.1%), 1.13 (0.47, 2.76), P = 0.782]. There was some evidence that PRO delayed relapse in women (days to relapse; PRO: 20.5 ± 29.6 versus PBO: 14.3 ± 26.8, P = 0.03) but not in men (PRO: 13.4 ± 25.9 versus PBO: 13.3 ± 23.8, P = 0.69). Conclusions Oral micronized progesterone may aid smoking cessation in women.
Stable isotopes 13 C and 15 N are often used in lake ecosystems to assess energy sources and trophic positions, respectively. However, d 13 C and d 15 N are also influenced by internal biogeochemical processes in epilimnetic and hypolimnetic habitats in lakes, but the extent to which biogeochemical processing mediates isotope values between these two habitats, and whether these patterns are influenced by lake productivity is not known. We sampled d 13 C and d 15 N in epilimnetic mussels, Chaoborus, cisco (Coregonus artedi), and seston and zooplankton in the epilimnia and hypolimnia of 22 Minnesota (USA) lakes ranging from oligotrophic to eutrophic. We also measured lake temperature-oxygen profiles and light levels to assess factors influencing isotope patterns. Isotope samples were baseline-corrected using epilimnetic mussels in each lake (sample-mussel) to control for watershed-level differences in isotope values. Results showed d 13 C in epilimnetic and hypolimnetic zooplankton, hypolimnetic seston, Chaoborus, and cisco became more depleted in d 13 C relative to epilimnetic mussels in low-productivity lakes where light penetrated into the hypolimnion, while epilimnetic seston d 13 C stayed similar to mussel d 13 C in all lakes. This pattern was likely due to hypolimnetic phytoplankton in clearwater lakes incorporating more respired CO 2 , which is depleted in d 13 C, and subsequently passing depleted d 13 C values up the food chain. Results also showed habitat differences in d 15 N with epilimnetic and hypolimnetic zooplankton, hypolimnetic seston, Chaoborus, and cisco becoming more enriched relative to epilimnetic mussels in low-productivity lakes with higher O 2 levels in the hypolimnion, while epilimnetic seston d 15 N remained similar to mussel values. The d 15 N pattern is consistent with the idea that denitrification and microbial degradation enriched hypolimnetic seston relative to epilimnetic seston in low nutrient lakes, while enhanced epilimnetic primary production enriched epilimnetic d 15 N seston relative to hypolimnetic seston in high nutrient lakes. Our results indicate isotopic differences between epilimnetic and hypolimnetic organisms that change along productivity gradients and suggest that microbial processes and the light regime are important drivers.
Cisco (Coregonus artedi) are threatened by climate change and lake eutrophication, and their oxythermal habitat can be assessed with TDO3, the water temperature at which dissolved oxygen equals 3 mg L-1. We assessed the influence of TDO3 on cisco habitat use, genetic diversity, diets, and isotopic niche in 32 lakes ranging from oligotrophic to eutrophic. Results showed that as TDO3 increased cisco were captured higher in the water column, in a narrower band, with higher minimum temperatures and lower minimum dissolved oxygen. TDO3 was also negatively related to cisco allelic richness and expected heterozygosity, likely driven by summer kill events. Moreover, TDO3 influenced the isotopic niche of cisco, as fish captured deeper were more depleted in δ13C and more enriched in δ15N compared to epilimnetic baselines. Lastly, cisco in high TDO3 lakes consumed more Daphnia, had fewer empty stomachs, and achieved larger body size. Our work identifies specific characteristics of cisco populations that respond to climate change and eutrophication effects, and provides a framework for understanding responses of other cold-water species at the global scale.
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