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381.
382.
《植物生态学报》2017,41(11):1208
Methane (CH4) is an important greenhouse gas, and is involved in atmospheric chemical reactions. Aquatic and hydric environments are important sources of atmospheric CH4. Majority of CH4 are transported and released to atmosphere by emerged herbaceous plants and hygrophytes in aquatic and hydric environments. In recent decades, there has been increasing attention on how plants transport CH4. During CH4 transportation processes, several interfaces of CH4 exchange play important roles. First, the tips of lateral roots are primary locations (hotspots) for CH4 entering the root systems and regulate the gross CH4 transportation. Then, the diaphragms in the aerenchyma and the root collar impose great resistances for the overall CH4 transportation processes. In early studies, it was controversial that whether CH4 emission from plants to atmosphere was controlled by stomas or micropores (small cracks and holes in aboveground part of plant except the blade). Recent studies have confirmed the dominant role of micropores for CH4 transportation and emission. The dead and damaged stems are widely considered to have positive effects on CH4 transportation. Diffusion and convection are the two main transporting mechanisms of CH4, with the efficiency of convection being generally higher than that of diffusion. Both biological (e.g. biomass and photosynthesis) and environmental (e.g. light, temperature and humidity) factors regulate the CH4 transportation. Many studies have contributed to understanding the CH4 transportation processes and mechanisms by emerged herbaceous plants and hygrophytes. However, there are still some questions needing further investigations. Issues of consideration may include the operational efficiency in the critical interfaces of CH4 exchange, the plant parts that play a decisive role in the entire CH4 transportation, the underlying roles of diffusion and convection on CH4 interfaces exchanges and entire long distance transports, the combined and coupling effects and mechanisms of biotic and abiotic factors, and the similarities and differences of CH4 transporting processes and mechanisms among plant species. 相似文献
383.
Kathleen R. Pritchett‐Corning Charles B. Clifford Michael F. W. Festing 《Birth defects research. Part B, Developmental and reproductive toxicology》2013,98(2):200-205
Although rats in various stages of pregnancy are routinely shipped by vendors, the effects of shipping on pregnancy outcomes have not been reported. This study examined the effects of shipping rats 1 day after mating. Two outbred stocks, (Crl:CD(SD), Crl:WI(Han)) and one inbred strain (F344/Crl) of rats (n = 300/strain) were mated in a vendor barrier room at 3‐month intervals five times, and either shipped the next day (total time in transit ~24 hr) or held in the room of origin until parturition. The pregnancy status, length of gestation, number of pups born per female, sex ratio of pups born, and neonatal mortality were compared between transported and nontransported rats. These pregnancy and litter parameters were also compared among strains and examined for seasonality; no seasonal effects were observed. Neonatal mortality was negligible at less than 2% in any of the groups. All sex ratios were normal. Transportation affected pregnancy rates only in the F344/Crl, in which 81.8% of the nontransported versus 70% of the transported rats had pups (p = 0.025). Overall, slightly fewer transported rats were pregnant, but they had larger litters (10.08 compared with 9.68, p = 0.02, pooling across all three strains) so produced the same numbers of pups. A total of 77 ± 8% of transported rats had gestation periods of 22 days or more compared with only 52 ± 10% in the nontransported rats. The reason for larger litters in transported females is unclear. Longer gestation in transported females may be due to facultative embryonic diapause, which might have implications for reproductive toxicology. 相似文献
384.
A radioimmunoassay (RIA) method for measuring medroxyprogesterone acetate (MPA, Provera) in serum has been developed utilizing benzene:iso-octane extraction, 3H-MPA to assess procedural losses, goat anti-MPA-3-(0-carboxymethyl) oxime-bovine serum albumin serum and dextran-coated charcoal separation. Control serum blanks were undetectable, 200 pg/ml of MPA was measurable with a high reliability, and intra- and interassay coefficients of variation were 6 and 13 percent, respectively. MPA added to control serum was quantitatively recovered. Serum MPA levels measured in 2 women after ingestion of 10 mg MPA rose to 3.4 to 4.4 ng/ml within 1 to 4 hours after oral intake and fell rapidly thereafter to 0.3 to 0.6 ng/ml within 24 hours. Insertion of Silastic intra-vaginal rings (IVRs), containing 100 or 200 mg of MPA, into 4 women for periods of 3 weeks resulted in a rapid rise of serum MPA after insertion, rather stable MPA levels of 0.9 to 1.6 ng/ml while the IVRs were in place, and a rapid decline of serum MPA following IVR removal. Serum estradiol-17beta and progesterone concentrations, measured about 3 times a week in these patients, indicated that ovulation was consistently inhibited. The serum MPA levels observed in this study were approximately 5 times lower than those reported by other investigators using a double-antibody RIA of MPA in unextracted serum. 相似文献
385.