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11.
Some flame retardants and the antimicrobials triclosan and triclocarban enhance the androgenic activity in vitro 总被引:1,自引:0,他引:1
Contaminants including flame retardants, antimicrobial agents and phthalates, occurring as residues in human tissues were associated with altered endocrine function. In our study we analysed the flame retardants tetrabromobisphenol A (TBBPA), hexabromocyclodecane (HBCD), penta-bromodiphenylether (BDE-100) and hexa-BDE (BDE-155), the antimicrobial compounds triclosan (TCS) and triclocarban (TCC) and eight phthalates for their androgenic and antiandrogenic activity in vitro in the MDA-kb2 cell line. No or only weak androgenic activity was observed for all the tested compounds. TBBPA showed weak antiandrogenic activity, which was demonstrated for the first time. The flame retardants HBCD, BDE-100 and BDE-155 enhanced the dihydrotestosterone-dependent activation of androgen receptor-responsive gene expression but exhibited little or no agonistic activity. The enhancement reached 150%, which was similar to the antimicrobials (TCS up to 180%, and TCC up to 130%). This enhancement of androgenic activity represents a novel mode of action of the endocrine activity of flame retardants. In contrast, most phthalates showed antiandrogenic activity. Butylbenzyl phthalate (BBP), dibutyl phthalate (DBP) and diethyl phthalate (DEP) showed strong antiandrogenicity, whereas the action of diethylhexyl phthalate (DEHP), dipentyl phthalate (DPP), dimethyl phthalate (DMP), and the DEHP metabolite monoethylhexyl phthalate (MEHP) was lower. Our in vitro study demonstrates for the first time a weak antiandrogenic activity of TBBPA, and a significant enhancement of the androgenic activity of HBCD, BDE-100 and BDE-155, which represents a novel mechanism of hormonal activity of flame retardants. 相似文献
12.
Christen E. Merte Thomas E. Goodwin Bruce A. Schulte 《Behavioral ecology and sociobiology》2010,64(3):401-408
Although communication is vital for members of a social species, the sexes may differ in the type and degree of information
sought. In many polygynous societies, males search for reproductively active females and compete intrasexually for access
to females with older males often being most successful. In social mammals, females may mature sooner than males and thus
at an earlier age behave more like adults. This maturation may include the assessment of potential mates directly or via indicative
signals. In this study, we observed the behavior of African elephants (Loxodonta africana) during their approach to waterholes. Waterholes provide an opportunity for elephants to investigate conspecific chemical
signals from feces and urine, and each other. We examined the presence of sexual dimorphism in behaviors of the trunk that
are indicative of olfactory investigation. We predicted that upon approach to a waterhole, adult males would show greater
interest than females in conspecific chemical signals. Females were predicted and observed to exhibit adult-like rates of
investigatory behavior at a younger age than males because females mature sooner. Adult males took the longest to reach the
waterhole in the last 100 m of approach; they also demonstrated greater investigatory rates to conspecific feces. Each sex
showed adult-type investigative behaviors with the trunk before the age of reproduction. Rather than showing a common chronological
developmental pattern across sex, the exhibition of investigatory, chemosensory behaviors reflected sex-specific changes in
reproductive development, perhaps reflective of the relative strength of intra- and intersexual selection on communication
patterns. 相似文献
13.
I.G. McKendry D. van der Kamp K.B. Strawbridge A. Christen B. Crawford 《Atmospheric environment (Oxford, England : 1994)》2009,43(36):5847-5852
Aerosol backscatter measurements from a Vaisala CL31 ceilometer are compared directly with a co-located 532/1064 nm lidar in order to validate the CL31 for remote sensing of vertical aerosol structure. The cases examined include a significant aerosol event (biomass burning), which by virtue of its vertical extent, provides a robust measure of the vertical range of the ceilometer for aerosol applications. A second case is presented when the instruments were separated in order to illustrate the utility of a network of such instruments for elucidating spatial patterns in aerosol distribution and the advection of elevated pollutant layers. When co-located, the instruments show remarkable agreement and indicate that the CL31 can detect aerosol layers up to 3000 m AGL in ideal conditions (at night and with high aerosol concentrations as found in biomass burning or dust plumes). When separated, multiple instruments provide an opportunity to examine advection of pollutant layers as well as their evolution. This suggests that installation of a ceilometer network would provide a cost-effective means of examining three-dimensional aspects of regional air quality as well as distinguishing between regional and local sources of pollution 相似文献
14.
Brian Miller Christen Wemmer Dean Biggins Richard Reading 《Environmental management》1990,14(6):763-769
Prairie dogs (Cynomys spp.) have been poisoned throughout this century because of grazing competition with livestock. Recent evidence showed these
early claims were exaggerated, but animal control was already entrenched in government policy. As a result, ongoing government
subsidized poisoning has reduced prairie dogs to about 2% of their former distribution. The reduction of prairie dogs diminished
species diversity in the arid grasslands of North America, including the potential extinction of the black-footed ferret (Mustela nigripes). Cost-benefit analysis revealed that poisoning costs more than any grazing benefits accrued. This analysis did not consider
the long-term costs of reversing ecosystem degradation, the intangible value of biological diversity as a public benefit,
or the depletion of biotic resources as a loss of actual or potential wealth. The government presently finances the poisoning
policy and the preservation of endangered species like the black-footed ferret, two apparently conflicting programs. We, therefore,
propose an integrated management plan that considers both interests. We propose that federal monies allocated to the poisoning
program be converted into a rebate for ranchers who manage livestock while preserving the prairie dog community. This would
redirect funds and personnel already allocated to prairie dog eradication to an incentive for ranchers who manage for livestock
and wildlife. Livestock interests and grassland biotic diversity would both benefit. 相似文献
15.
Jolly ID Walker GR Dowling TI Christen EW Murray E 《Journal of environmental management》2001,63(1):51-70
In order to prevent salinisation of the streams of the Riverine Plain of the Murray-Darling Basin in southern Australia, evaporation basins are used to dispose of saline irrigation drainage water. Local on-farm (individual landholder) and community (shared between multiple landholders) basins are increasingly being used to prevent export of salt outside irrigation districts. There are questions regarding the availability of land suitable for these basins and their impact on the surrounding environment. We describe the use of currently available spatial data to assist in regional planning for the environmentally safe use of these basins. A GIS-based approach was developed using suitability criteria expected to minimise the risk of off-site effects of basin leakage. The criteria were proximity to surface water features, urban areas and infrastructure, water table depth and salinity, and soil hydraulic conductivity. The approach was applied to all of the major irrigation districts at 1:250,000, the scale at which data are available over the entire Riverine Plain. Confidence in well-defined parameters such as proximity to infrastructure, urban areas and surface water features was higher than for those involving interpolated point data such as water table depth, salinity, and hydraulic conductivity. Most critically, hydraulic conductivity, the most important factor for basin leakage, was found to be unreliable at this scale. Use of higher resolution data (up to 1:100,000) available for two of the irrigation districts improved confidence in both water table depth and salinity but not in hydraulic conductivity. Despite these limitations, it was found that: (i) on-farm basins can only be used on an opportunistic basis in the eastern irrigation districts, but can be widely used in the western districts; (ii) community basins can be used anywhere there is suitable land; and (iii) the results raise serious questions as to whether there is enough suitable land in the eastern districts to dispose of all of the drainage water that is produced. 相似文献