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排序方式: 共有253条查询结果,搜索用时 15 毫秒
61.
Xiaoqing Ye Wuye Pan Chunming Li Xiaochen M Shanshan Yin Jianhong Zhou Jing Liu 《环境科学学报(英文版)》2020,32(5):1-9
Polycyclic aromatic hydrocarbons (PAHs) are a typical class of persistent organic pollutants that is ubiquitous worldwide. Previous animal studies suggested that PAHs had adverse effects on female reproduction. However, the human data regarding relationship of PAHs exposure with women reproductive health, such as ovarian dysfunction, are scarce. In this case-control study, the associations of serum levels of PAHs with the risk of premature ovarian failure (POF) and reproductive hormones in Chinese women were investigated, with recruiting 157 POF patients and 217 healthy women. The serum levels of 12 types of PAHs, as well as reproductive hormones, including follicle-stimulating hormone, luteinizing hormone and anti-mullerian hormone, were determined. In the logistic regression models, most individual PAH congeners showed significantly positive correlations with the risk of POF (p < 0.05), except for fluorine and pyrene. Benzo(a)pyrene (BaP), as the most carcinogenic PAH congener, was observed to be significantly positively associated with the risk of POF. After adjustment for age, body mass index, educational levels and household income, per one-unit increase in the log-transformed BaP concentration was significantly correlated with 2.191-fold increased risk of POF (OR = 2.191, 95%CI: 1.634–2.938, p < 0.05). To the best of our knowledge, this is the first study to report an association between internal exposure levels of PAHs and the increased risk of POF in women. 相似文献
62.
Rita Covas Morné A. du Plessis Claire Doutrelant 《Behavioral ecology and sociobiology》2008,63(1):103-112
Some studies on the effects of helpers in cooperatively breeding vertebrates show a positive effect of helper presence on
reproductive output whereas others find no effect. One possibility for this discrepancy is that helpers may have a positive
effect when breeding conditions are adverse, while their effect might go unnoticed under good conditions. We investigate this
hypothesis on sociable weavers Philetairus socius, a colonial cooperatively breeding passerine that inhabits a semi-arid region where breeding conditions vary markedly. We
used multivariate mixed models to analyse the effect of helpers on reproduction under contrasting environmental and social
conditions while controlling for parental and colony identity. We found that reproductive success in sociable weavers was
primarily influenced by nest predation and rainfall. In addition, colony size was negatively associated with hatching and
fledging success and number of young fledged per season. Helpers had a less prominent but significant influence on feeding
rates and reproductive outcome. In agreement with expectations, the presence of helpers counteracted some of the negative
effects of breeding in periods of low rainfall or in large colonies and was also associated with an increased number of young
fledged per season. Our results illustrate that the effect of helpers might be detectable mostly under unfavourable conditions,
but can contribute to improve reproductive performance in those situations. 相似文献
63.
High rates of extra-pair young in the pair-living fat-tailed dwarf lemur, Cheirogaleus medius 总被引:6,自引:0,他引:6
J. Fietz H. Zischler C. Schwiegk J. Tomiuk K. H. Dausmann J. U. Ganzhorn 《Behavioral ecology and sociobiology》2000,49(1):8-17
Cheirogaleids are one of the most primitive extant primate taxa in the world. Their lifestyle and mating system, therefore,
have been considered to be representative for social systems in primate ancestors. Accepted models of social evolution in
primates state that pair-bonding has evolved secondarily from diurnal group-living taxa and should therefore be constrained
primarily to diurnal species. In contrast to these assumptions, the nocturnal fat-tailed dwarf lemur (Cheirogaleus medius) lives in permanent pairs, with obligate paternal care probably representing the evolutionary basis of pair-living. In this
sociobiological field study, we analyzed the reproduction strategy of C. medius in the tropical forest of western Madagascar. In the rainy seasons from 1995 to 1999, 173 individuals of C. medius were captured and individually marked and 131 were genetically characterized through seven microsatellite loci. Additionally,
36 of these individuals were radio-tracked and observed. For 53 genotyped individuals, including 16 offspring, information
about pair-bonding and family structure was known from field observations. Genetic analyses revealed that yearlings and infants
living with an adult pair were in all cases sibs of the social mother. However, C. medius does not restrain from extra-pair copulations (EPCs) and a high rate of extra-pair paternity (44%) was detected. Males sired
offspring with their female partners as well as with extra-pair females within the same year, indicating that males may increase
their reproductive success by EPCs without necessarily running the risk of cuckoldry. Females on the other hand do not seem
to run the risk of reduced paternal care, either because males cannot detect relatedness of young, or because they might even
increase their inclusive fitness by raising offspring of closely related males. Since females reproduce preferentially with
territory holders and no paternity could be assigned to floating males, superior genetic quality of the males might be crucial
for female choice.
Received: 12 January 2000 / Revised: 15 August 2000 / Accepted: 26 August 2000 相似文献
64.
Jingjing Sha You Wang Jianxia Lv Hong Wang Hongmei Chen Leilei Qi Xuexi Tang 《环境科学学报(英文版)》2015,28(2):54-63
Polybrominated diphenyl ethers(PBDEs) are new kinds of persistent organic pollutants(POPs) and their potential threats to the equilibrium and sustainability of marine ecosystems have raised worldwide concerns. Here, two kinds of PBDEs, tetra-BDE(BDE-47)and deca-BDE(BDE-209) were applied, and their toxic effects on the swimming behavior,population growth and reproduction of Brachionus plicatilis were investigated. The results showed that:(1) The actual concentrations of BDE-47 and-209 in the seawater phase measured by GC–MS(Gas Chromatography-Mass Spectrometer) were much lower than their nominal concentrations.(2) In accordance with the 24-hr acute tests, BDE-209 did not show any obvious swimming inhibition to rotifers, but a good correlation did exist between the swimming inhibition rate and BDE-47 concentration suggesting that BDE-47 is more toxic than BDE-209.(3) Both BDE-47 and-209 had a significant influence on the population growth and reproduction parameters of B. plicatilis including the population growth rate, the ratio of ovigerous females/non-ovigerous females(OF/NOF), the ratio of mictic females/amictic females(MF/AF), resting egg production and the mictic rate, which indicate that these parameters in B. plicatilis population were suitable for monitoring and assessing PBDEs. Our results suggest that BDE-47 and-209 are not acute lethal toxicants and may pose a low risk to marine rotifers at environmental concentrations for short-term exposure. They also accumulate differently into rotifers. Further research data are needed to understand the mechanisms responsible for the effects caused by PBDEs and to assess their risks accurately. 相似文献
65.
66.
Polybrominated diphenyl ethers (PBDEs) are new kinds of persistent organic pollutants (POPs) and their potential threats to the equilibrium and sustainability of marine ecosystems have raised worldwide concerns. Here, two kinds of PBDEs, tetra-BDE (BDE-47) and deca-BDE (BDE-209) were applied, and their toxic effects on the swimming behavior, population growth and reproduction of Brachionus plicatilis were investigated. The results showed that: (1) The actual concentrations of BDE-47 and -209 in the seawater phase measured by GC-MS (Gas Chromatography-Mass Spectrometer) were much lower than their nominal concentrations. (2) In accordance with the 24-hr acute tests, BDE-209 did not show any obvious swimming inhibition to rotifers, but a good correlation did exist between the swimming inhibition rate and BDE-47 concentration suggesting that BDE-47 ismore toxic than BDE-209. (3) Both BDE-47 and -209 had a significant influence on the population growth and reproduction parameters of B. plicatilis including the population growth rate, the ratio of ovigerous females/non-ovigerous females (OF/NOF), the ratio of mictic females/amictic females (MF/AF), resting egg production and the mictic rate, which indicate that these parameters in B. plicatilis population were suitable for monitoring and assessing PBDEs. Our results suggest that BDE-47 and -209 are not acute lethal toxicants and may pose a low risk to marine rotifers at environmental concentrations for short-term exposure. They also accumulate differently into rotifers. Further research data are needed to understand the mechanisms responsible for the effects caused by PBDEs and to assess their risks accurately. 相似文献
67.
Miklos Domokos Jean Weber Lucien Duckstein 《Journal of the American Water Resources Association》1976,12(2):263-275
ABSTRACT. Methodological problems associated with forecasting water requirements by use of regression analysis are examined. Problems occurring when long-range forecasts are based on linear and nonlinear extrapolation of time series models include possible changes in socioeconomic conditions, water allocation system structure, and limits to growth. Problems arising in forecasting based on multiple regression models are likely to involve serially dependent errors, multicollinear explanatory variables, and difficulties inherent to the presence of explanatory variables that must themselves be predicted. 相似文献
68.
Laszlo David Lucien Duckstein 《Journal of the American Water Resources Association》1976,12(4):731-754
ABSTRACT The definition and comparison of alternative water resource systems designed to meet long-range goals (say 60 years) is illustrated by a case study in Hungary. A comprehensive cost-effectiveness approach is adapted to define goals, specifications, criteria, alternatives and their capabilities. Specifications include demands given in probabilistic terms. The comparison of alternative systems is based on 12 criteria, one of which is the balance between total energy consumed and peak energy produced. Important factors involving social elements, such as flood protection and land and forest use, are described both as monetary quantities and as qualitative appreciations. Five alternative systems are defied involving flat land reservoirs, pumped storage reservoirs, interbasin transfer, and conjunctive use of surface and ground water. International cooperation is then used to rank systems and reduce the problem to a tradeoff between only two alternatives. 相似文献
69.
ABSTRACT: The Yellowstone River historically has produced an ample supply of high quality water which is widely used for irrigation, municipal and industrial purposes, recreation, and fish and wildlife. Recently, energy companies have attempted to obtain water rights in the Yellowstone basin for energy conversion facilities in coal-rich southeastern Montana. Existing users fear that energy diversions will impair their rights, preclude expansion of present beneficial users, degrade water quality, and adversely effect fish and aquatic life. In response to these concerns, the Montana Legislature enacted several laws to regulate water appropriations in the Yellowstone River basin, including means by which state and federal agencies could apply for reservations of water for future beneficial uses. Thereafter, both the Montana Fish and Game Commission and the State Water Quality Bureau formally requested relatively large instream flows to protect fish and wildlife and to maintain water quality. This paper describes Montana's experience through December of 1977 with the administration of water in the Yellowstone basin under these laws; emphasis is placed on the major requests for instream flows. The final resolution of the reservation applications, and the related ramifications, will be discussed in a future paper. 相似文献
70.
Jürgen Heinze Björn Oberstadt Jutta Tentschert Bert Hölldobler Hans Jürgen Bestmann 《Chemoecology》1998,8(4):169-174
Summary. Queens in colonies of the small myrmicine ant, Leptothorax gredleri Mayr 1855 (Hymenoptera, Formicidae) engage in dominance interactions and form social hierarchies, in which typically only
the top-ranking queen lays eggs. Occasionally, queen antagonism escalates to violent mandible fighting, during which the sting
is used to apply Dufour gland secretions onto the cuticle of the opponent. Contaminated queens often are attacked by nestmate
workers. Here we show that the chemical composition of the Dufour gland is colony-specific and that workers can discriminate
between secretions from their own and other colonies. Our findings suggest that Dufour gland secretions are involved in the
establishment of hierarchies within a colony. When invading an alien colony the queen presumably employs the secretions during
the expulsion of the resident queen. Apparently, Dufour gland secretions play a role in intraspecific queen competition similar
to that in slave-making and inquiline formicoxenine ants, where they function as "propaganda substances" in an interspecific
context.
Received 7 July 1998; accepted 15 September 1998. 相似文献