Determinants and characteristics of female migration: a case study of Salem City in Tamil Nadu,India

A random sample of 521 male and 481 female migrants surveyed in Salem city in Tamil Nadu, India, during 1980-1981 was analyzed on the basis of a classification related to reasons (association, marriage, distress, and voluntary) for migration. Women were found to outnumber males in associational migration, both in rural to urban and urban to urban streams. They also formed almost all the marriage migrants. They were more numerous in distress migration as well. There were, however, comparatively few women among voluntary migrants. The incidence of illiteracy among migrant women was generally high, except for voluntary migrants who had completed high school. The share of working women was not negligible, but in most cases present work status was achieved after migrating.     

铁同位素的MC-ICP-MS测定方法与地质标准物质的铁同位素组成

详细报道了在低分辨和高分辨模式下运用MC-ICP-MS进行Fe同位素比值高精度测试的方法,对Fe同位素测定过程中谱峰干扰、基质效应、浓度效应、仪器测试的长期重现性等问题进行了评估,并对两种运行模式的测试结果进行了对比.在95%的可信度范围内,所建方法的外部精度优于0.5ε/ainu,达到国际同类实验室的先进水平,并且低分辨和高分辨两种模式下获得的Fe同位素测试结果是一致的.在此基础上对国家地质标准物质GBW07105(玄武岩)和GBW 07111(花岗闪长岩)进行了Fe同位素测定.相对于Fe同位素国际标样IRMM-014,GBW07105的Fe同位素成分为:ε57Fe=1.9±0.3(20),ε56Fe=1.3±0.2(2σ),ε57/56Fe=0.6±0.1(2σ);GBW 07111的Fe同位素成分为:ε57Fe=1.8±0.4(2σ),ε56Fe=1.2±0.2(2σ),ε57/56Fe=0.6±0.1(2σ).     

Total content and chemical speciation of arsenic in the polychaete Sabella spallanzanii

An unusual feature has been observed in polychaetes regarding their capacity to accumulate high levels of relatively toxic forms of arsenic in specific tissues. Basal levels of arsenic and distribution of its compounds were investigated in tissues of the Mediterranean polychaete Sabella spallanzanii. Particularly high concentrations were measured in the branchial crown (1036+/-136 microg/g d.w.) and chemical speciation revealed that the predominant form was the relatively toxic dimethylarsinate (DMA). These data suggest a potential role of As as anti-predatory strategy in polychaetes.     

Analysis of medaka cytochrome P450 3A homotropic and heterotropic cooperativity

We have previously demonstrated that medaka CYP3A is associated with metabolism of several endobiotics including steroids and bile acids. In this study, we demonstrate that medaka CYP3A catalysis exhibits unusual kinetic behaviors consistent with allosteric interaction which cannot be described by hyperbolic kinetic models. Using 7-benzyloxy-4-(trifluoromethyl)-coumarin (BFC) and nonylphenol as CYP3A substrates, we describe both homotropic and heterotropic cooperative interactions. Given the role of CYP3A in maintaining the homeostatic balance for numerous endobiotics, enzymatic activation/inhibition by endocrine disruptors (EDCs) represents a putative (non-genomic) mechanism for endocrine disruption.     

Partitioning of polycyclic aromatic hydrocarbons between water and particles compared to bioaccumulation in mussels: a harbour case

Water and particles from three sites located in Halifax Harbour, near and further away from combined municipal sewage effluents (CMSE) were analysed for parental and alkylated polycyclic aromatic hydrocarbons (par and alkPAH). Bioavailability of PAH was compared for inter-tidal mussels collected at the same sites in April and November. The PAH fingerprint determined over 9 sampling times covering a period of 19 months differed more between phases (water and particles) and seasons, than between sites. In the spring, more alkPAH associated with diesel and gasoline were detected in the soluble phase, along with more bioaccumulation of alkPAH in inter-tidal mussels. A broader number of parPAH were detected in mussels collected in the fall. The mean sum of dissolved alkPAH concentrations was higher in water at the site closer to raw CMSE than at the other two sites and particles of that site. However, lowest bioconcentration factors (BCF) were determined in mussels of this more contaminated site. Similar biota-particle accumulation factors (BPAF) were determined for parPAH in mussels from the three sites, all lower than the BCF of alkPAH. The study indicates that sewage treatment plants will reduce the amount of parPAH especially larger than fluoranthene and pyrene from being deposited in the harbour; that alk naphthalenes and fluorenes present in water will continue to be discharged; that the disturbance of sediments can make particle-bound PAH available to mussels.     

Cloning of cytochrome P450 1A (CYP1A) genes from the hermaphrodite fish Rivulus marmoratus and the Japanese medaka Oryzias latipes

To use two small fish Rivulus marmoratus (Cyprinodontiformes, Rivulidae) and the Japanese medaka Oryzias latipes (Belloniformes) as testing models in molecular ecotoxicology, we have cloned the cytochrome P450 1A (CYP1A) gene after screening of both genomic DNA libraries, and sequenced 11,863 and 7,243 bp including all the exons and introns with promoter regions, respectively. The Rivulus and the medaka CYP1A gene consisted of seven exons (including non-coding exons) with high homology to mammals. In the promoter region, Rivulus CYP1A gene has seven xenobiotic response elements (XREs) and two metal response elements (MREs), while the Japanese medaka CYP1A gene has six XREs and four MREs. Interestingly, medaka CYP1A gene has a number of MREs at the promoter, which may affect its response on metal exposure. We describe here the gene structure of both fish CYP1A genes.     

Metal concentrations in sediments and clams in four Moroccan estuaries

Metals (Cd, Cu, Ni, Zn, Mn and Fe) were analyzed seasonally over three years in sediments and in tissues of the clam Scrobicularia plana in four Moroccan Atlantic estuaries: Loukkos, Sebou, Bou Regreg and Oum er Rbia. Of these metals, Cd was at the lowest concentrations in sediment. Concentrations of Cu, Zn, and to a lesser extent Ni, in sediments suggest greater contamination in Sebou and Bou Regreg than in the other estuaries. The fluctuations of Mn and Fe concentrations in the fine surface sediments reflect their continental origin and show seasonal variations that indicate soil run-off following rain events. Concentrations of Cu, Zn, and especially Ni in clam tissues in these estuaries were generally higher than in some other common bioindicator bivalve species. The seasonal variations in S. plana's tissue metal concentrations are linked to patterns of reproductive activity for all metals except Cd and possibly Zn, whose tissue concentrations may be regulated. Mn and Fe concentrations in S. plana were positively correlated to sediment levels of these metals.     

缺少密度或孔隙度测定数据的块体堆积速率的计算

缺少密度或孔隙度测定数据的块体堆积速率的计算Ｔ．Ｊ．Ｓ．Ｓｙｋｅｓ等块体堆积速率（ＭＡＲ）计算已被应用于深海钻探计划（ＤＳＤＰ）和大洋钻探计划（ＯＤＰ）岩心，以研究大洋盆地的沉积物演化，或把ＭＡＲ数据分离成岩石学成分以决定方解石补偿深度（ＣＣＤ）的历...     

Theoretical wind wave frequency spectra in shallow water

The method developed by Wen et al. (1988 a) for deriving theoretical wind wave frequency spectrum in deep water is extended to the case of water of finite depth, in which a parameter η=H/d is introduced, where H and d represent the average wave height and water depth respectively. The derived spectra reduce to those in deep water when η=0. The case of η=1/2 corresponds to waves impending to break because of the effect of the bottom. Simplified forms of spectra are given. The theoretical results agree with the observed spectra well.     

Sub-lethal effects of metal exposure: physiological and behavioural responses of the estuarine bivalve Macoma balthica

Variation in glycogen concentration, condition index (CI) and filtration activity were measured in the bivalve Macoma balthica buried in sediment and experimentally exposed to cadmium (Cd). The stress due to elevated but sub-lethal concentrations (300 ppb Cd) affected the overall fitness of the organism as all parameters monitored responded significantly. Lower concentrations tested (10, 30 and 100 ppb) only induced a significant decrease in filtration activity, which may play a protective role, enabling the organism to slow down its metabolic activity and preserving the integrity of its reserves (reflected by stable CI and glycogen levels). Hence, the various endpoints selected show different thresholds. Our results also demonstrate that under high exposure, small individuals loose proportionally more glycogen per unit of weight than larger ones, thus confirming the higher sensitivity of small individuals to metal contamination. Furthermore, exposure to intermediate concentration (30 ppb) seems to be beneficial to the small individuals as indicated by their high CI values compared to the control. These results showed thus that non-sigmoidal concentration-response relationship and sizes of individuals should be considered in monitoring programmes and risk assessment.