首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
4.
In vertebrates, neurotoxicants are chemicals whose primary toxic effect is on the nervous system, either the central nervous system (CNS {brain and spinal cord}) or the peripheral nervous system (PNS {spinal roots, sensory ganglia, peripheral nerves}). Pathological aspects of neurotoxicity are well documented in experimental mammals. We illustrate the neurotoxicity of two chemicals, which both produce lesions in selective regions of the rat brain, a thiocarbamate herbicide (cycloate) and an industrial chemical, chloropropionic acid (L-CPA). Cycloate exposure results in neuronal cell death by apoptosis in specific areas of the forebrain, whereas L-CPA produces granule cell necrosis in the cerebellum. Our studies in rodents demonstrate the discriminative power of neuropathological tools for neurotoxicity. Many agrochemicals/industrial chemical products enter the aquatic environment, some with the potential for neurotoxicity. The teleost CNS is the most primitive among the vertebrates but has features in common with the CNS of more advanced forms. Even allowing for differences in phylogenetic organisation, neuropathological tools should have the potential to identify neurotoxicants that affect teleosts.  相似文献   

5.
China and Japan’s June 2008 agreement in principle on maritime cooperation in the East China Sea raised hopes of a significant breakthrough in the parties' complex and long-standing disputes in the area. Subsequent progress towards the realisation of a legally binding, formal treaty on, for example, offshore petroleum joint development has been slow to materialise. In fact, the area under dispute appears to have become more rather than less extensive. This paper examines competing maritime and sovereignty claims in the East China Sea together with progress towards maritime cooperation in the context of overlapping jurisdictional claims. The paper identifies some of the key challenges that need to be overcome in realizing a functioning joint resource management regime in the East China Sea.  相似文献   

6.
Repeated surveys at control sites in the gas accumulation fields from the Ría de Arousa (Galicia, NW Spain) have shown that the top of the acoustic turbidity fluctuates vertically. The vertical movement of gas fronts is more apparent in the gas fields located in the outer ría, where fluctuations of up to 1.5 ms (1.1 m) have been detected. At the inner ría, the depth to the top of the gas horizons varied between 0.5 and 1 ms (40 to 80 cm). Short-term (diurnal) fluctuations associated with the hydrostatic pressure variations of the water column during a tidal cycle have been identified as the most likely factors to explain fluctuations of gas fields in the outer ría. At the inner ría, gas fields are affected by these short-term pressure changes superimposed on long-term temperature and salinity variations of bottom water masses. This combination produces a different pattern of variation in gas fields from the inner and the outer ría. Prominent pockmarks and acoustic plumes have also been monitored throughout the three seismic surveys. Many of these pockmarks exhibit active characteristics, including the observance of plumes of escaping fluids and sediment.  相似文献   

7.
In this study, we exposed female medaka to aqueous solutions of o,p′-DDT until tissues residues reached approximately 100 g/g. Male offspring of exposed females and unexposed males that were raised to 6 months of age differed from untreated controls in their response to subsequent 4-day static exposure to 17-β-estradiol (E2; 12 μg/l as determined by steroid EIA). Homogenized liver samples from males from DDT treatments, females from DDT treatments, control males and control females produced two vitellogenin bands on a Western blot with no qualitative differences in band size and location between the groups. To quantify the relative level of vitellogenin, 5 μg of protein from each sample was analyzed by slot blot. A statistical comparison revealed a significant difference in optical density of the slots between control males and DDT exposed males (analysis of variance, n=18, P=0.021; Tukey test, n=9, P=0.047) indicating that previous transgenerational exposure to DDT enhanced the vitellogenic response to E2 exposure in males. These results indicate that exposure to estrogenic chemicals may produce an ‘estrogen memory’ which potentiates the response to a subsequent exposure event.  相似文献   

8.
In Belgium a long process (1999–2005) led to the designation of several marine protected areas (MPAs). In order to analyse the designation process, the ‘policy arrangement approach’ was used as an analytical tool. Attention was given to four dimensions (actors and coalitions, arguments, rules and resources). Particular attention was paid to the switch from an authoritative to a more deliberated policy style in reaction to conflicts with stakeholders. This switch in policy style contributed to a successful legal designation, but does not guarantee the best protection of marine biodiversity. This case study linked science (setting ecological goals) to policy (analysis of a policy process) and led to some more general conclusions on the designation of MPAs and the role of participation in this process.  相似文献   

9.
The Svalbard Fisheries Protection Zone is an international institution on the brink of being challenged in a critical phase of being institutionalized as a Norwegian property regime. The potential disturbance comes from the zooplankton redfeed, a new and valuable resource harvestable within the zone. Though the pressures on Norway’s inspection routines in the zone are challenged at times, this article suggests that the zone as a management regime is a surprisingly robust institution still. Nevertheless, in such a critical phase it is important not to allow possible exogenous shocks to appear, and creating a separate redfeed regime for the plankton will allow the Norwegian government to bypass this possible disturbance and allow for continued solidification of the zone into an EEZ for Norway.  相似文献   

10.
P-glycoprotein (pgp), an efflux transporter localized in a variety of tissues including the intestinal mucosa, renal tubules and bile canaliculi, is known to participate in the disposition of a variety of chemicals, including steroid hormones. This study examined the relationship of pgp to the movement into the bile of the hormone estradiol (E2), and the potential for transport interactions between the environmental pollutant nonylphenol ethoxylate (NPE) and E2. Biliary-cannulated in situ-prepared isolated perfused livers were used to assess pgp transport function. E2, in competitive transport preparations with Rhodamine 123 (Rho123), a pgp substrate, demonstrated significant decreases in Rho123 transport into bile, as did the prototypic inhibitor and substrate verapamil. [3H]E2 (0.28 nM) transport into bile was significantly reduced with either 20 M NPE or verapamil. These results suggest that E2 is a substrate and/or modulator for the catfish biliary pgp transporter, and that NPE potentially influences biliary transport and excretion of E2.  相似文献   

11.
This paper examines the Arctic Search and Rescue Agreement—the first legally-binding instrument negotiated and adopted under the auspices of the Arctic Council—and analyzes its implications for the current Arctic regime. Led by the Arctic Council, the Arctic regime was established in a soft law format. However, the soft law nature and restricted mandates of the Arctic Council have limited its capacity to respond to new issues emerging from climate change, particularly those related to the exploitation of oil and gas reserves, commercial shipping through the region, effects on wildlife, and impacts on indigenous peoples' homelands and culture. The adoption of the Agreement represents a new approach for the Arctic States to respond to these new challenges. At the same time, it does not imply that a legally-binding instrument is necessarily preferable for every issue, and importantly, the new Arctic Agreement does not establish new institutional relationships, suggesting satisfaction among the Arctic States with the existing arrangements. Thus, although the Arctic regime is undoubtedly changing, this change should not be treated today as a shift from soft to hard law. What is more certain is that the Arctic Council will continue to function as a cooperative forum where the Arctic States can address these challenges, and its importance will only increase in coming years.  相似文献   

12.
The Magnuson-Stevens Fishery Conservation and Management Act (1976), opened a new era of federal fishery management in the United States. It was enacted primarily to establish a system for conserving and managing fisheries in the new 200-mile (EEZ). The US assumed exclusive authority for managing all fisheries within the EEZ, except for highly migratory species such as tunas and billfishes. Within the framework of the Act, eight Regional Fishery Management Councils (Regional Councils) were created, which are responsible for preparing Fisheries Management Plans (FMPs) in federal waters under their jurisdiction. Each FMP must meet a series of National Standards (NSs) for conservation and management. The Act was reauthorized in 1996 with the passage of the Sustainable Fisheries Act (SFA), which aimed at fine tuning the fishery regulatory apparatus that was established under the original Act. This "fine tuning" involved increased attention to biological concerns, and removal of ambiguities within it. The Act was reauthorized again in 2007, mainly to provide for more clear directives and regulations to end overfishing. After more than thirty years since the Act was passed into law, the debate among conservationists, commercial and recreational fishery representatives, and politicians on the effectiveness of the Act in achieving its purported goals it still continues. Is the Act delivering on its promises? Do NSs reflect the most important priorities for the US fishery resources, conservation and sustainable exploitation? Do the Regional Councils represent all parties that should be involved in the fisheries resources management? The aim of this paper is to provide a critical analysis to answer these questions. This paper begins with a review of the Act and its background, followed by discussion and analysis of the Act's benefits and flaws. Finally, suggestions for the implementation of its structure and future directions in fishery management strategies are made.  相似文献   

13.
14.
A landing obligation was formally implemented in the European Union (EU) for the first time, as part of the recent reform of the EU Common Fisheries Policy (CFP). Given the reasonable success of the landing obligation in some countries such as the Faroe Islands, Iceland and Norway, this policy is seen as a viable approach to tackle the long-recognized discarding problem in EU waters. However, there has been some debate on whether there is sufficient evidence to support the feasibility of such a measure in the EU-CFP. The EU landing obligation will implicitly include all small-scale fisheries (SSF) provided the species captured are subject to catch limits or minimum sizes (in the case of the Mediterranean). SSF were included irrespective of the fact that the discarding problem in the EU has been historically associated with medium- to large-scale fleets (in particular largely mixed species trawl fisheries). Additionally, past experiences with a discard ban policy are still limited to specific countries and/or specific fisheries. This paper examined the appropriateness and feasibility of the recently implemented EU landing obligation in SSF. The effects in the long-term are unpredictable, but available evidence suggests that in the short to medium-term a landing obligation is likely to bring more negative social, economic and ecological impacts than benefits.  相似文献   

15.
In the last few decades there has been a surge in research focusing on coral disease. While climate change, specifically rising sea surface temperature, has been proposed as a major and growing driver of the emergence of marine diseases, to date a solid connection between disease epizootics and elevated sea surface temperature has not been established. However, a wealth of data now exists, compiled from many different perspectives, that may support such a connection. In this work we provide a comprehensive review targeting one coral disease, black band disease, that spans the infection process, pathobiology, and epizootiology, and links specific mechanisms of the disease process to increasing temperatures. This temperature‐driven pattern of infection can be expanded to include similar processes associated with other temperature‐related coral diseases. The conclusions presented here are based upon the results of many studies using a diverse suite of approaches that have been synthesized to argue that the emergence and continuing spread of black band disease is linked to warming sea surface temperatures. In summary, as global ocean temperatures increase seasonally and over decades, the environment shifts to become more favorable for the growth of potentially pathogenic microorganisms endemic to the immediate environment of the reef. The increase in the relative number of potential pathogens in the microbial community produces microenvironments conducive to the growth of other potential pathogens, leading to infection by a polymicrobial consortium. This consortium is easily perturbed by a (seasonal) temperature decrease, but remains associated with the coral host and can be reactivated with a subsequent seasonal increase in temperature, resulting in a cycle of temperature‐dependent disease emergence.  相似文献   

16.
Diatoms are major primary producers of microbial biomass in the Antarctica. They are found in the water and sea ice. The distribution, abundance of the ice diatoms and their relation to the environmental factors inside and outside the ice have been studied for its special role in the Antarctic Ocean ecology. In this paper we describe the abundance, distribution and composition of diatom assemblages in  相似文献   

17.
18.
In 2007 the EU Commission published the so-called “Blue Book” aimed at developing an Integrated Maritime Policy for the Union. Even though Norway is not an EU member and is usually referred to as a small state, this article shows how the Norwegian government was able to exercise significant influence on EU maritime policy development, positioning itself as one of the key actors. Applying the negotiation theory and tracing the process as it unfolded, this analysis identifies causal relationships leading to increased influence for Norwegian actors—particularly in respect to how issues concerning the Arctic became an integrated part of the policy. The paper concludes that even though the Norwegian actors had a strategic point of departure, utilizing objective advantages to maximize their own utility, their influence may also have been due to competence and sharing of knowledge. The article relies on official documents, but is to a large extent also based on interviews with key EU Commission and Norwegian governmental representatives. On an elevated, substantive analytical level the article contributes to the “small state” research agenda and its interest in how small states in international relations might influence policy outcomes and thrive in the international community.  相似文献   

19.
Fish assemblages were studied in a hypersaline tropical estuary in Northeastern Brazil. A total of 104 species were collected by beach seine during the dry and rainy seasons of 2012. Two families, Atherinopsidae and Gerreidae, were numerically dominant in all zones of the estuary; juveniles of Atherinella brasiliensis, Eucinostomus argenteus, Lile piquitinga, Ulaema lefroyi, Lutjanus analis and Sphoeroides greeleyi contributed 77% of the total catch. The factors that best explained the fish abundance pattern were salinity and depth, which were related to spatial segregation. Species richness was lowest in the upper zone, an area with high salinity and shallow depth. The distinct roles of structurally different habitats (submerged macrophyte beds and mangrove prop‐roots) and the influence of physicochemical conditions in the middle zone of the estuary may influence taxonomic diversity. The middle zone of the estuary is the one most attractive to juveniles of reef species (Lutjanidae and Serranidae). The fish assemblages are clearly dominated by marine estuarine dependent species, highlighting the importance of the ecosystem as a nursery ground for marine species of the Brazilian coast.  相似文献   

20.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号