Effects of beta-naphthoflavone on hepatic biotransformation and glutathione biosynthesis in largemouth bass (Micropterus salmoides)

We are investigating the effects of in vivo exposure of prototypical enzyme inducing agents on hepatic biotransformation enzyme expression in largemouth bass (Micropterus salmoides), a predatory game fish found throughout the United States and Canada. The current study targeted those genes involved in biotransformation and oxidative stress that may be regulated by Ah-receptor-dependent pathways. Exposure of bass to beta-naphthoflavone (beta-NF, 66 mg/kg, i.p.) elicited a 7-9-fold increase in hepatic microsomal cytochrome P4501A-dependent ethoxyresorufin O-deethylase (EROD) activities, but did not affect cytosolic GST catalytic activities toward 1-chloro-2,4-dinitrobenzene (CDNB) or 5-androstene-3,17-dione (ADI). Glutathione S-transferase A (GST-A) mRNA expression exhibited a transient, but non-significant increase following exposure to beta-NF, and generally tracked the minimal changes observed in GST-CDNB activities. Expression of the mRNA encoding glutamate-cysteine ligase catalytic subunit (GCLC), the rate-limiting enzyme in glutathione (GSH) biosynthesis, was increased 1.7-fold by beta-NF. Changes in GCLC mRNA expression were paralleled by increases in intracellular GSH. In summary, largemouth bass hepatic CYP1A-dependent and GSH biosynthetic pathways, and to a lesser extent GST, are responsive to exposure to beta-NF.     

源于深部韧性剪切带中氧化变质作用的金：初步模式

石英-碳酸盐金矿床赋存在剪切带中脆性-韧性转换处或在其上。据知有些最大的矿床就是沿着长期活动的主横推剪切带形成的。由于岩石的稠度随深度而降低,这种类型的剪切带向下在韧性态中加宽,有的韧性剪切带在麻粒岩相变质作用的深度宽达40km。韧性剪切带是可渗透的,并由于可渗性是沿微裂隙发育,所以水流遍布,为广泛的化学反应提供了机会。反应速率随剪切加热、矿物变形诱发的应力梯度、和粒度的减小而增加。因为压力在剪切带的脆性部分降低,水流往往是向上的。假设韧性剪切带为楔形体,穿过下地壳的大量流体就会聚集在脆性-韧性带的转换处。因此,如果在穿过下地壳的流体运动期间存在着选择迁移元素的作用,那么这些元素也可聚集在这个转换处。石英-碳酸盐矿脉最恒定的特征之一是碳酸盐蚀变,它可从矿床的中部向外延伸数公里。这里的~(13)C特征与幔源CO_2一致。可能来源于地幔并向上运动的CO_2气化物与角闪岩相岩石脱水成为麻粒岩及伴随的大离子亲岩元素的衰竭有关。有大量资料表明下地壳被CO_2改变的情况发生在主剪切带。在深部CO_2的流动仅发生在比石墨稳定性所需环境更为氧化的条件下。这种环境利于金的溶解,因为:(a) 使Au°氧化为Au~+;(b) 从岩石中溶出的硫化物和Au+络合。近期工作已经证明有些主要的太古代金矿床的成矿物质来源干相对氧化的流体中。初步模式的概述至少要考虑某些石英-碳酸盐金矿床的成因。渗入到深部韧性剪切带的CO_2使角闪岩相岩石脱水。产生了相对氧化的CO_2—H_2O流体,这个流体使来自下地壳的大量硫化物和金溶解。金被向上带到变窄的剪切处,聚集并沉淀在脆性-韧性转换处。     

Effects of mining wastes on a seagrass ecosystem: metal accumulation and bioavailability, seagrass dynamics and associated community structure

Two different Cymodocea nodosa (Ucria) Ascherson beds growing in mining-contaminated sediments were compared with two reference beds in the Mar Menor coastal lagoon. The accumulation of Zn, Pb and Cd in different fractions of the plant, the sediment parameters that regulate the availability of metals, the seabed structure and dynamics of each seagrass bed and its associated macroinvertebrate community were studied. C. nodosa accumulates metals from the sediments and reflects their bioavailability for this seagrass. At each station, the metal content of the rhizomes was lower than that of leaves and roots. The concentration of acid-volatile sulfides does not seem to influence the availability of metals to the seagrass, possibly due to oxygen transport to underground tissues. The highest metal concentration in all the contaminated stations was found in the leaf-biofilm, due to the formation of complexes between metals and the extracellular polymeric substances that form the biofilm. All the seagrass beds were seen to be undergoing expansion, those growing in contaminated sediments accumulating great quantities of metals and showing highest photosynthetic leaf surface area and highest leaf biomass. However, these structural parameters were not seen to be responsible for the differences in the faunal composition observed between contaminated and reference beds. Moreover, the multivariate analysis identified the metal content of leaves, biofilm and sediments as important variables that may be responsible for these differences in faunal composition. In this study we have demonstrated that both the seagrass C. nodosa and the biofilm on the plant leaves may be used as environmental tools in the Mar Menor lagoon. The former is an useful indicator of sediment contamination, whereas the latter seems to be a good sentinel of water quality.