Domoic acid excretion in dungeness crabs, razor clams and mussels

Domoic acid (DA) is a neurotoxic amino acid produced by several marine algal species of the Pseudo-nitzschia (PN) genus. We studied the elimination of DA from hemolymph after intravascular (IV) injection in razor clams (Siliqua patula), mussels (Mytilus edulis) and Dungeness crabs (Cancer magister). Crabs were also injected with two other organic acids, dichloroacetic acid (DCAA) and kainic acid (KA). For IV dosing, hemolymph was repetitively sampled and DA concentrations measured by HPLC-UV. Toxicokinetic analysis of DA in crabs suggested most of the injected dose remained within hemolymph compartment with little extravascular distribution. This observation is in sharp contrast to results obtained from clams and mussels which exhibited similarly large apparent volumes of distribution despite large differences in overall clearance. These findings suggest fundamentally different storage and elimination processes are occurring for DA between bivalves and crabs.     

地中海东部的早中生代俯冲——土耳其西北部三叠纪榴辉岩提供的证据

地中海东部的早中生代俯冲——土耳其西北部三叠纪榴辉岩提供的证据ＡｒａｌＯｋａｙ等晚古生代古地理再造表明现今地中海东部地区是一辽阔的海域。虽然有地质证据证明这一地区存在过这个古生代海洋——古特提斯海，但是对于这个古特提斯俯冲史的资料是缺乏的。因此，我们...     

用美国地质调查所车载氦探测器勘查铀矿的新发展

美国地质调查所研究成了一种测量He含量的车载质谱仪。该仪器在已知铀矿区作了试验,并在土壤气和水中都发现了He异常。气体样品收集在注射器式取样器里,然后注入到质谱仪中作He分析。仪器以10ppb的灵敏度每天可做100多次分析。在科罗拉多州维尔德郡所进行的详细研究表明,根据土壤气体的He值所编绘的等值线图,能圈定出异常区,同时异常相对矿体沿地下水的下流方向有所偏移。其它研究包括如下地点:科罗拉多州杰弗逊郡舒瓷兹瓦尔德铀山矿,那里He异常可能与地质构造有关;新墨西哥州安布罗西亚湖附近的地区,那里He异常位置与地下水运动有关;周日效应试验结果表明,He的变化甚微,可能与土壤湿度有关。     

First astronomical detection of the cumulene carbon chain molecule H2C6 in TMC-1

The cumulene carbenes are important components of hydrocarbon chemistry in low-mass star-forming cores. Here we report the first astronomical detection of the long-chain cumulene carbene H2C6 in the interstellar cloud TMC-1, from observations of two of its rotational transitions: J(K,K') = 7(1,7) --> 6(1,6) at 18.8 GHz and 8(1,8) --> 7(1,7) at 21.5 GHz, using NASA's Deep Space Network 70 m antenna at Goldstone, California. In addition we also observed the shorter cumulene carbene H2C4 at the same position. The fractional abundance of H2C6 relative to H2 is about 4.7 x 10(-11) and that of H2C4 is about 4.1 x 10(-9). The abundance of H2C6 is in fairly good agreement with gas-phase chemical models for young molecular cloud cores, but the abundance of H2C4 is significantly larger than predicted.     

An operational method for the real-time monitoring of E. coli numbers in bathing waters

The aim of this study was to investigate the potential application of the beta-d-glucuronidase (GLUase) activity measurement for the routine detection and quantification of E. coli in marine bathing waters. GLUase activity was measured as the rate of hydrolysis of 4-methylumbelliferyl-beta-d-glucuronide. Culturable E. coli were quantified by the most probable number (MPN) microplate method. Both methods were applied to a large set of seawater samples. Significant correlation was found between the log of GLUase activity and the log of culturable E. coli. The mean coefficient of variation (CV) of the GLUase activity was less than 15% at concentrations around the current standards of International regulations whereas the CV of the microplate method was around 30%. When samples were stored at 4 degrees C and 20 degrees C, the mean CV of the GLUase activity remained below 15% up to 6 hours after sample collection whereas the range of variation of the microplate method varied between 10 and 50%. We concluded that the GLUase activity is an operational, reproducible, simple, very rapid and low cost method for the real-time enumeration of E. coli in bathing waters and should be preferred to the microplate method. The GLUase activity method should be routinely applied to the rapid enumeration of E. coli in recreational waters and recommendations for its application were suggested to water quality managers.     

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.