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.     

Histopathological biomarkers in estuarine fish species for the assessment of biological effects of contaminants

The increasing emphasis on the assessment and monitoring of estuarine ecosystems has highlighted the need to deploy appropriate biological indices for these locations. Fish diseases and histopathology, with a broad range of causes, are increasingly being used as indicators of environmental stress since they provide a definite biological end-point of historical exposure. This study reports on the histopathological alterations observed in selected organs and tissues of three species of estuarine fish (Platichthys flesus, Pomatoschistus minutus and Zoarces viviparus), captured from four British estuaries (the Tyne, Tees, Mersey and Alde), differently impacted by contaminants, including PAHs. A biannual sampling regime was used to identify the important seasonal variations that occur in terms of the observed biological effects. Inflammatory lesions and hepatocellular fibrillar inclusions attained their highest prevalence in P. flesus captured from the Tyne, Tees and Mersey. The presence of pre-neoplastic and neoplastic toxicopathic lesions was highest in P. flesus captured from these sites, when compared to fish from the Aide reference site. In particular, the prevalence of hepatic foci of cellular alteration (up to 43.3%) and hepatocellular adenoma (up to 10%) were highest in P. flesus captured from the Mersey estuary. Intersex (ovotestis) was only recorded in male P.flesus captured from the Mersey estuary (up to 8.3%) and from male Z. viviparous captured from the Tyne estuary (25%). Pathologies associated with the gill and the kidney were also most prevalent in fish captured from the Tyne, Tees and Mersey estuaries. This study has successfully applied histopathology to an estuarine monitoring program, both for the recording of toxicopathic lesions in the liver and other organs, and for the detection of the endpoint of endocrine disruption, intersex. As such, it provides a powerful integrative tool for the assessment of biological effects of contaminants in these environments.     

Abrupt climate change and transient climates during the Paleogene: a marine perspective

Detailed investigations of high latitude sequences recently collected by the Ocean Drilling Program (ODP) indicate that periods of rapid climate change often culminated in brief transient climates, with more extreme conditions than subsequent long term climates. Two examples of such events have been identified in the Paleogene; the first in latest Paleocene time in the middle of a warming trend that began several million years earlier: the second in earliest Oligocene time near the end of a Middle Eocene to Late Oligocene global cooling trend. Superimposed on the earlier event was a sudden and extreme warming of both high latitude sea surface and deep ocean waters. Imbedded in the latter transition was an abrupt decline in high latitude temperatures and the brief appearance of a full size continental ice-sheet on Antarctica. In both cases the climate extremes were not stable, lasting for less than a few hundred thousand years, indicating a temporary or transient climate state. Geochemical and sedimentological evidence suggest that both Paleogene climate events were accompanied by reorganizations in ocean circulation, and major perturbations in marine productivity and the global carbon cycle. The Paleocene-Eocene thermal maximum was marked by reduced oceanic turnover and decreases in global delta 13C and in marine productivity, while the Early Oligocene glacial maximum was accompanied by intensification of deep ocean circulation and elevated delta 13C and productivity. It has been suggested that sudden changes in climate and/or ocean circulation might occur as a result of gradual forcing as certain physical thresholds are exceeded. We investigate the possibility that sudden reorganizations in ocean and/or atmosphere circulation during these abrupt transitions generated short-term positive feedbacks that briefly sustained these transient climatic states.     

我国第一个24位数字化无线遥测地震台网──广州台网通过验收

由广东省人民政府、珠江三角洲地区各市政府和国家地震局共同投资兴建的广州数字化遥测地震台网（以下简称广州台网），1985年开始筹建，1989年开始设备引进，经过安装调试、信道改造、系统完善和试验运行等多个环节，作了大量技术工作，现已完成了全部建设过程，达到了组织验收要求。1996年12月17～20日，由国家地震局和广东省人民政府联合组成的以陈运泰院士为组长的验收组对广州台网进行了测试和验收。验收组听取和审阅了广州台网技术人员作的技术、考核运行和工作报告，以及测试组作的测试报告，实地检查了台网技术系统的运行情况并进行…     

三水发生M_L3.7和4.2级地震

1997年9月23日11时20分，广东省三水市南边镇（北纬23．2°，东经113°），发生ML3，7级地震，9月26日13时27分，再发生ML4．2级（北纬23．3°，东经113°）地震一次。这是建国以来珠三角地区发生的最大一次地震。今年投入正式观测的广州遥测地震台网在这两次地震速报中发挥了重要的作用。两次地震分别只用5分和9分钟就准确地测定了参数作出速报。我局同时将地震情况上报省政府和国家地震局，达到了国家地震局要求的大中城市附近发生强有感地震后匕分钟内作出速报的要求。这两次地震佛山市范围普遍有感，广州市区部分居民也有感，特别是9…     

通用接口总线和地电自动测量系统(GP—IB和地电ATS)

微处理机(μp)和微型计算机(μc)近年来获得了迅猛发展,应用领域不断扩大.其中一个重要的领域是数字仪表。目前生产的数字仪表内部都装有一部或多部μp/μc.它们大有取代传统的模似仪表的趋势。数字仪表发展如此迅速的驱动力则是它的高精度,高速度,高稳定性,使用方便,应用广泛同时也因为各种各样的通用数字仪表可以很快的组成为实现各种不同目的,任务、要求的自动测试系统ATS(Automatic Test System).     

广东地区现代构造应力场的模拟计算

运用已知的断裂边界条件、区内震源机制解、小震应力降和环境应力场等资料作为基本数据,建立地质模型和计算模型,用有限元方法模拟计算了华南地区的现代地壳构造应力场.初步得到了本区的外力作用方式、断裂活动情况、应力集中状况、区应力场分布状况,为划分地震危险区段提供了依据.     

1997年9月三水3.7和4.4级地震特征初析

对１９９７年９月２３日和２６日两次三水有感地震的特征进行了初步分析,认为这两次地震具有震前和震后地震活动水平低、面波发育和低震级高烈度等特性;震区的主压应力为北北西方向,两震的受力方向基本一致,但断层面解明显不同。     

Testing alternative ground water models using cross-validation and other methods

Many methods can be used to test alternative ground water models. Of concern in this work are methods able to (1) rank alternative models (also called model discrimination) and (2) identify observations important to parameter estimates and predictions (equivalent to the purpose served by some types of sensitivity analysis). Some of the measures investigated are computationally efficient; others are computationally demanding. The latter are generally needed to account for model nonlinearity. The efficient model discrimination methods investigated include the information criteria: the corrected Akaike information criterion, Bayesian information criterion, and generalized cross-validation. The efficient sensitivity analysis measures used are dimensionless scaled sensitivity (DSS), composite scaled sensitivity, and parameter correlation coefficient (PCC); the other statistics are DFBETAS, Cook's D, and observation-prediction statistic. Acronyms are explained in the introduction. Cross-validation (CV) is a computationally intensive nonlinear method that is used for both model discrimination and sensitivity analysis. The methods are tested using up to five alternative parsimoniously constructed models of the ground water system of the Maggia Valley in southern Switzerland. The alternative models differ in their representation of hydraulic conductivity. A new method for graphically representing CV and sensitivity analysis results for complex models is presented and used to evaluate the utility of the efficient statistics. The results indicate that for model selection, the information criteria produce similar results at much smaller computational cost than CV. For identifying important observations, the only obviously inferior linear measure is DSS; the poor performance was expected because DSS does not include the effects of parameter correlation and PCC reveals large parameter correlations.