目的筛选试验鱼适宜急性毒性试验的发育期。方法将诸氏鲻虾虎鱼早期仔鱼、中期仔鱼、晚期仔鱼、稚鱼、幼鱼及成鱼暴露于一定浓度的钻井液中,比较钻井液对不同发育期诸氏鲻虾虎鱼的急性毒性。结果早期仔鱼48 h LC50为157 mg/L,中期仔鱼48 h LC50大于500 mg/L;中期仔鱼96 h LC50为79 mg/L,晚期仔鱼96h LC50为625 mg/L,稚鱼、幼鱼、成鱼96 h LC50显著大于500 mg/L;卤虫无节幼体96 h LC50为105 mg/L;不同发育期诸氏鲻虾虎鱼对钻井液的敏感性顺序为:早期仔鱼〉中期仔鱼〉晚期仔鱼〉稚、幼、成鱼。结论诸氏鲻虾虎鱼的早期仔鱼适用于海洋污染物急性毒性评价。 相似文献
Most textbook knowledge on ventricular repolarization is based on animal data rather than on data from the in vivo human heart. Yet, these data have been extrapolated to the human heart, often without an appropriate caveat. Here, we review multiple aspects of repolarization, from basic membrane currents to cellular aspects including extrinsic factors such as the effects of the sympathetic nervous system. We critically discuss some mechanistic aspects of the genesis of the T-wave of the ECG in the human heart.
Obviously, the T-wave results from the summation of repolarization all over the heart. The T-wave in a local electrogram ideally reflects local repolarization. The repolarization moment is composed of the moment of local activation plus local action potential duration (APD) at 90% repolarization (APD90). The duration of the latter largely depends on the balance between L-type Ca2+ current and the delayed rectifier currents. Generally speaking, there is an inverse relationship between local activation time and local APD90, leading to less dispersion in repolarization moments than in activation moments or in APD90. In transmural direction, the time needed for activation from endocardium toward epicardium has been considered to be overcompensated by shorter APD90 at the epicardium, leading to the earliest repolarization at the subepicardium. In addition, mid-myocardial cells would display the latest repolarization moments. The sparse human data available, however, do not show any transmural dispersion in repolarization moment. Also, the effect of adrenergic stimulation on APD90 has been studied mainly in animals. Again, sparse human data suggest that the effect of adrenergic stimulation is different in the human heart compared to many other mammalian hearts. Finally, aspects of the long QT syndrome are discussed, because this intrinsic genetic disease results from repolarization disorders with extrinsic aspects. 相似文献
Protein expression depends significantly on the stability, translation efficiency and localization of mRNA. These qualities are largely dictated by the RNA-binding proteins associated with an mRNA. Here, we report a method to visualize and localize RNA-protein interactions in living mammalian cells. Using this method, we found that the fragile X mental retardation protein (FMRP) isoform 18 and the human zipcode-binding protein 1 ortholog IMP1, an RNA transport factor, were present on common mRNAs. These interactions occurred predominantly in the cytoplasm, in granular structures. In addition, FMRP and IMP1 interacted independently of RNA. Tethering of FMRP to an mRNA caused IMP1 to be recruited to the same mRNA and resulted in granule formation. The intimate association of FMRP and IMP1 suggests a link between mRNA transport and translational repression in mammalian cells. 相似文献
We hypothesized that host antiviral genes induced by type I interferons might affect the natural course of severe acute respiratory syndrome (SARS). We analyzed single nucleotide polymorphisms (SNPs) of 2',5'-oligoadenylate synthetase 1 (OAS-1), myxovirus resistance-A (MxA), and double-stranded RNA-dependent protein kinase in 44 Vietnamese SARS patients with 103 controls. The G-allele of non-synonymous A/G SNP in exon 3 of OAS-1 gene showed association with SARS (p=0.0090). The G-allele in exon 3 of OAS-1 and the one in exon 6 were in strong linkage disequilibrium and both of them were associated with SARS infection. The GG genotype and G-allele of G/T SNP at position -88 in the MxA gene promoter were found more frequently in hypoxemic group than in non-hypoxemic group of SARS (p=0.0195). Our findings suggest that polymorphisms of two IFN-inducible genes OAS-1 and MxA might affect susceptibility to the disease and progression of SARS at each level. 相似文献
Lung‐cancer mortality (LCM) is elevated in underground miners who chronically inhaled the mutagenic, cytotoxic α‐decay products of radon gas. Epidemiologie studies of LCM rates vs. residential‐radon concentration levels are generally considered inconclusive. However, Cohen (Health Physics 68, 157–174, 1995) has hypothesized that data on LCM vs. residential radon concentrations at the U.S. county level are clearly inconsistent with a linear no‐threshold (LN) dose‐response model, and rather are consistent with threshold or hormesis model. Cohen's hypothesis has been criticized as “ecological fallacy,”; particularly because LN (but not threshold or hormesis) models are generally considered biologically plausible for agents like α radiation that damage DNA in linear proportion to dose. To assess the biological plausibility of Cohen's hypothesis, a preliminary study was made of whether a biologically realistic, cytodynamic 2‐stage (CD2) cancer model can provide a good, joint fit to Cohen's set of U.S. county data as well as to underground‐miner data. The CD2 model used adapts a widely applied, mechanistic, 2‐stage stochastic model of carcinogenesis to realistically account for interrelated cell killing and mutation (both assumed to have a LN dose‐response), cell turnover, and incomplete exposure of stem cells. A CD2 fit was obtained to combined summary data on LCM vs. radon‐exposure in white males in 1, 601 U.S. counties (from Cohen) and in white male Colorado Plateau (CP) uranium miners (from the National Research Council's “BEIRIV”; report). The CD2 fit is shown to: (i) be consistent with the combined data; (ii) have parameter values all consistent with biological data; and (iii) predict inverse dose‐rate‐effects data for CP and other radon‐exposed miners, despite the fact that optimization had not involved any of these dose‐rate data. The latter data were not predicted by a simplified CD2 model in which all stem cells were presumed to be exposed. It is concluded that this study provides preliminary evidence that Cohen's hypothesis is biologically plausible. 相似文献
Idiopathic short QT syndrome (SQTS) is a recently identified, genetically heterogeneous condition characterised by abbreviated QT intervals and an increased susceptibility to arrhythmia and sudden death. This simulation study identifies mechanisms by which cellular electrophysiological changes in the SQT2 (slow delayed rectifier, IKs, -linked) SQTS variant increases arrhythmia risk. The channel kinetics of the V307L mutation of the KCNQ1 subunit of the IKs channel were incorporated into human ventricular action potential (AP) models and into 1D and 2D transmural tissue simulations. Incorporating the V307L mutation into simulations reproduced defining features of the SQTS: abbreviation of the QT interval, and increases in T wave amplitude and Tpeak–Tend duration. In the single-cell model, the V307L mutation abbreviated ventricular cell AP duration at 90% repolarisation (APD90) and increased the maximal transmural voltage heterogeneity (δV) during APs; this resulted in augmented transmural heterogeneity of APD90 and of the effective refractory period (ERP). In the intact tissue model, the vulnerable window for unidirectional conduction block was also increased. In 2D tissue the V307L mutation facilitated and maintained reentrant excitation. Thus, in SQT2 increases in transmural heterogeneity of APD, δV, ERP and an increased vulnerable window for unidirectional conduction block generate an electrical substrate favourable to reentrant arrhythmia. 相似文献
The genusPittosporum includes about 160 species. Four species ofPittosporum occur in the Bonin Islands, and all of these are endemic to the islands. Electrophoretic studies of the four endemic species,P. tobira, from the Japanese mainland, andP. lutchuense var.denudatum from the Ryukyu Islands, were used to determine the origin and speciation pattern of the endemic species.
259 individuals were sampled from ten populations. Twenty loci in nine enzyme systems were resolved and used to calculate
the gene frequencies for each population. A low genetic diversity was observed in three of the Bonin Island species, as is
reported for other oceanic island plants. The exception,P. boninense, has the largest population size and widest distribution. A dendrogram generated by the UPGMA method shows two clusters.
One consists of only the Bonin endemics, suggesting a monophyletic origin for these species. 相似文献
The increasing use of digital technologies such as mobile phones has led to major health concerns about the effects of non-ionizing pulsed radiation exposure. We believe that the health implications of exposure to radiation cannot be fully understood without establishing the molecular mechanisms of biological effects of pulsed microwaves. We aim to establish methods for studying the molecular mechanisms of protein structural and energetic changes occurring due to external stresses related to non-ionizing radiation by using a combination of experimental and theoretical approaches. In this paper, we present the results from our fully atomistic simulation study of chemical and thermal stress response of a prototype protein, insulin. We performed a series of molecular dynamics simulations of insulin in solution under equilibrium conditions, under chemical stress (imitated by reducing the disulfide bonds in the protein molecule), and under short-lived thermal stress (imitated by increasing simulation temperature for up to 2 ns). The resultant protein conformational behaviour was analysed for various properties with the aim of establishing analysis routines for classification of protein unfolding pathways and associated molecular mechanisms.Submitted as a record of the 2002 Australian Biophysical Society meeting 相似文献