Electron microscopy documenting the cellular metabolic fate of Zn IONS∗

In vertebrates and invertebrates Zn exist as complexed compounds with metallothioneins. However, its cellular level effects and metabolic fates are scantly documented. In the elucidation of this fact, EM results on hepatic cellular alterations in fish under lethal dose exposure at 4.0 ppm over a week is illustrated.

A large number of lysosomes in hepatic cells prevailed on exposure to Zn in its sulfate form. Evidently, due to metal compound stress and cellular damage lysosomal activity is augmented. The lysosomes harboured digestible material, presumably the aforementioned substrates. Contrary to it, fat droplets prevailed while glycogen depletion is noticeable. Unlike the effects of Hg, the nuclei were normal with granular chromatin and prominent nucleoli. However, the mitochondria contained some small intramitochondrial bodies. Similar to the effects of Hg, the cell membrane remained intact.

In vivo enzymatic studies indicated augmentation in catalase, acid‐ and alkaline‐phosphatases, while glucose‐6‐phosphatase is inhibited. However, only alkaline‐ and glucose‐6‐phosphatases are inhibited under in vitro conditions.

Thus, it is evident that Zn enhances cellular bioenergetic requirements culminating in glycogen depletion owing to stress, concomitantly envisaging inhibition of oxidative phosphorylation in the electron transport system.     

Preliminary toxicity evaluation of water from rice fields using cost‐effective microbiotests

A study was performed in a Protected Area (Natural Reserve of Sado Estuary) in 1996, to evaluate the acute toxicity for aquatic life of surface water from rice fields treated with pesticides, particularly with molinate and quinclorac. As a preliminary assessment, the following rapid toxicity tests were used: “Rotoxkit F”;, “Thamnotoxkit F”; and the recently introduced “Daphtoxkit F magna”; and “Algaltoxkit F”;. Water samples were collected from: a water source for irrigating the rice fields, two rice plots, a drainage channel and from Sado river in which the water is discharged. The results showed that samples from the rice plot treated with molinate were more toxic than those obtained from rice plot treated with quinclorac. Water samples from the river were the most toxic, causing 100% of immobility in all organisms and a substantial inhibition in the algal growth. Water collected from the drainage channel in late July, was also found to be quite toxic. The results obtained until now indicate that some characteristics of these microbiotests, like their rapidity, simplicity and relatively low cost, make them a practical tool to evaluate acute effects of pesticides in freshwater ecosystems. They may also contribute to suggest some changes in pesticides use to promote agricultural practices with lower impact to aquatic life.     

Bioaccumulation and toxic effects of copper on growth and oxygen consumption by the postlarvae of Penaeus indicus

The aim of this study was to assess the toxic impact of copper on postlarvae (PL) of the penaeid shrimp Penaeus indicus. Tolerance, growth, oxygen consumption and metal accumulation were investigated in these PL on exposure to copper. Tolerance studies were conducted for 96 h to assess the tolerance limits of P. indicus PL exposed to different concentrations of copper using static renewal bioassay tests. Using the Probit method, the regression equation was calculated as Y=0.4899+2.3562 X, with a correlation coefficient of 0.9707. The 96 h LC₅₀ was 0.8204 ppm. The effect of sublethal (one-fifth of 96 h LC₅₀) copper on PL for short- and long-term exposures revealed a significant (p<0.05) decrease in the rate of oxygen consumption, metabolic rate, mean length, wet and dry weight of the exposed PL over their respective controls which can be attributed to a gradual and time-dependent accumulation of the metal, as noticed in the exposed PL through accumulation studies. Overall, the data suggest that on chronic exposure even sublethal concentrations of copper can reduce the metabolic rate and growth in P. indicus PL. This is perhaps the first attempt to use the wild P. indicus PL as a bioindicator of copper toxicity.     

Protein Metabolic Response to Carbon Tetrachloride in A Freshwater Fish,Sarotherodon Mossambicus

Exposure of a freshwater teleost, Sarotherodon mossambicus, to a sublethal concentration (26 ppm) of carbon tetrachloride for periods up to 30 days led to significant changes in the soluble protein fractions (albumin and globulins) and free amino acid content. the decrease in total protein content was greater in liver than in muscle. the protein loss was expected due to the impairement of protein synthetic activity during stress conditions.     

印染废水处理过程及排放水对草履虫遗传毒性评价

草履虫作为指示生物评估印染废水处理过程及排放水的毒性效应。急性毒性结果显示,原水、厌氧工段印染废水、好氧工段印染废水对草履虫的半数致死浓度(24h-LC₅₀)分别为54%、41%、98%;遗传毒性结果显示,印染废水原水、经处理的排放水在6.25%、12.25%稀释梯度下对草履虫造成的DNA损伤较对照组呈显著升高(p<0.01),而排放水对草履虫的DNA损伤较原水无显著性差异;草履虫增殖速率结果显示,印染废水排放水50%稀释梯度下对草履虫增殖速率有抑制作用。暴露于印染废水排放水中10%的草履虫其游动行为发生改变。以上结果表明,印染废水在经过处理后,理化指标均达到国家印染废水行业排放标准,但排放水仍对草履虫产生急性毒性,且遗传毒性较原水没有显著降低。水生生物毒性测试能有效补充理化指标评价,为印染废水行业全面达标排放提供依据。     

Ag（Ⅰ）对大肠杆菌抑制作用影响因素的分析

通过测定在各种条件下Ag（Ⅰ）对大肠杆菌Escherichia coli的生长的抑制作用,系统分析了各参数对Ag（Ⅰ）毒性的影响。结果表明：好氧、厌氧状态下,Ag（Ⅰ）对E.coli的抑制能力基本相同;在LB培养基、氨基酸基本培养基和标准基本培养基中Ag（Ⅰ）开始抑制E.coli生长的浓度差异较大,分别为10、0.5、0.1μmol/L;LB组分中的酵母粉的加入完全消除了Ag（I）对E.coli的抑制作用;此外,菌体浓度越高抑制其生长所需的Ag（Ⅰ）浓度也越高。因此Ag（I）对E.coli生长的抑制作用与氧化应激无关,而与培养基种类、培养基组分及菌体浓度高度相关。     

环境雌激素o,p′-DDT和抗雌激素氟维司群对斑马鱼胚胎的复合效应

为探究雌激素与抗雌激素的复合效应,将斑马鱼(Danio rerio)的胚胎暴露于o,p′-DDT和氟维司群2种典型的环境内分泌干扰物中,考察胚胎孵化率、孵化时间和总畸形率,并用实时荧光定量PCR技术检测Vtg1、Vtg2和ERα等雌激素效应相关基因的mRNA转录水平.结果显示,与单一化合物的暴露相比,o,p′-DDT和...     

全氟辛烷磺酸盐(PFOS)替代品对中华蜜蜂的毒性

选用中国蜂种中华蜜蜂工蜂作为受试生物,建立其环境危害评价毒性测试方法,用所建立的方法对全氟辛烷磺酸盐(PFOS)替代品进行了接触急性毒性及经口急性毒性风险评价,并比较了"小烧杯法"和"饲喂管法"两种经口毒性方法的优缺点及对毒性结果的影响。研究结果表明,"小烧杯法"实验中C4织物三防整理剂对中华蜜蜂的24h-LC50为1435mg·L~(-1),48h-LC_(50)为284.67mg·L~(-1);其余替代品在限度实验均未出现蜜蜂死亡,4种PFOS替代品对中华蜜蜂的接触毒性及经口毒性均为低毒,但"小烧杯法"测得的经口毒性结果比"饲喂管法"高。     

金属污染物对神经系统损害及毒性机制研究进展

神经系统与生物体其他系统联系密切,共同维持机体正常的结构和功能。环境中的金属污染物可通过多种途径进入生物体,干扰幼年或成年动物神经系统的发育和功能,其损害机制是目前研究的热点。本文系统地总结了汞、铅和铝等金属污染物对神经系统的损害作用,着重在细胞、分子和基因水平上阐述了金属对神经系统的毒性机制,在此基础上分析了当前研究的不足之处和发展趋势,并对今后的研究方向进行了展望。