Aluminum accumulation in a lotic mayfly at low pH--a laboratory study

The authors experimentally studied the occurrence of aluminum (Al) accumulation in nymphs of the mayfly Heptagenia sulphurea at low pH (4.5). Nymphs were exposed to two Al concentrations (0.2 and 2 mg inorganic Al liter-1), and two exposure times (2 and 4 weeks), the longer time period also including a molting phase. The major part of the Al was deposited on/in the exuviae of the nymphs, as Al determination in nymphs showed a 70% decrease in Al content after molting. When nymphs were exposed for two instar periods, with a molt in between. Al content almost doubled (2.34 mg Al g-1 dry wt) compared with that of a one-instar treatment (1.24 mg Al g-1 dry wt). This indicated that Al also accumulated within the mayfly nymphs. Determination of Al in emerged adults confirmed that most of the metal was deposited externally on the nymphs. No clear indications of Al accumulation were found in this short-term experiment. The implications for food-web accumulation of Al are that internally accumulated Al may be transferred to terrestrial predators by mayflies and other aquatic insects that leave their final exuvium in the water. However, aquatic insects that make their final molt in the terrestrial environment, and thereby bring adsorbed Al out of the water are more likely vectors.     

低剂量亚慢性砷染毒对雄性大鼠生殖功能及子代的影响

目的探讨低剂量砷染毒对雄性大鼠生殖毒性及胚胎发育毒性的影响。方法健康普通级雄性sD大鼠48只,按体质量随机分为4组,分别饮用含亚砷酸钠0（蒸馏水组）、0．01（低剂量组）、0．05（中剂量组）和0．25mg／L（高剂量组）的水。染毒12周后,与正常成年雌性大鼠按1：2合笼,确定雌鼠怀孕后,处死雄鼠取其附睾丸,观察雄性大鼠精子畸形并用原子荧光谱法测定其血砷和精液砷浓度。于妊娠第20天处死雌鼠,观察雌雄交配受孕情况、受精卵着床数、活胎数、死胎数、吸收胎数及胚胎的生长发育情况。结果染毒12周后,低、中、高剂量组与蒸馏水组大鼠的体重分别为（347．6±18．7）、（308．3±19．2）、（301．4±17．4）和（316．7±17．7）g,低剂量组体重较蒸馏水组增加,高剂量组体重较蒸馏水组降低,差异均有统计学意义;精子数量分别为（9．7±0．8）、（5．5±0．5）、（4．3±0．4）和（9．3±0．9）×10^6／ml,活精率分别为（65．4±7．2）％、（41．3±6．9）％、（37．9±4．6）％和（63．8±8．2）％,中高剂量组较蒸馏水组降低,差异有统计学意义;精子畸形率和死胎／吸收胎发生比例分别为（9．1±4．4）％、（14．0±3．9）％、（21．4±5．9）％、（9．3±2．5）％和1．7％、4．2％、7．3％、0．8％,中和高剂量组较蒸馏水组增加,差异有统计学意义。结论0．01mg／L亚砷酸钠染毒对大鼠生殖功能未见明显的毒性作用;0．05mg／L及以上浓度亚砷酸钠亚慢性染毒12周可对雄性大鼠产生生殖毒性,并对胚胎有一定的致畸作用。     

膳食营养素对砷毒性的影响

环境砷暴露是一个世界范围内的公共卫生问题,长期接触无机砷与心血管疾病、糖尿病以及恶性肿瘤等疾病关系密切。膳食结构的不同以及某些特定营养素的摄入对砷的致病效应可能产生重要影响。本文概述了膳食营养素对砷毒性的影响,为后续砷毒性研究以及通过营养干预来降低与砷有关的疾病风险提供参考。     

Lethal and sublethal effects of low dissolved oxygen condition on two aquatic invertebrates, Chironomus tentans and Hyalella azteca

Low dissolved oxygen (DO) conditions occur frequently during sediment toxicity testing, with potentially adverse effects on test organisms. The present study addressed the current lack of good information regarding low DO thresholds for toxicity tests using two common test species, juvenile Hyalella azteca and Chironomus tentans larvae. Results indicated that H. azteca was less tolerant of hypoxia than C. tentans. The 10-d highest- and no-observed-effect concentrations (HOEC and NOEC, respectively) for H. azteca were 1.2 +/- 0.1 and 2.9 +/- 0.1 mg/L DO, respectively. The 10-d NOEC for C. tentans was 1.2 +/- 0.1 mg/L DO, the lowest test concentration. Mortality was the predominant response of H. azteca to low DO exposure, with changes in growth and positioning behavior only evident at lethal DO concentrations. Although exposure to 1.2 +/- 0.1 mg/L DO for 10 d did not affect C. tentans survival or growth, significant behavioral changes were evident at 2.0 +/- 0.1 mg/L DO or less. Overall, the present results indicate that the North American guidelines for low DO thresholds during 10-d toxicity tests seem reasonable for juvenile H. azteca. However, the Environment Canada Guideline (3.4 mg/L DO at 23 degrees C) may be considered to be conservative for 10-d toxicity testing with C. tentans if only short-term effects on survival and growth are considered.     

Effects of low protein diets or feed restriction on rat lung glutathione and oxygen toxicity

Male rats weighing 200-250 g were fed a 25% casein diet in restricted amounts or ad libitum or one of two low protein diets (3 and 0% casein) ad libitum. Decreased tolerance to hyperoxic stress was observed only in the rats fed low protein diets. These animals had a median death time of 49-50 h compared to 58-69 h for feed-restricted or normal control groups. Death was due to accelerated development of lung edema. Changes in total lung levels of glutathione reductase, glucose-6-phosphate dehydrogenase or catalase did not correlate with oxygen sensitivity. Lung glutathione levels were related to the amount of sulfur-containing amino acids in the diet and were depressed in the feed-restricted as well as the protein-restricted groups. However, feed restriction alone did not enhance oxygen toxicity. We conclude that a decrease in lung glutathione may be partially responsible for the increased oxygen sensitivity in the protein-deficient rats, but that other factors are necessary for explanation of the relative oxygen tolerance of the feed-restricted animals with reduced levels of glutathione in the lung.     

Assessment of occupational exposure to inorganic arsenic based on urinary concentrations and speciation of arsenic

An analytical speciation method, capable of separating inorganic arsenic (As (V), As (III] and its methylated metabolites (MMAA, DMAA) from common, inert, dietary organoarsenicals, was applied to the determination of arsenic in urine from a variety of workers occupationally exposed to inorganic arsenic compounds. Mean urinary arsenic (As (V) + As (III) + MMAA + DMAA) concentrations ranged from 4.4 micrograms/g creatinine for controls to less than 10 micrograms/g for those in the electronics industry, 47.9 micrograms/g for timber treatment workers applying arsenical wood preservatives, 79.4 micrograms/g for a group of glassworkers using arsenic trioxide, and 245 micrograms/g for chemical workers engaged in manufacturing and handling inorganic arsenicals. The maximum recorded concentration was 956 micrograms/g. For the most exposed groups, the ranges in the average urinary arsenic speciation pattern were 1-6% As (V), 11-14% As (III), 14-18% MMAA, and 63-70% DMAA. The highly raised urinary arsenic concentrations for the chemical workers, in particular, and some glassworkers are shown to correspond to possible atmospheric concentrations in the workplace and intakes in excess of, or close to, recommended and statutory limits and those associated with inorganic arsenic related diseases.     

Effects of salinity and chemical speciation on cadmium accumulation and toxicity to two mysid species

The estuarine environment is characterized by frequent fluctuations in salinity. Consequently, organisms used for environmental monitoring of estuaries must be euryhaline so that their laboratory responses to chemical pollutants are measured under the full range of salinity exposures experienced in the field. Neomysis integer and Praunus flexuosus are two potential candidates for use in environmental monitoring of European estuaries. The present study assesses the effects of salinity on survival, trace metal accumulation, and toxicity to these two mysid species. Neomysis integer was more euryhaline, showing 100% survival at 1 to 40@1000 compared with P. flexuosus, which showed 100% survival at salinities of 10 to 40@1000. Toxicity of the free cadmium ion to both species was unaffected by salinity, and 96-h LC50s ranged from 4.8 to 15 micrograms Cd2+/L for N. integer and from 12.3 to 16 micrograms Cd2+/L for P. flexuosus. The 7-d LC50s ranged from 1.0 to 4.2 and 4.8 to 5.3 micrograms Cd2+/L for N. integer and P. flexuosus, respectively. No effect of exposure salinity was found on cadmium body burdens of mysids exposed for 7 d to 0.5 and 1.0 microgram Cd2+/L. The results are discussed in terms of possible effects of osmoregulatory mechanisms on trace metal uptake, accumulation, and toxicity.     

Assessment of occupational exposure to inorganic arsenic based on urinary concentrations and speciation of arsenic.

An analytical speciation method, capable of separating inorganic arsenic (As (V), As (III] and its methylated metabolites (MMAA, DMAA) from common, inert, dietary organoarsenicals, was applied to the determination of arsenic in urine from a variety of workers occupationally exposed to inorganic arsenic compounds. Mean urinary arsenic (As (V) + As (III) + MMAA + DMAA) concentrations ranged from 4.4 micrograms/g creatinine for controls to less than 10 micrograms/g for those in the electronics industry, 47.9 micrograms/g for timber treatment workers applying arsenical wood preservatives, 79.4 micrograms/g for a group of glassworkers using arsenic trioxide, and 245 micrograms/g for chemical workers engaged in manufacturing and handling inorganic arsenicals. The maximum recorded concentration was 956 micrograms/g. For the most exposed groups, the ranges in the average urinary arsenic speciation pattern were 1-6% As (V), 11-14% As (III), 14-18% MMAA, and 63-70% DMAA. The highly raised urinary arsenic concentrations for the chemical workers, in particular, and some glassworkers are shown to correspond to possible atmospheric concentrations in the workplace and intakes in excess of, or close to, recommended and statutory limits and those associated with inorganic arsenic related diseases.     

砷汞对小鼠生殖毒性的研究

用小鼠卵母细胞体外培养、体外受精的方法研究了 Hg Cl2 、As2 O3 对小鼠卵母细胞成熟和体外受精等的影响。结果 :Hg Cl2 、As2 O3 对生发泡破裂没有影响 ,但可以抑制卵母细胞第一极体的释放 ,影响卵母细胞的存活率并可降低体外受精的频率 ,对体内卵母细胞生发泡破裂无影响 ,但是可以显著抑制体外培养卵母细胞的生发泡破裂。结论 :本实验结果提示 ,育龄妇女吸收了 Hg Cl2 、As2 O3 后 ,可以损伤卵母细胞的成熟过程 ,降低其生育力和生殖能力 ,甚至导致不孕。     

Syngerism between dissolved oxygen and cadmium toxicity in five species of aquatic insects.

Continuous-flow bioassays were employed to determine the relationship between dissolved oxygen and cadmium upon five species of aquatic insects, as measured by survival and the amount of cadmium found within the insect. Results indicate the toxicity of cadmium increases as the dissolved oxygen concentration increases. This may be explained by an observed increase in the amount of cadmium found in the insect as the dissolved oxygen concentration increases. Oxygen consumption has been reported to increase as the dissolved oxygen concentration increases (Petty, 1967; Ericksen, 1963; Fox et al., 1937). In this study, using a fixed cadmium concentration, the amount of cadmium found in the insect also increased with an increase in the dissolved oxygen. Therefore, cadmium absorption may be coupled to metabolism.     

谷胱甘肽与蛋氨酸对饮水砷暴露小鼠体内砷化物的分布和甲基代谢的影响

目的探讨外源性谷胱甘肽(glutathione,GSH)和L-蛋氨酸(L-Methionine,L-Met)干预后,对饮水砷暴露小鼠肝、肾和血中化物的分布和甲基代谢的影响。方法将实验小鼠随机分为对照组(Con组)、单纯染砷组(As组)、GSH干预组(GSH组)与L-Met干预组(L-Met组)。小鼠自由饮用含砷50mg/L的水。从第4周起,染砷组同时腹腔注射GSH和L-Met进行处理,共处理7天。末次注射后24h处死小鼠,取其肝、肾和血组织样品。采用氢化物发生-超低温捕集-原子吸收分光光度法分别检测小鼠肝、肾和血中无机砷(inorganic arsenic,iAs)、一甲基胂(monomethylarsenic acid,MMA)和二甲基胂(dimethylarsenic acid,DMA)含量。结果L-Met组小鼠肝中DMA含量和砷二甲基化率(SMI)显著高于As组;GSH干预组小鼠肝中砷一甲基化率(PMI)和SMI显著高于As组。L-Met组和GSH组小鼠血中DMA、总砷含量和PMI均显著高于As组。结论GSH和L-Met对小鼠体内的砷甲基化代谢具有促进作用、可加速无机砷在体内的甲基化过程,最终使砷甲基代谢的终产物DMA含量增加,从而促进了总砷的代谢与排泄。     

砷对大脑毒性的研究进展

近年来流行病学研究表明长期、过量摄入砷可导致暴露者出现周围神经症状。砷对大脑、中枢神经系统的作用越来越引起人们的重视。本文综述了砷对大脑的毒性和中枢神经系统高级神经活动的影响及有关机理的研究进展     

Effects of age and magnesium ions on oxygen toxicity in the neonate chicken

White Leghorn male chicks, 2-6 days and 4 weeks old, were injected with MgCl2 (2 mM Mg/kg body weight) and exposed to 100% O2 at 75 lb/in2 (approximately 5 atm). Compared to saline-injected controls, average time to onset of convulsions was delayed 37% in the younger group with no significant difference in the protective effect during days 2-6. The delay in onset of convulsions was 66% in the 4-week-old group. The protective action of Mg++ in the chick agrees closely with that reported for the mature rat. Chicks treated with Mg++ did not appear depressed. Susceptibility to hyperbaric O2 convulsions increased uniformly between the 2nd and 6th day, with time to onset of convulsions decreasing by 1.4 min/day from the 19.3 +/- 1.01 (SE) min observed at day 2 for saline controls. Between the 6th and 28th day, susceptibility was relatively stable with time to onset decreasing by about 0.2 min/day in controls.     

Effect of low dissolved oxygen on aquatic life stages of the caddisfly Clistoronia magnifica (Limnephilidae)

Embryos, larval stages (instars I–V), pupal stages, and pharate adults of the caddisfly Clistoronia magnifica (Limnephilidae) were exposed to a range of dissolved oxygen (DO) concentrations (0.9–8.3 mg/L) for 4–88 days in the laboratory. Some embryos suspended growth at low DO, resuming growth and hatch when DO was increased. Embryos and larvae all had 96-h EC50 values (50% mortality at 96 h) of about 2.0 mg/L DO. The statistical Effect and No-Effect Thresholds for larvae exposed through two molts from instars I–III were 1.6 and 2.4 mg/L, respectively. At DO concentrations below 4.6 mg/L, egg hatch, larval development, molting success, time of molting, pupation, and adult emergence were delayed.The information in this paper has been funded by the U.S. Environmental Protection Agency. It has been subjected to the Agency's peer and administrative review, and has been approved for publication.     

砷的毒性及排砷研究进展

砷是有毒的类金属元素,通过环境污染和职业性接触进入体内,对人体的皮肤、神经系统、心血管、肝脏及肾脏等有明显的损伤。在砷中毒治疗中,常用临床药物虽然排砷效果好,但具有一定的局限性,寻求一种高效、价廉、无不良反应且能广泛用于患者的排砷药物是当务之急。笔者就近年来国内外学者有关砷对机体的损害及排砷治疗的研究进展进行综述。     

Ecotoxicological responses of the mayfly Baetis tricaudatus to dietary and waterborne cadmium: implications for toxicity testing

Trace metals readily accumulated by stream periphyton may enter aquatic food chains through grazer ingestion. Hence, experiments were conducted to determine the ecotoxicological responses of the grazing mayfly Baetis tricaudatus to dietary cadmium. Short-term feeding experiments indicated that B. tricaudatus nymphs did not initially avoid grazing on cadmium-contaminated diatom mats. During a partial life-cycle experiment, 4 and 10 microg/g of dietary cadmium significantly inhibited grazing, whereas 10 microg/g significantly inhibited growth. Feeding inhibition was the likely mechanism that inhibited growth (i.e., through reduced energy intake). Conversely, when exposed to waterborne cadmium using lethal toxicity test procedures, B. tricaudatus nymphs were relatively tolerant (96-h median lethal concentration, 1,611 microg/L). Thus, sublethal responses to dietary exposure appeared to be more sensitive than lethal responses to waterborne exposure. Because adult mayfly fecundity is a function of nymph size at emergence, dietary cadmium exposure could increase the extinction probability within mayfly populations. The present study highlights the importance of dietary exposure routes in determining the ecotoxicological responses of an organism to a contaminant. Furthermore, the findings emphasize the advantage of evaluating a combination of ecologically relevant, lethal and sublethal endpoints in laboratory methods used to generate data for ecological risk assessment and regulation.     

砷的生殖毒性研究进展

人群流行病学研究已肯定砷是人类致癌物和神经毒物[1]。近年来的研究资料表明,砷是已肯定的生殖毒物之一,并且其生殖发育毒性较强[2,3]。一、砷对生殖细胞的影响有关砷对生殖细胞的影响国内外已有不少报道[49]。用75ｍｇＬ的三氧化二砷(Ａｓ2Ｏ3)水溶液给Ｗｉｓｔａｒ大鼠染毒,在染砷的第1、3、6个月分别做精子畸形检查,结果发现不同染砷阶段的精子畸形率均显著高于对照组[4]。用92ｍｇｋｇ和46ｍｇｋｇ的Ａｓ2Ｏ3连续灌胃5ｄ,第35天观察精子形态,结果显示精子畸形率染毒组均高于对照组。畸形的类型主要有胖头,其次是无定形、无钩和颈扭转[5…