| Along with improving the wrold, human beings are also polluting the environment to different degree. In return, the environment pollution will interfere and damage people’s normal life as well as the growth of creatures, and even lead to the imbalance of ecological environment, therefore, it is to be urgent to strengthen the environmental monitoring and controlling. Among those environment pollution including fuel and emission pollutant, Environmental hormone pollution is newly presented, which is easily ignored for its high concealment. However, the long-term exposure to environmental hormone would produce adverse reactions to creatures and humbeings. There are many types of environmental hormone, about 70% of which are pesticides, and most pesticides are the environmental hormone. Most traditional instrument analysis cannot evaluate toxicity effect of its component, while biological indicator toxicology tests can make up this shortage. In recent years, Caenorhabditis elegans has been an ideal model organism due to its own characteristics and advantages, which is widely applied in environment assessment. There have been some reports that toxicity evaluation of pesticide pollution is carried with the worm of C. elegans, however most studies focused on biology and biological mechanism. There are very few reports in toxicology testing at the level of population, and this paper used the C. elegans as a live animal model, testing the acute toxicity of three environment hormone pesticides which were dichlorvos, monocrotophos and dimethoate. On this basis, it studied the toxicity of pesticides at sublethal concentrations on the worms of C. elegans at individual level, and population level, and their mechanism were also discussed in this paper.The mortality of the nematodes was tested, and the results showed that 4 h LC50 of dichlorvos was 47.09±1.41 μmol/L, that 4 h LC50 of monocrotophos was 18.88±0.21 mmol/L, and 4 h LC50 of dimethoate was 69.95±0.12 mmol/L. The results of joint action experiments showed that the mixture of dichlorvos and monocrotophos showed synergistic effect, and the synergistic effect of the mixture in high dose was more apparent than in low dose; the mixture of dichlorvos and dimethoate showed synergistic effect also, and the effect was more apparent than the mixture of dichlorvos and moncrotophos; the mixture of dimethoate and monocrotophos showed addition joint action.From three aspects of acetylcholinesterase (AChE) activity, feeding rate and the movement ability, neurotoxic effects of dichlorvos, monocrotophos and dimethoate on nematodes were detected. The results showed that with the increase of the concentration of the three pesticides, the AChE activity of nematodes gradually reduced and presented the obvious dose effect relationship. These three pesticides also inhibited the feeding rate, the inhibition of between AChE activity and of feeding rate were obvious linear correlation, the values of R2 were 0.8917,0.7590,0.8907 respectively. These three pesticides also inhibited the movement ability of the worms, the inhibitions of between AChE activity and of forword movement had some linear correlation, and the values of R2 were 0.6284,0.5980,0.7213 respectively.The effects of the three pesticides on physiological and biochemical characteristics were tested, using body length, SOD activity, CAT activity, GSH content and ROS content as biological endpoint. Results showed that the growth rates of the nematodes were restrained by the three pesticides, but with the extension of the recovery time, the growth of worms would be improved in certain period of time to reduce the growth retardation caused by discomfort environment before, but if the exogenous pollutants concentration was too high, it caused stunting which was difficult to return to normal levels. The glutathione (GSH) content of worms was negatively related with the concentration of the three pesticides, and there was a dose effect relationship. The SOD enzyme activity of worms was negatively related with the concentration of the three pesticides, and there was a dose effect relationship. The effect of dichlorvos on the CAT enzyme activity of worms was not remarkable, while the effects of moncrotophos and dimethoate on the CAT enzyme activity of worms were obvious, the enzyme activity and pesticide concentration showed dose effect, and differences between groups were statistically significant. The ROS content of worms were positively correlated with the concentration of the three pesticides, and there was a dose effect relationship.Using improved semi-fluid culture medium, effects of the three pesticides on the experimental population dynamics had been studied, and results showed that the pesticides inhibited the growth of the nematode populations. The total fertility rate (TFR), net reproductive rate (Ro), mean lifespan(eo) and intrinsic rate of increase (rm) of the nematodes in treatment groups were all decreased when the concentration of pesticides increased, and the difference was significant. However, dimethoate in low doses had poison excited effect (Hormesis) on rm of C. elegans.The mechanism of fertility decline caused by environmental hormones pesticides were discussed from the gametogenesis when dimethoate was chosen as pollutant. The results showed that the nematodes exposed in dimethoate for 24 h, then the mitotic germ cells decreased, and the apoptoctic germ cells increased, so the oogenesis of worms was restrained by dimethoate. However when the nematodes exposed in dimethoate only for 4 h, the oogenesis of worms was not reduced significantly, while the sperm related genes (fer-1, folt-1 and spe-10) expression decreased obviously, so that these three pesticides inhibited the spermatogenesis of C. elegans.Base on all the test results in this paper, these biological endpoints could be applied in the toxicity evaluation of the three environmental hormone pesticides: Individual level indicators:mortality, LC50, feeding rate, movement, length, AChE activity, GSH content and SOD activity, CAT activity, ROS content, mitotic germ cell, apoptotic germ cells, sperm genes (fer-1, folt-1 and spe-10); Population level indicators: TFR, Ro, eo, rm. This paper can provide a certain amount of research foundation to monitor and assess the toxicity of environmental hormone pollution, which will give reliable research datas for integrated management of pollution. |
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