Fluoroacetate producing plants grow worldwide and it is believed they produce this toxic compound as a defence mechanism against grazing by herbivores. Ingestion by livestock often results in fatal poisonings, which c...Fluoroacetate producing plants grow worldwide and it is believed they produce this toxic compound as a defence mechanism against grazing by herbivores. Ingestion by livestock often results in fatal poisonings, which causes significant economic problems to commercial farmers in many countries such as Australia, Brazil and South Africa.Several approaches have been adopted to protect livestock from the toxicity with limited success including fencing,toxic plant eradication and agents that bind the toxin. Genetically modified bacteria capable of degrading fluoroacetate have been able to protect ruminants from fluoroacetate toxicity under experimental conditions but concerns over the release of these microbes into the environment have prevented the application of this technology.Recently, a native bacterium from an Australian bovine rumen was isolated which can degrade fluoroacetate. This bacterium, strain MFA1, which belongs to the Synergistetes phylum degrades fluoroacetate to fluoride ions and acetate. The discovery and isolation of this bacterium provides a new opportunity to detoxify fluoroacetate in the rumen. This review focuses on fluoroacetate toxicity in ruminant livestock, the mechanism of fluoroacetate toxicity,tolerance of some animals to fluoroaceate, previous attempts to mitigate toxicity, aerobic and anaerobic microbial degradation of fluoroacetate, and future directions to overcome fluoroacetate toxicity.展开更多
为建立一种离子色谱-质谱法检测血液中γ-羟基丁酸(GHB)、氟乙酸钠、亚硝酸钠、草甘膦和草铵膦五种水溶性毒物的方法,选用AS19阴离子色谱柱进行分离,以在线产生的50 mmol/L氢氧化钠为淋洗液等度淋洗,飞行时间质谱仪作检测器,采用电喷雾...为建立一种离子色谱-质谱法检测血液中γ-羟基丁酸(GHB)、氟乙酸钠、亚硝酸钠、草甘膦和草铵膦五种水溶性毒物的方法,选用AS19阴离子色谱柱进行分离,以在线产生的50 mmol/L氢氧化钠为淋洗液等度淋洗,飞行时间质谱仪作检测器,采用电喷雾电离源负离子模式、选择离子监测模式(Selected Ion Monitor,SIM)进行分析,外标法定量。利用离子色谱-质谱法检测五种水溶性毒物简单快速、专属性强、灵敏度高,可为司法鉴定实践提供重要的科学支撑。展开更多
One of the most potent rodenticides is 2_fluoroacetamide (2_FA). Toxicity of this chemical is well documented. However, its inhalation toxicity data is not available in the literature. Hence, \{acute\} inhalation toxi...One of the most potent rodenticides is 2_fluoroacetamide (2_FA). Toxicity of this chemical is well documented. However, its inhalation toxicity data is not available in the literature. Hence, \{acute\} inhalation toxicity study was carried out by exposing male and female rats to aerosols of 2_FA at different concentrations for 4 h in a dynamically operated whole body inhalation exposure chamber. During and after the inhalation exposure the rats were less active, and showed mild tremors and convulsions. At higher concentrations the rats died after 2_3 days. The estimated 4_h LC 50 for male and female rats was 136.6 and 144.5 mg·m -3 respectively. Exposure to 0.7 LC 50 for 4 h duration showed an increase in the liver weight of male and female rats 7 days after exposure. Various haematological and biochemical variables determined were within the normal limits. However, histological findings showed injured lung as indicated by desquamation and necrosis of the epithelium of the respiratory tract. Marked hypertrophy of hepatocytes displaying strong acidophilic granulated cytoplasm was observed. Focal dilatation of renal proximal tubules in kidney with cytoplasmic vacuolation, and irregularly placed pyknotic nuclei were seen. The present study shows that 2_FA is a highly toxic chemical through the inhalation route based on the LC 50 value. Consequently necessary precautions should be taken during its handling.展开更多
In the cultivation of gene engineered strain of Escherichia coli on glucose medium, excretion and accumulation of acetic acid inhibit not only cell growth but also the the expression of heterologous protein. It is obv...In the cultivation of gene engineered strain of Escherichia coli on glucose medium, excretion and accumulation of acetic acid inhibit not only cell growth but also the the expression of heterologous protein. It is obvious that the desirable host strain maintaining acetate at a low level is one of the approaches to increase the production of recombinant protein. The present article deals with the selection of mutants of E.coli DP19, DP8, which grow on the medium containing pyruvate as the sole carbon source in the presence of 50mmol/L fluoroacetic acid. It is shown that mutant DP19 is defective in its phosphotransacetylase(PTA)activity and accumulates less acetate in the medium, while DP8 is defective in acetate kinase (ACK)and accumulates similar level of acetate comparing with its parent. Using pta - mutant E.coli DP19 as host, the expression of GL 7ACA acylase gene on the recombinant plasmid pMR24 is improved, and the yield of enzyme activity in flask fermentation is about twice as much as its parent.展开更多
文摘Fluoroacetate producing plants grow worldwide and it is believed they produce this toxic compound as a defence mechanism against grazing by herbivores. Ingestion by livestock often results in fatal poisonings, which causes significant economic problems to commercial farmers in many countries such as Australia, Brazil and South Africa.Several approaches have been adopted to protect livestock from the toxicity with limited success including fencing,toxic plant eradication and agents that bind the toxin. Genetically modified bacteria capable of degrading fluoroacetate have been able to protect ruminants from fluoroacetate toxicity under experimental conditions but concerns over the release of these microbes into the environment have prevented the application of this technology.Recently, a native bacterium from an Australian bovine rumen was isolated which can degrade fluoroacetate. This bacterium, strain MFA1, which belongs to the Synergistetes phylum degrades fluoroacetate to fluoride ions and acetate. The discovery and isolation of this bacterium provides a new opportunity to detoxify fluoroacetate in the rumen. This review focuses on fluoroacetate toxicity in ruminant livestock, the mechanism of fluoroacetate toxicity,tolerance of some animals to fluoroaceate, previous attempts to mitigate toxicity, aerobic and anaerobic microbial degradation of fluoroacetate, and future directions to overcome fluoroacetate toxicity.
文摘为建立一种离子色谱-质谱法检测血液中γ-羟基丁酸(GHB)、氟乙酸钠、亚硝酸钠、草甘膦和草铵膦五种水溶性毒物的方法,选用AS19阴离子色谱柱进行分离,以在线产生的50 mmol/L氢氧化钠为淋洗液等度淋洗,飞行时间质谱仪作检测器,采用电喷雾电离源负离子模式、选择离子监测模式(Selected Ion Monitor,SIM)进行分析,外标法定量。利用离子色谱-质谱法检测五种水溶性毒物简单快速、专属性强、灵敏度高,可为司法鉴定实践提供重要的科学支撑。
文摘One of the most potent rodenticides is 2_fluoroacetamide (2_FA). Toxicity of this chemical is well documented. However, its inhalation toxicity data is not available in the literature. Hence, \{acute\} inhalation toxicity study was carried out by exposing male and female rats to aerosols of 2_FA at different concentrations for 4 h in a dynamically operated whole body inhalation exposure chamber. During and after the inhalation exposure the rats were less active, and showed mild tremors and convulsions. At higher concentrations the rats died after 2_3 days. The estimated 4_h LC 50 for male and female rats was 136.6 and 144.5 mg·m -3 respectively. Exposure to 0.7 LC 50 for 4 h duration showed an increase in the liver weight of male and female rats 7 days after exposure. Various haematological and biochemical variables determined were within the normal limits. However, histological findings showed injured lung as indicated by desquamation and necrosis of the epithelium of the respiratory tract. Marked hypertrophy of hepatocytes displaying strong acidophilic granulated cytoplasm was observed. Focal dilatation of renal proximal tubules in kidney with cytoplasmic vacuolation, and irregularly placed pyknotic nuclei were seen. The present study shows that 2_FA is a highly toxic chemical through the inhalation route based on the LC 50 value. Consequently necessary precautions should be taken during its handling.
文摘In the cultivation of gene engineered strain of Escherichia coli on glucose medium, excretion and accumulation of acetic acid inhibit not only cell growth but also the the expression of heterologous protein. It is obvious that the desirable host strain maintaining acetate at a low level is one of the approaches to increase the production of recombinant protein. The present article deals with the selection of mutants of E.coli DP19, DP8, which grow on the medium containing pyruvate as the sole carbon source in the presence of 50mmol/L fluoroacetic acid. It is shown that mutant DP19 is defective in its phosphotransacetylase(PTA)activity and accumulates less acetate in the medium, while DP8 is defective in acetate kinase (ACK)and accumulates similar level of acetate comparing with its parent. Using pta - mutant E.coli DP19 as host, the expression of GL 7ACA acylase gene on the recombinant plasmid pMR24 is improved, and the yield of enzyme activity in flask fermentation is about twice as much as its parent.
