抗除草剂海洋微藻的生长和积累EPA的特性

在群体水平上研究了海产野生型眼点拟微球藻(Nannochloropsis oculata)及其抗除草剂Sandoz9785的细胞培养物在生长和脂肪酸组成方面的特性。结果表明,野生型藻株对Sandoz 9785较为敏感,除草剂用量为50μmol·L~(-1)时其生长的被抑制率为75％。在除草剂抑制作用下,野生型细胞的总脂肪酸含量显著下降,而EPA含量显著提高。在160μmol·L~(-1)和320μmol·L~(-1)Sandoz 9785浓度下,筛选到抗除草剂的细胞培养物R160和R320,其平均比生长速率与野生型没有显著差异,细胞的总脂肪酸、16;0、16:1ω9、18:0和18:1ω9的含量都低于野生型藻株,但20:5ω3(EPA)含量则高于野生型。R160在无除草剂的培养基中EPA含量最高,可占细胞干重的3.51％,比野生型提高了30％,但与野生型差异不显著。并讨论了抗性培养物抗Sandoz 9785和积累 EPA的机理。     

急性除草剂中毒的重要临床进展

除草剂是农业生产中一种常用药剂,其导致的急性中毒在我国较为多见,已成为严峻的公共卫生问题,引起人 们广泛关注。除草剂种类繁多,毒性差异大,缺乏特效解毒药,使得救治棘手,病死率极高。文章主要对急性除草剂 的诊疗进展进行阐述,旨在提高临床常见除草剂急性中毒的救治成功率,为中毒患者提供更有效的救治方案,减轻其 社会危害。     

A C?As lyase for degradation of environmental organoarsenical herbicides and animal husbandry growth promoters

Arsenic is the most widespread environmental toxin. Substantial amounts of pentavalent organoarsenicals have been used as herbicides, such as monosodium methylarsonic acid (MSMA), and as growth enhancers for animal husbandry, such as roxarsone (4-hydroxy-3-nitrophenylarsonic acid) [Rox(V)]. These undergo environmental degradation to more toxic inorganic arsenite [As(III)]. We previously demonstrated a two-step pathway of degradation of MSMA to As(III) by microbial communities involving sequential reduction to methylarsonous acid [MAs(III)] by one bacterial species and demethylation from MAs(III) to As(III) by another. In this study, the gene responsible for MAs(III) demethylation was identified from an environmental MAs(III)-demethylating isolate, Bacillus sp. MD1. This gene, termed arsenic inducible gene (arsI), is in an arsenic resistance (ars) operon and encodes a nonheme iron-dependent dioxygenase with C⋅As lyase activity. Heterologous expression of ArsI conferred MAs(III)-demethylating activity and MAs(III) resistance to an arsenic-hypersensitive strain of Escherichia coli, demonstrating that MAs(III) demethylation is a detoxification process. Purified ArsI catalyzes Fe²⁺-dependent MAs(III) demethylation. In addition, ArsI cleaves the C⋅As bond in trivalent roxarsone and other aromatic arsenicals. ArsI homologs are widely distributed in prokaryotes, and we propose that ArsI-catalyzed organoarsenical degradation has a significant impact on the arsenic biogeocycle. To our knowledge, this is the first report of a molecular mechanism for organoarsenic degradation by a C⋅As lyase.The metalloid arsenic is the most common environmental toxic substance, entering the biosphere primarily from geochemical sources, but also through anthropogenic activities (1). Arsenic is a group 1 human carcinogen that ranks first on the Agency for Toxic Substances and Disease Registry Priority List of Hazardous Substances (www.atsdr.cdc.gov/SPL/index.html). Microbial arsenic transformations create a global arsenic biogeocycle (1). These biotransformations include redox cycles between the relatively innocuous pentavalent arsenate and the considerably more toxic and carcinogenic trivalent arsenite (2, 3). In addition, many microbes, both prokaryotic and eukaryotic, have arsM genes for inorganic arsenite [As(III)] S-adenosylmethionine methyltransferases that methylate inorganic As(III) to mono-, di-, and tri-methylated species (4, 5). The genes encoding arsenic transforming enzymes are widely distributed, and these arsenic biotransformations have been proposed to play significant roles in the arsenic biogeocycle and in remodeling the terrain in volcanic areas such as Yellowstone National Park and regions of the world with high amounts of arsenic in soil and water such as West Bengal and Bangladesh (3, 6).Arsenicals, both inorganic and organic, have been used in agriculture in the United States for more than a century (7). Historically, the use of inorganic arsenical pesticides/herbicides has been largely replaced by methylated arsenicals such as monosodium methylarsonic acid (MSMA), which is still in use as an herbicide for turf maintenance on golf courses, sod farms, and highway rights of way, and for weed control on cotton fields (7). More complex pentavalent aromatic arsenicals such as roxarsone [4-hydroxy-3-nitrophenylarsonic acid, Rox(V)] have been largely used since the middle of the 1940s as antimicrobial growth promoters for poultry and swine to control Coccidioides infections and improve weight gain, feed efficiency, and meat pigmentation (8, 9). These aromatic arsenicals are largely excreted unchanged and introduced into the environment when chicken litter is applied to farmland as fertilizer (8). Pentavalent organoarsenicals are relatively benign and less toxic than inorganic arsenicals; however, aromatic (8–10) and methyl (11, 12) arsenicals are degraded into more toxic inorganic forms in the environment, which may contaminate the foods and water supplies. Although microbial degradation of environmental organoarsenicals has been documented (8, 9, 11, 13), no molecular details of the reaction have been reported. We recently demonstrated that a microbial community in Florida golf course soil carries out a two-step pathway of MSMA reduction and demethylation (14). Here we report the isolation of an environmental methylarsonous acid [MAs(III)]-demethylating bacterium Bacillus sp. MD1 (for “MAs(III) demethylating”) from Florida golf course soil and the cloning of the gene, termed arsenic inducible gene (arsI), responsible for MAs(III) demethylation. The gene product, ArsI, is nonheme iron-dependent dioxygenase with C⋅As lyase activity. ArsI cleaves the C⋅As bond in a wide range of trivalent organoarsenicals, including the trivalent roxarsone [Rox(III)], into As(III), which strongly suggests that the environmental pentavalent phenylarsenicals such as Rox(V) also undergo a two-step pathway of sequential reduction and ArsI-catalyzed dearylation, in analogy with the demethylation of MSMA by a microbial community. Thus, ArsI-catalyzed C⋅As bond cleavage is a newly identified mechanism for degradation of organoarsenical herbicides and antimicrobial growth promoters.     

Analysis of long non‐coding RNA involved in atrazine‐induced testicular degeneration of Xenopus laevis

Long non‐coding RNA (lncRNA) plays a critical role in male germline development. Atrazine (AZ) as an environmental endocrine disrupting chemical (EDCs) can induce male reproductive toxicity in amphibians. Our previous studies demonstrated that AZ can alter gene and circular RNA (circRNA) expression of damaged testes in Xenopus laevis (X. laevis). We furthered to investigate the lncRNA expression profiling in the testis of X. laevis. Over 3559 lncRNAs were detected by lncRNA sequencing. AZ induced 40 upregulated and 46 downregulated differentially expressed lncRNAs. KEGG analysis showed that AZ‐affected lncRNAs mainly involve in 19 pathways among which 12 pathways are found in circRNA analysis. This study for the first time demonstrated that AZ can alter lncRNAs which may play a role in testicular degeneration through regulating expressions of functional genes in X. laevis. Our data may provide more insights on the mechanism about male reproductive toxicity of EDCs.     

Glyphosate herbicide formulation: a potentially lethal ingestion

Glyphosate surfactant herbicide (GlySH) toxicity is an uncommon poisoning. We report two fatalities involving suicidal ingestion of this herbicide. Both deaths occurred despite early recognition of the serious nature of the poisoning and aggressive treatment. The deaths in this series are analysed in the context of a review of existing literature. Although traditionally regarded as minimally toxic, many deaths have been reported following suicidal ingestion. Severe GlySH toxicity may be refractory even to the most intensive supportive care. The triad of pulmonary oedema, metabolic acidosis and hyperkalaemia portends poor outcome. While containing a carbon phosphorus moiety, GlySH does not exhibit organophosphate toxicity. A clinical guide to assessing severity of GlySH toxicity is proposed and treatment modalities discussed.     

Subtle effects of herbicide use in the context of genetically modified crops: a case study with glyphosate (Roundup)

Research on the effects of glyphosate and seed germination spans 30 years. Despite several studies reporting detrimental effects of the herbicide on seedling germination and growth, glyphosate is still being registered for use as a weed killer and preharvest desiccant. Its nonselective nature and low chance of species developing resistance has lead to the development of genetically modified crops tolerant to the herbicide which also raises concerns about increased reliance on herbicide use, and subtle ecological impact.This paper presents the result of a literature review on past studies mostly, on crop species, and the results of a new experiment performed with emphasis on noncrop species. The new experimental part attempted to determine whether glyphosate (Roundup®) would have an effect on the germination and growth of the F1 generation of seeds produced by plants sprayed with the herbicide. It was designed to mirror spray drift which might affect noncrop plants in nontarget drift zones. Of the 11 species tested using treatments of 0% (control), 1%, 10% or 100% of a 890 g a.i./ha label rate solution sprayed near seed maturity, seven showed a significant effect of the glyphosate treatment on germination and/or growth characteristics.Results of this experiment together with several previous studies reviewed in this paper suggest that there are significant effects to keep in mind when using herbicides such as glyphosate as severe ecological changes could occur.     

A Comparative Study of Direct Hemoperfusion and Hemodialysis for the Removal of Glufosinate Ammonium

Abstract

BASTA® is a herbicide containing glufosinate ammonium 18.5% and a surface-active agent. There were six fatalities in 34 cases of glufosinate ammonium poisoning reported by the Japan Poison Information Center. To evaluate efficacy in the removal of glufosinate ammonium from the blood, two bottles were prepared containing 600 mL of heparinized bovine blood with 1 mL or 3 mL of BASTA. Direct hemoperfusion or hemodialysis was performed for two hours at a flow rate of 50 mL/min. The final glufosinate ammonium concentration of the blood bottle containing 1 mL of BASTA decreased to 96.9% of the initial concentration after direct hemoperfusion and to 0.5% after hemodialysis. The final glufosinate ammonium concentration of the bottle containing 3 mL of BASTA decreased to 62.2% after direct hemoperfusion and to 0.9% after hemodialysis. Hemodialysis is more effective than direct hemoperfusion for removal of glufosinate ammonium from blood.     

Clinical Presentations and Prognostic Factors of a Glyphosate — Surfactant Herbicide Intoxication A Review of 131 Cases

OBJECTIVE: Suicide attempts with agricultural chemicals are common in southern Taiwan. Among them, glyphosate-surfactant herbicide (GlySH) intoxication has been encountered with increasing frequency. Although a number of reports have described the clinical course and outcomes following ingestion, predictors of serious complications and mortality have not been elucidated. The purpose of this study was to define predictors of serious complications and probable mortality. METHODS: This was a retrospective study of 131 GlySH-intoxicated patients treated at the National Cheng Kung University Hospital from 1988 to 1995. Medical charts were reviewed and clinical and laboratory variables were abstracted, looking for predictors of mortality. RESULTS: The most common symptoms included sore throat (79.5%), and nausea with or without vomiting (73.8%). The most common laboratory findings were leukocytosis (68.0%), low serum bicarbonate (48.1%), and acidosis (35.8%). Overall, 11 of 131 patients (8.4%) died; the mean +/- SEM time to death was 2.8 +/- 0.8 days after presentation. When comparing the clinical and laboratory characteristics among the survivor and fatality groups, significant differences were identified. Respiratory distress, pulmonary edema, respiratory distress necessitating intubation, shock (systolic blood pressure less than 90 mm Hg), altered consciousness, abnormal chest x-ray, renal failure necessitating hemodialysis, larger amount of ingestion (>200 mL), and hyperkalemia were predictors highly associated with poor outcomes and mortality. Using multiple logistic regression, three predictors were identified, which may predict mortality in severely intoxicated patients. CONCLUSIONS: In managing patients who have larger amount of GlySH ingestion, airway protection, early detection of pulmonary edema, and prevention of further pulmonary damage and renal damage appear to be of critical importance.     

Subchronic feeding study of stacked trait genetically-modified soybean (3Ø5423 × 40-3-2) in Sprague–Dawley rats

The genetically-modified (GM) soybean 3Ø5423 × 40-3-2 expresses siRNA for the fatty acid desaturase-2 enzyme which results in higher concentrations of oleic acid (18:1) relative to linoleic acid (18:2) compared with non-GM soybeans. It also expresses the CP4 EPSPS protein for tolerance to glyphosate. In this study, three different dietary concentrations (7.5%, 15% and 30% wt/wt) of 3Ø5423 × 40-3-2 or non-GM soybeans were fed to Sprague–Dawley rats for 90 days during which in-life nutritional and growth performance variables were evaluated followed by analysis of standard clinical chemistry, hematology and organ variables. Compared with rats fed the non-GM control diet, some statistically significant differences were observed in rats fed the 3Ø5423 × 40-3-2 diet. However the differences were not considered treatment-related and commonly fell within the normal ranges of the control group consuming the commercial diet. These results demonstrated that the GM soybean 3Ø5423 × 40-3-2 is as safe as non-GM soybeans.     

Identification of a gene essential for protoporphyrinogen IX oxidase activity in the cyanobacterium Synechocystis sp. PCC6803

Protoporphyrinogen oxidase (Protox) catalyses the oxidation of protoporphyrinogen IX to protoporphyrin IX during the synthesis of tetrapyrrole molecules. Protox is encoded by the hemY gene in eukaryotes and by the hemG gene in many γ-proteobacteria, including Escherichia coli. It has been suggested that other bacteria possess a yet unidentified type of Protox. To identify a unique bacterial gene encoding Protox, we first introduced the Arabidopsis hemY gene into the genome of the cyanobacterium, Synechocystis sp. PCC6803. We subsequently mutagenized the cells by transposon tagging and screened the tagged lines for mutants that were sensitive to acifluorfen, which is a specific inhibitor of the hemY-type Protox. Several cell lines containing the tagged slr1790 locus exhibited acifluorfen sensitivity. The slr1790 gene encodes a putative membrane-spanning protein that is distantly related to the M subunit of NADH dehydrogenase complex I. We attempted to disrupt this gene in the wild-type background of Synechocystis, but we were only able to obtain heteroplasmic disruptants. These cells accumulated a substantial amount of protoporphyrin IX, suggesting that the slr1790 gene is essential for growth and Protox activity of cells. We found that most cyanobacteria and many other bacteria possess slr1790 homologs. We overexpressed an slr1790 homolog of Rhodobacter sphaeroides in Escherichia coli and found that this recombinant protein possesses Protox activity in vitro. These results collectively demonstrate that slr1790 encodes a unique Protox enzyme and we propose naming the slr1790 gene “hemJ.”