Stereoisomeric separation and toxicity of a new organophosphorus insecticide chloramidophos

Chloramidophos (CP), O,S-dimethyl-[(2,2,2)-trichloro-1-hydroxyethyl]phosphoramidothioate, is a new organophosphorus pesticide (OP) with two chiral centers each on the phosphorus and carbon atoms. Although CP has been widely used in some provinces of China, it has received very limited attention toward its environmental behaviors, in particular, with regard to stereospecificity. In this study, the stereoisomeric separation and toxicity of CP were investigated. All of the four stereoisomers of CP were successfully separated by high-performance liquid chromatography on a Chiralpak AD column. The stereoisomers (pk 1 to pk 4) were distinguishable on their mass and circular dichroism spectra. The inhibition on acetylcholinesterases (AChE, in vitro) and the acute aquatic toxicity to Daphnia magna (in vivo) tested with optically pure stereoisomers of CP showed its stereoselectivity. The inhibitory potency toward AChE decreased in the order of pk 4 > pk 3 > pk 2 > pk 1. In comparison, the acute toxicity to D. magna was in the order of pk 3 > pk 2 > pk 1 > pk 4. The stereoselectivity was found to be isomer-dependent, with 1.1-18.1-fold differences (in vitro) and 1.2-13-fold differences (in vivo) among the stereoisomers. These results suggest that the overall toxicity of chiral OPs should be assessed using their individual enantiomers.     

Developmental toxicity of flupyrazofos, a new organophosphorus insecticide, in rats.

Flupyrazofos is a new type of pyrazole organophosporus insecticide, which has a high activity against the diamond-back moth (Plutella xylostella). The potential of this agent to induce developmental toxicity was investigated in the Sprague-Dawley rat. One hundred mated females (sperm in vaginal LAVAGE=day 0) were distributed among three treated groups and a control group. Flupyrazofos was administered by gavage to pregnant rats from days 7-17 of gestation at dose levels of 0, 5, 12 and 30 mg/kg/day. All dams were subjected to the caesarean section on day 20 of gestation and their fetuses were examined for external, visceral and skeletal abnormalities. At 30 mg/kg, maternal effects including mortality (4.3%), clinical signs of toxicity, decreased food intake, suppressed body weight, and increased weight of adrenal glands, kidney and heart were observed in dams. Litter values for corpora lutea, implantations, sex ratio and litter size were within the normal range. However, a reduction in the fetal weight and an increase in the incidence of fetal skeletal retardations were observed. At 12 mg/kg, toxic effects including mortality (4.2%), nasal discharge and some fetal skeletal retardation were observed. There were no signs of either maternal toxicity or embryotoxicity at 5 mg/kg. The results show that flupyrazofos induces fetal growth retardation only at maternally toxic doses in rats and the no-observed-adverse-effect levels (NOAELs) of this agent are considered to be 5 mg/kg for both dams and fetuses.     

Passive avoidance retention in mice tolerant to the organophosphorus insecticide disulfoton

Male mice were administered the organophosphorus insecticide disulfoton (O,O-diethyl S-[2-(ethylthio)ethyl] phosphorodithioate) daily for 14 days at a dosage rate of 10 mg/kg/day. Signs of poisoning disappeared after 5 to 8 days of treatment indicating that the animals had developed tolerance to disulfoton toxicity. Acetylcholinesterase activity was inhibited 75 to 93% in hippocampus, cerebral cortex, striatum, and cerebellum of tolerant animals. Binding of the muscarinic cholinergic antagonist [³H]quinuclidinyl benzilate was significantly decreased in all these brain areas. The decrease was due to a decrease in the number of receptors (B max) without any change in the affinity constant K_d. Sodium-dependent high-affinity choline uptake was unchanged in the hippocampus of tolerant animals. When tested in a single trial passive avoidance task, mice tolerant to disulfoton did not show any difference from controls in 24-hr retention. These results indicate that the decreased number of muscarinic receptors in brain of disulfoton-tolerant animals does not affect their response latencies in a passive avoidance task.     

Dose-dependent toxicity of diphenhydramine overdose

BACKGROUND: Diphenhydramine (DPHM) overdose is a frequent cause of acute poisoning. Although its clinical features are well known, information about the dose-dependent toxicity of DPHM is still scarce. The objective of this study was to investigate the dose-dependent toxicity of DPHM in patients with acute DPHM poisoning. METHODS: We have analyzed retrospectively all well-documented cases with DPHM monointoxications reported by physicians to the Swiss Toxicological Information Centre (STIC) between January 1984 and April 1996. In addition, a prospective study focusing on ingested DPHM doses and severity of symptoms was performed between May 1996 and December 1998. RESULTS: The retrospective and prospective studies included 232 and 50 patients with DPHM monointoxications, respectively. In both studies, mild symptoms (somnolence, anticholinergic signs, tachycardia, nausea/vomiting) occurred in 55-64%, moderate symptoms (isolated and spontaneously resolving agitation, confusion, hallucinations and ECG disturbances) in 22-27% and severe symptoms (delirium/psychosis, seizures, coma) in 14-18% of patients. Moderate symptoms occurred above ingested doses of 0.3 g DPHM. For severe symptoms the critical dose limit was 1.0 g DPHM. Although the frequency of delirium/psychosis remained constant or even decreased, coma and seizures were significantly (p<0.05) more frequent in the >1.5-g compared with the 1.0- to 1.5-g-dose group. CONCLUSIONS: These data demonstrate a clear dose-dependent acute toxicity of DPHM. They indicate that only patients with DPHM ingestions above 1.0 g are at risk for the development of severe symptoms and, therefore, should be hospitalized. Thus, the results contribute to the data basis required for a cost effective management of patients with DPHM overdose.     

群体性有机磷杀虫剂中毒救治探讨

目的探讨群体性有机磷杀虫剂（OPI）中毒救治的临床特点。方法回顾性分析一次突发群体性OPI中毒的临床资料。结果 55例OPI中毒患者为集体生活、统一进食,在相同时间段出现头昏、恶心、呕吐、上腹部疼痛,其中,32例出现皮肤潮湿多汗,1例出现心慌、心悸和燥动不安,1例出现幻觉、躁狂、谵妄、尿潴留,大多数患者、家属、老师出现不同程度的紧张恐慌情绪;40例胆碱酯酶（ChE）活力降低,15例ChE活力正常;55例患者经排毒、解毒、对症、支持治疗均痊愈。结论群体性OPI中毒救治过程中要区别对待不同患者,注意心因性反应影响病情判断,合理使用解毒药物,防治阿托品中毒发生。     

Extremely sensitive biomarker of acute organophosphorus insecticide exposure

Egasyn-beta-glucuronidase complex is located at the luminal site of liver microsomal endoplasmic reticulum. When organophosphorus insecticides (OP) are incorporated into the liver microsomes, they become tightly bound to egasyn, a carboxylesterase isozyme, and subsequently, beta-glucuronidase (BG) is dissociated and released into blood. Consequently, the increase in plasma BG activity becomes a good biomarker of OP exposure. Thus, the single administration of EPN (O-ethyl O-p-nitrophenylphenylphosphonothioate), acephate and chlorpyrifos increased plasma BG activity in approximately 100-fold the control level in rats. The increase in plasma BG activity after OP exposure is a much more sensitive biomarker of acute OP exposure than acetylcholinesterase (AChE) inhibition.     

Evaluation of oxidative stress and genotoxicity in organophosphorus insecticide formulators

The aim of this study was to evaluate genotoxicity and oxidative stress in workers who formulate organophosphorus (OP) pesticides. In this survey, blood leukocytes and erythrocytes of a group of 21 pesticide formulating workers and an equal number of control subjects were examined for genotoxicity and oxidative stress parameters. The mean comet tail length and mean comet length were used to measure DNA damage. Lipid peroxidation level, catalase, superoxide dismutase (SOD) and glutathione peroxidase activities in erythrocytes were analysed as biomarkers of oxidative stress. In addition, the acetylcholinesterase activity was measured as a biomarker of toxicity. The average duration of employment of workers in the factory was 97 months. Results indicated that chronic exposure (multiple-dose, greater than or equal to 6 months duration) to OP pesticides was associated with increased activities of catalase, SOD and glutathione peroxidase in erythrocytes. The level of lipid peroxidation and acetylcholinesterase activity did not show any significant differences between the two groups. The results also indicated that chronic exposure to OP pesticides was associated with increased DNA damage. It is concluded that human chronic exposure to OP pesticides may result in stimulated antioxidant enzymes and increased DNA damage in the absence of depressed acetylcholinesterase levels. Routine genotoxicity monitoring concomitant to acetylcholinesterase activity in workers occupationally exposed to OP insecticides is suggested.     

Effect of androgens on phalloidin-induced liver toxicity in mice

A single i.p. dose of phalloidin, 0.75 or 1 mg/kg body weight, induced peliosis hepatis-like lesion (PHLL) at 3 h after injection to mice. Pretreatment with various doses of testosterone propionate for 7 days enhanced phalloidin-induced PHLL. Other anabolic steroids, methyltestosterone, methandriol. fluoxyrnesterone and oxymetholone had no effect.     

Interaction of diphenhydramine with cholinesterase inhibitors in mice

Physostigmine (1.5 mg/kg, s.c.) and neostigmine (1.0 mg/kg, s.c.) injection into male mice produced signs of toxicosis characteristic of cholinesterase inhibition and evoked death in 95 and 94% of the animals respectively. Diphenhydramine injections (5-30 mg/kg, s.c.) 15 min before physostigmine or neostigmine significantly increased the latency period to onset of death and the percentage of survivors. Diphenhydramine injection (20 mg/kg, s.c.) between -30 and +2 min (but not at +5 and +10 min) relative to physostigmine prevented lethality in 100% of the animals. The data indicated that diphenhydramine which possesses anticholinergic effects protected mice against physostigmine- and neostigmine-induced toxicosis.     

β-氯氰菊酯对斑马鱼胚胎的发育毒性

目的以斑马鱼胚胎为模型,探讨一种高效氯氰菊酯β-氯氰菊酯对胚胎发育的影响。方法 丙酮为助溶剂,配制β-氯氰菊酯0.05,0.1,0.15,0.2,0.6和1 mg.L-1,采用换水式每12 h更换一半β-氯氰菊酯溶液,对斑马鱼胚胎进行96 h暴露处理,采用显微镜观察β-氯氰菊酯0.05,0.1,0.15,0.2,0.6和1 mg.L-1对斑马鱼胚胎发育形态,测定受精后24 h(24 hpf)自主抽动次数、48 hpf心率及孵化率、72和96 hpf体轴弯曲个体比例等。结果 与正常对照组比较,β-氯氰菊酯0.05,0.1,0.15,0.2,0.6和1 mg.L-1组斑马鱼胚胎在24 hpf前形态上未出现明显异常,48 hpf以后表现出体轴弯曲、心包囊肿等不同程度的毒性反应症状,β-氯氰菊酯0.2 mg.L-1组幼鱼胸鳍发育即受到严重抑制且黑色素减少体色偏黄;随着β-氯氰菊酯浓度的增加,斑马鱼胚胎在24 hpf时每分钟自主抽动次数由正常对照组的(0.72±0.19)次增加至(3.83±1.07)次(P<0.05);48 hpf孵化率由对照组的(15.5±4.3)%升高至(98.9±1.2)%(P<0.05)。β-氯氰菊酯0.05 mg.L-1组72 hpf和96 hpf体轴弯曲个体比例分别为6.6%和10%,β-氯氰菊酯1 mg.L-1组分别为97.8%和100%。结论 β-氯氰菊酯对斑马鱼胚胎的神经及形态发育均有明显抑制作用,并且呈现一定的时间剂量依赖性。     

Vascular wall damage in rats induced by organophosphorus insecticide methidathion

We have examined the effect of subchronic methidathion (MD) administration on vascular wall damage. The experimental groups were: control group and rats treated with 5 mg/kg MD. The MD group was given MD by gavage for 5 days a week for 4 weeks at a dose level of 5 mg/kg per day by using corn oil as the vehicle. The levels of malondialdehyde (MDA) were determined in the vascular tissue. Histopathological examination was examined in the thoracic aortic tissue. The levels of MDA were increased in the MD group compared with the control group (P < 0.01). In the MD group, subchronic MD administration led to the irregulation, prominent breaks and fragmentation of the elastic fibers were located in the media of aortic wall. In conclusion, it is likely that subchronic MD administration caused vascular wall damage and, in addition, lipid peroxidation may be one of the molecular mechanisms involved in MD-induced vascular toxicity.     

Effect of preinduction of metallothionein on paraquat toxicity in mice

The effect of pretreatment with metallothionein (MT)-inducing metals (Zn, Cu, Bi, Co, Cd or Hg) on paraquat (PQ) toxicity was investigated in mice. PQ lethality was remarkably reduced by pretreatment with the above MT-inducing metals. The protective effect of pretreatment with these metals on PQ lethality was significantly correlated with MT levels in the lung, a target tissue of PQ toxicity, in mice administered MT-inducing metals, but not with MT in the liver or kidney. The increase in pulmonary lipid peroxidation in mice treated with PQ was significantly inhibited by Zn pretreatment. Zn was the most effective of the MT-inducing metals used in this experiment in protecting mice against PQ lethality. Of those monitored, the only pulmonary free radical scavenging factor increased by Zn pretreatment was MT. Other free radical scavenging factors (activities of Superoxide dismutase, glutathione peroxidase and catalase, and concentration of non-protein thiols level) were not influenced by Zn treatment. These results indicate that the induction of pulmonary MT protects against the lethality and lung toxicity of PQ. Pulmonary MT may scavenge free radicals produced by PQ, thereby protecting against lethal pulmonary toxicity.     

Effect of ascorbate on the toxicity of morphine in mice

The effects of ascorbic acid on the toxicity of morphine in mice were investigated. An intraperitoneal dose of sodium ascorbate (1 G/kg) injected 10 min prior to morphine (500 mg/kg, i.p.) was found to provide significant protection against mortality due to respiratory depression, while having no effect on the lethality of the pentobarbital. Pretreatment with ascorbate had no effect on the distribution of morphine in brain tissue, nor did it alter the pH of the plasma. Administration of ascorbate in vivo also produced no inactivation of binding to opioid receptors. It is postulated that ascorbate antagonizes the lethality of morphine by selectively affecting neuronal activity.     

Effect of L-cystine on toxicity of paraquat in mice.

The protective effect of L-cystine on the toxicity of paraquat (PQ) in mice was studied. Lipid peroxidation in the lung significantly increased after oral administration of PQ (200 mg/kg) and the increase in lipid peroxidation was prevented by L-cystine treatment (300 mg/kg). PQ administration produced an increase in superoxide dismutase (SOD) activity and a decrease in glutathione peroxidase (GSH-Px) activity in the lung at 24 h after PQ. L-Cystine treatment significantly prevented the changes in SOD and GSH-Px activity in the lung after PQ. L-Cystine treatment prevented the decrease in non-protein sulfhydryl (NP-SH) content in the lung after PQ administration. The tissue distribution and excretion of PQ after PQ administration were not changed by L-cystine treatment. Plasma aspartate aminotransferase activity did not change after PQ administration. These results suggest that L-cystine protects against the toxicity of PQ by maintaining reduced glutathione levels in the cells.     

Environmental pyrethroid and organophosphorus insecticide exposures and sperm concentration

BACKGROUND: There is growing concern that poisoning and other adverse health effects are increasing because organophosphorous (OP) insecticides are now being used in combination with pyrethroid (PYR) insecticides to enhance the toxic effects of PYR insecticides on target insects, especially those that have developed PYR resistance. OBJECTIVES: We conducted a pilot biomonitoring study to determine whether men in our reproductive cohort study were being exposed to pesticides environmentally by virtue of frequenting an agricultural setting. METHODS: We screened 18 randomly selected urine samples collected from male participants of reproductive age for 24 parent compounds and metabolites of pesticides and examined the results in relation to sperm concentration. RESULTS: Results showed high prevalence of exposure to OP and PYR pesticides and our preliminary analyses provided some suggestion that the higher exposure group had lower sperm concentration. CONCLUSIONS: The potential of OP/PYR mixtures to have enhanced human toxicity needs more research attention.