The effect of trichlorfon and other organophosphates on prenatal brain development in the guinea pig

The organophosphates trichlorfon, dichlorvos, dimethoate, soman, triortho-cresyl phosphate (TOCP), and the diethoxy-analogue of trichlorfon (O,O-diethyl 2,2,2-trichloro-1-hydroxyethylphosphonate, ethyl-trichlorfon), were administrated to guinea pigs between day 42 and 46 of gestation. When the offsprings were examined at birth, there was a severe reduction in brain weight in the case of trichlorfon and dichlorvos, but not after treatment with the other organophosphates. The reduction in weight was most pronounced for cerebellum, medulla oblongata, thalamus/hypothalamus and quadrigemina. The effect was less marked for cerebral cortex and hippocampus. Since soman, a potent anticholinesterase, and TOCP, an inhibitor of neuropathy target esterase, did not show any effects, this excludes that the brain hypoplasia can be caused by inhibition of these two enzymes. Further, the lack of effect with ethyl-trichlorfon has shed some light on the part of the trichlorfon molecule which could be involved in the formation of the hypoplasia. It is suggested that alkylation of DNA may be involved in the development of the lesion. The possible consequences for a teratogenic effect of trichlorfon and dichlorvos on humans are discussed.Special issue dedicated to Dr. Bernard W. Agranoff.     

神经肌接头上产生持续性去极化时小终板电位的变化

实验在大鼠膈肌标本上观察梭曼处理后,终板区持续性去极化（ｓｕｓｔａｉｎｅｄｄｅｐｏｌａｒｉｚａｔｉｏｎ,ＳＤ）产生时小终板电位（ＭＥＰＰ）的变化,以分析产生ＳＤ的机理。静息时,加入５．５μｍｏｌ／Ｌ梭曼后,ＭＥＰＰ的频率、幅度和下降时间常数分别是加药前的１．８,１．３和３．０倍（Ｐ＜０．０１）。间接强直刺激时,记录到ＳＤ,ＳＤ过程中不仅终板电位消失,ＭＥＰＰ也完全消失。ＳＤ之后一定时间ＭＥＰＰ恢复出现,然后其频率逐渐增高。从ＳＤ开始到ＭＥＰＰ明显恢复的时间与强直刺激参数有关,５０Ｈｚ×１ｓ和５０Ｈｚ×０．１ｓ强直刺激时,分别为２９．７±０．７ｓ和１１．７±３．０ｓ。结果表明,在乙酰胆碱酯酶活性被抑制后,静息时突触前自发ＡＣｈ释放增加;刺激神经时,突触后对ＡＣｈ反应性降低甚至失去反应性,是产生ＳＤ的主要机理。     

Chiral Separation of G‐type Chemical Warfare Nerve Agents via Analytical Supercritical Fluid Chromatography

Chemical warfare nerve agents (CWNAs) are extremely toxic organophosphorus compounds that contain a chiral phosphorus center. Undirected synthesis of G‐type CWNAs produces stereoisomers of tabun, sarin, soman, and cyclosarin (GA, GB, GD, and GF, respectively). Analytical‐scale methods were developed using a supercritical fluid chromatography (SFC) system in tandem with a mass spectrometer for the separation, quantitation, and isolation of individual stereoisomers of GA, GB, GD, and GF. Screening various chiral stationary phases (CSPs) for the capacity to provide full baseline separation of the CWNAs revealed that a Regis WhelkO1 (SS) column was capable of separating the enantiomers of GA, GB, and GF, with elution of the P(+) enantiomer preceding elution of the corresponding P(–) enantiomer; two WhelkO1 (SS) columns had to be connected in series to achieve complete baseline resolution. The four diastereomers of GD were also resolved using two tandem WhelkO1 (SS) columns, with complete baseline separation of the two P(+) epimers. A single WhelkO1 (RR) column with inverse stereochemistry resulted in baseline separation of the GD P(–) epimers. The analytical methods described can be scaled to allow isolation of individual stereoisomers to assist in screening and development of countermeasures to organophosphorus nerve agents. Chirality 26:817–824, 2014. © 2014 The Authors. Chirality published by John Wiley Periodicals, Inc.     

ORIGINAL ARTICLE: Evaluation of miosis,behavior and cholinesterase inhibition from low‐level,whole‐body vapor exposure to soman in African green monkeys (Chlorocebus sabeus)*

Background Relatively little is known about the effects of very low‐level exposures to nerve agents where few signs or symptoms are present. Methods African green monkeys (Chlorocebus sabeus) (n = 8) were exposed for 10 min, whole‐body, to a single concentration of soman (0.028–0.891 mg/m³). Results EC₅₀ values for miosis were determined to be 0.055 mg/m³ and 0.132 mg/m³ when defined as a 50 percent reduction in pupil area and diameter, respectively. In general, performance on a serial probe recognition task remained unchanged at lower concentrations, but responding was suppressed at the largest concentration tested. Soman produced concentration‐dependent inhibition of acetylcholinesterase activity and, to a lesser extent, butyrylcholinesterase activity. Conclusions These results characterize threshold soman exposure concentrations that produce miosis in the absence of other overt signs of toxicity and extend previous studies indicating that miosis is a valuable early indicator for the detection of soman vapor exposure.     

索曼和吗啡对猫膈神经和肋间外神经放电的影响

在乌拉坦氯醛糖混合麻醉猫上,平静呼吸时膈神经和肋间外神经α纤维单纤维放电时程、冲动数、冲动频率及休止期经统计处理无明显差别。切断双侧迷走神经后呼吸深慢,两种神经的冲动频率升高、放电时程延长及冲动数增多。窒息时两种神经电活动先增强,然后同时停止活动。索曼0.2—3μg 椎动脉或10—20μg/kg 静脉注射后,主要抑制膈神经放电的占85%和87%,无主要抑制肋间外神经的反应。椎动脉注射吗啡0.5—5mg,主要抑制肋间外神经放电的反应则占58%,无抑制膈神经放电的反应。从膈神经元所在的颈髓局部浸润索曼不能停止膈神经节律吸气放电。以上结果表明,主要支配膈神经的延髓呼吸神经元背侧组(DRG)和主要支配肋间外神经的腹侧组(VRG)在平静呼吸时活动无明显差异。而索曼和吗啡可使这两个细胞核团表现不同的反应。     

氨基酸分析法快速测定梭曼中毒后大鼠脑组织中兴奋性氨基酸的含量

建立一种快速、准确、可靠的脑内兴奋性氨基酸定量检测方法 ,并观察梭曼惊厥后大鼠脑组织中兴奋性氨基酸(EAAs)含量变化。采用 6 30 0黄金系统氨基酸分析仪 ,在锂柱 130min程序生理体液分析方法基础上 ,根据兴奋性氨基酸(EAAs)的特性 ,建立了EAAs的快速测定方法 ,并用此方法对梭曼惊厥后不同时相大鼠的新鲜脑组织进行定位检测。梭曼诱发惊厥后大脑皮质和海马内谷氨酸和天冬门氨酸水平显著下降。惊厥 30min时谷氨酸下降最明显 ,分别是正常组的 5 3.2 %和 5 2 .8%。天门冬氨酸更易受梭曼中毒的影响 ,惊厥后 5、30、90min 3个时相点测定值均显著下降。此方法完成谷氨酸和天门冬氨酸分析的时间是 2 0min ,比原方法缩短了 110min ;且有较好的重现性 (GluCV :日内 1.86 % ,日间 2 .32 % ;AspCV :日内 1.42 ,日间 2 .48% )和回收率 (Glu 97.7% ;Asp97.3% )。兴奋性氨基酸参与了梭曼中毒性惊厥的病理生理过程。本方法定量检测兴奋性氨基酸快速、准确 ,并利于大批量样品的快速测定     

Scanning cytophotometric analysis of myocardial nucleic acid and chromatin changes in soman toxicated rabbits

Myocardial nucleic acid responses were analysed in New Zealand White rabbits 20 min-1 h and 6-8 h following single subcutaneous injections of soman (20, 30, or 40 micrograms kg-1). Scanning-integrating microdensitometry was used to quantify Azure B-RNA and Feulgen-DNA (F-DNA) levels, and changes in the susceptibility of chromatin to Feulgen acid hydrolysis (F-DNA reactivity) of individual ventricular myocardial cells. With a dosage of 20 micrograms kg-1 soman, no RNA alterations were evidenced at 1 h whereas at 6-8 h myocardial cells exhibited higher RNA levels and an increase in F-DNA reactivity of chromatin. With dosages of 30 and 40 micrograms kg-1 soman there was an augmentation in RNA levels and in the acid hydrolysability of nuclear chromatin at both 20 min-1 h and 6-8 h. It is postulated that the observed cellular transformations represent a compensatory augmentation in myocardial metabolic functioning presumably in response to an increased functional demand on the ventricular myocardium. The absence of cytopathic or cytochemical evidence of impairment in nucleic acid metabolism is inconsistent with the premise that soman exerts direct cytotoxic effects on rabbit myocardium.     

The MASCA Approach Applied to Break Multicollinearities in Quantitative Structure-Activity Relationships

Since the regressors in multiple and multivariate regression analysis are intercorrelated, the coefficients of a regression of regressands on them are unreliable with respect to the predictive model power. Nonpredictive and predictive multicollinearity affect the ability to predict the biological activity (regressand) of novel drugs based on a function of physiochemical parameters (regressors), therefore. The nonpredictive multicollinearity can be broken by using the principal component regression analysis of the MASCA model. The working technique is exemplified on bispyridinium oxime antidotes, trimethoprim derivatives, and Taft's steric constant.