The delayed neuropathic effects of nerve agents and some other organophosphorus compounds

The in vitro inhibitory potencies of several nerve agents and other organophosphorus compounds against acetylcholinesterase (AChE) and neurotoxic esterase (NTE) have been compared. Although the I₅₀s against AChE were about 0.1–1.0 nM for the nerve agents the I₅₀s against NTE for sarin, soman and tabun were two to four orders of magnitude higher and VX had negligible activity. A series of bis[(ω-phenyl-n-alkyl]phosphorofluoridates inhibited both enzymes at 1.0–100 nM while ω-phenyl-n-alkyl NN-dimethylphosphoramidofluoridates were active at 0.1–10 μM. From the in vitro data it was predicted that nerve agents would cause delayed neuropathy only at doses greatly exceeding the LD₅₀. In hens protected against acute toxicity by pretreatment with physostigmine, atropine and the oxime P2S, delayed neuropathy associated with high inhibition of NTE was found at 30–60 × LD₅₀ for sarin but not at 38 × LD₅₀ for soman or 82 × LD₅₀ for tabun. At the maximum doses tested of the latter two compounds the inhibition of NTE was 55% and 66% respectively. The minimum neuropathic doses were calculated to be about 100–150 × LD₅₀ for soman and tabun. As expected from in vitro data, neuropathy, associated with a high level of inhibition of NTE, was caused by one of the bis-phenylalkyl phosphorofluoridates at doses causing negligible acute toxicity. The required dose was 9X that for DFP although the compound was 300X more active against NTE in vitro suggesting that such compounds are rapidly degraded in vivo. The phenylalkyl NN-dimethylphosphoramidofluoridates produced prolonged acute signs of poisoning but they were not neuropathic at the maximum tolerable doses nor was the NTE greatly inhibited contrary to the prediction from the in vitro data. It is possible that the enantiomer responsible for the inhibition of NTE is preferentially degraded in vivo. Several other phosphoramidofluoridates inhibit NTE in vitro at 1.0–100 μM and a number of bicyclic phosphates were inactive at 23 μM. None of these compounds was tested in vivo.     

Phosphonylated tyrosine and lysine residues as biomarkers of local exposure of human hair to the organophosphorus nerve agents sarin and VX

We herein present for the first time a micro liquid chromatography-electrospray ionization high-resolution tandem-mass spectrometry (μLC-ESI MS/HR MS) procedure to detect phosphonylated tyrosine (Tyr) and lysine (Lys) residues obtained from human hair exposed to organophosphorus nerve agents (OPNA). In general, toxic OPNA react with endogenous blood proteins causing the formation of adducts representing well-known targets for biomedical analysis to prove exposure. In contrast, no protein-derived biomarker has been introduced so far to document local exposure of hair. Accordingly, we developed and characterized a μLC-ESI MS/HR MS method for the analysis of scalp hair exposed to OPNA in vitro. Type I and Type II keratin from hair was dissolved during lysis, precipitated and subjected to pronase-catalyzed hydrolysis yielding single adducted Lys and in a much higher amount Tyr residues. Exposure to sarin caused the adduction of an isopropyl methylphosphonic acid moiety and exposure to VX yielded adducts of ethyl methylphosphonic acid, well suited as biomarkers of exposure. These were of appropriate stability in the autosampler for 24 h. The biomarker yield obtained from hair of six individuals as well as from hair of six different parts of the body of one individual (armpit, beard, leg, arm, scalp, and pubic) differed reasonably indicating the variable individual protein composition and structure of hair. Exposed hair stored at ambient temperature for 9 weeks with contact to air and daylight showed stability of all adducts and therefore their suitability for verification of exposure.     

Efficacy of biperiden and atropine as anticonvulsant treatment for organophosphorus nerve agent intoxication

The ability of the nerve agents tabun, sarin, soman, GF, VR, and VX to produce brain seizures and the effectiveness of the anticholinergics biperiden HCl or atropine SO₄ as an anticonvulsant treatment were studied in a guinea-pig model. All animals were implanted a week prior to the experiment with cortical electrodes for electroencephalogram (EEG) recordings. On the day of exposure, the animals were pretreated with pyridostigmine (0.026 mg/kg, i.m.) 30 min prior to challenge with a 2 × LD₅₀ dose (s.c.) of a given agent. In separate experiments, animals were challenged with 5 × LD₅₀ (sc) of soman. One minute after agent challenge, the animals were treated intramuscularly (i.m.) with 2 mg/kg atropine SO₄ admixed with 25 mg/kg 2-PAM Cl and then observed for the onset of seizure activity. Five minutes after the start of nerve agent-induced EEG seizures, animals were treated i.m. with different doses of biperiden HCl or atropine SO₄ and observed for seizure termination. The anticonvulsant ED₅₀ of biperiden HCl and atropine SO₄ for termination of seizures induced by each nerve agent was calculated and compared. With equally toxic doses (2 × LD₅₀) of these agents, continuous EEG seizures (status epilepticus) developed in all animals challenged with soman, tabun, or VR, and in more than 90% of the animals challenged with GF or sarin. In contrast, only 50% of the animals developed seizures when challenged with VX. The times to onset of seizures for soman, tabun, GF, and sarin were very similar (5–8 min) while for VR, it was about 10 min. In the case of VX, not only was the time to seizure development longer (20.7 min), but the seizure activity in 19% of the animals terminated spontaneously within 5 min after onset and did not return. Under these conditions, the anticonvulsant ED₅₀s of biperiden HCl for soman, GF, VR, tabun, sarin, and VX were 0.57, 0.51, 0.41, 0.2, 0.1, and 0.09 mg/kg, respectively, while those of atropine SO₄ for soman, VR, tabun, GF, sarin, and VX were 12.2, 11.9, 10.4, 10.3, 5.1, and 4.1 mg/kg, respectively. In separate experiments, the anticonvulsant ED₅₀ doses of biperiden for animals challenged with 2 or 5 × LD₅₀ of soman were 0.48 (95% confidence limits 0.25–0.73) or 0.57 (95% CI 0.38–0.84) mg/kg, respectively, while the anticonvulsant ED₅₀s for atropine (12.2 mg/kg, i.m.) were identical under these same two challenge conditions. The present study demonstrates that all nerve agents can produce status epilepticus and that the therapeutic effectiveness of atropine and biperiden roughly paralleled the seizurogenic potential of these agents. Received: 16 November 1999 / Accepted: 9 February 2000     

Determination of alkylmethylphosphonic acids, the main metabolites of organophosphorus nerve agents, in biofluids by gas chromatography-mass spectrometry and liquid-liquid-solid-phase-transfer-catalyzed pentafluorobenzylation

A simple gas chromatography-mass spectrometry (GC-MS) procedure has been developed for the main metabolites of organophosphorus nerve agents, alkylmethylphosphonic acids (AMPAs; alkyl = Et, i-Pr, and pinacolyl) in biofluids via extractive pentafluorobenzylation. The derivatization was carried out under liquid-liquid-solid-phase-transfer conditions using a polymer-bound tri-n-butylmethylphosphonium bromide as a catalyst. AMPAs in aqueous samples were semiquantitatively extracted into a small-volume organic layer as their pentafluorobenzyl derivatives at pH 4.5 (85 degrees C). Sample pretreatments for urine, serum, and saliva were each examined to minimize matrix interference. The detection limits of APMAs by electron-impact ionization GC-MS were around 50 ng/mL and 2.5-10 ng/mL in the full-scan and selected-ion monitoring modes, respectively. In order to detect trace-level AMPAs, negative-ion chemical ionization (NICI) was also employed to enhance sensitivity. The detection limits of AMPAs in biofluids were typically 60 pg/mL by GC-NICI-MS.     

Probes for vasopressin receptors Attachment of affinity and fluorescent groups in vasopressin

Fluorescent, photoreactive, and biotinylated analogs of vasopressin have been prepared in which one of these three groups has been attached to a reactive amino group in either position 4 or position 7. Using solid phase methodology, we have synthesized two active parent compounds, [l-desamino,4-lysine,7-hydroxy-prolinelarginine vasopressin and [l-desamino,7-aminoproline]arginine vasopressin, and acylated them to obtain biotinyl, azidobenzoyl, and fluoresceinyl derivatives. We have also prepared analogs in which a “spacer arm” was inserted between lysine in position 4 and the marker group. Some of these derivatives have good antidiuretic activity and could be valuable probes in studying hormone-receptor interaction and in receptor visualization and purification.     

一种新的快速简便的抗肿瘤药物筛选模型

本研究利用DNA修复缺陷的大肠埃希氏菌343/591和正常的大肠埃希氏菌343/636的差异性DNA修复特性,建立了液体悬浮法和琼脂固体筛选方法,用于抗肿瘤药物的筛选。这两种方法简单易行,其中琼脂固体筛选方法与抗生素生物鉴定杯碟法一样简单,适合于大量筛选各种来源的抗肿瘤药物。     

Analytical approaches for monitoring exposure to organophosphorus and carbamate agents through analysis of protein adducts

Appropriate treatment of a poisoned patient requires knowing the identity of the poison. This review summarizes the methods for identifying poisoning by organophosphorus and carbamate poisons. Mass spectrometry methods identify the poison from the adducts they form with proteins in blood. The most sensitive method uses potassium fluoride to release the organophosphorus agent from its covalent binding to serine 198 of human butyrylcholinesterase. The released poison is identified by gas chromatography-mass spectrometry. The drawback of this method is that it does not detect exposure to agents such as soman, because butyrylcholinesterase adducts with these agents age to a non-reactivatable form. A method that detects both aged and non-aged organophosphylated adducts as well as carbamate adducts is one that digests butyrylcholinesterase with a protease and analyzes the modified peptide by mass spectrometry. This method does not distinguish between poisons that have the same mass after reaction with butyrylcholinesterase--for example, between exposure to chlorpyrifos oxon and paraoxon. Albumin forms a stable, covalent bond with organophosphates on tyrosine 411. The rate of reaction with albumin is much slower than with butyrylcholinesterase, but albumin adducts persist for a longer time in the circulation; they do not age; and they do not release the organophosphate when a patient is treated with an oxime.     

Use of high-content analysis for compound screening and target selection

High-content analysis (HCA) has rapidly established itself as a core technology in drug discovery for secondary cell-based screening. When combined with our knowledge of genetics, HCA can provide a powerful tool for target validation, but excitingly, HCA may also enable the increased use of cellular assays in high-throughput screening for novel drug leads.     

In vivo microdialysis and electroencephalographic activity in freely moving guinea pigs exposed to organophosphorus nerve agents sarin and VX: analysis of acetylcholine and glutamate

Organophosphorus nerve agents such as sarin (GB) and VX irreversibly inhibit acetylcholinesterase, causing a buildup of acetylcholine (ACh) in synapses and neuromuscular junctions, which leads to excess bronchial secretions, convulsions, seizures, coma, and death. Understanding the unique toxic characteristics of different nerve agents is vital in the effort to develop broad spectrum medical countermeasures. To this end, we employed a repeated measure multivariate design with striatal microdialysis collection and high-performance liquid chromatography analysis to measure changes in concentrations of several neurotransmitters (ACh, glutamate, aspartate, GABA) in the same samples during acute exposure to GB or VX in freely moving guinea pigs. Concurrent with microdialysis collection, we used cortical electrodes to monitor brain seizure activity. This robust double multivariate design provides greater fidelity when comparing data while also reducing the required number of subjects. No correlation between nerve agents’ propensity for causing seizure and seizure-related lethality was observed. The GB seizure group experienced more rapid and severe cholinergic toxicity and lethality than that of the VX seizure group. Seizures generated from GB and VX exposure resulted in further elevation of ACh level and then a gradual return to baseline. Glutamate levels increased in the GB, but not in the VX, seizure group. There were no consistent changes in either aspartate or GABA as a result of either nerve agent. These observations reinforce findings with other nerve agents that seizure activity per se contributes to the elevated levels of brain ACh observed after nerve agent exposure.     

Neurotoxicity of organophosphorus pesticides: predictions can be based on in vitro studies with hen and human enzymes

The comparative inhibitory power of organophosphorus esters in vitro against hen brain acetylcholinesterase and neurotoxic esterase correlates with their comparative effects (death or delayed neuropathy) in vivo. Further comparisons of the in vitro effects seen with hen and human enzymes facilitates extrapolations to the human in vivo situation.Visiting worker from Istituto di Medicina del Lavoro. Universita di Padova (Italy)     

Researches on antibacterial and antifungal agents, XII: Analogues of bifonazole with two imidazole moieties and related azoles

Analogues of bifonazole bearing two imidazole rings and other related azoles have been synthesized and tested as antifungal agents against Candida albicans and Candida spp.. Only a slight part of the antifungal power of the parent drug is retained by some derivatives as evinced by the comparison of new compounds with bifonazole, miconazole, and ketoconazole.     

Mouse strain-dependent hepatic interaction of psychoactive agents with ethanol and biogenic aldehydes metabolizing enzymes

The effect of multiple dose regimens of amantadine, reserpine, chlorpromazine alone or combined on liver alcohol (L-ADH) and aldehyde dehydrogenase (L-ALDH) was studied in three strains of mice. A strain-dependent difference between endogenous specific activity of these enzymes and their sensitivity to the agents studied was determined. The C₅₇BL/6 mice showed most resistance to drug effect and possessed greater activity of mitochondrial L-ALDH isoenzymes and L-ADH than either ICR or BALB/C mouse strains, respectively. Amantadine induced both L-ADH and mitochondrial L-ALDH while reserpine inhibited them also as a function of mouse strain. Both reserpine-and chlorpromazine-mediated inhibition of albino ICR mouse L-ADH and BALB/C mitochondrial L-ALDH was alleviated by pretreatment with amantadine. This indicates antagonism between amantadine and these agents. The results suggest a genotypic sensitivity to drug action which may explain the individual sensitivity to the development of chlorpromazine and reserpine-produced side-effects, and the potency of amantadine in management of such drug-induced adverse reactions.     

Alkylation activity and molecular properties of two antineoplastic agents that utilise indometacin and a conjugate of aspirin with 2-aminonicotinic acid to transport nitrogen mustard groups

BACKGROUND: Nitrogen mustard (N-mustard) compounds are considered important anticancer drugs. Various transporting agents have been utilised to carry N-mustard groups including coumarins, amides, polyaromatic molecules and cycloalkyl structures. N-mustards act as bifunctional alkylating agents that induce cross-linking within DNA strands and cytotoxic activity. Compounds that transport the N-mustard group in vivo can also express drug-likeness that can have advantages in clinical application. This study presents data on two anticancer drugs with N-mustard groups covalently attached to NSAIDs. METHODS: Two alkylating compounds were synthesised by covalently attaching a single N-mustard group to 2-2-acetoxybenzoylaminonicotinic acid (for compound I) and indometacin (for compound II). Molecular properties such as aqueous solubility, 1-octanol/water partitioning coefficient (log Kow), molar volume, polar surface area, 1-octanol/water partitioning at pH values other than human blood (log D) and the dermal permeability coefficient (Kp) were determined. The rate-order of reaction and rate constant of alkylation were determined by reacting compound I and compound II with a target compound having a primary amine group in buffered aqueous solution at blood pH 7.4 and 37 masculineC, and monitoring absorbance at 400nm. RESULTS AND C onclusion: Compounds I and II were stable at room temperature, soluble in water and effectively alkylated a nucleophilic primary amine target at physiological temperature and pH. The water solubility of compound I was considerably greater than that of compound II. Both compounds showed second-order rate order of alkylation and effectively alkylated a nucleophilic target under aqueous physiological conditions of pH 7.4 and 37 masculineC. Kp values for compounds I and II were determined to be 0.000786 cm/h and 0.024 cm/h, respectively. Both compound I and compound II had zero percent ionisation at pH 7.4, and compound I showed zero violations of the Rule of 5. Log P values for compounds I and II were 3.27 and 5.08, respectively. This study describes the benefits of antineoplastic agents with NSAID substituents that provide favourable pharmacological properties.     

青岛泊子盐场放线菌多样性及其功能酶的筛选--测试文章

采用平板涂布法利用3种培养基从青岛即墨市田横镇泊子盐场盐池底泥样中共分离纯化出15株放线菌,对分离菌株进行16S rRNA基因测序分析。发现这15株放线菌分属于链霉菌属(Streptomyces)、拟诺卡氏菌属(Nocardiopsis)和1个新属,其中Streptomyces属为优势菌属;菌株CXB832与Nocardiopsis arabia DSM 45083^T和Haloactinospora albus DSM 45015^T最接近,同源性分别为95.4%和94.9%,根据其表型和分子特征可以初步判定该菌株为放线菌新属。培养基及培养温度对盐池环境中放线菌的分离效果均有影响,利用淀粉酪素培养基在37℃分离的放线菌种类和数量较多。在15株放线菌中,分别有12株、3株、2株和1株放线菌产淀粉酶、酯酶、蛋白酶和纤维素酶。     

Synthesis and characterization of fluorescent ligands for the norepinephrine transporter: potential neuroblastoma imaging agents.

Radiolabeled m-iodobenzylguanidine (MIBG) is a tumor-seeking radioactive drug used in the diagnosis and treatment of pheochromocytomas and neuroblastomas. It is transported into the tumor cells by the neuronal norepinephrine (NE) transporter (NET) which is expressed in almost all neuroblastoma cells. Here, we describe the synthesis and some pharmacological properties of a series of fluorescent compounds structurally related to the NET substrate, MIBG, or to the NET inhibitors, (-)-(2R,3S)-cocaine and nisoxetine. Three of 10 synthesized fluorescent compounds, 1-(1-naphthylmethyl)guanidinium sulfate (1), 1-[2-(dibenz[b, f]azepin-5-yl)ethyl]guanidinium sulfate (2), and (2R, 3S)-2beta-ethoxycarbonyl-3beta-tropanyl 5-(dimethylamino)naphthalene-1-sulfonate (6), exhibited high affinity (IC(50) about 50 nM) for the NET. The nisoxetine derivatives 8 (rac-N-[(3-methylamino-1-phenyl)propyl]-5-(dimethylamino)-1-naphthale nesulfonamide) and 9 (rac-4-[(3-methylamino-1-phenyl)propyl]amino-7-nitro-2,1, 3-benzoxadiazole) and especially the guanidine derivative 4 (1-[4-(4-phenyl-1,3-butadienyl)benzyl]guanidinium sulfate) which are characterized by intermediate affinity for the NET (IC(50) 370-850 nM) caused significant and nisoxetine-sensitive cell fluorescence. At least the guanidine derivative 4 might represent a potentially useful agent for imaging of neuroblastoma cells.     

Mechanism of action of key enzymes associated with cancer propagation and their inhibition by various chemotherapeutic agents

The propagation of cancer, which is basically the consequence of uncontrolled multiplication of cells, is a complicated process involving the participation of a number of enzymes. The molecular level understanding of the chemistry of these enzymes is the starting step towards the development of anti-cancer drugs and a collective view of these enzymes (responsible for cell multiplication) could help in the development of multiple target ligands. In this review, the mechanistic chemistry of the key enzymes viz. ribonucleotide reductase, thymidylate synthase, thymidylate phosphorylase, topoisomerase II, closely involved at various stages of cell multiplication and hence responsible for the propagation of cancer, and some of their suitable inhibitors have been discussed. Further, this review will elucidate the chemistry of lactate dehydrogenase and cyclooxygenase, the enzymes responsible for providing the extra energy to the cancer cells and initiating the growth of tumors through the formation of mutagens, respectively.