Perturbations induced by malathion, methylparathion and parathion on the physicochemical properties of dipalmitoylphosphatidylcholine (DPPC) were studied by fluorescence anisotropy of DPH and DPH-PA and by differential scanning calorimetry (DSC). Methylparathion and parathion (50 [mu]M) increased the fluorescence anisotropy evaluated by DPH-PA and DPH, either in gel or in the fluid phase of DPPC bilayers, but mainly in the fluid phase. Parathion is more effective than methylparathion. On the other hand, malathion had almost no effect. All the three xenobiotics displaced the phase transition midpoint to lower temperature values and broadened the phase transition profile of DPPC, the effectiveness following the sequence: parathion>methylparathion>>malathion. A shifting and broadening of the phase transition was also observed by DSC. Furthermore, at methylparathion/lipid molar ratio of 1/2 and at parathion/lipid molar ratio of 1/7, the DSC thermograms displayed a shoulder in the main peak, in the low temperature side, suggesting coexistence of phases. For higher ratios, the phase transition profile becomes sharp as the control transition, but the midpoint is shifted to the previous shoulder position. Conversely to methylparathion and parathion...
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Processo FAPESP: 09/51048-8; Processo FAPESP: 12/00168-6; Organophosphorus-induced delayed neuropathy (OPIDN) is a neurodegenerative disorder characterised by ataxia progressing to paralysis with concomitant central and peripheral distal axonopathy. Symptoms of OPIDN in people include tingling of the hands and feet. This tingling is followed by sensory loss, progressive muscle weakness and flaccidity of the distal skeletal muscles of the lower and upper extremities and ataxia, which appear about 8-14 days after exposure. Some organophosphorus compounds (OPs) that are still used in worldwide agriculture have potential to induce OPIDN, including methamidophos, trichlorfon, dichlorvos and chorpyrifos. This review summarizes experimental attempts to prevent and/or treat OPIDN and the different mechanisms involved in each approach. The initial mechanism associated with development of OPIDN is phosphorylation and inhibition of neuropathy target esterase (NTE). The phosphorylated enzyme undergoes a second reaction known as aging that results in the loss of one of the R groups bound to the phosphorus of the OP. A second mechanism involved in OPIDN is an imbalance in calcium homeostasis. This can lead to the activation of calcium-activated neutral protease and increases in calcium/calmodulin-dependent protein kinases. These events contribute to aberrant phosphorylation of cytoskeletal proteins and protein digestion in the terminal axon that can proceed similarly to Wallerian-type degeneration. Several experimental studies demonstrated alleviation of the signs and symptoms of OPIDN by restoring calcium balance. Other studies have used preadministration of NTE inhibitors...
A simple and rapid method for the determination of 13 organophosphorus insecticides and their metabolites in olive oil by GC is described. The pesticide was extracted from oil with acetonitrile and no cleanup was needed. GC-nitrogen-phosphorus detection response factors of pesticides were affected by solvents and coextractive substances. Pesticides in hexane showed on average higher response factors. Standards were prepared in the residue-free oil extract solubilized in hexane to handle effects of matrix and solvent. The low amount of coextractive substances does not decrease the column efficiency, even after a few hundred analyses. Recovery at three fortification levels (ca. 0.1, 1.0 and 3.0 mg/kg) ranged from 74 to 118%, With coefficients of variation ranging from 1 to 16.
This paper is a review of the history, synthesis and application of organophosphorus compounds, especially of those of pentavalent phosphorus, such as phosphoramidates, phosphorothioates, phosphonates and phosphonic acids with insecticide and anticancer activities. The organophosphorus compounds with agrochemical applications show great structural variety, They include not only insecticides, but also fungicides, herbicides, and others. The large variety of commercially available organophosphorus pesticides is remarkable. Even more interesting is the high efficiency of some organophosphorus compounds as anticancer agents such as cyclophosphamide and its derivatives.
Reaction of Li(P3C2Bu t2 ) with BrCH(SiMe3)2 results in a novel organophosphorus compound with the formula, P6C4Bu t4 CHSiMe3 (1). Compound 1 was fully characterised spectroscopically and its unique molecular structure determined by single crystal X-ray diffraction. Another isomer (2) with a saturated structure was also fully characterised.
Chemical warfare agents constitute one of the greatest threats in the modern world. Among them, the neurotoxic agents are of special interest due to their high lethality and danger. Neurotoxic agents are organophosphorus compounds that act by inhibiting the enzyme acetylcholinesterase, which is fundamental for the control of transmission of nervous impulses. There are several ways of treating intoxication by organophosphorus compounds, but none of them is efficient against all the known neurotoxic agents or against all of their effects. This review focus on the use of organophosphorus compounds as neurotoxic chemical warfare agents. After a brief historical introduction, it will be done a discussion about the structural and biological characteristics of acetylcholinesterase, followed by a review of the properties of organophosphorus compounds and their application as chemical warfare agents. Finally, the ways of treatment against intoxication with these agents will be discussed, with emphasis on the oximes used for reactivating the inhibited acetylcholinesterase.
1. Organophosphorus compounds that produce a delayed neurotoxic effect in hens phosphorylate a specific site in the brain soon after administration. 2. Phosphorylation of the specific site by di-isopropyl [32P]phosphorofluoridate in vitro is blocked by the prior addition of phenyl phenylacetate. 3. A small proportion of the total activity of hen brain hydrolysing phenyl phenylacetate in vitro was shown to be due to an enzyme different from two others previously described. 4. This enzyme is only slightly inhibited in vitro by concentrations of tetraethyl pyrophosphate and paraoxon (diethyl 4-nitrophenyl phosphate) up to 64μm and is completely inhibited by 6μm-di-isopropyl phosphorofluoridate and 128μm-mipafox. 5. It is also inhibited in vivo by effective doses of neurotoxic organophosphorus compounds but not by high doses of non-neurotoxic analogues. 6. It is deduced that the active site of this enzyme is the phosphorylation site associated with the genesis of delayed neurotoxicity.
1. It is proposed that part of a neurotoxic dose of di-isopropyl phosphorofluoridate will be covalently bound in vivo to a specific component in the brain and spinal cord as the initial biochemical event in the genesis of the lesion. 2. A test system in vitro was devised that removes many di-isopropyl phosphorofluoridate-binding sites and indicates that the specific component may be a protein present in brain at a concentration comparable with that of the cholinesterases. 3. The site was found to be present and capable of binding di-isopropyl phosphorofluoridate in vitro in brain samples taken from either normal hens or those dosed with organophosphorus esterase inhibitors that are not neurotoxic. 4. Very little of the specific binding activity was found in brain samples from hens pre-dosed with a variety of neurotoxic organophosphorus compounds. 5. A solubilized preparation of the active brain component was obtained, suitable for further purification and study.
Thirty-six alkyl organophosphorus compounds have been tested for neurotoxicity in the chicken. The individual compounds were chosen to enable the importance of each portion of the molecule to be assessed in relation to the property of neurotoxicity. Seventeen substances were found to be neurotoxic, fifteen for the first time. All of these contained fluorine. On the basis of the results reported, certain predictions have been made about the chemical structure of compounds which would be expected to be neurotoxic. The importance of fluorine suggests that it plays a direct role in the development of the biochemical lesion, and this may occur as the result of its being carried by the molecule as a whole to specific areas in the nervous system. By the action of cholinesterase, the P-F bond may be ruptured and ionic fluorine liberated where it blocks some metabolic cycle.
This paper outlines our knowledge of the reaction of organophosphorus compounds and carbamates with esterases, examples of particular aspects of the reaction being confined to cholinesterases, although the general principles discussed apply to all B-esterases. Mathematical expressions are given for the different rate constants, and some of the factors that may affect the response of insect and mammalian cholinesterases to organophosphorus compounds and carbamates are discussed.
The clinical manifestations of acute poisoning by organophosphorus compounds in man are in accord with, initially, the stimulation and, later, the blocking of cholinergic transmission due to acetylcholinesterase inhibition. The manifestations involve mainly the para-sympathetic nerves, the neuromuscular junctions, and the central nerve synapses, and to a smaller degree the cholinergic sympathetic nerves. Miosis and muscle fasciculations are useful signs for diagnosis and for the control of therapy. Blood cholinesterase determination is the best diagnostic test. The cause of death is usually respiratory paralysis. Persistent manifestations have not been confirmed. Atropine and pralidoxime are effective for treatment and useful for diagnosis. Other oximes are promising but their clinical value has not been established. Poisoning by malathion is characterized by a prolonged course and by motor signs. Poisoning by organophosphorus compounds in man differs from animal experiments in several ways: in man, exposure may occur by several different routes, the manifestations are detected more easily, and therapy is given throughout the course of illness.
This paper reviews the toxicity of organophosphorus compounds in relation to cholinesterase inhibition in insects. It covers anticholinesterase effects on different stages of the life cycle and the relationship between cholinesterase inhibition and lethality. Other effects of organophosphorus compounds, which may account for anomalies in insecticidal action, are also considered.
The general types of biological reaction that are most prominent in the modification of organophosphorus compounds involve the mixed-function oxidases, hydrolases, or transferases. In certain cases, more than one of these reactions may be involved at the same site on the pesticide molecule. Examples of various organophosphorus pesticides that are altered by oxidation, hydrolysis, alkyl- or aryl-group transfer, reduction, and conjugation are discussed. The increase or decrease in toxicity of a pesticide that can result from biological modification is emphasized.
The acute toxicity of most of the commonly used organophosphorus insecticides is essentially the same. A few compounds with low toxicity, such as malathion, have been developed but further efforts in that direction are needed. Most of the organophosphorus insecticides exert a generalized cholinergic action by inhibiting central and peripheral cholinesterases. The phosphoramides are an exception in that they do not gain access to the cholinesterase of the central nervous system in vivo and consequently atropine is a more effective antidote for them than for organophosphorus compounds. Young animals are more susceptible to the organophosphorus compounds than are adults. Enzyme-inducing agents decrease the toxicity of the phosphorothioates and phosphorodithioates. All organophosphorus insecticides can inhibit esterases that catalyse the detoxification of some insecticides of this class and ester-type drugs.
The authors have evaluated a number of organophosphorus compounds for residual contact toxicity to adult Anopheles stephensi. Fenthion and malathion were the most promising of the compounds, and wettable powder deposits at a dosage of 1 g/m2 on plywood remained effective for five months. There was, however, a rapid loss of effectiveness on dried mud bricks stored at 25°C and 50%-55% relative humidity.
From literature data on partition coefficients and in some cases solubilities in nonaqueous solvents we have been able to determine Abraham descriptors for several series of organophosphorus compounds including the dialkyl- and diaryl-phosphates (dialkylphosphoric acids), trialkyl- and triphenyl-phosphates, dialkylphosphinic acids and diphenylphosphinic acid, trialkyl- and triaryl-phosphine oxides, and dialkylphosphites and triarylphosphines. Other organophosphorus compounds studied were dimethyl methylphosphonate and the flame retardant PBMP. For all these compounds, knowledge of the Abraham descriptors enables partition coefficients to be predicted for transfer from water to over 40 (wet) solvents. If the solubility of a given compound in just one dry solvent (out of a list of 47 dry solvents) is available, then the solubility in all the other listed dry solvents can be predicted through very simple equations.
Studies the structure and reactivity of organic, organosilicon and organophosphorus anions in the gas phase. Theoretical ab initio calculations and collisional activation in a reverse geometry mass spectrometer revealed structural information and reactivity was probed using the flowing afterglow reactor.; Thesis (Ph.D.)--University of Adelaide, Dept. of Organic Chemistry, 1991; Copies of author's previously published articles inserted.; Includes bibliographical references (leaves 193-215); xiv, 216 leaves : ill. ; 30 cm.; Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Nineteen dialkylphosphorylhydrazones with different substituents at the aromatic ring were evaluated as potential tyrosinase inhibitors, which could then be used as efficient agents in the control of pigmentation disorders. The inhibition activity was measured by a modified Patil and Zucker UV-Vis method. Briefly, the assays were carried out with solutions containing phosphate buffer, L-3,4-dihidroxyphenylalanine (L-DOPA), (EDTA), tyrosinase and varying concentrations of organophosphorus compounds. The formation of dopachromone was determined by monitoring the absorbance at 475 nm. Three compounds were found to be the most active compounds of the series (IC50 = 105 ± 20 µmol L-1), (IC50 = 127 ± 16 µmol L-1) and (IC50 = 188 ± 27 µmol L-1), being three to seven times more active than ascorbic acid (IC50 = 730 µmol L-1), used as a standard. The most active compound is only 1.5 times less potent than the commercial kojic acid (IC50 = 69.4 µmol L-1). This study may lead to the discovery of potent agents against very important pigmentation disorders including hyperpigmentation.
BACKGROUND: Poisoning with organophosphorus pesticides (OPs) is an important cause of morbidity and mortality in all parts of the world, particularly developing countries. The case-fatality ratio for pesticide intentional self-poisoning is around 10-20% even when the standard antidotes (atropine, oximes and benzodiazepines) are used. Alternative treatments have been trialled in an attempt to improve outcomes from acute OP poisoning, one of which is plasma alkalinisation. Animal and preliminary human research has suggested benefit from plasma alkalinisation with sodium bicarbonate (NaHCO3) as a treatment for acute OP poisoning. OBJECTIVES: To determine the efficacy of alkalinisation, in particular NaHCO3, for the treatment of acute OP poisoning. SEARCH STRATEGY: We searched MEDLINE (1966-2004), EMBASE (1980-2004), the Controlled Trials Register of the Cochrane Collaboration, Current Awareness in Clinical Toxicology, Info Trac, http://www.google.com.au, and Science Citation Index of studies identified by the previous searches. We also manually reviewed the bibliographies of identified articles and personally contacted experts in the field. SELECTION CRITERIA: Randomised controlled trials and controlled clinical trials of symptomatic patients following acute OP poisoning treated with alkalinisation. The quality of studies and eligibility for inclusion was assessed using criteria by Jadad and Schulz. DATA COLLECTION AND ANALYSIS: Studies were identified and both authors independently extracted data which was recorded on a pre-designed form. Study design...
Os agentes de guerra química ou agentes neurotóxicos são uma perigosa ameaça à população de todo o mundo e merecem uma atenção especial devido a sua alta periculosidade. A maior parte destes agentes são compostos organofosforados (OF) que inibem a acetilcolinesterase (AChE), enzima responsável pelo controle da transmissão dos impulsos nervosos. Ao ser inibida por esses compostos a AChE pode ser reativada, sendo as oximas catiônicas as substâncias mais utilizadas para esse processo. Até o momento não foi encontrado um agente para tratamento de intoxicação por OF que seja eficaz contra todos os agentes de guerra química conhecidos e contra todos os seus efeitos. Dessa forma, este trabalho tem por objetivo fazer uma revisão sobre os OF, sua utilização como agentes de guerra química e o processo de inibição e reativação da AChE, para motivar o desenvolvimento de novos agentes para defesa contra guerra química. DOI: 10.5935/1984-6835.20140042; The chemical warfare agents or neurotoxic agents are an important threat to people all over the world, and deserve special attention because they are highly dangerous. Most of these agents are organophosphorus compounds (OP) that inhibit the enzyme acetylcholinesterase (AChE) which is responsible for controlling the transmission of nerve impulses. To be inhibited by these compounds...