PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “ISOFLUROPHATE”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 271 records · Page 15Linked to original sources
PubMed1993

Quaternary salts of 3,3'-bis-pyridinium monooximes: synthesis and biological activity.

Two new series of asymetrically substituted 3,3'-bis-pyridinium monooximes bridged by oxopropane and propane groups were synthesized and characterized by spectral data and acid dissociation constants (pKas). Both the in vitro reactivation potency, in experiments with lyophilized electric eel acetylcholinesterase (AChE) inhibited by diisopropylfluorophosphate, and in vivo protection efficacy against diisopropylfluorophosphate intoxication in mice of these compounds were evaluated and compared with those of trimedoxime and 2-pyridine-aldoxime methiodide. The compounds were also evaluated for in vitro inhibition of AChE. The compounds with the oxopropane link were stronger inhibitors and weaker reactivators than the corresponding propane derivatives. No significant correlation was observed among pKa, oxime inhibition of AChE, reactivation of inhibited AChE, and protection index. Changing substituents in pyridine rings or altering linking groups between pyridine rings did not improve antidotal efficacy compared with trimedoxime and 2-pyridine-aldoxime methiodide.

Animals↗
PubMed1995

Use of C1300 neuroblastoma cells to evaluate the protective value of hexamethonium, trimethaphan, hemicholinium, and triethylcholine against diisopropyl phosphorofluoridate toxicity.

Our intent was to evaluate the C1300 neuroblastoma cell as an in vitro system for studying the mode of action and efficacy of drugs used to treat or prevent organophosphate intoxication. The anticholinergic drugs hexamethonium, trimethaphan, and hemocholinium and the triethylcholine and cholinesterase/reactivator 2-pyridine aldoxime methochloride (2-PAM) have been shown to be effective in preventing intoxication by diisopropyl phosphorofluoridate (also known as diisopropyl fluorophosphate, DFP) in vivo. We determined their efficacy in preventing cell death (as measured by trypan blue exclusion) of neuroblastoma cells alone or in combination. We also determined their efficacy in reversing the cytotoxic effects of DFP on cell DNA synthesis (as measured by [3H]-thymidine incorporation), cell RNA synthesis (as measured by [3H]uridine incorporation), and on cell protein synthesis (as measured by [3H]leucine incorporation). The maximal nontoxic doses of the drugs in vitro were determined. All anticholinergic agents studied reduced the cytotoxicity of DFP using one or more parameters. 2-PAM, the cholinesterase reactivator, enhanced the cytotoxicity of DFP on cultured cells at a high concentration (1 mg/mL) and reduced it at a lower concentration (0.3 mg/mL). All four anticholinergic agents were capable of enhancing the uptake of [3H]thymidine. Only hexamethonium and hemicholinium reversed DFP inhibition of DNA synthesis. RNA synthesis was not affected by any anticholinergic agent and no agent reversed DFP inhibition of RNA synthesis. Protein synthesis was enhanced by every anticholinergic agent except hemicholinium; the inhibition of protein synthesis by DFP was reversed by trimethaphan and triethylcholine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1982

Erythrocyte survival studies in a rat myelogenous leukemia.

To determine the extent intrinsic erythrocyte defects and/or extrinsic factors were involved in anemia of rats bearing Shay chloroleukemia (SCL), survival of 3H-DFP labeled erythrocytes was studied in leukemic and nonleukemic hosts. Red blood cells labeled before induction of leukemia, were rapidly lost from the peripheral circulation of SCL rats in terminal stages of disease. However, labeled erythrocytes from terminal SCL animals displayed normal lifespans when transfused into nonleukemic controls. Thus the anemia of this leukemia probably resulted from extrinsic factors associated with the leukemic process. Hemorrhage appeared to be primarily responsible for the anemia of this disease.

Anemia↗
PubMed1994

DFP-sensitive multicatalytic protease complexes (proteasomes) involved in the control of oocyte maturation in the toad, Bufo japonicus.

The inhibition of progesterone-induced oocyte maturation by diisopropylfluorophosphate (DFP), a typical serine protease inhibitor, was investigated in oocytes of the Japanese toad Bufo japonicus for the first time. Oocytes to which DFP was externally applied did not undergo germinal vesicle breakdown (GVBD), which is an early signal of oocyte maturation, in response to progesterone. The more inhibitory period was found to be 0-0.5 GVBD50 on a relative time scale [when the time at which 50% of the oocytes had completed GVBD (GVBD50) was set at 1.0], namely, before the beginning of GVBD. DFP-sensitive proteases, which seem to be multifunctional nonlysosomal protease complexes (proteasomes), may already be present in the cytosol of premature oocytes. Peptide hydrolyzing activity, as reflected by proteasome activity, was found to be regulated before and after GVBD. In addition, immunoblotting regarding the native electrophoretic protein profile of the proteasomes throughout the maturational process demonstrated that they undergo alterations in mobility dependent upon the maturational process. These findings raise the possibility that the activities of some endogenous DFP-sensitive proteasomes play distinct, essential roles in oocyte maturation triggered by progesterone in Bufo.

Animals↗
PubMed2006

The electromyographic signal as a presymptomatic indicator of organophosphates in the body.

Organophosphate (OP) compounds are present in household and agricultural pesticides as well as in nerve agents. The toxic effects of these chemicals result from their anticholinesterase activity, which disrupts nerve junctions and parasympathetic effector sites, leading to a variety of symptoms and possible death. When the anticholinesterase agents in OP compounds reach the neuromuscular junction, they cause a disruption in the firing of muscle fiber action potentials. This effect has the potential of altering the time course of the electromyographic (EMG) signal detected by surface electrodes. We investigated the association between OP compound dose, surface EMG changes, and overt signs of OP toxicity. Daily doses of 10-15 microg/kg of diisopropylfluorophosphate (DFP) were injected into the calf muscle of four rhesus monkeys while surface EMG signals were recorded from two thigh muscles bilaterally. With increasing number of doses, the EMG signal presented an increasing number of time gaps. The presence of the gaps was evident prior to any overt symptoms of cholinesterase toxicity. These findings can lead to the development of noninvasive technology for indicating the presence of OP compounds in muscle tissue prior to clinical abnormalities.

Action Potentials↗
PubMed1991

Analysis of the organophosphate-induced electromyographic response to repetitive nerve stimulation: paradoxical response to edrophonium and D-tubocurarine.

We studied the mechanism underlying acute organophosphate intoxication (OPI) through in-vivo and in-vitro electrophysiologic studies in rats injected with diisopropylfluorophosphate. Intoxicated rats showed weakness, repetitive compound muscle action potentials (CMAPs) in response to a single stimulus, and decremental response to repetitive nerve stimulation that was most pronounced at the second CMAP. The decrement was worsened with the administration of edrophonium, and was completely reversed by D-tubocurarine. In-vitro microelectrode studies showed no reduction in the amplitude of miniature endplate potentials (MEPPs) or in the quantal content of end-plate potentials (EPPs). However, the half-decay times of MEPPs and EPPs were significantly prolonged. Trains of stimuli induced sustained end-plate depolarization via a "staircase phenomenon" of summation of prolonged EPPs, which was enhanced by edrophonium and abolished by D-tubocurarine. These results indicate that sustained end-plate depolarization can directly account for the decrement and weakness in acute OPI.

Animals↗
PubMed1980

Altered vascular permeability in the dental pulp of traumatised rat teeth.

A study was made of the vascular permeability changes occurring in the dental pulp of rat teeth subjected to trauma of the occlusal surface with a special steel burr. The vascular response was measured by leakage of 131I-labelled human serum albumin and of colloidal carbon. The effect of a variety of inhibitors of increased vascular permeability was observed. The results obtained support the hypothesis that in the model studied the vascular response of the dental pulp is mediated by the sequential release of histamine and 5-HT, kinins and prostaglandins.

Animals↗
PubMed1989

Looking for human glandular kallikrein-1 in the prostate.

Based on recent studies indicating that human glandular kallikrein-1 (hGK-1) mRNA was present in the prostate, we have undertaken to determine whether the prostate contained trypsin-like proteases with properties compatible with those deduced from hGK-1 gene nucleotide sequence. The first series of experiments showed that only minimal levels of trypsin-like enzymatic activity, determined with synthetic substrates, were present in chromatographic fractions of prostatic glycoproteins having a molecular weight in the range expected for hGK-1, i.e., 25,000-35,000. Because of this, we used [3H]diisopropylfluorophosphate (DFP) labeling alone or in the presence of various serine-protease inhibitors to identify trypsin-like proteases in the prostate. Two-dimensional gel electrophoresis of prostatic glycoproteins showed the presence of minor spots of 18-32 kDa. These spots were slightly more acidic than were those of prostate specific antigen (PSA) and were completely inhibited by preincubation with tosyl lysine chloromethyl ketone and p-nitrophenyl-p-guanidobenzoate in contrast to PSA spots that were not affected by these treatments. When a similar procedure was applied to total cytosolic proteins instead of glycoproteins, an additional 30 kDa DFP binding protein was observed. This relatively abundant protein was much more acidic than was PSA and was not inhibited by any of the protease inhibitors tested. In conclusion, this study has permitted us to demonstrate the presence of two sets of proteins that have physicochemical properties compatible with those that can be deduced from the information contained in the hGK-1 gene.

Amino Acid Sequence↗
PubMed1994

Inhibitors of chymotrypsin-like proteases inhibit eosinophil peroxidase release from activated human eosinophils.

Eosinophils contain many cytotoxic mediators including eosinophil peroxidase (EPO) in their granules; on degranulation, these mediators are released by various pathophysiological stimuli, resulting in severe tissue damage. However, little is known about inhibitors of degranulation. Here, we report that eosinophils isolated from patients with bronchial asthma have significant chymotrypsin-like serine protease activity in the high salt extract fraction. The protease partially purified and labeled with [3H]diisopropylfluorophosphate has an apparent molecular mass of 28 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The chymotrypsin-like protease was not immunoreactive with antibodies against chymase and atypical chymase from rat mast cells or with an antibody against cathepsin G from human neutrophils. Studies on the subcellular distribution of the chymotrypsin-like protease indicated that the enzyme is mainly localized with EPO in eosinophil granules. Chymostatin, an inhibitor of the chymotrypsin-like protease(s), but not an inhibitor of other types of proteases, markedly inhibited the EPO release from eosinophils that was induced by immunoglobulin G plus rIL-5 or platelet-activating factor, although it had no effect on the release of EPO induced by the calcium ionophore A23187. These results suggest that proteolytic activation by chymotrypsin-like serine protease(s) in eosinophils plays some role in the process of receptor-mediated EPO release from the granules.

Affinity Labels↗
PubMed1994

Characterization of a novel carboxypeptidase produced by the entomopathogenic fungus Metarhizium anisopliae.

Preparative isoelectric focusing and gel filtration chromatography were used to purify a carboxypeptidase produced by the entomopathogenic fungus Metarhizium anisopliae during growth on cockroach cuticle. The enzyme was inhibited by diisopropyl fluorophosphate, implying involvement of a serine residue in catalysis. However, the M. anisopliae enzyme differed from most serine carboxypeptidases in also being inhibited by the metal chelator 1,10-phenanthroline and in being a small (30 kDa), basic (pI 9.97) protein with a neutral pH optima (pH 6.8). These properties resemble those exhibited by some metalloproteases but the enzyme is not inhibited by Cd2+; nor do Zn2+ or Co2+ restore activity in enzyme inhibited with phenanthroline. The amino-terminal sequence (22 residues) showed no similarity to other protein sequences. Unlike previously reported fungal carboxypeptidases, the M. anisopliae enzyme is powerfully inhibited by potato carboxypeptidase inhibitor. The carboxypeptidase shows a broad primary specificity toward amino acids with hydrophobic side groups in a series of N-blocked dipeptides, with substrates with phenylalanine being the most rapidly hydrolyzed. The S1 subsite also accommodated Glu, confirming its low selectivity. Proline at P1 or P1 resulted in a very poor substrate. The specificity of the carboxypeptidase complements that of the subtilisin-like protease (Pr1) of M. anisopliae. Both Pr1 and the carboxypeptidase are produced during carbon and nitrogen deprivation, which indicates that the exopeptidase functions with Pr1 to degrade peptides to supply amino acids during starvation and pathogenicity.

Amino Acid Sequence↗
PubMed1999

Tau phosphorylation by diisopropyl phosphorofluoridate (DFP)-treated hen brain supernatant inhibits its binding with microtubules: role of Ca2+/Calmodulin-dependent protein kinase II in tau phosphorylation.

Diisopropyl phosphorofluoridate (DFP) produces organophosphorus ester-induced delayed neurotoxicity (OPIDN) in hen, human, and other sensitive species. This is characterized by mild ataxia, which progresses to severe ataxia or paralysis in a few days. Ultrastructurally, OPIDN is associated with the degeneration of axons in central and peripheral nervous systems. Bacterially expressed longest human tau protein (htau40) phosphorylated by DFP-treated hen brain supernatant showed a decrease in microtubule binding in a shorter time than that phosphorylated by control hen brain supernatant. The decrease in htau40-microtubule binding observed on htau40 phosphorylation by the recombinant Ca2+/calmodulin (CaM)-dependent protein kinase II (CaM kinase II) alpha-subunit showed that CaM kinase II present in brain supernatant could participate in tau phosphorylation even in the absence of Ca2+/CaM and decrease tau-microtubule binding. In addition, use of htau40 mutants, htau40m1 (Ala416) and htau40m6 (Asp416), suggested that replacement of Ser416 by neutral or acidic amino acid produced some change in htau40 conformation that caused diminished binding with microtubules phosphorylated by brain supernatant in the presence of ethylene glycol bis(beta-aminoethyl ether) N, N'tetraacetic acid (EGTA). The change in conformation produced by Ser416 phosphorylation, however, was different from that produced by mutants since only nonmutated htau40 showed a significant decrease in binding with microtubules on phosphorylation by recombinant CaM kinase II in the presence of Ca2+/CaM compared to that obtained by phosphorylation in the presence of EGTA. This study showed that enhanced Ca2+/CaM-dependent protein kinase activity in DFP-treated hen brain supernatant may cause decreased tau-microtubule binding and destabilization of microtubules and may be involved in axonal degeneration in OPIDN.

Amino Acid Substitution↗
PubMed1999

Identification of serine esterases in tissue homogenates.

Serine esterases react with [3H]diisopropylphosphofluoridate ([3H]DFP) to produce radioactive adducts that can be resolved by denaturing slab gel electrophoresis. To identify an esterase or its catalytic subunit, a potential substrate was included in the reaction mixture with the expectation that it would suppress the enzyme's reaction with [3H]DFP. The nature of the enzyme could be inferred from the character of the substrates that suppress labeling. The validity of this analytical method was tested with two serine proteases, trypsin and alpha-chymotrypsin, and two serine esterases, acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), and several of their natural or model substrates or inhibitors. Application of the method to complex biological systems was tested with chicken embryo brain microsomes. Trypsin labeling with [3H]DFP was suppressed by alpha-N-benzoyl-l-arginine ethyl ester (BAEE) and poly-l-lysine but not by benzoyl-l-tyrosine ethyl ester (BTEE). [3H]DFP labeling of chymotrypsin was suppressed by both BAEE and BTEE. Labeling of AChE and BuChE was suppressed by their natural and some related substrates and inhibitors. [3H]DFP reacted with brain microsomes to produce nine distinct radioactive bands. When the relevant substrates and inhibitors of AChE were included in the reaction mixtures, labeling of only the 95-kDa band was suppressed, implicating it as AChE. Labeling of the 85- and 79-kDa bands was inhibited by butyrylcholine, suggesting that these proteins have BuChE activity.

Acetylcholinesterase↗
PubMed1996

Conversion of acetylcholinesterase hydrophilic tetramers into amphiphilic dimers and monomers.

Exposure of purified hydrophilic tetramers of acetylcholinesterase (AChE) from fetal bovine serum to various guanidinium chloride (Gdn) concentrations led to inactive tetramers (2 M Gdn) and dimers (6 M Gdn). The native tetramers were almost fully monomerized by reduction, a minor fraction of the released monomers remaining active. Sedimentation analysis and hydrophobic chromatography showed that the modified tetramers, dimers and monomers had amphiphilic properties. Intrinsic fluorescence spectra and binding of the amphiphilic probe, 1-anilino-8-naphthalene sulfonate (ANS), revealed that AchE subunit in the modified tetramers were in a 'molten globule' structure, the dimers in a denatured stated, and the inactive monomers in a 'native-like' structure. These data show that AChE subunits possess a flexible conformation, which may be important for generating a full set of molecular forms. In addition, the behavior of the active monomers with amphiphiles may explain the interactions of type II AChE forms with membranes.

Acetylcholinesterase↗
PubMed1997

Lung "surfactant convertase" is a member of the carboxylesterase family.

The extracellular conversion of lung surfactant from tubular myelin to the small vesicular form has previously been shown to require a serine-active enzyme called "surfactant convertase." In the present study, a 72kD serine-active enzyme previously identified in mouse lung alveolar lavage and having convertase activity was partially sequenced. Sixty-eight residues obtained from amino acid sequencing of this protein show that it is a new member of the mouse carboxylesterase family (EC 3.1.1.1). The 72kD lung protein also has esterase activity. A commercial esterase of the same family was able to reproduce surfactant convertase bioactivity in vitro, unlike several serine proteinases previously tested. We conclude that surfactant convertase is a carboxylesterase which mediates a biochemical step in the extracellular metabolism of surfactant.

Amino Acid Sequence↗
PubMed1999

Cloning and expression of a novel lysophospholipase which structurally resembles lecithin cholesterol acyltransferase.

Lecithin cholesterol acyltransferase (LCAT) is the key enzyme in the esterification of plasma cholesterol and in the reverse cholesterol transport on high-density lipoprotein (HDL). We have found a novel LCAT-related gene among differentially expressed cDNA fragments between two types of foam cells derived from THP-1 cells, which are different in cholesterol efflux ability, using a subtractive PCR technique. The deduced 412-amino-acid sequence has 49% amino acid sequence similarity with human LCAT. In contrast to the liver-specific expression of LCAT, mRNA expression of the gene was observed mainly in peripheral tissues including kidney, placenta, pancreas, testis, spleen, heart, and skeletal muscle. The protein exists in human plasma and is probably associated with HDL. Moreover, we discovered that the recombinant protein hydrolyzed lysophosphatidylcholine (lysoPC), a proatherogenic lipid, to glycerophosphorylcholine and a free fatty acid. We have therefore named this novel enzyme LCAT-like lysophospholipase (LLPL), through which a new catabolic pathway for lysoPC on lipoproteins could be elucidated.

Amino Acid Sequence↗
PubMed1999

Activity in monomers of human cytomegalovirus protease.

Herpesvirus proteases require dimerization for activity, although crystallographic data indicate that each monomeric subunit possesses a well-separated and complete active site. This suggests that dimerization stabilizes the monomeric protease subunits in an active conformation. Chemical cross-linking with disuccinimidyl glutarate was used to capture human cytomegalovirus protease in its various conformations. The cross-linked protease retained activity under mildly chaotropic conditions (0.25 to 0.75 M urea) in contrast to non-cross-linked protease which lost activity. Identification of active protease species by incorporation of radioactive diisopropylfluorophosphate showed that in addition to cross-linked dimers, cross-linked protease monomers were responsible for a significant fraction of the total protease activity. These results are consistent with the hypothesis that herpesvirus protease activation occurs by stabilization of an active conformer in the dimer.

Binding Sites↗