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  • 1
    ISSN: 1432-0738
    Keywords: Neuropathy ; Organophosphorus ; Trichlorphon ; Neurotoxic Esterase ; Screening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Progressive neuropathy developed in a man during 2–8 weeks after acute poisoning by a pesticide said to contain trichlorphon. The neuropathy was typical of that caused by organophosphorus esters in the delay and in the maintenance of normal conduction velocity in surviving nerve fibres. A sample alleged to be typical of the ingested material was not more active against hen brain neurotoxic esterase (NTE) than was pure trichlorphon. Delayed neuropathy has never been produced in hens by a single dose of trichlorphon. This incident and studies of human brain in vitro suggest that the ratio neurotoxicity/lethality for trichlorphon is higher in man than in the hen. Suggestion is made of laboratory tests to improve neurotoxicity screening.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 41 (1978), S. 107-110 
    ISSN: 1432-0738
    Keywords: Delayed neurotoxicity ; Dimethyl phosphates ; Neurotoxicity testing anomaly
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Several dimethyl phosphate behave anomalously in tests for delayed neurotoxicity. Doses given to hens caused high inhibition of brain neurotoxic esterase (NTE) but no ataxia. Less inhibition of NTE was seen in spinal cord than in brain. Di-isopropyl phosphorofluoridate caused equal inhibition of NTE in brain and cord. When dosing with dimethyl phosphates was repeated NTE inhibition in cord increased and pair-dosed birds became ataxic. In vitro brain and cord NTE were indistinguishable but the in vivo discrepancy between inhibition of brain and cord NTE was matched by a similar discrepancy in inhibition of AChE. It appears that ataxia arises from inhibition of spinal cord NTE and that only in the present cases (among about 200) was the effect in brain not a perfect biochemical monitor.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 32 (1979), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Neurotoxic esterase (NTE) is now regarded as the site of the primary biochemical lesion in the delayed neuronal degeneration produced by certain organophosphorus esters. Since hens are the species of choice in studies of this neuropathy the subcellular distribution of NTE and marker enzymes in adult hen brain was carried out. Up to 70%, of NTE was recovered in a microsomal fraction (P3) which was also enriched in 5′-nucleotidase (5′-ribonucleotide phosphohydrolase EC 3.1.3.5), a plasma membrane marker. The protein content of this fraction (31% of the parent homogenate) is double that of equivalent mammalian brain fractions. The LDH distribution suggests that the P3 fraction contained many small synaptosomes. Subfractionation of microsomes by rate and equilibrium centrifugation on sucrose density gradients segregated the RNA but failed to separate the NTE. 5′-nucleotidase and glucose-6-phosphatase (D-glucose-6-phosphate phosphohydrolase EC 3.1.3.9) from each other. NTE was considerably concentrated (2–5 times) in subfractions of the P2 fraction, which are believed to be enriched in synaptosomal membranes. A similar localization of NTE and AChE was found in subfractions of P2 from neonatal chick brain. Axon fragments contained a significant amount of NTE which was not associated with the myelin. Nuclear and mitochondrial fractions were low in NTE. Microsomes could be partitioned in biphasic aqueous polymer systems, but with little enrichment of NTE. The possible association of NTE with synaptosomal membranes suggests that early events in organophosphorus neuropathy may occur at the axonal (? synaptic) surface.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 37 (1977), S. 113-115 
    ISSN: 1432-0738
    Keywords: Determination ; Neurotoxic esterase ; Neurotoxicity ; Organophosphate compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Durch Bestimmung der neurotoxischen Esterase (NTE) ist es möglich, im Gehirn von mit phosphororganischen Pflanzenschutzmitteln, Weichmachern und anderen Stoffen behandelten Hühnern die potentielle Neurotoxizität dieser Stoffe zu erfassen. Die ursprüngliche Methode [Johnson, M. K. Biochem. J. 114, 711–717 (1969)] wurde vereinfacht, so daß Zentrifugieren und Transferschritte nicht mehr erforderlich sind. Die Selektivität und Empfindlichkeit der Methode wurde verbessert. Die Herstellung stabiler Reagentienstammlösungen wird beschrieben.
    Notes: Abstract The assay of neurotoxic esterase (NTE) in brains taken from dosed hens enables potential neurotoxicity of organophosphate pesticides, plasticers, etc. to be assessed. The original assay [Johnson, M. K. Biochem. J. 114, 711–717 (1969)] has been simplified to eliminate centrifugation and transfer steps and both the selectivity and the sensitivity have been increased. The procedures necessary to obtain stable reagent stocks are described.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 34 (1975), S. 259-288 
    ISSN: 1432-0738
    Keywords: Organophosphates ; Neurotoxicity ; Mechanism ; Structure/Activity ; Organophosphate ; Neurotoxizität ; Wirkungsmechanismus ; Struktur-Aktivitätsbeziehungen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Wirkungsmechanismus Die Beweisführung nimmt an, daß die Phosphorylierung des aktiven Zentrums eines spezifischen Enzyms, “neurotoxische Esterase” genannt, das initiale biochemische Ereignis der zur verzögerten Neurotoxizität führenden Reaktionsfolge ist. Darauf folgt die Spaltung einer Bindung (hydrolytisch?) die einen monosubstituierten Phosphorsäurerest am Protein hinterläßt. — Der Mechanismus, auf dem die Schutzwirkung einiger Phosphonsäureester gegenüber neurotoxischen Substanzen beruht, wird erläutert. Screening-Methode Die Bestimmung der Wirkung auf die Aktivität der “neurotoxischen Esterase” im Hühnergehirn (in vitro und in vivo) stellt eine schnelle biochemische Probe zur Ergänzung des 3wöchigen klinischen Tests dar. Der Test erlaubt die Abschätzung von Sicherheitsgrenzen für Substanzen, die negative Ergebnisse im klinischen Test erbringen und häufig als Pestizide, Weichmacher usw. verwendet werden. Vereinfachte Bestimmungsmethoden wurden entwickelt. Struktur-Wirkungs-Eeziehungen Für viele Verbindungen liegen Daten über die biochemische und neurotoxische Wirkung vor. Diese dienen als Basis für Vorhersagen von Struktur-Wirkungs-Beziehungen. Die seit 1930 veröffentlichten Daten zur Neurotoxizität werden unter diesem Gesichtspunkt behandelt.
    Notes: Abstract Mechanism of Action Evidence is reviewed that the initial biochemical event leading to delayed neurotoxicity is phosphorylation of the active site of a specific enzyme called Neurotoxic Esterase. This is followed by a bondcleavage (? hydrolytic) leading to formation of a mono-substituted phosphoric acid residue on the protein. The mechanism by which some phosphinates protect hens against neurotoxic compounds is explained. Screening Assay Assay of effects of compounds on Neurotoxic Esterase activity of hen brain in vitro and in vivo provides a quick biochemical screen to supplement the 3-week clinical test. This test provides an estimate of safety margin for compounds which give negative results in the clinical test and are currently used as pesticides, plasticisers, etc. Simplified assay procedures are being developed. Structure/Activity Studies Data is now available for the biochemical and neurotoxic activity of many compounds. This provides a basis for structure/activity predictions; neurotoxicity data published since 1930 has been assessed in this light.
    Type of Medium: Electronic Resource
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