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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 53 (1983), S. 275-288 
    ISSN: 1432-0738
    Keywords: 4-Dimethylaminophenol ; Ferrihemoglobin ; Metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The cyanide antidote 4-dimethylaminophenol · HCl (DMAP) was administered orally, i.v., or i.m. to man and dog. Ferrihemoglobin formation and changes of several parameters in human blood were investigated to obtain information on damage to liver, kidney, muscle, and red blood cells; in addition, the metabolism of DMAP was studied. In dogs, the initial rate of ferrihemoglobin production (DMAP, 3.25 mg/kg i.v. or i.m., 15 mg/kg orally) amounted to 28%, 3.5%, and 2% of the total hemoglobin per min; the corresponding values for man were 9%, 2%, and 2% per min. The dogs behaved normally while CPK increased after i.m. injection. In man, only i.m. injection of DMAP (3.25 mg/kg) was followed by increases in LDH, GOT, and CPK of 110, 260, and 490%, resp.; while total bilirubin, conjugated bilirubin, and iron concentration rose by 270,120, and 50%, respectively. Bilirubin and iron concentration increased also after DMAP i.v. (3.25 mg/kg) or when it was taken orally (600 or 900 mg). The lactate concentration was not influenced while the pyruvate concentration increased by 50%. DMAP produced hemolysis in vitro. Generally, the values determined in vivo approached the starting level within 1 week. Intramuscular injection of DMAP induced reversible subjective and objective symptoms, e.g., local pain, swollen buttock, fever reaction. The urine showed no pathological changes. About 54% of DMAP taken orally was excreted as metabolites in the urine, 41% as glucuronide, 7% as sulfate, and 6% as thioethers. After i.v. administration the total of metabolites was somewhat higher, and the thioether proportion was 15%. The results indicate that DMAP is readily absorbed after oral administration but undergoes significant first pass effect in the liver. Therefore, the 4-fold i.v. dose must be administered orally to achieve the same ferrihemoglobin formation.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 64 (1990), S. 586-589 
    ISSN: 1432-0738
    Keywords: Organophosphate metabolism ; Soman metabolism ; Liver perfusion ; Esterases
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The detoxification of soman (1,2,2-dimethylpropyl methylphosphonofluoridate) was measured in rat livers, using hemoglobin-free, non-recirculating perfusion in situ. Since the detoxification processes may differ in perivenous and periportal zones of liver parenchyma, soman uptake, stereoselective metabolism and inhibition of esterases were compared in antegrade and retrograde perfusion experiments. At low concentrations of soman (up to about 10 μmol l−1 for 5 min) soman was taken up by the liver nearly quantitatively. About 5% recovery rate in the perfusate corresponded well to the intrahepatic shunt flow. Infusions of higher amounts yielded increasing recovery rates. The racemic infusion medium contained the four isomers of soman, C(−)P(−) to C(+)P(+), in nearly identical amounts, whereas in the effluent perfusate only P(−) isomers were found. Even small amounts of soman (5–120 nmol g−1 liver wet weight) caused significant inhibition of hepatic aliesterase activity. Doses higher than 200 nmol g−1 suppressed esterase activity by more than 90%. No essential differences in soman uptake, stereoselective metabolism or inhibition of esterases were found between antegrade and retrograde perfusion experiments.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 70 (1995), S. 16-19 
    ISSN: 1432-0738
    Keywords: Key words Methantheline ; Acetylcholinesterase ; Soman ; Reactivation ; HI 6
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The effect of methantheline, a quaternary ammonium compound, on the reactivation by HI 6 of soman-inhibited human erythrocyte acetylcholinesterase (AChE) was investigated in vitro using purified human erythrocyte AChE or washed human erythrocytes. Methantheline itself was found to be a mixed competitive/non-competitive inhibitor of AChE (Kii 360±70 μmol/l; Ki 240±10 μmol/l). In all experiments the enzyme was first inhibited by soman for 30 min under conditions preventing ageing (pH 10, 0°C) and then ageing was allowed by changing the pH to 7.3 and the temperature to 37°C. Methantheline addition (0.36 or 3.6 mmol/l) at the start of ageing increased the portion of AChE which could be reactivated by HI 6 (0.32 mmol/l) added 5 min later, from 24.6±1.0% (mean±SEM) of the original acitivity to 42.1±1.8% or 45±2.9%, respectively. With HI 6 alone, the portion of AChE activity which could be reactivated 25 min after the start of ageing decreased rapidly with the delay of the oxime addition (100% of the original activity at immediate addition), the half-life being approximately 2.5 min. With methantheline alone (0.36 mmol/l) the AChE activity was lower after immediate addition (37% of the original value), but the loss of activity due to the increasing delay of methantheline addition exhibited a similar half-life as with HI 6. Finally, when methantheline (0.36 mmol/l) was added at the start of ageing and HI 6 at various intervals thereafter the half-life of AChE activity loss due to the delay of HI 6 addition at least doubled, compared to incubations without methantheline.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Archives of toxicology 61 (1988), S. 444-449 
    ISSN: 1432-0738
    Keywords: As2O3 ; Arsenicals ; Gluconeogenesis ; Carbohydrate metabolism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract 1) The effect of As2O3 and As2O5 on gluconeogenesis from various substrates in the liver and kidney of rats was investigated. 2) A concentration-dependent inhibition by As2O3 was found. The effect was not dependent on the amount of investigated material (hepatocytes or kidney tubules). For either hepatocytes or kidney tubules the extent of inhibition depended strongly on the substrate used. The highest degree of inhibition was observed in incubations with pyruvate. The inhibition of glucose formation was accompanied to a lesser extent by a diminution in O2 consumption and ATP content. The effect was also dependent on the substrate used. Maximum effect was found in incubations with pyruvate. 3) Oleate, 0.5 mmol/l, increased gluconeogenesis from pyruvate. The effect was not abolished by As2O3. 4) A decrease in the content of acetyl-CoA, 3-hydroxybutyrate, and reduced glutathione was found in suspensions of isolated rat kidney tubules or hepatocytes incubated with As2O3. 5) About 10 times higher concentrations of As2O5 were necessary to induce a similar extent of inhibition of gluconeogenesis, decrease in O2 consumption, and in ATP content as compared with As2O3. The extent of the As2O5 effect depended on the concentration of the toxicant and on the substrate used. Gluconeogenesis from pyruvate exhibited the highest sensitivity to As2O5. 6) All findings can be largely explained by inhibition of pyruvate dehydrogenase as the central target for arsenicals. The subsequent depletion of acetyl CoA results in impaired formation of reducing equivalents in the citric acid cycle, decrease in high energy phosphates and, acetyl CoA being a strong positive modulator of pyruvate carboxylase, in gluconeogenesis inhibition. Carbohydrate depletion, resulting mainly from gluconeogenesis inhibition, is proposed to be a major problem in poisoning with trivalent arsenicals. In accordance with this proposal, starved rats were shown to be much more sensitive to As2O3 than animals with free access to food.
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  • 5
    ISSN: 1432-0738
    Keywords: Cholinesterase ; Soman ; Oxime ; HI 6 ; Dopamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of atropine and the oxime HI 6 on running performance, brain and plasma cholinesterase activity and brain catecholamines were investigated in mice intoxicated with sublethal doses of soman (100 μg/kg s.c.). The running time on a rotating mash wire drum (total running time 60 min) after injection of soman was reduced to 17.2 min. Treatment with atropine (10 mg/kg i.p.) or HI 6 (55 mg/kg i.p.) improved the running peformance to 48.2 and 44.8 min, respectively. Cholinesterase activity was decreased in soman poisoned mice to 47.3% in plasma and 43.5% in brain. Therapy with the oxime HI 6 resulted in a reactivation of soman-inhibited peripheral cholinesterase to 76.6%, but failed to reactivate central cholinesterase. Dopamine levels in mice brain were elevated in soman poisoning by 23.2%, whereas noradrenaline levels remained unchanged. The increase in brain dopamine levels was antagonized by atropine as well as by HI 6. The results of this study lead to the speculation that central dopaminergic mechanisms may be involved in soman toxicity as well as in the antidotal action of atropine and the mainly peripherally acting oxime HI 6.
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  • 6
    ISSN: 1432-0738
    Keywords: Glucose ; Arsenic ; Survival ; Liver ; Mouse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Carbohydrate depletion (glucose and glycogen) was reported to be a major problem in acute arsenic poisoning (Berry and Smythe 1959; Reichl et al. 1988; Szinicz and Forth 1988). In the present paper the effectiveness of glucose substitution was investigated in mice after acute experimental poisoning with As2O3. Four groups of ten mice each received As2O3, 12.9 mg/kg, s.c. After the injection the first group remained without further treatment, the second received saline every 2 h, the third 5% glucose, and the fourth 5% glucose + 0.12 IE insulin/kg i.p. Groups 5 and 6, five mice each, received either saline or glucose only. Group 7, five mice, remained without any treatment. Immediately after death the livers were removed for the enzymatic determination of glucose and glycogen. Mice receiving As2O3 only died within 22 h. The mean survival time was 12.4 h. In mice receiving As2O3 and after that saline, glucose, or glucose + insulin, an increase in the survival time to 30.8, 40.7, and 43.6 h, respectively, was observed. All mice which died showed a significant decrease in the liver glucose and glycogen content, compared to control animals. In livers of survivors, the glucose and glycogen content was not different to the control groups. The data suppport the assumption that carbohydrate depletion is an important factor in arsenic toxicity, and its substitution should be considered in the treatment of arsenic poisoning.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-0738
    Keywords: Key words Organophosphates ; Oxime ; Reactivation ; AChE ; Obidoxime ; Pralidoxime ; HI 6 ; HLö 7
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The new bispyridinium oximes HI 6 and HLö 7 are promising antidotes against poisoning by highly toxic organophosphorus compounds, i.e. nerve agents. Until now, their ability to reactivate pesticide inhibited human acetylcholinesterase (AChE) has not been elucidated. For this purpose human erythrocyte AChE (EC 3.1.1.7) was inhibited (30 min) by chlorfenvinphos, dichlorvos, dicrotophos, heptenophos, mevinphos, monocrotophos, paraoxon, phosphamidon, trichlorfon, malaoxon, omethoate, oxydemeton-methyl or methamidophos by 85–98% of control. After removal of excess inhibitor, obidoxime, pralidoxime (2-PAM), HI 6 or HLö 7 (10, 30 or 100 μmol/l) were added and the AChE activity was measured spectrophotometrically at various times thereafter (5–60 min). The oximes significantly, but not completely, reactivated organophosphate inhibited AChE. The velocity and extent of reactivation were dependent on the oxime and its concentration. In all cases obidoxime was superior to the three other oximes, followed by HLö 7, 2-PAM and HI 6. In most cases obidoxime and HLö 7 were most effective at 10 or 30 μmol/l while 2-PAM and HI 6 needed 100 μmol/l. These data suggest that 2-PAM, HI 6 and HLö 7 are less patent than obidoxime in reactivating human AChE inhibited by organophosphate pesticides.
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  • 8
    ISSN: 1432-0738
    Keywords: Key words Acetylcholinesterase ; Organophosphates ; Oxime ; Reactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The treatment of poisoning by highly toxic organophosphorus compounds (nerve agents) is unsatisfactory. Until now, the efficacy of new potential antidotes has primarily been evaluated in animals. However, the extrapolation of these results to humans is hampered by species differences. Since oximes are believed to act primarily through reactivation of inhibited acetylcholinesterase (AChE) and erythrocyte AChE is regarded to be a good marker for the synaptic enzyme, the reactivating potency can be investigated with human erythro‐cyte AChE in vitro. The present study was undertaken to evaluate the ability of various oximes at concentrations therapeutically relevant in humans to reactivate human erythrocyte AChE inhibited by different nerve agents. Isolated human erythrocyte AChE was inhibited with soman, sarin, cyclosarin, tabun or VX for 30 min and reactivated in the absence of inhibitory activity over 5–60 min by obidoxime, pralidoxime, HI 6 or HLö 7 (10 and 30 μM). The AChE activity was determined photometrically. The reactivation of human AChE by oximes was dependent on the organophosphate used. After soman, sarin, cyclosarin, or VX the reactivating potency decreased in the order HLö 7 〉 HI 6 〉 obidoxime 〉 pralidoxime. Obidoxime and pralidoxime were weak reactivators of cyclosarin-inhibited AChE. Only obidoxime and HLö 7 reactivated tabun-inhibited AChE partially (20%), while pralidoxime and HI 6 were almost ineffective (5%). Therefore, HLö 7 may serve as a broad-spectrum reactivator in nerve agent poisoning at doses therapeutically relevant in humans.
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  • 9
    ISSN: 1432-0738
    Keywords: Key words Organophosphate ; Acetylcholinesterase ; Oximes ; Human ; Reactivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The reactivation of organophosphate-inhibited acetylcholinesterase (AChE) by oximes inevitably results in the formation of highly reactive phosphoryloximes (POX), which are able to re-inhibit the enzyme. In this study, the dependence of POX formation on AChE concentration was investigated with sarin-inhibited human erythrocyte AChE (EryAChE). A marked dependence was found with obidoxime but not with the experimental oxime HI 6, suggesting great differences in the decomposition rates of the respective POXs. At a physiological erythrocyte content the reactivation of EryAChE was markedly affected by POX with obidoxime and pralidoxime (2-PAM) but not with the newer oximes HI 6 and HLö 7. Addition of extensively dialysed, sarin-treated human plasma reduced the reactivation by obidoxime and 2-PAM even more. Obidoxime and 2-PAM were superior to HI 6 and HLö 7 in reactivating butyrylcholinesterase (BChE). This effect was pronounced in diluted plasma, but was obscured in concentrated plasma, probably because of re-inhibition by the generated POX. Addition of native erythrocytes to sarin-treated plasma resulted in marked inhibition of EryAChE in the presence of obidoxime, suggesting a higher affinity of the POX for EryAChE. The results indicate that obidoxime and 2-PAM may reactivate sarin-inhibited AChE insufficiently due to re-inhibition by the POX formed. In addition, the re-inhibition of EryAChE may be aggravated by the POX that is produced during BChE reactivation. These reactions must be regarded as therapeutically detrimental and disqualify those oximes which are capable of forming stable POX by reactivation of BChE.
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  • 10
    ISSN: 1432-0738
    Keywords: 4-Dimethylaminophenol ; Co2EDTA ; Ferrihemoglobin ; Oxygen ; Circulation ; Cyanide poisoning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of intravenously injected 4-dimethylaminophenol and Co2EDTA on peripheral circulation, respiration, acid-base balance, and several other physiological and biochemical parameters were studied on dogs. DMAP increased the respiratory minute volume and mean arterial pressure, diminished the lactate-to-pyruvate ratio, and induced an increase in arterial oxygen pressure caused by liberation of oxygen from oxyhemoglobin during the formation of ferrihemoglobin. A study in vitro of the fate of the oxygen during the reaction between DMAP and oxyhemoglobin showed that only 30–40% of the oxygen released by the formation of ferrihemoglobin appeared in the gas phase. Co2EDTA caused circulatory depression, hyperventilation, and metabolic acidosis resulting in a decrease in base-excess and pH. The concentrations of lactate, pyruvate, potassium, and urea nitrogen and the hemoglobin content were increased by Co2EDTA. The side effects of Co2EDTA in therapeutic doses were more serious than those of DMAP. Thus the latter is superior in the therapy of cyanide poisoning, all the more since it detoxifies more cyanide.
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