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Standard therapy of Organophosphorus Compound (OPC) poisoning with oxime-type acetylcholinesterase (AChE) reactivators is unsatisfactory. New bispyridinium oximes have therefore been synthesized. This review summarizes in vitro characteristics of established (pralidoxime, obidoxime, trimedoxime, HI-6) and experimental (K-)oximes, and compares their protective efficacy in vivo, when administered shortly after exposure to Diisopropylfluorophosphate (DFP) and three OPC pesticides (ethyl-paraoxon, methylparaoxon, azinphos-methyl) in the same experimental setting. In addition to reactivating cholinesterase, oximes also inhibit this enzyme; strongest AChE inhibition (IC50 rat blood: 1-9 μM) is observed in vitro for the oximes with a xylene linker (K-107, K-108, K-113). AChE inhibition is weakest for K-27, K-48 and HI-6 (IC50 >500 μM). Intrinsic AChE inhibition of oximes in vitro (IC50, rat) is strongly correlated with their LD50 (rat): oximes with a high IC50 (K-27, K-48, pralidoxime, obidoxime) also show a high LD50, making them relatively non-toxic, whereas oximes K-107, K-108 and K-113 (low IC50 and LD50) are far more toxic. When given in vivo after OP exposure, best protection is conferred by K-27, reducing the relative risk of death to 16-58% of controls, which is significantly superior to pralidoxime in DFP-, ethyl-paraoxon- and methylparaoxon- exposure, and to obidoxime in ethyl-paraoxon- and methyl-paraoxon-exposure. Marked reduction in mortality is also achieved by K-48, K-53, K-74 and K-75, whereas K-107, K-108 and K-113 have no or only a very weak mortality-reducing effect. K-27 is the most promising K-oxime due to its strong reactivation potency, weak cholinesterase inhibition and high LD50, allowing administration in large, very efficacious dosages.

Introduction: Intoxications with organophosphorous compounds, especially paraoxon, are frequent. Organophosphorous compounds inhibit serine hydrolases such as acetylcholine, butyrylcholine, and carboxyl esterases although acetylcholine and butyrylcholine are too sensitive to paraoxon to be useful markers of severity. They cannot show a dose-dependent inhibition during an acute organophosphorous compounds exposure because maximal enzyme inhibition is reached at very low organophosphorous compounds concentrations. Purpose: To determine in vitro the dose-effect relationship between the activity of the paraoxon-sensitive phenylvalerate hydrolase, a member of the carboxyl esterases family, and the paraoxon dose, and to assess its utility as a putatively less sensitive enzyme marker to monitor the severity of an acute paraoxon intoxication. Materials and Methods: Phenylvalerate hydrolase and butyrylcholine activities were determined in serum of nine healthy human volunteers before and after addition of different concentrations of paraoxon. The determination of phenyl-valerate hydrolase activity was carried out using a modification of the method described by Johnson. A commercially available kit was used to measure butyrylcholine activity. Results: Paraoxon inhibits phenyl-valerate hydrolase activity at concentrations above [10.sup.-9] M. Maximal inhibition ([approximately equals] 50% of baseline) is achieved at concentrations above 2.5 x [10.sup.-7] M. The [IC.sub.50] value of paraoxon for phenyl-valerate hydrolase is 34 [+ or -] 2 nM. The uninhibited phenyl-valerate hydrolase activity is due to paraoxon-resistent isoforms. Paraoxon begins inhibiting butyrylcholine activity at concentrations above [10.sup.-9] m. At concentrations above 5 x [10.sup.-5] M, no butyrylcholine activity is measurable. The [IC.sub.50] value of paraoxon for butyrylcholine is 150 [+ or -] 23 nM. Conclusion: The paraoxon-sensitive subunit of phenyl-valerate hydrolase shows dose-dependent inhibition when exposed to paraoxon in vitro, but it is even more sensitive than butyrylcholine to paraoxon inhibition. Determinations of phenyl-valerate hydrolase activity to assess the severity of an acute organophosphorous compounds poisoning cannot be recommended, but phenyl-valerate hydrolase may have utility in worker surveillance., INTRODUCTION Orgaophosphorus compounds (OPCs) are widely used as pesticides in both agricultural and domestic settings, as softening agents and additives to lubricants in industry and technology, and as chemical weapons [...]

Background: Reversible cholinesterase inhibitors, when given prophylactically before exposure to organophosphates, are able to decrease organophosphate-induced mortality. However, the efficacy of pyridostigmine, the only pre-treatment substance approved by the US Federal Drug Administration, is unsatisfactory. Methods: In search of a better prophylactic compound, we determined in vivo the protection conferred by five cholinesterase inhibitors (ranitidine, physostigmine, tacrine, K-27 and pyridostigmine), which were administered in equitoxic dosage (1/4 of LD01) 30 minutes before exposure to the organophosphate dicrotophos. Efficacy was measured in rats by Cox analysis calculating the relative risk of death (RR), RR being 1 for the reference group which received dicrotophos and no prophylaxis. Results: K-27 (RR=0.06), physostigmine (RR=0.15), pyridostigmine (RR=0.22) and tacrine (RR=0.28) significantly (p ≤ 0.05) reduced dicrotophos-induced mortality in comparison to the reference group (dicrotophos without pre-treatment), whereas ranitidine (RR=0.86) had no significant influence. The experimental oxime K-27, when given before dicrotophos exposure, conferred the best in vivo protection. This was significantly (p ≤ 0.05) more efficacious than pre-treatment with any other tested compound. The differences in efficacy between the second best compound, physostigmine, and the less efficacious substances (tacrine and pyridostigmine) were also statistically significant. Conclusion: These data indicate that K-27 can be considered a very efficacious prophylactic agent for organophosphate exposure.

Authorities of Drug Administration in the United States of America approved about 5000 drugs for use in the therapy or management of several diseases. About two hundred of these drugs have active metabolites and the knowledge of their medicinal chemistry is important both in medical practice and pharmaceutical research. This review gives a detailed description of the medicinal chemistry of drugs with active metabolites generated after conjugation. This review focused on glucuronide-, acetyl-, sulphate- and phosphate-conjugation of drugs, converting the drug into an active metabolite. This conversion essentially changed the lipophilicity of the drug.

Deterioration of the cortical cholinergic system is a leading neurochemical feature of Alzheimer’s Disease (AD). This review summarizes evidence that the homomeric 7- nicotinic acetylcholine receptor (nAChR) plays a crucial role in the pathogenesis of this disease, which is characterized by amyloid- (A) accumulations and neurofibrillary tangles originating from of hyperphosphorylated tau protein. A binds to 7-nAChRs with a high affinity, either activating or inhibiting this receptor in a concentration-dependent manner. There is strong evidence that 7-nAChRs are neuroprotective, reducing A-induced toxicity; but co-localization of 7- nAChRs, A and amyloid plaques also points to neurodegenerative actions. A induces tau phosphorylation via 7-nAChR activation. A influences hippocampus-dependent memory and long-term potentiation in a dose-dependent way: there is evidence that enhancement by picomolar A concentrations is mediated by 7-nAChRs, whereas inhibition by nanomolar concentrations is independent of nAChRs and probably mediated by small A42 oligomers. 7-nAChRs located on vascular smooth muscle cells and astrocytes are also involved in the pathogenesis of AD. Although these data strongly point to an important role of 7-nAChRs in the development of AD, dose-dependence of the effects, rapid desensitization of the receptor and dependence of the effects on A aggregation (monomers, oligomers, fibrils) make it difficult to develop simple therapeutic strategies acting upon this receptor.

Oximes are acetylcholinesterase reactivators of use in poisoning with organophosphorus inhibitors of cholinesterase (OPIChE: (organophosphates and organophosphonates). They are clinically used as an adjunct to atropine in such exposure. Clinical experience with oximes is, however, disappointing. This paper reviews available data concerning the ability of established and new oximes to reactivate cholinesterases inhibited by two differently substituted prototypical organophosphates: ethyl- and methyl-paraoxon. The intrinsic toxicity of oximes is quantified in vitro by measuring the concentration required to inhibit red blood cell (RBC) cholinesterase activity by 50 (IC50). Reactivation ability is assessed in vitro via the IC50 shift graph. The slope of the shift graph (tan ) is used to quantify the magnitude of the protective effect (nM IC50 increase per μM reactivator). The ranking of reactivating potencies of the examined oximes determined with methyl-paraoxon as an inhibitor is essentially the same as the ranking obtained using ethyl-paraoxon as an inhibitor. In the in vitro model used, the presence of ethyl versus methyl substituents does not seem to significantly alter the ability of the examined oximes to reactivate the esterase. In vitro derived results were subsequently validated in vivo in rats using ethyl-paraoxon and methyl-paraoxon as cholinesterase inhibitors and various oximes as reactivators. Mortality data were compared and hazard ratios calculated using Cox proportional hazards model. Overall, the ability of in vitro testing (tan α determinations) to predict in vivo protection by oximes is limited.

The effect of the plant-derived nonpsychotropic cannabinoid, cannabidiol (CBD), on the function of hydroxytryptamine (5-HT)3A receptors expressed in Xenopus laevis oocytes was investigated using two-electrode voltage-clamp techniques. CBD reversibly inhibited 5-HT (1 microM)-evoked currents in a concentration-dependent manner (IC50 = 0.6 microM). CBD (1 microM) did not alter specific binding of the 5-HT3A antagonist [3H]3-(5-methyl-1H-imidazol-4-yl)-1-(1-methylindol-3-yl)propan-1-one (GR65630), in oocytes expressing 5-HT3A receptors. In the presence of 1 microM CBD, the maximal 5-HT-induced currents were also inhibited. The EC50 values were 1.2 and 1.4 microM, in the absence and presence of CBD, indicating that CBD acts as a noncompetitive antagonist of 5-HT3 receptors. Neither intracellular BAPTA injection nor pertussis toxin pretreatment (5 microg/ml) altered the CBD-evoked inhibition of 5-HT-induced currents. CBD inhibition was inversely correlated with 5-HT3A expression levels and mean 5-HT3 receptor current density. Pretreatment with actinomycin D, which inhibits protein transcription, decreased the mean 5-HT3 receptor current density and increased the magnitude of CBD inhibition. These data demonstrate that CBD is an allosteric inhibitor of 5-HT3 receptors expressed in X. laevis oocytes. They further suggest that allosteric inhibition of 5-HT3 receptors by CBD may contribute to its physiological roles in the modulation of nociception and emesis.

Three major flavonoid chamomile components (quercetin, apigenin-7-O-glucoside and rutin) were subjected to oxidative metabolism by cytochrome P-450 of rat liver microsomal preparations. Changes over time in their respective concentrations were followed using reversed-phase HPLC with UV detection. No clean-up had to be applied as only the specific flavonoid had to be separated from the background components originating from the rat liver microsome.Neither the concentration of apigenin-7-O-glucoside nor that of the diglycoside rutin decreased during one hour of exposure to rat microsomal treatment. In contrast, the concentration of quercetin, a lipophilic aglycon, decreased.Our analytical HPLC results complement the calculated lipophilicity (logP) of these compounds; the relatively high lipophilicity of quercetin appears to predispose it to oxidative metabolism in order to decrease its fat solubility. In contrast the much less lipophilic compounds apigenin-7-O-glucoside and rutin were resistant to microsomal treatment.in silicoin vitro

After administration of various amounts of pralidoxime to rats, the levels in serum, brain and cerebrospinal fluid (CSF) were measured using capillary zone electrophoresis (CZE). The calibration curves were established using spiked samples. The calibration covers the ranges from 0.3 - 200 g/mL, 0.3 - 7 g/mL and 0.1 - 7 g/mL for serum, brain and CSF, respectively. The CZE measurement opens the way to the fast and reliable determination of pyridinium aldoxime concentrations in serum, cerebrospinal fluid and brain, thereby monitoring blood-brain and blood-CSF penetration of pyridinium aldoximetype antidotes clinically used in organophosphate poisoning.

Oximes are acetylcholinesterase reactivators of use in poisoning with organophosphorus inhibitors of cholinesterase (OPIChE: (organophosphates and organophosphonates). Pralidoxime (1) and obidoxime (2) are clinically used as an adjunct to atropine in such exposure. Clinical experience with oximes is however disappointing. The paper reviews the available data concerning the ability of established and new oximes to reactivate cholinesterases inhibited by two differently substituted prototypical organophosphates: ethyl-paraoxon (3) and methyl-paraoxon (4). Reactivation ability is quantified in vitro via the IC50 shift curve. The slope of the shift curve (tg α) is used to quantify the magnitude of the protective effect (nM IC50 increase per microM reactivator). The ranking of reactivator potencies of the examined oximes determined with 4 as an inhibitor is essentially the same as the ranking obtained using 3 as an inhibitor. In the in vitro model used, the presence of ethyl vs. methyl substituents does not seem to significantly alter the in vitro ability of the examined oximes to reactivate the esterase. In vitro derived results were subsequently validated in vivo in rats using 3 and 4 as cholinesterase inhibitors and various oximes as reactivator. Mortality data were compared and hazards ratios calculated using Cox proportional hazards model. Overall the ability of the in vitro testing (tg α determinations) to predict in vivo performance of the oximes is limited.

Quaternary pyridinium aldoximes have been analyzed by thin-layer chromatography. Their separation was adequate when silica plates were used with a mobile phase with a high water content. As a consequence of their limited migration, reversed-phase TLC was not appropriate for determination of the lipophilicity of quaternary pyridinium aldoximes. Displacement TLC of some quaternary pyridinium aldoximes is, nevertheless, possible using silica as stationary phase with water–acetone–hydrochloric acid mobile phases. Normal-phase TLC with different concentrations of organic modifier gave a series of RMvalues for the pyridinium aldoximes. Approximation of the different plots of RMagainst organic modifier concentration to straight lines afforded RM,0values and the slopes of the lines. The RM,0values and the slopes both serve as indicators of the hydrophilic character of the compounds.

A hallmark of the so-called amniotic fluid embolism is the induction of coagulation defects. Entry of meconium-free autologous amniotic fluid into the circulation, however, is innocuous. Little is known about the true causative agent or agents. The purpose of this study was to assess the effects of homogenized autologous fetal membranes (FM) on the coagulation system in the mini-pig model.

The in vivo effects of the organophosphorus compound (OPC) paraoxon (POX) on blood coagulation of mini pigs were assessed by measuring the partial thromboplastin time (PTT), prothrombin time (PT), fibrinogen, factor V, factor VII, factor VIII, antithrombin III, protein C, and platelet count. The mini pigs were randomly assigned to a POX-treatment group (n=9) receiving 54 mg POX kg−1BW−1or the control group (n=9). Measurements were carried out over a period of 150 min after poisoning. The exposure to POX did not have any influence on measurements of PT, factor VIII, factor VII, factor V, antithrombin III, protein C, or fibrinogen compared to the control group evaluated by rank order test (ROT) during the time of observation (150 min). Changes seen in the intrinsic coagulation followed a biphasic pattern corresponding to an early sympathomimetic phase with PTT-shortening and a decrease of the platelet count, and a late vagal phase, with PTT-prolongation. The hypercoagulability seen in the sympathomimetic phase is probably due to a massive release of catecholamines from the adrenals. Previous studies showed in vitro no coagulation activating effect of POX. The hypocoagulability in the vagal phase shown by the PTT-prolongation is probably due to POX influencing platelet function or its inhibition of clotting factors, which are serine proteases, or a combination of the two.

The purpose of the present study was to establish in the mini pig model the effects of paraoxon (POX) on PLA2activity. Six anesthetized and mechanically ventilated mini pigs were infused over 50 min with 0.3, 1, 3, 9, 27 and 81 mg POX kg−1BW−1dissolved in ethanol, respectively. The control animal received no POX but the ethanol amount corresponding to the highest POX dose. PLA2activity measurements were carried out immediately after POX application. Data were analysed with the Mann–Whitney–Wilcoxon rank order test. Statistical significance was assumed for P≤0.05. Exposure to POX inhibited PLA2activity to 50.5±8.9% of baseline activity. The changes seen were not dose-dependent. The dose dependency previously demonstrated in vitro was not reproducible in vivo. This is most probably due to the massive endogenous catecholamine release leading to PLA2activation. An additional masking effect is due to the (co)administration of drugs needed for anesthesia and cardiovascular support, especially Mg2+. These substances also influence the PLA2activity.

Organophosphorus compounds in the form of insecticides are in widespread use and have recently attracted considerable interest as environmentally toxic agents. As little is known about the effect of environmental toxins on the tubal function in the ear, we studied the middle ear pressure necessary to force the Eustachian tube to open (POL pressure opening level) under physiological conditions in laboratory mini pigs and under the influence of an i.v. organophosphorus compound (Paraoxon). The median POL in the untreated animals was 6.4 kPa (n 8). After intoxication with Paraoxon the median POL increased to 12.0 kPa (n 8). Tubal instillation of surfactant in intoxicated pigs reduced the POL to a median of 7.3 kPa (n8), while in non-intoxicated animals (n4) it also lowered the POL, though not significantly. These results suggest that organophosphorus compound interferes with the surfactant-dependant tubal patency.

Objective. To examine the ease of endotracheal intubation on the ground for various rescuer positions.Methods. Six female and 18 male emergency medical technicians were asked to intubate a Laerdal Megacode Trainer placed on the ground, Rescuers assumed the following positions in random order: prone, sitting, kneeling at the mannequin's head, and straddling the chest. The authors measured times 1) for changing from mask ventilation to assuming intubation position and 2) from touching the laryngoscope to putting it down. Incidences of esophageal tube placement and clicks (possible tooth damage) were noted. The rescuers rated their satisfaction with each position on a six-point scale (1 = very good, 6 = insufficient). Total intubation times of the other three positions were compared with that for prone by rank order test for paired observations. Handling, esophageal positions, and clicks of the other three positions were compared with those for prone by sign test for paired observations. A Bonferroni correction (factor 12) was applied.Results. Mean total intubation times (in seconds) were 11.8 ± 3.3 for prone, 13.9 ± 4.7 for sitting, 11.4 ± 4.5 for kneeling, and 16.2 ± 5.8 for straddling. The difference between straddling and prone was statistically significant (p < 0.005). For handling, the results were for prone 3.0 ± 1.4, for sitting 3.1 ± 1.1, for kneeling 2.2 ± 0.6, and for straddling 2.8 ± 1.4. Esophageal positions occurred for prone 1, for sitting 1, for kneeling 2, and for straddling 3. Clicks were counted for prone 2, for sitting 1, for kneeling 1, and for straddling 0.Conclusions. All tested positions provide satisfactory conditions for intubation on the ground. The straddling position requires statistically, but not clinically, significantly more time for intubation than does prone and may be an important backup position if access from behind the patient's head is impossible.

Objective. To examine the feasibility of closed chest compressions in ambulances.Methods. Ten male emergency medical technicians performed closed chest compressions on a Laerdal Skillmeter Resusci Anne placed 1) on the ground, 2) on the stretcher of an MB 510 ALS ambulance, 3) on the stretcher of an MB 310 ambulance, and 4) on the stretcher of a VW T4 BLS ambulance for 2 minutes each. The authors noted the percentage of correct compressions as shown by the mannequin and counted the heart rate of the participants before and after each session. The authors compared the percentage of correct compressions and the increase in heart rate during the three ambulance sessions with those of the session on the ground by rank order test for paired observations. A p < 0.05 after Bonferroni correction (factor 3) was considered significant.Results. The percentage of correct compressions was 90% ± 7% on the ground, 77% ± 19% in the MB 510,60% ± 31% in the MB 310, and 38% ± 24% in the VW T4. Heart rate increase was 18 ± 16 min-1 on the ground, 23 ± 9 min-1 in the MB 510,30 ± 16 min-1 in the MB 310, and 32 ± 13 min-1 in the VW T4. Only the difference in percentage of correct compressions between on the ground and the VW T4 was significant (p < 0.01 after Bonferroni correction).Conclusions. The percentage of correct compressions in all the vehicles tested was lower when compared with the percentage on the ground, and the increase in heart rate was higher. Only one of these results was statistically significant. A further study with more participants seems warranted.

Previous studies have shown increasing evidence that TGF-a, a ligand for the often overexpressed EGF-receptor may be important for the oncogenesis and autocrine stimulation of the proliferation in head and neck cancers. the occurrence of TGF-α and its relation to the EGF-receptor still remain unclear. Twenty six specimens (primaries and metastasis) of oropharyngeal squamous cell carcinomas were investigated for the presence of transforming growth factor alpha (TGF-α), epidermal growth factor (EGF) and the EGF-receptor using a tissue extraction method and a “sandwich” immuno absorbent assay. in 77 of the specimens we found TGF-α, all had a significant amount of EGF-receptors, no EGF was found. No significant difference was noted for metastasis and primaries. No correlation was seen to the TNM stage and to the histological grading. There was an inverse statistical correlation between the TGF-α and the EGF-receptor concentration. High TGF-α concentrations were associated with low EGF-receptor concentration. Interestingly, even high TGF-α concentrations showed a lower limit of EGF-receptor concentrations which could not be passed. the present investigation gives a quantitative determination of the EGF-receptors and TGF-α in oropharyngeal carcinomas. the results indicate that a EGF-receptor /TGF-α complex could be functionally important for autocrine/paracrine stimulation.

Abstract: This study examined the maternal and fetal blood kinetics of lead in pregnant, near term mini-pigs. A lead dose of 1 mg/kg was administered to the animals by i.v. injection as bolus. During the 5-h sampling period, the two-compartment maternal pharmacokinetics demonstrated a rapid phase T 1/2 of 8 min and a slower phase T1/2 of 199 min. Lead reached the fetus with a time lag of 81 min. At 24 h after administration the ratio of fetal to maternal blood lead concentration seemed to become stable. When lead was injected directly into the fetal blood circulation, the decay of fetal blood lead fitted a one-compartment model. The disappearance half-life was 92 min. Lead can obviously accumulate in fetal liver; the lead level in fetal brain showed no detectable changes. This study confirmed that lead can also pass through the epitheliochorial placenta.

Auteur(s) : Miriam Toomes1, Wolfgang H. Maleck2, Katharina P. Koetter3, Georg A. Petroianu4 1. Anesthesiology, University of Heidelberg at Mannheim, D‐68167 Mannheim, Germany 2. Anesthesiology, Klinikum Ludwigshafen, D‐67063 Ludwigshafen, Germany 3. Neurology, Klinikum Aschaffenburg, D‐63739 Aschaffenburg 4. Pharmacology, University of Heidelberg at Mannheim, D‐68169 Mannheim, Germany Correspondence: Prof. Georg A. Petroianu, United Arab […]