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ABSTRACT: An automated device is described to test the exploratory and motor activity of common marmosets (Callithrix jacchus). The device consists of four boxes interconnected by PVC tubes. The presence of an animal in a box is detected by a photocell. Calibration takes place with an electric model train. Movements of the animal from one box to another are detected by disappearance from one and appearance in another box. The apparatus is linked to a PC. The effects of two doses of methamphetamine and of pentobarbital are shown.
Pharmacology Biochemistry and Behavior 05/1994; 47(4):879-81. · 2.53 Impact Factor
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ABSTRACT: This mini-review mainly describes a part of the pharmacological research carried out in our laboratory during the past decades, aimed at finding a therapy against intoxication by cholinesterase-inhibiting organophosphates, in particular against the nerve agent soman. In particular soman, because this is one of the nerve agents that consistently appears to be very resistant to treatment. Various experimental approaches are described. Yet, even after all these years of research an adequate (pre)treatment against poisoning by soman is still not available.
Neuroscience & Biobehavioral Reviews 02/1994; 18(4):469-86. · 8.65 Impact Factor
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ABSTRACT: The therapeutic efficacy of the oxime HI-6 against intoxication with the irreversible cholinesterase (ChE) inhibitor soman was tested in marmoset monkeys. Five out of six marmosets, intoxicated with 5 x LD50 soman and treated immediately with diazepam (0.2 mg.kg-1 iv) and 15 sec later with atropine (0.5 mg.kg-1 im) and HI-6 (50 mg.kg-1 im), survived for more than 24 hr. One of these animals died after 4 days. In the HI-6-treated marmosets blood ChE activity was inhibited at a rate slower than that in three animals treated similarly but with saline instead of HI-6. The latter marmosets died within 8 min after soman. HI-6 achieved its plasma peak 5 min after injection and was eliminated with a t1/2 of about 40 min. In a second experiment similarly treated marmosets were euthanized at 5 min (three saline-treated animals) or at 10 min (three HI-6-treated animals) after the soman intoxication to enable the determination of acetylcholinesterase (AChE) activities in diaphragm and brain tissue. In addition, in these animals blood AChE and butyrylcholine esterase (BuChE) activities were determined. Low AChE activities were encountered in diaphragms and brains. These levels were not significantly different between saline- and HI-6-treated marmosets. In vitro treatment with HI-6 at 40 min after soman still led to an increase of the AChE activity, which was significant in diaphragm, suggesting that postmortem AChE inhibition had occurred. The ratio of AChE to BuChE in blood was significantly enhanced in HI-6-treated animals, indicating that HI-6 preferentially reactivated AChE. It is concluded that (i) HI-6 is an effective treatment against soman poisoning in marmosets and (ii) AChE reactivation or protection by HI-6 contributed to the survival of the animals.
Toxicology and Applied Pharmacology 08/1992; 115(1):50-6. · 4.45 Impact Factor
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ABSTRACT: To overcome most of the disadvantages of current models to investigate percutaneous penetration of drugs or toxic substances, a model is proposed here based on the isolated pig ear, which is obtained at the slaughterhouse, and perfused with oxygenated blood from the same pig. To determine the viability of the preparations, we measured glucose consumption and lactate production as metabolic parameters, Na+ and K+ ions, as well as lactate dehydrogenase activity in blood as markers for cell damage, whereas vasomotor reactivity was assessed by administering noradrenaline and isoxsuprine. After 60 min of equilibration, only insignificant changes in these parameters were observed during the subsequent 3-hr test period (longer periods were not tested). A slight weight increase was noted during the total period 4 hr, presumably due to slight edema formation. On the basis of several types of measurements, such as in vivo blood flow and ear temperature and in vitro glucose metabolism, standard procedures were developed. It is concluded that this technique offers an easy to handle, cost-efficient, and animal-saving model for skin penetration studies that lacks most of the disadvantages of existing models.
Journal of Pharmacological and Toxicological Methods 05/1992; 27(2):71-7. · 2.32 Impact Factor
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ABSTRACT: Several earlier studies showed that, in contrast with DFP, repeated injections with soman did not lead to behavioral tolerance in rats. The reason for the difference between the effects of these two organophosphate cholinesterase inhibitors was not clear and a neurophysiological approach was undertaken. Four experiments (A, B, C and D) were carried out, each consisting of three groups of rats, SC injected with saline, DFP (600 micrograms/kg) or soman (60 micrograms/kg) respectively. In Experiment B and D the rats were trained to criterion in a two-way shuttlebox. Thereafter, the animals of Experiment B were fitted with suitable electrodes and two days later their EEGs and visual evoked responses (VERs) were recorded, 1 and 24 h after a single dose of the above-mentioned compounds. In Experiment D the trained animals were subsequently injected 3 times per week for 4 weeks with the same doses and their performance was tested 5 days per week, 1 and 24 h after injection. After those 4 weeks, when the DFP-treated animals had developed behavioral tolerance, electrodes were fitted and EEGs and VERs were recorded after two days, again 1 and 24 h after injection, as in Experiment B. The difference with Experiments A and C was that these animals were not trained. Otherwise, treatment schedules and recording procedures of Experiment A were identical to those of Experiments B and of Experiment C to those of Experiment D. In all cases the EEGs and VERs were recorded from animals slowly walking in a rotating hollow transparent wheel. The results show a similar pattern in all four experiments.(ABSTRACT TRUNCATED AT 250 WORDS)
Pharmacology Biochemistry and Behavior 09/1991; 39(4):851-8. · 2.53 Impact Factor
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ABSTRACT: The development of tolerance to organophosphates (OPs) was investigated by SC injections of saline and sublethal doses of DFP or soman three times per week or every other day for at least 4 weeks. Shuttlebox performance was tested 1 hr and 24 hr after the injections. Notwithstanding a progressive inhibition of AChE to very low values in various organs, shuttlebox performance was virtually normal 24 hr after the OP injections. However, whereas the performance decrements measured 1 h after the injection of DFP practically disappeared in the course of weeks, the decrements 1 hr after soman remained approximately the same. These differences between the effects of DFP and soman cannot be explained: 1) by differences in inhibition or de novo synthesis of AChE in various regions of the CNS, the striated muscle or blood, 2) by differences in the reductions of the muscarinic receptors in various regions of the CNS, 3) by differences in the number of nicotinic receptors in the diaphragm muscle, or 4) by differences in phosphorylphosphatase (DFP-ase or somanase) activity in blood plasma or liver.
Pharmacology Biochemistry and Behavior 12/1989; 34(3):473-81. · 2.53 Impact Factor
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ABSTRACT: Whether the temporary retention of intact soman in the rat and its subsequent delivery from tissues into the circulation of the blood is also demonstrable in guinea-pigs and marmosets has been investigated as was whether the soman simulator PDP (pinacolyl dimethylphosphinate) prevented this retention. Electric eel AChE, intravenously injected 1.5 h after an intravenous soman intoxication into anaesthetized, atropinized and artificially ventilated guinea-pigs (150 micrograms kg-1 soman), marmoset monkeys (100 micrograms kg-1 soman) and rats (330 and 172.5 micrograms kg-1 soman) lost its activity faster than enzyme injected in non-intoxicated animals. Electric eel AChE incubated in the presence of pectoralis or diaphragm muscle isolated from soman-intoxicated rats, guinea-pigs and marmosets 0.5 or 1.5 h after the intoxication, was progressively inhibited, indicating that those muscles still delivered soman into the incubation medium. In rats, PDP (6.4 mg kg-1 i.v.) pretreatment was effective in preventing inhibition of intravenously injected electric eel AChE 1.5 h after intoxication with a high dose of soman (330 micrograms kg-1). But after intoxication with a low dose (172.5 micrograms kg-1), PDP pretreatment was ineffective in this action, however, it did lead to less soman delivery from muscle tissue isolated 30 min following the 172.5 micrograms kg-1 soman intoxication, suggesting that there was less soman in the tissue. In PDP (6.4 mg kg-1 i.v.)-pretreated marmosets (100 micrograms kg-1 soman) and guinea-pigs (150 micrograms kg-1 soman), to the contrary, the trend was for the injected AChE to be more inhibited, whereas only slightly less soman was delivered from isolated muscle tissue.(ABSTRACT TRUNCATED AT 250 WORDS)
Journal of Pharmacy and Pharmacology 02/1988; 40(1):35-41. · 2.17 Impact Factor
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ABSTRACT: Because of the lack of agreement about the effects of topically applied antiviral agents on herpes simplex virus (HSV) skin infections in humans and in animals, an in-vivo human skin model of infection was developed. Human skin was grafted on to congenitally athymic nude mice and the therapeutic effects of topically applied viral DNA polymerase inhibitor phosphonoformate (foscarnet) on the course of the disease were studied. Following infection with HSV, the human skin grafts developed herpes vesicles similar to those seen in human skin in situ. Vesicles developed within three days of inoculation, and coalesced and crusted over by the fifth day post-inoculation. Healing of the wound did not occur and non-treated animals died approximately 13 days after inoculation. Treatment with topically applied foscarnet starting 24 h after inoculation suppressed both the development of the clinical signs of the disease and the replication of HSV in the grafted human skin. However, when therapy was withdrawn the symptoms of the disease proceeded to develop. Late onset (day two post-inoculation) of the foscarnet treatment was without effect on the course of the disease. Because foscarnet showed an antiviral effect when applied to infected human skin, the lack of effect of foscarnet in clinical studies on recurrent genital or labial herpes may be due to differences in the pathogenesis of the primary and recurrent infections.
Journal of Antimicrobial Chemotherapy 11/1987; 20(4):547-56. · 5.07 Impact Factor
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ABSTRACT: The interaction of C(+/-)P(+/-)-soman (pinacolyl methylphosphonofluoridate) and its individual stereoisomers with serum carboxylic-ester hydrolase and potentiation of their toxicity by a carboxylic-ester hydrolase inhibitor CBDP (2-(2-methylphenoxy)-4H-1,3,2-benzodioxaphosphorin-2-oxide) was investigated. C(+/-)P(+/-)-Soman and the individual stereoisomers all inhibited purified mouse serum carboxylic-ester hydrolase to different degrees. C(+/-)P(+/-)-Soman and the C(-)P(-)- and C(+)P(-)-isomers had Ki values of 30.6, 18.7, and 35.7 nM, respectively, and C(-)P(+)- and C(+)P(+)-isomers had Ki values of 1412 and 2523 nM, respectively. In toxicity experiments CBDP (0.5 mg/kg; iv 1 hr prior to soman) pretreatment potentiated the toxicity of C(+/-)P(+/-)-, C(+)P(-)-, and C(-)P(-)-soman to a similar degree. Thus, it appears that the toxic stereoisomers of soman have a similar affinity for mouse serum carboxylic-ester hydrolase, and CBDP pretreatment does not enhance selectively the toxicity of one stereoisomer over the other.
Toxicology and Applied Pharmacology 07/1987; 89(1):141-3. · 4.45 Impact Factor
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ABSTRACT: Diaphragms isolated from rats 60 or 120 min after the intravenous injection of 6 X LD50 soman were incubated with electric eel acetylcholinesterase. As calculated from the enzyme inhibition, detectable amounts of P(-)-soman (1,2-dimethylpropyl methylphosphonofluoridate) were released from the diaphragm into the medium even 120 min post-injection. This release was reduced by additional pretreatment of the rats with pinacolyl dimethylphosphinate, providing further evidence that this compound prevents the storage of soman in diaphragm tissue.
European Journal of Pharmacology 09/1986; 127(1-2):135-8. · 2.52 Impact Factor
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ABSTRACT: Atropinized rats, intoxicated with 6 or 8 X LD50 soman and subsequently treated with the oxime HI-6 died several hours after intoxication. Oral or intravenous administration of the soman-simulator, pinacolyl dimethylphosphinate (PDP), given at progressively increasing time intervals before soman, appeared to be very active in preventing death and secondary failure of neuromuscular transmission that followed HI-6-induced recovery. Therapeutically, PDP was only effective when given immediately after soman intoxication and oxime treatment. In animals that received no treatment otherwise, intravenous administration of PDP 10 min before intoxication with 1 X LD50 soman did not enhance lethality.
Journal of Pharmacy and Pharmacology 07/1986; 38(6):439-45. · 2.17 Impact Factor
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ABSTRACT: The effects were investigated of structural variations of the soman simulator pinacolyl dimethylphosphinate on its efficacy to prevent secondary failure of oxime-induced recovery of neuromuscular transmission and death after soman intoxication. The simulators were administered prophylactically to atropinized, HI-6 treated rats, dosed with 6 or 8 X LD50 soman. In these new simulators the pinacolyl moiety was varied, the phosphonyl oxygen atom was replaced by sulphur, or the phosphorous-bound methyl groups were replaced by ethyl or methoxy groups. All these variations appeared to be less active than pinacolyl dimethylphosphinate. Intravenously, the latter compound was very effective at a dose of 12 mumol kg-1; its i.v. LD50 appeared to be higher than 1 mmol kg-1.
Journal of Pharmacy and Pharmacology 02/1986; 38(1):19-23. · 2.17 Impact Factor
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ABSTRACT: The extrapolation of the results of measurements of skin penetration or skin damage with current in vitro and in vivo animal models to humans is of questionable value. Therefore, the usefulness of two other models is being evaluated: human skin grafts on congenitally athymic mice and cultures of human epidermal cells. The results show that histologically and immunologically the human skin grafts retain their "human" characteristics for at least 6 months. In contrast to animal skin these grafts also form blisters in response to heat and microblisters in response to sulfur mustard. By comparing blood cholinesterase (CHE) activity after epicutaneous, subcutaneous, and intravenous administration of soman in intact and (auto- or homo-) grafted mice it appears that the transplantation process itself does not influence penetration speed, nor does it affect the total amount of soman that ultimately reaches the blood. When applied on the human skin graft, soman penetration is slower and CHE inhibition in blood has not reached a plateau value after 2 1/2 hr. Substantial amounts of soman are metabolized in the skin. With epidermal cell cultures the different mechanisms of action of the mycotoxin T2 and that of tributyltin (TBT) can be demonstrated. In a young growing culture, 10(-8) M T2 completely blocks the increase in the number of epidermal cells, whereas the same concentration of TBT has no effect. In a fullgrown culture, however, 5 X 10(-5) M TBT causes membrane damage, detectable by the leakage of lactate dehydrogenase (LDH) into the medium, whereas the same concentration of T2 has no effect. Moreover the differential effects of TBT on cytoplasmic and lysosomal membranes can be demonstrated by measuring the rates at which the cytoplasmic marker enzyme LDH and the lysosomal marker enzyme N-acetyl-beta-glucosaminidase appear in the medium. From the results obtained so far it is concluded that these two models have quite a number of promising features for dermatotoxicity testing.
Fundamental and Applied Toxicology 01/1986; 5(6 Pt 2):S98-111.
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ABSTRACT: The effects of CNS-active drugs and neurotoxic agents on motor coordination in the rat were studied using a newly developed, automated technique. In this test, a tv/microprocessor-based system was utilized to detect and describe the movement and placement characteristics of one of the rat's hindpaws as the rat placed its paw from one rung to another while walking in a rotating wheel. In studies employing a wheel speed of 8.2 cm/sec and a single 90-sec trial, significant deficits in coordinated hindlimb movement could be detected following the acute ip administration of a variety of compounds, including acrylamide (0, 50, and 100 mg/kg), diazepam (0, 0.5, 1.0, and 2.0 mg/kg), ethyl alcohol (0, 600, 900, and 1200 mg/kg), and tremorine (0, 2.5, 5.0, and 10.0 mg/kg). Further, results from a subacute study involving the oral administration of 2,5-hexanedione (2,5-HD; 0, 250, and 600 mg/kg) indicated that rats treated with 600 mg/kg, 2,5-HD were significantly impaired after 1 week of treatment and those treated with 250 mg/kg 2,5-HD, after 2 weeks of treatment. Although both groups improved during the recovery period, the performance of the 600 mg/kg group 5 weeks post-treatment was still inferior to controls. Taken together, these studies indicate that the coordinated hindlimb placement test provides a reliable, sensitive, and rapid technique for quantifying deficits in motor coordination in the rat during acute and prolonged exposure to neurotoxic substances.
Toxicology and Applied Pharmacology 09/1985; 80(1):1-10. · 4.45 Impact Factor
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ABSTRACT: The oxime HI-6 is effective as an antidote in the soman poisoned (6-8LD50) rat, however, successfully treated animals subsequently show a gradual relapse of signs of poisoning and eventually die after several hours. The relapse is caused by the reappearance of soman at specific sites, after having been elsewhere in the body. Diaphragms isolated from poisoned rats successfully treated with HI-6 also showed a 'secondary' relapse of poisoning. Eight compounds chemically related to soman-soman-simulators--have been tested as prophylactic agents, for their potency in preventing the reappearance of poisoning. The idea was that such compounds may block the non-synaptic binding sites for soman. Three of the 8 compounds proved very effective, which gave some insight into the chemical structure needed for this type of prophylactic action.
Journal of Pharmacy and Pharmacology 06/1984; 36(5):305-8. · 2.17 Impact Factor
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ABSTRACT: In rats the acute effects of low doses of five cholinesterase (ChE) inhibitors were investigated in six behavioral tests. Considerable differences were found between the inhibitors studied. TEPP and sarin at doses up to 30% LD50 were without effects. In contrast, soman, physostigmine, and pyridostigmine caused effects at dose levels which did not produce overt symptoms and did not affect running speed and simple coordinated locomotion. Soman (less than or equal to 3% LD50), physostigmine (less than or equal to 4.5% LD50), and pyridostigmine (less than or equal to 10% LD50) interfered with two-way shuttlebox avoidance learning, open field behavior, and complex coordinated movements ( hurdle -stepping task). Tests of retention in a passive avoidance learning test appeared less sensitive. It is concluded that paradigms that involve higher CNS structures and require motor activity are sensitive to some ChE inhibitors at doses far below those that cause overt symptoms. The individual characteristics of ChE inhibitors play an important role. In contrast to TEPP and sarin, soman has a predominantly central effect. Further, the finding that pyridostigmine was also effective at unexpectedly low dose levels suggests that this compound may have more central actions than hitherto accepted.
Fundamental and Applied Toxicology 05/1984; 4(2 Pt 2):S195-208.
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ABSTRACT: Disturbances of motor coordination are usually difficult to quantify. Therefore, a method was developed for the automated quantitative analysis of the movements of the dyed paws of stepping rats, registered by a colour TV camera. The signals from the TV-video system were converted by an electronic interface into voltages proportional to the X- and Y-coordinates of the paws, from which a desktop computer calculated the movements of these paws in time and distance. Application 1 analysed the steps of a rat walking in a hollow rotating wheel. The results showed low variability of the walking pattern, the method was insensitive to low doses of alcohol, but was suitable to quantify overt, e.g. neurotoxic, locomotor disturbances or recovery thereof. In application 2 hurdles were placed in a similar hollow wheel and the rats were trained to step from the top of one hurdle to another. Physostigmine-induced disturbances of this acquired complex motor task could be detected at doses far below those that cause overt symptoms.
Journal of Neuroscience Methods 04/1984; 10(3):237-45. · 1.98 Impact Factor
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ABSTRACT: Isolated rat diaphragms were treated with the oxime HI-6, 25 min after the start of soman exposure for 5, 15, 20 or 25 min. Recovery of neuromuscular transmission (NMT) was smaller and the subsequent spontaneous failure of NMT greater when soman exposure was longer. Diaphragms taken from anaesthetized atropinized soman-poisoned rats treated with HI-6 again showed spontaneous failure of NMT when tested repeatedly in vitro. In vivo pretreatment with a soman simulator prevented reinhibition in vitro. The results are indicative of a simulator-sensitive soman depot in muscles.
European Journal of Pharmacology 06/1983; 89(3-4):271-4. · 2.52 Impact Factor
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ABSTRACT: 1 The ability of various bis-pyridinium oximes to restore organophosphate-inhibited neuromuscular transmission in vitro was compared in human intercostal and marmoset diaphragm muscles. 2 HI-6 (2-hydroxyiminomethyl-pyridinium-1-methyl-4'-carbamoyl-pyridinium-1'-methyl ether dichloride monohydrate) appeared very effective against VX (O-ethyl S-2-diisopropylaminoethyl methylphosphonothioate) and sarin in both muscles, whereas obidoxim was quite effective against tabun. 3 Against soman, HI-6, HS-6 (2-hydroxyiminomethyl-pyridinium-1-methyl-3'-carbamoyl-pyridinium-1'-methyl ether dichloride dihydrate) and obidoxim had little effect in the human muscle and only slight activity in the marmoset muscle; HGG-12 (2-hydroxyiminomethyl-pyridinium-1-methyl-3'-phenylcarbonyl-pyridinium-1'-methy l ether dichloride) and benzyl-P2A (1-benzyl-2-hydroxyiminomethyl-pyridinium methanesulphonate) were ineffective. 4 Anaesthetized, atropinized marmosets were poisoned with soman (4 X LD50, i.v.) and subsequently treated with HI-6, HS-6 or HGG-12. Only HI-6 and HS-6 were marginally effective in restoring respiration and neuromuscular transmission. 5 Marmoset muscle is a reasonable model for human muscle for the study of organophosphate poisoning and therapy.
British Journal of Pharmacology 04/1983; 78(3):579-89. · 4.41 Impact Factor
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ABSTRACT: This study was carried out to evaluate the rhesus monkey as a model for man with respect to oxime-induced acetylcholinesterase reactivation as a mechanism contributing to restoration of soman poisoned neuromuscular function. In-vitro neuromuscular blockade in intercostal and diaphragm muscle strips of rhesus monkeys was induced by exposing them for 2.5 or 15 min to the cholinesterase inhibitor soman. Subsequent treatment with the oxime HI6 produced only a partial reversal of this blockade. Only a minor part of the recovery obtained could be attributed to enzyme reactivation and suggested that this species responded in a manner closer to that reported in man than other animal species studied.
Journal of Pharmacy and Pharmacology 04/1983; 35(3):157-60. · 2.17 Impact Factor
