Young Cho

Minimum effective drug concentrations of a transdermal patch system containing procyclidine and physostigmine for prophylaxis against soman poisoning in rhesus monkeys.

A transdermal patch system containing procyclidine, an N-methyl-d-aspartate receptor antagonist possessing anticholinergic action, and physostigmine, a reversible cholinesterase inhibitor, was developed, and its prophylactic efficacy against soman intoxication was investigated. Male rhesus monkeys were shaved on the dorsal area, attached with a matrix-type patch with various sizes (2×2 to 7×7 cm) for 24 or 72 h, and challenged with 2×LD₅₀ doses (13μg/kg) of soman. The smallest patch size for the protection against lethality induced by soman intoxication was 3×3cm, resulting in blood procyclidine concentration of 10.8 ng/ml, blood physostigmine concentration of 0.54 ng/ml, which are much lower concentrations than maximum sign-free doses, and blood cholinesterase inhibition of 42%. The drug concentrations and enzyme inhibition rate corresponding to a diverging point of survivability were presumably estimated to be around 7 ng/ml for procyclidine, 0.35 ng/ml for physostigmine, and 37% of enzyme inhibition. Separately, in combination with the patch treatment, the post treatment consisting of atropine (0.5 mg/kg) plus 1-[([4-(aminocarbonyl)pyridinio]methoxy)methyl]-2-[(hydroxyimino)methyl]pyridinium (HI-6, 50 mg/kg) exerted protection against 5×LD₅₀ challenge of soman, which means the posttreatment remarkably augmented the efficacy of the patch. Additionally, it was found that brain injuries induced by soman toxicity were effectively prevented by the patch treatment according to histopathological examinations. These results suggest that the patch system could be an effective alternative for diazepam, an anticonvulsant, and the current pyridostigmine pretreatment, and especially in combination with atropine plus HI-6, could be a choice for quality survival from nerve-agent poisoning.

Hydration number of calcium palmitate LB film deposited on a piezoelectric quartz crystal plate

Abstract The calcium palmitate monolayer formed from palmitic acid on calcium-containing substrate can be examined regarding the study of hydration by applying the quartz crystal microbalance (QCM) technique. Monolayers of calcium palmitate were deposited on piezoelectric crystal plate by the Langmuir-Blodgett (LB) technique. Analysis of complete conversion to calcium palmitate was performed by identification of its infrared spectra. The estimation of the hydration for the multilayered calcium palmitate is compared with the data of the multilayered calcium stearate in the literature. The QCM measurement for determining hydration number is based on the results of McCaffrey, particularly employed in the treatment of drying in vacuum (R.R. McCaffrey, S. Bruckenstein, P.N. Prasad, Langmuir 2 (1986) 228). In our experiments, the frequency change of the oscillating quartz transducer for the skimmed calcium palmitate also increased after drying in vacuum. Hydration behavior of the multilayered calcium palmitate LB film is discussed, and it was shown that the hydration of calcium palmitate exists as monohydrate, though its hydrophobicity is relatively a little low compared with that of calcium stearate, which has a longer hydrocarbon chain length.

Differential inhibition of soluble and membrane-bound acetylcholinesterase forms from mouse brain by choline esters with an acyl moiety of an intermediate size

Differential inhibitions of soluble and membrane-bound acetylcholinesterase forms purified from mouse brain were examined by the comparison of kinetic constants such as a Km value, a Kss value (substrate inhibition constant), and IC50 values of active site-selective ligands including choline esters. Membrane-bound acetylcholinesterase form (solubilized only in the presence of detergent) showed lower Km and Kss values than soluble acetylcholinesterase form (easily solubilized without detergent). Edrophonium expressed a slightly but significantly (p<0.01) higher inhibition of detergent-soluble acetylcholinesterase form than aqueous-soluble acetylcholinesterase form, while physostigmine inhibited both forms with a similar potency. A remarkable difference in inhibition was observed using choline esters; although choline esters with acyl chain of a short size (acetyl-to butyrylcholine) or a long size (heptanoyl- to decanoylcholine) showed a similar inhibitory potency for two forms of acetylcholinesterase, pentanoylcholine and hexanoylcholine inhibited more strongly aqueous-soluble acetylcholinesterase than detergent-soluble acetylcholinesterase. Thus, it is suggested that the two forms of AChE may be distinguished kinetically by pentanoyl- or hexanoylcholine.

Properties of acetylcholinesterase reconstituted in liposomes of a different charge.

Acetylcholinesterase (AChE) purified from mouse brain was reconstituted in liposomes of a different charge, and the properties of liposome-associated AChE were investigated. Relative to the Km value (38.5 μM) of AChE bound to a neutral liposome, the value of AChE reconstituted in a negatively-charged liposome decreased to 23.3 μM, whereas that of AChE in a positively-charged liposome increased to 90.9 μM. Additionally, AChE bound to a positively-charged liposome expressed a wider range of optimum pH than the enzyme in a negatively-charged liposome. In a stability study, it was found that soluble AChE was unstable at pH 5.5 and 7.4, while it was relatively stable at pH 10. Noteworthy, the immobilization of AChE to liposome enhanced the stability of soluble enzyme at acidic and neutral pH. Moreover, in the stabilization of the enzyme, a neutral liposome was more effective than charged liposomes, of which a positively-charged liposome was more effective than a negatively-charged liposome at acidic pH. Based on these results, it is proposed that while the Km value and the pH dependence of AChE activity are affected by the charge of liposome, the stability of AChE is determined mainly by a hydrophobic binding to a phospholipid membrane.

In-situ studying of C60 Langmuir-Blodgett films deposited on a quartz crystal microbalance

Abstract Buckminsterfullerene(C 60 ) has been investigated at the air-water interface using Langmuir trough. Surface pressure-Area(π - A) isotherm showed differing properties. Particularly, the area/molecule of C 60 was more diminished than expected. Quartz crystal microbalance(QCM) was applied to in-situ weighing of Langmuir-Blodgett(LB) films transferred from water surface, and suggested that C 60 film does not exist in the form of a monolayer at the air-water interface. In-situ weighing could also examine the extent of multilayer formation of C 60 molecules at the air-water interface.

A Study on the Anticonvulsant Effects of Centrally-Acting Drugs by Measuring Electroencephalography of Experimental Animals Intoxicated with Organophosphate Compounds

Organophosphorus compounds are irreversible inhibitors of cholinesterase enzyme. Exposure causes a progression of toxic signs, including hypersecretion, tremor, convulsion, respiratory distress, epileptiform seizure, brain injuries and death. To protect brain injuries, administration of diazepam as a neuroprotectant is now considered essential for severely exposed nerve agent casualties. However, studies have shown diazepam to provide less than total protection against the neuropathological consequences of nerve agent exposure. In this context, extensive studies have been carried out to find out effective alternative drugs to protect brain from epileptiform seizures induced by organophosphate compounds intoxication. It has been reported that a combination of carbamate and anticholinergic or antiglutamatergic can be a very effective medical countermeasure in dealing with the threat of organophosphorous poisoning. In this study, experimental animals including rats and guinea pigs were implanted with microelectrodes on their brain sculls, and treated with various centrally acting drugs such as physostigmine and procyclidine prior to soman challenge, and then its electroencephalography(ECoG) was monitored to see anticonvulsant effects of the drugs. It was found that seizure activities in ECoG were not always in proportion to clinical signs induced by soman intoxication, and that combinative pretreatment with physostigmine plus procyclidine effectively stopped the seizures induced by organophosphorous poisoning.Keywords : Anticonvulsant(항경련제), Seizure(발작), Electroencephalography(뇌파), Procyclidine(프로사이클리딘), Physostigmine( 피소스티그민), Prophylactic(예방), Soman(신경작용제 GD), Poisoning(중독)

Investigation of the Pharmacological Mechanisms and the R&D of Medical Countermeasures Against Nerve Agent Poisoning

Nerve agents are irreversible inhibitors of the cholinesterase enzyme. Exposure causes a progression of toxic signs, including hypersecretions, fasciculations, tremor, convulsions, respiratory distress, epileptiform seizures, brain injuries and death. A combined regimen of prophylaxis and therapy is the most effective medical countermeasure for dealing with the threat of nerve agent poisoning to military personnel. In this paper, the author investigated the updated technologies regarding various pre- and post-treatment drugs for nerve agents detoxification which are under development in several countries including Korea. Some characteristics of active ingredients in the formulations of drugs, their action mechanisms, and effectiveness were analyzed. Additionally, part of experimental data on the transdermal patch studied in ADD using beagle dogs was introduced.