Tacrine and its 7-methoxy derivate; time-change concentration in plasma and brain tissue and basic toxicological profile in rats.

The search for tacrine derivatives, as potential Alzheimer´s disease treatment, is still being at the forefront of scientific efforts. 7-MEOTA was found to be a potent, centrally active acetylcholinesterase inhibitor free of the serious side effects observed for tacrine. Unfortunately, a relevant argumentation about pharmacokinetics and potential toxicity is incomplete; information about tacrine derivatives absorption and especially CNS penetration are still rare as well as detailed toxicological profile in vivo. Although the structural changes between these compounds are not so distinctive, differences in plasma profile and CNS targeting were found. The maximum plasma concentration were attained at 18th min (tacrine; 38.20 ± 3.91 ng/ml and 7-MEOTA; 88.22 ± 15.19 ng/ml) after i.m. application in rats. Although the brain profiles seem to be similar; tacrine achieved 19.34 ± 0.71 ng/ml in 27 min and 7-MEOTA 15.80 ± 1.13 ng/ml in 22 min; the tacrine Kp (AUCbrain/AUCplasma) fit 1.20 and was significantly higher than 7-MEOTA Kp 0.10. Administration of tacrine and 7-MEOTA showed only mild elevation of some biochemical markers following single p.o. application in 24 hours and 7 days. Also histopathology revealed only mild-to-moderate changes following repeated p.o. administration for 14 days. It seems that small change in tacrine molecule leads to lower ability to penetrate through the biological barriers. The explanation that lower p.o. acute toxicity of 7-MEOTA depends only on differences in metabolic pathways may be now revised to newly described differences in pharmacokinetic and toxicological profiles.

Simple validated method of LC-MS/MS determination of BZ agent in rat plasma samples.

Agent BZ (3-quinuclidinyl benzilate) is a centrally acting synthetic anticholinergic agent, considered as a potential military incapacitating chemical warfare agent. Despite its significance as a model compound in pharmacological research and its potential misuse in chemical attacks, few modern analytical methods for BZ determination in biological samples have been published. The goal of the present work is to develop and validate a sensitive and rapid LC-MS/MS method for the determination of agent BZ in rat plasma. The sample preparation was based on solid-phase extraction on C-18 cartridges. The reversed-phase HPLC coupled with the mass spectrometer with electrospray ionization in the positive ion-selective reaction monitoring mode was employed in the BZ analysis. Atropine was used as an internal standard. The presented method is selective, accurate, precise, and linear (r2 = 0.9947) in a concentration range from 0.5 ng/mL to 1 000 ng/mL and sensitive enough (limit of detection 0.2 ng/mL; limit of quantification 0.5 ng/mL) to determine the BZ plasma levels in rats exposed to 2 mg/kg and 10 mg/kg of BZ. The highest level of BZ in plasma was observed 5 minutes after intramuscular administration (154.6 ± 22.3 ng/mL in rats exposed to 2 mg/kg of BZ and 1024 ± 269 ng/mL in rats exposed to 10 mg/kg). After 48 h, no BZ was observed at detectable levels. This new method allows the detection and quantification of BZ in biological samples after exposure of an observed organism and it will be further optimized for other tissues to observe the distribution of BZ in organs.

Pharmacological and toxicological in vitro and in vivo effect of higher doses of oxime reactivators.

The major function of compounds with an oxime moiety attached to a quarternary nitrogen pyridinium ring is to reactivate acetylcholinesterase inhibited by organophosphorus agent (OP). However, other oxime mechanisms (e.g. modulation of cholinergic or glutamatergic receptor) may be involved in the recovery. The main disadvantage of positively charged reactivators is their low ability to penetrate into the brain although crossing the blood brain barrier could be supported via increasing the dose of administered oxime. Thus, this study presents maximal tolerated doses (MTD) for marketed oximes (TMB-4, MMB-4, LüH-6, HI-6, 2-PAM) and the most promising K-oximes (K027, K048, K203) which can be used in OP therapy in the future. No signs of sarin intoxication were observed in mice treated with 100% MTD of HI-6 in contrast to those treated with atropine and only 5% LD50 of HI-6. 100% MTD of HI-6 resulted in levels of 500 µM and 12 µM in plasma and brain, respectively. This concentration is by a far margin safe with respect to direct effects on neuronal cell viability and, on the other hand, does not have any effects on central NMDA receptors or central nACh receptors. However, a weak antimuscarinic activity in case of LüH-6 and a weak peripheral antinicotinic action in case of TMB-4 and 2-PAM could be observed at their respective 100% MTD dose. These high doses, represented by MTD, are, however, irrelevant to clinical practice since they led to mild to moderate toxic side effects. Therefore, we conclude that clinically used doses of marketed oxime reactivators have no significant direct pharmacological effect on the tested receptors.

The Concentration of Memantine in the Cerebrospinal Fluid of Alzheimer's Disease Patients and Its Consequence to Oxidative Stress Biomarkers.

Memantine is a noncompetitive N-methyl-d-aspartate (NMDA) receptor antagonist utilized as a palliative cure for Alzheimer's disease. This is the second study examining the memantine concentrations in cerebrospinal fluid. The previously published study enrolled six patients, and three of them were theoretically in a steady state. In our study, we enrolled 22 patients who regularly used a standard therapeutic dose of memantine (20 mg/day, oral administration) before the sample collection. Patients were divided into four groups, according to the time of plasma and cerebrospinal fluid collection: 6, 12, 18, and 24 h after memantine administration. The cerebrospinal fluid samples were also assessed for selected oxidative stress parameters (malondialdehyde, 3-nitrotyrosine, glutathione, non-protein thiols, and non-protein disulfides). The plasma/cerebrospinal fluid (CSF) ratio for all time intervals were within the range of 45.89% (6 h) to 55.60% (18 h), which corresponds with previously published findings in most patients. The other aim of our study was to deduce whether the achieved "real" memantine concentration in the central compartment was sufficient to block NMDA receptors. The IC50 value of memantine as an NMDA antagonist is in micromolar range; the lowest limit is 112 ng/ml (GluN2C), and this value was achieved only in three cases. The memantine cerebrospinal fluid concentration did not reach one quarter of the IC50 value in five cases (one patient was excluded for noncompliance); therefore, the potency of memantine as a therapeutic effect in patients may be questionable. However, it appears that memantine therapy positively affected the levels of some oxidative stress parameters, especially non-protein thiols and 3-nitrotyrosine.

Novel tacrine-tryptophan hybrids: Multi-target directed ligands as potential treatment for Alzheimer's disease.

A combination of tacrine and tryptophan led to the development of a new family of heterodimers as multi-target agents with potential to treat Alzheimer's disease. Based on the in vitro biological profile, compound S-K1035 was found to be the most potent inhibitor of human acetylcholinesterase (hAChE) and human butyrylcholinesterase (hBChE), demonstrating balanced IC50 values of 6.3 and 9.1 nM, respectively. For all the tacrine-tryptophan heterodimers, favorable inhibitory effect on hAChE as well as on hBChE was coined to the optimal spacer length ranging from five to eight carbon atoms between these two pharmacophores. S-K1035 also showed good ability to inhibit Aß42 self-aggregation (58.6 ±â€¯5.1% at 50 µM) as well as hAChE-induced Aß40 aggregation (48.3 ±â€¯6.3% at 100 µM). The X-ray crystallographic analysis of TcAChE in complex with S-K1035 pinpointed the utility of the hybridization strategy applied and the structures determined with the two K1035 enantiomers in complex with hBChE could explain the higher inhibition potency of S-K1035. Other in vitro evaluations predicted the ability of S-K1035 to cross blood-brain barrier and to exert a moderate inhibition potency against neuronal nitric oxide synthase. Based on the initial promising biochemical data and a safer in vivo toxicity compared to tacrine, S-K1035 was administered to scopolamine-treated rats being able to dose-dependently revert amnesia.

Orexin supplementation in narcolepsy treatment: A review.

Narcolepsy is a rare, chronic neurological disease characterized by excessive daytime sleepiness, cataplexy, vivid hallucinations, and sleep paralysis. Narcolepsy occurs in approximately 1 of 3000 people, affecting mainly adolescents aged 15 to 30 years. Recently, people with narcolepsy were shown to exhibit extensive orexin/hypocretin neuronal loss. The orexin system regulates sleep/wake control via complex interactions with monoaminergic, cholinergic and GABA-ergic neuronal systems. Currently, no cure for narcolepsy exists, but some symptoms can be controlled with medication (eg, stimulants, antidepressants, etc). Orexin supplementation represents a more sophisticated way to treat narcolepsy because it addresses the underlying cause of the disease and not just the symptoms. Research on orexin supplementation in the treatment of sleep disorders has strongly increased over the past two decades. This review focuses on a brief description of narcolepsy, the mechanisms by which the orexin system regulates sleep/wake cycles, and finally, possible therapeutic options based on orexin supplementation in animal models and patients with narcolepsy.

The benefit of combinations of oximes for the ability of antidotal treatment to counteract sarin-induced brain damage in rats.

BACKGROUND: The aim of our study was to compare the ability of two combinations of oximes (HI-6 + trimedoxime and HI-6 + K203) with atropine to counteract acute sarin-induced brain damage with the efficacy of antidotal treatment involving single oxime (HI-6) and atropin using in vivo methods. METHODS: Brain damage and neuroprotective effects of antidotal treatment were evaluated in rats poisoned with sarin at a sublethal dose (108 µg/kg i.m.; 90% LD50) using histopathological, Fluoro-Jade B and Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analysis 24 h after sarin administration. RESULTS: Both combinations of oximes reduce the number of rats that died before the end of experiment compared to non-treated sarin poisoning and sarin poisoning treated with HI-6 and atropine. In the case of treatment of sarin poisoning with HI-6 in combination with K203, all rats survived till the end of experiment. HI-6 with atropine was able to reduce sarin-induced brain damage, however, both combinations were slightly more effective. CONCLUSIONS: The oxime HI-6 in combination with K203 and atropine seems to be the most effective. Thus, both tested oxime combinations bring a small benefit in elimination of acute sarin-induced brain damage compared to single oxime antidotal therapy.

Cholinesterase Inhibitor 6-Chlorotacrine - In Vivo Toxicological Profile and Behavioural Effects.

BACKGROUND: 6-chlorotacrine is a cholinesterase inhibitor showing good inhibitory potential, even better than parent compound tacrine, in vitro. Despite tacrine scaffold is broadly used for design and synthesis of novel compounds with anti-Alzheimer's potential, no in vivo effects have been investigated so far. Thus, basic toxicological and behavioural evaluation has been carried out throughout this study. METHODS: Maximum tolerated dose (MTD) and median lethal dose (LD50) were assessed in BALB/c mice and Wistar rats. Behavioural effects were observed in rats performing the multiple T-maze test, the water maze test and the step-through passive avoidance test. All outcomes were compared with the effects of parent compound - tacrine. RESULTS: The toxicity of 6-chlorotacrine was increased compared to tacrine with MTD 6.0/5.0 mg.kg-1 (i.m., male/female mice), 6.0/5.0 mg.kg-1 (i.p., male/female rats) and LD50 9.0 mg.kg-1 (male rats). At MTD doses, no histopathological changes and blood biochemistry abnormalities were observed except decreased plasma creatinine levels. 6-chlorotacrine showed good effects in the reversal of quinuclidinyl benzilate-induced amnesia. Best results were achieved at the dose of 1.8 mg.kg-1 (20% LD50) in the water maze test; the pro-cognitive effect was stronger than that of tacrine (5.2 mg.kg-1, 20% LD50). Other doses tested (0.9 mg.kg-1 and 2.7 mg.kg-1) showed similar effects as tacrine in the water maze, multiple T-maze and passive avoidance test. CONCLUSION: Observed effects predetermined 6-chlorotacrine as a potent parent compound for the synthesis of novel multifactorial drugs intended to the treatment of Alzheimer's disease. Even though 6- chlorotacrine showed in vivo beneficial effect with no signs of toxicity, further tests on the field of biochemistry and pharmacology are essential to disclose the exact mechanism of action, safety evaluation and the metabolic fate of the compound after the repeated administration.

In vitro skin decontamination of paraoxon - wet-type cleansing effect of selected detergents.

The aim of this study was to determine optimal conditions for in vitro skin decontamination using water and detergents as decontamination agents and to test the cleansing efficiency of selected detergents. Experiments were performed using a peristaltic pump for showering of pig skin in modified static diffusion cells. Several conditions were tested including different flow rates (from 5 to 33 ml s-1), quantity of rinsing fluid (from 40 to 400 ml) and concentration of detergents (2; 5; 10%). Further, several types of detergents/commercial decontamination agents were evaluated under the selected conditions to find the most effective means of decontamination. The amount of paraoxon removed from the skin surface following wet-type decontamination was detected in the rinsing fluid spectrophotometrically after hydrolysis of paraoxon - a model contaminant. The efficacy of rinsing by water/Spolapon AES 253 increased with flow rate up to 25 ml s-1 and a rinsing volume of 200 ml. Lutensol AT 25 achieved maximum efficacy at the lowest tested concentration (2%). A flow rate of 16 ml s-1, rinsing volume of 100 ml (values from the middle part of the sigmoid curve) and 5% concentration of decontaminant solution were used for further evaluation of detergents as cleansing agents under the selected conditions. Cetylpyridinium bromide (cationic surfactant), carbethopendecinii bromidum (cationic surfactant) and polyoxyethylene-10-tridecyl ether (non-ionic surfactant), SDS (anionic surfactant), althosan MB (cationic surfactant), sodium dodecylbenzene sulphonate (anionic surfactant), neodekont (mixture), tergitol NPX (non-ionic surfactant), Korynt P (non-ionic surfactant) were found to be the most effective. These decontaminants were able to wash away more than 92% of paraoxon from the contaminated skin.

Development of 2-Methoxyhuprine as Novel Lead for Alzheimer's Disease Therapy.

Tacrine (THA), the first clinically effective acetylcholinesterase (AChE) inhibitor and the first approved drug for the treatment of Alzheimer's disease (AD), was withdrawn from the market due to its side effects, particularly its hepatotoxicity. Nowadays, THA serves as a valuable scaffold for the design of novel agents potentially applicable for AD treatment. One such compound, namely 7-methoxytacrine (7-MEOTA), exhibits an intriguing profile, having suppressed hepatotoxicity and concomitantly retaining AChE inhibition properties. Another interesting class of AChE inhibitors represents Huprines, designed by merging two fragments of the known AChE inhibitors-THA and (-)-huperzine A. Several members of this compound family are more potent human AChE inhibitors than the parent compounds. The most promising are so-called huprines X and Y. Here, we report the design, synthesis, biological evaluation, and in silico studies of 2-methoxyhuprine that amalgamates structural features of 7-MEOTA and huprine Y in one molecule.

The Evaluation of the Reactivating and Neuroprotective Efficacy of Two Newly Prepared Bispyridinium Oximes (K305, K307) in Tabun-Poisoned Rats-A Comparison with Trimedoxime and the Oxime K203.

The ability of two newly developed oximes (K305, K307) to protect tabun-poisoned rats from tabun-induced inhibition of brain acetylcholinesterase, acute neurotoxic signs and symptoms and brain damage was compared with that of the oxime K203 and trimedoxime. The reactivating and neuroprotective effects of the oximes studied combined with atropine on rats poisoned with tabun at a sublethal dose were evaluated. The reactivating efficacy of a newly developed oxime K305 is lower compared to the reactivating efficacy of the oxime K203 and trimedoxime while the ability of the oxime K307 to reactivate tabun-inhibited acetylcholinesterase (AChE) in the brain roughly corresponds to the reactivating efficacy of the oxime K203 and it is slightly lower compared to trimedoxime. In addition, only one newly developed oxime (K307) combined with atropine was able to markedly decrease tabun-induced neurotoxicity although it did not eliminate all tabun-induced acute neurotoxic signs and symptoms. These results correspond to the histopathological evaluation of tabun-induced brain damage. Therefore, the newly developed oximes are not suitable for the replacement of commonly used oximes (especially trimedoxime) in the treatment of acute tabun poisonings.

Activity of cholinesterases in a young and healthy middle-European population: Relevance for toxicology, pharmacology and clinical praxis.

The activity of human cholinesterases, erythrocyte acetylcholinesterase (AChE; EC 3.1.1.7) and plasma butyrylcholinesterase (BChE; EC 3.1.1.8) represents an important marker when monitoring exposure to pesticides/nerve agents, and may also be used in occupational medicine in diagnosis and prognosis of some diseases. In this study "normal/baseline" AChE and BChE activity has been investigated in a young and healthy population, with subsequent evaluation of several intra-population factors including sex, age (categories 18-25, 26-35 and 36-45 years old) and smoker status. The modified Ellman's method was used for enzyme activity assessment in 387 young and healthy individuals (201 males and 186 females aged 18-45). A significant inter-sexual difference in AChE and BChE activity was found (AChE: 351±67 for males and 377±65 for females, (µmol/min)/(µmol of hemoglobin), p<0.001; BChE: 140±33 for males and 109±29 for females, µkat/l, p<0.001; mean±SD). Despite the finding that mean AChE activity somewhat decreased whereas BChE activity grew within the age categories of the tested subjects, no significant effect of age on cholinesterase activity was found (p>0.05). Smoking influenced cholinesterase activity - AChE activity in smokers was elevated (approx. 3% in males; 8% in females) relative to that in non-smokers (p<0.05). Smoking was found not to have any effect on BChE activity. Reference values based on confidence intervals for AChE and BChE activity were established. The presented results might be useful in routine clinical practice where the monitoring of blood AChE and plasma BChE activity is crucial for prognosis and diagnosis of organophosphate poisoning, in occupational medicine and in relevant mass casualty scenarios.

A comparison of neuroprotective efficacy of two novel reactivators of acetylcholinesterase called K920 and K923 with the oxime K203 and trimedoxime in tabun-poisoned rats.

The ability of two newly developed bispyridinium oximes (K920, K923) to reduce tabun-induced acute neurotoxic signs and symptoms was compared with the oxime K203 and trimedoxime using a functional observational battery (FOB). The neuroprotective effects of the oximes studied combined with atropine on rats poisoned with tabun at a sublethal dose (130 µg/kg i.m.; 80% of LD50 value) were evaluated. Tabun-induced neurotoxicity was monitored by FOB at 2 h after tabun administration. The results indicate that all tested oximes combined with atropine enable tabun-poisoned rats to survive till the end of experiment while one non-treated tabun-poisoned rat died within 2 h. Both newly developed oximes (K920, K923) combined with atropine were able to markedly decrease tabun-induced neurotoxicity in the case of sublethal poisoning although they did not eliminate all tabun-induced acute neurotoxic signs and symptoms. Their ability to decrease tabun-induced acute neurotoxicity did not prevail the neuroprotective efficacy of trimedoxime and the oxime K203. Therefore, the newly developed oximes are not suitable for the replacement of currently available oximes (especially trimedoxime) in the treatment of acute tabun poisonings.

Concentration of Donepezil in the Cerebrospinal Fluid of AD Patients: Evaluation of Dosage Sufficiency in Standard Treatment Strategy.

Although some studies have described the pharmacokinetics and pharmacodynamics of donepezil in the peripheral compartment, studies focused on drug transport across the blood-brain barrier are still very rare. To our knowledge, the fluctuation in the cerebrospinal fluid concentration of donepezil after administration of the drug has not been described in the literature so far. We recruited 16 patients regularly taking a standard therapeutic dose of donepezil (10 mg per day). All patients (Caucasian race) were treated for at least three months with a stable dose of 10 mg per day prior to sample collection. Patients were divided into two groups depending on the time of plasma and cerebrospinal fluid sampling: 12 h (n = 9; 4 M/5F aged 78.68 ± 7.35 years) and 24 h (n = 7; 3 M/4F aged 77.14 ± 5.87 years) after donepezil administration. The cerebrospinal fluid sample was collected by standard lumbar puncture technique using a single-use traumatic needle. The samples were analysed on an Agilent 1260 Series liquid chromatograph comprising a degasser, a quaternary pump, a light-tight autosampler unit set, a thermostated column compartment, and a UV/VIS detector. Agilent ChemStation software, the statistical software Prism4, version 5.0 (GraphPad Software, USA), and IBM® SPSS® Statistics were used for the analysis of the results. The difference in plasma concentration of donepezil after 12 h (mean ± SEM; 39.99 ± 5.90 ng/ml) and after 24 h (29.38 ± 1.71 ng/ml) was nonsignificant. In contrast, the donepezil concentration in the cerebrospinal fluid was significantly higher in the 24-h interval (7.54 ± 0.55 ng/ml) compared with the 12-h interval (5.19 ± 0.83 ng/ml, which is ~70 % based on mean cerebrospinal fluid values). Based on these data, it is plausible to predict that donepezil might produce a stronger AChE inhibition in the brain at 24 h compared with 12 h following the administration. This information may help physicians individually adjust the time of drug administration in the patients according to time course of the disease symptoms.

Effects of novel tacrine-related cholinesterase inhibitors in the reversal of 3-quinuclidinyl benzilate-induced cognitive deficit in rats--Is there a potential for Alzheimer's disease treatment?

Inhibitors of cholinesterase are important drugs for therapy of Alzheimer's disease and the search for new modifications is extensive, including dual inhibitors or multi-target hybrid compounds. The aim of the present study was a preliminary evaluation of pro-cognitive effects of newly-developed 7-MEOTA-donepezil like hybrids (compounds no. 1 and 2) and N-alkylated tacrine derivatives (compounds no. 3 and 4) using an animal model of pharmacologically-induced cognitive deficit. Male Wistar rats were subjected to tests of learning and memory in a water maze and step-through passive avoidance task. Cognitive impairment was induced by 3-quinuclidinyl benzilate (QNB, 2mgkg(-1)), administered intraperitoneally 1h before training sessions. Cholinesterase inhibitors were administered as a single therapeutic dose following the QNB at 30min at the following dose rates; 1 (25.6mgkg(-1)), 2 (12.3mgkg(-1)), 3 (5.7mgkg(-1)), 4 (5.2mgkg(-1)). The decrease in total path within the 10-swim session (water maze), the preference for target quadrant (water maze) and the entrance latency (passive avoidance) were taken as indicators of learning ability in rats. The effects of novel compounds were compared to that of standards tacrine (5.2mgkg(-1)) and donepezil (2.65mgkg(-1)). QNB significantly impaired spatial navigation as well as fear learning. Generally, the performance of rats was improved when treated with novel inhibitors and this effect reached efficiency of standard donepezil at selected doses. There was a significant improvement in the groups treated with compounds 2 and 3 in all behavioral tasks. The rest of the novel compounds succeed in the passive avoidance test. In summary, the potential of novel inhibitors (especially compounds 2 and 3) was proved and further detailed evaluation of these compounds as potential drugs for Alzheimer's disease treatment is proposed.

The effects of novel 7-MEOTA-donepezil like hybrids and N-alkylated tacrine analogues in the treatment of quinuclidinyl benzilate-induced behavioural deficits in rats performing the multiple T-maze test.

AIMS: The number of approved drugs for the clinical treatment of Alzheimer disease remains limited. For this reason, there is extensive search for novel therapies. Of these, cholinesterase inhibitors have some proven benefit in slowing the disease progression and still remain the first-line therapeutic approach. In this study, the pro-cognitive effect of four novel tacrine-related inhibitors was evaluated and compared with the standards, tacrine and donepezil. METHODS: Wistar rats trained to perform the multiple T-maze were treated intra-peritoneally with the anticholinergic agent 3-quinuclidinyl benzilate (QNB, 2.0 mg/kg), followed 30 min later by another injection containing a therapeutic dose of standard or novel cholinesterase inhibitor. The rats were repeatedly subjected to the multiple T-maze task at several time points following QNB administration (1, 24, 48 and 72 h). The passage time and number of errors were recorded. The inhibitory potential of selected therapeutic doses was assessed in a separate in vivo experiment using a spectrophotometric method. RESULTS: QNB significantly impaired the performance of the rats within 48 h. The four novel cholinesterase inhibitors attenuated the effect of QNB at 1 h, 24 h and 48 h test intervals. The novel compounds resulted in brain cholinesterase inhibition ranging from 5.4 to 11.3 %, and their effect on the QNB-induced deficit recorded in the T-maze performance was comparable to that of the standards or higher at some time points. CONCLUSION: The best result was achieved with derivative 4, followed by derivatives 2 and 3, suggesting that these compounds could be candidates for the treatment of Alzheimer disease.

Self-expandable biodegradable biliary stents in porcine model.

BACKGROUND: Treatment or prevention of a benign biliary tree stricture is an unresolved problem. A novel self-expandable biodegradable polydioxanon biliary stent in a porcine model was studied. MATERIALS AND METHODS: This new stent was used in 23 pigs. Feasibility and safety of surgical stenting, time of biodegradation, and histologic reaction in 2, 8, 13, and 20 wk of a follow-up were studied. All stents were inserted into a common bile duct through a duodenal papilla following small dilatation. After surgical evaluation of abdominal cavities, the pigs were sacrificed to remove common bile ducts with the stents. All bile ducts were assessed by macroscopic and histopathologic examination. RESULTS: Self-expansion was correct in all cases. Neither bile duct obstruction nor postsurgical complications were observed. Macroscopic evaluation indicated lightening of the stent color in 2 wk, a partial disintegration in 8 wk, and a complete absorption in 13 and 20 wk. Histologic evaluation in general substantiated a mild-to-moderate inflammatory reaction in the lamina propria during the whole follow up and had no clinical consequences. No cholangitis, necrosis, abscess, or excessive fibroplasia was found in a hepatoduodenal ligament. CONCLUSIONS: Our results suggest that polydioxanon biodegradable self-expanding stents seem to be useful for biliary system implantation, offer a good biocompatibility, and completely degrade within 13 wk.

Translation of in vitro to in vivo pyridinium oxime potential in tabun poisoning.

Even if organophosphorus (OP) nerve agents were banned entirely, their presence would remain a problem as weapons of terror (like in Syria). Oxime antidotes currently used in medical practice still fall short of their therapeutic purpose, as they fail to fully restore the activity of cholinesterases, the main target for OPs. As orphan drugs, these antidotes are tested too seldom for anybody's benefit. Over the last few decades, search for improved reactivators has reached new levels, but the translation of data obtained in vitro to in vivo application is still a problem that hinders efficient therapy. In this study, we tested the strengths and weaknesses of extrapolating pyridinium oxime antidotes reactivation efficiency from in vitro to in vivo application. Our results show that this extrapolation is possible with well-determined kinetic constants, but that it also largely depends on oxime circulation time and its tissue-specific distribution. This suggests that pharmacokinetic studies should be planned at the early stages of antidote development. Special attention should also be given to improving oxime distribution throughout the organism to overcome this major constraint in improving overall OP therapy.

Acute toxicity of some nerve agents and pesticides in rats.

OBJECTIVES: Highly toxic organophosphorus compounds (V- and G-nerve agents) were originally synthesized for warfare or as agricultural pesticides. Data on their acute toxicity are rare and patchy. Therefore, there is a need for integrated summary comparing acute toxicity of organophosphates using different administration routes in the same animal model with the same methodology. Based on original data, a summary of in vivo acute toxicity of selected V- and G-nerve agents (tabun, sarin, soman, VX, Russian VX) and organophosphates paraoxon (POX) and diisopropyl fluorophosphate (DFP) in rats has been investigated. MATERIALS AND METHODS: Male Wistar rats were exposed to organophosphates in several administration routes (i.m., i.p., p.o, s.c., p.c.). The acute toxicity was evaluated by the assessment of median lethal dose (LD50, mg kg(-1)) 2, 4, and 24 hours post exposure. RESULTS: V-agents were the most toxic presented with LD50 ranged from 0.0082 mg kg(-1) (VX, i.m.) to 1.402 mg kg(-1) (Russian VX, p.o.), followed by G-agents (LD50 = 0.069 mg kg(-1)/soman, i.m./ - 117.9 mg kg(-1)/sarin, p.c./), organophosphate POX and DFP (LD50 = 0.321 mg kg(-1)/POX, i.m./ - 420 mg kg(-1)/DFP, p.c./). Generally, i.m. administration was the most toxic throughout all tested agents and ways of administration (LD50 = 0.0082 mg kg(-1)/VX/ - 1.399 mg kg(-1)/DFP/) whereas p.c. way was responsible for lowest acute toxicity (LD50 = 0.085 mg kg(-1)/VX/ - 420 mg kg(-1)/DFP/). CONCLUSION: The acute toxicity of selected organophosphorus compounds is summarized throughout this study. Although the data assessed in rats are rather illustrative prediction for human, it presents a valuable contribution, indicating the toxic potential and harmfulness of organophosphates.

Cholinergic antagonist 3-quinuclidinyl benzilate - Impact on learning and memory in Wistar rats.

3-Quinuclidinyl benzilate (QNB) represents a non-selective, competitive antagonist of cholinergic receptors, which has been previously used to generate cognitive deficits in animal models of neurodegenerative disorders. The aim of this study was evaluation of QNB potency for creation of cognitive impairment during the acquisition, consolidation and retrieval stages of learning and memory in rats. Male Wistar rats were subjected to a water maze task with hidden platform and a step-through passive avoidance task. The water maze test was carried out in two separate experiments focused on spatial learning (acquisition test) and long-term spatial memory (retrieval test). QNB doses (0.5, 1.0, 2.0 and 5.0 mg kg(-1)) were administered to rats intraperitoneally before training sessions (acquisition test) or before probe trial (retrieval test). A QNB dose of 2.0 mg kg(-1) was administered to rats in the passive avoidance task before training (acquisition test), immediately post-training (consolidation test) or 24h pre-retention (retrieval test). QNB significantly impaired the acquisition in the water maze at doses 0.5-5.0 mg kg(-1) as well as the acquisition of passive avoidance task. In contrast, consolidation and retrieval were not affected by QNB, indicating that QNB specifically affects the stage of acquisition.