Mephedrone pharmacokinetics after intravenous and oral administration in rats: relation to pharmacodynamics

Fe d'errates disponible a: http://​dx.​doi.​org/​10.​1007/​s00213-013-3283-6Rationale Mephedrone (4-methylmethcathinone) is a still poorly known drug of abuse, alternative to ecstasy or cocaine. Objective The major aims were to investigate the pharmacokineticsa and locomotor activity of mephedrone in rats and provide a pharmacokinetic/pharmacodynamic model. Methods Mephedrone was administered to male Sprague-Dawley rats intravenously (10 mg/kg) and orally (30 and 60 mg/kg). Plasma concentrations and metabolites were characterized using LC/MS and LC-MS/MS fragmentation patterns. Locomotor activity was monitored for 180-240 min. Results Mephedrone plasma concentrations after i.v. administration fit a two-compartment model (α=10.23 h−1, β=1.86 h−1). After oral administration, peak mephedrone concentrations were achieved between 0.5 and 1 h and declined to undetectable levels at 9 h. The absolute bioavailability of mephedrone was about 10 % and the percentage of mephedrone protein binding was 21.59±3.67%. We have identified five phase I metabolites in rat blood after oral administration. The relationship between brain levels and free plasma concentration was 1.85±0.08. Mephedrone induced a dose-dependent increase in locomotor activity, which lasted up to 2 h. The pharmacokinetic-pharmacodynamic model successfully describes the relationship between mephedrone plasma concentrations and its psychostimulant effect. Conclusions We suggest a very important first-pass effect for mephedrone after oral administration and an easy access to the central nervous system. The model described might be useful in the estimation and prediction of the onset, magnitude,and time course of mephedrone pharmacodynamics as well as to design new animal models of mephedrone addiction and toxicity

Fluorescent Transgenic Zebrafish Tg(nkx2.2a:mEGFP) Provides a Highly Sensitive Monitoring Tool for Neurotoxins

10.1371/journal.pone.0055474PLoS ONE82

Atomic Resolution Cryo-EM Structure Of A Nativelike CENP-A Nucleosome Aided By An Antibody Fragment

Genomic DNA in eukaryotes is organized into chromatin through association with core histones to form nucleosomes, each distinguished by their DNA sequences and histone variants. Here, we used a single-chain antibody fragment (scFv) derived from the anti-nucleosome antibody mAb PL2-6 to stabilize human CENP-A nucleosome containing a native α-satellite DNA and solved its structure by the cryo-electron microscopy (cryo-EM) to 2.6 Å resolution. In comparison, the corresponding cryo-EM structure of the free CENP-A nucleosome could only reach 3.4 Å resolution. We find that scFv binds to a conserved acidic patch on the histone H2A-H2B dimer without perturbing the nucleosome structure. Our results provide an atomic resolution cryo-EM structure of a nucleosome and insight into the structure and function of the CENP-A nucleosome. The scFv approach is applicable to the structural determination of other native-like nucleosomes with distinct DNA sequences

Nucleosome–Chd1 structure and implications for chromatin remodelling

Chromatin-remodelling factors change nucleosome positioning and facilitate DNA transcription, replication, and repair. The conserved remodelling factor chromodomain-helicase-DNA binding protein 1(Chd1) can shift nucleosomes and induce regular nucleosome spacing. Chd1 is required for the passage of RNA polymerase IIthrough nucleosomes and for cellular pluripotency. Chd1 contains the DNA-binding domains SANT and SLIDE, a bilobal motor domain that hydrolyses ATP, and a regulatory double chromodomain. Here we report the cryo-electron microscopy structure of Chd1 from the yeast Saccharomyces cerevisiae bound to a nucleosome at a resolution of 4.8 Å. Chd1 detaches two turns of DNA from the histone octamer and binds between the two DNA gyres in a state poised for catalysis. The SANT and SLIDE domains contact detached DNA around superhelical location (SHL) -7 of the first DNA gyre. The ATPase motor binds the second DNA gyre at SHL +2 and is anchored to the N-terminal tail of histone H4, as seen in a recent nucleosome-Snf2 ATPase structure. Comparisons with published results reveal that the double chromodomain swings towards nucleosomal DNA at SHL +1, resulting in ATPase closure. The ATPase can then promote translocation of DNA towards the nucleosome dyad, thereby loosening the first DNA gyre and remodelling the nucleosome. Translocation may involve ratcheting of the two lobes of the ATPase, which is trapped in a pre- or post-translocation state in the absence or presence, respectively, of transition state-mimicking compounds

Nitrogen Deposition Reduces Plant Diversity and Alters Ecosystem Functioning: Field-Scale Evidence from a Nationwide Survey of UK Heathlands

Findings from nitrogen (N) manipulation studies have provided strong evidence of the detrimental impacts of elevated N deposition on the structure and functioning of heathland ecosystems. Few studies, however, have sought to establish whether experimentally observed responses are also apparent under natural, field conditions. This paper presents the findings of a nationwide field-scale evaluation of British heathlands, across broad geographical, climatic and pollution gradients. Fifty two heathlands were selected across an N deposition gradient of 5.9 to 32.4 kg ha−1 yr−1. The diversity and abundance of higher and lower plants and a suite of biogeochemical measures were evaluated in relation to climate and N deposition indices. Plant species richness declined with increasing temperature and N deposition, and the abundance of nitrophilous species increased with increasing N. Relationships were broadly similar between upland and lowland sites, with the biggest reductions in species number associated with increasing N inputs at the low end of the deposition range. Both oxidised and reduced forms of N were associated with species declines, although reduced N appears to be a stronger driver of species loss at the functional group level. Plant and soil biochemical indices were related to temperature, rainfall and N deposition. Litter C:N ratios and enzyme (phenol-oxidase and phosphomonoesterase) activities had the strongest relationships with site N inputs and appear to represent reliable field indicators of N deposition. This study provides strong, field-scale evidence of links between N deposition - in both oxidised and reduced forms - and widespread changes in the composition, diversity and functioning of British heathlands. The similarity of relationships between upland and lowland environments, across broad spatial and climatic gradients, highlights the ubiquity of relationships with N, and suggests that N deposition is contributing to biodiversity loss and changes in ecosystem functioning across European heathlands

Volatile substance abuse: fatal overdose with dimethylether

With all of the recent publicity over novel psychoactive substances it is easy to forget that other easily available intoxicants can be found. Dimethyl ether (DME), also known as methylether, is an extremely flammable volatile organic compound with chemical structure CH3OCH3. This ether is a by-product of methanol production and is a colourless gas or liquid with ether like odour. Dimethyl ether has been used as a fuel, an aerosol propellant, a refrigerant and in ‘freeze’ sprays. Dimethyl ether is an asphyxiant, but in liquid form it can act as a refrigerant. When inhaled, it is recognised to produce symptoms of euphoria, agitation, headache, and slurred speech (1,2). Very little is known about the acute or chronic effects of dimethyl ether in humans. The UK shortterm exposure limit is 500 ppm and the long-term exposure limit is 400 ppm (3). Recently the presence of the volatile substance dimethyl ether was identified in brain tissue of a 38 year old man with history of anxiety, depression and post-traumatic stress disorder. Due to the lipid solubility of dimethylether they can easily cross lipid membranes and distribute to well perfused organs such as the brain (4). The body was in a moderate state of decomposition surrounded with a number of aerosol cans (Muscle “ freeze” spray). Dimethyl ether was found in combination with ethanol in brain and other prescribed drugs (Gabapentin & Trazadone) in skeletal muscle. Due to the extensive putrefaction seen in the specimen, some if not all the ethanol detected could be a product of this process. Dimethyl ether, as a refrigerant and if sprayed into the mouth/throat, could stimulate the branch of the vagus nerve at the back of the throat. Stimulation of the vagus nerve causes the heart to slow. Over stimulation could cause the heart to stop. Myocardial ischemia caused by coronary vasospasm has also been hypothesised as a mechanism of death (4). As an asphyxiant its effects would include depression of the breathing and conscious levels. Taking into consideration of the history, circumstances surrounding the death and the toxicological findings, death was attributed to volatile substance abuse. The medical community should be aware of the availability of volatile abuse of Muscle “freeze” spray containing dimethyl within the U

Biomarkers for illicit heroin: a previously unrecognized origin of papaverine

No abstract available