Medetomidine/midazolam/fentanyl narcosis alters cardiac autonomic tone leading to conduction disorders and arrhythmias in mice.

Arrhythmias are critical contributors to cardiovascular morbidity and mortality. Therapies are mainly symptomatic and often insufficient, emphasizing the need for basic research to unveil the mechanisms underlying arrhythmias and to enable better and ideally causal therapies. In translational approaches, mice are commonly used to study arrhythmia mechanisms in vivo. Experimental electrophysiology studies in mice are performed under anesthesia with medetomidine/midazolam/fentanyl (MMF) and isoflurane/fentanyl (IF) as commonly used regimens. Despite evidence of adverse effects of individual components on cardiac function, few data are available regarding the specific effects of these regimens on cardiac electrophysiology in mice. Here we present a study investigating the effects of MMF and IF narcosis on cardiac electrophysiology in vivo in C57BL/6N wild-type mice. Telemetry transmitters were implanted in a group of mice, which served as controls for baseline parameters without narcosis. In two other groups of mice, electrocardiogram and invasive electrophysiology studies were performed under narcosis (with either MMF or IF). Basic electrocardiogram parameters, heart rate variability parameters, sinus node and atrioventricular node function, and susceptibility to arrhythmias were assessed. Experimental data suggest a remarkable influence of MMF on cardiac electrophysiology compared with IF and awake animals. While IF only moderately reduced heart rate, MMF led to significant bradycardia, spontaneous arrhythmias, heart rate variability alterations as well as sinus and AV node dysfunction, and increased inducibility of ventricular arrhythmias. On the basis of these observed effects, we suggest avoiding MMF in mice, specifically when studying cardiac electrophysiology, but also whenever a regular heartbeat is required for reliable results, such as in heart failure or imaging research.

Segmental Hair Testing of Triazolam to Unmask a Suspected Case of Idiopathic Recurrent Stupor.

ABSTRACT: Stupor is a diagnostic challenge at emergency department. Differential diagnosis includes idiopathic recurrent stupor, formerly attributed to "endozepine-4" accumulation. This condition has been recently questioned because many suspected cases resulted in exogenous benzodiazepine intake that eludes the conventional toxicological assay. In case of unexplained recurrent stupor, to extend the benzodiazepine search in nonconventional matrices can allow unmasking of hidden toxic behavior.

Quantitative Structure-Activity Relationships of Aquatic Narcosis: A Review.

BACKGROUND: Prior estimation of toxicity of each and every, existing and yet to be synthesized chemicals is a must to elude their adverse effect on the environment. Experimental determination of such parameters is time consuming, cost effective and above all, it demands the sacrifice of many vertebrates. At this end, the REACH regulations advocate for the use of non-testing predictive methods such as read-across, weight-of-evidence and QSAR (quantitative structure-activity relationship) techniques. Among these methods, QSAR is found to be the best as it is based on molecular structure only. The descriptors used in deriving the model in QSAR vary according to the nature of the narcotics as well as the species used for. The success of a model in predicting the toxicity of a narcotic purely depends on the type of descriptors selected that explains the structural features closely related to the property under study. In this review, we have focused on the different types of descriptors and QSAR models used to explain the narcosis phenomenon. METHODS: Literature was scanned for acute toxicity of chemicals on species like tadpoles, protozoa, planktonic crustaceans, and small fishes like million fish, rainbow fish etc. from different sources. The toxicity and toxicants were classified considering their polarity and specific interactions of the compounds. Due to complex nature of the substrate, the mechanism of action of toxicant is uncertain. However, the overall results obtained from the biological study have been subjected to QSAR studies to obtain various models, which can provide some ideas on the mode of toxicological action. Different types of molecular descriptors derived both experimentally and theoretically have been used in the QSAR studies. RESULTS: Mostly biochemicals have a specific signature on oil/water partition (Ko/w, P), which is the crux in biological activity. Accordingly, the toxicological activities have good correlations with log P. Addition of some more structural descriptors improves the structure-toxicity relationship. Among these, electronic descriptors like EHOMO, ELUMO and ΔE derived from molecular orbitals have been used in the QSAR. ELUMO describing the energy of excited species of the molecule is found to be the most suitable one. Other molecular descriptors used in the QSAR include constitutional, topological and Abraham's solute descriptors. The models derived from the QSAR studies were found to be highly significant to predict the toxicology as well as to throw light on the mechanism. CONCLUSION: The best descriptor for aquatic narcosis is the KO/W or P. Addition of an electronic parameter (ELUMO) improves the QSAR to some extent. However, substitution of ELUMO by other class of molecular descriptors has also some statistical significance. To have a global QSAR model, in addition to P, some more appropriate descriptors are to be derived either experimentally or theoretically, latter being the more cost effective and easy in derivation.

Individual roles of brain and serum alcohol dehydrogenase isoforms in regulation of alcohol consumption in SPF Wistar rats.

Alcohol dehydrogenases (ADH) are key enzymes of ethanol metabolism that mediate its oxidation to acetaldehyde. ADHs are also able to oxidize some types of neurotransmitters such as dopamine, serotonin and norepinephrine. Increased level of ADHs activity, induced by chronic alcohol consumption, is presumably associated with disturbed neurotransmitters metabolism that leads to stable alcohol craving. As earlier reported, intraperitoneal administration of 4-methilpirasole (non-specific inhibitor of ADHs) has shown to provide a short-term anti-alcoholic effect, but individual roles of ADH isoforms in this process were still unclear. The aim of this work was to study the roles of brain and serum ADH isoforms in alcohol consumption and neurotransmitter metabolism in the rats. In the study we used specific-pathogen-free (SPF) Wistar rats chronically alcoholized with 15% ethanol. 4-methilpirasole intranasal administration in small doses led to local inhibition of ADH III activity in the brain estimated by spectrophotometric assay. It correlated with dose-dependent reduction of dopamine concentration and increased level of its metabolic products in the brain but did not influence alcohol consumption. These data allowed us to propose an important role of brain ADHs (predominantly ADH III) in metabolism of dopamine in chronically alcoholized rats but not in regulation of alcohol consumption. To evaluate the role of serum ADH isoforms we immunized the rats with recombinant horse ADH that led to production of high levels of cross-reactive anti-ADH antibodies verified by ELISA assay. Immunization led to 30% decrease in alcohol consumption and recovery of general behavioral parameters such as motor activity, anxiety and depression level. At the same time active immunization did not cause any impairments in animal blood composition. We can conclude that immunization against ADHs appeared to be a safe way to decrease alcohol consumption that could be possibly associated with neurotransmitters metabolism correction.

Evaluation of the phototoxicity of unsubstituted and alkylated polycyclic aromatic hydrocarbons to mysid shrimp (Americamysis bahia): Validation of predictive models.

Crude oils are composed of an assortment of hydrocarbons, some of which are polycyclic aromatic hydrocarbons (PAHs). Polycyclic aromatic hydrocarbons are of particular interest due to their narcotic and potential phototoxic effects. Several studies have examined the phototoxicity of individual PAHs and fresh and weathered crude oils, and several models have been developed to predict PAH toxicity. Fingerprint analyses of oils have shown that PAHs in crude oils are predominantly alkylated. However, current models for estimating PAH phototoxicity assume toxic equivalence between unsubstituted (i.e., parent) and alkyl-substituted compounds. This approach may be incorrect if substantial differences in toxic potency exist between unsubstituted and substituted PAHs. The objective of the present study was to examine the narcotic and photo-enhanced toxicity of commercially available unsubstituted and alkylated PAHs to mysid shrimp (Americamysis bahia). Data were used to validate predictive models of phototoxicity based on the highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap approach and to develop relative effect potencies. Results demonstrated that photo-enhanced toxicity increased with increasing methylation and that phototoxic PAH potencies vary significantly among unsubstituted compounds. Overall, predictive models based on the HOMO-LUMO gap were relatively accurate in predicting phototoxicity for unsubstituted PAHs but are limited to qualitative assessments. Environ Toxicol Chem 2017;36:2043-2049. © 2017 SETAC.

Acute mental change and hemiplegia after autologous fat injection.

Autologous fat injection is a common procedure used for skin augmentation. It is known to be safe and simple, but severe complications have been reported at times. The authors observed a patient with acute large cerebral infarction including the territories of the anterior and middle cerebral arteries and optic nerve infarction developing after autologous fat transplantation. A 32-year-old woman was referred to the emergency room of our hospital due to sudden stupor. Thirty minutes earlier, she was undergoing cosmetic autologous fat injection into the glabella area by a plastic surgeon at a private clinic. The cause was confirmed to be anterior and middle cerebral arteries infarction on brain imaging studies. When a patient presents abrupt mental change, hemiplegia, ocular pain, or blindness after autologous fat particle injection, physicians must consider cerebral infarction and combined retinal artery occlusion.

Re-analysis of narcotic critical body residue data using the equilibrium distribution concept and refined partition coefficients.

Narcosis occurs as a result of the accumulation of chemicals in the phospholipid membrane. The toxic threshold concentration in the membrane is thought to be relatively constant across different chemicals and species. Hence, estimating chemical concentrations in the membrane is expected to reduce the variability of narcotic critical body residue (CBR) data. In this study, a high quality CBR dataset for three aquatic species reported recently in the literature was evaluated with the internal equilibrium distribution concept. The raw wet-weight-based CBR values were converted to membrane-weight-based CBR values by assuming that the chemical is distributed in storage lipids, membranes, proteins, and water according to the respective equilibrium partition coefficients. Several sets of partition coefficients were compared for this analysis. The results were consistent with the notion that the use of a structural protein instead of serum albumin as a surrogate for the body protein fraction could reduce the variability of CBRs. Partition coefficients predicted by polyparameter linear free energy relationships (PP-LFERs) reduced the variability of CBRs as much as or even more than experimental partition coefficients did. It is suggested that CBR data for chemicals with larger structural diversity and biological species with more distinct compositions are needed to evaluate further the equilibrium distribution concept and the constant membrane threshold hypothesis.

Role of phosphodiesterase-4 on ethanol elicited locomotion and narcosis.

The cAMP signaling pathway has emerged as an important modulator of the pharmacological effects of ethanol. In this respect, the cAMP-dependent protein kinase has been shown to play an important role in the modulation of several ethanol-induced behavioral actions. Cellular levels of cAMP are maintained by the activity of adenylyl cyclases and phosphodiesterases. In the present work we have focused on ascertaining the role of PDE4 in mediating the neurobehavioral effects of ethanol. For this purpose, we have used the selective PDE4 inhibitor Ro 20-1724. This compound has been proven to enhance cellular cAMP response by PDE4 blockade and can be administered systemically. Swiss mice were injected intraperitoneally (i.p.) with Ro 20-1724 (0-5 mg/kg; i.p.) at different time intervals before ethanol (0-4 g/kg; i.p.) administration. Immediately after the ethanol injection, locomotor activity, loss of righting reflex, PKA footprint and enzymatic activity were assessed. Pretreatment with Ro 20-1724 increased ethanol-induced locomotor stimulation in a dose-dependent manner. Doses that increased locomotor stimulation did not modify basal locomotion or the suppression of motor activity produced by high doses of this alcohol. Ro 20-1724 did not alter the locomotor activation produced by amphetamine or cocaine. The time of loss of righting reflex evoked by ethanol was increased after pretreatment with Ro 20-1724. This effect was selective for the narcotic effects of ethanol since Ro 20-1724 did not affect pentobarbital-induced narcotic effects. Moreover, Ro 20-1724 administration increased the PKA footprint and enzymatic activity response elicited by ethanol. These data provide further evidence of the key role of the cAMP signaling pathway in the central effects of ethanol.

Elemental mercury mixed with alcohol injected intravenously as a suicide attempt.

A 22-year-old woman was admitted to the emergency department with symptoms of chest discomfort after a suicide attempt by injecting intravenously the amount of mercury extracted from 3 thermometers mixed with alcohol. At presentation, the patient was well oriented with normal vital signs, but a few hours later she presented an abrupt deterioration of her mental status, with confusion, disorientation, tremor and finally stupor. She was transferred to the intensive care unit for monitoring and therapy. A nasogastric tube was immediately placed and the patient received treatment with a chelating agent dimercaptosuccinic acid (DMSA)/succimer 800 mg orally three times a day, a dosage decided on the basis of her body weight, plus phenytoin 125 mg intravenously three times a day. Two hours after treatment initiation, the patient reported a remarkable improvement of her symptoms. However, she experienced seizures during a 6-month period after her discharge.

Acute and long-term biological effects of mechanically and chemically dispersed oil on lumpsucker (Cyclopterus lumpus).

Concentration dependent differences in acute and long-term effects of a 48 h exposure to mechanically or chemically dispersed crude oil were assessed on juvenile lumpsucker (Cyclopterus lumpus). Acute or post-exposure mortality was only observed at oil concentrations representing higher concentrations than reported after real oil spills. Acute mortality was more apparent in chemically than mechanically dispersed oil treatments whereas comparable EC50s were observed for narcosis. There was a positive correlation between EROD activity and muscle PAH concentration for the lower oil concentrations whereas higher concentrations inhibited the enzyme activity. The incidence of gill tissue lesions was low with no difference between dispersion methods or oil concentrations. A concentration dependent decrease in swimming- and feeding behavior and in SGR was observed at the start of the post-exposure period, but with no differences between corresponding oil treatments. Three weeks post-exposure, fish from all treatments showed as high SGR as the control fish.

QSARs for aquatic toxicity: celebrating, extending and displaying the pioneering contributions of Ferguson, Konemann and Veith.

Significant advances were made in the development of quantitative structure-activity relationships (QSARs) relating molecular structure to aquatic toxicity by three studies over 30 years ago by Ferguson in 1939, Konemann in 1981, and Veith and colleagues in 1983. We revisit the original concepts and data from these studies and review these contributions from the bases of current perspectives on the hypothesized mechanism of baseline narcotic toxicity and the underlying thermodynamic and kinetic aspects. The relationships between LC50, octanol-water partition coefficient, aqueous solubility, chemical activity and chemical volume fraction in lipid phases are outlined including kinetic influences on measured toxicities. These relationships provide a compelling and plausible explanation of the success of these and other QSARs for aquatic toxicity. Suggestions are made for further advances in these QSARs to improve assessments of toxicity by baseline narcotic toxicity and selective modes of action, especially using emerging quantum chemical computational capabilities.

Stage-dependent toxicity of bisphenol a on Rhinella arenarum (anura, bufonidae) embryos and larvae.

The acute and chronic toxicity of bisphenol A (BPA) was evaluated on the common South American toad Rhinella arenarum embryos and larvae by means of continuous and pulse exposure treatments. Embryos were treated continuously from early blastula (S.4) up to complete operculum (S.25), during early larval stages and by means of 24 h pulse exposures of BPA in concentrations ranging between 1.25 and 40 mg L(-1) , in order to evaluate the susceptibility to this compound in different developmental stages. For lethal effects, S.25 was the most sensitive and gastrula was the most resistant to BPA. The Teratogenic Index for neurula, the most sensitive embryonic stage for sublethal effects was 4.7. The main morphological alterations during early stages were: delayed or arrested development, reduced body size, persistent yolk plug, microcephaly, axial/tail flexures, edemas, blisters, waving fin, underdeveloped gills, mouth malformations, and cellular dissociation. BPA caused a remarkable narcotic effect from gill circulation stage (S.20) onwards in all the organisms exposed after 3 h of treatment with 10 mg L(-1) BPA. After recovering, the embryos exhibited scarce response to stimuli, erratic or circular swimming, and spasmodic contractions from 5 mg L(-1) onwards. Our results highlight the lethal and sublethal effectsof BPA on R. arenarum embryos and larvae, in the last case both at structural and functional levels.