Cephalopods are a group of marine invertebrates that have received little attention as sentinel species in comparison to other molluscs, such as bivalves. Consequently, their physiological and ...biochemical xenobiotic metabolism responses are poorly understood. Here we undertake a comparative analysis of the enzymatic activities involved in detoxification reactions and neural transmission in the digestive tract of two commercial cephalopods: the Common octopus, Octopus vulgaris, and the European cuttlefish, Sepia officinalis. For methodological purposes, several common B-esterases (five carboxylesterase (CE) substrates and three cholinesterase (ChE) determinations) were assayed as a proxy of metabolic and neuronal activities, respectively. Four components of the digestive tract in each species were considered: salivary glands, the stomach, the digestive gland and the caecum. The in vitro responses of digestive gland homogenates to model chemicals and contaminants of environmental concern were contrasted between both cephalopod species. The baseline biochemical activities in the four digestive tract components were also determined. Moreover, in order to validate the protocol, purified proteins, recombinant human CE (CE1 and CE2) and purified eel acetylcholinesterase (AChE) were included in the analysis. Overall, carboxylesterase activities were higher in octopus than in cuttlefish, with the activity quantified in the digestive tract components in the following order: digestive gland ≈ caecum > stomach ≈ salivary glands, with higher hydrolysis rates reached with naphthyl-derived substrates. In contrast, cuttlefish hydrolysis rates with ChE substrates were higher than in octopus. This trend was also reflected in a higher sensitivity to CE inhibitors in octopus and to AChE inhibitors in cuttlefish. Given the detoxification character of CEs and its protective role preventing AChE inhibition, octopus could be regarded as more efficiently protected than cuttlefish from neurotoxic exposures. A full characterisation of B-esterases in the digestive tract of the two common cephalopods is also provided.
•First time B-esterases characterisation in the digestive tract of two cephalopods.•Octopus carboxylesterase was sensitive to chemicals of environmental concern.•Cuttlefish acetylcholinesterase was sensitive to neurotoxic chemicals.•The flame retardant TBBPA interferes in vitro with carboxylesterases.•Cuttlefish AChE in vitro sensitive to organophosphorus flame retardants.
The loggerhead sea turtle (Caretta caretta) has been selected as sentinel species by the Marine Strategy Framework Directive (MSFD) descriptor 10 in relation to marine litter. In this, and other ...protected species, there is a need to develop conservative pollution biomarkers equally informative of chemical exposures to those traditionally carried out in metabolic organs, such as the liver. With this aim, plasma from turtles undergoing rehabilitation at the Fundació Oceanogràfic rescue centre (Arca del Mar) were selected and tested for B-esterase measurements. Hydrolysis rates of acetylcholinesterase (AChE), butyrylcholinesterase (BChE) and carboxylesterases (CEs) using four commercial substrates were undertaken on 191 plasma samples. Results indicated that acetylthiocholine was the most adequate substrate of cholinesterases and butyrate esters for CE measures. The correlation of these parameters with well-established blood biochemistry measurements was analysed. B-esterase measures in wild specimens were discussed in relation to age group, pathology on admission to the rescue centre and season; moreover, contrasts with long-term resident turtles were also made. Although this study provides baseline data on B-esterase measures in a large sample size for this species, more complementary information is still needed in terms of population genetics, chemical exposures, and in relation to other biochemical parameters before they can be confidently applied in wild specimens within the regulatory MSFD.
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•Plasmatic B-esterase hydrolysis rates are provided in loggerhead turtles.•Gas embolism does not modulate B-esterase responses.•Recovery centres can aid on the use of loggerheads as sentinels.•B-esterases are robust measures applicable to recently deceased individuals.
Sea turtles are frequently proposed as indicator species for assessing ocean health. To faciliate the use of these species as bioindicators requires the development of tools for rapidly and ...effectively assessing individual health. Here, we collected 104 blood samples from 69 loggerhead sea turtles, Caretta caretta, undergoing rehabilitation to determine the connection between health status, the activity of B-esterases, and other biochemical parameters. To determine the optimal assay protocol for B-esterases, we measured the activity and kinetics of cholinesterases-(ChEs) and carboxylesterases (CEs) using 3 and 5 commercial substrates, respectively, at different assay conditions. IC50 values for the activity of B-esterases were calculated within a concentration range for model pesticide inhibitors. Turtles’ health status was determined via routine veterinary procedures. During rehabilitation (which was associated with improving health status), we observed a decrease in the activity of most enzymes (especially in acetylcholinesterase) alongside an increase in CE when using p-nitrophenyl acetate as a substrate. As such, it is possible that the activity rates of plasmatic B-esterases could serve as an indicator of health status. There is also high potential that B-esterases could be specifically sensitive to marine pollutants although to further validate this would require future studies to specifically correlate B-esterarse activities to pollutant concentrations in blood or excreta.
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•Loggerhead turtles undergoing rehabilitation exhibited a decrease in plasmatic AChE activity.•Increases in pNPA-CE activity in loggerhead turtles may be linked to immune-system modulation.•Higher hydrolysis rates on plasmatic B-esterase measurements in marine turtles were seen at pH = 8.•Gas embolism significantly affected αNB-CE measurements in marine turtles.
Neuromuscular electrical stimulation (NMES) of the nervous system has been extensively used in neurorehabilitation due to its capacity to engage the muscle fibers, improving muscle tone, and the ...neural pathways, sending afferent volleys toward the brain. Although different neuroimaging tools suggested the capability of NMES to regulate the excitability of sensorimotor cortex and corticospinal circuits, how the intensity and dose of NMES can neuromodulate the brain oscillatory activity measured with electroencephalography (EEG) is still unknown to date. We quantified the effect of NMES parameters on brain oscillatory activity of 12 healthy participants who underwent stimulation of wrist extensors during rest. Three different NMES intensities were included, two below and one above the individual motor threshold, fixing the stimulation frequency to 35 Hz and the pulse width to 300 μs. Firstly, we efficiently removed stimulation artifacts from the EEG recordings. Secondly, we analyzed the effect of amplitude and dose on the sensorimotor oscillatory activity. On the one hand, we observed a significant NMES intensity-dependent modulation of brain activity, demonstrating the direct effect of afferent receptor recruitment. On the other hand, we described a significant NMES intensity-dependent dose-effect on sensorimotor activity modulation over time, with below-motor-threshold intensities causing cortical inhibition and above-motor-threshold intensities causing cortical facilitation. Our results highlight the relevance of intensity and dose of NMES, and show that these parameters can influence the recruitment of the sensorimotor pathways from the muscle to the brain, which should be carefully considered for the design of novel neuromodulation interventions based on NMES.
This paper presents a new approach for self-calibration BCI for reaching tasks using error-related potentials. The proposed method exploits task constraints to simultaneously calibrate the decoder ...and control the device, by using a robust likelihood function and an ad-hoc planner to cope with the large uncertainty resulting from the unknown task and decoder. The method has been evaluated in closed-loop online experiments with 8 users using a previously proposed BCI protocol for reaching tasks over a grid. The results show that it is possible to have a usable BCI control from the beginning of the experiment without any prior calibration. Furthermore, comparisons with simulations and previous results obtained using standard calibration hint that both the quality of recorded signals and the performance of the system were comparable to those obtained with a standard calibration approach.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Propylene carbonate can be used as an environmentally friendly, non-chlorinated solvent for asymmetric cyanohydrin synthesis catalyzed by a vanadiumoxo(salen) complex.
Propylene carbonate can be used ...as a green solvent for asymmetric cyanohydrin synthesis catalyzed by VO(salen)NCS. A range of 10 aromatic and aliphatic aldehydes gave high enantioselectivities (up to 93%) and conversions (up to 100%) in reactions carried out at or near room temperature with reaction times of 24
h or less.
The asymmetric addition of trimethylsilyl cyanide to aldehydes can be catalysed by Lewis acids and/or Lewis bases, which activate the aldehyde and trimethylsilyl cyanide, respectively. It is not ...always apparent from the structure of the catalyst whether Lewis acid or Lewis base catalysis predominates. To investigate this in the context of using salen complexes of titanium, vanadium and aluminium as catalysts, a Hammett analysis of asymmetric cyanohydrin synthesis was undertaken. When Lewis acid catalysis is dominant, a significantly positive reaction constant is observed, whereas reactions dominated by Lewis base catalysis give much smaller reaction constants. {Ti(salen)O}2 was found to show the highest degree of Lewis acid catalysis, whereas two VO(salen)X (X=EtOSO3 or NCS) complexes both displayed lower degrees of Lewis acid catalysis. In the case of reactions catalysed by {Al(salen)}2O and triphenylphosphine oxide, a non‐linear Hammett plot was observed, which is indicative of a change in mechanism with increasing Lewis base catalysis as the carbonyl compound becomes more electron‐deficient. These results suggested that the aluminium complex/triphenylphosphine oxide catalyst system should also catalyse the asymmetric addition of trimethylsilyl cyanide to ketones and this was found to be the case.
To be (Lewis acid catalysed) or not to be, that is the question: A Hammett analysis based on the structure of aldehyde substrates allows the determination of the relative importance of Lewis acid and Lewis base catalysis. The methodology is applied to asymmetric cyanohydrin synthesis catalysed by four complexes and shows that they differ in the degree of Lewis acid catalysis (see figure). Based on the results, it was predicted, and experimentally verified, that an aluminium‐based catalyst would accept ketones as substrates.
Propylene carbonate can be used as a green solvent for the asymmetric synthesis of cyanohydrin trimethylsilyl ethers from aldehydes and trimethylsilyl cyanide catalysed by VO(salen)NCS, though ...reactions are slower in this solvent than the corresponding reactions carried out in dichloromethane. A mechanistic study has been undertaken, comparing the catalytic activity of VO(salen)NCS in propylene carbonate and dichloromethane. Reactions in both solvents obey overall second-order kinetics, the rate of reaction being dependent on the concentration of both the aldehyde and trimethylsilyl cyanide. The order with respect to VO(salen)NCS was determined and found to decrease from 1.2 in dichloromethane to 1.0 in propylene carbonate, indicating that in propylene carbonate, VO(salen)NCS is present only as a mononuclear species, whereas in dichloromethane dinuclear species are present which have previously been shown to be responsible for most of the catalytic activity. Evidence from ⁵¹V NMR spectroscopy suggested that propylene carbonate coordinates to VO(salen)NCS, blocking the free coordination site, thus inhibiting its Lewis acidity and accounting for the reduction in catalytic activity. This explanation was further supported by a Hammett analysis study, which indicated that Lewis base catalysis made a much greater contribution to the overall catalytic activity of VO(salen)NCS in propylene carbonate than in dichloromethane.
Human studies on cognitive control processes rely on tasks involving sudden-onset stimuli, which allow the analysis of these neural imprints to be time-locked and relative to the stimuli onset. Human ...perceptual decisions, however, comprise continuous processes where evidence accumulates until reaching a boundary. Surpassing the boundary leads to a decision where measured brain responses are associated to an internal, unknown onset. The lack of this onset for gradual stimuli hinders both the analyses of brain activity and the training of detectors. This paper studies electroencephalographic (EEG)-measurable signatures of human processing for sudden and gradual cognitive processes represented as a trajectory mismatch under a monitoring task. Time-locked potentials and brain-source analysis of the EEG of sudden mismatches revealed the typical components of event-related potentials and the involvement of brain structures related to cognitive control processing. For gradual mismatch events, time-locked analyses did not show any discernible EEG scalp pattern, despite related brain areas being, to a lesser extent, activated. However, and thanks to the use of non-linear pattern recognition algorithms, it is possible to train an asynchronous detector on sudden events and use it to detect gradual mismatches, as well as obtaining an estimate of their unknown onset. Post-hoc time-locked scalp and brain-source analyses revealed that the EEG patterns of detected gradual mismatches originated in brain areas related to cognitive control processing. This indicates that gradual events induce latency in the evaluation process but that similar brain mechanisms are present in sudden and gradual mismatch events. Furthermore, the proposed asynchronous detection model widens the scope of applications of brain-machine interfaces to other gradual processes.
The mechanism by which four Lewis bases, triethylamine, tetrabutylammonium thiocyanate, tetrabutylammonium azide and tetrabutylammonium cyanide, catalyse the addition of trimethylsilyl cyanide to ...aldehydes is studied by a combination of kinetic and spectroscopic methods. The reactions can exhibit first or second order kinetics corresponding to three different reaction mechanisms. Spectroscopic evidence for the formation of hypervalent silicon species is obtained for reaction between all of the tetrabutylammonium salts and trimethylsilyl cyanide. The reactions are accelerated by the presence of water in the reaction mixture, an effect which is due to a change in the reaction mechanism from Lewis to Brønsted base catalysis. Tetrabutylammonium thiocyanate is shown to be an excellent catalyst for the synthesis of cyanohydrin trimethylsilyl ethers on a preparative scale.
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