Herbicide effects on freshwater benthic diatoms: Induction of nucleus alterations and silica cell wall abnormalities

Benthic diatoms are well known bio-indicators of river pollution by nutrients (nitrogen and phosphorus). Biological indexes, based on diatom sensitivity for non-toxic pollution, have been developed to assess the water quality.Nevertheless, they are not reliable tools to detect pollution by pesticides. Many authors have suggested that toxic agents, like pesticides, induce abnormalities of the diatom cell wall (frustule). High abnormal frustule abundances have been reported in natural diatom communities sampled in streams contaminated by pesticides. However, no direct link was found between the abundances of abnormal frustules in these communities and the pesticide concentrations in stream water. In the present study, a freshwater benthic diatomcommunity, isolated fromnatural biofilm and cultured under controlled conditions, was treated with a known genotoxic herbicide, maleic hydrazide (MH). Cells were exposed to three concentrations of MH (5×10−6, 10−6, 10−7 M) for 6 h followed by a 24 h-recovery time. After MH treatments, nucleus alterations were observed: abnormal nucleus location, micronucleus, multinuclear cell or disruption of the nuclear membrane. A dose-dependent increase of nuclear alterations was observed. The difference between the control (9.65 nuclear alterations per 1000 cells observed (9.65‰), S.D. = 4.23) and the highest concentrations (29.40‰, S.D. = 8.49 for 10−6Mand 35.96‰, S.D. = 3.71 for 5×10−6 M)was statistically significant (Tukey test, P < 0.05). Diatoms also exhibited frustules with deformed morphology and abnormal ornamentation. Significantly increased abundances of abnormal frustules were observed for the highest concentrations (10−6 and 5×10−6 M; Tukey test, P < 0.05). These two parameters tended to increase together (Pearson correlation = 0.702, P < 0.05). The results suggest that the induction of abnormal frustules could be associated with the genotoxic effects of MH. The alterations observed could be related to the effects of MH on the synthesis of the proteins involved in frustule formation or in the regulation of the cytoskeleton of the diatom cells

Characterization of oxidative stress in Leishmaniasis-infected or LPS-stimulated macrophages using electrochemical impedance spectroscopy

The physiological changes caused by external stimuli can be employed as parameters to study pathogen infection in cells and the effect of drugs. Among analytical methods, impedance is potentially useful to give insight into cellular behavior by studying morphological changes, alterations in the physiological state, production of charged or redox species without interfering with in vitro cellular metabolism and labeling. The present work describes the use of electrochemical impedances spectroscopy to simply monitor by modeling impedance plots (Nyquist diagram) in appropriate equivalent circuit, the changes affecting murine macrophage cell line (RAW 264.7) in response to parasite infection by Leishmania amazonensis or to lipopolysaccharide (LPS) treatment. These results demonstrate the ability of electrochemical impedance spectroscopy to discriminate between two opposite cell responses associated to two different stimuli, one caused by the internalization of a parasite, and the other by activation by a bacterium component. Indeed, the study has allowed the characterization, from an electrical point of view, of the extra-cellular NO radical produced endogenously and in great quantities by the inducible form of NO-synthase in the case of LPS-stimulatedmacrophages. This production was not observed in the case of Leishmania-infectedmacrophages for which to survive and multiply, the parasite itself possesses mechanisms which may interfere with NO production. In this latest case, only the intracellular production of ROS was observed. To confirm these interpretations confocal microscopy analysis using the ROS (reactive oxygen species) fluorescent probe 2′,7′-dichlorodihydrofluorescein diacetate and electron paramagnetic resonance experiments using Fe(DETC)2 as NO radical spin trap were carried out

Sensitivity of freshwater periphytic diatoms to agricultural herbicides

The biomonitoring of pesticide pollution in streams and rivers using algae such as diatoms remains difficult. The responses of diatomcommunities to toxic stress in streamwater are disturbed by the variations of environmental parameters. In this study, periphytic algae collected in situwere exposed under controlled conditions to two major herbicides used in French agriculture (isoproturon and s-metolachlor). Three exposure regimes were tested: 5 and 30gL−1 for 6 days and 30gL−1 for 3 days followed by a recovery period of 3 days. The algal biomasses were assessed from pigment concentrations (chlorophyll a and c) and from live cell density. The highest concentration (30gL−1) of isoproturon inhibited the biomass increase statistically significantly. In periphyton exposed to 5 and 30gL−1 of s-metolachlor, chlorophyll c concentration and live cell densitywere also statistically significantly lower than in the control. Periphyton left to recover after reduced exposure duration (3 days) showed higher growth rates after treatment with s-metolachlor than with isoproturon. Taxonomic identifications showed that species like Melosira varians, Nitzschia dissipata and Cocconeis placentula were not affected by the herbicide exposure. Other species like Eolimna minima and Navicula reichardtiana were more sensitive. Studying diatoms according to their trophic mode showed that facultative heterotroph specieswere statistically significantly favoured by isoproturon exposure at the highest concentration. Results obtained with s-metolachlor exposure showed a disturbance of cell multiplication rather than that of photosynthesis. These results suggest that photosynthesis inhibitors like isoproturon favour species able to survive when the autotroph mode is inhibited

A sensor fusion approach for inertial sensors based 3D kinematics and pathological gait assessments: toward an adaptive control of stimulation in post-stroke subjects

International audiencePathological gait assessment and assistive control based on functional electrical stimulation (FES) in post-stroke individuals, brings out a common need to robustly quantify kinematics facing multiple constraints. This study proposes a novel approach using inertial sensors to compute dorsiflexion angles and spatio-temporal parameters, in order to be later used as inputs for online close-loop control of FES. 26 post-stroke subjects were asked to walk on a pressure mat equipped with inertial measurement units (IMU) and passive reflective markers. A total of 930 strides were individually analyzed and results between IMU-based algorithms and reference systems compared. Mean absolute (MA) errors of dorsiflexion angles were found to be less than 4°, while stride lengths were robustly segmented and estimated with a MA error less than 10 cm. These results open new doors to rehabilitation using adaptive FES closed-loop control strategies in "foot drop" syndrome correction

Early Deformation of Deep Brain Stimulation Electrodes Following Surgical Implantation: Intracranial, Brain, and Electrode Mechanics

IntroductionAlthough deep brain stimulation is nowadays performed worldwide, the biomechanical aspects of electrode implantation received little attention, mainly as physicians focused on the medical aspects, such as the optimal indication of the surgical procedure, the positive and adverse effects, and the long-term follow-up. We aimed to describe electrode deformations and brain shift immediately after implantation, as it may highlight our comprehension of intracranial and intracerebral mechanics.Materials and MethodsSixty electrodes of 30 patients suffering from severe symptoms of Parkinson’s disease and essential tremor were studied. They consisted of 30 non-directional electrodes and 30 directional electrodes, implanted 42 times in the subthalamus and 18 times in the ventrolateral thalamus. We computed the x (transversal), y (anteroposterior), z (depth), torsion, and curvature deformations, along the electrodes from the entrance point in the braincase. The electrodes were modelized from the immediate postoperative CT scan using automatic voxel thresholding segmentation, manual subtraction of artifacts, and automatic skeletonization. The deformation parameters were computed from the curve of electrodes using a third-order polynomial regression. We studied these deformations according to the type of electrodes, the clinical parameters, the surgical-related accuracy, the brain shift, the hemisphere and three tissue layers, the gyration layer, the white matter stem layer, and the deep brain layer (type I error set at 5%).ResultsWe found that the implanted first hemisphere coupled to the brain shift and the stiffness of the type of electrode impacted on the electrode deformations. The deformations were also different according to the tissue layers, to the electrode type, and to the first-hemisphere-brain-shift effect.ConclusionOur findings provide information on the intracranial and brain biomechanics and should help further developments on intracerebral electrode design and surgical issues

Synthesis of melatoninergic and serotoninergic ligands with benzoindolic, azaindolic and indolic cores

La mélatonine est une hormone produite par la glande pinéale durant la nuit. Des études ont montré que des agonistes des récepteurs mélatoninergiques (MT1 et MT2) pouvaient être des antidépresseurs efficaces. Ainsi, a été développée l’agomélatine, un puissant antidépresseur commercialisé par les Laboratoires Servier sous le nom de valdoxan®, agoniste des récepteurs MT1, MT2 et antagoniste du récepteur 5-HT2C. Le travail de cette thèse a eu pour but d’élaborer un successeur à l’agomélatine possédant un profil pharmacologique similaire. Dans une première partie, des ligands à structure 4- et 6-azaindolique ont été synthétisés. Notre premier effort a été de développer la voie de synthèse de ces molécules via la réaction de Fischer, puis, ce travail a débouché sur l’optimisation de cette réaction par l’utilisation des micro-ondes. Par la suite, notre recherche s’est portée sur la synthèse de composés 7-azaindoliques et benzoindiques, ceci découlant d’une étude de la relation structure-activité entre les ligands et les récepteurs MT. Ensuite, ont été synthétisés des analogues à structure indolique ayant une affinité pour les récepteurs MT1 et MT2 connue, sur laquelle nous avons greffé un motif bispyridinique sensé apporté une activité 5- HT2C. Enfin, des ligands indoliques dichlorés ont également été mis au point. L’ensemble de ce travail a permis l’élaboration de quelques composés dont le profil est intéressant et qui sont toujours à l’étude.Melatonin is a hormone produced by the pineal gland during the night. Some studies have shown that agonists of melatoninergic receptors (MT1 and MT2) could be efficient antidepressants. Few years ago, Agomelatine, an agonist of MT1, MT2 receptors and antagonist of 5-HT2C receptor, was developed by Les Laboratoires Servier, The goal of this thesis was to design a molecule with a similar pharmacological profile. First, some 4- and 6-azaindolic ligands were synthesised. We work around the development of the method to synthesised this molecules via the Fischer cyclisation and improved it by micro-ondes using. Second, following structure-activity studies with MT receptors, we have synthesised 7-azaindolics and benzoindolics compounds. Third, some indolics analogs presenting a good MT1 and MT2 affinity were coupled with a bispyridinic entity to enhance an 5-HT2C activity. Finally, dichloroindolics ligands were synthesised. All this work allows the synthesis of interesting ligands. Some of these molecules are still on study

Etude de la fonction et des mécanismes du wind-up des neurones nociceptifs trigéminaux chez le rat: rôle des récepteurs NMDA et des récepteurs NK1

Wind-up is a frequency-dependent increase of neuronal response during electrical repetitive noxious stimulation of receptive field. This phenomenon is generally expressed in spinal and trigeminal WDR neurons. It partially depends on the activation of NMDA and NK1 receptors. In human, wind-up is related with the temporal summation and has consequences on the perception of pain. Its functional significance is not yet clearly established. In sensory trigeminal complex of anaesthetized rat, we aim at: 1) analysing the characteristics and function of the wind-up of trigeminal WDR neurons. 2) identifying the neural networks underlying the wind -up and 3) establishing the role of rNMDA and rNK1 in this phenomenon. We use an electrophysiological approach with extracellular recordings in the Sp5O associated with microinjections in the Sp5C. Moreover a neuroanatomical study allowed identifying networks of interneurones conveying the message since the Sp5C towards the Sp5O. 1) the wind-up of WDR neurons of the Sp5O depends on the intensity of noxious stimulation and makes it possible to improve the coding capacities of short duration noxious stimuli. In addition, we show that wind -up involves a transitory modification (approximately 2min duration) of the WDR neurons exci tability. The modification of excitability generated by the wind-up is responsible only for the facilitation responses evoked by C fibres. We suggest that the increase in the central excitability generated by the wind-up and central sensitization are different phenomena. 2) wind-up depends on the activation of the local rNMDA whereas it is submitted to an inhibition mediated by the rNMDA located in the superficial layers of the Sp5C. The trigeminal model enables to show that, even at the segmentary level, there is a permanent adjustment of the amplification of the painful message. 3) finally, the development of the wind-up also depends on the activation of the rNK1 located on interneurones localised of the lamina III of the Sp5C. To conclude, it appears that wind-up is a segmentary phenomenon allowing the coding of short duration noxious stimulations and triggered by rNK1 and rNMDA polysynaptic ways.Le wind-up est une augmentation progressive, fréquence dépendante, de la réponse d'un neurone lors de l'application répétitive de stimuli électriques nociceptifs identiques sur un même territoire. Ce phénomène est essentiellement exprimé par les neurones WDR de la moelle comme du trijumeau. Il dépend en partie de l'activation des récepteurs NMDA et NK1. Il est apparenté chez l'homme à la sommation temporelle et a des conséquences sur la perception de la douleur. Sa signification fonctionnelle n'est pas encore clairement établie. Chez le rat anesthésié et au sein du complexe sensitif du trijumeau, l'objectif de ce travail est : 1) d'analyser les caractéristiques et la fonction du wind-up des neurones WDR trigéminaux, 2) d'identifier les réseaux neuronaux sous tendant le wind-up et 3) d'établir le rôle des rNMDA et des rNK1 dans le wind-up. Nous avons adopté une approche électrophysiologique lors d'enregistrements extracellulaires au sein du Sp5O associés à des micro injections dans le Sp5C. De plus, une approche neuroanatomique a permis d'identifier des réseaux d'interneurones véhiculant le message depuis le Sp5C vers le Sp5O. 1) le wind-up des neurones WDR du Sp5O dépend de l'intensité de la stimulation nociceptive et permet d'améliorer les capacités de codage de stimuli nociceptifs de courte durée. Par ailleurs, nous montrons que le wind-up entraine une modification transitoire (environ 2min) de l'excitabilité des neurones WDR. Cette modification d'excitabilité générée par la wind-up est responsable uniquement de la facilitation des réponses évoquées par la mise en jeu des fibres C. Nous suggérons que l'augmentation de l'excitabilité centrale générée par le wind-up et la sensibilisation centrale sont des phénomènes différents. 2) le wind-up dépend de l'activation des rNMDA locaux alors qu'il est soumis à une inhibition via les rNMDA situés dans les couches superficielles du Sp5C. Le modèle trigéminal permet donc de montrer que, dès l'étage segmentaire, il existe un ajustement permanent de l'amplification du message douloureux. 3) enfin, le développement du wind-up dépend également de l'activation des rNK1 situés sur des interneurones localisés dans la couche III du Sp5C. En conclusion, il apparaît que le wind-up est un phénomène segmentaire permettant le codage de stimulations nociceptives de courte durée et sous tendu à la mise en jeu de voies polysynaptiques rNK1 et rNMDA dépendantes

Etude de la fonction et des mécanismes du wind-up des neurones nociceptifs trigéminaux chez le rat (rôle des récepteurs NMDA et des récepteurs NK1)

CLERMONT FD-BCIU Odontol. (631132226) / SudocCLERMONT FD-BCIU-Santé (631132104) / SudocSudocFranceF