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Marianne Graber - One of the best experts on this subject based on the ideXlab platform.
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Metabolomics based on UHPLC-QToF- and APGC-QToF-MS reveals metabolic pathways reprogramming in response to tidal cycles in the sub-littoral species Mimachlamys varia exposed to aerial emergence
Comparative Biochemistry and Physiology - Part D: Genomics and Proteomics, 2019Co-Authors: Pascaline Ory, Antoine Bonnet, Florence Mondeguer, Marine Breitwieser, Emmanuel Dubillot, Marianne GraberAbstract:Mimachlamys varia is a sub-littoral bivalve encountered from Norway to the Mediterranean Sea, which lives mostly byssally attached to rocks. During the low tide period, M. varia individuals, located highest on the shore, may experience short time of aerial exposure and face a low availability of oxygen. Here we report a comparative metabolomic profiling of gill samples of M. varia obtained by both LC-QToF and APGC-QToF mass spectrometry, to analyze metabolic changes occurring during Emersion in comparison with immersion. Scallops were grown in aquaria with a simulated intertidal environment mimicking short-duration air exposure that they might experience during extreme tides: alternating 2 h Emersion and 10 h immersion. Our results show a switch from aerobic to anaerobic metabolism after only 2 h of Emersion, with the resort to different pathways: glucose-lactate, glucose-succinate and aspartate-succinate pathways. Furthermore, carnitine-conjugated metabolites were found to accumulate during Emersion, as well as urate. The level of tyrosine on the contrary was found to decrease. These findings indicate a complex metabolic reprogramming that occurs after a two hour Emersion period and upon re-immersion. Furthermore, M. varia is used as sentinel species in pollution biomonitoring, through the assay of biomarkers to evaluate the effects of pollutants. Here we show that Emersion induces a significant decrease of superoxide dismutase activity, an enzyme developed by bivalves to face oxidative stress and used as biomarker. These findings have to be taken into account to normalize sampling during campaigns of environmental monitoring, by taking in situ, as far as possible only immersed individuals.
Tianyao Chen - One of the best experts on this subject based on the ideXlab platform.
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An Ankle-Foot Prosthesis Emulator with Control of Plantarflexion and Inversion-Eversion Torques
2018Co-Authors: Steven Collins, Myunghee Kim, Tianjian Chen, Tianyao ChenAbstract:Ankle inversion-eversion compliance is an important feature of conventional prosthetic feet, and control of inversion, or roll, in robotic prostheses could improve balance for people with amputation. We designed a tethered ankle-foot prosthesis with two independently-actuated toes that are coordinated to provide plantarflexion and inversion-eversion torques. This configuration allows a simple lightweight structure with a total mass of 0.72 kg. Strain gages on the toes measure torque with less than 2.7% RMS error, while compliance in the Bowden cable tether provides series elasticity. Benchtop tests demonstrated a 90% rise time of less than 33 ms and peak torques of 180 N·m in plantarflexion and ±30 N·m in inversion-eversion. The phase-limited closedloop torque bandwidth is 20 Hz with a 90 N·m amplitude chirp in plantarflexion, and 24 Hz with a 20 N·m amplitude chirp in inversion-eversion. The system has low sensitivity to toe position disturbances at frequencies of up to 18 Hz. Walking trials with five values of constant inversion-eversion torque demonstrated RMS torque tracking errors of less than 3.7% in plantarflexion and less than 5.9% in inversion-eversion. These properties make the platform suitable for haptic rendering of virtual devices in experiments with humans, which may reveal strategies for improving balance or allow controlled comparisons of conventional prosthesis features. A similar morphology may be effective for autonomous devices.
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an ankle foot prosthesis emulator with control of plantarflexion and inversion eversion torque
International Conference on Robotics and Automation, 2015Co-Authors: Steven H. Collins, Myunghee Kim, Tianjian Chen, Tianyao ChenAbstract:Ankle inversion-eversion compliance is an important feature of conventional prosthetic feet, and control of inversion, or roll, in robotic prostheses could improve balance for people with amputation. We designed a tethered ankle-foot prosthesis with two independently-actuated toes that are coordinated to provide plantarflexion and inversion-eversion torques. This configuration allows a simple lightweight structure with a total mass of 0.72 kg. Strain gages on the toes measure torque with less than 2.7% RMS error, while compliance in the Bowden cable tether provides series elasticity. Benchtop tests demonstrated a 90% rise time of less than 33 ms and peak torques of 180 N·m in plantarflexion and ±30 N·m in inversion-eversion. The phase-limited closedloop torque bandwidth is 20 Hz with a 90 N·m amplitude chirp in plantarflexion, and 24 Hz with a 20 N·m amplitude chirp in inversion-eversion. The system has low sensitivity to toe position disturbances at frequencies of up to 18 Hz. Walking trials with five values of constant inversion-eversion torque demonstrated RMS torque tracking errors of less than 3.7% in plantarflexion and less than 5.9% in inversion-eversion. These properties make the platform suitable for haptic rendering of virtual devices in experiments with humans, which may reveal strategies for improving balance or allow controlled comparisons of conventional prosthesis features. A similar morphology may be effective for autonomous devices.
Steven H. Collins - One of the best experts on this subject based on the ideXlab platform.
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Step-to-Step Ankle Inversion/Eversion Torque Modulation Can Reduce Effort Associated with Balance
Frontiers Media S.A., 2017Co-Authors: Myunghee Kim, Steven H. CollinsAbstract:Below-knee amputation is associated with higher energy expenditure during walking, partially due to difficulty maintaining balance. We previously found that once-per-step push-off work control can reduce balance-related effort, both in simulation and in experiments with human participants. Simulations also suggested that changing ankle inversion/eversion torque on each step, in response to changes in body state, could assist with balance. In this study, we investigated the effects of ankle inversion/eversion torque modulation on balance-related effort among amputees (N = 5) using a multi-actuated ankle-foot prosthesis emulator. In stabilizing conditions, changes in ankle inversion/eversion torque were applied so as to counteract deviations in side-to-side center-of-mass acceleration at the moment of intact-limb toe off; higher acceleration toward the prosthetic limb resulted in a corrective ankle inversion torque during the ensuing stance phase. Destabilizing controllers had the opposite effect, and a zero gain controller made no changes to the nominal inversion/eversion torque. To separate the balance-related effects of step-to-step control from the potential effects of changes in average mechanics, average ankle inversion/eversion torque and prosthesis work were held constant across conditions. High-gain stabilizing control lowered metabolic cost by 13% compared to the zero gain controller (p = 0.05). We then investigated individual responses to subject-specific stabilizing controllers following an enforced exploration period. Four of five participants experienced reduced metabolic rate compared to the zero gain controller (−15, −14, −11, −6, and +4%) an average reduction of 9% (p = 0.05). Average prosthesis mechanics were unchanged across all conditions, suggesting that improvements in energy economy might have come from changes in step-to-step corrections related to balance. Step-to-step modulation of inversion/eversion torque could be used in new, active ankle-foot prostheses to reduce walking effort associated with maintaining balance
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an ankle foot prosthesis emulator with control of plantarflexion and inversion eversion torque
International Conference on Robotics and Automation, 2015Co-Authors: Steven H. Collins, Myunghee Kim, Tianjian Chen, Tianyao ChenAbstract:Ankle inversion-eversion compliance is an important feature of conventional prosthetic feet, and control of inversion, or roll, in robotic prostheses could improve balance for people with amputation. We designed a tethered ankle-foot prosthesis with two independently-actuated toes that are coordinated to provide plantarflexion and inversion-eversion torques. This configuration allows a simple lightweight structure with a total mass of 0.72 kg. Strain gages on the toes measure torque with less than 2.7% RMS error, while compliance in the Bowden cable tether provides series elasticity. Benchtop tests demonstrated a 90% rise time of less than 33 ms and peak torques of 180 N·m in plantarflexion and ±30 N·m in inversion-eversion. The phase-limited closedloop torque bandwidth is 20 Hz with a 90 N·m amplitude chirp in plantarflexion, and 24 Hz with a 20 N·m amplitude chirp in inversion-eversion. The system has low sensitivity to toe position disturbances at frequencies of up to 18 Hz. Walking trials with five values of constant inversion-eversion torque demonstrated RMS torque tracking errors of less than 3.7% in plantarflexion and less than 5.9% in inversion-eversion. These properties make the platform suitable for haptic rendering of virtual devices in experiments with humans, which may reveal strategies for improving balance or allow controlled comparisons of conventional prosthesis features. A similar morphology may be effective for autonomous devices.
Dominique Davoult - One of the best experts on this subject based on the ideXlab platform.
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Dynamics of Fucus serratus thallus photosynthesis and community primary production during Emersion across seasons: canopy dampening and biochemical acclimation
2020Co-Authors: Aline Migne, Dominique Menu, Dominique Davoult, Gwendoline Duong, François GévaertAbstract:The brown alga Fucus serratus forms dense stands on the sheltered low intertidal rocky shores of the Northeast Atlantic coast. In the southern English Channel, these stands have proved to be highly productive, particularly during Emersion periods. Here, we studied the dampening effect of the canopy cover, associated with physiological and biochemical acclimation processes, that allows this species to withstand Emersion stress. The F. serratus community primary production and the photosynthetic performance of thalli were concurrently followed in situ, throughout the midday Emersion period, in different seasons and under various weather conditions. In addition, thallus samples were taken at various tidal stages to determine their content in biochemical compounds involved in photoprotective and antioxidant mechanisms. Under high light and temperature, the F. serratus community exhibited high aerial production rates (sometimes exceeding 1 g C m-2 h-1) that never decreased to less than 59% of the initial value during the Emersion period. Under mild weather conditions, photosynthesis in thalli at the top of the canopy (measured as the relative electron transport rate) varied in response to changing incident light. Under harsh weather conditions (i.e. high light and temperature), the effective quantum yield of photosystem II (ΦPSII) dramatically decreased in thalli at the top of the canopy, but remained high in thalli at the bottom of or within the canopy. Due to self-shading, photosynthesis was light-limited in thalli in the lowest layer of the canopy, but was effective in thalli in the intermediate layers. Photoinhibition was observed in thalli at the top of the canopy (as a dramatic decrease in the optimal photosynthetic quantum yield Fv/Fm), but not in thalli beneath the canopy. At the end of the Emersion period, Fv/Fm was strongly correlated to the relative water content of thalli. The findings from our simultaneous analysis of biochemical and photosynthetic parameters suggest coordination between the xanthophyll and the ascorbateglutathione cycles that varies with season. An accumulation of hydrogen peroxide was nevertheless observed once, indicating that oxidative stress is nonetheless possible under particularly harsh conditions.
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Photosynthesis of Laminaria digitata during the immersion and Emersion periods of spring tidal cycles during hot, sunny weather
2019Co-Authors: Aline Migne, Gaspard Delebecq, Nicolas Spilmont, Dominique Menu, Dominique Davoult, Marie-andrée Janquin, François GévaertAbstract:The boreal kelp Laminaria digitata dominates the low intertidal and upper subtidal zones of moderately exposed rocky shores in north-western Europe. Due to ocean warming, this foundation species is predicted to disappear from French coasts in the near future. Photosynthesis of L. digitata sporophytes was surveyed in situ during spring and summer tidal cycles with Emersion periods around midday during hot, sunny weather. The net production (NP) of whole individuals (i.e. the difference between their gross primary production and respiration) was assessed by measuring carbon fluxes inside a closed chamber. Photosynthetic performance of thalli was assessed using pulse-amplitude modulated (PAM) fluorescence parameters, the effective (ΦPSII) and optimal (Fv/Fm) quantum yields of photosystem II. Content in pigments involved in the xanthophyll cycle, a photoprotective mechanism, was measured in thalli to evaluate the de-epoxidation ratio (DR). NP shifted from positive values (reaching 140 μmol C gDW-1 h-1) during morning immersion to negative values uduring Emersion (reaching -37 μmol C gDW-1 h-1), and did not return to positive values during the following immersion period when respiration was exacerbated. ΦPSII decreased during Emersion (down to 0.01), but recovered during afternoon immersion. Fv/Fm decreased during Emersion (down to 0.18) indicating severe photoinhibition. High DR values (up to 0.70) showed the effectiveness of the photoprotective mechanism, which appeared nevertheless insufficient to prevent photodamage during Emersion stress. Among the environmental factors contributing to this Emersion stress, repeated heat shocks over consecutive tide cycles likely play a leading role. These repeated heat shocks appear to further exacerbate the detrimental effects of warming events on this marginal population of L. digitata.
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photosynthetic activity and productivity of intertidal macroalgae in situ measurements from thallus to community scale
Aquatic Botany, 2015Co-Authors: Aline Migne, Gaspard Delebecq, Nicolas Spilmont, Dominique Davoult, Dominique MenuAbstract:The photosynthetic activity and productivity of four dominant canopy intertidal macroalgae were measured under Emersion and immersion, at saturating light levels (PAR > 300 μmol photons m−2 s−1), and compared at two sites (eastern and western English Channel) in spring and summer. The photosynthetic activity of thalli was measured by the electron transport rate (ETR) using pulse-amplitude modulated (PAM) fluorescence and the productivity of individuals and of communities was measured by carbon fluxes in closed chambers. Under Emersion, when thalli were still hydrated, the uppermost species Pelvetia canaliculata had higher photosynthetic activity (mean ETR between 327 and 460 μmol e− m−2 s−1) and individual gross productivity (between 60 and 212 μmol C gDW−1 h−1) than the lowermost species Laminaria digitata (mean ETR between 24 and 53 μmol e− m−2 s−1 and gross productivity between 2 and 38 μmol C gDW−1 h−1), whatever the site and season. P. canaliculata had higher ETR in air than underwater (averaged 146 μmol e− m−2 s−1) and L. digitata had lower ETR in air than underwater (averaged 112 μmol e− m−2 s−1), while they exhibited respectively 3 and 5 times higher gross productivity underwater. At the community scale, the low mid-shore zone of Fucus serratus had the highest mean gross productivity under Emersion (47 mmol C m−2 h−1) while rates were higher for the uppermost than lowermost zone at the eastern site (average 20 and 6 mmol C m−2 h−1 respectively) and of the same order of magnitude for both zones at the western site (about 30 mmol C m−2 h−1). Finally, the variability of under Emersion primary productivity among sites and seasons was reduced when the measurements were performed on entire communities compared to isolated individuals of the dominant species.
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community level carbon flux variability over a tidal cycle in zostera marina and z noltii beds
Marine Ecology Progress Series, 2011Co-Authors: Vincent Ouisse, Aline Migne, Dominique DavoultAbstract:Abiotic parameters such as light, temperature, nutrient availability and inorganic carbon source are known to vary widely between immersion and Emersion. We measured gross community productivity (GCP) and community respiration (CR) over spring tidal cycles in intertidal Zostera marina and Z. noltii communities. CO2 fluxes during Emersion and inorganic carbon fluxes during immersion were assessed using closed benthic chambers. GCP and CR rates were significantly higher during immersion than during Emersion for both communities. In July, GCP rates were 3- and 5-fold higher and CR rates were 2.5- and 9-fold higher during immersion for the Z. marina and Z. noltii communities, respectively. This trend was confirmed in the Z. noltii community at different periods of the year (February, April and November). Neither photoinhibition nor desiccation was measured during Emersion, but shading might have greatly limited the GCP rates. Higher CR during immersion could be explained by enhanced bacterial and infaunal activity.
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Annual budget of benthic production in Mont Saint-Michel Bay considering cloudiness, microphytobenthos migration, and variability of respiration rates with tidal conditions
Continental Shelf Research, 2009Co-Authors: Aline Migne, Nicolas Spilmont, G. Boucher, L. Denis, C. Hubas, M. -a. Janquin, M. Rauch, Dominique DavoultAbstract:In order to provide an accurate annual rate of net benthic community production, community photosynthetic response to incident irradiance and respiration were measured at different times of the year, at mid-tide level on the muddiest part of the Mont Saint-Michel Bay. As the water turbidity prevented any photosynthesis by the microphytobenthos during immersion periods, primary production was measured only during Emersion periods. In contrast respiration was expected to vary according to the tidal cycle and was measured during both Emersion and immersion periods. Primary production and respiration rates under Emersion were assessed using in situ infra-red gas analysis of CO(2) exchange measured in a benthic chamber. Respiration rates under immersion were assessed through total CO(2) concentration variations in incubated cores. When respiration rate was considered constant over a day and equal to the rate measured under emerged conditions, the community respiration was 54.56 gC m(-2) yr(-1). Taking into account the variations of respiration during the Emersion/immersion cycle, community respiration increased to 101.76 gC m(-2) yr(-1) (86% increase). Assuming that community primary production varied as a function of irradiance from the time of exposure until flooding, GCP was 53.22 gC m(-2) yr(-1) when calculated with theoretical irradiance and 45.86 gC m(-2) yr(-1) after correction for cloudiness (14% decrease). Then, by integrating the effect of vertical migration of microphytobenthos, the rate was adjusted to 23.49 gC m(-2) yr(-1) (49% decrease). The net community production budget, calculated as the difference between the GCP and the CR budgets taking into account the corrections described above, was -78.27 gC m(-2) yr(-1). This example of annual budget calculation highlights the need to integrate several processes occurring over various time scales to accurately reflect the metabolic balance of a system The results also confirmed the heterotrophic status generally suggested for intertidal muddy sediments. (C) 2009 Elsevier Ltd. All rights reserved.
Pascaline Ory - One of the best experts on this subject based on the ideXlab platform.
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Metabolomics based on UHPLC-QToF- and APGC-QToF-MS reveals metabolic pathways reprogramming in response to tidal cycles in the sub-littoral species Mimachlamys varia exposed to aerial emergence
Comparative Biochemistry and Physiology - Part D: Genomics and Proteomics, 2019Co-Authors: Pascaline Ory, Antoine Bonnet, Florence Mondeguer, Marine Breitwieser, Emmanuel Dubillot, Marianne GraberAbstract:Mimachlamys varia is a sub-littoral bivalve encountered from Norway to the Mediterranean Sea, which lives mostly byssally attached to rocks. During the low tide period, M. varia individuals, located highest on the shore, may experience short time of aerial exposure and face a low availability of oxygen. Here we report a comparative metabolomic profiling of gill samples of M. varia obtained by both LC-QToF and APGC-QToF mass spectrometry, to analyze metabolic changes occurring during Emersion in comparison with immersion. Scallops were grown in aquaria with a simulated intertidal environment mimicking short-duration air exposure that they might experience during extreme tides: alternating 2 h Emersion and 10 h immersion. Our results show a switch from aerobic to anaerobic metabolism after only 2 h of Emersion, with the resort to different pathways: glucose-lactate, glucose-succinate and aspartate-succinate pathways. Furthermore, carnitine-conjugated metabolites were found to accumulate during Emersion, as well as urate. The level of tyrosine on the contrary was found to decrease. These findings indicate a complex metabolic reprogramming that occurs after a two hour Emersion period and upon re-immersion. Furthermore, M. varia is used as sentinel species in pollution biomonitoring, through the assay of biomarkers to evaluate the effects of pollutants. Here we show that Emersion induces a significant decrease of superoxide dismutase activity, an enzyme developed by bivalves to face oxidative stress and used as biomarker. These findings have to be taken into account to normalize sampling during campaigns of environmental monitoring, by taking in situ, as far as possible only immersed individuals.