Motor flexibility: neuronal control of walking direction and walking speed in an insect

The neuronal basis of locomotion is largely investigated in many different vertebrate and invertebrate species. Especially studying the neuronal control of adaptive locomotor behaviors is important to reveal general insights into nervous system function. In this thesis, the stick insects Carausius morosus and Cuniculina impigra were used to investigate how important parts of the locomotor network generate different walking directions and walking speeds. In order to study which parameters have to be changed to generate the different behaviors, leg muscle, motoneuron, and premotor nonspiking interneuron activity was recorded. In the first part, leg muscle activity during forward, backward, and curve walking was studied in a slippery surface setup, in which the animal is stationary about a slippery substrate and all legs can freely move. Muscle activity and timing was compared during different walking directions. The main change was observed in protractor and retractor muscles which move the leg in anterior and posterior direction. These muscles almost completely reverse their phase of activity with the change of walking direction, and intermediate changes occur in the inside leg during curve walking, depending on the steepness of the curve. In the second and third part, leg motoneuron and interneuron activity was recorded intracellularly in the single-leg preparation, in which only one leg is able to move in the vertical plane on a treadwheel. Fictive forward and backward walking can be reliably elicited in this preparation. It is known that leg motoneurons receive tonic depolarizing synaptic inputs from higher centers throughout walking, and additional phasic excitatory and inhibitory inputs from leg sense organs, as well as phasic inhibitory inputs from the rhythm generating network. It could be shown that similar inputs shape the motoneuron modulation pattern also during backward walking. The phase of the step cycle in which the phasic inputs to protractor and retractor MNs occur reverses during backward walking. It was shown previously that stepping velocity in the single-leg preparation is correlated to flexor MN activity (stance) but not extensor MN (swing) activity. These findings are confirmed in this thesis and also held for backward walking. No such influences could be shown for other stance phase motoneurons. Furthermore, premotor nonspiking interneurons were recorded to investigate their contribution to the generation of different walking directions and walking speeds. These neurons are known to integrate signals from descending, central, and sensory sources and thus contribute to the control of timing and magnitude of the motor output. Previously identified (E3, E4, E5, E7, I1, I2), as well as newly described nonspiking interneurons providing synaptic drive to motoneurons of all leg joints were recorded during forward and backward stepping. Interestingly, neurons could be identified which contribute to the change in protractor and retractor muscle activity. Furthermore it could be shown that all recorded nonspiking interneurons contribute to the motor output during walking in both directions, suggesting that the same premotor network is responsible for the generation of both behaviors. NSI activity also underlies tonic and phasic synaptic inputs. Additionally, the contribution of NSIs to the generation of different stepping velocities was investigated

Customized Woven Carbon Fiber Electrodes for Bioelectrochemical Systems—A Study of Structural Parameters

Commercial carbon fiber (CF) fabrics are popular electrode materials for bioelectrochemical systems (BES), but are usually not optimized for the specific application. This study investigates BES-relevant material characteristics on fabric level, such as weave types and weave parameters. The two contrasting weave types plain and leno weave were characterized with respect to their envisaged application types: 1) BES with mainly advective flow regimes and 2) stirred systems, which could benefit from fluid flow through a fabric electrode. Experiments with batch and continuously fed pure cultures of Geobacter sulfurreducens PCA and Shewanella oneidensis MR-1 reveal that µm-scale electrode topologies are of limited use for the thick biofilms of G. sulfurreducens , but can boost S. oneidensis ’ current generation especially in batch and fed-batch reactors. For advective flow regimes, deeper layers of biofilm inside microporous electrodes are often mass transport limited, even with thin biofilms of S. oneidensis . Therefore, low porosity plain weave electrodes for advective flow operation as in wastewater treating BES should be thin and flat. A trade-off between maximized current density and electrode material utilization exists, which is optimized exemplarily for an advective flow operation. For stirred BES of biotechnological applications, a flow-through of electrolyte is desired. For this, leno weave fabrics with pores at cm-scale are produced from 100% CF for the first time. In a preliminary evaluation, they outperform plain weave fabrics. Mass transfer investigations in stirred BES demonstrate that the large pores enable efficient electrode utilization at lower power input in terms of stirring speed

Intravital Two-Photon Microscopy of Immune Cell Dynamics in Corneal Lymphatic Vessels

BACKGROUND: The role of lymphatic vessels in tissue and organ transplantation as well as in tumor growth and metastasis has drawn great attention in recent years. METHODOLOGY/PRINCIPAL FINDINGS: We now developed a novel method using non-invasive two-photon microscopy to simultaneously visualize and track specifically stained lymphatic vessels and autofluorescent adjacent tissues such as collagen fibrils, blood vessels and immune cells in the mouse model of corneal neovascularization in vivo. The mouse cornea serves as an ideal tissue for this technique due to its easy accessibility and its inducible and modifiable state of pathological hem- and lymphvascularization. Neovascularization was induced by suture placement in corneas of Balb/C mice. Two weeks after treatment, lymphatic vessels were stained intravital by intrastromal injection of a fluorescently labeled LYVE-1 antibody and the corneas were evaluated in vivo by two-photon microscopy (TPM). Intravital TPM was performed at 710 nm and 826 nm excitation wavelengths to detect immunofluorescence and tissue autofluorescence using a custom made animal holder. Corneas were then harvested, fixed and analyzed by histology. Time lapse imaging demonstrated the first in vivo evidence of immune cell migration into lymphatic vessels and luminal transport of individual cells. Cells immigrated within 1-5.5 min into the vessel lumen. Mean velocities of intrastromal corneal immune cells were around 9 µm/min and therefore comparable to those of T-cells and macrophages in other mucosal surfaces. CONCLUSIONS: To our knowledge we here demonstrate for the first time the intravital real-time transmigration of immune cells into lymphatic vessels. Overall this study demonstrates the valuable use of intravital autofluorescence two-photon microscopy in the model of suture-induced corneal vascularizations to study interactions of immune and subsequently tumor cells with lymphatic vessels under close as possible physiological conditions

LC‐IMPACT: A regionalized life cycle damage assessment method

Life cycle impact assessment (LCIA) is a lively field of research, and data and models are continuously improved in terms of impact pathways covered, reliability, and spatial detail. However, many of these advancements are scattered throughout the scientific literature, making it difficult for practitioners to apply the new models. Here, we present the LC‐IMPACT method that provides characterization factors at the damage level for 11 impact categories related to three areas of protection (human health, ecosystem quality, natural resources). Human health damage is quantified as disability adjusted life years, damage to ecosystem quality as global species extinction equivalents (based on potentially disappeared fraction of species), and damage to mineral resources as kilogram of extra ore extracted. Seven of the impact categories include spatial differentiation at various levels of spatial scale. The influence of value choices related to the time horizon and the level of scientific evidence of the impacts considered is quantified with four distinct sets of characterization factors. We demonstrate the applicability of the proposed method with an illustrative life cycle assessment example of different fuel options in Europe (petrol or biofuel). Differences between generic and regionalized impacts vary up to two orders of magnitude for some of the selected impact categories, highlighting the importance of spatial detail in LCIA. This article met the requirements for a gold – gold JIE data openness badge described at http://jie.click/badges.info:eu-repo/semantics/publishedVersio

Intracellular calcium strongly potentiates agonist-activated TRPC5 channels

TRPC5 is a calcium (Ca2+)-permeable nonselective cation channel expressed in several brain regions, including the hippocampus, cerebellum, and amygdala. Although TRPC5 is activated by receptors coupled to phospholipase C, the precise signaling pathway and modulatory signals remain poorly defined. We find that during continuous agonist activation, heterologously expressed TRPC5 currents are potentiated in a voltage-dependent manner (∼5-fold at positive potentials and ∼25-fold at negative potentials). The reversal potential, doubly rectifying current–voltage relation, and permeability to large cations such as N-methyl-d-glucamine remain unchanged during this potentiation. The TRPC5 current potentiation depends on extracellular Ca2+: replacement by Ba2+ or Mg2+ abolishes it, whereas the addition of 10 mM Ca2+ accelerates it. The site of action for Ca2+ is intracellular, as simultaneous fura-2 imaging and patch clamp recordings indicate that potentiation is triggered at ∼1 µM [Ca2+]. This potentiation is prevented when intracellular Ca2+ is tightly buffered, but it is promoted when recording with internal solutions containing elevated [Ca2+]. In cell-attached and excised inside-out single-channel recordings, increases in internal [Ca2+] led to an ∼10–20-fold increase in channel open probability, whereas single-channel conductance was unchanged. Ca2+-dependent potentiation should result in TRPC5 channel activation preferentially during periods of repetitive firing or coincident neurotransmitter receptor activation

Mobility in a Globalised World 2014

The term mobility has different meanings in the following science disciplines. In economics, mobility is the ability of an individual or a group to improve their economic status in relation to income and wealth within their lifetime or between generations. In information systems and computer science, mobility is used for the concept of mobile computing, in which a computer is transported by a person during normal use. Logistics creates by the design of logistics networks the infrastructure for the mobility of people and goods. Electric mobility is one of today’s solutions from engineering perspective to reduce the need of energy resources and environmental impact. Moreover, for urban planning, mobility is the crunch question about how to optimise the different needs for mobility and how to link different transportation systems. In this publication we collected the ideas of practitioners, researchers, and government officials regarding the different modes of mobility in a globalised world, focusing on both domestic and international issues

Task-dependent Modification of Leg Motor Neuron Synaptic Input Underlying Changes in Walking Direction and Walking Speed

Rosenbaum P, Schmitz J, Schmidt J, Bueschges A. Task-dependent Modification of Leg Motor Neuron Synaptic Input Underlying Changes in Walking Direction and Walking Speed. Journal of Neurophysiology. 2015;144(2):1090-1101.Animals modify their behavior constantly to perform adequately in their environment. In terrestrial locomotion many forms of adaptation exist. Two tasks are changes of walking direction and walking speed. We investigated these two changes in motor output in the stick insect Cuniculina impigra to see how they are brought about at the level of leg motor neurons. We used a semi-intact preparation in which we can record intracellularly from leg motor neurons during walking. In this single-leg preparation the middle leg of the animal steps in a vertical plane on a treadwheel. Stimulation of either abdomen or head reliably elicits fictive forward or backward motor activity, respectively, in the fixed and otherwise deafferented thorax-coxa joint. With a change of walking direction only thorax-coxa-joint motor neurons protractor and retractor changed their activity. The protractor switched from swing activity during forward to stance activity during backward walking, and the retractor from stance to swing. This phase switch was due to corresponding change of phasic synaptic inputs from inhibitory to excitatory and vice versa at specific phases of the step cycle. In addition to phasic synaptic input a tonic depolarization of the motor neurons was present. Analysis of changes in stepping velocity during stance showed only a significant correlation to flexor motor neuron activity, but not to that of retractor and depressor motor neurons during forward walking. These results show that different tasks in the stick insect walking are generated by altering synaptic inputs to specific leg joint motor neurons only

Task-dependent modification of leg motor neuron synaptic input underlying changes in walking direction and walking speed

Animals modify their behavior constantly to perform adequately in their environment. In terrestrial locomotion many forms of adaptation exist. Two tasks are changes of walking direction and walking speed. We investigated these two changes in motor output in the stick insect Cuniculina impigra to see how they are brought about at the level of leg motor neurons. We used a semi-intact preparation in which we can record intracellularly from leg motor neurons during walking. In this single-leg preparation the middle leg of the animal steps in a vertical plane on a treadwheel. Stimulation of either abdomen or head reliably elicits fictive forward or backward motor activity, respectively, in the fixed and otherwise deafferented thorax-coxa joint. With a change of walking direction only thorax-coxa-joint motor neurons protractor and retractor changed their activity. The protractor switched from swing activity during forward to stance activity during backward walking, and the retractor from stance to swing. This phase switch was due to corresponding change of phasic synaptic inputs from inhibitory to excitatory and vice versa at specific phases of the step cycle. In addition to phasic synaptic input a tonic depolarization of the motor neurons was present. Analysis of changes in stepping velocity during stance showed only a significant correlation to flexor motor neuron activity, but not to that of retractor and depressor motor neurons during forward walking. These results show that different tasks in the stick insect walking system are generated by altering synaptic inputs to specific leg joint motor neurons only