Conductance of porous media depends on external electric fields

In obstacle-filled media, such as extracellular or intracellular lumen of brain tissue, effective ion diffusion permeability is a key determinant of electrogenic reactions. Although this diffusion permeability is thought to depend entirely on structural features of the medium, such as porosity and tortuosity, brain tissue shows prominent non-ohmic properties, the origins of which remain poorly understood. Here, we explore Monte Carlo simulations of ion diffusion in a space filled with overlapping spheres, to predict that diffusion permeability of such media decreases with stronger external electric fields. This dependence increases with lower medium porosity while decreasing with radial (2D or 3D) compared to homogenous (1D) fields. We test our predictions empirically in an electrolyte chamber filled with microscopic glass spheres and find good correspondence with our predictions. A theoretical insight relates this phenomenon to a disproportionately increased dwell time of diffusing ions at potential barriers (or traps) representing geometric obstacles, when the field strength increases. The dependence of medium ion-diffusion permeability on electric field could be important for understanding conductivity properties of porous materials, in particular for the accurate interpretation of electric activity recordings in brain tissue

Buffering by Transporters Can Spare Geometric Hindrance in Controlling Glutamate Escape

The surface of astrocyte processes that often surround excitatory synapses is packed with high-affinity glutamate transporters, largely preventing extrasynaptic glutamate escape. The shape and prevalence of perisynaptic astroglia vary among brain regions, in some cases providing a complete isolation of synaptic connections from the surrounding tissue. The perception has been that the geometry of perisynaptic environment is therefore essential to preventing extrasynaptic glutamate escape. To understand to what degree this notion holds, we modelled brain neuropil as a space filled with a scatter of randomly sized, overlapping spheres representing randomly shaped cellular elements and intercellular lumen. Simulating release and diffusion of glutamate molecules inside the interstitial gaps in this medium showed that high-affinity transporters would efficiently constrain extrasynaptic spread of glutamate even when diffusion passages are relatively open. We thus estimate that, in the hippocampal or cerebellar neuropil, the bulk of glutamate released by a synaptic vesicle is rapidly bound by transporters (or high-affinity target receptors) mainly in close proximity of the synaptic cleft, whether or not certain physiological or pathological events change local tissue geometry

ARACHNE: A neural-neuroglial network builder with remotely controlled parallel computing

Creating and running realistic models of neural networks has hitherto been a task for computing professionals rather than experimental neuroscientists. This is mainly because such networks usually engage substantial computational resources, the handling of which requires specific programing skills. Here we put forward a newly developed simulation environment ARACHNE: it enables an investigator to build and explore cellular networks of arbitrary biophysical and architectural complexity using the logic of NEURON and a simple interface on a local computer or a mobile device. The interface can control, through the internet, an optimized computational kernel installed on a remote computer cluster. ARACHNE can combine neuronal (wired) and astroglial (extracellular volume-transmission driven) network types and adopt realistic cell models from the NEURON library. The program and documentation (current version) are available at GitHub repository https://github.com/LeonidSavtchenko/Arachne under the MIT License (MIT)

Regenerating plants from in vitro culture of Erigeron breviscapus leaves

A protocol to efficiently achieve plant regeneration from leaf explants of Erigeron breviscapus (Compositae) has been developed. Leaf explants produced calli on Murashige and Skoog’s (1962) basal medium (MS) supplemented with 6-benzylaminopurine (BAP) (0.4 mM) and 2,4-dichlorophenoxyacetic acid (2,4-D) (0.4-22.6 mM) under a 16-h photoperiod. Direct adventitious shoots were induced from leaf explants on MS medium containing BAP (22.2 mM) and IAA (5.7 mM) under the light treatment. The effect of the dark incubation on shoot regeneration from leaves indicated that 15 days of darkness permitted a higher regeneration frequency (82.6%) on the medium supplemented with BAP (4.4 mM) and indole-3- acetic acid (IAA) (0.6 mM). Regenerated shoots were rooted on MS medium with or without naphthaleneacetic acid (NAA). Plantlets were cultivatable in the greenhouse after acclimatization

Inhibitory effects of (-)-epigallocatechin-3-gallate on melanogenesis in ultraviolet A-induced B16 murine melanoma cell

Purpose: To investigate the anti-melanogenesis effect of green tea compound, (-)-epigallocatechin-3- gallate (EGCG), on B16 murine melanoma cell irradiated by ultraviolet A (UVA) in the search for natural skin-lightening alternative agents.Methods: B16 murine melanoma cells by UVA (9.0 J/cm2) for 0 to 32 min and then incubated in Dulbecco's Modified Eagle's Medium (DMEM) with EGCG (0-200 μg/mL) for 2 days. Cell viability was determined by MTT method and cell protein was quantified using a PA102 Bradford protein assay kit. Activity of tyrosinase (TRY) was determined based on the oxidation rate of 3,4-dihydroxy phenylalanine (DOPA). The ultra-structure of the melanosomes was observed by transmission electron microscopy (TEM).Results: TRY activity and melanin concentration were increased to 146.70 ± 10.28 % (p < 0.05) and 157.06 ± 6.37 % (p < 0.05), respectively, by 9.0 J/cm2 UVA irradiation for 8 min, compared to blank control without UV A and EGCG. EGCG inhibited the UV A induced increase in TRY activity and melanin level, and the optimum concentration of EGCG was 25 μg/mL. TRY activity and melanin concentration were decreased to 64.71 ± 4.41 (p < 0.05) and 86.24 ± 5.15 % (p < 0.05), respectively, compared to blank (control) which was neither treated by UVA nor by EGCG. TEM showed that UVA induced the formation of melanosomes while EGCG inhibited UVA-induced melanosome maturation.Conclusion: EGCG inhibits UVA-induced melanogenesis via suppression of TRY activity and melanosome maturation and is thus a potential alternative to melanogenesis inhibitor.Keywords: Green tea, Catechins, Melanin, Melanosome, Tyrosinase, Cell proliferatio

Randomized controlled trial of traditional Chinese medicine (acupuncture and Tuina) in cerebral palsy: Part 1 - Any increase in seizure in integrated acupuncture and rehabilitation group versus rehabilitation group?

Objective: The objective of this study was to observe for any change in baseline seizure frequency with acupuncture in children with cerebral palsy. Methods: A randomized controlled study was conducted: Group I consisted of integrated acupuncture, tuina, and rehabilitation (physiotherapy, occupational therapy, and hydrotherapy) for 12 weeks; and Group II consisted of rehabilitation (physiotherapy, occupational therapy, and hydrotherapy) for 12 weeks. After a washout period of 4 weeks, Group II then received acupuncture and tuina for 12 weeks. Each subject received 5 daily acupuncture sessions per week for 12 weeks (total = 60 sessions). All children were assessed for any change in seizure frequency during treatment. Results: One hundred and sixteen (116) children were recruited and randomized into Group I (N = 58) and Group II (N = 58). Thirty-three (33) children withdrew (9 from Group I and 24 from Group II). Of the remaining 83 children, Group I consisted of 49 and Group II of 34 children. For baseline, 5 children (6%; 5/83) had seizures. During phase 1 (12 weeks) of integrative treatment and subsequent 4-week follow-up, 3 children in Group I had seizures. Among those 3 children with seizures, 1 child with prior history of recurrent febrile seizure had 3 more recurrent febrile seizures during acupuncture treatment and 2 children without any prior history of seizures had new-onset seizures (1 with 3 recurrent febrile seizures and 1 with afebrile seizure). For Group I, 2 children with epilepsy had no increase in seizure frequency during acupuncture treatment. For Group II during the phase 2 acupuncture period, none had increase in seizure frequency. In both groups, 4 of 5 children (80%; 2 in Group I and 2 in Group II) with seizures had no increase in seizure frequency during acupuncture treatment and follow-up. Conclusions: The risk of increasing seizure is not increased with acupuncture treatment for cerebral palsy. © 2008 Mary Ann Liebert, Inc.published_or_final_versio

The economic burden of influenza-associated outpatient visits and hospitalizations in China: a retrospective survey

published_or_final_versio

Disentangling astroglial physiology with a realistic cell model in silico

Electrically non-excitable astroglia take up neurotransmitters, buffer extracellular K+ and generate Ca2+ signals that release molecular regulators of neural circuitry. The underlying machinery remains enigmatic, mainly because the sponge-like astrocyte morphology has been difficult to access experimentally or explore theoretically. Here, we systematically incorporate multi-scale, tri-dimensional astroglial architecture into a realistic multi-compartmental cell model, which we constrain by empirical tests and integrate into the NEURON computational biophysical environment. This approach is implemented as a flexible astrocyte-model builder ASTRO. As a proof-of-concept, we explore an in silico astrocyte to evaluate basic cell physiology features inaccessible experimentally. Our simulations suggest that currents generated by glutamate transporters or K+ channels have negligible distant effects on membrane voltage and that individual astrocytes can successfully handle extracellular K+ hotspots. We show how intracellular Ca2+ buffers affect Ca2+ waves and why the classical Ca2+ sparks-and-puffs mechanism is theoretically compatible with common readouts of astroglial Ca2+ imaging

Design and implementation of deformation algorithms for computer assisted orthopedic surgery: application to virtual implant database and preliminary results

Fractures around the joints are more common cases in routine trauma surgery where the surgeons have to bend the osteosynthesis plates to fit geometrical boundaries of the specific patient. This is a complicated, time consuming, and technically demanding procedure. The average time for bending a single plate requires as long as twenty minutes. This paper presents the first trial to design and implement the deformation algorithms for computer assisted orthopedic surgery system to assist surgeons in this procedure. Our preliminary results are presented