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- Myoelectric stimulation on peroneal muscles with electrodes of the muscle belly size attached to the upper shank gives the best effect in resisting simulated ankle sprain motion. [Journal Article, Research Support, Non-U.S. Gov't]
- J Biomech 2013 Apr 5; 46(6):1088-91.
Ankle sprain is a common sports related injury that may be caused by incorrect positioning of the foot prior to and at initial contact during landing from a jump or gait. Furthermore a delayed reaction of the peroneal muscle may also contribute to the injury mechanism. A recent study demonstrated that myoelectric stimulation of the peroneal muscles within 15 ms of a simulated inversion event would significantly resist an ankle spraining motion. This study further investigated its effect with three different electrode sizes and three different lateral shank attachment positions. Twelve male subjects with healthy ankles performed simulated ankle supination spraining motion on a pair of mechanical sprain simulators. A pair of electrodes of one of the three sizes (large, medium, small) was attached to one of the three positions (upper 1/4, middle, lower 1/4) along the lateral shank to deliver an electrical signal of 130 V for 0.5s when the sprain simulator started. Ankle kinematics data were collected by a tri-axial gyroscope motion sensor and the peak inward heel tilting velocity was obtained to represent the effect in resisting the simulated ankle spraining motion. Repeated measures one-way analysis of variance was performed and showed a significant drop from 273.3 (control, no stimulation) to 215.8 deg/s (21%) when small electrodes were attached to the upper 1/4 position. Decrease was found in all other conditions but the drops (11-18%) were not statistically significant. The small electrodes used in this study fitted the width of the peroneal muscle belly at the upper 1/4 position, so the electrical current may have well flowed to the motor points of the muscles to initiate quick contraction.
- Plasmoid and Kelvin-Helmholtz instabilities in Sweet-Parker current sheets. [Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.]
- Phys Rev E Stat Nonlin Soft Matter Phys 2013 Jan; 87(1):013102.
A two-dimensional (2D) linear theory of the instability of Sweet-Parker (SP) current sheets is developed in the framework of reduced magnetohydrodynamics. A local analysis is performed taking into account the dependence of a generic equilibrium profile on the outflow coordinate. The plasmoid instability [Loureiro et al., Phys. Plasmas 14, 100703 (2007)] is recovered, i.e., current sheets are unstable to the formation of a large-wave-number chain of plasmoids (k(max)L(CS)~S(3/8), where k(max) is the wave number of fastest growing mode, S=L(CS)V(A)/η is the Lundquist number, L(CS) is the length of the sheet, V(A) is the Alfvén speed, and η is the plasma resistivity), which grows super Alfvénically fast (γ(max)τ(A)~S(1/4), where γ(max) is the maximum growth rate, and τ(A)=L(CS)/V(A)). For typical background profiles, the growth rate and the wave number are found to increase in the outflow direction. This is due to the presence of another mode, the Kelvin-Helmholtz (KH) instability, which is triggered at the periphery of the layer, where the outflow velocity exceeds the Alfvén speed associated with the upstream magnetic field. The KH instability grows even faster than the plasmoid instability γ(max)τ(A)~k(max)L(CS)~S(1/2). The effect of viscosity (ν) on the plasmoid instability is also addressed. In the limit of large magnetic Prandtl numbers Pm=ν/η, it is found that γ(max)~S(1/4)Pm(-5/8) and k(max)L(CS)~S(3/8)Pm(-3/16), leading to the prediction that the critical Lundquist number for plasmoid instability in the Pm>1 regime is S(crit)~10(4)Pm(1/2). These results are verified via direct numerical simulation of the linearized equations, using an analytical 2D SP equilibrium solution.
- Nature of halogen bonding. A study based on the topological analysis of the Laplacian of the electron charge density and an energy decomposition analysis. [Journal Article]
- J Mol Model 2013 May; 19(5):2035-41.
In this work we investigate the nature of the Cl···N interactions in complexes formed between substituted ammonium [NHn(X3-n) (with n = 0, 1, 2, 3 and X = -CH3, -F] as Lewis bases and F-Cl molecule as Lewis acid. They have been chosen as a study case due to the wide range of variation of their binding energies, BEs. Møller-Plesset [MP2/6-311++G(2d,2p)] calculations show that the BEs for this set of complexes lie in the range from 1.27 kcal/mol (in F-Cl···NF3) to 27.62 kcal/mol [in F-Cl···N(CH3)3]. The intermolecular distribution of the electronic charge density and their L(r) = -¼∇(2)ρ(r) function have been investigated within the framework of the atoms in molecules (AIM) theory. The intermolecular interaction energy decomposition has also been analyzed using the reduced variational space (RVS) method. The topological analysis of the L(r) function reveals that the local topological properties measured at the (3,+1) critical point [in L(r) topology] are good descriptors of the strength of the halogen bonding interactions. The results obtained from energy decomposition analysis indicate that electrostatic interactions play a key role in these halogen bonding interactions. These results allow us to establish that, when the halogen atom is bonded to a group with high electron-withdrawing capacity, the electrostatic interaction between the electron cloud of the Lewis base and the halogen atom unprotected nucleus of the Lewis acid produces the formation and determines the geometry of the halogen bonded complexes. In addition, a good linear relationship has been established between: the natural logarithm of the BEs and the electrostatic interaction energy between electron charge distribution of N atom and nucleus of Cl atom, denoted as V e-n(N,Cl) within the AIM theory.
- Comparison of carfentanil-xylazine and thiafentanil-medetomidine in electroejaculation of captive gaur (Bos gaurus). [Clinical Trial, Journal Article]
- J Zoo Wildl Med 2011 Sep; 42(3):430-6.
Carfentanil citrate and thiafentanil oxalate have been used successfully to immobilize captive and free-ranging ungulates. The objective of this study was to compare the efficacy and certain physiologic parameters of protocols by using the 2 opioids in gaur (Bos gaurus). Eight adult gaur bulls were immobilized for electroejaculation at Omaha's Henry Doorly Zoo (Omaha, Nebraska, USA). All the animals were immobilized twice, by using each of the following protocols one time: 10 mg carfentanil combined with 100 mg xylazine (CX), reversed with 1,000 mg naltrexone and 24 mg yohimbine; and 12 mg thiafentanil combined with 20 mg medetomidine (TM), reversed with 120 mg naltrexone and 100 mg atipamezole. Immobilization drugs were delivered intramuscularly into the shoulder area via pole syringe. Electroejaculation was carried out by a standardized protocol to duplicate procedural stimulation on each animal. Induction and recovery times, initial rectal temperature, heart rate, respiratory rate, anesthetic depth, oxygen saturation, indirect blood pressure, and arterial blood gases were recorded at the time of initial handling, before ejaculation, and after ejaculation. Antagonists were administered 1/4 i.v. and 3/4 s.q. Both protocols require a small volume of drug for a large ungulate, provide smooth induction, and adequate anesthesia. Both protocols produced a significant hypoxemia, although the animals on CX showed slightly better blood gas values (based on lower partial pressure of carbon dioxide) and numerically lower blood pressure values. Animals on TM had better muscle relaxation and smoother recoveries, with no renarcotization noted. The results of the present study indicate the TM and CX protocols used for immobilizing gaur result in similar quality ejaculates that can be used for fertility examination as well as for assisted reproduction such as artificial insemination. Additional immobilizations need to take place to further compare these 2 combinations in this species.
- A ratiometric fluorescent chemosensor for iron: discrimination of Fe2+ and Fe3+ and living cell application. [Journal Article, Research Support, Non-U.S. Gov't]
- Analyst 2012 Jul 21; 137(14):3335-42.
A newly designed probe, 6-thiophen-2-yl-5,6-dihydrobenzo[4,5]imidazo-[1,2-c] quinazoline (HL(1)) behaves as a highly selective ratiometric fluorescent sensor for Fe(2+) at pH 4.0-5.0 and Fe(3+) at pH 6.5-8.0 in acetonitrile-HEPES buffer (1/4) (v/v) medium. A decrease in fluorescence at 412 nm and increase in fluorescence at 472 nm with an isoemissive point at 436 nm with the addition of Fe(2+) salt solution is due to the formation of mononuclear Fe(2+) complex [Fe(II)(HL)(ClO(4))(2)(CH(3)CN)(2)] (1) in acetonitrile-HEPES buffer (100 mM, 1/4, v/v) at pH 4.5 and a decrease in fluorescence at 412 nm and increase in fluorescence at 482 nm with an isoemissive point at 445 nm during titration by Fe(3+) salt due to the formation of binary Fe(3+) complex, [Fe(III)(L)(2)(ClO(4))(H(2)O)] (2) with co-solvent at biological pH 7.4 have been established. Binding constants (K(a)) in the solution state were calculated to be 3.88 × 10(5) M(-1) for Fe(2+) and 0.21 × 10(3) M(-1/2) for Fe(3+) and ratiometric detection limits for Fe(2+) and Fe(3+) were found to be 2.0 μM and 3.5 μM, respectively. The probe is a "naked eye" chemosensor for two states of iron. Theoretical calculations were studied to establish the configurations of probe-iron complexes. The sensor is efficient for detecting Fe(3+)in vitro by developing a good image of the biological organelles.
- Acute effects of methiocarb on oxidative damage and the protective effects of vitamin E and taurine in the liver and kidney of Wistar rats. [Journal Article, Research Support, Non-U.S. Gov't]
- Toxicol Ind Health 2013 Feb; 29(1):60-71.
Methiocarb (MC) is a widely used carbamate pesticide in agriculture and health programs. Although the main molecular mechanism of carbamate toxicity involves acetylcholinesterase inhibition, studies have also implicated the induction of oxidative stress. Therefore, the present study was aimed to evaluate the effect of acute MC exposure on lipid peroxidation, antioxidant defense systems, histological changes in Wistar rats and the protective effect of pretreatment with vitamin E and taurine. A total of 48 rats were randomly divided into six groups. Rats in group I were given corn oil, while those in group III were dosed with vitamin E (100 mg/kg body weight (b.w.)) and in group V were dosed with taurine (50 mg/kg b.w.). Rats in group II were administered with MC only (25 mg/kg b.w., 1/4 of median lethal dose (LD(50))), while those in groups IV and VI were pretreated with vitamin E (100 mg/kg b.w.) and taurine (50 mg/kg b.w.) for 20 days, respectively, and then exposed to MC (25 mg/kg b.w.). The rats administered with MC showed significant increase in the levels of malondialdehyde in the liver and kidney as an index of lipid peroxidation. Levels of glutathione and activities of superoxide dismutase, catalase and glutathione peroxidase were significantly increased, while activity of glutathione reductase remained unchanged in both the tissues after MC treatment. Mild degenerative histological changes were observed in liver tissue, while the changes in kidney tissue were more severe then liver after MC treatment. Pretreatment with vitamin E and taurine resulted in a significant decrease in the lipid peroxidation and alleviating effects on antioxidant defense systems in both the tissues, while protective effects on the histological changes were shown only in kidney when compared with liver. In conclusion, the study has demonstrated that the acute MC exposure in Wistar rats caused oxidative damage on liver and kidney, which were partly ameliorated by the pretreatment of vitamin E and taurine.
- Micropropagation, antinociceptive and antioxidant activities of extracts of Verbena litoralis Kunth (Verbenaceae). [JOURNAL ARTICLE]
- An Acad Bras Cienc 2012 Feb 24.
This work describes an efficient micropropagation protocol for Verbena litoralis and the study of the antinociceptive and antioxidant activities in extracts of this species. For the establishment in vitro, surface-sterilization procedures and PVPP showed high efficiency in fungal-bacterial contamination and phenol oxidation controls. Nodal segments cultivation in MS medium supplemented with 6-benzyladenine (7.5 μM)/α-naphthaleneacetic acid (NAA; 0.005 μM) induced multiple shoots. Elongated shoots were rooted with IAA (0.2 μM). Acclimatization rates were elevated and the plants showed the typical features of this species. The hexanic fraction (HF) of powdered leaves presented a radical scavenging activity with IC50 = 169.3 Î¼g mL-1. HF showed a non-dose dependent analgesic activity in the writhing test; its antinociceptive activity in the hot plate test was restricted to 500 mg kg-1, which is the highest dose. The results of this study showed the potential of tissue culture on conservation and large scale multiplication and confirmed the traditional folk medicine use of V. litoralis.
- Mechanics of soft composites of rods in elastic gels. [Journal Article, Research Support, Non-U.S. Gov't]
- Phys Rev E Stat Nonlin Soft Matter Phys 2011 Dec; 84(6 Pt 1):061906.
We report detailed theoretical investigations of the micromechanics and bulk elastic properties of composites consisting of randomly distributed stiff fibers embedded in an elastic matrix in two and three dimensions. Recent experiments [V. Pelletier, N. Gal, P. Fournier, and M. L. Kilfoil, Phys. Rev. Lett. 102, 188303 (2009)] have suggested that the inclusion of stiff microtubules in a softer, nearly incompressible biopolymer matrix can lead to emergent compressibility. This can be understood in terms of the enhancement of the compressibility of the composite relative to its shear compliance as a result of the addition of stiff rodlike inclusions. We show that the Poisson's ratio ν of such a composite evolves with increasing rod density toward a particular value, or fixed point, independent of the material properties of the matrix, as long as it has a finite initial compressibility. This fixed point is ν = 1/4 in three dimensions and ν = 1/3 in two dimensions. Our results suggest an important role for stiff filaments such as microtubules and stress fibers in cell mechanics. At the same time, our work has a wider elasticity context, with potential applications to composite elastic media with a wide separation of scales in stiffness of its constituents such as carbon nanotube-polymer composites, which have been shown to have highly tunable mechanics.
- Atropine-sensitive hippocampal θ oscillations are mediated by Cav2.3 R-type Ca²⁺ channels. [Journal Article, Research Support, Non-U.S. Gov't]
- Neuroscience 2012 Mar 15.:125-39.
Hippocampal theta oscillations are key elements in numerous behavioral and cognitive processes. Based on the dualistic theory of theta oscillations, one can differentiate between atropine-sensitive and atropine-insensitive theta subtypes. Urethane-induced atropine-sensitive theta oscillations are driven by muscarinic signal transduction pathways through G protein q/11 alpha subunit (Gα(q/11)), phospholipase β( ¼) (PLCβ( ¼), inositol trisphosphate (InsP₃), diacylglycerole (DAG), and protein kinase C (PKC). Recent findings illustrate that Ca(v)2.3 Ca²⁺ channels are important targets of muscarinic signaling in the hippocampus mediating plateau potential generation, epileptiform burst activity, and complex rhythm generation in the septohippocampal network. To investigate the physiological implications of Ca(v)2.3 Ca²⁺ channels in hippocampal theta oscillations we performed radiotelemetric intrahippocampal (cornu ammonis (CA1)) recordings in urethane (800 mg/kg, i.p.) and atropine (50 mg/kg, i.p.) treated Ca(v)2.3⁺/⁺ and Ca(v)2.3⁻/⁻ mice followed by wavelet analysis of EEG data. Our results demonstrate that Ca(v)2.3 ablation, unlike PLCβ₁ deletion, does not result in complete abolishment of urethane-induced theta oscillations and that both mean and total theta duration is not significantly inhibited by subsequent atropine treatment, indicating that Ca(v)2.3 Ca²⁺ channels are important mediators of atropine-sensitive theta. Although theta frequency remained unchanged between both genotypes, the temporal characteristics of theta distribution, that is, theta architecture were significantly affected by the loss of Ca(v)2.3 Ca²⁺ channels. Our data suggest, for the first time, that Ca(v)2.3 voltage-gated Ca²⁺ channels (VGCC) are an important factor in septohippocampal synchronization associated with theta oscillation.
- Scaling of brain metabolism and blood flow in relation to capillary and neural scaling. [Journal Article, Research Support, Non-U.S. Gov't]
- PLoS One 2011; 6(10):e26709.
Brain is one of the most energy demanding organs in mammals, and its total metabolic rate scales with brain volume raised to a power of around 5/6. This value is significantly higher than the more common exponent 3/4 relating whole body resting metabolism with body mass and several other physiological variables in animals and plants. This article investigates the reasons for brain allometric distinction on a level of its microvessels. Based on collected empirical data it is found that regional cerebral blood flow CBF across gray matter scales with cortical volume V as CBF ~ V(-1/6), brain capillary diameter increases as V(1/12), and density of capillary length decreases as V(-1/6). It is predicted that velocity of capillary blood is almost invariant (~V(ε)), capillary transit time scales as V(1/6), capillary length increases as V(1/6+ε), and capillary number as V(2/3-ε), where ε is typically a small correction for medium and large brains, due to blood viscosity dependence on capillary radius. It is shown that the amount of capillary length and blood flow per cortical neuron are essentially conserved across mammals. These results indicate that geometry and dynamics of global neuro-vascular coupling have a proportionate character. Moreover, cerebral metabolic, hemodynamic, and microvascular variables scale with allometric exponents that are simple multiples of 1/6, rather than 1/4, which suggests that brain metabolism is more similar to the metabolism of aerobic than resting body. Relation of these findings to brain functional imaging studies involving the link between cerebral metabolism and blood flow is also discussed.