-
PloS One 2016The important process of nutrient uptake in Escherichia coli, in many cases, involves transit of the nutrient through a class of beta-barrel proteins in the outer...
The important process of nutrient uptake in Escherichia coli, in many cases, involves transit of the nutrient through a class of beta-barrel proteins in the outer membrane known as TonB-dependent transporters (TBDTs) and requires interaction with the inner membrane protein TonB. Here we have imaged the mobility of the ferric enterobactin transporter FepA and TonB by tracking them in the membranes of live E. coli with single-molecule resolution at time-scales ranging from milliseconds to seconds. We employed simple simulations to model/analyze the lateral diffusion in the membranes of E.coli, to take into account both the highly curved geometry of the cell and artifactual effects expected due to finite exposure time imaging. We find that both molecules perform confined lateral diffusion in their respective membranes in the absence of ligand with FepA confined to a region [Formula: see text] μm in radius in the outer membrane and TonB confined to a region [Formula: see text] μm in radius in the inner membrane. The diffusion coefficient of these molecules on millisecond time-scales was estimated to be [Formula: see text] μm2/s and [Formula: see text] μm2/s for FepA and TonB, respectively, implying that each molecule is free to diffuse within its domain. Disruption of the inner membrane potential, deletion of ExbB/D from the inner membrane, presence of ligand or antibody to FepA and disruption of the MreB cytoskeleton was all found to further restrict the mobility of both molecules. Results are analyzed in terms of changes in confinement size and interactions between the two proteins.
Topics: Antibodies, Neutralizing; Bacterial Outer Membrane Proteins; Carrier Proteins; Cell Membrane; Cytoskeleton; Diffusion; Escherichia coli; Escherichia coli Proteins; Gene Deletion; Gene Expression Regulation, Bacterial; Membrane Proteins; Molecular Dynamics Simulation; Protein Binding; Protein Transport; Receptors, Cell Surface; Single Molecule Imaging; Time-Lapse Imaging
PubMed: 27935943
DOI: 10.1371/journal.pone.0160862 -
Ear, Nose, & Throat Journal Jul 2021Ototoxicity is the general name of cochlear and vestibular organ injury resulting from encountering various therapeutic agents and chemical substances. Cisplatin is...
Ototoxicity is the general name of cochlear and vestibular organ injury resulting from encountering various therapeutic agents and chemical substances. Cisplatin is commonly used in the treatment of many cancers. In this study, the efficacy of intratympanic steroids was compared for preventing cisplatin ototoxicity. In this study, 32 (64 ears) rats were used by separating into 4 groups. Cisplatin was administered intraperitoneally to the first group (n = 8). Methylprednisolone and then cisplatin were administered intratympanically to the second group (n = 8). On the third group (n = 8), dexamethasone and then cisplatin were administered intratympanically. To the fourth group (n = 8), 0.9% NaCl and then cisplatin were given intratympanically. Otoacoustic emission (OAE) measurements and auditory brainstem responses (ABRs) tests were performed on all groups before and 72 hours after the procedure. Pretreatment of ABR-IV values were 4.29 ± 0.19 milliseconds in group 2 and 4.27 ± 0.16 milliseconds in group 3, whereas posttreatment ABR-IV values were 4.95 ± 0.35 milliseconds in group 2 and 4.65 ± 0.26 milliseconds in group 3. The ABR-IV values were measured significantly shorter in the rats given dexamethasone and methylprednisolone, according to control and cisplatin groups ( < .001). Pretreatment of ABR I-IV interval values were 2.98 ± 0.34 milliseconds and 3.03 ± 0.42 milliseconds in group 1 and group 4, respectively, and ABR I-IV interval values in group 1 and group 4 posttreatment were 3.49 ± 0.39 milliseconds and 3.5 ± 0.39 milliseconds in group 1 and group 4, respectively. Auditory brainstem responses I-IV interval was significantly longer in the cisplatin and control group than in the rats given dexamethasone and methylprednisolone ( < .001). After cisplatin treatment, OAE amplitudes decreased significantly in group 1 and group 4 for all frequencies, while OAE values were protected in methylprednisolone and dexamethasone group ( < .001). In conclusion, it has been shown that both agents have protective effects on cisplatin ototoxicity, with dexamethasone slightly more than methylprednisolone.
Topics: Animals; Antineoplastic Agents; Cisplatin; Dexamethasone; Disease Models, Animal; Evoked Potentials, Auditory, Brain Stem; Glucocorticoids; Injection, Intratympanic; Methylprednisolone; Otoacoustic Emissions, Spontaneous; Ototoxicity; Protective Agents; Rats
PubMed: 31569969
DOI: 10.1177/0145561319874311 -
Optics Letters May 2020We present a parallel stimulated emission depletion (STED) nanoscope with no mechanical moving parts and sub-millisecond pixel dwell times, relying on electro-optical...
We present a parallel stimulated emission depletion (STED) nanoscope with no mechanical moving parts and sub-millisecond pixel dwell times, relying on electro-optical (EO) phase modulators. The nanoscope offers 1225-fold parallelization over single-doughnut-scanning STED and achieves a spatial resolution of 35 nm. We imaged immunostained nuclear pore complexes of zebrafish within their natural biological environment, demonstrating spatial and temporal resolutions of 56 nm and 0.2 s, respectively. Furthermore, we show parallel EO-STED sub-second imaging of microtubules inside living cells. Finally, we reveal the nanodomain organization of a eukaryotic initiation factor within the processing bodies of fixed cells. The potential of parallel EO-STED to offer microsecond pixel dwell times over large fields of view promises millisecond STED imaging.
Topics: Cell Line; Humans; Optical Imaging; Time Factors
PubMed: 32412448
DOI: 10.1364/OL.392822 -
Clinical Pharmacology in Drug... Sep 2018This study evaluated the effects of eluxadoline, a mixed μ-opioid receptor (OR) and κ-OR agonist and δ-OR antagonist, on cardiac repolarization. This... (Randomized Controlled Trial)
Randomized Controlled Trial
This study evaluated the effects of eluxadoline, a mixed μ-opioid receptor (OR) and κ-OR agonist and δ-OR antagonist, on cardiac repolarization. This evaluator-blinded, placebo- and positive-controlled, 4-period crossover study randomized healthy men and women to single oral doses of eluxadoline (therapeutic dose 100 mg or supratherapeutic dose 1000 mg), moxifloxacin 400 mg, or placebo. QT data were corrected using individual custom correction (QTcI). The primary endpoint was the change from baseline in QTcI intervals (ΔQTcI) between eluxadoline and placebo (ΔΔQTcI). An upper bound of the 95% confidence interval around ΔΔQTcI of 10 milliseconds was considered clinically significant. Concentration-QTc data were analyzed using a repeated-measures, mixed-effects linear model. Sixty-four volunteers were treated, and 58 completed the study. Assay sensitivity was demonstrated with moxifloxacin (noted by ΔΔQTcI of 11.94 milliseconds). The maximum ΔΔQTcI for eluxadoline 1000 mg was 4.10 milliseconds 1 hour postdose (1-sided 95% upper confidence bound, 5.81 milliseconds), and for eluxadoline 100 mg was 1.20 milliseconds at 0.5 hours postdose (1-sided 95% upper confidence bound, 2.91 milliseconds). Primary ΔΔQTcI results were confirmed using Fridericia's formula for QTc. Categorical, morphological, and concentration-QTc analyses were consistent with the primary and secondary findings. There were no significant gender effects on ΔΔQTcI values. The most common adverse events were contact dermatitis and nausea (12.5% each) and dizziness (10.9%); adverse events were more frequent in the eluxadoline 1000 mg group. In conclusion, eluxadoline, at therapeutic or supratherapeutic doses, did not significantly prolong QT intervals, and was safe and generally well tolerated in this study population.
Topics: Administration, Oral; Adult; Cross-Over Studies; Electrocardiography; Female; Gastrointestinal Agents; Healthy Volunteers; Heart; Heart Function Tests; Humans; Imidazoles; Male; Middle Aged; Moxifloxacin; Phenylalanine; Young Adult
PubMed: 29659201
DOI: 10.1002/cpdd.453 -
Biomolecular NMR Assignments Oct 2019β-Phosphoglucomutase (βPGM) is a magnesium-dependent phosphoryl transfer enzyme that catalyses the reversible isomerisation of β-glucose 1-phosphate and glucose...
β-Phosphoglucomutase (βPGM) is a magnesium-dependent phosphoryl transfer enzyme that catalyses the reversible isomerisation of β-glucose 1-phosphate and glucose 6-phosphate, via two phosphoryl transfer steps and a β-glucose 1,6-bisphosphate intermediate. Substrate-free βPGM is an essential component of the catalytic cycle and an understanding of its dynamics would present significant insights into βPGM functionality, and enzyme catalysed phosphoryl transfer in general. Previously, 30 residues around the active site of substrate-free βPGM were identified as undergoing extensive millisecond dynamics and were unassignable. Here we report H, N and C backbone resonance assignments of the P146A variant (βPGM) in its substrate-free form, where the K145-A146 peptide bond adopts a trans conformation in contrast to all crystal structures of βPGM, where the K145-P146 peptide bond is cis. In βPGM millisecond dynamics are suppressed for all but 17 residues, allowing 92% of backbone resonances to be assigned. Secondary structure predictions using TALOS-N reflect βPGM crystal structures, and a chemical shift comparison between substrate-free βPGM and βPGM confirms that the solution conformations are very similar, except for the D137-A147 loop. Hence, the isomerisation state of the 145-146 peptide bond has little effect on structure but the cis conformation triggers millisecond dynamics in the hinge (V12-T16), the nucleophile (D8) and residues that coordinate the transferring phosphate group (D8 and S114-S116), and the D137-A147 loop (V141-A142 and K145). These millisecond dynamics occur in addition to those for residues involved in coordinating the catalytic Mg ion and the L44-L53 loop responsible for substrate discrimination.
Topics: Lactococcus lactis; Mutant Proteins; Nuclear Magnetic Resonance, Biomolecular; Phosphoglucomutase
PubMed: 31396843
DOI: 10.1007/s12104-019-09904-y -
Journal of Athletic Training Apr 2018Scapular taping can offer clinical benefit to some patients with shoulder pain; however, the underlying mechanisms are unclear. Understanding these mechanisms may...
CONTEXT
Scapular taping can offer clinical benefit to some patients with shoulder pain; however, the underlying mechanisms are unclear. Understanding these mechanisms may guide the development of treatment strategies for managing neuromusculoskeletal shoulder conditions.
OBJECTIVE
To examine the mechanisms underpinning the benefits of scapular taping.
DESIGN
Descriptive laboratory study.
SETTING
University laboratory.
PATIENTS OR OTHER PARTICIPANTS
A total of 15 individuals (8 men, 7 women; age = 31.0 ± 12.4 years, height = 170.9 ± 7.6 cm, mass = 73.8 ± 14.4 kg) with no history of shoulder pain.
INTERVENTION(S)
Scapular taping.
MAIN OUTCOME MEASURE(S)
Surface electromyography (EMG) was used to assess the (1) magnitude and onset of contraction of the upper trapezius (UT), lower trapezius (LT), and serratus anterior relative to the contraction of the middle deltoid during active shoulder flexion and abduction and (2) corticomotor excitability (amplitude of motor-evoked potentials from transcranial magnetic stimulation) of these muscles at rest and during isometric abduction. Active shoulder-flexion and shoulder-abduction range of motion were also evaluated. All outcomes were measured before taping, immediately after taping, 24 hours after taping with the original tape on, and 24 hours after taping with the tape removed.
RESULTS
Onset of contractions occurred earlier immediately after taping than before taping during abduction for the UT (34.18 ± 118.91 milliseconds and 93.95 ± 106.33 milliseconds, respectively, after middle deltoid contraction; P = .02) and during flexion for the LT (110.02 ± 109.83 milliseconds and 5.94 ± 92.35 milliseconds, respectively, before middle deltoid contraction; P = .06). These changes were not maintained 24 hours after taping. Mean motor-evoked potential onset of the middle deltoid was earlier at 24 hours after taping (tape on = 7.20 ± 4.33 milliseconds) than before taping (8.71 ± 5.24 milliseconds, P = .008). We observed no differences in peak root mean square EMG activity or corticomotor excitability of the scapular muscles among any time frames.
CONCLUSIONS
Scapular taping was associated with the earlier onset of UT and LT contractions during shoulder abduction and flexion, respectively. Altered corticomotor excitability did not underpin earlier EMG onsets of activity after taping in this sample. Our findings suggested that the optimal time to engage in rehabilitative exercises to facilitate onset of trapezius contractions during shoulder movements may be immediately after tape application.
Topics: Adult; Deltoid Muscle; Electromyography; Female; Humans; Intermediate Back Muscles; Male; Motor Neurons; Muscle Contraction; Muscle, Skeletal; Range of Motion, Articular; Scapula; Shoulder; Superficial Back Muscles; Surgical Tape
PubMed: 29569944
DOI: 10.4085/1062-6050-68-17 -
Optometry and Vision Science : Official... Apr 2020Despite similar levels of visual acuity and contrast sensitivity reductions, simulated central vision impairment increased response times to a much greater extent in...
SIGNIFICANCE
Despite similar levels of visual acuity and contrast sensitivity reductions, simulated central vision impairment increased response times to a much greater extent in older than in younger participants.
PURPOSE
Driving is crucial for maintaining independence in older age, but age-related vision impairments and in-vehicle auditory distractions may impair driving safety. We investigated the effects of age, simulated central vision impairment, and auditory distraction on detection of pedestrian hazards.
METHODS
Thirty-two normally sighted participants (16 younger and 16 older) completed four highway drives in a simulator and pressed the horn whenever they saw a pedestrian. Pedestrians ran toward the road on a collision course with the approaching vehicle. Simulated central vision impairment was achieved by attaching diffusing filters to a pair of laboratory goggles, which reduced visual acuity to 20/80 and contrast sensitivity by 0.35 log units. For drives with distraction, subjects listened to an audiobook and repeated out loud target words.
RESULTS
Simulated central vision impairment had a greater effect on reaction times (660-millisecond increase) than age (350-millisecond increase) and distraction (160-millisecond increase) and had a greater effect on older than younger subjects (828- and 492-millisecond increase, respectively). Simulated central vision impairment decreased safe response rates from 94.7 to 78.3%. Distraction did not, however, affect safety because older subjects drove more slowly when distracted (but did not drive more slowly with vision impairment), suggesting that they might have perceived greater threat from the auditory distraction than the vision impairment.
CONCLUSIONS
Older participants drove more slowly in response to auditory distraction. However, neither older nor younger participants adapted their speed in response to simulated vision impairment, resulting in unsafe detections. These results underline the importance of evaluating safety of responses to hazards as well as reaction times in a paradigm that flexibly allows participants to modify their driving behaviors.
Topics: Accidents, Traffic; Adult; Aged; Aged, 80 and over; Aging; Attention; Auditory Perception; Automobile Driving; Computer Simulation; Contrast Sensitivity; Distracted Driving; Female; Humans; Male; Middle Aged; Psychomotor Performance; Reaction Time; Scotoma; Visual Acuity; Visual Fields; Young Adult
PubMed: 32304533
DOI: 10.1097/OPX.0000000000001501 -
The Journal of Physiology Nov 2005At least two functionally distinct transient outward K(+) current (I(to)) phenotypes can exist across the free wall of the left ventricle (LV). Based upon their... (Review)
Review
At least two functionally distinct transient outward K(+) current (I(to)) phenotypes can exist across the free wall of the left ventricle (LV). Based upon their voltage-dependent kinetics of recovery from inactivation, these two phenotypes are designated 'I(to,fast)' (recovery time constants on the order of tens of milliseconds) and 'I(to,slow)' (recovery time constants on the order of thousands of milliseconds). Depending upon species, either I(to,fast), I(to,slow) or both current phenotypes may be expressed in the LV free wall. The expression gradients of these two I(to) phenotypes across the LV free wall are typically heterogeneous and, depending upon species, may consist of functional phenotypic gradients of both I(to,fast) and I(to,slow) and/or density gradients of either phenotype. We review the present evidence (molecular, biophysical, electrophysiological and pharmacological) for Kv4.2/4.3 alpha subunits underlying LV I(to,fast) and Kv1.4 alpha subunits underlying LV I(to,slow) and speculate upon the potential roles of each of these currents in determining frequency-dependent action potential characteristics of LV subepicardial versus subendocardial myocytes in different species. We also review the possible functional implications of (i) ancillary subunits that regulate Kv1.4 and Kv4.2/4.3 (Kvbeta subunits, DPPs), (ii) KChIP2 isoforms, (iii) spider toxin-mediated block of Kv4.2/4.3 (Heteropoda toxins, phrixotoxins), and (iv) potential mechanisms of modulation of I(to,fast) and I(to,slow) by cellular redox state, [Ca(2)(+)](i) and kinase-mediated phosphorylation. I(to) phenotypic activation and state-dependent gating models and molecular structure-function relationships are also discussed.
Topics: Animals; Biophysics; Cell Membrane; Heart Ventricles; Humans; Ion Channel Gating; Mammals; Models, Biological; Molecular Biology; Phenotype; Potassium; Shal Potassium Channels; Ventricular Function
PubMed: 15831535
DOI: 10.1113/jphysiol.2005.086223 -
Physical Chemistry Chemical Physics :... Mar 2013For the past two decades, protein folding experiments have been speeding up from the second or millisecond time scale to the microsecond time scale, and full-atom...
For the past two decades, protein folding experiments have been speeding up from the second or millisecond time scale to the microsecond time scale, and full-atom simulations have been extended from the nanosecond to the microsecond and even millisecond time scale. Where the two meet, it is now possible to compare results directly, allowing force fields to be validated and refined, and allowing experimental data to be interpreted in atomistic detail. In this perspective we compare recent experiments and simulations on the microsecond time scale, pointing out the progress that has been made in determining native structures from physics-based simulations, refining experiments and simulations to provide more quantitative underlying mechanisms, and tackling the problems of multiple reaction coordinates, downhill folding, and complex underlying structure of unfolded or misfolded states.
Topics: Computer Simulation; Protein Folding; Thermodynamics
PubMed: 23361200
DOI: 10.1039/c3cp43992e -
NeuroImage Sep 2021The cerebellum is involved in predicting the sensory feedback resulting from movements and sensations, but little is known about the precise timing of these predictions...
The cerebellum is involved in predicting the sensory feedback resulting from movements and sensations, but little is known about the precise timing of these predictions due to the scarcity of time-sensitive cerebellar neuroimaging studies. We here, using magnetoencephalography, investigated the hypothesis that one function of the cerebellum is to predict with millisecond precision when rhythmic stimuli are expected to impinge on sensory receptors. This revealed that omissions following regular trains of stimulation showed higher cerebellar power in the beta band (14-30 Hz) than those following irregular trains of stimulation, within milliseconds of when the omitted stimulus should have appeared. We also found evidence of cerebellar theta band (4-7 Hz) activity encoding the rhythm of new sequences of stimulation. Our results also strongly suggest that the putamen and the thalamus mirror the cerebellum in showing higher beta band power when omissions followed regular trains of stimulation compared to when they followed irregular trains of stimulation. We interpret this as the cerebellum functioning as a clock that precisely encodes and predicts upcoming stimulation, perhaps in tandem with the putamen and thalamus. Relative to less predictable stimuli, perfectly predictable stimuli induce greater cerebellar power. This implies that the cerebellum entrains to rhythmic stimuli for the purpose of detecting any deviations from that rhythm.
Topics: Adolescent; Adult; Attention; Cerebellum; Feedback, Sensory; Female; Humans; Magnetoencephalography; Male; Physical Stimulation; Touch; Touch Perception; Young Adult
PubMed: 34089874
DOI: 10.1016/j.neuroimage.2021.118202