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Journal of Athletic Training 2012Head-first sports-induced impacts cause cervical fractures and dislocations and spinal cord lesions. In previous biomechanical studies, researchers have vertically...
CONTEXT
Head-first sports-induced impacts cause cervical fractures and dislocations and spinal cord lesions. In previous biomechanical studies, researchers have vertically dropped human cadavers, head-neck specimens, or surrogate models in inverted postures.
OBJECTIVE
To develop a cadaveric neck model to simulate horizontally aligned, head-first impacts with a straightened neck and to use the model to investigate biomechanical responses and failure mechanisms.
DESIGN
Descriptive laboratory study.
SETTING
Biomechanics research laboratory.
PATIENTS OR OTHER PARTICIPANTS
Five human cadaveric cervical spine specimens.
INTERVENTION(S)
The model consisted of the neck specimen mounted horizontally to a torso-equivalent mass on a sled and carrying a surrogate head. Head-first impacts were simulated at 4.1 m/s into a padded, deformable barrier.
MAIN OUTCOME MEASURE(S)
Time-history responses were determined for head and neck loads, accelerations, and motions. Average occurrence times of the compression force peaks at the impact barrier, occipital condyles, and neck were compared.
RESULTS
The first local compression force peaks at the impact barrier (3070.0 ± 168.0 N at 18.8 milliseconds), occipital condyles (2868.1 ± 732.4 N at 19.6 milliseconds), and neck (2884.6 ± 910.7 N at 25.0 milliseconds) occurred earlier than all global compression peaks, which reached 7531.6 N in the neck at 46.6 milliseconds (P < .001). Average peak head motions relative to the torso were 6.0 cm in compression, 2.4 cm in posterior shear, and 6.4° in flexion. Neck compression fractures included occipital condyle, atlas, odontoid, and subaxial comminuted burst and facet fractures.
CONCLUSIONS
Neck injuries due to excessive axial compression occurred within 20 milliseconds of impact and were caused by abrupt deceleration of the head and continued forward torso momentum before simultaneous rebound of the head and torso. Improved understanding of neck injury mechanisms during sports-induced impacts will increase clinical awareness and immediate care and ultimately lead to improved protective equipment, reducing the frequency and severity of neck injuries and their associated societal costs.
Topics: Acceleration; Athletic Injuries; Biomechanical Phenomena; Cadaver; Cervical Atlas; Cervical Vertebrae; Fractures, Bone; Head; Humans; Male; Motion; Neck; Neck Injuries; Spinal Fractures; Sports
PubMed: 23068585
DOI: 10.4085/1062-6050-47.4.06 -
Frontiers in Molecular Biosciences 2022Advances in single particle cryo-EM data collection and processing have seen a significant rise in its use. However, the influences of the environment generated through...
Advances in single particle cryo-EM data collection and processing have seen a significant rise in its use. However, the influences of the environment generated through grid preparation, by for example interactions of proteins with the air-water interface are poorly understood and can be a major hurdle in structure determination by cryo-EM. Initial interactions of proteins with the air-water interface occur quickly and proteins can adopt preferred orientation or partially unfold within hundreds of milliseconds. It has also been shown previously that thin-film layers create hydroxyl radicals. To investigate the potential this might have in cryo-EM sample preparation, we studied two proteins, HSPD1, and beta-galactosidase, and show that cysteine residues are modified in a time-dependent manner. In the case of both HSPD1 and beta-galactosidase, this putative oxidation is linked to partial protein unfolding, as well as more subtle structural changes. We show these modifications can be alleviated through increasing the speed of grid preparation, the addition of DTT, or by sequestering away from the AWI using continuous support films. We speculate that the modification is oxidation by reactive oxygen species which are formed and act at the air-water interface. Finally, we show grid preparation on a millisecond timescale outruns cysteine modification, showing that the reaction timescale is in the range of 100s to 1,000s milliseconds and offering an alternative approach to prevent spontaneous cysteine modification and its consequences during cryo-EM grid preparation.
PubMed: 35992264
DOI: 10.3389/fmolb.2022.945772 -
Journal of Veterinary Internal Medicine 1998Signal-averaged electrocardiograms (SAECGs) were performed on nonsedated normal dogs in left-lateral recumbency. Following signal averaging, both time-domain and...
Signal-averaged electrocardiograms (SAECGs) were performed on nonsedated normal dogs in left-lateral recumbency. Following signal averaging, both time-domain and 3-dimensional frequency-domain analyses were performed. For time-domain analysis, the high-frequency QRS (HFQRS) duration, duration of the terminal QRS complex less than 40 microV (LAS40), and root mean square (RMS) voltages (microV) of the terminal 40 milliseconds (RMS40) and 30 milliseconds of the QRS complex were calculated. For frequency-domain analysis, correlation ratios were calculated for 30-, 40-, 50-, and 60-millisecond segment lengths begun 10, 15, or 20 milliseconds before the end of the QRS complex. Spectro-temporal mapping was also performed. All of the parameters of the SAECGs analyzed in the time domain were associated with each other. LAS40 and RMS voltages regressed significantly (P < .0000) on the HFQRS duration. Ninety-five percent of the HFQRSs were 55-75 milliseconds, 95% of the LAS40s were 9-26 milliseconds, and 95% of the RMS40 voltages were 177-444 microV. None of the SAECGs contained evidence of ventricular late potentials. Spectro-temporal maps were similar in each dog when the same segment lengths and starting points were compared. No evidence of ventricular late potentials was observed. Correlation ratios were lower when windowed segments included 15 or 20 milliseconds (versus 10 milliseconds) of the terminal QRS complex. When only 10 milliseconds of the terminal QRS complex were included in windowed segments, the mean correlation ratios for 30- and 40-millisecond segment lengths were > 0.8 and > 0.61 in 67% of all analyses, respectively.
Topics: Animals; Cardiomyopathies; Data Interpretation, Statistical; Death, Sudden; Dog Diseases; Dogs; Electrocardiography; Reference Values; Tachycardia, Ventricular; Ventricular Function, Left
PubMed: 9773412
DOI: 10.1111/j.1939-1676.1998.tb02135.x -
Nature Communications May 2023Our knowledge about the fine structure of lightning processes at Jupiter was substantially limited by the time resolution of previous measurements. Recent observations...
Our knowledge about the fine structure of lightning processes at Jupiter was substantially limited by the time resolution of previous measurements. Recent observations of the Juno mission revealed electromagnetic signals of Jovian rapid whistlers at a cadence of a few lightning discharges per second, comparable to observations of return strokes at Earth. The duration of these discharges was below a few milliseconds and below one millisecond in the case of Jovian dispersed pulses, which were also discovered by Juno. However, it was still uncertain if Jovian lightning processes have the fine structure of steps corresponding to phenomena known from thunderstorms at Earth. Here we show results collected by the Juno Waves instrument during 5 years of measurements at 125-microsecond resolution. We identify radio pulses with typical time separations of one millisecond, which suggest step-like extensions of lightning channels and indicate that Jovian lightning initiation processes are similar to the initiation of intracloud lightning at Earth.
PubMed: 37221170
DOI: 10.1038/s41467-023-38351-6 -
Biophysical Journal May 1995Electroporation involves the application of an electric field pulse that creates transient aqueous pathways in lipid bilayer membranes. Transport through these pathways... (Comparative Study)
Comparative Study
Electroporation involves the application of an electric field pulse that creates transient aqueous pathways in lipid bilayer membranes. Transport through these pathways can occur by different mechanisms during and after a pulse. To determine the time scale of transport and the mechanism(s) by which it occurs, efflux of a fluorescent molecule, calcein, across erythrocyte ghost membranes was measured with a fluorescence microscope photometer with millisecond time resolution during and after electroporation pulses several milliseconds in duration. One of four outcomes was typically observed. Ghosts were: (1) partially emptied of calcein, involving efflux primarily after the pulse; (2) completely emptied of calcein, involving efflux primarily after the pulse; (3) completely emptied of calcein, involving efflux both during and after the pulse; or (4) completely emptied of calcein, involving efflux primarily during the pulse. Partial emptying, involving significant efflux during the pulse, was generally not observed. We conclude that under some conditions transport caused by electroporation occurs predominantly by electrophoresis and/or electroosmosis during a pulse, although under other conditions transport occurs in part or almost completely by diffusion within milliseconds to seconds after a pulse.
Topics: Biological Transport; Electroporation; Erythrocyte Membrane; Fluoresceins; Humans; Indicators and Reagents; Kinetics; Microscopy, Fluorescence; Reproducibility of Results; Spectrometry, Fluorescence; Time Factors
PubMed: 7612828
DOI: 10.1016/S0006-3495(95)80363-2 -
Investigative Radiology Apr 2019The aim of this study was to quantitatively assess changes in collagen structure using MR T1- and T2*-mapping in a novel controlled ex vivo tendon model setup.
OBJECTIVES
The aim of this study was to quantitatively assess changes in collagen structure using MR T1- and T2*-mapping in a novel controlled ex vivo tendon model setup.
MATERIALS AND METHODS
Twenty-four cadaveric bovine flexor tendons underwent MRI at 3 T before and after chemical modifications, representing mechanical degeneration and augmentation. Collagen degradation (COL), augmenting collagen fiber cross-linking (CXL), and a control (phosphate-buffered saline [PBS]) were examined in experimental groups, using histopathology as standard of reference. Variable echo-time and variable-flip angle gradient-echo sequences were used for T2*- and T1-mapping, respectively. Standard T1- and T2-weighted spin-echo sequences were acquired for visual assessment of tendon texture. Tendons were assessed subsequently for their biomechanical properties and compared with quantitative MRI analysis.
RESULTS
T1- and T2*-mapping was feasible and repeatable for untreated (mean, 545 milliseconds, 2.0 milliseconds) and treated tendons. Mean T1 and T2* values of COL, CXL, and PBS tendons were 1459, 934, and 1017 milliseconds, and 5.5, 3.6, and 2.5 milliseconds, respectively. T2* values were significantly different between enzymatically degraded tendons, cross-linked tendons, and controls, and were significantly correlated with mechanical tendon properties (r = -0.74, P < 0.01). T1 values and visual assessment could not differentiate CXL from PBS tendons. Photo-spectroscopy showed increased autofluorescence of cross-linked tendons, whereas histopathology verified degenerative lesions of enzymatically degraded tendons.
CONCLUSIONS
T2*-mapping has the potential to detect and quantify subtle changes in tendon collagen structure not visible on conventional clinical MRI. Tendon T2* values might serve as a biomarker for biochemical alterations associated with tendon pathology.
Topics: Animals; Cattle; Collagen; Humans; Magnetic Resonance Imaging; Models, Animal; Phantoms, Imaging; Tendons
PubMed: 30444794
DOI: 10.1097/RLI.0000000000000532 -
Biochemistry Sep 2013To date, little work has been conducted on the relationship between solute and buffer molecules and conformational exchange motion in enzymes. This study uses solution...
To date, little work has been conducted on the relationship between solute and buffer molecules and conformational exchange motion in enzymes. This study uses solution NMR to examine the effects of phosphate, sulfate, and acetate in comparison to MES- and HEPES-buffered references on the chemical shift perturbation and millisecond, chemical, or conformational exchange motions in the enzyme ribonuclease A (RNase A), triosephosphate isomerase (TIM) and HisF. The results indicate that addition of these solutes has a small effect on (1)H and (15)N chemical shifts for RNase A and TIM but a significant effect for HisF. For RNase A and TIM, Carr-Purcell-Meiboom-Gill relaxation dispersion experiments, however, show significant solute-dependent changes in conformational exchange motions. Some residues show loss of millisecond motions relative to the reference sample upon addition of solute, whereas others experience an enhancement. Comparison of exchange parameters obtained from fits of dispersion data indicates changes in either or both equilibrium populations and chemical shifts between conformations. Furthermore, the exchange kinetics are altered in many cases. The results demonstrate that common solute molecules can alter observed enzyme millisecond motions and play a more active role than what is routinely believed.
Topics: Acetates; Alkanesulfonic Acids; Aminohydrolases; Animals; Buffers; HEPES; Morpholines; Nuclear Magnetic Resonance, Biomolecular; Phosphates; Protein Conformation; Ribonuclease, Pancreatic; Solutions; Sulfates; Thermotoga maritima; Triose-Phosphate Isomerase
PubMed: 23991940
DOI: 10.1021/bi400973e -
Journal of the American Chemical Society Nov 2009The three-dimensional structures of macromolecules fluctuate over a wide range of time-scales. Separating the individual dynamic processes according to frequency is of...
The three-dimensional structures of macromolecules fluctuate over a wide range of time-scales. Separating the individual dynamic processes according to frequency is of importance in relating protein motions to biological function and stability. We present here a general NMR method for the specific characterization of microsecond motions at backbone positions in proteins even in the presence of other dynamics such as large-amplitude nanosecond motions and millisecond chemical exchange processes. The method is based on measurement of relaxation rates of four bilinear coherences and relies on the ability of strong continuous radio frequency fields to quench millisecond chemical exchange. The utility of the methodology is demonstrated and validated through two specific examples focusing on the thermo-stable proteins, ubiquitin and protein L, where it is found that small-amplitude microsecond dynamics are more pervasive than previously thought. Specifically, these motions are localized to alpha helices, loop regions, and regions along the rim of beta sheets in both of the proteins examined. A third example focuses on a 28 kDa ternary complex of the chaperone Chz1 and the histones H2A.Z/H2B, where it is established that pervasive microsecond motions are localized to a region of the chaperone that is important for stabilizing the complex. It is further shown that these motions can be well separated from extensive millisecond dynamics that are also present and that derive from exchange of Chz1 between bound and free states. The methodology is straightforward to implement, and data recorded at only a single static magnetic field are required.
Topics: Histones; Kinetics; Magnetic Resonance Spectroscopy; Methods; Molecular Chaperones; Molecular Dynamics Simulation; Motion; Protein Conformation; Proteins
PubMed: 19842628
DOI: 10.1021/ja906842s -
Journal of the American Chemical Society May 2022Understanding water dynamics and structure is an important topic in biological systems. It is generally held in the literature that the interfacial water of hydrated...
Understanding water dynamics and structure is an important topic in biological systems. It is generally held in the literature that the interfacial water of hydrated phospholipids is highly mobile, in fast exchange with the bulk water ranging from the nano- to femtosecond timescale. Although nuclear magnetic resonance (NMR) is a powerful tool for structural and dynamic studies, direct probing of interfacial water in hydrated phospholipids is formidably challenging due to the extreme population difference between bulk and interfacial water. We developed a novel O solid-state NMR technique in combination with an ultra-high-field magnet (35.2 T) to directly probe the functionally important interfacial water. By selectively suppressing the dominant bulk water signal, we observed two distinct water species in the headgroup region of hydrated dimyristoylphosphatidylcholine (DMPC) lipid bilayers for the first time. One water species denoted as "confined water" is chemically and dynamically different from the bulk water (∼0.17 ppm downfield and a slightly shorter spin-lattice relaxation time). Another water species denoted as "bound water" has severely restricted motion and a distinct chemical shift (∼12 ppm upfield). Additionally, the bulk water is not as "free" as pure water, resulting from the fast exchange with the water molecules that weakly and transiently interact with the lipid choline groups. These new discoveries clearly indicate the existence of the interfacial water molecules that are relatively stable over the NMR timescale (on the order of milliseconds), providing an opportunity to characterize water dynamics on the millisecond or slower timescale in biomacromolecules.
Topics: Dimyristoylphosphatidylcholine; Lipid Bilayers; Magnetic Resonance Spectroscopy; Phospholipids; Water
PubMed: 35439409
DOI: 10.1021/jacs.2c02145 -
Genes To Cells : Devoted To Molecular &... Jan 2000Living cells have molecular machines for free energy conversion, for example, sliding machines in muscle and other cells, flagellar motors in bacteria, and various ion... (Review)
Review
Living cells have molecular machines for free energy conversion, for example, sliding machines in muscle and other cells, flagellar motors in bacteria, and various ion pumps in cell membranes. They are constructed from protein molecules and work in the nm (nanometer), pN (piconewton) and ms (millisecond) ranges, without inertia. In 1980s, a question was raised of whether the input-output or influx-efflux coupling in these molecular machines is tight or loose, and an idea of loose coupling was proposed. Recently, the long-distance multistep sliding of a single myosin head on an actin filament, coupled with the hydrolysis of one ATP molecule, was observed by Yanagida's group using highly developed techniques of optical microscopy and micromanipulation. This gave direct evidence for the loose coupling between the chemical reaction and the mechanical event in the sliding machine. In this review, I will briefly describe a historical overview of the input-output problem in the molecular machines of living cells.
Topics: Actins; Adenosine Triphosphatases; Animals; Bacteria; Energy Transfer; Flagella; Myosins
PubMed: 10651901
DOI: 10.1046/j.1365-2443.2000.00304.x