Supraspinal locomotor centers do/do not contribute significantly to the hyperpnea of dynamic exercise in humans.
Explore the source record for details and available documents.
Animals↗
SEARCH · PubMed Health
Results for “dynamics”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Comparison of cardiovascular response to combined static-dynamic effort, postprandial dynamic effort and dynamic effort alone in patients with chronic ischemic heart disease.
The cardiovascular responses to combined static-dynamic effort, postprandial dynamic effort and dynamic effort alone were evaluated by upright bicycle ergometry during equilibrium-gated blood pool scintigraphy in 24 men, mean age 59 +/- 8 years, with chronic ischemic heart disease. Combined static-dynamic effort and the postprandial state elicited a peak cardiovascular response similar to that of dynamic effort alone; work load 643 +/- 156 and 638 +/- 161 vs 650 +/- 153 kg-m/min, respectively; heart rate 147 +/- 14 and 145 +/- 14 vs 143 +/- 17 beats/min; systolic pressure 195 +/- 26 and 200 +/- 25 vs 197 +/- 25 mm Hg; and rate-pressure product 286 +/- 48 and 292 +/- 55 vs 282 +/- 52. Heart rate, intraarterial systolic and diastolic pressures, rate-pressure product and ejection fraction were similar for the three test conditions at the onset of ischemia and at peak effort. The prevalence and extent of exercise-induced ischemic left ventricular dysfunction, ST-segment depression, angina pectoris and ventricular ectopic activity were also similar during the three test conditions. Direct and indirect measurements of systolic and diastolic blood pressure were highly correlated. The onset of ischemic ST-segment depression and angina pectoris correlated as strongly with heart rate alone as with the rate-pressure product during all three test conditions. The cardiovascular response to combined static-dynamic effort and to postprandial dynamic effort becomes more similar to that of dynamic effort alone as dynamic effort reaches a symptom limit. If significant ischemic and arrhythmic abnormalities are absent during symptom-limited dynamic exercise testing, they are unlikely to appear during combined static-dynamic or postprandial dynamic effort. This simplifies, the task of formulating guidelines for physical effort in patients with chronic ischemic heart disease, especially in providing "clearance" to perform avocational and vocational tasks involving combined static-dynamic and postprandial dynamic effort.
Aged↗
Dynamic molecules: molecular dynamics for everyone. An internet-based access to molecular dynamic simulations: basic concepts.
Molecular dynamics is a rapidly developing field of science and has become an established tool for studying the dynamic behavior of biomolecules. Although several high quality programs for performing molecular dynamic simulations are freely available, only well-trained scientists are currently able to make use of the broad scientific potential that molecular dynamic simulations offer to gain insight into structural questions at an atomic level. The "Dynamic Molecules" approach is the first internet portal that provides an interactive access to set up, perform and analyze molecular dynamic simulations. It is completely based on standard web technologies and uses only publicly available software. The aim is to open molecular dynamics techniques to a broader range of users including undergraduate students, teachers and scientists outside the bioinformatics field. The time-limiting factors are the availability of free capacity on the computing server to run the simulations and the time required to transport the history file through the internet for the animation mode. The interactive access mode of the portal is acceptable for animations of molecules having up to about 500 atoms.
Computer Simulation↗
Molecular dynamics studies of heterogeneous dynamics and dynamic crossover in supercooled atomic liquids.
Supercooled liquids near the glass transition exhibit the phenomenon of heterogeneous relaxation; at any specific time, a nominally homogeneous equilibrium fluid undergoes dynamic fluctuations in its structure on a molecular distance scale with rates that are very different in different regions of the sample. Several theoretical and simulation studies have suggested a change in the nature of the dynamics of fluids as they are supercooled, leading to the concept of a dynamic crossover that is often associated with mode coupling theory. Here, we will review the use of molecular dynamics computer simulation methods to investigate heterogeneous dynamics and dynamic crossovers in models of atomic liquids.
Biophysics↗
Molecular dynamics simulation and essential dynamics study of mutated plastocyanin: structural, dynamical and functional effects of a disulfide bridge insertion at the protein surface.
A molecular dynamics simulation (1.1 ns) at 300 K, of fully hydrated Ile21Cys, Glu25Cys plastocyanin mutant has been performed to investigate the structural, dynamical and functional effects of a disulfide bridge insertion at the surface of the protein. A detailed analysis of the root mean square fluctuations, H-bonding pattern and dynamical cross-correlation map has been performed. An essential dynamics method has also been applied as complementary analysis to identify concerted motions (essential modes), that could be relevant to the electron transfer function. The results have been compared with those previously obtained for wild-type plastocyanin and have revealed that the mutant shows a different pattern of H-bonds, with several interactions lost and a higher flexibility, especially around the electron transfer copper site. The analysis of dynamical cross-correlation map and of essential modes, has shown that the mutant performs different functional concerted motions, which might be related to the binding recognition with its electron transfer partners in comparison with the wild-type protein.
Algorithms↗
Elements of dynamics VI: the dynamic unconscious and unconscious dynamics.
The dynamic unconscious remains in contention in cognitive psychology. Academic settings may not provide the compelling evidence of unconscious dynamics regularly experienced by dynamic psychiatrists, psychoanalysts, and other physicians, including neurologists treating psychogenic motor disorders in the movement disorder clinic. An origin of unconscious motor expression is postulated in the intermodal connectivity of neuromental agencies, extending an idea that originated in Freud's (1950/1966) "Project for a Scientific Psychology." Motoric alexithymia is contrasted with synesthesia. Other examples of unconscious psychodynamics of everyday life are readily found in sexual expression. Dynamic pressures that render processes unconscious may also originate interpersonally. Illustrations are drawn from cultural influence, peer and parental pressure, sports competition, military combat, and reactions to dangerous predators.
Affective Symptoms↗
A study of dynamic development in radiolesion and cell death of eukaryotes after exposure to ionizing radiation--the visualization of the dynamic reaction by means of cytochemical method with lactate dehydrogenase (LDH) as a nuclear marker and radiation-induced nuclear anomalization by an ultramicrostructural manifestation: a dynamic explanation.
The present work deals with the radiation effect on adult rats suffering from acute, whole-body irradiation with cobalt-60 gamma rays of dosages 100R and 300R respectively. The morphological alteration of the lymphocytic nucleus and exhibition of cytochemical reaction of LDH in intra- or extra-nuclear region has been observed at the end of predetermined time intervals after irradiation. A close relationship between the percentage of damage of the lymphocytic nucleus and that of positivity of LDH reaction is seen from their variations with time parallel. From technical color microphotographs which exhibit cytochemical reactions, the existence of enzyme LDH in the nucleus so far obscure has been visually recognized. The events happening in enzymic reaction and the leakage of enzyme across the nuclear envelope reflect the dynamic nature. The ultrastructural alteration of nuclear anomalization confirms the dynamic development of inducing radiolesion. The experimental facts inspire us to attempt an explanation of cellular radiolesion and cell death owing to ionization radiation in light of the dynamic concept.
Animals↗
Reproducibility of dynamical heterogeneities and metabasin dynamics in glass forming liquids: the influence of structure on dynamics.
The discovery that the propensity for particle motion in a supercooled liquid is completely determined by the initial structure pointed to the existence of a causal link between structure and dynamics in glassy systems. Here we demonstrate that this underlying influence of structure is only local in time, fading out beyond the metabasin lifetime much before the relaxation time. Thus, our results reveal the irreproducibility of metabasin dynamics and support the scenario of a random walk on metabasins for the long time diffusion.
Computer Simulation↗
The use of inverse dynamics solutions in direct dynamics simulations.
Previous attempts to use inverse dynamics solutions in direct dynamics simulations have failed to replicate the input data of the inverse dynamics problem. Measurement and derivative estimation error, different inverse dynamics and direct dynamics models, and numerical integration error have all been suggested as possible causes of inverse dynamics simulation failure. However, using a biomechanical model of the type typically used in gait analysis applications for inverse dynamics calculations of joint moments, we produce a direct dynamics simulation that exactly matches the measured movement pattern used as input to the inverse dynamic problem. This example of successful inverse dynamics simulation demonstrates that although different inverse dynamics and direct dynamics models may lead to inverse dynamics simulation failure, measurement and derivative estimation error do not. In addition, inverse dynamics simulation failure due to numerical integration errors can be avoided. Further, we demonstrate that insufficient control signal dimensionality (i.e., freedom of the control signals to take on different "shapes"), a previously unrecognized cause of inverse dynamics simulation failure, will cause inverse dynamics simulation failure even with a perfect model and perfect data, regardless of sampling frequency.
Biomechanical Phenomena↗
Dynamics of everyday life: rigorous modular modeling in neurobiology based on Bloch's dynamical theorem.
Natural, everyday sensorimotor behaviors, such as rising from sitting, typically have an intrinsic organization of several levels of analysis. Taking this intrinsic organization as key to understanding neural dynamics is neither a top-down nor a bottom-up approach, but rather a meshing of multiple centers and levels of analysis. Motor control requires body dynamics that are consistent with physical dynamics, besides the more microscopic levels of neural dynamics. The dynamics of separate movements have been investigated as if the ends can be capped off, separated from the rest of the individual's life. Is this dynamically correct? Even chaotic behavior is deterministic. However, the mathematics of nonlinear oscillations is not all of dynamics. This paper relates Bloch's dynamical theorem to the modular, conditional approach to sensorimotor and other neural functioning. Bloch's dynamical theorem lays a foundation for the piecewise study of structurally accurate dynamics in theoretical neurobiology. Piecewise studies can be used as a modeling option complementary to the methods of nonlinear oscillator dynamics. By applying Bloch's theorem, dynamics of movements analyzed piecewise can be extended into a smooth flow on any manifold, either as a whole or conditionally. Conditional dynamics makes dynamical modeling options explicit, often depending on what variables the organism can control, and allows one to take different modeling options at different junctures in analyzing the same phenomenon. For example, this approach allows the study of complex motor control problems to be reduced to modular constructions using singularities and flow lines. Dynamical contingencies are expressed using the mathematics of ordered structures. This paper presents Bloch's dynamical theorem and its relevance to model construction in theoretical neurobiology. Specific examples, integrated into physiological and behavioral context, are cited from the literature.
Models, Neurological↗
Dynamic cooperativity of molecular processes in active streaming, muscle contraction, and subcellular dynamics: the molecular mechanism of self-organization at the subcellular level.
Life phenomena are a kind of ordered dynamics appearing in macroscopic systems, living systems. Schrödinger has proposed a molecular mechanism for the organization of life phenomena, i.e., 'order-from-order' mechanism where ordered dynamics are composed of molecular dynamics having order as the ordered dynamics of a watch is caused by orderly movements of its mechanical elements. However, neither evidence supporting the 'order-from-order' mechanism has been found in living systems nor the reason why molecular dynamics acquire order instead of disorder has been elucidated for more than 30 years. The latter is quite anomalous from the point of views of thermodynamics, which is based on disordered behaviors of molecules. In this paper, we verify from studies of a streaming system reconstituted from rabbit skeletal F-actin and HMM that one life phenomenon, active streaming, is caused by the 'order-from-order' mechanism. This is also the case for muscle contraction. Moreover, it is probable that this mechanism generally works at the subcellular level, not only in biological motilities but also in life phenomena at biomembranes. We also clarify that dynamic cooperativity among molecule gives rise to order in molecular dynamics. Hence, dynamic cooperativity is the key mechanism for life phenomena caused by the 'order-from-order' principle at the subcellular level. To produce dynamic cooperativity it is necessary for component molecules or elements to have three states, i.e., inactive (stable) state 0, energized or energy storing (quasi-stable) state 1, and active (unstable) state 2. Each molecule performs elementary cycle 0 yields 1 yields 2 yields 0 repeatedly by using free energy at the molecular level. In a state far from thermodynamic equilibrium dynamic cooperativity is yielded in 2 yields 0 due to a kind of triggering action of neighboring elements and breaks thermodynamic detailed balance. In addition, dynamic cooperativity gives component molecules long-range interactions which depend on the structure of organelles or molecular assemblies. Dynamic cooperativity is able to decrease entropy production and will give a high efficiency in chemo-mechanical conversions. Great progress would be achieved in the understanding of the molecular mechanisms and thermodynamic principles of energy transformations in biological systems, if molecular dynamics during transformation could be directly observed. This is not only because physical changes accompanied by specific movements of macromolecules are essentially involved but also because such molecular movements play a substantial role in energy transformation. Entirely new ideas will be needed for this purpose although high voltage electron microscopy or X-ray diffraction, for instance, is now expected as to be one of the possible tools in the future. Fortunately even at present it is possible to obtain important information on molecular dynamics from biochemical and physiological data, if analyses are properly performed...
Actomyosin↗
Reaction ensemble molecular dynamics: direct simulation of the dynamic equilibrium properties of chemically reacting mixtures.
A molecular simulation method to study the dynamics of chemically reacting mixtures is presented. The method uses a combination of stochastic and dynamic simulation steps, allowing for the simulation of both thermodynamic and transport properties. The method couples a molecular dynamics simulation cell (termed dynamic cell) to a reaction mixture simulation cell (termed control cell) that is formulated upon the reaction ensemble Monte Carlo (RxMC) method, hence the term reaction ensemble molecular dynamics. Thermodynamic and transport properties are calculated in the dynamic cell by using a constant-temperature molecular dynamics simulation method. RxMC forward and reverse reaction steps are performed in the control cell only, while molecular dynamics steps are performed in both the dynamic cell and the control cell. The control cell, which acts as a sink and source reservoir, is maintained at reaction equilibrium conditions via the RxMC algorithm. The reaction ensemble molecular dynamics method is analogous to the grand canonical ensemble molecular dynamics technique, while using some elements of the osmotic molecular dynamics method, and so simulates conditions that directly relate to real, open systems. The accuracy and stability of the method is assessed by considering the ammonia synthesis reaction N2 +3 H2 <-->2N H3 . It is shown to be a viable method for predicting the effects of nonideal environments on the dynamic properties (particularly diffusion) as well as reaction equilibria for chemically reacting mixtures.
Journal Article↗
Stroke recovery induced by coordination dynamic therapy and quantified by the coordination dynamic recording method.
Based on measurements of relative phase and frequency coordination of time-space distributed firing of single neurons and neuron assemblies in the human nervous system, the concept of coordination dynamics to describe the integrative functions of the human central nervous system (CNS) and the finding of neurogenesis in the human CNS, the coordination dynamic therapy has been developed with which it is possible to repair the lesioned or malfunctioning human CNS. With the developed coordination dynamic recording method the organization (the coordination dynamics) of the CNS can be measured on-line non-invasively. By measuring the present coordination dynamics at different times with ongoing coordination dynamic therapy when exercising on a special coordination dynamic therapy device, the progress in re-organization and repair of the lesioned CNS can be quantified. In this paper it is reported that in 8 patients following stroke the lesioned CNS could partly be repaired by coordination dynamic therapy. The repair was quantified by the improvement of walking, hand function and the direct measurement of CNS organization (the coordination dynamics). In 4 patients the improvement of CNS organization (coordinations dynamics) was 70 +/- 14% within 3 months of therapy. In a patient where the intensive coordination dynamic therapy (at least 4 hours therapy with more than 15,000 coordinated movements per day) lasted longer than one year, also the difficult repairable hand functions could substantially be improved. It is shown that in the healthy CNS of the author the coordination dynamics improved in the short-term memory by 20% within 10 min and in a stroke patient by 70% within 30 min, when exercising on the special coordination dynamic therapy device. As in other learning therapies (school) it is believed, that by repeated learning of movements, vegetative and higher mental functions in the short-term memory, the learned CNS functions will also go into the long-term memory, which means the CNS has been reorganized. Improvements in the short-term memory are used to motivate the patient to perform a therapy.
Adult↗
Coupling between lysozyme and glycerol dynamics: microscopic insights from molecular-dynamics simulations.
We explore possible molecular mechanisms behind the coupling of protein and solvent dynamics using atomistic molecular-dynamics simulations. For this purpose, we analyze the model protein lysozyme in glycerol, a well-known protein-preserving agent. We find that the dynamics of the hydrogen bond network between the solvent molecules in the first shell and the surface residues of the protein controls the structural relaxation (dynamics) of the whole protein. Specifically, we find a power-law relationship between the relaxation time of the aforementioned hydrogen bond network and the structural relaxation time of the protein obtained from the incoherent intermediate scattering function. We demonstrate that the relationship between the dynamics of the hydrogen bonds and the dynamics of the protein appears also in the dynamic transition temperature of the protein. A study of the dynamics of glycerol as a function of the distance from the surface of the protein indicates that the viscosity seen by the protein is not the one of the bulk solvent. The presence of the protein suppresses the dynamics of the surrounding solvent. This implies that the protein sees an effective viscosity higher than the one of the bulk solvent. We also found significant differences in the dynamics of surface and core residues of the protein. The former is found to follow the dynamics of the solvent more closely than the latter. These results allowed us to propose a molecular mechanism for the coupling of the solvent-protein dynamics.
Algorithms↗
A comparison of the effects of mixed static and dynamic work with mainly dynamic work in hot conditions.
Current physiological criteria for limiting work in hot conditions are frequently based on responses to mainly dynamic work (eg treadmill walking). Their applicability to industrial situations containing mixed static and dynamic work is questioned, since the physiological responses to static work are different from those of dynamic work. Each of eight subjects attempted a one hour uphill treadmill walk (mainly dynamic work), and an uphill treadmill walk whilst intermittently carrying a 20 kg weight in the arms (mixed static and dynamic work). The external work rates in the two conditions were equal, effected by lowering the treadmill gradient in the loaded condition. Experiments were conducted in a hot climate (33 degrees C dry bulb, 25 degrees C wet bulb). Oxygen consumption, minute ventilation, sweat rate and rated perceived exertion were all significantly higher (p less than 0.001) for the mixed static and dynamic work than for the dynamic work. This was also the case for heart rate and forearm skin temperature (p less than 0.01), and for auditory canal temperature (p less than 0.05). There was no significant difference between the two types of work for mean skin temperature, calf skin temperature and chest skin temperature. These results show that for the same external work, physiological strain and perceived exertion are greater for mixed static and dynamic work (carrying a load in the arms) than for mainly dynamic work (walking on a treadmill). They suggest that it is not appropriate to make direct comparisons of laboratory studies based on dynamic work, with practical situations containing mixed static and dynamic work in the heat.
Adult↗
Detection of hypervascular hepatocellular carcinoma by dynamic MRI and dynamic spiral CT.
OBJECTIVE: Our goal was to evaluate the detectability of hypervascular hepatocellular carcinomas (HCCs) by multislice dynamic MRI and dynamic spiral CT. MATERIALS AND METHODS: Prior to transcatheter arterial chemoembolization (TACE) with iodized oil, the liver was subjected to T1- and T2-weighted SE-MRI, multislice dynamic MRI after intravenous bolus injection of Gd-DTPA, early phase imaging with spiral CT (dynamic spiral CT) after intravenous bolus injection of contrast medium (at a rate of 2 or 3 ml/s), and delayed phase CT in 64 patients with 208 HCC nodules. The detectability of HCCs by MRI and CT was evaluated retrospectively compared with CT after TACE as a gold standard. RESULTS: The detectability of nodules < 1 cm in diameter was superior with dynamic MRI (67%) and dynamic spiral CT (50%) in comparison with SE-MRI (26%) and delayed phase CT (11%) (p < 0.01). The detectability of these tumors with dynamic MRI was significantly superior to that with dynamic spiral CT using an injection rate of 2 ml/s (p < 0.01), but not significantly different from that of dynamic spiral CT using a rate of 3 ml/s. CONCLUSION: Dynamic MRI and dynamic spiral CT are comparable for detecting hypervascular intrahepatic metastases of HCC.
Adult↗
Slowly adapting type I mechanoreceptor discharge as a function of dynamic force versus dynamic displacement of glabrous skin of raccoon and squirrel monkey hand.
The effects of dynamic force and dynamic displacement on single unit discharge rate during ramp stimulation were examined in 10 raccoon and 8 squirrel monkey slowly adapting Type I (SAI) mechanoreceptive afferent fibers, all having receptive fields on glabrous skin of the hand. In all 18 cases, power function exponents were higher for effects of dynamic displacement than for effects of dynamic force on discharge frequency. Thus, these SAI mechanoreceptors are more sensitive to variations in dynamic displacement than to variations in dynamic force. This differential sensitivity may be explained by the fact that the relationship between dynamic force and dynamic displacement is, itself, nonlinear, dynamic displacement being a power function of dynamic force, with exponents less than 1.0.
Action Potentials↗
Post-transition state dynamics for propene ozonolysis: Intramolecular and unimolecular dynamics of molozonide.
A direct chemical dynamics simulation, at the B3LYP6-31G(d) level of theory, was used to study the post-transition state intramolecular and unimolecular dynamics for the O3 + propene reaction. Comparisons of B3LYP6-31G(d) with CCSD(T)/cc-pVTZ and other levels of theory show that the former gives accurate structures and energies for the reaction's stationary points. The direct dynamics simulations are initiated at the anti and syn O3 + propene transition states (TSs) and the TS symmetries are preserved in forming the molozonide intermediates. Anti<-->syn molozonide isomerization has a very low barrier of 2-3 kcalmol and its Rice-Ramsperger-Kassel-Marcus (RRKM) lifetime is 0.3 ps. However, the trajectory isomerization is slower and it is unclear whether this anti<-->syn equilibration is complete when the trajectories are terminated at 1.6 ps. The syn (anti) molozonides dissociate to CH3CHO + H2COO and H2CO + syn (anti) CH3CHOO. The kinetics for the latter reactions are in overall good agreement with RRKM theory, but there is a symmetry preserving non-RRKM dynamical constraint for the former. Dissociation of anti molozonide to CH3CHO + H2COO is enhanced and suppressed, respectively, for the trajectory ensembles initiated at the anti and syn O3 + propene TSs. The dissociation of syn molozonide to CH3CHO + H2COO may also be enhanced for trajectories initiated at the syn O3 + propene TS. At the time the trajectories are terminated at 1.6 ps, the ratio of the trajectory and RRKM values of the CH3CHO + H2COO product yield is 1.6 if the symmetries of the initiation and dissociation TSs are the same and 0.6 if their symmetries are different. There are coherences in the intramolecular energy flow, which depend on molozonide's symmetry (i.e., anti or syn). This symmetry related dynamics is not completely understood, but it is clearly related to the non-RRKM dynamics for anti<-->syn isomerization and anti molozonide dissociation to CH3CHO + H2COO. Correlations are found between the stretching motions of molozonide, indicative of nonchaotic and non-RRKM dynamics. The non-RRKM dynamics of molozonide dissociation partitions vibration energy to H2COO that is larger than statistical partitioning. Though the direct dynamics simulations are classical, better agreement is obtained using quantum instead of classical harmonic RRKM theory. This may result from the neglect of anharmonicity in the RRKM calculations, the non-RRKM dynamics of the classical trajectories, or a combination of these two effects. The trajectories suggest that the equilibrium syn/anti molozonide ratio is approximately 1.1-1.2 times larger than that predicted by the harmonic densities of state, indicating an anharmonic correction.
Journal Article↗