Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RELAXATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7Linked to original sources
PubMed1988

Relaxation of isolated corpus cavernosum induced by smooth-muscle relaxant drugs. A comparative study.

Intracavernous injection of vasoactive substances are used in the treatment and investigation of impotence. We studied the effects induced by some pharmacological agents on strips of human erectile tissue. Specimens of corpus cavernosum were obtained from 16 men undergoing cystectomy or penectomy for bladder or penile malignancy. Strip preparations were mounted in thermostically controlled baths containing Krebs solution. Pharmacologic effects were monitored by means of an isotonic transducer. Papaverine was shown to be the substance able to cause the biggest relaxation effect. The authors compared the action of other drugs having a relaxant effect, studied the antagonist effects of epinephrine and dopamine on the pharmacologically relaxed preparations, and stressed that the relaxation of the erectile tissue has a determinant role in the appearance and maintenance of erection.

Adult↗
PubMed1988

Panic attacks during relaxation and relaxation-induced anxiety: a hyperventilation interpretation.

This paper explains how a hyperventilation theory of panic disorder accounts for panic attacks during relaxation and relaxation-induced anxiety. The explanation is based on the observation that chronic hyperventilators maintain a steady state of low pCO2 (arterial carbon dioxide tension) and are, therefore, sensitive to relatively small increases in ventilation when metabolism is low and to relatively sudden reductions in metabolism when ventilation is relatively constant. Thus, if minute volume of air breathed remains constant while the metabolic production of CO2 decreases, as in the case of one who sits down or lies down to relax, respiratory hypocapnea may increase in intensity until it produces the familiar sensations which mark the panic attack. Data from relevant studies of panic attacks during relaxation support the hyperventilation interpretation.

Anxiety Disorders↗
PubMed1980

Anaphylaxis to muscle relaxants: cross sensitivity between relaxants.

Two patients are described who had clinical anaphylaxis due to muscle relaxants. One patient had systemic hypersensitivity and positive intradermal tests to d-tubocurarine and alcuronium. The second had systemic hypersensitivity to d-tubocurarine and positive intradermal tests to d-tubocurarine, alcuronium, and pancuronium. It is suggested that positive intradermal tests to more than one relaxant may mean allergy to more than one relaxant rather than false positive test. Cross sensitivity between alcuronium and d-tubocurarine occurs and a similar situation may exist for suxamethonium and gallamine. When intradermal testing is carried out after anaesthetic reactions all relaxants should be tested.

Adult↗
PubMed1989

The Relaxation Inventory: self-report scales of relaxation training effects.

The development of a self-report measure to assess the effects of relaxation training was examined. A rigorous statistical method of scale construction consisting of a modification of the scale discrimination technique was employed, resulting in a 45-item questionnaire representing three orthogonally derived scales. The three scales, Physiological Tension, Physical Assessment, and Cognitive Tension, demonstrated adequate internal consistency with KR20 reliability coefficients of .89, .95, and .81, respectively. In a second study of predictive validity, 40 individuals were randomly assigned to one of four conditions: relaxation training, tension inducement, pre-postcontrol, or postcontrol. Univariate analysis of variance indicated significant findings for each of the three dimensions of the inventory. The Physiological Tension Scale detected significant increases in tension following tension inducement, whereas the Physical Assessment Scale and Cognitive Tension Scale detected increases in relaxation following relaxation training. Recommendations were made for future research on the inventory.

Adult↗
PubMed1992

Relaxation as an altered state of consciousness: a rationale for a general theory of relaxation.

A general theory of relaxation is presented. It is based on an integrated model of the main states of consciousness, which enables one to differentiate "techniques for relaxing" leading to the "relaxing states" and "meditative techniques" leading to the differentiated waking states of consciousness. These latter include specific "only the relaxation response states" and the "ultraconsciousness states". Each state is described along the following dimensions: of biological rhythms, i.e., Sleep-Wakefulness and the Basic Rest-Activity Cycle; brain hemispheric activity; the threshold of the extero- and interoceptive stimuli reception; perceptual dominance of stimuli from external or internal sources; spontaneous versus goal-oriented imagination activity, i.e., passive or active state of mind; feed-back relation with the surroundings.

Arousal↗
PubMed2002

Dy-DTPA derivatives as relaxation agents for very high field MRI: the beneficial effect of slow water exchange on the transverse relaxivities.

Proton longitudinal and transverse relaxivities of Dy(DTPA)(2-) and Dy-DTPA bisamide derivatives (Dy(DTPA-BA): Dy-DTPA bisamide, Dy(DTPA-BEA): Dy-DTPA bisethylamide, Dy(DTPA-BnBA): Dy-DTPA bis-n-butylamide, and Dy(DTPA-BBMA): Dy-DTPA bisbismethylamide) were analyzed between 0.47 T and 18.8 T. Curie longitudinal relaxation was clearly observed at magnetic fields larger than 2.4 T, but the longitudinal relaxivities are limited by the fast rotation of the complexes. Rotational correlation times were separately assessed by deuterium relaxometry of the diamagnetic deuterated lanthanum analogs. Transverse relaxivity, which depends on the square of the magnetic field and on the residence time of the coordinated water molecule (tau(M)), was more than 7.5 times larger at 18.8 T and 310 K for Dy(DTPA-BA) and Dy(DTPA-BEA) as compared to Dy(DTPA)(2-). This difference is mainly related to the slower water exchange of the bisamide complexes, as confirmed by the values of tau(M) measured by oxygen-17 relaxometry. Such Dy-complexes, characterized by relatively long tau(M) values (tauM310 larger than 100 ns but smaller than 1 micros), thus appear to be useful as negative T(2) (or transverse) contrast agents for high-field imaging. This was demonstrated by the spin-echo images of phantoms obtained at 4.7 T on samples containing Dy(DTPA)(2-) and Dy(DTPA-BEA).

Contrast Media↗
PubMed1997

Relax, a flexible program for the back calculation of NOESY spectra based on complete-relaxation-matrix formalism.

RELAX is a flexible program for the quantitative analysis of NOESY spectra. It allows the simultaneous application of different models describing the internal and overall motion of the molecule under investigation for individual spin pairs or groups of spins. A correction for anisotropy effects due to the deviation of the molecule from a spherical shape is calculated automatically from the trial structure. The program can deal with completely relaxed spectra as well as spectra recorded with a short relaxation delay. An execution-time-controlled splitting of the relaxation matrix reduces the computation time significantly without any loss of accuracy. This is especially important for large molecules or medium distance cutoffs.

Actins↗
PubMedDate not supplied

13C spin-lattice relaxation in natural diamond: Zeeman relaxation in fields of 500 to 5000 G at 300 K due to fixed paramagnetic nitrogen defects.

13C Spin-lattice relaxation (SLR) times in the laboratory frame have been measured at room temperature as a function of field in the range of 500 to 5000 G on two natural type 1b and 1a diamonds after dynamic nuclear polarization. Each of the diamonds contains two types of fixed paramagnetic centers with overlapping inhomogeneous electron paramagnetic resonance (EPR) lines. EPR techniques have been employed to identify these defects and to determine their concentrations and relaxation times at X-band. Three different nuclear SLR paths, namely that due to electron SLR and two types of three spin processes, are discussed. The one three-spin process (TSP) (type 1) involves a simultaneous transition of two electron spins belonging to the same hyperfine EPR line and a 13C spin while the other process (type 2) involves two electron spins belonging to different hyperfine EPR lines and a 13C spin. It is shown that the thermal contact between the 13C nuclear Zeeman and electron dipole-dipole interaction reservoirs decreases with an increase in field intensity, thus forming a bottleneck in the 13C relaxation path due to the type 1 TSP. The contribution of TSP of type 1 dominates that due to electron SLR and the type 2 TSP in relaxing the 13C nuclei in type lb diamond from about 1200 to 5000 G, while for type 1a diamond it dominates from 500 up to about 2200 G. In type 1a diamond over the range 2200 to 5000 G it seems that the type 2 TSP, which involves electrons of neighboring P2 hyperfine lines, dominates that of electron spin-lattice and the type 1 TSP. Over the range 500 to about 1200 G, a field-dependent electron SLR mechanism associated with N3 centers appears to dominate the 13C SLR.

Journal Article↗
PubMed1978

Experimental evidence for the role of cross-relaxation in proton nuclear magnetic resonance spin lattice relaxation time measurements in proteins.

Proton nuclear magnetic resonance (NMR) spin lattice relaxation time (T1) and spin-spin relaxation time (T2) measurements are presented for a number of proteins with molecular weights spanning the range of 6,500-150,000 daltons. These measurements provide experimental evidence for the role of cross-relaxation in 1H NMR T1 measurements in proteins. The relationship between these measurements and the theory recently presented by Kalk and Berendsen is discussed. The results indicate that cross-relaxation dominates the T1 measurements for the larger proteins, even at relatively low resonance frequencies such as 100 MHz.

Chemical Phenomena↗
PubMed1992

Coupling of the relaxation and resonant elements in the autonomous chaotic relaxation oscillator (ACRO).

If a harmonic oscillator is embedded in a relaxation oscillator, the resulting system may behave like an autonomous chaotic relaxation oscillator (ACRO). The discharge transient of the relaxation oscillator excites sinusoidal oscillations in the harmonic oscillator and these sinusoids affect when the next discharge occurs. This can lead to chaotic intervals in the oscillator periods. A simple electronic model of the ACRO is studied over a wide range of parameters using numerical, analytic, and experimental techniques. The dynamics of the ACRO is found to be determined by three parameters: (1) tuning, (2) coupling, and (3) damping. Complex, intermittent outputs can always be inhibited by increasing the damping of the harmonic oscillator. For weak damping, strong coupling yields chaotic periods. With weak damping and weak coupling, complex behavior only occurs if the relaxation oscillator is tuned near a resonance of the harmonic oscillator. A new path to chaos, called a disruption bifurcation, is the source for intermittency in the ACRO. This bifurcation occurs when the amplitude of internal resonances is excited to the degree that existing limit cycles are disrupted.

Journal Article↗
PubMed2005

Development of a relaxation-inducing cluster expansion formalism for treating strong relaxation and correlation effects.

We present in this paper a comprehensive account of an explicitly spin-free coupled cluster theory for treating energy differences of open-shell states relative to a closed-shell ground state, where the open-shell states of interest are dominated by a few simple configuration state functions. We develop a valence-universal coupled cluster formalism to achieve this via a novel cluster expansion ansatz for the valence part of the wave operator, where the orbital relaxation and the correlation relaxation accompanying ionization/excitation from the ground state are taken care of to all orders in compact, efficient, and explicitly spin-free manner. The essential difference of our proposed ansatz from the ordinary and the normal-ordered cluster ansatz in vogue is that (a) we allow the valence cluster operators to be connected among themselves with spectator valence lines only and (b) we use suitable combinatoric factors accompanying powers of cluster operators thus connected, which are equal to the number of ways the operators can be joined, leading to the same excitation (the automorphic factor). We emphasize that such an ansatz does not generate terms (diagrams) with chains of cluster operators joined among themselves via spectator lines only. Barring only a few, almost all the terms in the working equations determining the cluster amplitudes involve contraction of the Hamiltonian with the cluster operators via at least one nonspectator line, leading to what we call a "strongly connected" series. The structure of the working equation is remarkably similar to the single-reference closed-shell equation, with a few additional terms. The presence of contractions among cluster operators via spectator lines introduces the additional physical effects of orbital and correlation relaxation using low-body cluster operators. As an illustrative application of the new multireference coupled cluster (CC) theory, we consider in this paper computation of ionization potentials (IPs) of one-valence problem with only one active orbital. The numerical applications are made for both the core- and the inner- and outer-valence IPs for several molecular systems. The numerical values demonstrate the superiority of the relaxation-inducing CC theory, as compared to the normal-ordered ansatz.

Journal Article↗
PubMed1974

Relaxation complexes of plasmids ColE1 and ColE2: unique site of the nick in the open circular DNA of the relaxed complexes.

The product of the induced relaxation of supercoiled DNA-protein relaxation complexes of colicinogenic factors E1 (ColE1) and E2 (ColE2) is an open circular DNA molecule with a strand-specific nick. Cleavage of the open circular DNA of each relaxed complex with the EcoRI restriction endonuclease demonstrates that the single-strand break is at a unique position. The site of the single-strand break in the relaxed ColE1 complex is approximately the same distance from the EcoRI cleavage site as the origin of ColE1 DNA replication.

Binding Sites↗
PubMed2006

Relaxation-based multichannel signal combination (RELAX-MUSIC) for ROC analysis of percept-related neuronal activity.

In this letter, we consider how to combine neuronal signals from multiple electrodes to optimally predict behavioral choices from observed neural activity. The predictability is often quantified by the area under the receiver operating characteristic (ROC) curve, also called choice probability (CP) in neurophysiology. We exploit a distribution-free relaxation based multichannel signal combination (RELAX-MUSIC) approach that requires only simple pairwise combination and recursive implementation for optimizing the area under the ROC curve. A permutation test is employed to assess the statistical significance of the derived CP. We demonstrate that the RELAX-MUSIC approach outperforms the commonly used response pooling and Fisher linear discriminant (FLD) methods. The excellent performances of the RELAX-MUSIC approach for predicting perceptual decisions from neural activity are demonstrated via examples using simulated and experimental data.

Action Potentials↗
PubMed1991

A cellular mechanism for impaired posthypoxic relaxation in isolated cardiac myocytes. Altered myofilament relaxation kinetics at reoxygenation.

Single, isolated rat ventricular myocytes were made hypoxic for 10 minutes and then reoxygenated. During hypoxia, there was a marked abbreviation of the mechanical twitch, without a decrease in its amplitude. Immediately after reoxygenation, both the time to peak shortening and the duration of relaxation were markedly prolonged, and they remained prolonged for 10-50 minutes. The alterations in contraction and relaxation were not associated with any change in the time course of either the transmembrane action potential or the cytosolic calcium transient, as recorded with the fluorescent probe indo 1. Intracellular pH, measured with a fluorescent probe (carboxyseminaphthorhodofluor), showed an acid shift during hypoxia and an alkaline rebound immediately after reoxygenation. The time courses of intracellular pH and contraction duration were not parallel during hypoxia or reoxygenation, and simulation of the alkaline pH shift by lowering PCO2 or superfusing NH4Cl (in the absence of exposure to hypoxia) did not quantitatively reproduce the prolongation of relaxation seen after reoxygenation. The prolongation of contraction after reoxygenation could be overridden by the beta-adrenergic agonist isoproterenol or the nonenzymatic phosphatase butanedione monoxime. We conclude that delayed relaxation after reoxygenation exists at the single cell level and is due to an alteration of the properties of the myofilaments. Intracellular pH is not the primary mediator of this alteration. We speculate that alteration of intracellular inorganic phosphate or covalent modification of the myofilaments might be involved.

Actin Cytoskeleton↗
PubMed1989

Isovolumic relaxation period as an index of left ventricular relaxation under different afterload conditions--comparison with the time constant of left ventricular pressure decay in the dog.

In order to determine whether isovolumic relaxation period (IRP) reflects left ventricular relaxation under different afterload conditions, 17 anesthetized, open chest dogs were studied, and the left ventricular pressure decay time constant (T) was calculated. In 12 dogs, angiotensin II and nitroprusside were administered, with the heart rate constant at 90 beats/min. Multiple linear regression analysis showed that the aortic dicrotic notch pressure (AoDNP) and T were major determinants of IRP, while left ventricular end-diastolic pressure was a minor determinant. Multiple linear regression analysis, correlating T with IRP and AoDNP, did not further improve the correlation coefficient compared with that between T and IRP. We concluded that correction of the IRP by AoDNP is not necessary to predict T from additional multiple linear regression. The effects of ascending aortic constriction or angiotensin II on IRP were examined in five dogs, after pretreatment with propranolol. Aortic constriction caused a significant decrease in IRP and T, while angiotensin II produced a significant increase in IRP and T. IRP was affected by the change of afterload. However, the IRP and T values were always altered in the same direction. These results demonstrate that IRP is substituted for T and it reflects left ventricular relaxation even in different afterload conditions. We conclude that IRP is a simple parameter easily used to evaluate left ventricular relaxation in clinical situations.

Angiotensin II↗
PubMed2004

MaxiK channel roles in blood vessel relaxations induced by endothelium-derived relaxing factors and their molecular mechanisms.

The endothelium of blood vessels plays a crucial role in the regulation of blood flow by controlling mechanical functions of underlying vascular smooth muscle. The regulation by the endothelium of vascular smooth muscle relaxation and contraction is mainly achieved via the release of vasoactive substances upon stimulation with neurohumoural substances and physical stimuli. Nitric oxide (NO) and prostaglandin I2 (prostacyclin, PGI2) are representative endothelium-derived chemicals that exhibit powerful blood vessel relaxation. NO action involves activation of soluble guanylyl cyclase and PGI2 action is initiated by the stimulation of a cell-surface receptor (IP receptor, IPR) that is coupled with Gs-protein-adenylyl cyclase cascade. Many studies on the mechanisms by which NO and PGI2 elicit blood vessel relaxation have highlighted a role of the large conductance, Ca2+-activated K+ (MaxiK, BKCa) channel in smooth muscle as their common downstream effector. Furthermore, their molecular mechanisms have been unravelled to include new routes different from the conventionally approved intracellular pathways. MaxiK channel might also serve as a target for endothelium-derived hyperpolarizing factor (EDHF), the non-NO, non-PGI2 endothelium-derived relaxing factor in some blood vessels. In this brief article, we review how MaxiK channel serves as an endothelium-vascular smooth muscle transducer to communicate the chemical signals generated in the endothelium to control blood vessel mechanical functions and discuss their molecular mechanisms.

Animals↗
PubMed1975

Relaxation complexes of plasmid DNA and protein. I. Strand-specific association of protein and DNA in the relaxed complexes of plasmids ColE1 and ColE2.

The ColE1 and ColE2 relaxation complexes of supercoiled DNA and protein were purified from Escherichia coli cells. Protein remains associated with the open circular DNA of these complexes after induction of relaxation with sodium dodecyl sulfate. The protein is associated specifically with the strand that possesses a site-specific break in the Co1E1 and ColE2 relaxed complexes. This protein remains associated with the DNA after centrifugation of the relaxed complex in a neutral or alkaline (pH 12.5) cesium chloride gradient or treatment with 8 M urea, 2 M NaSCN, 2M LiCl, 0.2 M sodium acetate, pH 4.6, and 70% formamide at 60 degrees.

Acetates↗
PubMed1975

Relaxation complexes of plasmid DNA and protein. II. Characterization of the proteins associated with the unrelaxed and relaxed complexes of plasmid ColE1.

The proteins of the DNA-protein relaxation complex of plasmid ColE1 were labeled with [3H]leucine by growth of ColE1 containing Escherichia coli cells in the presence of this radioactive labeled amino acid. Three major [3H]leucine-labeled proteins are found associated with the supercoiled DNA in the ColE1 relaxation complex. The molecular weights of these proteins, determined by sodium dodecyl sulfate-acrylamide gel electrophoresis, are 60,000, 16,000, and 11,000, respectively. Induction of relaxation of the supercoiled DNA by treatment of the complex with sodium dodecyl sulfate results in a dissociation of the two smaller proteins from the DNA. The 60,000 protein, however, remains associated specifically with the nicked strand of the open circular DNA. The strand-specific association of this protein with the relaxed DNA resists heat denaturation of the DNA, sedimentation through an alkaline (pH 12.5) sucrose gradient, and centrifugation to equilibrium in an alkaline (pH 12.5) CsCl gradient.

Bacterial Proteins↗