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At least 379 records · Page 21Linked to original sources
PubMed1984

[A comparison of the effects of baclofen and some other muscle relaxants on alpha-rigidity in rats].

Muscle relaxant effects of baclofen were compared with those of dantrolene, diazepam, chlordiazepoxide and tolperisone. When administered intraduodenally (i.d.), baclofen and dantrolene but not diazepam suppressed the sustained rigidity of forelimbs in anemically decerebrated rats, and ED50 values of the former two drugs were 2.9 and 22 mg/kg, respectively. Baclofen, dantrolene and diazepam reduced the phasic rigidity of the decerebrated animals induced by mechanical stimulation of hindlimbs, with their respective ED50 values of 6.2, 140 and 1.4 mg/kg, i.d. Both the rigidities were almost insensitive to chlordiazepoxide and tolperisone. With the exception of tolperisone, these drugs also produced a muscle relaxation in intact animals as measured by traction (rats), rotarod (mice), and grip-strength (mice) tests. ED50 or eD25 values were calculated to be in the following ranges: 5.6 approximately 12 mg/kg, p.o. for baclofen, 15 approximately 35 mg/kg, p.o. for dantrolene, 2.1 approximately 6.5 mg/kg, p.o. for diazepam and 33 approximately 64 mg/kg, p.o. for chlordiazepoxide. These results suggest that baclofen, unlike other drugs, may be effective in reducing both tonic and phasic rigidities at lower doses than those causing muscle relaxation in intact animals.

Animals↗
PubMed1982

[Rigid-spine syndrome in a female patient (author's transl)].

A case of rigid spine syndrome in a woman is reported. There were a diffuse myopathic process, with atrophy and mild weakness not involving the face and a major rigidity of the spine. Contractures were present as well as a pure restrictive respiratory failure. Heart-rythm disorders and prolapse of the mitral valve were present. Histological features of a deltoid muscle biopsy were slight necrosis, lack of fibrosis and major disproportion in fiber-types. There were a high rate of fiber I and absence of fiber IIB. This case was similar to others described as Dubowitz's rigid spine syndrome. The histological features belonged to the second neuropathological group of cases, with disproportion in fiber-types. The rigid spine syndrome may be considered as a clinically definite disease and distinguished from other myopathies with orthopedic deformations. It should not be confused with arthrogryposis multiplex. The disease is probably autosomic recessive.

Adult↗
PubMedDate not supplied

Attenuation of the fentanyl-induced muscle rigidity by the selective 5HT1A agonist 8-OH-DPAT.

Fentanyl given in a low dose of 25 microgram/kg (ip) evoked a marked muscle rigidity measured directly by a mechanographic method in non-anesthetized rats. The selective 5HT1A receptor agonist 8-OH-DPAT (0.1, 0.3 and 1.0 mg/kg ip) showed only a tendency to attenuate the natural muscle tone. However, when that compound was given 40 min before (0.3 and 1.0 mg/kg ip) or 20 min after (1.0 mg/kg ip) fentanyl, it abolished the muscle rigidity. It is concluded that the serotonergic transmission, possibly via 5HT1A receptors, may participate in elucidation of the mechanism(s) of the fentanyl-induced muscle rigidity. These results seem to be clinically important in case other 5HT1A agonists, buspirone or gepirone (potent anxiolytics), also prevented fentanyl-induced muscle rigidity in humans.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMedDate not supplied

Fentanyl-induced chest wall rigidity in a neonate: a case report.

Fentanyl-induced chest wall rigidity occurred in an 8-week-old infant girl recovering from surgical repair of coarctation of the aorta. The neonate received 30 minutes of a moderate dose continuous infusion of fentanyl before chest wall rigidity developed. Association of the chest wall rigidity with the fentanyl infusion resulted in the appropriate intervention of narcotic reversal and prevented irreversible hypoxic sequelae. Patients receiving fentanyl, even at moderate doses, are at risk for the development of chest wall rigidity.

Female↗
PubMed1996

Muscarinic antagonists microinjected into the subthalamic nucleus decrease muscular rigidity in reserpinized rats.

The ability of anticholinergic agents microinjected into the subthalamic nucleus to reduce reserpine-induced muscular rigidity was assessed in rats. The electromyographical activity of the gastrocnemius-soleus muscle was used as a parameter of muscular rigidity. Reserpine (5 mg/kg i.p.) produced the appearance of electromyographical activity. The muscarinic antagonists M3 (1.27 nmol of 4-DAMP) and M1 (2.36 nmol of pirenzepine) markedly reduced the reserpine-induced electromyographical activity, whereas the M2 antagonist AFDX-116 (2.37 nmol) had no effect. These results suggest that a high cholinergic tone in the subthalamic nucleus is associated with the reserpine-induced muscular rigidity. Moreover, the M3 muscarinic antagonist is more effective than the M1 muscarinic antagonist in reducing the muscular rigidity in reserpinized rats, a model of Parkinson's disease, by blocking the high cholinergic tone in the subthalamic nucleus.

Anesthetics, Intravenous↗
PubMed1996

[A case of progressive continuous muscular rigidity and painless and rhythmic muscle spasm associated with autoantibody against glutamic acid decarboxylase].

We described a 60-year-old man with 5-year history of insulin dependent diabetes mellitus who developed continuous rigidity of truncal muscle and painless, rhythmic muscular spasm of trunk and proximal lower and upper extremities. The rigidity continued even in sleep. The painless muscle spasm was often precipitated by volitional movement and emotional stimuli. Intravenous administration of diazepam strongly attenuated the muscle spasm as well as truncal rigidity. Surface electromyography showed the continuous contraction of abdominal and paraspinal muscles. The rhythmic, clonic spasm of shoulder, triceps brachii, intercostal, abdominal, paraspinal and quadriceps femoris muscle induced by voluntary neck flexion was not compatible with typical stiff-man syndrome. Antibody against glutamic acid decarboxylase (GAD) was detected in the serum and cerebrospinal fluid of this patient. His condition was getting well with oral intake of sodium valproate. While painless, rhythmic spasm and persistent rigidity during sleep ruled out the patient from typical stiff-man syndrome, he was supposed to have the same pathophysiological mechanism as the anti-GAD autoantibody positive stiff-man syndrome.

Analgesia↗
PubMed1998

Muscle rigidity induced by fluphenazine in rats is antagonized by L-DOPA, an antiparkinsonian drug.

The aim of the present study was to find out whether the classic neuroleptic fluphenazine is a good model compound for inducing parkinsonian-like muscle rigidity in rats. The muscle tone was measured as resistance developed by the rat's hind foot to passive flexion and extension. Fluphenazine in doses of 0.4-3.0 mg/kg i.p. induced a dose-dependent increase in the hind foot resistance to passive movements. The muscle rigidity induced by fluphenazine 1.5 mg/kg i.p.) was counteracted in a dose-dependent manner by the main antiparkinsonian drug L-DOPA (25-75 mg/kg i.p.). The present results suggest that the fluphenazine-induced muscle rigidity may be a useful model of parkinsonian rigidity.

Animals↗
PubMed1991

Adherence of Pseudomonas aeruginosa to rigid gas-permeable contact lenses.

We examined the adherence of a human corneal isolate of Pseudomonas aeruginosa to unused rigid gas-permeable and hydrogel contact lenses. Adherence to rigid gas-permeable lenses was greater than the adherence to hydrogels. The lower incidence of microbial keratitis associated with rigid gas-permeable lenses, as compared with hydrogel lenses, may be attributed to the more rigorous cleaning and disinfection possible for rigid gas-permeable lenses and/or patient noncompliance with complicated disinfection systems used with hydrogel lenses.

Bacterial Adhesion↗
PubMed1988

Rigid internal fixation for fractures involving tooth-bearing maxillary segments.

Fracture dislocations of the middle third of the face usually involve a complex combination of the three types of fractures initially described by LeFort. Treatment of these injuries requires a six- to eight-week period of intermaxillary fixation, unless rigid internal fixation devices (plates and screws) are used to stabilize the fractures. However, rigid fixation carries the risk of producing a malunion and serious malocclusion if not performed correctly. A review of 22 patients with complex LeFort fractures treated with rigid fixation revealed that the only absolute contraindication to its use is difficulty in interdigitating the maxillary and mandibular teeth in a passive fashion at the time of fracture reduction. Rigid internal fixation should therefore be considered as an alternative treatment for most fractures of the middle third of the face.

Fracture Fixation, Internal↗
PubMed1987

Patient response to sigmoidoscopy. A randomized, controlled trial of rigid and flexible sigmoidoscopy.

Sigmoidoscopy could aid in the control of large bowel cancer by early detection of the 55% of colorectal cancers that develop in the rectosigmoid and by the identification and eradication of significant rectosigmoid adenomas. Rigid sigmoidoscopy has had poor patient acceptance and therefore has not been successful. The present study is a prospective randomized trial to evaluate patient response to flexible as compared with rigid sigmoidoscopy. Patients reported significantly less discomfort (10.1% versus 29.7%), anxiety (9.8% versus 27.6%) and embarrassment (5.2% versus 12.8%) during flexible as compared with rigid sigmoidoscopy. Flexible sigmoidoscopy appears to have better patient acceptance than rigid sigmoidoscopy (P less than 0.01). This could enhance its value as a cancer-control instrument. This article addresses the feasibility of sigmoidoscopy. Its validity also needs to be addressed within the framework of a long-term trial, evaluating mortality for rectosigmoid cancer.

Clinical Trials as Topic↗
PubMed1977

Cognitive rigidity in information processing of chronic undifferentiated schizophrenics.

This study investigated Concept Identification (CI) performance and hypothesis behavior of 100 chronic undifferentiated schizophrenic and matched normal Ss as functions of motor-cognitive, personality-perceptual, and psychomotor speed parameters of rigidity. The CI task was designed to test the effects of five levels of information complexity and to examine 10 categories of hypothesis strategies utilized in conceptual problem solving. It was found that normals were superior to schizophrenics in CI and that schizophrenics performed more poorly than normals at higher complexity levels. Normals were markedly less rigid on the motor-cognitive dimension than were schizophrenics. Correlational analysis revealed a number of reliable relationships between the three rigidity measures and the 10 hypothesis categories. Some insight was gained about the role of rigidity in utilization of effective strategies in problem solving; the psychomotor speed factor emerged as the best predictor of schizophrenics' hypothesis behavior.

Adaptation, Psychological↗
PubMed2003

Topological effects on the electrophoretic mobility of rigid rodlike DNA in polyacrylamide gels.

The electrophoretic migration of rigid rodlike DNA structures with well defined topologies has been investigated in polyacrylamide (PA) hydrogels prepared by copolymerization of acrylamide and N, N'-methylenebisacrylamide. Previous studies have reported structural and dynamic characteristics of linear and branched DNA during electrophoresis in PA gels using a variety of experimental parameters. However, a thorough investigation aimed at establishing specific relationships between topological features of rigid rodlike DNA structures and their electrophoretic behavior is still needed. In order to study these topological effects on mobility, an intensive examination of the electrophoretic mobility of small linear and starlike DNA was performed. A series of model DNA structures with well-defined branched topologies were synthesized with varying molecular parameters, such as number of arms surrounding the branch point and arm length. The electrophoretic mobility of these structures was then contrasted with a series of data obtained using linear DNA of comparable molecular size. When large DNA stars (M >/= 60 bp) were compared with linear DNA of identical molecular weight, the Ferguson plots were quite different. However, small DNA stars (24-32 bp) and linear analogues had identical Ferguson plots. This indicates that a different motional mode or greater interaction with the gel exists for the larger DNA stars. When the total molecular weight of the DNA stars was held constant and the number of arms varied, the Ferguson plots for all the stars were identical. Additionally, a critical pore size was reached when the ratio of linear DNA mobility to star DNA mobility increased dramatically. Thus, while the incorporation of a single branch point can produce a large reduction in mobility, above a critical molecular size, the incorporation of additional branch points does not appear to provide further reduction in mobility. This finding is consistent with the transport properties of large synthetic star polymers, where a large reduction in their diffusion coefficient is observed when a single branch is added. When additional arms are incorporated, large synthetic stars do not display an appreciable further reduction in diffusion coefficient. The effect of arm length on mobility for rigid rod DNA stars was also studied. For four-arm DNA stars, the mobility was found to scale as an exponential function of the arm length. Finally, a recently proposed phenomenological model was used to successfully fit the mobility data for linear rigid rod DNA at various concentrations of PA.

DNA↗
PubMedDate not supplied

Intramolecular interference effects in dynamic light scattering: rigid double spirals and superhelical DNAs.

A theory is developed for dynamic light scattering (DLS) from rigid double spirals by treating an invisible rigid cylinder with two helical scattering stripes on opposite sides of its cylindrical surface. The exact initial, or first cumulant, diffusion coefficient Dapp (K) is obtained in terms of the translational diffusion coefficients (D parallel and D perpendicular) parallel and perpendicular to the symmetry axis, the rotational diffusion coefficients (DR parallel and DR perpendicular) around the symmetry and transverse axes, the length (L) and radius (b) of the cylindrical surface bearing the stripes, and the pitch (p). Interference effects, namely geometrical antiresonances, between strands, produce deep minima in the static structure factor S (K) and corresponding prominent peaks in Dapp (K). These peaks in Dapp (K) depend sensitively on the rotational dynamics around the symmetry axis, and nearly vanish when DR parallel = 0. Some results for single spirals are also presented. A simpler model in which scattering points are attached at opposite ends of an otherwise invisible thin rigid rod is also treated, and shown to exhibit modest minima in S (K) and corresponding maxima in Dapp (K). Confining this rod to a plane containing K enhances the amplitudes of the oscillations in S (K) and Dapp (K), as expected. Rigid double spirals are employed as crude models for interwound supercoiled DNAs in order to assess the possible occurrence of interference effects. Although native supercoiled DNAs exhibit a cylinder diameter that is much too small to exhibit geometrical antiresonances in the presently accessible range of K2, nearly relaxed supercoiled DNAs are predicted to exhibit their first maximum in Dapp (K) just inside this range. Previously reported data for the effect of Escherichia coli single-strand binding (ssb) protein on the DLS of supercoiled pBR322 DNA cannot be mimicked by a gradual homogeneous reduction of superhelix density with increasing ssb, but instead can be mimicked by inhomogeneous all-or-none binding in which uncomplexed native DNAs and nearly relaxed saturated ssb/DNA complexes coexist in varying proportions. Experimental Dapp (K) and S (K) data for a sample of relaxed pUC8 dimers display, respectively, a broad maximum and a corresponding minimum, in qualitative agreement with rough theoretical predictions.

DNA Topoisomerases, Type I↗
PubMed2004

Partial rigid-body dynamics in NPT, NPAT and NPgammaT ensembles for proteins and membranes.

A partial rigid-body method of molecular dynamics simulations for proteins and membranes is presented. In this method, the symplectic integrator for rigid bodies is combined with the equations of motion for the NPT ensemble. The standard NPT ensemble is extended to the membrane-specific ensembles, the NPAT (constant normal pressure and lateral surface area of membranes and constant temperature) and NPgammaT (constant normal pressure and lateral surface tension of membranes and constant temperature) ensembles. By more than 30-ns simulations of aqueous proteins and hydrated lipid bilayers, the results of the partial rigid-body method demonstrated excellent conservation of total energy and consistent behavior with the traditional constraint method in terms of structural distribution and fluctuation of proteins and lipids. The efficient implementation of the partial rigid-body method in parallel computation is presented, which is shown to work well in large-scale molecular dynamics simulations.

Algorithms↗
PubMed1984

Less rigid internal fixation plates: historical perspectives and new concepts.

In the application of "rigid" plates for diaphyseal fractures, lack of callus healing and overprotection of the underlying bone are viewed by many investigators as undesirable consequences. Potential solutions offered to overcome these deficiencies include modification of the timing of plate removal, use of biologically degradable materials for plates so that stress-shielding can be minimized, and use of less rigid plate fixation systems. This study emphasizes the selection of appropriate design criteria for less rigid plate-fixation systems. To accomplish this goal, the axial, bending, and torsional stiffness parameters are considered in place of the oversimplified terms such as "flexible plate" or "elastic fixation." With the aid of finite element modeling and simplified bench experiments, we performed parametric studies and singled out the plate axial stiffness as the dominant factor in altering the bone stresses. As a result, we designed two experimental plates, one a thin Ti-6Al-4V (titanium with 6% aluminum and 4% vanadium) alloy plate with low stiffness in axial and bending directions, and the other a tubular stainless steel plate with low stiffness in the axial direction but moderate stiffness in bending and torsional directions. The low-stiffness Ti-6Al-4V alloy plate was first tested in a demanding bilateral canine midshaft osteotomy, and proved to be inadequate. Both experimental plates were successful in the unilateral osteotomies, with the tubular plate yielding the best results. After 6 months of plating, the bones beneath the tubular plate had superior mechanical and structural properties as compared to those of the control "rigid" stainless steel and the Ti-6Al-4V alloy plates. Application of this plate prolonged for 9 months did not cause reduction in bone properties and strength. The success of the tubular plate is due to its moderate bending and torsional stiffnesses, which provide adequate fixation to achieve callus union, while its low axial stiffness permits the underlying bone to share the physiological stresses needed for bone remodeling. These drastic changes in mechanical demands on the internal fixation plate during the early healing phase and the postunion remodeling phase are discussed.

Alloys↗
PubMed1986

Guidelines for external fixation frame rigidity and stresses.

Using results from FEM analyses and experiments as references, analytical methods are applied to develop simple approximate formulas to relate frame rigidity, maximal pin stresses, and peak pin-bone stresses in external fracture fixation (EFF) configurations in axial loading to the most important frame, pin, and bone parameters. It is found that, in a realistic range, the parameters can be adapted to vary the frame rigidity from about 13 N/mm to 17,000 N/mm, thereby reducing the maximal stresses in the pins and at the pin-bone interface by a factor of 140. In particular, when compromises have to be established in the frame characteristics in order to ensure a flexible configuration and limit the stress values at the same time, the formulas presented can provide useful guidelines. The side-bar separation and the pin modulus, in particular, can be adapted to decrease the rigidity, while only moderately increasing the stresses, thereby reducing changes for pin failure, pin-bone loosening, and pin-tract infection. A nomogram is presented for a quick reference to estimated relations between frame characteristics, rigidity, and stresses. It is believed that this material may be of use in EFF design and applications in clinical and animal experimental trials.

Biomechanical Phenomena↗
PubMed2005

Improving CAPRI predictions: optimized desolvation for rigid-body docking.

The ICM Docking and Interface Side-Chain Optimization (ICM-DISCO) showed promising predictive results during the first CAPRI experiment by successfully finding medium- or high-accuracy models in 3 of the 7 targets. A key factor was the ability to recognize near-native rigid-body geometries in a relatively low number of alternative docking poses, together with the successful refinement of the rigid-body docking interfaces. Since then, we have focused on improving the scoring function to optimally discriminate the near-native rigid-body conformations. For that, we have defined a new desolvation descriptor for rigid-body docking, based on atomic solvation parameters (ASPs) derived from octanol-water transfer experiments. This and other new approaches have been gradually incorporated into our docking procedure during our participation on the second CAPRI experiment. Overall, we produced reasonable models for 8 of the 9 official targets. Especially encouraging were those cases in which a homology model of 1 of the subunits had to be used during the docking simulations. And not less gratifying has been the successful prediction of antibody-antigen targets in a completely automatic, unrestrained fashion. In summary, our success rate (89%) shows a consistent improvement over the previous CAPRI rounds, and suggests that a correct desolvation description is key for improved protein-protein docking predictions.

Algorithms↗
PubMed2001

Bioorganic chemistry à la baguette: studies on molecular recognition in biological systems using rigid-rod molecules.

Initial studies using rigid-rod molecules or "baguettes" to address bioorganic topics of current scientific concern are reported. It is illustrated how transmembrane oligo(p-phenylene)s as representative model rods can be tuned to recognize lipid bilayer membranes either by their thickness or polarization. The construction of otherwise problematic hydrogen-bonded chains along transmembrane rods yields "proton wires," which act by a mechanism that is central in bioenergetics but poorly explored by means of synthetic models. Another example focuses on multivalent ligands assembling rigid-rod cell-surface receptors into transmembrane dynamic arene arrays. The potassium transport mediated by these ligand-receptor complexes provides experimental support for the potential biological importances of the controversial cation-pi mechanism. More complex supramolecular architecture is portrayed in the first artificial beta-barrels. It is shown how programmed assembly of toroidal rigid-rod supramolecules in detergent-free water permits control of diameter of the chemical nature of their interior. Reversed rigid-rod beta-barrels are assembled to function as self-assembled ionophores, ion channel models, and transmembrane nanopores. The potential of future intratoroidal chemistry is exemplified by encapsulation and planarization of beta-carotene in water and the construction of transmembrane B-DNA at the center of a second-sphere host-guest complex à al baguette.

Benzene Derivatives↗