Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Rotation”

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 721 records · Page 40Linked to original sources
PubMed2001

Internal/external rotation moment arms of muscles at the knee: moment arms for the normal knee and the ACL-deficient knee.

Knowledge of the three-dimensional balance of loads at the knee joint is required to adequately assess the treatment and rehabilitation of the malfunctioning knee. This report focuses upon the moment arms for the knee in internal/external (IE) rotation motion. It augments prior work that defined flexion/extension moment arms. Muscle excursions and angular motion of the lower leg during IE rotation were measured in 17 fresh-frozen hemi-pelvis specimens. Moment arms were calculated as the derivatives of excursion with respect to the angle. Rotational motion was performed for the normal and anterior cruciate ligament (ACL)-deficient knee. Of the 13 muscles measured at the knee, seven were significant contributors to IE rotation: the biceps femoris long and short head externally rotate opposite the gracilis, sartorious, semimembranosis, semitendonosus and popliteus, functioning as internal rotators. Moment arm magnitudes were greatest with the knee in a flexed position (internal [external] rotators peaked at 70 degrees [90 degrees] flexion). At 30 degrees flexion, the IE rotation moment arm minima and maxima were 10.1-11.6, 6.8-9.0, 6.0-15.7, 8.2-14.1 and 0.0-10.4 mm for the semimembranosis, semitendonosus, gracilis, sartorius and popliteus, and 14.7-27.9 and 18.5-31.5 mm for the biceps femoris short and long, respectively. Moment arms for the ACL-deficient condition were significantly changed only at extremes of flexion-extension.

Adult↗
PubMed2003

Synergy of medial and lateral hamstrings at three positions of tibial rotation during maximum isometric knee flexion.

Rotation of the knee has been used to isolate the strength of the medial and lateral hamstrings during manual testing of the knee flexors. The purpose of this study was to determine if medial and lateral rotation of the knee during manual knee flexor strength testing increased the electromyographic activity of the respective hamstrings. Twenty-three women between 22 and 36 years old with no history of lower extremity injury or disease participated in the study. Indwelling fine wire electrodes were used to record EMG activity of the medial (semitendinosus and semimembranosus) and lateral (long and short heads of the biceps femoris) hamstring muscles during maximally resisted knee flexion with neutral, medial, and lateral rotation of the knee. Repeated measures analysis of variance with post hoc Bonferroni adjustments were used to compare EMG activity across the three tests. EMG activity increased significantly for the target hamstrings during ipsilateral rotation (P<0.05). The semitendinosus had a mean activity of 109% Max. during medial rotation as opposed to 95% Max. during lateral rotation. The semimembranosus averaged 107 and 89% Max. in medial and lateral rotation respectively. Conversely, both the long and short head of the biceps muscle showed significantly higher activity (P<0.05) during lateral compared to medial rotation (110 and 108% compared to 93 and 97%, respectively). Even though the differences are statistically significant they ranged from 2 to 13% only of maximum activity, the clinical importance of this small change in EMG activity is questionable.

Adult↗
PubMed1993

Tri- and diglycine backbone rotational dynamics investigated by 13C NMR multiplet relaxation and molecular dynamics simulations.

Backbone motional dynamics in tri- and diglycine have been investigated by using 13C NMR multiplet relaxation spectroscopy. Dipolar auto- and cross-correlation times were determined as a function of pH, ionic strength, and temperature. Molecular dynamics simulations and phi,psi bond rotation energy profiles were calculated for insight into the physical nature of backbone rotations that could contribute to 13C relaxation. Various motional models were used to fit the experimental data. For internal glycine G2 in triglycine, restricted and unrestricted rotational diffusion models both underestimate internal correlation times, although they do agree that the axis of fastest internal rotation is directed closely along the C alpha-C bond. For di- and triglycine, significant pH dependencies in cross-correlation times for C-terminal glycines, and more so for those of N-terminal glycines, indicate the importance of the ionization state in internal mobility of terminal backbone positions. For terminal glycines, rotational jump models which allow for diffusive-like fluctuations within minima best explain the experimental data. phi,psi rotational fluctuation amplitudes and internal rotational energy barriers derived from the temperature dependence of 13C relaxation parameters, which range from 3 to 5 kcal/mol, agree well with those values calculated in rotational energy profiles.

Amino Acid Sequence↗
PubMed2000

Myosin motor domain lever arm rotation is coupled to ATP hydrolysis.

We have investigated coupling of lever arm rotation to the ATP binding and hydrolysis steps for the myosin motor domain. In several current hypotheses of the mechanism of force production by muscle, the primary mechanical feature is the rotation of a lever arm that is a subdomain of the myosin motor domain. In these models, the lever arm rotates while the myosin motor domain is free, and then reverses the rotation to produce force while it is bound to actin. These mechanical steps are coupled to steps in the ATP hydrolysis cycle. Our hypothesis is that ATP hydrolysis induces lever arm rotation to produce a more compact motor domain that has stored mechanical energy. Our approach is to use transient electric birefringence techniques to measure changes in hydrodynamic size that result from lever arm rotation when various ligands are bound to isolated skeletal muscle myosin motor domain in solution. Results for ATP and CTP, which do support force production by muscle fibers, are compared to those of ATPgammaS and GTP, which do not. Measurements are also made of conformational changes when the motor domain is bound to NDP's and PP(i) in the absence and presence of the phosphate analogue orthovanadate, to determine the roles the nucleoside moieties of the nucleotides have on lever arm rotation. The results indicate that for the substrates investigated, rotation does not occur upon substrate binding, but is coupled to the NTP hydrolysis step. The data are consistent with a model in which only substrates that produce a motor domain-NDP-P(i) complex as the steady-state intermediate make the motor domain more compact, and only those substrates support force production.

Adenosine Triphosphate↗
PubMed2003

Controlled rotation of biological microscopic objects using optical line tweezers.

Controlled, continuous rotation of cells or intracellular objects was achieved using optical tweezers with an elliptic beam profile (line tweezers), which was generated by placing a cylindrical lens in the path of the trapping beam. By rotating the cylindrical lens, rotation of the elliptic trapping beam and hence of the object trapped therein was achieved. Compared to previously reported techniques for rotation of microscopic objects, this approach is much simpler, gives better utilization of available laser power and also allows much easier control of the trap beam profile. We have used this approach for rotation of biological objects varying in size from 2 to 40 microm. At 25 mW trapping beam power at the object plane E. coli bacteria could be rotated at speeds approaching 10 Hz and an intracellular object (presumably a calcium oxalate crystal) trapped inside Elodea densa plant cell could be rotated with speeds of up to 4 Hz. To our knowledge, this is the first report for rotation of an intracellular object.

Cell Movement↗
PubMed1987

Effects of stimulus complexity on mental rotation rate of polygons.

Both spatial and propositional theories of imagery predict that the rate at which mental images can be rotated is slower the more complex the stimulus. Four experiments (three published and one unpublished) testing that hypothesis found no effect of complexity on rotation rate. It is argued that despite continued methodological improvements, subjects in the conditions of greater complexity may have found it sufficient to rotate only partial images, thereby vitiating the prediction. The two experiments reported here are based on the idea of making the discriminative response sufficiently difficult so as to force the rotation of complete images. The first one scaled the similarity between standard polygons and certain systematically mutated versions. From the ratings so obtained, two levels of perceived similarity, high and low, were defined and served as separate conditions in a response-time, image rotation experiment. The second experiment tested the complexity hypothesis by examining the effect of similarity on rotation rates and its interaction with levels of complexity. The results support the complexity hypothesis, but only for the highly similar stimuli. Rotation times were also generally slower for high as compared with low similarity. It is argued that these results arise because subjects rotate incomplete images when the stimuli are not very similar.

Cues↗
PubMed1996

Lateral bias for rotational behavior in tufted capuchin monkeys (Cebus apella).

This research examined lateral bias for rotational behavior in tufted capuchin monkeys (Cebus apella). A symmetrical distribution of rotational bias was noted, with approximately equal numbers of subjects preferring to turn to the right and to the left. As a group, adults did not exhibit a lateral rotational bias. Immatures preferentially rotated to the left. Across subjects, the strength of rotational bias was positively related to the incidence of right-eyed looking. Rotational bias was not related to hand preference. The finding of analogous age-dependent patterns of rotational bias in capuchins and in humans suggests that the rotational behavior of Cebus apella can be used to model an asymmetric response pattern that has been linked to development in Homo sapiens.

Age Factors↗
PubMed2001

Effect of head rotation on lateral cephalometric radiographs.

The purpose of this study was to identify the potential projection errors of lateral cephalometric radiographs due to head rotation in the vertical Z-axis. For this investigation, 17 human dry skull samples with permanent dentition were collected from the Department of Anatomy in the College of Medicine, Chosun University. They had no gross asymmetry and were well preserved. Each dry skull was rotated from 0 degrees to +/- 15 degrees at 1 degrees intervals. A vertical axis, the Z-axis, was used as a rotational axis to have 527 lateral cephalometric radiographs exposed. The findings were that: (1) angular measurements have fewer projection errors than linear measurements; (2) the greater the number of landmarks on the midsagittal plane that are included in angular measurements, the fewer the projection errors occurring; (3) horizontal linear measurements decrease gradually in length as the rotational angle toward the film increases, whereas a small increase and then decrease of the length occurs as the rotational angle toward the focal spot increases; (4) horizontal linear measurements have more projection errors than vertical linear measurements according to head rotation; and (5) projection errors of vertical linear measurements increase as the distance from the rotational axis increases. In summary, angular measurements of lateral cephalometric radiographs are more useful than linear measurements in minimizing the projection errors associated with head rotation on a vertical axis.

Cephalometry↗
PubMed2001

Breakthrough waves during ventricular fibrillation depend on the degree of rotational anisotropy and the boundary conditions: a simulation study.

INTRODUCTION: The left ventricle (LV) and right ventricle (RV) are characterized by specific fiber orientation known as "rotational anisotropy." However, it remains unclear whether the LV and RV are different with regard to the effect of rotational anisotropy on the dynamics of scroll waves during ventricular fibrillation (VF). To resolve this issue, we used a computation-based model to study scroll wave behavior. METHODS AND RESULTS: We composed an environment of simulated three-dimensional ventricular wall slabs, with optional ratios of fiber rotation to wall thickness (0 degrees, 6 degrees, and 12 degrees/mm thickness; LV 10 mm, RV 5 mm), using Luo-Rudy phase I equations. When rotational anisotropy was not incorporated into the LV wall slab (theta endo to approximately theta epi = 0 degrees), most scroll waves rotated around the filaments perpendicular to the tissue surface, with only a few accompanying breakthrough waves. In a twisted LV model (theta endo to approximately theta epi = 60 degrees and 120 degrees), the scroll waves were demonstrated as multiple wavelets scattered spatiotemporally, frequently accompanied by breakthrough waves that were promoted by rotational anisotropy. In a twisted RV model (theta endo to approximately theta epi = 30 degrees and 60 degrees), single scroll waves and/or figure-of-eight reentrant waves appeared, with comparatively few breakthrough waves, regardless of the degree of fiber twist. CONCLUSION: The proportion of electrical effects of rotational anisotropy and tissue boundaries plays an important role in the genesis of breakthrough waves during VF, and the difference in wave propagating patterns and frequency spectrum of the ventricles may arise, in part, from the number of breakthrough waves promoted by rotational anisotropy.

Anisotropy↗
PubMed2000

Manual scapular stabilization: its effect on shoulder rotational range of motion.

OBJECTIVES: To study the effect of a recently described method of measuring shoulder rotational range of motion in which the scapula is manually stabilized, and to determine the reliability of that technique compared with measurements taken with the scapula unstabilized. DESIGN: Fifty high school athletes underwent measurement of shoulder rotational range of motion with and without the scapula manually stabilized. Measurements were performed by two groups of physical therapists blinded to the movement results, with repeat measurements performed 5 days later. RESULTS: Rotational motion measured with the scapula stabilized was significantly less than when it was measured with the scapula unstabilized. Reliability was comparable for the two techniques when measuring external rotation, but the new technique was more reliable for measuring internal rotation. CONCLUSION: Scapular stabilization should be used when measuring internal rotation of the shoulder to obtain more accurate measurement of pure glenohumeral rotation. The technique described is promising, but warrants further refinement before it can be recommended for widespread clinical use. With practice, in experienced clinicians' hands, this technique may be the most reliable method for measuring outcome in clinical trials and for following clinically significant rotational motion deficits.

Adolescent↗
PubMed2003

Effect of fatigue on torque output and electromyographic measures of trunk muscles during isometric axial rotation.

OBJECTIVES: To examine the changes in torque output resulting from fatigue, as well as changes in electromyographic measures of trunk muscles during isometric axial rotation and to compare these changes between directions of axial rotation. DESIGN: Subjects performed fatiguing right and left isometric axial rotation of the trunk at 80% of maximum voluntary contraction while standing upright. SETTING: A rehabilitation center. PARTICIPANTS: Twenty-three men with no history of back pain. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Surface electromyographic signals were recorded from 6 trunk muscles bilaterally. The primary torque in the transverse plane and the coupling torques in sagittal and coronal planes were also measured. RESULTS: During the fatiguing axial rotation contraction, coupling torques of both sagittal and coronal planes were slightly decreased and no difference was found between directions of axial rotation. Decreasing median frequency and an increase in electromyographic amplitude were also found in trunk muscles with different degrees of changes in individual muscles. There were significant differences (P<.05) between right and left axial rotation exertions in median frequency slope of external oblique, internal oblique, latissimus dorsi, and iliocostalis lumborum muscles, but no such difference was found in median frequency slope of rectus abdominis and multifidus muscles. This could be attributed to different functional roles among the muscles. Similar differences (P<.05) between right and left axial rotation in median frequency slope were also detected in the electromyographic amplitude slope of the trunk muscles. Coefficient of variation of the torque output and electromyographic activation in most of the trunk muscles increased during the fatigue process. CONCLUSION: The changing coupling torque, different fatigue rate, and activation changes of trunk muscles, as well as the increase in variability during fatiguing axial rotation exertion, could affect the internal loading and stability of the spine; this needs to be further quantified in future studies.

Abdominal Muscles↗
PubMed2002

Arthroscopic release of the rotator interval and coracohumeral ligament: An anatomic study in cadavers.

PURPOSE: The purpose of this cadaveric study was to examine the anatomy of the normal glenohumeral joint relevant to an arthroscopic rotator interval release and define both the endpoints of a complete release of the coracohumeral ligament and the relationship to surrounding tendons and nerves. TYPE OF STUDY: An anatomic cadaveric study. METHODS: Fifteen fresh-frozen cadaveric specimens were studied with 5 specimens in group I and 10 specimens in group II. Group I specimens were used to examine the relevant anatomy, including the structures at risk, the dimensions of the rotator interval, and potential endpoints for release of the coracohumeral ligament. Measurements included (1) the supraspinatus to the subscapularis distance, (2) the distance from the rotator interval to the deep surface of the coracoid process, and (3) the distance from the rotator interval to the coracoacromial ligament at the level of the glenoid. Group II specimens underwent arthroscopic release of the rotator interval using the appearance of the coracoacromial ligament as the superficial endpoint. Dissection was then performed to examine for complete release of the coracohumeral ligament and to assess the structures at risk of injury. RESULTS: The distance from the anterior edge of supraspinatus to the superior edge of subscapularis at the glenoid rim was 21.6 mm, which increased to 27.8 mm with joint distention. The minimum distance from the rotator interval to the deep surface of the coracoid process was 11.4 mm. Before distention, the coracoacromial ligament was an average of 6.2 mm from the rotator interval capsule. Arthroscopic release from the supraspinatus to the subscapularis resulted in complete resection of the coracohumeral ligament in all 15 specimens. There were no specimens with evidence of injury to the biceps tendon, supraspinatus, subscapularis, or the conjoint tendon. CONCLUSIONS: This study confirms that intra-articularly directed arthroscopic release of the rotator interval can safely lead to complete release of the coracohumeral ligament if dissection is taken superficially to the level of the coracoacromial ligament.

Arthroscopy↗
PubMed1999

Incidence and symptoms of clinically manifest rotator cuff lesions.

A clinical study of 200 unselected elderly subjects with an average age of 78 years living in retirement homes was performed to determine the prevalence of clinically manifest rotator cuff tears and the relevance of the tear for daily life. A comprehensive questionnaire was performed and the examination included the UCLA- and Constant-shoulder assessment scales and a multitude of special tests. The criteria for clinical diagnosis of a rotator cuff tear were a positive Jobe-test, diminished external rotation, a positive zero-degree-abduction test, the drop arm sign, pseudoparalysis and atrophy. By these criteria we found 28 (7%) rotator cuff tears in 25 people. There were 15 women and 10 men and the mean age of symptom onset was 55 years. Eleven craftsmen, 7 office workers and 7 housewives met our criteria for rotator cuff tears. Pain was present in 22 shoulders. Moderate weakness was found in 2 people and severe weakness in 22. In 20 people the range of motion was severely reduced and in 8 moderately reduced. Activities of daily living were impaired in all affected subjects. Eight people reported onset of symptoms after trauma. Patients with clinically diagnosed rotator cuff tears scored an average of 13 points in the UCLA-shoulder assessment scales and 40 points in the Constant-shoulder assessment scales. In conclusion rotator cuff may be symptomatic only in some people. Probably more anatomic than symptomatic rotator cuff tears exist, and it can be supposed that physical activities may be one possible reason for clinically relevant tears.

Aged↗
PubMed2001

The effects of combined x-axis translations and y-axis rotations on projected lamina junction offset.

OBJECTIVES: To quantify the projection errors caused by the combining of selected x-axis translations with selected y-axis rotations as seen on plain film anteroposterior (AP) radiographs. STUDY DESIGN: A computer was used to model the projection of the lamina junction and points on the lateral body margins of a 2-dimensional vertebral model onto an AP radiograph. This simulation was done in the neutral position and in a number of combinations of x-axis translations and y-axis rotations. RESULTS: Some combinations of x-axis translation and y-axis rotation can increase or decrease the projected horizontal lamina offset as compared with what would be found with rotation alone. The projection of some combinations may lead the viewer to believe that rotation of the vertebral model is in the opposite direction of its true rotation. CONCLUSION: The projections of combined movements of x-axis translations and y-axis rotations can lead to confusion when the clinician attempts to discern quantity and direction of y-axis vertebral rotation from the AP radiograph.

Computer Graphics↗
PubMed1989

Perceptual linkage of multiple objects rotating in depth.

When multiple objects rotate in depth, they are frequently perceived to rotate in the same direction even when perspective information signals counterrotation. Three experiments are reported on this tendency to recover the rotation directions of multiple objects in a nonindependent fashion (termed rotational linkage). Rotational linkage was strongly affected by slant in depth of the objects, image perspective, and relative starting phase of the objects. Linkage was found not to vary as a function of the relative rotation speed of the objects or the relative alignment of their rotation axes. Rotational linkage is interpreted as a tendency of the visual system to assign signed depths to objects based on a communality of image point direction.

Computer Simulation↗
PubMed1999

Influence of body roll on visually induced sensations of self-tilt and rotation.

Illusory self-tilt and illusory self-motion (vection) produced by rotation of a 360 degrees visual scene about the subject's roll axis was measured as a function of the presence or absence of actual rotation of the subject during acceleration of the visual scene. Rotation of the subject to a tilt of 15 degrees was at two levels of acceleration (onset) and with or without a delay between initial rotation and subsequent return (washout) to the vertical position. In one set of conditions, visual motion and subject motion were in opposite directions (concordant) and in another set they were in the same direction (discordant). In two control conditions, the subject was rotated while the visual scene remained stationary. For concordant motion the main effect of body rotation was to reduce the time taken by the subject to indicate self-tilt as compared with the response time to visual motion alone. The magnitude of estimated self-tilt was increased by actual body tilt as could be expected from addition of the perceived actual body tilt and the illusory body tilt induced by visual rotation. This effect of augmented body tilt did not persist after the body was returned to the vertical. The magnitude of vection was not markedly influenced by body rotation and washout. For discordant motion of body and the visual scene, subjects were confused and their responses were very variable, suggesting a nonlinear visual--vestibular interaction.

Adult↗
PubMed2004

Inverse regulation of rotation of F1-ATPase by the mutation at the regulatory region on the gamma subunit of chloroplast ATP synthase.

In F1-ATPase, the rotation of the central axis subunit gamma relative to the surrounding alpha3beta3 subunits is coupled to ATP hydrolysis. We previously reported that the introduced regulatory region of the gamma subunit of chloroplast F1-ATPase can modulate rotation of the gamma subunit of the thermophilic bacterial F1-ATPase (Bald, D., Noji, H., Yoshida, M., Hirono-Hara, Y., and Hisabori, T. (2001) J. Biol. Chem. 276, 39505-39507). The attenuated enzyme activity of this chimeric enzyme under oxidizing conditions was characterized by frequent and long pauses of rotation of gamma. In this study, we report an inverse regulation of the gamma subunit rotation in the newly engineered F1-chimeric complex whose three negatively charged residues Glu210-Asp211-Glu212 adjacent to two cysteine residues of the regulatory region derived from chloroplast F1-ATPase gamma were deleted. ATP hydrolysis activity of the mutant complex was stimulated up to 2-fold by the formation of the disulfide bond at the regulatory region by oxidation. We successfully observed inverse redox switching of rotation of gamma using this mutant complex. The complex exhibited long and frequent pauses in its gamma rotation when reduced, but the rotation rates between pauses remained unaltered. Hence, the suppression or activation of the redox-sensitive F1-ATPase can be explained in terms of the change in the rotation behavior at a single molecule level. These results obtained by the single molecule analysis of the redox regulation provide further insights into the regulation mechanism of the rotary enzyme.

Amino Acid Sequence↗
PubMed1955

Optical rotation and helical polypeptide chain configuration in collagen and gelatin.

The optical rotation phenomena exhibited by a citrate-extracted fraction of ichthyocol (from carp swim bladder), as well as by the parent gelatin derived therefrom, have been studied. Dispersion data for all cases follow a single-term Drude equation, but the variations with state are adequately expressed by simple reference to changes in [alpha](D) as follows:- 1. The native collagen fraction, dispersed in 0.15 M citrate buffer at pH 3.7 in the cold (11 degrees C.), yields a high negative specific rotation, [alpha](D), near -350 degrees . 2. During equilibration at 40 degrees C., which causes conversion to a monodisperse parent gelatin, the rotation drops to about -110 degrees . 3. Gelation at 2 degrees C. results in a partial regain of rotation to around -290 degrees . This mutarotation is reversible, depending on temperature. 4. In the range 0.02 to 0.28 per cent the native ichthyocol and the warm gelatin solutions show little concentration dependence, but with the cold gelatin solutions the specific rotation increases with concentration. Gelatin films formed by cold evaporation yield high specific rotation (ca. -620 degrees ), but those formed by hot evaporation retain low optical activity. 5. Since this same collagen-gelatin system has been investigated physicochemically, it is possible to relate molecular changes to the observed variations in optical rotation. Conclusions are similar to those of Robinson (1953), who studied other gelatins: high negative rotation is believed related to a native collagen polypeptide configuration, herein specified as helical (from x-ray diffraction considerations) and destroyed by heating. The possible roles of intermolecular interactions and of prevalent pyrrolidine constituents in influencing the helical configuration and optical activity are discussed.

Collagen↗