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PubMed1990

Rotational dynamics of the Ca-ATPase in sarcoplasmic reticulum studied by time-resolved phosphorescence anisotropy.

We have investigated the microsecond rotational motions of the Ca-ATPase in rabbit skeletal sarcoplasmic reticulum (SR), by measuring the time-resolved phosphorescence anisotropy of erythrosin 5-isothiocyanate (ERITC) covalently and specifically attached to the enzyme. Over a wide range of solvent conditions and temperatures, the phosphorescence anisotropy decay was best fit by a sum of three exponentials plus a constant term. At 4 degrees C, the rotational correlation times were phi 1 = 13 +/- 3 microseconds, phi 2 = 77 +/- 11 microseconds, and phi 3 = 314 +/- 23 microseconds. Increasing the solution viscosity with glycerol caused very little effect on the correlation times, while decreasing the lipid viscosity with diethyl ether decreased the correlation times substantially, indicating that the decay corresponds to rotation of the protein within the membrane, not to vesicle tumbling. The normalized residual anisotropy (A infinity) is insensitive to viscosity and temperature changes, supporting the model of uniaxial rotation of the protein about the membrane normal. The value of A infinity (0.20 +/- .02) indicates that each of the three decay components can be analyzed as a separate rotational species, with the preexponential factor Ai equal to 1.25X the mole fraction. An empirically accurate measurement of the membrane lipid viscosity was obtained, permitting a theoretical analysis of the correlation times in terms of the sizes of the rotating species. At 4 degrees C, the dominant correlation time (phi 3) is too large for a Ca-ATPase monomer, strongly suggesting that the enzyme is primarily aggregated (oligomeric).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2005

Light-driven molecular motors: stepwise thermal helix inversion during unidirectional rotation of sterically overcrowded biphenanthrylidenes.

To investigate the unidirectional rotation of chiral overcrowded biphenanthrylidenes in more detail, the size of the substituent next to the double bond responsible for the unidirectionality of rotation was varied. The thermal and photochemical isomerization of three sterically overcrowded alkenes is described. The behavior of the biphenanthrylidenes with methyl and ethyl substituents is rather similar, and these compounds undergo a unidirectional 360 degrees rotation around the central double bond in a four-step sequence involving two photochemical cis-trans isomerizations and two thermal helix inversions. The only difference between these two true molecular motors was a small entropic effect, which causes the ethyl substituted molecular motor to rotate slightly faster. The behavior of the i-propyl substituted compound differs significantly from that of the other two. Although not all different isomers of the i-propyl substituted molecular motor were detected spectroscopically, experimental data led to the conclusion that this compound can also be considered as a molecular motor and is capable of performing a 360 degrees unidirectional rotation. (1)H NMR and X-ray analysis show a meso-like form as an intermediate in the unidirectional rotation, which proves that the thermal helix inversion is a stepwise process.

Ketones↗
PubMed2005

Compartmental modeling of reversible intermolecular two-state excited-state processes coupled with rotational diffusion or with added quencher.

Analysis of related time-resolved fluorescence measurements can possibly lead to the determination of the kinetic parameters of excited-state processes. A deterministic identifiability analysis on an error-free fluorescence decay data surface has to be executed to verify whether the parameters of a particular model can be determined and may point to the minimal experimental conditions under which this will become possible. In this work, similarity transformation is chosen as an identifiability analysis approach because it also gives the explicit relationships between the true and alternative model parameters. Results are presented for two kinetic models of a reversible intermolecular two-state excited-state process in isotropic environments: (a) with coupled species-dependent rotational diffusion described by Brownian reorientation and (b) with added quencher. For model a, both spherically and cylindrically symmetric rotors, with no change in the principal axes of rotation in the latter, are considered. The fluorescence delta-response functions I(parallel)(t) and I(perpendicular)(t), for fluorescence polarized respectively parallel and perpendicular to the electric vector of linearly polarized excitation, are used to define the sum S(t) = I( parallel)(t) + 2 I( perpendicular)(t) and the difference D(t) = I(parallel)(t) - I(perpendicular)(t) function. The identifiability analysis is carried out using the S(t) and D(t) functions. The analysis involving S(t) shows that two physically acceptable possible solutions for the overall rate constants of the excited-state process exist. Inclusion of information from polarized fluorescence measurements on the rotational kinetic behavior contained in D(t) results in the unique set of rate constants and rotational diffusion coefficients when the rotational diffusion coefficients are different. For model b, it is shown that addition of quencher plays formally the same role as rotational diffusion as far as the identification is concerned. When the quenching rate constants are different, the rate constants of a reversible intermolecular two-state excited-state process with added quencher can be uniquely determined.

Diffusion↗
PubMed1998

The relationship of vertical and horizontal velocity gradients in the perception of shape, rotation, and rigidity.

Perceived shape, rotation, and rigidity were investigated in displays with linear velocity gradients in the vertical and horizontal directions. Different temporal relationships between these gradients simulated perspective projections of frontally oriented or rotated translating dihedral angles, orthographic projections of rotating dihedral angles, or nonrigid motion. Displays with nonzero horizontal gradients were judged to represent greater angle magnitudes (less relative depth) than displays with 0 horizontal gradients. The temporal relationship between the vertical and horizontal gradients did not influence judged shape but did affect rotation and rigidity judgments; rigid rotations were judged to rotate most, and nonrigid displays were rated as least rigid. These results indicate that the visual system integrates information from more than 1 velocity field. Possible integration methods based on first-order optic flow analysis are discussed.

Form Perception↗
PubMed1995

Representation of rotated objects in explicit and implicit memory.

The effects of rotating familiar and novel objects in depth between study and test were explored on short-term recognition, long-term recognition, and priming tasks. Short-term recognition memory was not affected by rotation in depth when the study and test views shared the same visible parts. However, long-term recognition was sensitive to rotation, even when all the parts were visible in both views. Priming was also affected by rotation, but only when study and test views did not share the same parts, or when test views were generated from rotations greater than 67 degrees. Together, the results suggest that long-term recognition memory is mediated by representations that specify viewpoint in depth precisely, whereas priming is mediated by representations that are more broadly tuned with respect to orientation. Furthermore, the insensitivity of the short-term recognition memory task to rotation suggests the possibility that viewpoint-invariant descriptions are generated from multiple successive views.

Humans↗
PubMed2002

Mental-rotation deficits following damage to the right basal ganglia.

The authors report the case of a woman with a right basal ganglia lesion and severe mental-rotation impairments. She had no difficulty recognizing rotated objects and had intact left-right orientation in egocentric space but was unable to map the left and right sides of external objects to her egocentric reference frame. This study indicates that the right basal ganglia may be critical components in a cortico-subcortical network involved in mental rotation. We speculate that the role of these structures is to select and maintain an appropriate motor program for performing smooth and accurate rotation. The results also have important implications for theories of object recognition by demonstrating that recognition of rotated objects can be achieved without mental rotation.

Aged↗
PubMed1990

Abrupt changes in flagellar rotation observed by laser dark-field microscopy.

Bacteria such as Escherichia coli and Salmonella typhimurium swim by rotating their flagella, each of which consists of an external helical filament and a rotary motor embedded in the cell surface. The function of the flagellar motor has been examined mainly by tethering the flagellar filament to a glass slide and observing the resultant rotation of the cell body. But under these conditions the motor operates at a very low speed (about 10 r.p.s.) owing to the unnaturally high load conditions inherent in this technique. Lowe et al. analysed the frequency of light scattered from swimming cells to estimate the average rotation speed of flagellar bundles of E. coli as about 270 r.p.s. To analyse motor function in more detail, however, measurement of high-speed rotation of a single flagellum (at low load) with a temporal resolution better than 1 ms is needed. We have now developed a new method--laser dark-field microscopy--which fulfils these requirements. We find that although the average rotation speed of S. typhimurium flagella is rather stable, there are occasional abrupt slowdowns, pauses and reversals (accomplished within 1 ms). These changes were frequently observed in mutants defective in one of the motor components (called the switch complex), suggesting that this component is important not only in switching rotational direction but also in torque generation or regulation.

Escherichia coli↗
PubMed2000

Respiratory-related genioglossus electromyographic activity in response to head rotation and changes in body position.

The purpose of this study was to assess the effect of changes in body and head positions on respiratory-related activity of the genioglossus muscle in normal subjects in 8 body and head positions: (1) upright body with head straight, (2) upright body with head rotated to the right, (3) upright body with head rotated to the left, (4) supine body with head straight, (5) supine body with head rotated to the right, (6) supine body with head rotated to the left, (7) lateral recumbent body to the right, and (8) lateral recumbent body to the left. Phasic activity of the genioglossus muscle decreased significantly when subjects rotated their heads and moved from the supine to the lateral recumbent position. It is therefore concluded that genioglossus muscle activity is modulated in response to head rotation and changes in body position.

Adult↗
PubMed2001

Rotational head motion concurrent to rhythmical mandibular opening movements.

We have previously demonstrated the existence of a functional-rhythmical coupling between the head and the mandible using maxillary and mandibular incisal tracking points. However, that data did not provide information neither on the movement of the head as a whole nor on the location of its instantaneous centre of rotation. Thus, the objective of the present study was to determine whether the head undergoes a rotational motion during mouth opening and to locate its putative instantaneous centre of rotation. The same 6 d.f. (degree of freedom) measuring device employed in our previous studies was used again to analyse data from five male adults (age range: 26-29 years old) chosen as subjects. Concomitant head and mandibular movements were assessed in the sagittal plane by allocating several reference points in the head (upper incisor, cranial base, occipital and parietal points) and a mandibular incisor point during maximal mouth open-close movements. Then, the magnitude and inclination of the vectors of motion in each reference point during the opening phase were calculated. The instantaneous centre of rotation was defined as the point showing the least amount of motion in a determined area around each head reference point. The mandibular incisal point and the maxillary incisal point showed concomitant movements; that is, during opening the mandibular point moved downwards and the maxillary incisor point upwards. Making a large jaw opening movement caused an inferior-anterior displacement in the O point, a posterior-inferior displacement of the P point, and an anterior-superior displacement in the C point in all subjects. During jaw closing all points followed a trajectory opposite to that described above. In other words, during opening the head moved clockwise and counter-clockwise during closing, at least in the sagittal plane of the subjects' left side. These results suggest that the head undergoes a rotation-like sagittal movement during mouth opening whose rotation centre seems to be located above the cranial base point, which was set close to the centre of mass of the head. However, its location varies according to the magnitude of mouth opening.

Adult↗
PubMed2002

The rotational technique with a partially inflated laryngeal mask airway improves the ease of insertion in children.

BACKGROUND: This study compared the ease of insertion of the laryngeal mask airway (LMA) with a partially inflated cuff using the standard 'nonrotational' technique versus the rotational technique. METHODS: One hundred and forty-five children undergoing anaesthesia using the LMA were randomly assigned to either method. The cuff was partially inflated in both groups. The ease of insertion was assessed by the time taken to complete the LMA insertion, the number of attempts before successful placement and the occurrence of complications. RESULTS: The success rate of insertion at the first attempt was higher in the rotational technique group (99% versus 79%, P < 0.05). All patients in the rotational group had the mask inserted within two attempts. On the other hand, three patients had the mask inserted on the first attempt with the rotational technique after three unsuccessful attempts by an anaesthesiologist with the standard 'nonrotational' technique. Insertion technique made no difference on insertion time. CONCLUSIONS: The rotational technique was associated with a higher success rate for insertion and a lower incidence of complications in children. Using the rotational technique with a partially inflated cuff could be the first-choice approach in paediatric patients.

Anesthesia↗
PubMed2000

Forearm rotation alters interosseous ligament strain distribution.

Recent interest in reconstruction of the interosseous ligament (IOL) of the forearm has led to questions concerning optimal placement of the reconstructive graft as well as the ideal rotational position of the forearm during graft tensioning. We therefore studied the strain distribution in the IOL to determine which fibers are strained in different positions of forearm rotation. Five cadaveric human forearms were subjected to compressive axial load (simulating power grip) and the strain values across the entire IOL were measured with the forearm in neutral, supination, and pronation. The strain distribution in the IOL changed with forearm rotation. The highest overall strain was found in neutral. In neutral and pronation, higher strain was observed in the proximal region of the IOL. In supination, however, higher average strain was seen in the distal region of the IOL. These results suggest that a reconstructive graft placed in the proximal region of the IOL and tensioned in neutral rotation would provide balanced constraint in different positions of forearm rotation. A graft placed in the distal region and tensioned in forearm neutral, however, may limit forearm rotation.

Adolescent↗
PubMed1999

In vivo MR studies of dynamic changes in the interosseous membrane of the forearm during rotation.

In vivo dynamic changes in the interosseous membrane (IOM) during forearm rotation were studied using magnetic resonance imaging (MRI). The right forearms of 20 healthy volunteers were examined in five different rotational positions. Axial slices were obtained at the proximal quarter, the middle and the distal quarter of the forearm. The changes in shape of the IOM during rotation were observed in an axial MR plane. For each image, we measured the interosseous distance and the length of the interosseous membrane. Images of the tendinous and membranous parts of the IOM could be differentiated by thickness. There were minimal dynamic changes in the tendinous part on the MRI while the membranous part showed numerous changes during rotation. The interosseous distance and the length of the interosseous membrane were maximum from a neutral to a slightly supinated position. The tendinous part is considered to be taut during rotation to provide stability between the radius and the ulna, but the membranous part which is soft, thin and elastic, allows smooth rotation.

Elasticity↗
PubMed2004

Shoulder rotation characteristics in professional tennis players.

Aim of this study was to assess the glenohumeral joint internal and external rotational range of motion using an ultrasound based kinematic measurement device. Twenty-seven male professional tennis players were bilaterally measured for internal and external rotation at 90 degrees of shoulder abduction while avoiding scapulothoracic motion. The control group consisted of 20 asymptomatic volunteers not involved in overhead sports activities. The dominant arm (playing arm) had a significantly greater range of external rotation than the non-dominant arm, while their internal rotation showed a significant deficit as compared to the non-dominant arm. The dominant arm total rotational range of motion was also significantly reduced in comparison to the non-dominant arm and to the controls. No significant difference was found between the dominant and non-dominant extremity in the control group. For objective measurement of glenohumeral rotational range of motion ultrasound based real time motion analysis is a new application for the diagnostic testing of specific shoulder parameters in orthopedics and sports physical therapy. It is therefore concluded that the specific methodology aiming at isolated glenohumeral motion may have clinical application for the development of rehabilitation and preventative programs.

Adult↗
PubMedDate not supplied

Postoperative subcoracoid impingement syndrome in patients with rotator cuff tear.

Impingement of the tendinous rotator cuff on the coracoid process (subcoracoid impingement syndrome) has rarely been reported as a cause of pain after surgery for rotator cuff tear. We evaluated clinical features, surgical results, and histopathology findings of resected coracoid processes in patients with subcoracoid impingement syndrome after anterior acromioplasty and management of rotator cuff tear. Pain at the anterior aspect of the shoulder, localized tenderness of the coracoid process, anterior shoulder pain on horizontal adduction testing, and positive subcoracoid block suggest subcoracoid impingement syndrome. Postoperative subcoracoid impingement syndrome was investigated in 11 of 216 cases with rotator cuff surgery. The average patient age at the time of surgery was 61.2 y (range, 28-78 y). Coracoplasty (partial resection of the posterolateral side of the coracoid process) was performed in 9 shoulders that had not responded to a 6-month regimen of conservative treatment. Complete pain relief was achieved in all cases. Histopathologic findings revealed hypertrophic changes of the fibrocartilage layer at the posterior aspect of the resected coracoid process. We concluded that subcoracoid impingement syndrome was an important factor in unsuccessful rotator cuff surgery and recommend that coracoplasty be performed on patients with symptoms of subcoracoid impingement syndrome after management of the rotator cuff tear.

Adult↗
PubMed2002

Perception of objects that are translating and rotating.

The motion of objects that are both translating and rotating can be decomposed into an infinite number of translational and rotational combinations. How, then, do such stimuli routinely elicit specific percepts and behavioral responses that are usually appropriate? A possible answer is that motion percepts are fully determined by the probability distributions of all the possible correspondences and differences in the stimulus sequence. To test the merits of this conceptual framework, we investigated the perceived motion elicited by a line that is both translating and rotating behind an aperture. When stimuli are presented such that a particular sequence of appearance and disappearance occurs at the aperture boundary, subjects report that the line is rotating only; furthermore, the perceived centers of rotation appear to describe a cycloidal trajectory, even when one aperture shape is replaced by another. These and other perceptual effects elicited by translating and rotating stimuli are all accurately predicted by the probability distribution of the possible sources of the physical movements, supporting the conclusion that motion perception is indeed generated by a wholly probabilistic strategy.

Discrimination Learning↗
PubMed1989

Photolysis of a photolabile precursor of ATP (caged ATP) induces microsecond rotational motions of myosin heads bound to actin.

To test the proposal that ATPase activity is coupled to the rotation of muscle cross-bridges (myosin heads attached to actin), we have used saturation-transfer EPR to detect the rotational motion of spin-labeled myosin heads (subfragment 1; S1) bound to actin following the photolysis of caged ATP (a photoactivatable analog of ATP). In order to ensure that most of the heads were bound to actin in the presence of ATP, solutions contained high (200 microns) actin concentrations and were of low (36 mM) ionic strength. Sedimentation measurements indicated that 52 +/- 2% of the spin-labeled heads were attached in the steady state of ATP hydrolysis during EPR measurements. Five millimolar caged ATP was added to the actin-S1 solution in an EPR cell in the dark, with no effect on the intense saturation-transfer EPR signal, implying a rigid actin-S1 complex. A laser pulse produced 1 mM ATP, which decreased the signal rapidly to a brief steady-state level that indicated only slightly less rotational mobility than that of free heads. After correcting for the fraction of free heads, we conclude that the bound heads have an effective rotational correlation time of 1.0 +/- 0.3 microseconds, which is about 100 times shorter (faster) than that in the absence of ATP. To our knowledge, this is the first direct evidence that myosin heads undergo rotational motion when bound to actin during the ATPase cycle. It is likely that similar cross-bridge rotations occur during muscle contraction.

Actins↗
PubMed2004

Observation of calcium-dependent unidirectional rotational motion in recombinant photosynthetic F1-ATPase molecules.

ATP hydrolysis and synthesis by the F(0)F(1)-ATP synthase are coupled to proton translocation across the membrane in the presence of magnesium. Calcium is known, however, to disrupt this coupling in the photosynthetic enzyme in a unique way: it does not support ATP synthesis, and CaATP hydrolysis is decoupled from any proton translocation, but the membrane does not become leaky to protons. Understanding the molecular basis of these calcium-dependent effects can shed light on the as yet unclear mechanism of coupling between proton transport and rotational catalysis. We show here, using an actin filament gamma-rotation assay, that CaATP is capable of sustaining rotational motion in a highly active hybrid photosynthetic F(1)-ATPase consisting of alpha and beta subunits from Rhodospirillum rubrum and gamma subunit from spinach chloroplasts (alpha(R)(3)beta(R)(3)gamma(C)). The rotation was found to be similar to that induced by MgATP in Escherichia coli F(1)-ATPase molecules. Our results suggest a possible long range pathway that enables the bound CaATP to induce full rotational motion of gamma but might block transmission of this rotational motion into proton translocation by the F(0) part of the ATP synthase.

Actins↗
PubMed2004

Imagination of body rotation can induce eye movements.

OBJECTIVE: Several studies have shown that spatiotemporal aspects of motion are stored and can be retrieved with the use of vestibular and somatosensory cues. The purpose of this study was to examine whether intentional imagination of body rotation can induce oculomotor activity similar to the typical vestibulo-ocular reflex (VOR). MATERIAL AND METHODS: Normal subjects without known vestibular and/or oculometric abnormalities were instructed to imagine a sensation of accelerating body rotation in the horizontal plane (rightward or leftward) while sitting in darkness with closed eyes, using only vestibular and somatosensory cues and not imaginary visual cues. Eye movements were recorded during the imagery session and also during a full, routine electronystagmography (ENG) test. All subjects selected for this study showed normal results in the ENG test, and none of them had gaze-evoked or end-point nystagmus. RESULTS: In response to imaginary rotations, horizontal eye movements were found in 91/121 recordings (75%) in 10 subjects. A typical pattern of nystagmus (0.3-3 Hz, 3-30 degrees /s maximal speed of slow component) was recorded in 53% of mental rightward rotations and 49% of leftward rotations. The fast component was always in the direction of the imaginary rotation (similar to a normal VOR). Other types of eye movement comprised either contralateral eye drift ( approximately 17% of trials) or macro square waves. In 25% of the recordings no definite eye movements could be detected during the mental maneuvers. CONCLUSION: These mentally induced eye movements seem to be due to a cortical process which can affect the normal input to the brainstem nuclei. A possible mechanism is discussed. This phenomenon may serve as an objective measurement of mental activity, may be used for testing the cognitive resources of patients and can probably be used for enhancing the rehabilitation process after acute vestibular insult.

Adolescent↗