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At least 595 records · Page 33Linked to original sources
PubMed1992

Kinematic analysis of upper limb trajectories in Parkinson's disease.

The purpose of this study was to analyze the kinematic properties of upper limb trajectories in Parkinson's disease (PD) patients and to investigate the role of visual feedback from the moving limb. Beyond the characteristic bradykinesia, PD patients differed from controls by generating hand trajectories with asymmetrical velocity profiles that lacked smoothness and were composed of a short initial accelerative phase, followed by a prolonged interval composed of alternating decelerative and accelerative phases. In both groups, the reaction times for movements directed away from the body were longer than for movements directed toward the body; this effect was accentuated in PD. In both groups, initial peak accelerations were significantly larger for distally as compared to proximally directed movements. In the absence of visual feedback from the limb a deterioration in the accuracy of reaching the target was observed in both control and PD patients only for distally directed movements. However, this deterioration and the effect of target location on final accuracy was substantially larger in PD. Taken together, our study suggests that in PD visual information is continuously relied upon for ongoing movement correction, therefore accentuating the bradykinesia. The deficit in final accuracy in the absence of visual feedback reflects the important role played by the basal ganglia in sensorimotor integration.

Acceleration↗
PubMed1995

Predicting the kinematics and kinetics of gait based on the optimum trajectory of the swing limb.

An algorithm was developed to predict the minimum energy consumption trajectory of the swing limb. The method of dynamic programming, a multistage optimization method, was applied to generate the optimum trajectory of the swing ankle which minimized the mechanical energy required to generate the moments of the joints of the lower extremities during the single support phase of gait. Predictions and measurements of gait were compared for six healthy subjects. The predicted hip and knee flexion angles of the swing limb were not significantly different from those experimentally measured except for hip flexion at times greater than 75% of the swing period. The predicted ground reaction forces were not significantly different from the measured ground reaction forces. Furthermore, the moments about the joints were not significantly different from those computed using the measured ground reaction forces and kinematics of the limbs. The results of this study support the hypothesis that human gait is energy efficient.

Acceleration↗
PubMed1993

Lymphocyte locomotion in three-dimensional collagen gels. Comparison of three quantitative methods for analysing cell trajectories.

We evaluated three different quantitative evaluation methods for lymphocyte locomotion in three-dimensional collagen gels: (1) the length of the two-dimensional migration path (distance migrated) was compared to (2) the resulting average displacement from the starting to the end point and (3) the displacement of the furthest migrating population (cells with high displacement). Locomotion of immunomagnetically isolated human CD4+ and CD8+ peripheral blood lymphocytes suspended in type I collagen gels was recorded using time-lapse videomicroscopy. Paths of randomly selected locomoting cells were digitized, reconstructed and quantitatively analysed. For spontaneously locomoting CD4+ and CD8+ lymphocytes (90 min observation period) the mean total distance migrated was 10.0 +/- 3.7 microns/min (CD4+; n = 114 cells) and 5.6 +/- 3.3 microns/min (CD8+; n = 90 cells). The mean displacement from the individual starting point amounted to 1.3 +/- 0.7 micron/min for CD4+ and 1.1 +/- 0.7 micron/min for CD8+ cells, thus representing only 5-25% of the total migration path (index range displacement/distance migrated: 0.13-50%). Incubation with interleukin-8 and/or receptor blocking by monoclonal antibodies against VLA-2 (Gi9) or VLA-4 (HP2/1) integrins significantly altered the mean length of the migration paths for six out of ten different experimental conditions. Average displacement or displacement of the most active cells detected significant changes in two and three out of ten samples. Whereas the interleukin-8 induced locomotory changes were correctly represented by end point determination, relatively slight but significant modulation in lymphocyte behaviour by anti-integrin antibodies was revealed solely by analysis of the complete cell trajectory. In conclusion, the cell trajectory may represent a sensitive method for evaluating induced subtle changes in lymphocyte locomotory characteristics.

CD4-Positive T-Lymphocytes↗
PubMed1992

Trajectory surgical guide stent for implant placement.

This article describes a new implant placement surgical guide that gives both implant location and trajectory to the surgeon. Radiopaque markers are placed on diagnostic dentures and a lateral cephalometric radiograph is made that shows the osseous anatomy at the symphysis and the anterior tooth location. The ideal implant location and trajectory data are transferred to a surgical stent that programs the angle and location of the fixtures at time of surgery. The stent has the additional benefit of acting as an occlusion rim, a mouth prop, and tongue retractor. Use of this stent has resulted in consistently programming the placement of implant fixtures that are prosthodontically ideal.

Dental Implantation, Endosseous↗
PubMed1994

Walking trajectory and hand movements in unilateral left neglect: a vestibular hypothesis.

This is the first systematic study of walking trajectories in unilateral neglect. Six patients with unilateral left neglect approached and walked through a doorway, and all six deviated to the right of centre when doing so. Four out of six significantly centred their walking trajectories by making left hand movements while approaching the doorway. The group effect of walking with no hand movements vs walking with hand movements was statistically significant. Age-matched control patients showed a similar but significant smaller rightward deviation. The results are interpreted in terms of recent research in limb activation effects on neglect (Robertson and North, Neuropsychologia 30, 553-563, 1992), and also in the light of research showing close anatomical correspondence between the cortical projections of the vestibular nerve on the one hand, and the hand/arm representational fields of the central sulcus on the other.

Adult↗
PubMed1986

Retinotectal projection in reeler mutant mice: relationships among axon trajectories, arborization patterns and cytoarchitecture.

The distribution of axons in the midbrain and thalamus of homozygous reeler mutant mice is anomalous. The cytoarchitecture of these regions is normal. In the normal mouse SC there is a distinct SO in which fascicles of retinotectal axons pass caudally before terminating in the overlying SGS. In reeler, by contrast, fascicles of retinotectal axons are distributed through the entire thickness of SGS as well as through SO. There are also abnormalities of fiber pattern in the thalamus, most notably in the region of the dorsal nucleus of the LGd. Retinotectal axon trajectory and patterns of terminal arborization in reeler and normal animals were compared by single-fiber HRP axonography. In normal mice, two distinct morphological classes of retinotectal axons form focal terminal arborizations at different radial levels in the superficial layers of the SC. Class U axons are of relatively small diameter and terminate in upper portions of SGS. Class L1 axons are of larger diameter and form terminal arbors which are confined to SO and deeper regions of SGS. Axons of both classes ascend to their terminal zones from parent axons which course through SO. Similarly, in reeler mice axons of both large and small diameter can be distinguished. However, many axons of both classes pass caudally in anomalous fascicles distributed through the full thickness of SGS and descend to terminate. Other axons pass in normal fashion in SO and ascend to terminate in SGS. Regardless of their trajectories, the small axons terminate superficially in SGS while the thick axons terminate deeper in SGS and/or SO, as in normal mice. These findings suggest that the ingrowth of afferents and the formation of terminal arbors are regulated by different mechanisms and that fiber architecture and cytoarchitecture are regulated by different mechanisms. It is not known if the anomalous fiber pattern in reeler adults arises in development through a defect in initial patterns of axon fasciculation or from a failure of axon elimination.

Animals↗
PubMed1993

Plasticity of avian mesencephalic polarity revealed by trajectories of tectofugal axons.

In normal E6 (sixth day of incubation) quail mesencephalons, circumferential axons originate in the tectum (the dorsal part of a mesencephalon), course in a ventral direction and split into three trajectories in the ventral region of the mesencephalon; two of them turned on the ipsilateral side of the mesencephalon, one rostrally and the other caudally, while the third crossed the ventral midline and turned caudally on the contralateral side. In this study, we examined whether the ventral part of the mesencephalon has plasticity in its rostrocaudal polarity formation. We transplanted quail mesencephalons at the 9-10 somite stage (E2) with reversed rostrocaudal orientation prior to axon outgrowth. In reversely transplanted mesencephalons, circumferential axons at E6 took the same trajectory pattern as that of normal embryos; one turned rostrally and the second caudally on the ipsilateral side, and the third one turned caudally on the contralateral side. These results indicate that the rostrocaudal polarity of the mesencephalon is not fixed at E2, and that it may develop under the influence of tissues surrounding the mesencephalon.

Animals↗
PubMed1995

Use of TSAR as a new tool to analyze the molecular dynamics trajectories of proteins.

There is a lack of tools to analyze simulations of protein molecular dynamics quantitatively. Our aim is to use calmodulin, a prototypical calcium-binding protein, to describe a strategy and some tools for extracting relevant information from dynamics calculations. Our main conclusions are as follows: Autocorrelation vectors may be used to represent a 3D conformation in an n-dimensional space, where n is variable (n < or = 20-30). On such a transformation, classic statistical tools (PCA, clustering, etc.) may be used to differentiate or characterize dynamics trajectories quantitatively. TSAR, an integrated package used for quantitative structure-activity relationships, is well suited (after minor modifications) for such a purpose. Finally, this type of strategy is able to point out the effects of the solvent screening parameters of the Amber software on the dynamics trajectories of calmodulin.

Calmodulin↗
PubMed1995

Moments at the L(5)/S(1) joint during asymmetrical lifting: effects of different load trajectories and initial load positions.

The purpose of this study was to examine the reaction moments at L(5)/S(1) about the three orthogonal orthopaedic axes on the trunk when performing asymmetrical lifting tasks under six experimental conditions. The first three conditions were three lifting modes referring to different load trajectories (diagonal, extension then twisting, twisting then extension). The next three conditions were three lifts referring to different initial load positions (90 degrees, 45 degrees, 0 degrees ). Ten male volunteers (mean age 23.4 years) participated in the study. The mass of the load was 11.6 kg and two shelves were used: a low shelf of 22 cm from which the load was removed and a high shelf of 80 cm onto which the load was laid down following the manoeuvre. A dynamic 3D multisegment model was used to compute spinal loadings. The maximum reaction moments generated at the joint for the three load trajectories and for the three initial load positions were approximately of the same magnitude. On the other hand, significant differences were observed in the trunk orientation when the maximal moment was generated. Symmetrical trunk positions appeared to be more advantageous because of the reduction in the capability of maximal extension force in asymmetric trunk posture. A possible alternative for avoiding excessive stress on the back in asymmetric trunk posture may be to keep the shoulders parallel to the ground. RELEVANCE: Three-dimensional studies of the resulting moments at L(5)/S(1) when performing lifting activities are not common, particularly when the tasks include muscular exertions in trunk flexion combined with either twisting or lateral bending. This type of analysis is particularly important since asymmetries have been identified as risk factors for low back disorders. The knowledge of reaction moments in relation to postures are essential to understand the mechanism of low back pain.

Journal Article↗
PubMed1994

Particle trajectories in seeds of Lactuca sativa and chromosome aberrations after exposure to cosmic heavy ions on Cosmos Biosatellites 8 and 9.

The potentially specific importance of the heavy ions of the galactic cosmic radiation for radiation protection in manned spaceflight continues to stimulate in situ, i.e., spaceflight experiments to investigate their radiobiological properties. Chromosome aberrations as an expression of a direct assault on the genome are of particular interest in view of cancerogenesis being the primary radiation risk for man in space. In such investigations the establishment of the geometrical correlation between heavy ions' trajectories and the location of radiation sensitive biological substructures is an essential task. The overall qualitative and quantitative precision achieved for the identification of particle trajectories in the order of approximately 10 micrometers as well as the contributing sources of uncertainties are discussed. We describe how this was achieved for seeds of Lactuca sativa as biological test organisms, whose location and orientation had to be derived from contact photographies displaying their outlines and those of the holder plates only. The incidence of chromosome aberrations in cells exposed during the COSMOS 1887 (Biosatellite 8) and the COSMOS 2044 (Biosatellite 9) mission was determined for seeds hit by cosmic heavy ions. In those seeds the incidence of both single and multiple chromosome aberrations was enhanced. The results of the Biosatellite 9 experiment, however, are confounded by spaceflight effects unrelated to the passage of heavy ions.

Chromosome Aberrations↗
PubMed1991

Discrimination of motion in depth trajectory following acute alcohol ingestion.

Evoked potentials were recorded at four scalp sites O1, O2, T5, T6; before and after the consumption of one of two alcohol dose levels, to the occurrence of disparate stimuli in dynamic random dot stereograms. Twenty young adult subjects, all of whom had vision which was normal or corrected to normal, were randomly assigned to the two dosage groups. Subjects viewed stimuli which embodied crossed disparity and followed one of three trajectories in depth. The task was to distinguish between and identify, by specific button presses, these trajectories. One half of the stimuli were presented with monocular cues to motion in depth (dark condition); in the remainder only stereoscopic depth information was available (uniform condition). Responses to both conditions showed alcohol-related reduction of evoked responses across all sites. It was concluded that the visual systems associated with the processing of motion in depth were susceptible to alcohol effects, as revealed by reductions in the amplitude of evoked responses.

Adult↗
PubMed1989

Effects of click polarity on auditory brain-stem potentials: a three-channel Lissajous' trajectory study.

Three-channel Lissajous' trajectories (3CLTs) of the auditory brain-stem evoked potentials (ABEP) were recorded from 16 adult subjects (28 ears) in response to rarefaction (R), condensation (C) and alternating polarity (A) clicks. 3CLTs were analysed and described in terms of their geometrical measures. All 3CLTs included 5 planar segments (named 'a', 'b', 'c', 'd' and 'e') whose latencies, durations, orientations, sizes and shapes were not affected by click polarity. Occasionally, planar segment 'd' was not defined, and its absence was parallelled by the absence of peak IV in the Vertex-Mastoid records. A small (0.03 microV), but significant increase was found in the trajectory amplitude of planar segment 'e' in C clicks. The effects of click polarity on 3CLT observed in this study suggest that some previously described ABEP changes with click polarity were the result of interactions between electrode positions and relative contributions of overlapping generators. The effects on the fourth and fifth ABEP components may be the results of changes in the temporal overlap of the activity of their generators.

Acoustic Stimulation↗
PubMed1990

Three-channel Lissajous' trajectories of auditory brainstem evoked potentials: contribution of fast and slow components to planar segment formation.

Three-Channel Lissajous' Trajectories (3CLT) of Auditory Brainstem Evoked Potentials (ABEP) to clicks were obtained after finite impulse response filtering in three frequency bands. These bands were chosen to replicate the widely used passband (100-3000 Hz) and to selectively enhance the definition of the 'pedestal' (10-240 Hz) or the first, third and fifth components (240-483 Hz). Quantitative measures of 3CLT were calculated to describe apex latencies, planar segment orientations, durations, trajectory amplitude peaks and their latencies. In addition, dipole moments at the latencies of apical points along 3-CLT were calculated. The planarity of ABEP 3-CLT segments persisted after selective enhancement of the 'pedestal' or the first, third and fifth components. These results rule out the suggestion that planarity of ABEP segments results from the interaction of the 'pedestal' with the superimposed faster components. These results demonstrate summation of 3-CLT planar segments ('a' 'c' and 'e' with the 'pedestal') to form new segments (wide-band 'a', 'c' and 'e'). With the exception of 'c', planar segments and the equivalent dipole moments associated with apexes did not change orientations across passbands. The effects of passband on the orientation of planar segment 'c' and the dipole moment of its apex are explained by its superimposition on the 'pedestal' in the wide-band records. A similar analysis of ABEP to clicks as compared to low-frequency stimuli (high-pass masked clicks) revealed no change in planarity nor in plane parameters. These results are compatible with the suggestion that the generators of the first, third and fifth ABEP components are curved fiber tracts. The planarity of the slow 'pedestal' may be due to the summation of slow synaptic potentials in auditory brainstem nuclei. These findings indicate that the generators of ABEP are composites that may be separated by selective lesion studies.

Acoustic Stimulation↗
PubMed1993

Determination of high LET cosmic particles' trajectories for space radiobiological studies.

During IML-1 mission, we carried out space experiments on radiobiological effect of a single HZE cosmic particle. In the experiment, the precise determination of the distance between the center of the particle trajectory and the individual biological objects around it is an indispensable condition. For the detection of HZE particles CR-39 track detectors were used and analyzed by the video image processing. The positions of biological objects in relation to a particle trajectory were measured by referring to the laser grid marks which were printed on the surface of CR-39 detector. We describe such an experimental method and report the applicability of this method.

Bacillus subtilis↗
PubMed2005

Joint trajectories of gambling, alcohol and marijuana use during adolescence: a person- and variable-centered developmental approach.

The usefulness of Moffitt's (1993) [Moffitt, T. E. (1993). Adolescence-limited and life-course-persistent antisocial behavior: A developmental taxonomy. Psychological Review, 100, 674-701.] theory of antisocial behavior was examined regarding gambling, alcohol and marijuana use. We assessed 903 Caucasian boys' developmental trajectories of these behaviors annually from age 11 through age 16. Severity of problems with these behaviors were assessed at ages 17 and 23. As correlates of these behaviors, teacher-rated personality and self-reported parenting were assessed at age 10. Self-reported autonomy was measured at ages 11 and 14. A cluster analysis on the correlates yielded two clusters. Membership in the cluster without adult problems was associated with either late onset of gambling and/or alcohol use trajectories or consistently low involvement in each of the behaviors. This cluster may correspond to Moffitt's adolescence-limited group and uninvolved adolescents, respectively. Membership in the cluster with subsequent adult problems was associated with early initiation of at least one of the three behaviors and involvement in each of them during adolescence. This cluster may correspond to Moffitt's life-course-persistent group. Findings indicate that early assessment of correlates used in the cluster analysis may be useful for screening and preventive purposes.

Adolescent↗
PubMed2004

The influence of Tai Chi training on the center of pressure trajectory during gait initiation in older adults.

OBJECTIVE: To determine if a program of intense Tai Chi exercise that has been shown to reduce the risk of falling in older adults improves postural control by altering the center of pressure (COP) trajectory during gait initiation. DESIGN: Before-after trial. SETTING: Biomechanics research laboratory. PARTICIPANTS: Twenty-eight older adults transitioning to frailty who participated in either a 48-week intervention of intense Tai Chi training or a wellness education (WE) program. INTERVENTIONS: Eight Tai Chi forms emphasizing trunk rotation, weight shifting, coordination, and narrowing of lower-extremity stance were taught twice weekly. WE program participants met once a week and received lectures focused on health. Main outcome measures The COP was recorded during gait initiation both before and after the 48-week intervention by using a forceplate sampling at 300 Hz. The COP trajectory was divided into 3 periods (S1, S2, S3) by identifying 2 landmark events. Displacement and average velocity of the COP trace in the anteroposterior (x) and mediolateral (y) directions, as well as smoothness, were calculated. RESULTS: Tai Chi training increased the posterior displacement of the COP during S1 and improved the smoothness of the COP during S2. CONCLUSIONS: Tai Chi improved the mechanism by which forward momentum is generated and improved coordination during gait initiation, suggesting improvements in postural control.

Aged↗
PubMed2006

PTSD symptom trajectories: from early to chronic response.

This study aimed to identify posttraumatic stress disorder (PTSD) symptom trajectories across the first 12 months following traumatic injury. Three hundred and seven consecutively admitted injury survivors were assessed for severity of PTSD symptoms just prior to discharge, and at 3 and 12 months postinjury. Growth modeling was used to determine the curve that best fit the trajectory for each symptom cluster over the 12-month period. Individuals with 12-month PTSD showed significantly higher re-experiencing, arousal, and avoidance symptoms at eight days posttrauma relative to those without, and these symptoms escalated over time. Those without PTSD maintained their relatively low symptom levels. These findings highlight that individuals who will go onto develop PTSD have a distinctly different symptom course than those who recover.

Adaptation, Psychological↗
PubMed2005

Relation between saccade trajectories and spatial distractor locations.

This study shows that the exact spatial location of a distractor can have a modulatory influence on saccade trajectories. Distractors close to the target evoke saccade trajectories that are directed towards the distractor, while distractors close to fixation result in saccades that are directed away from the distractor. This finding questions the idea that target positions are coarsely coded in the superior colliculus.

Functional Laterality↗