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Trajectories of human granulocytes.

The spatial trajectories of human granulocytes moving on glass in two dimensions under an isotropic medium may be characterized as realizations of a correlated walk. The present model is similar to an earlier one for slime-mold amebae. The correlation from step to step is essentially via the relative angle theta, represented for granulocytes as a random variable with a symmetric bimodal density. As the cells age, they appear to turn less and the degree of correlation increases. Even under chemotaxis the angle theta and the step length r appear to be statistically independent.

Cell Movement↗

Rational analyses of organelle trajectories in tobacco pollen tubes reveal characteristics of the actomyosin cytoskeleton.

To gain insight into the characteristics of organelle movement and the underlying actomyosin motility system in tobacco pollen tubes, we collected data points representing sequential organelle positions in control and cytochalasin-treated cells, and in a sample of extruded cytoplasm. These data were utilized to reconstruct approximately 900 tracks, representing individual organelle movements, and to produce a quantitative analysis of the movement properties, supported by statistical tests. Each reconstructed track appeared to be unique and to show irregularities in velocity and direction of movement. The regularity quotient was near 2 at the tip and above 3 elsewhere in the cell, indicating that movement is more vectorial in the tube area. Similarly, the progressiveness ratio showed that there were relatively more straight trajectories in the tube region than at the tip. Consistent with these data, arithmetical dissection revealed a high degree of randomlike movement in the apex, lanes with tip-directed movement along the flanks, and grain-directed movement in the center of the tube. Intercalated lanes with bidirectional movement had lower organelle velocity, suggesting that steric hindrance plays a role. The results from the movement analysis indicate that the axial arrangement of the actin filaments and performance of the actomyosin system increases from tip to base, and that the opposite polarity of the actin filaments in the peripheral (+-ends of acting filaments toward the tip) versus the central cytoplasm (+-ends of actin filaments toward to the grain) is installed within a few minutes in these tip-growing cells.

Actomyosin↗

Balancing personal and family trajectories: an international study of dual-earner couples with pre-school children.

In general, the nursing literature neglects healthy families and depictions of families are dominated by systems and developmental theory. The preponderance of dual-earner families has changed the meaning of family, however, nurses have given minimal attention to how women and men attend to work and home. Balancing personal and family trajectories is a substantive theory that accounts for how Canadian and English couples with pre-school children managed work and family life. The theory describes their efforts to maximize personal and family development, by using processes that attempted to support and sustain individual and family health, happiness, and fulfillment.

Adaptation, Psychological↗

Influence of body segment parameters and modeling assumptions on the estimate of center of mass trajectory.

This study sought to determine the effect of inaccuracies in body segment parameters and modeling assumptions on the estimate of antero-posterior center of mass (COM) trajectory. Four different methods, one based on segmental kinematics, and three methods based on kinetic recordings were compared via simulation. Kinematic patterns (quiet stance, ankle-related sway, hip-ankle-related sway, sit-up and sit-up-sit-down) were tested with a 2D four-link model of the body and the ground reaction force vector was obtained by inverse dynamics. Errors in the estimation of body segment parameters were simulated by applying a +/-10% variation to one or more parameters at a time. These errors propagated differently to the COM estimated location between methods, between parameters within the same method, and between tasks. The kinematics-based method was the most sensitive to body segment parameters, with special regards to segment lengths and head-arms-trunk parameters. Root mean square error between estimated and simulated COM location reached 19mm in balance-related tasks and 38.3mm in sit-up-sit-down. The kinetics-based methods were largely less sensitive to inaccuracies in body segment parameters. In particular, the technique proposed by Zatsiorsky and King (J. Biomech. 31 (1998) 161), was completely insensitive to segment parameters. On the other hand the kinetics-based methods showed an intrinsic estimation error, due to the underlying model assumptions. The methods based on the double integration of horizontal force had better outcomes with tasks challenging such assumptions, with a maximal error in COM location of 15mm in the sit-up-sit-down. The method proposed by Shimba (J. Biomech. 17 (1984) 53) showed the best trade-off between sensitivity to body segment parameters and estimation performances given the ideal test conditions.

Biomechanical Phenomena↗

Early cerebro-craniofacial dysmorphogenesis in schizophrenia: a lifetime trajectory model from neurodevelopmental basis to 'neuroprogressive' process.

Understanding the temporal origin(s) of schizophrenia, through specifying the earliest identifiable pathology, might indicate when to look for etiological factor(s), what their nature might be, and how course of illness might evolve from these origins. From this premise, earlier formulations are elaborated to offer a rigorously data-driven model that roots schizophrenia in cerebro-craniofacial dysmorphogenesis, particularly along the mid-line but involving other structures, over weeks 9/10 through 14/15 of gestation. However, a brain that has been compromised very early in fetal life is still subject to the normal endogenous programme of developmental, maturational and involutional processes on which a variety of exogenous biological insults and psychosocial stressors can impact adversely over later pregnancy, through infancy and childhood, to maturation and into old age, to sculpt brain structure and function; it should be emphasised that the effects of such endogenous programmes and exogenous insults on such an already developmentally-compromised brain may be different from their effects on a brain whose early fetal origins were unremarkable. From these early origins, a lifetime trajectory model for schizophrenia from developmental basis to 'neuroprogressive' process is constructed. Thereafter, consideration is given to what the model can explain, including cerebral asymmetry and homogeneity, what it cannot explain, what empirical findings would challenge or disprove the model, what cellular and molecular mechanisms might underpin the model, and what are its implications.

Brain↗

An ellipsoidal trajectory model for measuring the line of sight.

The relationship between the amount of rotation of the eyeball and the amount of rotation of the line of sight was investigated. The planar model and ellipsoidal model were compared as the trajectory of the center of the pupil. An evaluation of precision was carried out by measuring the discrepancy between the direction of the target and the estimated direction of the line of sight. The experimental results showed that the planar model was more precise than the ellipsoidal model. The center of rotation of the eyeball seems to translate along the oblique rotation of the eyeball.

Eye Movements↗

Predicting intraindividual self-concept trajectories during adolescence.

The level and stability of both global and domain-specific self-concepts was examined in a study of 253 adolescents, aged 11-20. Intraindividual self-concept trajectories were calculated through growth curve modeling. Six of the self-concept domains were stable over time. In the remaining three domains, there was a significant increase in perceived competency. Growth curve modeling highlighted individual differences in both level and change in self-concept for each of the domains. These differences were partially accounted for by the adolescents' age and gender, suggesting that these variables are important determinants of adolescent self-concept.

Adolescent↗

Three-dimensional trajectories of the hippocampal rhythmic slow activity in the behaving rat.

Movement-concurrent rhythmic slow activity (RSA) was recorded by means of 3 pairs of bipolar electrodes which were arranged so that they orthogonally encompassed the dorsal hippocampus in the freely moving rat. The 3-channel data were combined by synchronously plotting them on independent voltage axes and the resultant 3-channel Lissajous' trajectory (3-CLT) was depicted in 3-dimensional microcomputer processing. A type of 3-CLT which traversed the surface of an ellipsoid with the long axis nearly perpendicular to the medial CA1 pyramidal layer, appeared most abundantly during walking. A 3-CLT depicting curves on a spherical surface was frequently produced during sitting. A linear 3-CLT of short duration was occasionally produced during rearing. These findings suggest that alteration of voltage axis specific to a behavior is possibly generated associating with the hippocampal RSA.

Animals↗

Axon trajectories in local circuits of the primary motor cortex in the macaque monkey (Macaca fuscata).

The intrinsic trajectories and terminal arbors of two axons and one horizontal axon collateral within the primary motor cortex (M1) were studied in the macaque monkey using injections of biotinylated dextran amine (BDA) into the putative primary forelimb motor cortex, and two-dimensional (2-D) reconstruction of the individually labeled axons and collateral. (1) A long collateral of the main axon from a large pyramidal cell in layer Vb of the putative forelimb area on the anterior bank of the central sulcus coursed horizontally anteriorly for 3 mm and formed a terminal arbor in layer III of M1. (2) The main axon of a pyramidal cell in layer IIIa+b of the putative forelimb area on the precentral gyrus descended into the white matter and then entered the anterior bank of the central sulcus to form a terminal arbor in layers III and V. (3) The main axon of a pyramidal cell in layer IIIc of the putative forelimb area on the precentral gyrus descended and bifurcated in the white matter. One branch entered the anterior bank of the central sulcus to form a terminal field in layer VI. These results indicate that some local axons and horizontal axon collaterals arising from M1 reach their single targets within M1 to form single terminal fields.

Animals↗

Fractal correlation of initial trajectory dynamics vanishes at the movement end point in human rapid goal-directed movements.

Many researchers have investigated the variability of discrete goal-directed movements. However, a possible time-dependent property for them has been ignored. We investigated the time-dependent property of the kinematic variability in human rapid goal-directed movements by using fractal analysis. The variability of the peak acceleration had fractal time correlation characterized by a non-negligible frequency-spectral exponent (beta=0.3). This beta value was reduced at the peak velocity (beta=0.2) and nearly reached zero at the peak movement amplitude, indicating that the variability became white noise with no time correlation. A similar result was observed in the progress of the positional trajectory. The functional significance of this phenomenon for the goal-directed task demand is discussed.

Acceleration↗

Hand trajectory formation during whole body reaching movements in man.

End-effector trajectory formation was studied during a reaching movement using the whole body. The movements of various parts of the body were measured with the optoelectronic ELITE system. Wrist reaching movement paths showed noticeable curvatures. The analysis of various marker onset latencies revealed that the wrist was the last to move, always after the head, knee or trunk, suggesting a subordinate role of the focal component with respect to the primary role of the equilibrium component. These results suggest that reaching wrist movements are subjected to whole-body equilibrium constraints in addition to constraints placed upon end-effector kinematics or the dynamic optimization of upper-limb movements.

Adult↗

Axonal trajectories of the nucleus reticularis gigantocellularis neurons in the C2-C3 segments in cats.

Axonal trajectories in the C2-C3 segments of the nucleus reticularis gigantocellularis neurons projecting to the lower cervical cord (C-RSNs) and excited monosynaptically from cortico- and tectofugal fibers were studied by mapping thresholds of antidromic excitation and intra-axonal staining in cats. The C-RSNs descended in various sites of the spinal funiculi, and the projection area of individual cells varied with the funicular location of the stem axon. C-RSNs descending in the ventrolateral funiculus (inRSNs) projected mainly to lamina VIII-IX, those descending in the lateral funiculus (IRSNs) mainly to laminae VI-VIII, and those descending in the contralateral funiculus (coRSNs) chiefly to laminae VIII-IX on that side. It is suggested that inRSNs and coRSNs mediate disynaptic effects from cortico- and tectofugal fibers to dorsal neck motoneurons bilaterally.

Animals↗

A longitudinal study of developmental trajectories to young adult cigarette smoking.

This study examined smoking trajectories between adolescence and adulthood in an African American cohort followed prospectively from first grade to age 32. We classified non-smokers, former smokers, current smokers/late adopters (initiated after age 18), and current smokers/early adopters (initiated before age 17). Results show that almost half of the population were currently smoking. Multiple logistic regression analyses showed that non-smokers differed most from the three smoking groups on social integration. Non-smokers were less likely to have left home before the age of 18, to have had more drug use parental supervision as an adolescent, to have moved less, and to attend church more frequently as an adult. Those current smokers who initiated early differed from the non-smokers and also from the former smokers and the current smokers who adopted smoking after the age of 18; they were more likely to be rated as aggressive or both shy and aggressive by their first grade teachers and to have drug problems as adults. Current smokers were less likely to attend church as adults than the non-smokers and former smokers. Neither mother's smoking or lifetime depression was related to smoking. The findings elucidate the contribution of factors over the life course that have an impact on smoking initiation, continuation, and cessation. They highlight the importance of targeting African American children and adolescents for prevention despite the fact that African American youth have the lowest rates of smoking across all ethnic groups. Possible interventions could be aimed at early aggressive behavior, parental supervision and monitoring, and other social integration efforts.

Adolescent↗

The effect of trajectory on the auditory motion aftereffect.

The auditory motion aftereffect (aMAE) can be induced in listeners after repeated presentation of a horizontally moving sound source. Aftereffects have also been found for the individual acoustic consequences of source motion such as amplitude or frequency modulations (AM, FM). No study, however, has investigated whether combining these changes would enhance the magnitude of the aMAE, which has appeared otherwise weak relative to its visual counterpart. AM, FM and binaural changes can occur simultaneously when sources move along common translational trajectories rather than the restricted rotational paths used in previous adaptation studies. This raises the question whether the observed weakness of the aMAE is due to the improper stimulation of units responsive to the entire macrostructure induced by translational motion. The hypothesis is tested here that if integrated motion detectors exist, then including lawful amplitude and frequency changes in adapting stimuli may enhance aftereffects. Though results indicate that interaurally moving stimuli in general induce an aMAE, the acoustic macrostructure of translational motion does not appear to increase the aftereffect. A simple cross-correlation model is used to illustrate that such acoustic modulations may allow brainstem auditory centers time to recover from adaptation to translational motion.

Acoustic Stimulation↗

Truncation artifact reduction in spectroscopic imaging using a dual-density spiral k-space trajectory.

Truncation artifacts arise in magnetic resonance spectroscopic imaging (MRSI) of the human brain due to limited coverage of k-space necessitated by low SNR of metabolite signal and limited scanning time. In proton MRSI of the head, intense extra-cranial lipid signals "bleed" into brain regions, thereby contaminating signals of metabolites therein. This work presents a data acquisition strategy for reducing truncation artifact based on extended k-space coverage achieved with a dual-SNR strategy. Using the fact that the SNR in k-space increases monotonically with sampling density, dual-SNR is achieved in an efficient manner with a dual-density spiral k-space trajectory that permits a smooth transition from high density to low density. The technique is demonstrated to be effective in reducing "bleeding" of extra-cranial lipid signals while preserving the SNR of metabolites in the brain.

Artifacts↗

Treatment compliance in the trajectory of treatment progress among offenders.

Research on drug treatment process has been limited, with most studies centering on individual and program factors associated with successful treatment completion. Recent literature has begun highlighting the salience of treatment engagement in reducing drug dependence among criminal offenders. This study descriptively analyzes incidents of treatment noncompliance identified in monthly progress reports for 150 criminal justice-mandated clients in residential treatment. We identify seven problem types and seven dimensions of noncompliance in the trajectory of treatment engagement. The latter are prevalence, frequency, types, specialization, temporal distribution, paths, and correlates. It is found that incidents of rule violations are common among criminal justice participants of residential treatment. Although for most clients these troubles do not appear to evolve into serious obstacles to recovery, a few clients with a high frequency of noncompliant behavior never engage in treatment. Clinical implications for improving treatment engagement and retention are discussed.

Adult↗

Trajectory formation and speed-accuracy trade-off in aiming movements.

The trade-off between speed and accuracy and the patterning of movement kinematics have been central issues for theories of human movement for almost a century. In the present contribution experimentally obtained kinematics of reciprocal aiming movements, performed under different task conditions, are modelled as resulting from a single non-linear dynamical system whose parameters vary so as to respond to the task demands. Providing a unified account of speed-accuracy trade-off and trajectory formation phenomena, the model offers a theoretical framework in which both discrete and continuous movements, performed along one or more dimensions can be understood.

Biophysical Phenomena↗