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PubMed2004

Prediction of alcohol-related harm from controlled drinking strategies and alcohol consumption trajectories.

AIMS: To establish predictors of age 21 alcohol-related harm from prior drinking patterns, current levels of alcohol consumption and use of controlled drinking strategies. PARTICIPANTS: One thousand, five hundred and ninety-six students recruited from an initial sample of 3300 during their final year of high school in 1993. DESIGN: Longitudinal follow-up across five waves of data collection. SETTING: Post high school in Victoria, Australia. MEASUREMENTS: Self-administered surveys examining a range of health behaviours, including alcohol consumption patterns and related behaviour. FINDINGS: Drinking behaviours at age 21 were found to be strongly predicted by drinking trajectories established through the transition from high school. Multivariate regression analysis revealed that alcohol-related harms at age 21 were reduced where current levels of alcohol use fell within limits recommended in Australian national guidelines. After controlling for this effect it was found that the range of strategies employed by participants to control alcohol use maintained a small protective influence. Post-high-school drinking trajectories continued to demonstrate a significant effect after controlling for current behaviours. FINDINGS: revealed that over one quarter of males and females drank alcohol, but on a less-than-weekly basis. This pattern of alcohol use demonstrated considerable stability through the post-school transition and was associated with a low level of subsequent harm at age 21. CONCLUSIONS: Future research should investigate whether encouraging more Australian adolescents to drink alcohol on a less-than-weekly basis may be a practical intervention target for reducing alcohol-related harms.

Adolescent↗
PubMed2006

Stress trajectories in mothers of young children with Down syndrome.

BACKGROUND: In this study, we investigated the early development of stress in mothers of children with Down syndrome, compared with mothers of children with developmental disabilities of mixed aetiologies. Growth modelling analyses were used to explore: (1) whether mothers of children with Down syndrome demonstrated distinct patterns of stress during their children's early development, compared with mothers of children with other developmental disabilities; and (2) whether there was a relation between child behavioural characteristics and the level and rate of change in stress observed in each population. METHOD: The stress trajectories of mothers of young children with Down syndrome (n = 25) and a mixed-aetiology comparison group (n = 49) were estimated, using growth modelling on data collected at ages of 15, 30 and 45 months. RESULTS: On average, stress in the mixed comparison group was higher at Time 1 and remained unchanged over time, while stress in the Down syndrome group was lower at Time 1 but increased steadily. After taking diagnostic group membership into account, more advanced cognitive-linguistic functioning and lower levels of maladaptive behaviours at all time points were associated with lower levels of maternal stress. CONCLUSIONS; These findings suggest that the cognitive-linguistic and behavioural trajectory observed in early development in Down syndrome may contribute to the changes in maternal stress levels observed throughout these early years. Implications for developing targeted and time- sensitive family interventions for families of children with Down syndrome are discussed.

Adult↗
PubMed1991

Bypassing the Saccadic Pulse Generator: Possible Control of Head Movement Trajectory by Rat Superior Colliculus.

Saccades produced by electrical stimulation of the superior colliculus in primates are influenced primarily by the location of the stimulating electrode, with the suprathreshold intensity or frequency of the stimulating pulse train having little effect. Any given collicular site produces a characteristic movement of relatively fixed amplitude and velocity. In accordance with this finding, in models of the saccadic eye movement system the superior colliculus specifies the change of eye position: the velocity of movement components are determined by 'pulse generators' located between the superior colliculus and the oculomotor neurons. Previous findings in rodents, however, have suggested that eye and head movements induced by stimulation at some collicular sites may be critically dependent on stimulation parameters, implying that in these animals the superior colliculus has access to a non-saccadic control system. To investigate this possibility, rats with electrodes implanted into the lateral intermediate layers were stimulated with pulse trains of varying frequency and duration, and the resultant head movements analysed from video tape. At seven of the nine sites studied, amplitude of the horizontal component of the head movement was linearly related to stimulating frequency for fixed-duration trains, in some cases over a ten-fold range. Subsequent variation of train duration showed that amplitude was affected not by frequency as such, but by the number of pulses in the train; frequency was related to the mean velocity of the movement. By appropriate setting of these parameters, independent control of head movement amplitude and velocity could be achieved. These results suggest that the rodent superior colliculus may be able to control head movement without recourse to a pulse generator, and thus influence the trajectory of the movement directly. If so, it may prove to be a useful preparation for testing theories of trajectory formation.

Journal Article↗
PubMedDate not supplied

Trajectory of weight changes in the first 6 weeks postpartum.

OBJECTIVE: To determine the trajectory of postpartum weight changes and to examine associations between weight change in the first 6 weeks postpartum and demographic, clinical, psychosocial, and behavioral variables. DESIGN: Prospective, longitudinal design. SETTING: Community hospital and university research setting. PARTICIPANTS: 26 low-income women (9 White, 8 Black, and 9 Hispanic) with uncomplicated term pregnancies. MAIN OUTCOME MEASURE: Body mass index measured weekly. RESULTS: Among White women, body mass index decreased significantly for the first 3 weeks of the postpartum period. Black women experienced a significant reduction in body mass index for only the first 2 postpartum weeks. Similarly, the postpartum body mass index decreased for the first 2 weeks for Hispanic women. Prepregnancy body mass index and gestational weight gain each had a significant positive effect on postpartum body mass index. Perception of social support at 4 weeks had a significant positive effect on postpartum body mass index in Black women. CONCLUSIONS: The trajectory of weight change was nonlinear with large initial weight losses during the first 2 to 3 weeks postpartum followed by weight plateaus for the remainder of the first 6 weeks postpartum.

Adult↗
PubMed2026

Divergent trajectories of genome architecture and chromosome evolution in ferns and angiosperms.

Ferns and angiosperms represent the two largest vascular plant lineages but exhibit striking genomic and ecological contrasts. We investigated whether differences in genome size, chromosome architecture, GC content, and stomatal traits reveal divergent evolutionary trajectories between these lineages. We assembled the most comprehensive dataset to date, integrating genome size, chromosome number and size, GC content, and stomatal traits for over 1100 fern species and compared it with an extensive angiosperm dataset. Ferns exhibited markedly lower variability and c. 16-fold slower rates of chromosome size evolution than angiosperms. A persistent positive relationship between genome size and chromosome number in ferns suggests limited cytological post-polyploid diploidization. While ferns generally possess larger stomata, this difference disappears after accounting for genome size, indicating that nucleotypic constraints, rather than lineage-specific physiology, dictate stomatal dimensions. Both groups share a unimodal GC-genome size relationship peaking at c. 14 Gbp. Larger fern chromosomes imply lower genome-wide recombination rates, potentially limiting genetic reshuffling and adaptive potential. Our results highlight fundamentally divergent evolutionary trajectories, likely shaped by meiotic symmetry in ferns and meiotic asymmetry, possibly centromere drive, and post-polyploid diploidization in angiosperms, defining the functional and genomic landscapes of these lineages across deep evolutionary timescales.

Genome, Plant↗
PubMed2006

Prenatal exposure to excess testosterone modifies the developmental trajectory of the insulin-like growth factor system in female sheep.

Experimental elevation of maternal testosterone (T) from 30 to 90 days of gestation leads to intrauterine growth retardation (IUGR) and increased prepubertal growth rate in female lambs. This study tested the hypothesis that prenatal T treatment during mid-gestation alters the trajectory of the fetal insulin-like growth factor (IGF)-insulin-like growth factor binding protein (IGFBP) system to promote IUGR and subsequent postnatal catch-up growth in female lambs. Plasma IGF-I and IGFBPs were measured by radioimmunoassay and Western ligand blot, respectively, on 65, 90 and 140 days (d) of gestation, at birth, approximately 5 months (prepubertal, the catch-up growth period), and approximately 9.5 months (postpubertal). Northern blot analysis was used to measure hepatic mRNA content of IGF system components during fetal stages. At fetal 65 d, plasma protein and hepatic mRNA content of IGFBP-1, an inhibitor of IGF bioactivity, was elevated in prenatal T-treated fetuses although body weight did not differ. There was a transient increase in plasma IGF-I and IGFBP-3 concentrations at fetal 90 d in prenatal T-treated fetuses. Hepatic IGF-I mRNA and plasma IGFBP-3 content were reduced by 140 d when body weight was reduced in prenatal T-treated fetuses. Plasma IGFBP-2 content was significantly reduced in prenatal T-treated newborns, but by 4 months these females had significantly higher circulating IGF-I and IGFBP-3 concentrations and faster growth rates than control females. After puberty, plasma IGF-I remained elevated in prenatal T-treated females. These findings provide evidence that prenatal T excess programmes the developmental trajectory of the IGF/IGFBP system in female sheep to reduce IGF bioavailability during IUGR and increase IGF bioavailability during prepubertal catch-up growth.

Animals↗
PubMedDate not supplied

The k-trajectory formulation of the NMR imaging process with applications in analysis and synthesis of imaging methods.

The fundamental operations of nuclear magnetic resonance (NMR) imaging can be formulated, for a large number of methods, as sampling the object distribution in the Fourier spatial-frequency domain, followed by processing the digitized data (often simply by Fourier transformation) to produce a digital image. In these methods, which include reconstruction from projections, Fourier imaging, spin-warp imaging, and echo-planar imaging, controllable gradient fields determine the points in the spatial-frequency domain which are sampled at any given time during the acquisition of data (the free induction decay, or FID). The detailed time dependence of the resulting trajectory of sample points (the k trajectory) determines the relative weight and accuracy with which image information at each spatial frequency is measured, establishing theoretical limitations on image quality achievable with a given imaging method. We demonstrate here that these considerations may be used to compare the theoretical capabilities of NMR imaging methods, and to derive new imaging methods with optimal theoretical imaging properties.

Image Enhancement↗
PubMed1999

Syllable intelligibility for temporally filtered LPC cepstral trajectories.

The intelligibility of syllables whose cepstral trajectories were temporally filtered was measured. The speech signals were transformed to their LPC cepstral coefficients, and these coefficients were passed through different filters. These filtered trajectories were recombined with the residuals and the speech signal reconstructed. The intelligibility of the reconstructed speech segments was then measured in two perceptual experiments for Japanese syllables. The effect of various low-pass, high-pass, and bandpass filtering is reported, and the results summarized using a theoretical approach based on the independence of the contributions in different modulation bands. The overall results suggest that speech intelligibility is not severely impaired as long as the filtered spectral components have a rate of change between 1 and 16 Hz.

Adult↗
PubMed2000

A comparative analysis of the center of gravity and center of pressure trajectory path lengths in standing posture: an estimation of active stiffness.

The center of foot pressure (CP) motions, representing the net neuromuscular control, was compared to the center of gravity (CG) motions, representing the net performance. The comparison focused on the trajectory path length parameter along the medio-lateral and antero-posterior axes because these two variables depend on amplitude versus frequency relationship. This relationship was used to evaluate the CG motions based on the CP motions. Seven subjects stood still on a force plate with eyes open and eyes closed. The results showed that the ratio of (CP-CG)/CP trajectory path length was personal for each subject. These results suggest different levels of passive (ligaments, elastic properties) and active (reflex activity) stiffness. For some subjects, this ratio was significantly lower for the eyes open condition than for the eyes closed condition, indicating a decrease of the active stiffness for the eyes open condition. Therefore, a CG-CP comparative analysis appeared helpful in understanding the control of balance and necessary to quantify the subjects' net performance.

Adult↗
PubMed2002

An evaluation of the minimum-jerk and minimum torque-change principles at the path, trajectory, and movement-cost levels.

In the present study we evaluated the minimum jerk and the minimum torque-change model at the path, trajectory, and movement-cost levels. To date, most evaluations of these models have mainly been restricted to path comparisons. Assessments of the time courses of realized jerk and torque changes are surprisingly lacking. Moreover, the extent to which the presumed optimized parameters change as a function of the duration and other temporal features of aiming movements has never been investigated, most probably because the models presuppose movement time. In order to fill this gap, we analyzed a subset of the data of an earlier experiment in which 12 participants performed leftward and rightward planar pointing movements. Hand displacements and joint excursions were recorded with a 3D motion-tracking system and subsequently evaluated by means of model-based analyses. The results show that despite a good agreement between observed paths and predicted paths, especially by the minimum torque-change model, the time courses of jerk and torque changes of observed and modeled movements differed considerably. These differences could mainly be attributed to asymmetrical properties of the time functions of slow movements. Variations of movement costs as a function of movement time and skewness of tangential velocity profiles show that, especially at high movement speed, costs increase exponentially with departures of symmetry. It is concluded that trajectory-formation models have limited explanatory power in situations that require demanding information processing during the homing-in phase of goal-directed movements. However, for slow movements, deviations from the optimal timing profiles require little extra costs in terms of jerk or torque change.

Adult↗
PubMed2004

Force-clamp spectroscopy monitors the folding trajectory of a single protein.

We used force-clamp atomic force microscopy to measure the end-to-end length of the small protein ubiquitin during its folding reaction at the single-molecule level. Ubiquitin was first unfolded and extended at a high force, then the stretching force was quenched and protein folding was observed. The folding trajectories were continuous and marked by several distinct stages. The time taken to fold was dependent on the contour length of the unfolded protein and the stretching force applied during folding. The folding collapse was marked by large fluctuations in the end-to-end length of the protein, but these fluctuations vanished upon the final folding contraction. These direct observations of the complete folding trajectory of a protein provide a benchmark to determine the physical basis of the folding reaction.

Chemical Phenomena↗
PubMed2006

Lifelong socioeconomic trajectory and premature mortality (35-65 years) in France: findings from the GAZEL Cohort Study.

BACKGROUND: Studies conducted in the UK and Scandinavia show an inverse association between lifetime socioeconomic position and adult mortality. However, there are virtually no data from other countries and few investigations have examined non-cardiovascular mortality in men and women. METHODS: Lifelong socioeconomic trajectories (father's occupation, own occupation in young adulthood and in mid-life) and premature (< or = 65 years) mortality (all-cause, smoking-related cancer, diseases of the circulatory system and external causes) in the French GAZEL Cohort Study (14,972 men and 5,598 women, followed up between 1990 and 2004) were studied. Hazard ratios (HRs) were estimated using Cox's regression models adjusted for age, marital status, tobacco smoking, alcohol consumption, body mass index, and fruit and vegetable consumption. RESULTS: Men and women who experienced lifelong disadvantage or downward intergenerational mobility were at high risk of dying prematurely compared with those with a favourable trajectory (age-adjusted HRs for all-cause mortality: cumulative disadvantage: HR 1.61, 95% confidence interval (CI) 1.26 to 2.06 in men and HR 1.95, 95% CI 1.10 to 3.47 in women; downward mobility: HR 1.87, 95% CI 1.35 to 2.58 in men and HR 2.05, 95% CI 1.12 to 3.75 in women). Associations were strongest for mortality due to chronic diseases (smoking-related cancers and diseases of the circulatory system). These associations were partly explained by marital status, body mass index, alcohol consumption, cigarette smoking, and fruit and vegetable consumption. CONCLUSIONS: In France, where the leading cause of premature death is cancer, lifelong socioeconomic position is associated with the risk of dying before the age of 65 years. Adult factors seem more relevant than childhood socioeconomic circumstances.

Adult↗
PubMed2002

Mapping epigenetic quantitative trait loci (QTL) altering a developmental trajectory.

Genetic variation in a quantitative trait that changes with age is important to both evolutionary biologists and breeders. A traditional analysis of the dynamics of genetic variation is based on the genetic variance-covariance matrix among different ages estimated from a quantitative genetic model. Such an analysis, however, cannot reveal the mechanistic basis of the genetic variation for a growth trait during ontogeny. Age-specific genetic variance at time t conditional on the causal genetic effect at time t - 1 implies the generation of episodes of new genetic variation arising during the interval t - 1 to t. In the present paper, the conditional genetic variance estimated from Zhu's (1995) conditional model was partitioned into its underlying individual quantitative trait loci (QTL) using molecular markers in an F2 progeny of poplars (Populus trichocarpa and Populus deltoides). These QTL, defined as epigenetic QTL, govern the alterations of growth trajectory in a population. Three epigenetic QTL were detected to contribute significantly to variation in growth trajectory during the period from the establishment year to the subsequent year in the field. It is suggested that the activation and expression of epigenetic QTL are influenced by the developmental status of trees and the environment in which they are grown.

Analysis of Variance↗
PubMed1995

Proprioceptive sensory codes mediating movement trajectory perception: human hand vibration-induced drawing illusions.

To study the organization of the proprioceptive sensory codes subserving movement trajectory perception, complex hand drawing illusions were elicited using various vibration patterns applied to the wrist muscles of nine human subjects. It was established that it is possible to elicit kinesthetic illusions involving spatially oriented lines and geometrical shapes such as rectilinear or curvilinear figures by activating four groups of muscle tendons at the wrist level. The vibration sequences specifically evoking each shape were determined by varying the vibration frequency, the duration of each stimulus applied, and the vibrator onsets, and by applying the vibrations either successively or simultaneously. The proprioceptive coding of a trajectory can be modelled in terms of a series of vectors, the direction of which depends on the anatomical sites of the muscles that are stretched and shortened during the movement. The vector giving the spatial path of a movement is the sum vector of the vectors determined on the basis of the proprioceptive inputs originating from each muscle, and the modulus of the resulting vector is the instantaneous velocity of the movement. In line with previous cortical data, our results suggest that the perception of the spatial paths of limb segment movements is coded in joint space kinematic coordinates on the basis of the relevant ongoing proprioceptive information. It therefore emerges from the results of this study that muscle proprioception is able to generate spatiotemporal afferent patterns that may mediate complex cognitive operations such as those involved in the memorizing and recognition of motor forms.

Female↗
PubMed2005

Exploring protein folding trajectories using geometric spanners.

We describe the 3-D structure of a protein using geometric spanners--geometric graphs with a sparse set of edges where paths approximate the n2 inter-atom distances. The edges in the spanner pick out important proximities in the structure, labeling a small number of atom pairs or backbone region pairs as being of primary interest. Such compact multiresolution views of proximities in the protein can be quite valuable, allowing, for example, easy visualization of the conformation over the entire folding trajectory of a protein and segmentation of the trajectory. These visualizations allow one to easily detect formation of secondary and tertiary structures as the protein folds.

Computational Biology↗
PubMed1996

Regional lung volume trajectories during expiratory flow in dogs.

Parenchymal markers were placed in the left caudal lobes of anesthetized dogs, and the three-dimensional positions of the markers were tracked by biplane videofluoroscopy during expiration from total lung capacity (TLC) to approximately 30% TLC at steady expiratory flows of 0.3-7% TLC/s. Regional volumes of samples of parenchyma with volumes at TLC of 1-5 cm3 were obtained by computing the volumes of tetrahedral defined by taking the markers, four at a time, as apices of the tetrahedra, Regional volume (Vr), as a fraction of volume at TLC, was plotted against average volume (VL), as a fraction of volume at TLC, and Vr was fit by a quadratic function of VL. The initial slopes of the plots, dVr/dVL at VL = 1, varied by +/- 26% from the mean slope of 1. The curvatures were highly correlated with the slopes, and the Vr vs. VL plots formed a nest of "onion skins". The initial slopes were weakly correlated with the vertical position of the centroid of the tetrahedron, with the slope increasing by approximately 20%/cm, on average, in the dorsal direction in the supine dog. The vertical gradient in Vr accounted for approximately 30% of the total variability; small-scale heterogeneity contributed the remaining 70%. These results confirm earlier quasistatic measurements of nonuniform Vr and provide the first data on curvature of Vr trajectories. The mechanisms that cause the nongravitational component of Vr variability and the curvatures of the trajectories are unknown.

Animals↗
PubMed1995

Motor adaptation to Coriolis force perturbations of reaching movements: endpoint but not trajectory adaptation transfers to the nonexposed arm.

1. Reaching movements made in a rotating room generate Coriolis forces that are directly proportional to the cross product of the room's angular velocity and the arm's linear velocity. Such Coriolis forces are inertial forces not involving mechanical contact with the arm. 2. We measured the trajectories of arm movements made in darkness to a visual target that was extinguished at the onset of each reach. Prerotation subjects pointed with both the right and left arms in alternating sets of eight movements. During rotation at 10 rpm, the subjects reached only with the right arm. Postrotation, the subjects pointed with the left and right arms, starting with the left, in alternating sets of eight movements. 3. The initial perrotary reaching movements of the right arm were highly deviated both in movement path and endpoint relative to the prerotation reaches of the right arm. With additional movements, subjects rapidly regained straight movement paths and accurate endpoints despite the absence of visual or tactile feedback about reaching accuracy. The initial postrotation reaches of the left arm followed straight paths to the wrong endpoint. The initial postrotation reaches of the right arm had paths with mirror image curvature to the initial perrotation reaches of the right arm but went to the correct endpoint. 4. These observations are inconsistent with current equilibrium point models of movement control. Such theories predict accurate reaches under our experimental conditions. Our observations further show independent implementation of movement and posture, as evidenced by transfer of endpoint adaptation to the nonexposed arm without transfer of path adaptation. Endpoint control may occur at a relatively central stage that represents general constraints such as gravitoinertial force background or egocentric direction relative to both arms, and control of path may occur at a more peripheral stage that represents moments of inertia and muscle dynamics unique to each limb. 5. Endpoint and path adaptation occur despite the absence both of mechanical contact cues about the perturbing force and visual or tactile cues about movement accuracy. These findings point to the importance of muscle spindle signals, monitoring of motor commands, and possibly joint and tendon receptors in a detailed trajectory monitoring process. Muscle spindle primary and secondary afferent signals may differentially influence adaptation of movement shape and endpoint, respectively.

Adaptation, Physiological↗
PubMed1998

Modeling control of eye orientation in three dimensions. I. Role of muscle pulleys in determining saccadic trajectory.

This study evaluates the effects of muscle axis shifts on the performance of a vector velocity-position integrator in the CNS. Earlier models of the oculomotor plant assumed that the muscle axes remained fixed relative to the head as the eye rotated into secondary and tertiary eye positions. Under this assumption, the vector integrator model generates torsional transients as the eye moves from secondary to tertiary positions of fixation. The torsional transient represents an eye movement response to a spatial mismatch between the torque axes that remain fixed in the head and the displacement plane that changes by half the angle of the change in eye orientation. When muscle axis shifts were incorporated into the model, the torque axes were closer to the displacement plane at each eye orientation throughout the trajectory, and torsional transients were reduced dramatically. Their size and dynamics were close to reported data. It was also shown that when the muscle torque axes were rotated by 50% of the eye rotation, there was no torsional transient and Listing's law was perfectly obeyed. When muscle torque axes rotated >50%, torsional transients reversed direction compared with what occurred for muscle axis shifts of <50%. The model indicates that Listing's law is implemented by the oculomotor plant subject to a two-dimensional command signal that is confined to the pitch-yaw plane, having zero torsion. Saccades that bring the eye to orientations outside Listing's plane could easily be corrected by a roll pulse that resets the roll state of the velocity-position integrator to zero. This would be a simple implementation of the corrective controller suggested by Van Opstal and colleagues. The model further indicates that muscle axis shifts together with the torque orientation relationship for tissue surrounding the eye and Newton's laws of motion form a sufficient plant model to explain saccadic trajectories and periods of fixation when driven by a vector command confined to the pitch-yaw plane. This implies that the velocity-position integrator is probably realized as a subtractive feedback vector integrator and not as a quaternion-based integrator that implements kinematic transformations to orient the eye.

Eye Movements↗