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PubMed2005

Growth trajectories are influenced by breast-feeding and infant health in an afro-colombian community.

We conducted a longitudinal study among an Afro-Colombian population to investigate the influence of feeding practices and child morbidity on linear and ponderal growth during infancy. We enrolled 133 children at 5-7 mo and followed them until 18 mo. Repeated anthropometric measures were taken every 2-3 mo, with monthly interviews on feeding practices and daily self-reports on morbid conditions by the mothers of the infants. Mothers' social conditions and infants' fixed variables (gender and gestational age at birth) were measured at baseline. Growth starting points and trajectories were modeled via Hierarchical Linear Models (HLM). Children started with a mean length of 64.8 cm (95% CI: 59.8-69.7) and a mean weight of 7.68 kg (95% CI: 5.37-9.9), and gained length at a rate of 1.13-1.70 cm/mo, and weight at 66.5-319 g/mo. Breast-feeding, defined as receiving breast milk at any time within a 2-3-mo interval, was positively related to length gain (regression coefficient = 0.27 cm/mo; P = 0.04), after adjusting for social conditions and food consumption. Among mothers with low levels of education, breast-feeding had a positive effect on weight gain (regression coefficient = 0.30 kg/mo; P = 0.04); among nonbreast-fed infants, complementary food diversity generated a positive effect on weight (regression coefficient = 0.14 kg/mo; P = 0.03). Mean differences in length were related to the total proportion of healthy time (regression coefficient = 3.1; P = 0.02), whereas weight-gain rates were negatively associated with changes during illness (regression coefficient = -0.70; P = 0.04 for fever). No association was found between diarrhea episodes and infant growth. Our study confirms that breast-feeding after 6 mo of life is important for nutrition and health, likely by mitigating the negative effects of poor social conditions and diarrhea on infant growth.

Black People↗

PubMed2003

In vivo multiphoton imaging of a transgenic mouse model of Alzheimer disease reveals marked thioflavine-S-associated alterations in neurite trajectories.

Postmortem analyses of senile plaques reveal numerous dystrophic processes in their vicinity. We used in vivo multiphoton microscopy of a transgenic model of Alzheimer disease (AD) to simultaneously image senile plaques and nearby neuronal processes. Plaques were labeled by immunofluorescent staining or thioflavine-S and neuronal processes were labeled with a fluorescent dextran conjugate. Imaging of 3-dimensional volumes in the vicinity of plaques revealed subtle changes in neurite geometry in or near diffuse plaques. By contrast, disruptions in neurite morphology, including dystrophic neurites immediately surrounding plaques as well as major alterations in neurite trajectories, were seen in association with thioflavine-S-positive plaques. Nearly half of all labeled processes that came within 50 microm of a thioflavine-S-positive plaque were altered, suggesting a fairly large "halo" of neuropil alterations that extend beyond the discrete border of a thioflavine-S plaque. These results support the hypothesis that compact thioflavine-S-positive plaques disrupt the neuropil in AD.

Aging↗

PubMed2006

Predictors of parenting behavior trajectories among families of young adolescents with and without spina bifida.

OBJECTIVE: To evaluate the utility of familial and parental variables in predicting trajectories of parenting behaviors among families of young adolescents with and without spina bifida (SB). METHOD: Sixty-eight families with a child with SB and a demographically matched comparison group (CG) of 68 families of an able-bodied child participated. Observational and questionnaire assessments of parenting behavior were collected via home visits at three time points, as were reports of parent and family functioning. RESULTS: Family conflict was negatively associated with adaptive parenting behavior at Time 1 (T1), but positively associated with adaptive parenting change. Although the direction of this effect was the same across both groups, findings were more robust for the SB sample. Among fathers of children with SB, parenting stress was positively associated with adaptive parenting at T1 but negatively associated with adaptive parenting change. In contrast, within the CG, paternal parenting stress was negatively associated with adaptive parenting at T1 but showed no enduring negative effects in longitudinal analyses. CONCLUSIONS: Family conflict and parenting stress were significant predictors of parenting behaviors and longitudinal parenting change. Findings are interpreted within a developmental context such that variables associated with maladaptive (or adaptive) parenting in the short run, may facilitate adaptive (or maladaptive) parenting over time based on young adolescents' changing developmental needs.

Adaptation, Psychological↗

PubMed1994

Torsion angle differences as a means of pinpointing local polypeptide chain trajectory changes for identical proteins in different conformational states.

We discuss a facile and sensitive method of determining conformational differences based on the changes in the phi and psi angle values between chemically identical proteins in different conformations. It complements the conventional r.m.s. deviation technique, but offers some advantages. Two classes of conformational difference can be distinguished by this method: (i) abrupt local trajectory deformations where the chains flanking the locus of deformation remain simultaneously superposable and (ii) localized 'hinge bending' that generates domain shifts, thereby causing only one domain to be superposable on the other at one time. In the second case, the r.m.s. deviation method requires two or more calculations of r.m.s. deviation as a function of sequence after optimal alignment of each domain to demonstrate the superposability of the shifted domains, and hence the conservation of internal domain structure. On the other hand, the method of plotting delta phi and/or delta psi as a function of sequence demonstrates in one graph the superposability of shifted domains, without the prior need to perform rotational and translational alignments whose outcomes vary with the subjective choice of alignment parameters. Also, an analysis of the r.m.s. deviation in C alpha alone will miss torsion angle rotations that happen to preserve C alpha positions. The method pinpoints residues contributing singly to localized, major movements of a conformational change; however, it is insensitive to conformational changes achieved through small, concerted movements spread over a number of residues.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, Bacterial↗

PubMed1995

Spatial attention-determined modifications in saccade trajectories.

Normal subjects were required to make horizontal or vertical saccades at the presentation of visual or acoustic imperative stimuli. The locations of visual imperative stimuli were orthogonal to the required saccade. Before stimulus presentation the subjects were cued about its location and instructed to allocate attention to it without moving the eyes. The main aim of the experiment was to establish whether the trajectory of horizontal saccades would be modified by spatial attention. The results showed that, with respect to the condition in which attention was on the horizontal meridian, the allocation of attention to the upper hemifield determined a downward saccade deviation, while the allocation to the lower hemifield determined an opposite deviation. The data strongly support the view that spatial attention and saccade programming share the same neural substrates.

Acoustic Stimulation↗

PubMed2005

Assessing vestibular contributions during changes in gait trajectory.

Displacing prisms and galvanic stimulation were used to examine visual-vestibular interactions during target-directed gait. Participants walked towards a wall 6 m away. After taking four steps, a target on the wall, located directly in front or to the right of the participant, was illuminated. Participants continued walking towards the target. Galvanic vestibular stimulation was triggered at either gait initiation, a step before the potential turn, or at target illumination. Although the visual and vestibular perturbations significantly altered gait trajectory, the greatest interaction occurred when galvanic stimulation was triggered one step before the target appeared. This implies an increase in the weighting of vestibular inputs just before turning to prepare for the potential change in direction.

Adult↗

PubMed1994

Three-channel Lissajous' trajectory of human middle latency auditory evoked potentials.

OBJECTIVE: We provide the normative values for middle latency auditory evoked potentials (MLAEPs) measures (three-channel Lissajous' trajectories or 3-CLT) in response to clicks and tone pips, which are the stimuli most widely used in MLAEP clinical testing. The relationship of 3-CLT measures to the more widely used latency and amplitude characteristics of the single-channel MLAEP of the same subjects was also evaluated. We further relate the 3-CLT findings to the question of MLAEP generators. DESIGN: 3-CLT of MLAEPs were derived from 12 humans (24 ears) in response to 65 dB nHL, rarefaction clicks as well as tone pips (1000 Hz), presented at a rate of 3.3/sec. A normative set of 3-CLT measures was calculated and compared with the corresponding measures of simultaneously recorded, single-channel vertex-left mastoid and vertex-neck derivation of MLAEP. RESULTS: Apex latencies of 3-CLT were comparable to peak latencies of the vertex-neck record, both in absolute values and in intersubject variability. Durations of planar segments were approximately 5.0 msec. Size and shape measures of planar segments were variable across subjects, making their clinical use, in their present form, questionable. CONCLUSIONS: The results showed two apices and associated planar segments (i1 and i2) in the 3-CLT of MLAEP which corresponded to the vertex-neck component Pa. These results and earlier studies that indicated a dual set of generators for Pa are compatible with a primary auditory cortex generator for i1 and ascending subcortical generators for i2.

Adolescent↗

PubMed2005

Handedness: differential specializations for control of trajectory and position.

Handedness is often portrayed as a nonfunctional artifact of cerebral asymmetry. Our data, however, indicate that handedness reflects cerebral specialization for specific control processes. Each hemisphere/limb system is specialized for different but complementary functions: the dominant system for controlling limb trajectory dynamics, and the nondominant system for controlling limb position.

Biomechanical Phenomena↗

PubMed1990

Developmental implications of changing trajectories of IQ in males with fragile X syndrome.

This study examined the trajectories of cognitive development in boys under the age of 21 years with fragile X syndrome. By combining information from three centers, data from 66 boys were analyzed; only children who had been tested two or more times with the same psychometric instrument at one or more year intervals were included in this study. Results demonstrated that males with fragile X syndrome show a decline in IQ scores, with the most marked declines seen during the early pubertal period. All 22 children retested during the 11- to 15-year period showed IQ declines, suggesting a slowing of development associated with the onset of puberty. Before age 10 years, males with higher (as opposed to lower) pretest IQs were more likely to decline at subsequent testings. A single etiological factor may not be sufficient to account for the observed findings, as both changes in neurobiological- and task-related factors seem implicated in the slowing intellectual development of this population.

Adolescent↗

PubMed1992

Profiles, correlates, and trajectories of intelligence in Prader-Willi syndrome.

Three aspects of intellectual functioning in persons with Prader-Willi syndrome were examined in two, related studies. In study 1, 21 subjects were evaluated with a psychometric instrument that assesses neuropsychological styles of cognitive processing, the Kaufman Assessment Battery for Children. Prader-Willi subjects showed deficits in sequential processing, and strengths in academic achievement tasks such as reading and vocabulary. In contrast to previous reports on the syndrome, no relationship was found between weight and degree of intellectual impairment. Study 2 included a cross-sectional examination of the trajectory of IQ in 21 subjects aged 13 to 46 years, as well as a longitudinal analysis of 31 subjects aged 5 to 30 years who were tested twice with the same IQ test. No evidence of the previously described decline in IQ over time was noted in either the cross-sectional or longitudinal analyses. The implications of these findings for interventions are discussed.

Achievement↗

PubMed1992

The utility of severity of illness information in assessing the quality of hospital care. The role of the clinical trajectory.

This research explored whether differentiating patients whose severity of illness worsened, improved, or remained the same over the hospital stay is a good screen for quality of care. The hypothesis was that substandard care is more likely to occur among patients who have worsened. Severity was measured using the Computerized Severity Index (CSI) and MedisGroups in 233 patients who had experienced acute myocardial infarction and 279 who had undergone coronary artery bypass graft who were admitted to four New England hospitals in 1987. Deaths and patients with discharge diagnoses indicating iatrogenic events and complications were oversampled. Potential quality problems were identified through explicit screening criteria applied by nurse researchers and implicit physician reviews. Acute myocardial infarction patients who worsened had higher rates of potential quality problems than other patients (CSI, P = 0.06; MedisGroups, P = 0.01). For the CSI, the 49.4% of patients who worsened captured 70.6% of the potentially substandard care; for MedisGroups, the 35.6% of patients who worsened also encompassed 70.6% of the problematic cases. For coronary artery bypass graft, results varied depending on how severity and quality were defined. The CSI performed better using implicit physician review to identify problematic care (P = 0.00), capturing 76.5% of substandard cases among the 41.6% of patients who worsened. In contrast, MedisGroups did better using explicit quality screens (P = 0.04), grouping 60.5% of the problematic cases among the 47.0% of patients who worsened. After removing in-hospital deaths from consideration, a worsening trajectory was generally associated with a higher fraction of potential quality problems among live discharges. This preliminary study suggests that examining changes in illness severity may be a useful screen for substandard hospital care, but its utility could vary by condition and by how quality problems are defined.

Coronary Artery Bypass↗

PubMed1993

Trajectory and empowerment theory applied to care of patients with multiple sclerosis.

Two theoretical frameworks were examined for their applicability to nursing care of multiple sclerosis (MS) patients. The Corbin and Strauss Trajectory Framework assumes that the course of chronic illness (eg, MS) varies over time and can be reconfigured by treatment and management. Miller's theory of chronically ill patient's empowerment to promote successful coping is derived by combining previously developed concepts of coping and empowerment to maintain control and enhance the quality of life. These theoretical frameworks offer great potential for guiding the nursing care of MS patients who require extensive repertoires of coping skills to deal with the stress of this chronic illness. However, further research is required to establish their validity.

Activities of Daily Living↗

PubMed2004

Major histocompatibility complex controls the trajectory but not host-specific adaptation during virulence evolution of the pathogenic fungus Cryptococcus neoformans.

Genes of the major histocompatibility complex (MHC) play a critical role in immune recognition and are the most genetically diverse loci known. One hypothesis to explain this diversity postulates that pathogens adapt to common MHC haplotypes and thus favour selection of new or rare alleles. To determine whether the pathogenic yeast Cryptococcus neoformans adapts to MHC-dependent immune responses, it was serially passaged in two independent replicate lines of five B10 MHC-congenic strains and Balb/c mice. All passaged lines increased in virulence as measured by reduced host survival. MHC influenced the rate (trajectory) of virulence increase during passages as measured by significant differences in mortality rate (p < 0.001). However, when the post-passage strains were tested, no MHC differences in mortality rate remained and only minor differences in titres were observed. Also contrary to expectations, increased virulence in three lines passaged in B10 mice had a larger effect in Balb/c mice, and the evolution of virulence in lines passaged in alternating hosts was not retarded. To our knowledge, these data represent the first experimental test of MHC-specific adaptation in a non-viral pathogen. The failure to observe MHC effects despite dramatically increased virulence and host-genotype-specific adaptation to non-MHC genes suggests that escape of MHC-dependent immune recognition may be difficult for pathogens with unlimited epitopes or that other virulence factors can swamp MHC effects.

Adaptation, Biological↗

PubMed2000

Kinetics of stochastically gated diffusion-limited reactions and geometry of random walk trajectories

In this paper we study the kinetics of diffusion-limited, pseudo-first-order A+B-->B reactions in situations in which the particles' intrinsic reactivities are not constant but vary randomly in time. That is, we suppose that the particles are bearing "gates" which fluctuate in time, randomly and independently of each other, between two states-an active state, when the reaction may take place between A and B particles appearing in close contact; and a blocked state, when the reaction is completely inhibited. We focus here on two customary limiting cases of pseudo-first-order reactions-the so-called target annihilation and the Rosenstock trapping model-and consider four different particular models, such that the A particle can be either mobile or immobile or gated or ungated, and ungated or gated B particles can be fixed at random positions or move randomly. All models are formulated on a d-dimensional regular lattice, and we suppose that the mobile species perform independent, homogeneous, discrete-time lattice random walks. The model involving a single, immobile, ungated target A and a concentration of mobile, gated B particles is solved exactly. For the remaining three models we determine exactly, in the form of rigorous lower and upper bounds showing the same N dependence, the large-N asymptotical behavior of the probability that the A particle survives until the Nth step. We also realize that for all four models studied here the A particle survival probability can be interpreted as the moment generating function of some functionals of random walk trajectories, such as, e. g., the number of self-intersections, the number of sites visited exactly a given number of times, the "residence time" on a random array of lattice sites, etc. Our results thus apply to the asymptotic behavior of corresponding generating functions which are not known as yet.

Journal Article↗

PubMed2000

Descriptive parameter for photon trajectories in a turbid medium.

In many applications of laser techniques for diagnostic or therapeutic purposes it is necessary to be able to characterize photon trajectories to know which parts of the tissue are being interrogated. In this paper, we consider the cw reflectance experiment on a semi-infinite medium with uniform optical parameters and having a planar interface. The analysis is carried out in terms of a continuous-time random walk and the relation between the occupancy of a plane parallel to the surface to the maximum depth reached by the random walker is studied. The first moment of the ratio of average depth to the average maximum depth yields information about the volume of tissue interrogated as well as giving some indication of the region of tissue that gets the most light. We have also calculated the standard deviation of this random variable. It is not large enough to qualitatively affect information contained in the first moment.

Lasers↗

PubMed2000

Bursts in the chaotic trajectory lifetimes preceding controlled periodic motion

The average lifetime [tau(H)] it takes for a randomly started trajectory to land in a small region (H) on a chaotic attractor is studied. tau(H) is an important issue for controlling chaos. We point out that if the region H is visited by a short periodic orbit, the lifetime tau(H) strongly deviates from the inverse of the naturally invariant measure contained within that region [&mgr;(N)(H)(-1)]. We introduce the formula that relates tau(H)/&mgr;(N)(H)(-1) to the expanding eigenvalue of the short periodic orbit visiting H.

Journal Article↗

PubMed2000

Arbitrary trajectory quantization method.

The arbitrary trajectory quantization method (ATQM) is a time dependent approach to quasiclassical quantization based on the approximate dual relationship that exists between the quantum energy spectra and classical periodic orbits. It has recently been shown however, that, for polygonal billiards, the periodicity criterion must be relaxed to include closed almost-periodic (CAP) orbit families in this relationship. In light of this result, we reinvestigate the ATQM and show that at finite energies, a smoothened quasiclassical kernel corresponds to the modified formula that includes CAP families while the delta function kernel corresponding to the periodic orbit formula is recovered as E-->infinity. Several clarifications are also provided.

Journal Article↗

PubMed2001

Three-dimensional optical trajectory tracing and energy deposition of a laser beam in a laser-driven fusion.

A convenient method of three-dimensional ray tracing is suggested in the geometrical optical approximation, in which the laser ray propagation is completely based on the concept of optical trajectory tracing rather than depending upon the effective force and propagation time. This tracing has two obvious advantages that the direct application of Snell's law can be avoided when a ray crosses a different density zone and that to any desired accuracy it takes much less computation time than existing tracing. For Gaussian light beam propagation, in a spherically symmetric plasma atmosphere, the results emphasize that the deposition uniformity is strongly dependent not only on the wavelength of the laser but also on the temperature of the plasma.

Journal Article↗