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Comparison of multiple molecular dynamics trajectories calculated for the drug-resistant HIV-1 integrase T66I/M154I catalytic domain.

HIV-1 integrase (IN) is an essential enzyme for the viral replication and an interesting target for the design of new pharmaceuticals for multidrug therapy of AIDS. Single and multiple mutations of IN at residues T66, S153, or M154 confer degrees of resistance to several inhibitors that prevent the enzyme from performing its normal strand transfer activity. Four different conformations of IN were chosen from a prior molecular dynamics (MD) simulation on the modeled IN T66I/M154I catalytic core domain as starting points for additional MD studies. The aim of this article is to understand the dynamic features that may play roles in the catalytic activity of the double mutant enzyme in the absence of any inhibitor. Moreover, we want to verify the influence of using different starting points on the MD trajectories and associated dynamical properties. By comparison of the trajectories obtained from these MD simulations we have demonstrated that the starting point does not affect the conformational space explored by this protein and that the time of the simulation is long enough to achieve convergence for this system.

Biophysics↗

Prevalence, correlates, and trajectory of television viewing among infants and toddlers.

OBJECTIVES: Recognizing the negative effects of television on children, the American Academy of Pediatrics (AAP) recommends that children 2 years and older watch <2 hours of television per day and that children younger than 2 years watch no television. However, relatively little is known about the amount of television viewed by infants and toddlers. The objective of this study was to describe the prevalence and correlates of television viewing that exceeds the AAP guidelines for 0- to 35-month-olds and to examine the trajectory of a child's viewing over time. METHODS: Data from the National Longitudinal Survey of Youth, 1990 to 1998, were used to analyze reported television viewing at 0 to 35 months of age and to follow the trajectory of a child's viewing from infancy through age 6. Logistic regression models were used to determine risk factors associated with greater television viewing at 0 to 35 months and the association of early viewing habits with school-age viewing. RESULTS: Seventeen percent of 0- to 11-month-olds, 48% of 12- to 23-month-olds, and 41% of 24- to 35-month-olds were reported to watch more television than the AAP recommends. Compared with college graduates, less-educated women were more likely to report that their children watched more television than recommended. Children who watched >2 hours per day at age 2 were more likely to watch >2 hours per day at age 6 (odds ratio: 2.7; 95% confidence interval: 1.8-3.9), controlling for maternal education, race, marital status and employment, household income, and birth order. CONCLUSIONS: A substantial number of children begin watching television at an earlier age and in greater amounts than the AAP recommends. Furthermore, these early viewing patterns persist into childhood. Preventive intervention research on television viewing should consider targeting infants and toddlers and their families.

Black or African American↗

[Telling a beautiful story: the trajectory of the Brazilian Nurses Association-Bahia].

This study presents the story of the Brazilian Association of Nursing in Bahia federal state. It parallels the trajectory of this association to the history of the National Brazilian Association of Nursing, pointing out the most important events in its fifty-three years of work. It is clear that the history of the Brazilian Association of Trained Nurses (ABED)/ABEn-Bahia begins with the foundation of the Nursing School of the Federal University of Bahia. Teachers at this university, who were nurses in their home states, and had participated in other associations previously, were motivated to create a new branch of ABEn in Bahia. The branch of ABEn in the city of Feira de Santana-Bahia, had a similar trajectory, since it was also founded after the creation of the State University of Feira de Santana. The branch of ABEn in Bahia is considered a democratic association, which is attentive to the claims of the nursing professionals, the health of the Brazilian population and also to the strengthening of the organization.

Brazil↗

School trajectory and teenage pregnancy in three Brazilian state capitals.

This paper describes the relationship between school trajectory and incidence of teenage pregnancy. A cross-sectional residence-based questionnaire was applied, interviewing 4,634 youth ages 18 to 24 years, selected through a stratified three-stage sample. For the present study, young people ages 20 to 24 years (65.6%) were chosen, with teenage pregnancy rates of 29.5% for females and 21.4% for males (in relation to their partners). Sexual debut was reported by 87% of women and 95.3% of men. The majority of young people reported irregular school trajectory, with 39% enrolled in school at the time of the study. Nearly half of those who had interrupted their studies at least once reported a teenage pregnancy. The main reasons for interrupting their studies were pregnancy and children for women and work for men. School dropout due to teenage pregnancy was mentioned by 40.1% of women for whom the outcome of pregnancy was a child. However, 20.5% had already dropped out of school before becoming pregnant.

Adolescent↗

Trajectories of aging: imagined pathways in later life.

The model of aging that people construct influences interpretations of and responses to actual situations when they occur, as well as preparatory actions that people take. Thus the question of what people foresee for themselves and the process by which they construct and revise this subjective aging trajectory has implications for such issues as health behavior, retirement planning, migration and residential moves, and advance directives, as well as for overall well-being in old age. This exploratory, hypothesis-generating study found that informants referred frequently to the course of aging and the events they envisioned in their own futures. The analysis delineates 1) types of events that older people see as part of aging in general and their own aging in particular, 2) factors and processes that enter into the construction of the subjective trajectory of aging, and 3) feeling and behavioral responses to the imagined future.

Affect↗

Trajectory formation of vertical arm movements through a via-point: a limit of validity of the minimum-jerk model.

The minimum-jerk model predicts the smoothest trajectory for a class of human movements and so provides us with a kinematic measurement of skilled motor performance. To establish the limits of the model's validity, the predicted and experimentally defined movement trajectories and the joint coordination were compared in two-joint arm movements, bringing the hand from the initial position to the final position through a specified point (a via-point). Kinematic data of the movements were obtained through the SELSPOT system. The movement path, tangential velocity, and coordinated change in positions of the shoulder and elbow joints evidently deviated from those predicted by the model. These results suggest that the minimum-jerk model is not valid for movements under extreme conditions which are highly dependent on musculoskeletal dynamics.

Adult↗

Is spatial judgement of ball trajectories a highly differentiated or hierarchically organized skill?

An experiment was designed to examine the structure of spatial judgement skill related to ball trajectories. 54 subjects (16 to 23 years old) were administered prediction tasks in two highly contrasted planes (saggital vs fronto-parallel) and a speed of visual-discrimination task. Factor analysis shows that the skill is hierarchically organized with a broad-spectrum factor which covers the whole range of perceptual conditions and two group factors, one per trajectory plane. The low magnitude of the partial correlations between Inspection Time and Prediction Tasks (with simple reaction time kept constant) was interpreted as a confirmation of the hierarchical nature of the skill.

Adolescent↗

Three-channel Lissajous trajectories of auditory brainstem-evoked potentials in patients with neurological lesions affecting the brainstem: preliminary impressions.

Three-channel Lissajous trajectories (3CLT), as well as vertex-mastoid records of auditory brainstem-evoked potentials (ABEP) were obtained from 12 patients with neurological lesions localized to the auditory nerve, the medulla, the pons, the pons and midbrain and the midbrain. Patients selected had well-localized lesions at the levels of the presumed generators of ABEP (10 patients), as well as below (1 patient) and above (1 patient) those levels. The 3CLT measures used were trajectory amplitude, peak latency and amplitude, planar segment number, apex latency, duration, orientation in voltage space, as well as size and shape. Latencies and amplitudes of vertex-positive peaks I-V, as well as interpeak latency differences, were determined. Vertex-mastoid ABEP and 3CLT were compared in terms of their sensitivity to the existence of a lesion, the accuracy of lesion localization as well as their specificity to the lesion. 3CLT had an advantage in all three comparisons, with the most prominent advantage in specificity, which was over twice as high as that of single-channel ABEP. The results of this preliminary study indicate that 3CLT affords a sensitive analysis of ABEP, which is superior to single-channel analysis in sensitivity, accuracy and specificity. These results also indicate that the 'contralateral effect' of peak V latency prolongation in cerebellopontine angle tumors may be related to anatomical changes of its generators' orientation, rather than slowed conduction along the upper brainstem.

Brain Diseases↗

Effects of electrolytic lesions of the superior olivary complex and trapezoid body on brainstem auditory-evoked potentials in the guinea pig. II. Three-channel Lissajous' trajectory analysis.

Brainstem auditory-evoked potentials (BAEP) were studied both with vertex (positive) - tragus (negative) derivation and three-channel Lissajous' trajectory (3-CLT) planar analysis in guinea pigs (GP) after destruction of the ipsilateral superior olivary complex (SOC) (6 GP), contralateral SOC (8 GP) referred to the stimulation side, and trapezoid body (TB) in the sagittal line (8 GP). The size of the lesion was evaluated on histological examination. The right ear was locally destroyed with aminoside instillation. The left ear was stimulated with unfiltered clicks and tone bursts of different frequencies at 100 dB SPL. Three questions were the basis of this study: (i) What are the effects of brainstem lesions on 3-CLT? (ii) Is there a relationship between planar segments and underlying sources? (iii) What is the generator of planar segment C (P3) in GP? 3-CLT analysis was made on plane A (corresponding to P1 on a vertex-tragus channel), plane B (N1-P2) and plane C (P3.) Plane C disappeared after TB lesions and remained after ipsi- and contralateral SOC destructions. However, plane C disappeared after extensive lesions to the contralateral SOC affecting the TB. Planes A and B were always observed whatever the lesion, with sometimes a modification of their orientation. A localized brainstem lesion induced a local modification of the three-dimensional trajectory. These data are in agreement with the assumption that some planes of 3-CLT reflect the activity of underlying generators. However, the loop which contains the planar segment is a better indicator of the global electrical activity of the source. Plane C (P3) would have a contralateral source which is probably not the SOC but the afferent curved fibers of the TB close to the contralateral SOC.

Animals↗

Psychomotor decline can be described by discontinuities in response trajectories.

Force exerted in the isometric button-press response in a choice reaction time experiment was measured in order to study discontinuities in the response trajectory. Groups of young and elderly subjects were compared on performance with four choice reaction time tasks of varying difficulty. An additional comparison (with one task only) was made with a group of brain-damaged subjects. Velocity changes within the response trajectory were used to locate its discontinuities. The principal finding was that response discontinuities were least frequent in young subjects, intermediate in elderly, and most frequent in brain-damaged. Also, in the comparison of young and elderly across four stimulus conditions, the number of discontinuities was greater with more difficult than with easier tasks. Psychomotor decline was interpreted as an increase in the number of response discontinuities.

Adult↗

The trajectory of a dot crossing a pattern of tilted lines is misperceived.

The straight trajectory of a dot crossing a pattern of tilted lines is perceived as being sinusoidal. Manipulation of the size of the angle between the trajectory and the tilted lines, the velocity of the dot, and the distance between the tilted lines shows that the magnitude of the illusion is inversely proportional to the size of the incidence angle, to velocity, and to the distance between the lines. The illusion is interpreted as being the result of an integration process of local distortions occurring at the intersections with the tilted lines.

Humans↗

Using the illness trajectory framework to describe recovery from traumatic injury.

This paper seeks to highlight the utility of the Corbin and Strauss Chronic Illness Trajectory Framework in describing recovery from traumatic injury and encourages consideration of its implementation into contemporary trauma nursing (Corbin and Strauss, 1991; 1992). To date, few such frameworks have been proposed to sensitize health professionals to the path of recovery following traumatic injury. Although this framework was initially conceived for use in the domain of chronic illness, the lasting effects of severe traumatic injury have significant parallels to chronic conditions such as stroke (Burton, 2000) and multiple sclerosis (Miller, 1993) to which the framework has previously been applied. This paper demonstrates the Trajectory Framework as a useful structure to potentially enhance the development of post-discharge interventions for trauma survivors and encourages consideration of its implementation into the nursing management of this complex patient group.

Chronic Disease↗

Analysis and evaluation of the Trajectory Theory of Chronic Illness Management.

The development and testing of theories for use in nursing research and practice is essential for advancement of the profession. The Trajectory Theory of Chronic Illness Management is a middle-range nursing theory that has been proposed by Corbin and Strauss (1991a). Analysis and evaluation of this theory was performed using Fawcett and Downs's (1992) guidelines. Theory analysis and evaluation are important first steps before using a theory for practical purposes. Theory analysis makes a theory more understandable and helps to identify the strengths and weaknesses of the theory. Evaluation extends the analysis process by making judgments about the potential contribution of the theory based on published data. Results of the theory analysis and evaluation suggest that the Trajectory Theory has theoretical and social significance but that further theoretical work is necessary to enhance the internal consistency and parsimony of the theory. Although several authors have suggested that the theory has pragmatic adequacy, evidence for empirical adequacy of the theory is needed. Before more empirical studies are conducted, further theoretical work is recommended.

Chronic Disease↗

Integrating person-centered and variable-centered analyses: growth mixture modeling with latent trajectory classes.

BACKGROUND: Many alcohol research questions require methods that take a person-centered approach because the interest is in finding heterogeneous groups of individuals, such as those who are susceptible to alcohol dependence and those who are not. A person-centered focus also is useful with longitudinal data to represent heterogeneity in developmental trajectories. In alcohol, drug, and mental health research the recognition of heterogeneity has led to theories of multiple developmental pathways. METHODS: This paper gives a brief overview of new methods that integrate variable- and person-centered analyses. Methods discussed include latent class analysis, latent transition analysis, latent class growth analysis, growth mixture modeling, and general growth mixture modeling. These methods are presented in a general latent variable modeling framework that expands traditional latent variable modeling by including not only continuous latent variables but also categorical latent variables. RESULTS: Four examples that use the National Longitudinal Survey of Youth (NLSY) data are presented to illustrate latent class analysis, latent class growth analysis, growth mixture modeling, and general growth mixture modeling. Latent class analysis of antisocial behavior found four classes. Four heavy drinking trajectory classes were found. The relationship between the latent classes and background variables and consequences was studied. CONCLUSIONS: Person-centered and variable-centered analyses typically have been seen as different activities that use different types of models and software. This paper gives a brief overview of new methods that integrate variable- and person-centered analyses. The general framework makes it possible to combine these models and to study new models serving as a stimulus for asking research questions that have both person- and variable-centered aspects.

Adolescent↗

Trajectories of concurrent substance use disorders: a developmental, typological approach to comorbidity.

BACKGROUND: Although alcohol and tobacco use disorders are highly comorbid, little is known regarding the combined course of these disorders. METHODS: The current study utilized latent class analysis to examine longitudinal patterns of alcohol-tobacco use disorder comorbidity. Participants were 449 young adults (baseline age, 18.5 years; 48% male; 51% with paternal history of alcoholism) assessed five times over 7 years. RESULTS: Five longitudinal types of alcohol or tobacco use disorder over time were identified: nondiagnosing; developmentally limited alcohol use disorder; chronic alcohol use disorder; chronic tobacco use disorder; and comorbid alcohol and tobacco use disorder. These typologies were distinguishable on the basis of family history of alcoholism status and sex. Etiologically important third variables (alcohol expectancies, behavioral undercontrol, childhood stressors) mediated the relation between family history and the latent classes. CONCLUSIONS: Characterizations of alcohol use disorders typically fail to consider important sources of heterogeneity such as course or comorbidity. By simultaneously modeling developmental course and comorbidity with tobacco dependence, we were able to identify distinct trajectories of single and concurrent substance use disorders. Such multi-substance trajectories represent meaningful subtypes that, although sharing substantial common influences, have unique etiologic correlates. Additionally, these subtypes might represent distinct groups from the perspective of intervention strategies.

Adolescent↗

The effects of cosmic particle radiation on pocket mice aboard Apollo XVII: VII. Cosmic ray particle dosimetry and trajectory tracing.

Five pocket mice (Perognathus longimembris) were flown on Apollo XVII, each with a solid-state (plastic) nuclear track detector implanted beneath its scalp. The subscalp detectors were sensitive to HZE cosmic ray particles with a LET larger than or equal to 0.15 million electron volts per micrometer (MeV/mjm). A critical aspect of the dosimetry of the experiment involved tracing individual particle trajectories through each mouse head from particle tracks registered in the individual subscalp detectors, thereby establishing a one-to-one correspondence between a trajectory location in the tissue and the presence or absence of a lesion. The other major aspect was the identification of each registered particle. An average of 16 particles with Z larger than or equal to 6 and 2.2 particles with Z larger than or equal to 20 were found per detector. The track density, 29 tracks/cm2, when adjusted for detection volume, was in agreement with the photographic emulsion data from an area dosimeter located next to the flight package.

Animals↗

Trajectory of psychological risk and incident hypertension in middle-aged women.

The aim of the study was to test the hypotheses that the trajectory of psychological risk (ie, persistent or increasing measures of depression and anxiety symptoms, anger, and low social support over time) increases the risk for the development of hypertension and that blood pressure levels fluctuate with psychological changes in women. Initially, healthy normotensive middle-aged women (n=541; 90.6% white, 8.9% African American) were followed across an average of 9.2 years of follow-up. Psychological characteristics were assessed repeatedly via standardized questionnaires, and Cox proportional hazards and random regression models were used to analyze their impact, adjusting for hypertension risk factors (age, race, years of education, parental history of hypertension, baseline blood pressure, body mass index, physical activity, alcohol use, and cigarette smoking). Seventy-five women became hypertensive during the follow-up period. Baseline levels of depression, anxiety, anger, and social support did not predict subsequent hypertension. A high level of anxiety throughout the follow-up, an increase in the level of feelings of anger, and a decrease in the level of social support over the follow-up were significant predictors of hypertension incidence (all P<0.05), although covariate adjustment reduced some of the significance levels to nonsignificance. In women, increases in depressive symptoms were significantly associated (P=0.003) with concurrent increases in the level of systolic blood pressure, especially among hypertensive patients (P=0.0001). Increasing levels of anger, decreasing levels of social support, and high anxiety increase the likelihood of women's development of hypertension in midlife. These results emphasize the importance of evaluating the trajectory of psychological risk during the period of evolving hypertension.

Adult↗

Birth trajectory under changing fertility conditions.

An initially stable population of women is assumed to shift its reproductive behavior to a different level either abruptly or in a prescribed gradual fashion. A closed-form solution which is exact up to about 30 years after the reproductive adjustment is found for the resulting birth trajectory. Exact expressions are also found for the long-time asymptotic behavior of both the birth trajectory and the total population size when the shift in reproductive behavior is to bare replacement level. Accurate approximations to these asymptotic results are then derived and used to illustrate why a growing population continues to grow even after shifting to bare replacement reproductive behavior.

Age Factors↗