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Mechanism of head and neck response to -Gx impact acceleration: a math modeling approach.

Mathematical modeling has attained wider acceptance in recent years. In particular, the use of computer programs to simulate the dynamic response of a human in a crash situation has become an attractive alternative to full-scale experimental testing. This paper analyzes data on the dynamic response of the living human head and neck to -Gx impact acceleration, where the motion of the subject's head and neck in the midsagittal plane was monitored with inertial instrumentation and high-speed photography for confirmation. The Calspan "3D Computer Simulator of Motor Vehicle Crash Victims" was used to predict expected responses for the deceleration pulses employed. These estimates were compared to the fully instrumented human test runs. The standard 15-segment and 14-joint representation of the occupant was modified to include two sternoclavicular joints, increasing the articulation in the upper torso. Analysis of the data indicated that muscular activity in the head and neck seemed to be evident and does influence motion of the head, even at relatively high (10-G peak, 530 G/s onset) acceleration levels. Simulation of muscular contraction, using a spring-damper arrangement, improved the results significantly. Additionally, possible limitations to head-to-neck motion, such as ligament restrictions, were also modeled.

Acceleration↗

Chronic pain, stress, and the dynamics of affective differentiation.

We describe a program of research examining how the relationship between positive and negative affect varies both between individuals and within individuals over time. This Dynamic Model of Affect (DMA) proposes that under conditions that promote maximal information processing, positive and negative affective systems function relatively independently. In contrast, under conditions characterized by uncertainty, including pain and stress, the affects become strongly inversely related. Included in our consideration are potential individual differences in the ability to sustain affective differentiation during pain and other stressors and the implications of this model for perceptions of social relations and for interventions to improve well-being among the chronically ill.

Affect↗

Modeling the topological organization of cellular processes.

The cell as a dynamical system presents the characteristics of having a dynamical structure. That is, the exact phase space of the system cannot be fixed before the evolution and integrative cell models must state the evolution of the structure jointly with the evolution of the cell state. This kind of dynamical systems is very challenging to model and simulate. New programming concepts must be developed to ease their modeling and simulation. In this context, the goal of the MGS project is to develop an experimental programming language dedicated to the simulation of this kind of systems. MGS proposes a unified view on several computational mechanisms (CHAM, Lindenmayer systems, Paun systems, cellular automata) enabling the specification of spatially localized computations on heterogeneous entities. The evolution of a dynamical structure is handled through the concept of transformation which relies on the topological organization of the system components. An example based on the modeling of spatially distributed biochemical networks is used to illustrate how these notions can be used to model the spatial and temporal organization of intracellular processes.

Algorithms↗

Dynamic sensorimotor interactions in locomotion.

Locomotion results from intricate dynamic interactions between a central program and feedback mechanisms. The central program relies fundamentally on a genetically determined spinal circuitry (central pattern generator) capable of generating the basic locomotor pattern and on various descending pathways that can trigger, stop, and steer locomotion. The feedback originates from muscles and skin afferents as well as from special senses (vision, audition, vestibular) and dynamically adapts the locomotor pattern to the requirements of the environment. The dynamic interactions are ensured by modulating transmission in locomotor pathways in a state- and phase-dependent manner. For instance, proprioceptive inputs from extensors can, during stance, adjust the timing and amplitude of muscle activities of the limbs to the speed of locomotion but be silenced during the opposite phase of the cycle. Similarly, skin afferents participate predominantly in the correction of limb and foot placement during stance on uneven terrain, but skin stimuli can evoke different types of responses depending on when they occur within the step cycle. Similarly, stimulation of descending pathways may affect the locomotor pattern in only certain phases of the step cycle. Section ii reviews dynamic sensorimotor interactions mainly through spinal pathways. Section iii describes how similar sensory inputs from the spinal or supraspinal levels can modify locomotion through descending pathways. The sensorimotor interactions occur obviously at several levels of the nervous system. Section iv summarizes presynaptic, interneuronal, and motoneuronal mechanisms that are common at these various levels. Together these mechanisms contribute to the continuous dynamic adjustment of sensorimotor interactions, ensuring that the central program and feedback mechanisms are congruous during locomotion.

Animals↗

Washington State's Basic Health Plan: choices and challenges.

The current turbulence characterizing the health sector has engendered a limited number of state-level experiments to provide health services for the nation's 37 million uninsured. The issues and challenges generated by each program's design and implementation vary. By examining the experience of one such state program, the Washington Basic Health Plan, in some detail, this paper contributes to the policy debate regarding the possible range of solutions available to address the issue of "the uninsured." By analyzing the array of design choices available at the time the program was enacted, and why certain options were chosen rather than others, this paper points to the complex interaction of political dynamics, public policy development, and program implementation.

Health Policy↗

Developing a quality assurance program through teamwork.

Clinic nurses and nursing faculty members collaborated to develop a quality assurance program appropriate to three different clinic sites. The nurse consultants maintained a supportive, rather than a leadership, role while guiding the three groups of clinic nurses through the change process structured around the familiar structure, process, outcome framework. Regularly scheduled meetings and the cooperative distribution and accomplishment of clearly defined tasks not only have produced an excellent standardized nursing quality assurance program but also forged a dynamic nursing team.

Goals↗

Comparison of IMG-dependent and non-IMG-dependent residencies in the National Resident Matching Program.

OBJECTIVE: To provide insight into the dynamics that determine the pattern of participation of international medical graduates (IMGs) in graduate medical education (GME). DESIGN: Data on IMG-dependent programs (ie., those having at least 50% of first-year positions filled by IMGs) and non-IMG-dependent programs in 6 core specialties (internal medicine, family practice, obstetrics and gynecology, surgery, pediatrics, and psychiatry) were matched with application data from the 1989 and 1995 National Resident Matching Program (NRMP). MAIN OUTCOME MEASURES: Participation of IMG-dependent and non-IMG-dependent programs in the 1995 NRMP and the pattern of US medical graduate (USMG) and IMG applications to these programs in 1989 and 1995. RESULTS: Of the 1634 programs in the 6 specialties, 93.5% participated in the 1995 NRMP. The 1165 non-IMG-dependent programs were significantly more likely to participate in the NRMP and were slightly more likely to fill their offered positions than were the 469 IMG-dependent programs. Specifically, IMGs constituted 76% of applicants to IMG-dependent programs and only 14% of applicants to non-IMG-dependent programs. Changes in NRMP data between 1989 and 1995 indicated that the number of IMG applications to IMG-dependent programs increased 88.7%, as did the number of applicants ranked. CONCLUSIONS: Persistent differences exist in the mix of USMGs and IMGs applying through the NRMP to IMG-dependent and non-IMG-dependent programs. Over time, programs that enroll large numbers of IMGs are likely to experience an increase in the number and proportion of applications from IMGs and a decrease in the number and proportion of applications from USMGs. If policies are adopted to limit IMG access to GME, IMG-dependent programs may be unable to recruit USMGs unless the total number of GME programs or the quality of existing programs fundamentally changes.

Foreign Medical Graduates↗

Environmental programming of stress responses through DNA methylation: life at the interface between a dynamic environment and a fixed genome.

Early experience permanently alters behavior and physiology. These effects are, in part, mediated by sustained alterations in gene expression in selected brain regions. The critical question concerns the mechanism of these environmental "programming" effects. We examine this issue with an animal model that studies the consequences of variations in mother-infant interactions on the development of individual differences in behavioral and endocrine responses to stress in adulthood. Increased levels of pup licking/grooming by rat mothers in the first week of life alter DNA structure at a glucocorticoid receptor gene promoter in the hippocampus of the offspring. Differences in the DNA methylation pattern between the offspring of high- and low-licking/grooming mothers emerge over the first week of life; they are reversed with cross-fostering; they persist into adulthood; and they are associated with altered histone acetylation and transcription factor (nerve growth factor-induced clone A [NGFIA]) binding to the glucocorticoid receptor promoter. DNA methylation alters glucocorticoid receptor expression through modifications of chromatin structure. Pharmacological reversal of the effects on chromatin structure completely eliminates the effects of maternal care on glucocorticoid receptor expression and hypothalamic-pituitary-adrenal (HPA) responses to stress, thus suggesting a causal relation between the maternally induced, epigenetic modification of the glucocorticoid receptor gene and the effects on stress responses in the offspring. These findings demonstrate that the structural modifications of the DNA can be established through environmental programming and that, in spite of the inherent stability of this epigenomic marker, it is dynamic and potentially reversible.

Animals↗

Computer-assisted dynamic integration of multiple medical thesauruses.

We have previously described a user-interactive rule-based computer program (Dyna-SaurI) designed for dynamic thesaurus integration, and demonstrated its efficacy on integrating dermatological subsets of the MeSH and SNOMED thesauruses. In the present study, we have refined our rules for merging and mapping multiple thesauruses and tested these rules. We then applied them with a set of optimized parameters to the integration of a third thesaurus, a subset of the International Coding Index for Dermatology, with the Integrated MeSH-SNOMED thesaurus. The parameter changes resulted in improved ranking of more specific and conceptually closer terms.

Abstracting and Indexing↗

Uniform depth dose distribution for biological irradiation using negative pions.

A simple, flexible technique has been developed to generate uniform depth dose profiles for the biomedical pion beam at TRIUMF using dynamic momentum control and linear programming. Either the entrance dose or the irradiation time required for a certain dose over the uniform region can be minimised. The dynamic momentum control can operate automatically under computer control even with a highly unstable beam. Cell survival profiles have been obtained for this uniform dose distribution using the gelatin technique. The RBE increases with increasing depth through the uniform dose region.

Animals↗

Electromyographic analysis of the glenohumeral muscles during a baseball rehabilitation program.

Many exercises are used to strengthen the glenohumeral muscles, but there have been limited studies to evaluate the exercises. Thus, the purpose of this study was to decide how the muscles responsible for humeral motion can best be exercised in a rehabilitation program for the throwing athlete. Dynamic, fine wire, intramuscular electromyography was carried out in 15 normal male volunteers performing 17 shoulder exercises derived from a shoulder rehabilitation program used by professional baseball clubs. The four rotator cuff muscles were studied, as well as other positioners of the humerus, including the pectoralis major, latissimus dorsi, and three portions of the deltoid. The electromyographic activity was synchronized with cinematography and averaged over 30 degrees arcs of motion. An exercise was considered to be a significant challenge for a muscle if it generated at least 50% of its predetermined maximum contraction over three consecutive arcs (i.e., a 90 degrees range). Four exercises were consistently found to be among the most challenging exercises for every muscle. These shoulder exercises consisted of 1) elevation in the scapular plane with thumbs down, 2) flexion, 3) horizontal abduction with arms externally rotated, and 4) press-up. This study documents that the minimum for an effective and succinct rehabilitation protocol for the glenohumeral muscles would include these exercises.

Adult↗

Three-dimensional structure of soybean trypsin/chymotrypsin Bowman-Birk inhibitor in solution.

The three-dimensional structure of soybean trypsin/chymotrypsin Bowman-Birk inhibitor in solution has been determined by two-dimensional 1H nuclear magnetic resonance spectroscopy and dynamical simulated annealing using the program XPLOR. The structure was defined by 907 NOEs involving intra- and interresidue contacts which served as distance constraints for a protocol of dynamical simulated annealing. In addition, 48 phi angle constraints involving non-proline amino acids, 29 chi angle constraints, six omega angle constraints for the X-Pro peptide bond, and 35 stereoassignments for prochiral centers were incorporated during the course of the calculation. The protein is characterized by two distinct binding domains for serine protease. Each domain is comprised of a beta-hairpin (antiparallel beta-sheet and a cis-proline-containing type VIb reverse turn) with a short segment making a third strand of antiparallel beta-sheet. The structure determination and refinement are described, and the structure is compared to other structures of Bowman-Birk inhibitors as well as other families of serine protease inhibitors.

Amino Acid Sequence↗

Longitudinal Multi-Organ Transcriptomic Atlas of Salt-Induced Hypertension.

BACKGROUND: Salt-sensitive hypertension is a prevalent and clinically significant subtype of hypertension, where increased dietary salt intake elevates blood pressure and causes injury to multiple organ systems. Despite extensive research, dynamic molecular changes and conserved versus organ-specific transcriptional programs in hypertensive multi-organ damage remain poorly understood. Defining complex molecular pathways both in a temporal sequence and in an organ-specific manner is essential for developing targeted, precision therapies to mitigate hypertensive disease burden. METHODS: We generated a longitudinal multi-organ transcriptomic atlas of salt-sensitive hypertension using RNA sequencing of kidney cortex, kidney medulla, heart, and liver from Dahl salt-sensitive rats across four disease stages. A comprehensive bioinformatic analysis mapped dynamic transcriptional programs, evaluated 50 biological pathways, and defined upstream regulators. Histological and biochemical assays complemented transcriptomic analysis, while integration with human genome-wide association studies (GWAS) and compound-transcriptome analysis provided translational insights and identified candidate therapeutics. RESULTS: Salt-induced hypertension elicited both shared and tissue-specific transcriptional programs that evolved with disease progression. The kidney medulla showed robust early immune activation with metabolic suppression, while the cortex exhibited transient metabolic activation before declining and initiating immune activation. The liver and heart showed time-dependent metabolic and inflammatory remodeling. Cross-organ comparisons revealed a shared early proliferative response that converged on proinflammatory and fibrotic signatures. Upstream regulator analysis identified 79 time- and tissue-specific transcription factors associated with gene expression dynamics. GWAS integration analysis revealed endocrine signaling, ion transport, lipid metabolism, and detoxification as conserved pathways across species, underscoring the translational relevance of the model and study. Predictive compound-transcriptome analyses identified kinase inhibitors targeting phosphoinositide 3-kinase, mechanistic target of rapamycin and cyclin-dependent kinases as top candidates to counteract maladaptive transcriptional programs. CONCLUSIONS: This study defines temporal and tissue-specific transcriptomic remodeling in salt-sensitive hypertension and highlights the need for precision interventions to prevent progressive organ damage.

Journal Article↗

Dynamic scintigraphy with high temporal resolution. Phase dynamic studies of rapid periodical processes.

The theory and general method of construction of the phase dynamic studies of rapid periodical processes with high temporal resolution is described briefly. Moreover, problems are discussed that are associated with the introduction of external pulses into dynamic studies in LIST-mode, the spatial and temporal reconstruction from LIST-mode, the computer's construction of phase dynamic studies, the selection of correct cycles, the creation of phase histograms and processing of the phase studies. The method is illustrated by a general program LIST leads to PHASE DYNAM. STUDY created for Clincom apparatus. In addition to the general method, there is mentioned here the modification of the simplified procedure--a well-known EKG-gated method. Some aspects of the method are documented by the results of phantom measurement and clinical examinations.

Electrocardiography↗

TRAJELIX: a computational tool for the geometric characterization of protein helices during molecular dynamics simulations.

We have developed a computer program with the necessary mathematical formalism for the geometric characterization of distorted conformations of alpha-helices proteins, such as those that can potentially be sampled during typical molecular dynamics simulations. This formalism has been incorporated into TRAJELIX, a new module within the SIMULAID framework (http://inka.mssm.edu/~mezei/simulaid/) that is capable of monitoring distortions of alpha-helices in terms of their displacement, global and local tilting, rotation around their axes, compression/extension, winding/unwinding, and bending. Accurate evaluation of these global and local structural properties of the helix can help study possible intramolecular and intermolecular changes in the helix packing of alpha-helical membrane proteins, as shown here in an application to the interacting helical domains of rhodopsin dimers. Quantification of the dynamic structural behavior of alpha-helical membrane proteins is critical for our understanding of signal transduction, and may enable structure-based design of more specific and efficient drugs.

Algorithms↗

Effects of exercise frequency on functional fitness in older adult women.

This study evaluated the effects of exercise frequency on functional fitness in older women participating in a 12-week exercise program. Participants (67.8+/-4.6 years) were divided into three different exercise groups (I, II, and III; n=34) and a control group (Group C; n=11). Group I participated in a 90-min exercise program once a week, for 12 weeks, while Group II attended it twice a week, and Group III attended three times a week. The exercise program consisted of a 10-min warm-up, 20 min of walking, 30 min of recreational activities, 20 min of resistance training, and a 10-min cool-down. The following items were measured before and after the program: muscular strength, muscular endurance, dynamic balance, coordination, and cardiorespiratory fitness (6-min walking distance). Comparisons of baseline and post-intervention measures showed significantly greater improvements in body weight, coordination, and cardiorespiratory fitness for Group III compared to the other groups (p<0.05). In addition, the greatest improvements in body fat, muscular endurance, and dynamic balance were also observed in Group III (p<0.05). However, no significant differences were found in muscular strength. Older women who participate in an exercise program three times a week gain greater functional fitness benefits than those who exercise less frequently. In order to improve functional fitness in older women, an exercise frequency of at least three times each week should be recommended.

Activities of Daily Living↗