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PubMedDate not supplied

Spatial signaling in the development and function of neural connections.

In the vertebrate central nervous system, afferent axons find their appropriate target structures under the influence of local environmental cues. In many target regions, appropriate patterns of activity in the afferents are also required to establish normal mappings between the source cells and the target region. Specific mappings arise in these targets because temporal contiguity in firing is somehow transformed into spatial contiguity of synaptic contacts. In this article, we propose a theory that utilizes the covariance of a transient diffusive signal produced at active synapses with the firing of presynaptic axon terminals to account for many of these activity-dependent features of vertebrate neuroanatomy. Computer simulations of the growth of axons within a three-dimensional volume of neural tissue reveal the generality of the proposed mechanism in accounting for the self-organization of a broad range of diverse neuroanatomical structures, including those in the cerebral cortex. The proposed mechanism is consistent with detailed anatomical and physiological data, and direct experimental tests of predictions of the theory are suggested.

Animals↗
PubMed1996

Nursing theory: everything the artist spits is art?

This paper explores the concept and utility of nursing theory in and for the practice of nursing. Working from the premise that many nurse practitioners appear uncertain as to the value of theory in relation to their everyday working experience, the paper investigates the contribution nursing theory makes in terms of sustaining and developing nursing as a practice discipline. The fact that nursing theory remains at once poorly evaluated, articulated or understood appears to be compounded by a general perception of nurse theorists as being removed from the realities of the practice setting and by the confusion precipitated, not least, by the semantic ambiguity engendered by their writings. The paper reviews the complex relationships extant between the development of nursing theory in regard to its utility for nursing practice, and concludes by suggesting a practice-led perspective by which nursing theory may be better articulated and assimilated within the discipline. In order to facilitate the study, it has been necessary to investigate the historical, theoretical and philosophical imperatives pertaining not only to the development of nursing theory but to nursing research and nursing practice per se.

Forecasting↗
PubMed2005

Examining the relationship between executive functions and restricted, repetitive symptoms of Autistic Disorder.

The executive function theory was utilized to examine the relationship between cognitive process and the restricted, repetitive symptoms of Autistic Disorder (AD). Seventeen adults with AD were compared to 17 nonautistic controls on a new executive function battery (Delis-Kaplin Executive Function Scales). Restricted, repetitive symptoms were measured by a variety of instruments (i.e., the Autism Diagnostic Observation Schedule, Autism Diagnostic Interview-Revised, Gilliam Autism Rating Scale, and the Aberrant Behavior Checklist). The study replicated the executive function profile that has been reported in adults with AD. In addition to the replication findings, the study found several executive processes (i.e., cognitive flexibility, working memory, and response inhibition) were highly related to the restrictive, repetitive symptoms of AD; whereas, other executive process (i.e., planning and fluency) were not found to be significantly correlated with restricted, repetitive symptoms. Similarly, we found an executive function model consisting of relative strengths and deficits was the best predictor of restricted, repetitive symptoms of autism. The implications for the executive function theory and how the theory predicts core symptoms of autism are discussed.

Adolescent↗
PubMed1999

Molecular recognition in nicotinic acetylcholine receptors: the importance of pi-cation interactions.

We explore the significance of pi-cation interactions in the binding of ligands to nicotinic acetylcholine receptors. Specifically, the Austin method of semiempirical molecular orbital theory is utilized to estimate the interaction of aromatic amino acid side chains with the cation-containing heterocyclic ring fragments of nicotinic ligands. Variational interaction energies (E(i)) of side chain-ligand fragment pairs are shown to be distance-dependent and follow a Morse-like potential function. The tryptophan side chain shows the most pronounced interaction with the cation fragments, followed by tyrosine and phenylalanine. For a given side chain, cationic fragments exhibit characteristically different E(i) profiles, with the azabicyclo[2.2.1]heptane fragment of the potent nicotinic ligand epibatidine eliciting the greatest interaction energy of the study set. Most significantly, the minimum energy values calculated for numerous fragments correlate with the binding affinity of the parent ligands- we show this to be the case for heteropentameric (alpha4beta2) and homopentameric (alpha7) nicotinic acetylcholine receptor subtypes. Furthermore, intermolecular distances corresponding to the Morse-like potential minimum also correlate with high-affinity binding. A number of parallel calculations were conducted at the Hartree-Fock 6-31G ab initio level of theory in an effort to substantiate these findings.

Amino Acids↗
PubMedDate not supplied

Choosing and using contraception: toward a theory of women's contraceptive self-care.

Thirty women of varying ethnicity and socioeconomic status, who were actively seeking to avoid pregnancy, were interviewed concerning their lifetime experience with contraceptive use. The resulting description, Women's Contraceptive Self-Care, was divided into four processes: the central process, Choosing and Using Contraception, and three contextual processes. Forestalling Pregnancy was defined as using contraceptive methods or behaviors to prevent or delay childbearing. Assigning the Burden of Contraceptive Responsibility was defined as assuming responsibility for contraception or shifting that responsibility to a partner. Negotiating with Those who Control Contraception was defined as maneuvering among individuals and agencies that permit or hinder access to contraceptive methods and behaviors. Each process is comprised of thematic clusters and/or themes that are defined and illustrated.

Adult↗
PubMed1976

A new approach to psychopathology.

A new approach to psychopathology based on the psychology of integration as applied to psychological states is outlined. Because all raw behavior occurs only in the form of psychological states, all formulations of psychopathology must refer to integrative disorders that are postulated to underlie all pathological or defective behaviors. Disintegration is the one common factor found in all mental disorders. Lack of integration underlies most inadaptability. The classical field of psychopathology, which formerly was limited to the consideration of formal psychiatric disorders, now is expanded to include deficits, imbalances and disintegrations of acute or chornic nature that result in erroneous or less than perfect judgments. Judgment is considered to reflect the quality of underlying integrative processes. Judgmental defects that lead to maladaptive decisions inevitably must result in maladjustment and/or less than perfect performance. It is necessary to differentiate between (a) integrative disorders per se, and (b) the personal-social effects of positive or negative integrations organized by healthy or unhealthy factors. Criminals may be well integrated in their asocial activities, but socially undesirable because organized about the criminal ethic. Postulates are presented that outline the theoretical assumptions upon which integrative psychopathology is based. This approach utilizes classic theories such as the Freudian psychopathology of everyday life when valid and relevant within the larger framework of integrative psychology. A differentiation is made between hierarchical levels of increasingly complex factors that may organize integration.

Autonomic Nervous System↗
PubMed2002

Determination of individual cell Michaelis-Menten constants.

BACKGROUND: A novel methodology for the measurement and analysis of apparent K(M) (Michaelis-Menten constant) and V(MAX) values of individual cells is suggested. It is based on a mathematical model that considers substrate influx into the cell, its intracellular enzymatic hydrolysis, and the product efflux. The mathematical formulation was approximated linearly in order to analyze intracellular substrate conversion characteristics via Michaelis-Menten theory. METHODS: Utilizing static cytometry, the time dependence of the fluorescence intensity [FI(t)] emitted from prelocalized and defined FDA stained cells was recorded. This required frequent periodical measurements of the same cells, which are sequentially exposed to various fluorogenic substrate concentrations. RESULTS: Model simulations correlated with experimental results. Differences in distributions of individual K(M) and V(MAX) values of cells incubated with and without PHA were evident. Average K(M) and V(MAX) values of PHA-stimulated cells increased by 99% and 540%, respectively. CONCLUSIONS: This study may provide a tool for assessing intracellular enzymatic activity in individual intact cells under defined physiologic conditions. This may open new vistas in various areas, giving answers to critical questions arising in the field of cell and developmental biology, immunology, oncology, and pharmacology.

Flow Cytometry↗
PubMed2004

A practical valence bond method: a configuration interaction method approach with perturbation theoretic facility.

The previously developed valence bond configuration interaction (VBCI) method (Wu, W.; Song, L.; Cao, Z.; Zhang, Q.; Shaik, S., J. Phys. Chem. A, 2002, 105, 2721) that borrows the general CI philosophy of the MO theory, is further extended in this article, and its methodological features are improved, resulting in three accurate and cost-effective procedures: (a) the effect of quadruplet excitation is incorporated using the Davidson correction, such that the new procedure reduces size consistency problems, with due improvement in the quality of the computational results. (b) A cost-effective procedure, named VBCI(D, S), is introduced. It includes doubly excited structures for active electrons and singly excited structures for inactive pairs. The computational results of VBCI(D, S) match those of VBCISD with much less computational effort than VBCISD. (c) Finally, a second-order perturbation theory is utilized as a means of configuration selection, and lead to considerable reduction of the computational cost, with little or no loss in accuracy. Applications of the new procedures to bond energies and barriers of chemical reactions are presented and discussed.

Journal Article↗
PubMed2004

Regression models for relative survival.

Four approaches to estimating a regression model for relative survival using the method of maximum likelihood are described and compared. The underlying model is an additive hazards model where the total hazard is written as the sum of the known baseline hazard and the excess hazard associated with a diagnosis of cancer. The excess hazards are assumed to be constant within pre-specified bands of follow-up. The likelihood can be maximized directly or in the framework of generalized linear models. Minor differences exist due to, for example, the way the data are presented (individual, aggregated or grouped), and in some assumptions (e.g. distributional assumptions). The four approaches are applied to two real data sets and produce very similar estimates even when the assumption of proportional excess hazards is violated. The choice of approach to use in practice can, therefore, be guided by ease of use and availability of software. We recommend using a generalized linear model with a Poisson error structure based on collapsed data using exact survival times. The model can be estimated in any software package that estimates GLMs with user-defined link functions (including SAS, Stata, S-plus, and R) and utilizes the theory of generalized linear models for assessing goodness-of-fit and studying regression diagnostics.

Adolescent↗
PubMed1984

Affective information processing and the assessment of anxiety.

A conceptualization of anxiety as comprising three loosely coupled response systems of overt behavior, verbal report, and physiological activation has proven useful in clinical and theoretical work. With this framework as a starting point, an information-processing approach to the study of emotion is described. Emotions are conceived as affective programs within the brain, with information coded as propositions organized into associative networks. Affective expression results when such a network is accessed and processed, which can occur when a sufficient number of propositions are activated by environment stimuli and/or internal associations. It is hypothesized that information about the expressive physiology is an integral component of the associative structure, and that processing of the network accordingly results in measurable psychophysiological response. Data from studies of emotional imagery, as well as other areas of research, are reviewed in support in these theories. The utility of this approach for the assessment of anxiety disorders is discussed, and results of clinical studies are presented to suggest that individual differences in accessing and processing emotional information may bear significant implications for prognosis and treatment selection. It is speculated that differences among the anxiety disorders could be interpreted in terms of the degree of cognitive organization of the network, leading to potential refinement of current diagnostic categories. In conclusion, cognitive psychology paradigms are discussed in terms of their application to the assessment and treatment of anxiety disorders.

Anxiety↗
PubMed2006

Navigating social class roles in community research.

This paper describes the first author's attempt to collect data in a homeless shelter without attending to her role in the social class hierarchy of the organization. The author's egalitarian approach towards the homeless clients, and her lack of involvement in "staff-only" activities, transgress the social class norms within the organizational structure. While the author is successful in gaining the trust of the homeless clients, her approach alienates shelter staff, especially those in the higher echelons of the social hierarchy. The concepts of classism, world views, and Social Identity Theory, are utilized to discuss the dilemma faced by researchers who want to challenge, or work outside, a setting's status quo.

Adolescent↗
PubMed2007

Use of context in pragmatic language comprehension by children with Asperger syndrome or high-functioning autism.

Utilizing relevance theory, this study investigated the ability of children with Asperger syndrome (AS) and high-functioning autism (HFA) to use context when answering questions and when giving explanations for their correct answers. Three groups participated in this study: younger AS/HFA group (age 7-9, n=16), older AS/HFA group (age 10-12, n=23) and a normally functioning control group (age 7-9, n=23). The results indicated that the younger AS/HFA group did less well when answering contextually demanding questions compared to the control group, and the performance of the older AS/HFA group fell in between the younger AS/HFA group and the control group. Both AS/HFA groups had difficulties explaining their correct answers, suggesting that they are not always aware of how they have derived answers from the context.

Aptitude↗
PubMed1987

The newly hired hospital staff nurse's professionalism, satisfaction and alienation.

In a previously reported panel study [Speedling et al. (1981). Int. J. Nurs. Stud. 18, 217-225], 180 Registered Nurses, three-quarters new graduates, were given questionnaires at time of hire and a year later. Using the panel study data, relationships among bureaucratic-professional role conception, actual situation and role discrepancy, and importance of job factors, job satisfaction and alienation, as well as age and length of stay at termination for time of hire only, are explored in this follow-up report. Mean bureaucratic actual situation (t = -5.18, P less than 0.001), bureaucratic role discrepancy (t = -2.77, P less than 0.01) and alienation (t = -2.36, P less than 0.05) increased, while professional actual situation (t = 3.39, P less than 0.01) and importance of job factors (t = 2.33, P less than 0.05) decreased during this first year of employment. In correlational analysis, at the time of hiring relationships were found between numerous variables, including: bureaucratic role conception with alienation (r = 0.17, P less than 0.05); bureaucratic actual situation with alienation (r = 0.19, P less than 0.05); professional role conception with alienation (r = -0.20, P less than 0.05) and with job satisfaction (r = -0.35, P less than 0.001); professional actual situation with job satisfaction (r = -0.19, P less than 0.05); and professional role discrepancy with job satisfaction (r = 0.23, P less than 0.01). A year after hiring, many relationships were found, including professional actual situation with job satisfaction (r = 0.26, P less than 0.05) and alienation with job satisfaction (r = -0.33, P less than 0.01). In stepwise regression analysis, age accounted for 8% of the variance in the importance of job factors (P less than 0.05), professional role conception for 28% of the variance in job satisfaction (P less than 0.001) at time of hire. A year after hiring, alienation and job satisfaction accounted for 12% of the variance in each other (P less than 0.01). As in the correlational analysis, there were many relationships among the bureaucratic-professional variables. Professional socialization theory was utilized in this study, helping to clarify the relationships among staff nurse professionalism, satisfaction and alienation.

Adult↗
PubMed1990

Social evaluation with variable population size: an alternative concept.

This paper deals with some consequences of certain population changes on social welfare considerations. In particular, a general concept for expressing value judgments about how the addition of 1 further agent to some given society should affect social welfare and a replication invariance condition are introduced and discussed. An axiomatic framework for welfare orderings based on a generalized averaging procedure applied to individual utilities is provided.

Behavior↗
PubMed1993

The old-age security hypothesis revisited.

"Children's altruism toward parents is allowed in a two-overlapping-generations model with endogenous fertility. Parents raise children because, when retired, they expect gifts from their children who are essentially a capital good. Individuals' behavior between generations is examined by analyzing a Nash equilibrium, which is then compared with a social planner's optimal allocation. The pay-as-you-go public pension program is viewed as the optimal gifts from the optimal allocation when the latter is implemented. The effect on fertility of the introduction of a capital market is also analyzed. The validity of the old-age security hypothesis is shown to depend on the parameters of utility and cost functions."

Behavior↗
PubMed2006

Observation of anomalous diffusion in excised tissue by characterizing the diffusion-time dependence of the MR signal.

This report introduces a novel method to characterize the diffusion-time dependence of the diffusion-weighted magnetic resonance (MR) signal in biological tissues. The approach utilizes the theory of diffusion in disordered media where two parameters, the random walk dimension and the spectral dimension, describe the evolution of the average propagators obtained from q-space MR experiments. These parameters were estimated, using several schemes, on diffusion MR spectroscopy data obtained from human red blood cell ghosts and nervous tissue autopsy samples. The experiments demonstrated that water diffusion in human tissue is anomalous, where the mean-square displacements vary slower than linearly with diffusion time. These observations are consistent with a fractal microstructure for human tissues. Differences observed between healthy human nervous tissue and glioblastoma samples suggest that the proposed methodology may provide a novel, clinically useful form of diffusion MR contrast.

Algorithms↗