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PubMed1990

A model of methods for influencing prescribing: Part I. A review of prescribing models, persuasion theories, and administrative and educational methods.

The purpose of this literature review is to develop a model of methods to be used to influence prescribing. Four bodies of literature were identified as being important for developing the model: (1) Theoretical prescribing models furnish information concerning factors that affect prescribing and how prescribing decisions are made. (2) Theories of persuasion provide insight into important components of educational communications. (3) Research articles of programs to improve prescribing identify types of programs that have been found to be successful. (4) Theories of human inference describe how judgments are formulated and identify errors in judgment that can play a role in prescribing. This review is presented in two parts. This article reviews prescribing models, theories of persuasion, studies of administrative programs to control prescribing, and sub-optimally designed studies of educational efforts to influence drug prescribing.

Cognition↗

PubMedDate not supplied

Modelling the growth curve of Maine-Anjou beef cattle using heteroskedastic random coefficients models.

A heteroskedastic random coefficients model was described for analyzing weight performances between the 100th and the 650th days of age of Maine-Anjou beef cattle. This model contained both fixed effects, random linear regression and heterogeneous variance components. The objective of this study was to analyze the difference of growth curves between animals born as twin and single bull calves. The method was based on log-linear models for residual and individual variances expressed as functions of explanatory variables. An expectation-maximization (EM) algorithm was proposed for calculating restricted maximum likelihood (REML) estimates of the residual and individual components of variances and covariances. Likelihood ratio tests were used to assess hypotheses about parameters of this model. Growth of Maine-Anjou cattle was described by a third order regression on age for a mean growth curve, two correlated random effects for the individual variability and independent errors. Three sources of heterogeneity of residual variances were detected. The difference of weight performance between bulls born as single and twin bull calves was estimated to be equal to about 15 kg for the growth period considered.

Algorithms↗

PubMed2005

Modeling Lactococcus lactis using a genome-scale flux model.

BACKGROUND: Genome-scale flux models are useful tools to represent and analyze microbial metabolism. In this work we reconstructed the metabolic network of the lactic acid bacteria Lactococcus lactis and developed a genome-scale flux model able to simulate and analyze network capabilities and whole-cell function under aerobic and anaerobic continuous cultures. Flux balance analysis (FBA) and minimization of metabolic adjustment (MOMA) were used as modeling frameworks. RESULTS: The metabolic network was reconstructed using the annotated genome sequence from L. lactis ssp. lactis IL1403 together with physiological and biochemical information. The established network comprised a total of 621 reactions and 509 metabolites, representing the overall metabolism of L. lactis. Experimental data reported in the literature was used to fit the model to phenotypic observations. Regulatory constraints had to be included to simulate certain metabolic features, such as the shift from homo to heterolactic fermentation. A minimal medium for in silico growth was identified, indicating the requirement of four amino acids in addition to a sugar. Remarkably, de novo biosynthesis of four other amino acids was observed even when all amino acids were supplied, which is in good agreement with experimental observations. Additionally, enhanced metabolic engineering strategies for improved diacetyl producing strains were designed. CONCLUSION: The L. lactis metabolic network can now be used for a better understanding of lactococcal metabolic capabilities and potential, for the design of enhanced metabolic engineering strategies and for integration with other types of 'omic' data, to assist in finding new information on cellular organization and function.

Bacteria, Anaerobic↗

PubMed2005

Cavernous sinus tumor model in the canine: a simulation model for cavernous sinus tumor surgery.

OBJECTIVE: The recent limitations of working hours for neurosurgical trainees carry the risk of decreasing the amount of microsurgical experience. In the absence of enough surgical exposure to some pathological states, an alternative option of a more continuous source of tactile and visual experience that simulates the real-life state is needed. To help with this problem, we established a cavernous sinus tumor model in the canine. METHODS: A gliosarcoma cell line that was harvested from a tumor model in nude mice was implanted in six mongrel dogs. In the first group (two dogs), the cell line was implanted in the dural leaflets of the cavernous sinus. (Immunosuppression was used in one dog.) In the second group (four dogs), the cell line was implanted in the region of the gasserian ganglion. (Immunosuppression was used in all four dogs.) The condition of each dog was followed through neurological examinations and serial magnetic resonance imaging. The cavernous sinus region later was explored, after which the dogs were later killed and histopathological evaluations of the cavernous sinus region was carried out. RESULTS: The initial cell line implanted within the dural leaflets of the cavernous sinus showed no evidence of tumor growth. The tumor grew in all four dogs that had the gliosarcoma cell line implanted in the region of the gasserian ganglion. The clinical and radiological features as well as the experience of the surgical dissection of these tumors simulated cavernous sinus tumors in humans. CONCLUSION: We established the first cavernous sinus tumor model in the canine. This model simulates the real-life pathological state, and it can be used as an alternative source of surgical experience to advance surgical skills.

Animals↗

PubMed1996

Tranilast suppresses intimal hyperplasia in the balloon injury model and cuff treatment model in rabbits.

Intimal hyperplasia is a serious problem after percutaneous transluminal coronary angioplasty (PTCA). In this study, we investigated the effects of tranilast on intimal hyperplasia in both in vivo and in vitro experiments. For the in vivo experiments, we used the balloon injury model and the cuff treatment model of rabbits fed regular chow. In the balloon injury model, tranilast decreased intimal area, intima/media ratio, stenosis ratio and vascular DNA content after endothelial injury. Also in the cuff treatment model, tranilast suppressed the intimal hyperplasia. In the in vitro experiments, we assessed the effects of tranilast on platelet-derived growth factor-induced rabbit vascular smooth muscle cell (VSMC) migration and proliferation and on collagen synthesis by VSMCs. Tranilast inhibited VSMC migration, proliferation and collagen synthesis. These results suggest that tranilast has a suppressive effect on intimal hyperplasia after a vascular injury such as PTCA.

Angioplasty, Balloon, Coronary↗

PubMed2005

Comparison of the use of a physiologically based pharmacokinetic model and a classical pharmacokinetic model for dioxin exposure assessments.

In epidemiologic studies, exposure assessments of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) assume a fixed elimination rate. Recent data suggest a dose-dependent elimination rate for TCDD. A physiologically based pharmacokinetic (PBPK) model, which uses a body-burden-dependent elimination rate, was developed previously in rodents to describe the pharmacokinetics of TCDD and has been extrapolated to human exposure for this study. Optimizations were performed using data from a random selection of veterans from the Ranch Hand cohort and data from a human volunteer who was exposed to TCDD. Assessment of this PBPK model used additional data from the Ranch Hand cohort and a clinical report of two women exposed to TCDD. This PBPK model suggests that previous exposure assessments may have significantly underestimated peak blood concentrations, resulting in potential exposure misclassifications. Application of a PBPK model that incorporates an inducible elimination of TCDD may improve the exposure assessments in epidemiologic studies of TCDD.

Body Burden↗

PubMed2004

The Lindsay Leg Club Model: a model for evidence-based leg ulcer management.

Leg Club is a unique model of community-based leg ulcer care. By providing nursing care in a non-medical, social environment, the model has several benefits: it removes the stigma associated with leg ulcers and helps isolated older people reintegrate into their communities, which in turn improves concordance and has a positive impact on healing and recurrence rates. In an atmosphere of de-stigmatisation, empathy and peer support, positive health beliefs are promoted and patients take ownership of their treatment. The Leg Club model creates a framework in which nurses, patients and local community can collaborate as partners in the provision of holistic care. The model also provides an environment for appropriate supportive education, advice and information.

Community Health Centers↗

PubMed2005

Modelling non-ignorable missing-data mechanisms with item response theory models.

A model-based procedure for assessing the extent to which missing data can be ignored and handling non-ignorable missing data is presented. The procedure is based on item response theory modelling. As an example, the approach is worked out in detail in conjunction with item response data modelled using the partial credit and generalized partial credit models. Simulation studies are carried out to assess the extent to which the bias caused by ignoring the missing-data mechanism can be reduced. Finally, the feasibility of the procedure is demonstrated using data from a study to calibrate a medical disability scale.

Activities of Daily Living↗

PubMed2005

Modeling anisotropic light propagation in a realistic model of the human head.

A Monte Carlo model capable of describing photon migration in arbitrary three-dimensional geometry with spatially varying optical properties and tissue anisotropy is presented. We use the model to explore the effects of anisotropy for optical measurements of the human head. An anisotropic diffusion equation that corresponds to our Monte Carlo model is derived, and a comparison between the Monte Carlo model and the diffusion equation solution with finite elements is given.

Adult↗

PubMed2002

Experimental models of small intestinal transplantation in rats: orthotopic versus heterotopic model.

Two kinds of surgical models of small intestinal transplantation (SITx) in rats, namely heterotopic (HIT) and orthotopic transplantion (OIT), have been reviewed. In OIT, the small intestine of the recipient is removed and the transplanted intestine replaces it in continuity. On the other hand, in the HIT model, the small intestinal grafts are rendered dysfunctional without alimentary tract continuity. Histological evidence showed that acute rejection appeared earlier in HIT as compared to OIT. Hyperplasia and hypertrophy of the muscularis externa produced in the chronic rejection process were more pronounced in HIT allografts. The HIT grafts showed severe mucosal atrophy due to the lack of intraluminal trophic factors, because oral feedings can stimulate tropic hormones for mucosal growth, and provide nutrients for enterocytes. Intestinal permeability was consistently higher after HIT than after OIT. The HIT grafts demonstrated less contractility and less response to chemical stimulation than did OIT grafts. The OIT models are advantageous in studies of intraluminal nutrients, and intestinal secretions in these models might modulate the intestinal immune status and possibly delay rejection. The superior intestinal barrier function and the delayed onset of rejection in OIT rats suggest that nutrients and other factors in the succus entericus are important for the maintenance of intestinal graft function.

Animals↗

PubMed1999

Modeling modeling.

Models are tools; they need to fit both the hand and the task. Presence or absence of a feature such as a pacemaker or a cascade is not in itself good. Or bad. Criteria for model evaluation involve benefit-cost ratios, with the numerator a function of the range of phenomena explained, goodness of fit, consistency with other nearby models, and intangibles such as beauty. The denominator is a function of complexity, the number of phenomena that must be ignored, and the effort necessary to incorporate the model into one's parlance. Neither part of the ratio can yet be evaluated for MTS, whose authors provide some cogent challenges to SET.

Animals↗

PubMed2006

One-dimensional GIS-based model compared with a two-dimensional model in urban floods simulation.

A GIS-based one-dimensional flood simulation model is presented and applied to the centre of the city of Nîmes (Gard, France), for mapping flow depths or velocities in the streets network. The geometry of the one-dimensional elements is derived from the Digital Elevation Model (DEM). The flow is routed from one element to the next using the kinematic wave approximation. At the crossroads, the flows in the downstream branches are computed using a conceptual scheme. This scheme was previously designed to fit Y-shaped pipes junctions, and has been modified here to fit X-shaped crossroads. The results were compared with the results of a two-dimensional hydrodynamic model based on the full shallow water equations. The comparison shows that good agreements can be found in the steepest streets of the study zone, but differences may be important in the other streets. Some reasons that can explain the differences between the two models are given and some research possibilities are proposed.

Cities↗

PubMed1997

Model of complications of NIDDM. I. Model construction and assumptions.

OBJECTIVE: To develop a model of NIDDM for analyzing prevention strategies for NIDDM. RESEARCH DESIGN AND METHODS: A Markov type model with Monte Carlo techniques was used. Age, sex, and ethnicity of cohort was based on U.S. data. Incidence rates of complications were also based on community and population studies. RESULTS: Nonproliferative retinopathy, proliferative retinopathy, and macular edema are predicted in 79, 19, and 52%, respectively, of people with NIDDM; 19% are predicted to develop legal blindness. Microalbuminuria, gross proteinuria, and end-stage renal disease related to diabetes are predicted in 53, 40, and 17%, respectively. Symptomatic sensorimotor neuropathy and lower-extremity amputation are predicted in 31 and 17%, respectively. Cardiovascular disease is predicted in 39%. Higher rates of complications (1.1-3.0x) are predicted in minority populations. Predicted average life expectancy is 17 years after diagnosis. CONCLUSIONS: A probabilistic model of NIDDM predicts the vascular complications of NIDDM in a cohort representative of the incident cases of diabetes in the U.S. before age 75 years. Predictions of complications and mortality are consistent with the known epidemiology of NIDDM. The model is suitable for evaluating the effect of preventive interventions on the natural history of NIDDM.

Adult↗

PubMed1991

Computer simulation model of swine production systems: II. Modeling body composition and weight of female pigs, fetal development, milk production, and growth of suckling pigs.

Theoretical concepts and relationships used to develop a deterministic computer simulation model of female pigs during their reproductive life are described. The model predicts, in a continuous form, body composition and weight of female pigs, fetal development, sow milk yield, and growth of suckling pigs according to genotype, diet, and management conditions. The model simulates growth of adult female pigs. Dietary nutrients are used first for maintenance and second for fetal growth or milk production. Any surplus is retained in the body. Energy and protein body reserves are mobilized when a nutrient deficit occurs during gestation or lactation. However, the rates of body protein and fat accretion as well as the fat/protein ratio are limited by boundaries, the values of which depend on the nutritional and physiological status of the pig. The model's ability to simulate sow body weight changes and composition, fetal growth, milk production, and suckling pig's growth is illustrated.

Animals↗

PubMed1993

LIGHT model: an effective intervention model to change high-risk AIDS behaviors among hard-to-reach urban drug users.

Two thousand thirty-three hospital emergency room (ER) patients who were current, active injecting drug users (IDUs) were voluntary participants in a pretest, posttest research project which utilized a nursing model, the Personalized Nursing LIGHT Model, as a counseling approach to decrease high-risk AIDS behaviors. The LIGHT Model works by directly improving well-being and thereby indirectly decreasing high-risk behaviors associated with AIDS. Addicts from an urban ER in each of three cities (Detroit, Michigan; Brooklyn, New York; and Baltimore, Maryland) were treated with teams consisting of nurses and indigenous outreach workers. Posttest data were gathered on 995 of the clients who received the Personalized Nursing LIGHT Model teaching and counseling intervention. In a posttest at least 3 months after the initial interview, these IDUs reported a significant increase in well-being, t(530) = -11.77; p < .001, and significant reductions in frequency of IV heroin use, z = -18.4; p < .001, IV cocaine use, z = -16.0; p < .001, and IV speedball use, z = -14.3; p < .001, as well as significant decreases in sharing of cookers (a type of drug-using equipment), z = -13.8; p < .001, and other high-risk behaviors associated with AIDS acquisition and transmission. At a second posttest, at least 6 months after the initial interview, these results were unchanged.

Acquired Immunodeficiency Syndrome↗

PubMed1995

Kinetic modelling of in vitro lipid peroxidation experiments--'low level' validation of a model of in vivo lipid peroxidation.

Kinetic modelling overcomes some of the drawbacks of purely intuitive thinking in integrating information accumulated on chemical reactions involved in oxidative stress. However, it is important to assess if current knowledge about the reactions that mediate lipid peroxidation already allows satisfactory modelling of this process in near-to-physiological conditions. In this paper, a set of increasingly complex in vitro experiments on antioxidants (alpha-tocopherol and ascorbate) and lipid peroxidation in heterogeneous systems is simulated. Quantitative to semiquantitative agreement is found between experimental and simulation results. In addition, this theoretical analysis provided useful insights, suggested new hypotheses and experiments and pointed out relevant aspects needing further research. The results encourage and serve as partial validation for the formulation of relatively detailed mathematical models of in vivo lipid peroxidation. Some important aspects of the formulation and analysis of such models are discussed.

Antioxidants↗

PubMed2006

Modeling of lactose crystallization and color changes in model infant foods.

Lactose crystallization and color changes in formulas containing beta-lactoglobulin and gelatinized starch were investigated. Model infant formulas were prepared by colyophilization of 3 components (lactose, beta-lactoglobulin, and gelatinized starch). A mixture design was used to choose the percentage of each mixture component. These formulas were stored for 3 mo at different relative humidities (RH), ranging from approximately 0 to 94.6%, to study the lactose crystallization and color changes. Crystallization kinetics was studied by gravimetric methods, and lactose state (crystalline vs. amorphous) was verified before and after storage by differential scanning calorimetry. Before storage, lyophilized lactose was amorphous, but during storage it crystallized, depending on the RH. The lactose crystallization RH depended on the quantity of beta-lactoglobulin and gelatinized starch, and by increasing these quantities, the crystallization RH increased. For some formulas, the crystallization RH was noted at 3 different RH during storage. The first was noted after 1 d of storage and the second and third were observed later on, showing that crystallization is a time-dependent phenomenon. Nonenzymatic browning was studied in model infant formulas by yellow color changes of samples at 11.3, 43.2, 54.5, and 75.4% RH. In this study, 7 mathematical models were proposed to predict the moisture sorption properties and color changes at different RH, and the models were validated by experimental results.

Adsorption↗

PubMed1996

[A study on the mechanism of anxiety reduction through training: a comparison and examination of the stress-model and the distraction-model].

This study was carried out on the basis of Wolpe's principle of reciprocal inhibition. The stress-model asserts that the essence of anxiety reduction is the shift from the ergotropic to the trophotropic state, while the distraction-model asserts that distraction is the essence of anxiety reduction. The present experiment brings light to the following points not clarified in previous studies: (1) the effects of training vary with the symptoms of clients suffering from generalized anxiety disorders. The anxiety reducing effects of relaxation training is higher among those who complain of emotional syndromes than in those who complain of behavioral syndromes; (2) in both generalized anxiety disorders and social phobias, the mechanism of anxiety reduction matches the distraction model more than the stress model; (3) the effects of anxiety reduction by relaxation training and stress-relieving training carried out in the counseling room or in the client's home is higher in cases of generalized anxiety disorders than in social phobias.

Adolescent↗