SEARCH · PubMed Health

Results for “Model”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 919 records · Page 51Linked to original sources

PubMedDate not supplied

Advanced practice nursing model for comprehensive care with chronic illness: model for promoting process engagement.

New models of providing care to chronically ill persons are needed that can facilitate a more integrative approach to patient care. The purposes of this article are to describe the utilization of a theory synthesis process for development of a client-focused approach for advanced practice nurse (APN) management of chronic illness and to present the Model for Promoting Process Engagement. The model was developed as a theory-driven intervention to address complexities of chronic illness care. This APN practice model is the direct result of the synthesis of a number of differing theoretical models developed by the authors in previous individual research endeavors.

Caregivers↗

PubMed2004

Modeling of the sagittal cervical spine as a method to discriminate hypolordosis: results of elliptical and circular modeling in 72 asymptomatic subjects, 52 acute neck pain subjects, and 70 chronic neck pain subjects.

STUDY DESIGN: Computer analysis of digitized vertebral body corners on lateral cervical radiographs. OBJECTIVES: Using elliptical and circular modeling, the geometric shape of the path of the posterior bodies of C2-C7 was sought in normal, acute pain, and chronic pain subjects. To determine the least squares error per point for paths of geometric shapes, minor axis to major axis elliptical ratios (b/a), Cobb angles, sagittal balance of C2 above C7, and posterior tangent segmental and global angles. SUMMARY OF BACKGROUND DATA: When restricted to cervical lordotic configurations, normal, acute pain, and chronic pain subjects have not been compared for similarities or differences of these parameters. Conventional Cobb angles provide only a comparison of the endplates of the distal vertebrae, while geometric modeling provides the shape of the entire sagittal curves, the orientation of the spine, and segmental angles. METHODS: Radiographs of 72 normal subjects, 52 acute neck pain subjects, and 70 chronic neck pain subjects were digitized. For normal subjects, the inclusion criteria were no kyphotic cervical segments, no cranial-cervical symptoms, and less than +/- 10 mm horizontal displacement of C2 above C7. In pain subjects, inclusion criteria were no kyphotic cervical segments and less than 25 mm of horizontal displacement of C2 above C7. Measurements included segmental angles, global angles of lordosis (C1-C7 and C2-C7), height-to-length ratios, anterior weight bearing, and from modeling, circular center, and radius of curvature. RESULTS: In the normal group, a family of ellipses was found to closely approximate the posterior body margins of C2-C7 with a least squares error of less than 1 mm per vertebral body point. The only ellipse/circle found to include T1, with a least squares error of less than 1 mm, was a circle. Compared with the normal group, the pain group's mean radiographic angles were reduced and the radius of curvature was larger. For normal, acute, and chronic pain groups, the mean angles between posterior tangents on C2-C7 were 34.5 degrees, 28.6 degrees, and 22.0 degrees, C2-C7 Cobb angles were 26.8 degrees, 16.5 degrees, and 12.7 degrees, and radius of curvature were r = 132.8 mm, r = 179 mm, and r = 245.4 mm, respectively. CONCLUSIONS: The mean cervical lordosis for all groups could be closely modeled with a circle. Pain groups had hypolordosis and larger radiuses of curvature compared with the normal group. Circular modeling may be a valuable tool in the discrimination between normal lordosis and hypolordosis in normal and pain subjects.

Acute Disease↗

PubMed2006

Using protein homology models for structure-based studies: approaches to model refinement.

Homology modeling is a computational methodology to assign a 3-D structure to a target protein when experimental data are not available. The methodology uses another protein with a known structure that shares some sequence identity with the target as a template. The crudest approach is to thread the target protein backbone atoms over the backbone atoms of the template protein, but necessary refinement methods are needed to produce realistic models. In this mini-review anchored within the scope of drug design, we show the validity of using homology models of proteins in the discovery of binders for potential therapeutic targets. We also report several different approaches to homology model refinement, going from very simple to the most elaborate. Results show that refinement approaches are system dependent and that more elaborate methodologies do not always correlate with better performances from built homology models.

Computational Biology↗

PubMed2005

A health-care model of emotional labour: an evaluation of the literature and development of a model.

PURPOSE: This paper aims to evaluate the literature on emotional labour in the health-care sector and the benefits and costs of such performance for both the carer and the patient. The aim is to develop a new health care model of emotional labour that has implications for health-care management in terms of policy and education as well as for future research in this field. DESIGN/METHODOLOGY/APPROACH: A new model to explain the antecedents and consequences of emotional labour within a health-care setting is developed that builds on existing research. FINDINGS: The model distinguishes between types of emotional conflict to which emotional labour-inducing events in health-care settings might lead. The negative and positive consequences, specific to health-care settings, of emotional labour performance are also outlined. PRACTICAL IMPLICATIONS: Emotional labour should be formally recognised as a key skill in facilitating the patient journey, with emotional skills being taught in innovative ways outside the formal classroom setting. Health-care professionals should be offered training on coping with the effects of emotional labour performance. Finally, more research should be carried out to further develop the model, particularly in identifying causes of emotional labour within health-care settings and in differentiating the effects that different kinds of emotional labour performance might have. ORIGINALITY/VALUE: The paper draws together previous research on emotional labour within health-care settings to develop a coherent model that can be used to guide future research and practice.

Health Personnel↗

PubMedDate not supplied

Children's and adults' models for predicting teleological action: the development of a biology-based model.

Understanding that only living things must act to gain self-beneficial goals is important for developing a theory-like understanding of the living world. This research studied the models that preschoolers, fifth graders, and adults use to guide their predictions of self-beneficial, goal-directed (i.e., teleological) action. Four possible models have been suggested: finalist, complexity based, biology based, and animal based. In Study 1, participants (N = 104) were assigned to one of two conditions that differed in whether a beneficial or neutral object was pictured; they were asked to predict whether animals, plants, machines, and simple artifacts would modify their movement in the direction of that object. Preschoolers' predictions were consistent with an animal-based model, fifth graders' predictions were consistent with biology-based and complexity-based models, and adults' predictions were consistent with a biology-based model. Analysis of both individual response patterns and explanations supported these findings, but also showed that a significant number of preschoolers and fifth graders were finalist, and that very few individual fifth graders followed a complexity-based teleology. In Study 2, participants (N = 84) reported whether the animals, plants, machines, and simple artifacts in Study 1 had psychological capacities. All age groups attributed psychological capacities to animals at levels higher than other domains and at above-chance levels. The evidence from these two studies suggests that preschoolers, unlike fifth graders and adults, predict teleological action for plants and animals on the basis of these entities' inferred psychological capacities.

Adult↗

PubMed1994

The inflammatory and proliferative response of normal skin in a model for acute chemical injury: ornithine decarboxylase induction as a common feature in various models for acute skin injury.

Application of sodium dodecyl sulphate (SDS) on the skin of healthy volunteers was used as a model for acute chemical injury. The time course of the response with respect to cell proliferation was studied using ornithine decarboxylase (ODC) activity. Erythema, polymorphonuclear leucocyte (PMN) infiltration, and the induction of epidermal antiproteinase activity (SKALP/elafin) were used as markers for the inflammatory response. ODC induction was similar to that in other models of acute skin injury, such as tape-stripping and ultraviolet light radiation. The amount of PMN infiltration correlated with erythema, but not with ODC induction. In contrast with findings in the tape-stripping model, no induction of SKALP/elafin activity was found after SDS application. We conclude that cell proliferation as measured by ODC induction is a common feature in the various models for skin injury. Both the kinetics and the intensity of the inflammatory response, and the induction of epidermal antiproteinase activity, appear to vary, depending on the specific model.

Acute Disease↗

PubMed2005

Evidence against a maximum response model of exogenous visual orienting during early infancy and support for a dimensional switching model.

Very young infants orient overtly with eye and head movements to salient events in their visual environments, but those events rarely occur in the absence of competing visual stimuli. Two different models of how this kind of orienting is related to number and distribution of elements in the stimulus field were tested with infants across the age range from 2 to 5 months in four experiments. A set size manipulation in Experiments 1-3 produced data that were mostly inconsistent with the Maximum Response model proposed by Dannemiller (1998), especially at ages over 3 months. Experiment 4 produced data from 3.5-month-olds that were consistent with an alternative Dimensional Switching model that assumed that there was switching across trials in the stimulus dimension that drove orienting. This Dimensional Switching model can explain the small to nonexistent set size effects observed in the first three experiments as well as data from previous experiments using this paradigm. Factors that could produce this kind of dimensional switching over time were considered and other implications of this model for understanding the development of overt visual orienting were discussed.

Age Factors↗

PubMed1984

A two-susceptibility-allele model for genetic diseases and associated marker loci: differences and similarities to a one-s-allele model.

A model for genetic diseases and associated markers is defined where two distinct susceptibility alleles are possible, each associated with a different marker allele. Marker genotype distributions in a disease population are then expressed in terms of haplotype frequencies and penetrance parameters. It is shown that, if the heterozygote with two different disease alleles has a higher penetrance than the two disease homogzygotes, the observed to 'Hardy-Weinberg-expected' ratio of associated marker genotypes (the alpha/beta ratio of Falk, Mendell & Rubinstein, 1983) will always be greater than or equal to one. When all disease penetrances are equal, the model becomes indistinguishable from a recessive one-s-allele model with alpha/beta = 1. Application of these observations to several data sets for insulin dependent diabetes mellitus suggests the possibility that different marker genotype distributions in different samples may be due to different penetrances of the disease genotypes in the samples. If a particular environment causes the heterozygote disease genotype (with two different disease alleles) to have the highest penetrance, the marker genotype distribution would be compatible with the 2-s-allele model. In other environments where the three disease genotypes have essentially equal penetrances, the marker distribution would be compatible with the 1-s-allele model.

Alleles↗

PubMed1993

Uncertainties in pharmacokinetic modeling for perchloroethylene: II. Comparison of model predictions with data for a variety of different parameters.

In this paper we compare expectations derived from 10 different human physiologically based pharmacokinetic models for perchloroethylene with data on absorption via inhalation, and concentrations in alveolar air and venous blood. Our most interesting finding is that essentially all of the models show a time pattern of departures of predictions of air and blood levels relative to experimental data that might be corrected by more sophisticated model structures incorporating either (a) heterogeneity of the fat compartment (with respect to either perfusion or partition coefficients or both) or (b) intertissue diffusion of perchloroethylene between the fat and muscle/VRG groups. Similar types of corrections have recently been proposed to reduce analogous anomalies in the fits of pharmacokinetic models to the data for several volatile anesthetics. A second finding is that models incorporating resting values for alveolar ventilation in the region of 5.4 L/min seemed to be most compatible with the most reliable set of perchloroethylene uptake data.

Biological Transport, Active↗

PubMed1997

Modeling of flow in a straight stented and nonstented side wall aneurysm model.

We investigated the changes of flow patterns in a blood vessel with a side wall aneurysm resulting from placement of a stent. Local hemodynamics can be markedly altered by placing an intravascular stent, which covers the orifice of the aneurysm. The alternations in flow patterns can lead to flow stasis in the aneurysmal pouch and promote the formation of a stable thrombus. Furthermore, a porous stent can serve as substrate for neointimal growth and subsequently induce a remodeling of the diseased arterial segment. To examine changes in local hemodynamics due to stent placement, a stented and nonstented aneurysm model was investigated computationally in a three-dimensional configuration using a finite element fluid dynamics program. The finite element model was studied under incompressible, pulsatile, viscous, Newtonian conditions. The fluid dynamic similarity parameter, i.e., the maximum/minimum Reynolds number, was set at about 240/25 based on cross-sectional average instantaneous flow. The Womersley number was set to 2.5. These values are representative of large cerebral arteries. The results of the stented versus the nonstented model show substantial difference sin flow patterns inside the aneurysmal pouch. Flow activity inside the stented aneurysm model is significantly diminished and flow inside the parent vessel is less undulated and is directed past the orifice. A high-pressure zone at the distal neck and the dome of the aneurysm prior to stenting decreases after stent placement. However, elevated pressure values are found at the stent filaments facing the current. Higher shear rates are observed at the distal aneurysmal neck after stenting, but are confined to a smaller region and are unidirectional compared to the nonstented model.

Aneurysm↗

PubMed1994

[Adaptation study for biofilm of the urinary tract via highly complicated bladder model (biofilm model of the urinary tract)--experimental study using automatic simulator of the urinary antimicrobial agent concentration].

With the view of making an adaptation study for biofilm of the urinary tract, we devised a computer-controlled highly complicated bladder model (biofilm model of the urinary tract) that allowed the simulation of time-course changes in the urinary concentration of antimicrobial agents. Clarithromycin (CAM), which is reported to have an anti-biofilm action, was examined at urinary levels approximating clinical concentrations and its effect on biofilm was determined. The following results were obtained. 1) Ofloxacin (OFLX, 200 mg x 2/day, MIC; 8 micrograms/ml), which is active against Pseudomonas aruginosa, caused apparent microbial elimination from the model at 42 hours, but bacterial regrowth occurred 4 hours after withdrawal of this agent. No disappearance of the biofilm was noted with OFLX suggesting that this was the cause of bacterial regrowth. 2) The combination of OFLX (200 mg x 2/day) and CAM (MIC; > 128 micrograms/ml, 200 mg x 2/day) on anti-biofilm agent, with no effect on P. aeruginosa, eliminated bacteria from the bladder model more rapidly and prolonged the regrowth time to 10 hours after withdrawal of the antimicrobial agents. Disappearance of most of the biofilm and only slight microbial adhesion was noted. 3) The combination of OFLX (200 mg x 2/day) and CAM (400 mg x 3/day) caused microbial elimination from the bladder model with no regrowth at 30 hours after withdrawal of the antimicrobial agents. The biofilm disappeared completely and no microbial adhesion was noted. 4) CAM alone (400 mg x 3/day) allowed microbial recovery to the initial level within 48 hours after withdrawal, but led to disappearance of the biofilm and the adhesion of microbes without a glycocalyx. 5) These results suggest that the anti-biofilm action of CAM is dose-dependent, and that combined use of an appropriate antimicrobial agent and anti-biofilm agent like CAM may be effective for biofilm infections of the urinary tract.

Anti-Bacterial Agents↗

PubMed2000

A virtual source model for Monte Carlo modeling of arbitrary intensity distributions.

A photon virtual source model was developed for simulating arbitrary, external beam, intensity distributions using the Monte Carlo method. The source model consists of a photon fluence grid composed of a matrix of square elements, located 25-cm downstream from the linear accelerator target. Each particle originating from the fluence map is characterized by the seven phase space parameters, position (x, y, z), direction (u, v, w), and energy. The map was reconstructed from fluence and energy spectra acquired by modeling components of the linear accelerator treatment head using the Monte Carlo code MCNP4B. The effect of contaminant electrons is accounted for by the use of a sub-source derived from a phase-space simulation of a 25-MV linac treatment head using the code BEAM. The BEAM sub-source was incorporated into the MCNP4B phase-space model and is sampled using a field-size dependent sampling ratio. A Gaussian blurring kernel is convolved with the photon fluence map to account for the finite focal spot size and scattering effects from structures such as the flattening filter and MLC leaves. Depth dose and profile source calculations for 6-MV and 25-MV photon beams, for 5 x 5 cm2, 10 x 10 cm2, and 15 x 15 cm2 field sizes, are in good agreement with measurement and are well within acceptability criteria suggested by the AAPM Task Group Report No. 53. Irregular field calculations compared with film measurement and with a 3-D pencil beam algorithm show that the source model is capable of accurately simulating arbitrary MLC fields.

Biophysical Phenomena↗

PubMed2004

Neuroprotective effects of a novel poly(ADP-ribose) polymerase-1 inhibitor, 2-[3-[4-(4-chlorophenyl)-1-piperazinyl] propyl]-4(3H)-quinazolinone (FR255595), in an in vitro model of cell death and in mouse 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine model of Parkinson's disease.

The massive activation of poly(ADP-ribose) polymerase-1 (PARP-1) by DNA-damaging stimuli, such as exposure to reactive oxygen species (ROS), can lead to cell injury via severe, irreversible depletion of the NAD and ATP pool, and PARP-1 inhibitors have been expected to rescue neurons from degeneration in a number of disease models. We have recently identified 2-[3-[4-(4-chlorophenyl)-1-piperazinyl] propyl]-4(3H)-quinazolinone (FR255595) as a novel and potent PARP-1 inhibitor through structure-based drug design and high-throughput screening. This compound potently inhibited PARP activity with an IC(50) value of 11 nM and was orally active and highly brain penetrable. Here, we show that prevention of PARP activation by FR255595 protects against both ROS-induced cells injury in vitro and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced nigrostriatal dopaminergic damage in an in vivo Parkinson's disease (PD) model. In cell death models in vitro, exposure of hydrogen peroxide induced cell death with PARP overactivation in PC12 cells and SH-SY5Y cells, and pre- and post-treatment with FR255595 (10(-9)-10(-5) M) significantly reduced PARP activation and cell death. In mouse MPTP model, MPTP (20 mg/kg i.p.) intoxication lead to PARP activation and cell damage in the nigrostriatal dopaminergic pathway, which was significantly ameliorated by oral administration of FR255595 (10-32 mg/kg), both in the substantia nigra and in the striatum via marked reduction of PARP activation, even with delayed treatment. These findings clearly indicate that the novel PARP-1 inhibitor FR255595 exerts neuroprotective effect through its potent PARP-1 inhibitory actions in PD model, suggesting that the drug could be an attractive candidate for several neurodegenerative disorders, including PD.

Animals↗

PubMed2000

Modeling the functional effects of allosteric modulators at pharmacological receptors: an extension of the two-state model of receptor activation.

Allosteric modulation is a mechanism for modifying pharmacological receptor activity that has largely been ignored in terms of therapeutic drug design, although benzodiazepine receptor ligands are an example of the serendipitous discovery of this class of compound. The current mathematical models of allosteric interactions at (particularly G-protein-coupled) receptors concentrate on the effects of the allosteric ligand on orthosteric ligand binding and ignore potential effects of these compounds on the ability of orthosteric ligands to cause receptor activation. In this report a mathematical model of allosteric interactions at pharmacological receptors has been investigated that explicitly includes effects of the allosteric ligand on receptor activation. This model uses the two-state model of receptor activation as its basis and is qualitatively consistent with currently reported behavior of allosteric modulators. The predictions of this model suggest a series of criteria that should be tested before the effects of an allosteric modulator can be quantified in a nonsystem-dependent manner. It has also been used to provide a potential mechanistic explanation for the functional effects of the A(1) adenosine receptor allosteric enhancer PD 81,723 and a recently reported allosteric modulator of type 1 metabotropic glutamate receptors.

Allosteric Regulation↗

PubMed1986

Two approaches to modeling kinetics of biodegradation by growing cells and application of a two-compartment model for mineralization kinetics in sewage.

The patterns of microbial mineralization of 0.3 to 30 ng of glucose, benzoate, and phenol per ml of sewage collected in late fall and winter were analyzed with the integrated Monod equation and a model in which growth of active organisms occurs at the expense of organic compounds other than the test substrate. Either model could be closely fit by nonlinear regression to the data from individual tests with one concentration of substrate added to one dilution of sewage. However, neither model accounted satisfactorily for differences in patterns of mineralization resulting from differences in substrate concentration and cell density between different tests. It is suggested that both the added substrates and other organics present in sewage contributed to the growth of the active organisms. The mineralization of glucose in sewage collected in summer was better described by a two-compartment model than by any other model tested.

Bacteria↗

PubMed1999

Visualization and modelling of the thermal inactivation of bacteria in a model food.

A large number of incidents of food poisoning have been linked to undercooked meat products. The use of mathematical modelling to describe heat transfer within foods, combined with data describing bacterial thermal inactivation, may prove useful in developing safer food products while minimizing thermal overprocessing. To examine this approach, cylindrical agar blocks containing immobilized bacteria (Salmonella typhimurium and Brochothrix thermosphacta) were used as a model system in this study. The agar cylinders were subjected to external conduction heating by immersion in a water bath. They were then incubated, sliced open, and examined by image analysis techniques for regions of no bacterial growth. A finite-difference scheme was used to model thermal conduction and the consequent bacterial inactivation. Bacterial inactivation rates were modelled with values for the time required to reduce bacterial number by 90% (D) and the temperature increase required to reduce D by 90% taken from the literature. Model simulation results agreed well with experimental results for both bacteria, demonstrating the utility of the technique.

Agar↗

PubMed2006

Development of a microbial model for the combined effect of temperature and pH on spoilage of ground meat, and validation of the model under dynamic temperature conditions.

The changes in microbial flora and sensory characteristics of fresh ground meat (beef and pork) with pH values ranging from 5.34 to 6.13 were monitored at different isothermal storage temperatures (0 to 20 degrees C) under aerobic conditions. At all conditions tested, pseudomonads were the predominant bacteria, followed by Brochothrix thermosphacta, while the other members of the microbial association (e.g., lactic acid bacteria and Enterobacteriaceae) remained at lower levels. The results from microbiological and sensory analysis showed that changes in pseudomonad populations followed closely sensory changes during storage and could be used as a good index for spoilage of aerobically stored ground meat. The kinetic parameters (maximum specific growth rate [mu(max)] and the duration of lag phase [lambda]) of the spoilage bacteria were modeled by using a modified Arrhenius equation for the combined effect of temperature and pH. Meat pH affected growth of all spoilage bacteria except that of lactic acid bacteria. The "adaptation work," characterized by the product of mu(max) and lambda(mu(max) x lambda) was found to be unaffected by temperature for all tested bacteria but was affected by pH for pseudomonads and B. thermosphacta. For the latter bacteria, a negative linear correlation between ln(mu(max) x lambda) and meat pH was observed. The developed models were further validated under dynamic temperature conditions using different fluctuating temperatures. Graphical comparison between predicted and observed growth and the examination of the relative errors of predictions showed that the model predicted satisfactorily growth under dynamic conditions. Predicted shelf life based on pseudomonads growth was slightly shorter than shelf life observed by sensory analysis with a mean difference of 13.1%. The present study provides a "ready-to-use," well-validated model for predicting spoilage of aerobically stored ground meat. The use of the model by the meat industry can lead to effective management systems for the optimization of meat quality.

Animals↗

PubMed2000

Lessons from genetically engineered animal models XI. Novel mouse models to study pathogenic mechanisms of Crohn's disease.

Crohn's Disease (CD) affects more than 500,000 individuals in the United States and represents the second most common chronic inflammatory disorder after rheumatoid arthritis. Although major advances have been made in defining the basic mechanisms underlying chronic intestinal inflammation, the precise etiopathogenesis of CD remains unknown. We have recently characterized two novel mouse models of enteritis that express a CD-like phenotype, namely the TNF DeltaARE model of tumor necrosis factor (TNF) overexpression and the SAMP1/Yit model of spontaneous ileitis. The unique feature of these models is that they closely resemble CD for location and histopathology. These genetically manipulated new models of intestinal inflammation offer a powerful tool to investigate potential causes of human disease and may allow the development of novel disease-modifying therapeutic modalities for the treatment of CD.

Animals↗