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Results for “Structural validation”

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PubMed1985

[Criterion-oriented measurement in clinical psychology: development of a test on stress management].

Criterion-oriented tests evaluate the performance of the individual in relation to a given criterion which describes abilities and skills (intended competencies). The measuring process decides statistically if the person is "mastering" the criterion or not. The intended competencies should be represented by test items of high content-validity. The structure and application of this method especially to diagnostical issues of clinical psychology and therapeutic control are discussed. Steps are described construing a criterion-oriented test of stress and coping processes related to depressive and fearful behavior. The test is based on a situation-action-model in the theoretical framework of "stress and coping", "self-efficacy", "control" and "learned helplessness". Method and construction of items are shown in order to find some dimensions of coping-behavior-in-situations (appraisals, person-directed and environment-directed actions) and its sequential organisation in stressful episodes.

Adaptation, Psychological↗
PubMed1984

Estimation of individually adapted control parameters for an artificial beta cell.

For optimum long-term glycemic regulation using a miniaturized artificial beta cell it is indispensible to estimate control parameters suited to the individual requirements of each diabetic patient. To solve this problem, a strategy has been developed which is based on engineering optimum-control theory with a model involving glucose and insulin interactions. The model considers physiologically relevant unit processes like endogenous glucose production, insulin-independent glucose uptake from its apparent distribution space, insulin-dependent glucose utilization, glucose-dependent insulin supply, and insulin catabolism. The assumed model structure is validated by results obtained in experimentally diabetic dogs using partition analysis. The individual parameter values of the model are obtained by a digital computer procedure based on a simple test which involves a bolus injection of glucose + insulin when a constant basal insulin dose is being administered in the diabetic in whom normoglycemia was re-established before the test. The method presented is recommended for future use in all cases where an optimized insulin regimen is to be worked out.

Animals↗
PubMed1984

[Noninvasive monitoring with echocardiography. I. Ventricular function following thiopental and positive pressure breathing].

Using continuous M-mode echocardiography for measuring diameters of the left ventricle and calculating variables of left ventricular contractility during induction of anaesthesia the hemodynamic effects of thiopentone and of positive end-expiratory pressure breathing (PEEP) have been noninvasively assessed in 22 patients undergoing minor surgery (series A, n = 4 + 6, thiopentone) or cholecystectomy (series B, n = 12, PEEP). 4 mg X kg-1 i.v. (group I, n = 4) and 2 X 4 mg X kg-1, the second dose injected i.v. 5 min later (group II, n = 6), led in group I to a short lasting and in group II to a prolonged (duration of each experiment 10 min) significant decrease of the ejection fraction (EF), the shortening fraction (FS) and the mean velocity of circumferential fiber shortening (VCF mean). Thus the well known negative inotropic effect of thiopentone has been proven once more this time by noninvasive echocardiography. The influence of PEEP 5 and 10 cm H2O was evaluated in two ways: 1) by finding the incidence and extent of diminishing the "echocardiographic window" due to overexpansion of the lung during PEEP, rendering the sonographic visualization of the cardiac structures less valid, and 2) by assessing potential haemodynamic effects of PEEP. The curves of 3 in 12 cases (25%) have not been able to be evaluated properly because of "window closing"; in the residual 9 patients during PEEP 10 a significant decrease of the above mentioned parameters of contractility in comparison to PEEP 0 has been observed. IPPB without PEEP apparently does not disturb echocardiographic visualization.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

[An analysis of the quality of life of rehabilitated patients].

The improvement of the survival of cardiac patients may cause an impairment of their quality of life. At present, the study of the quality of life of the patients and its changes, must be considered as one of the aims of the Medicine. This study must be comprised clinical, functional, intellectual, social, and labor aspects, and all the items related to the environment of the patient. The first questionnaires used for the study of quality of life were generic but later on, specific questionnaires for different pathologies were found to be preferential. At present, there are questionnaires for hypertensive, myocardial infarction, angina and heart failure patients, and among them the questionnaire for myocardial infarction patients, structures and validated by the authors which has been used to study the quality of life postinfarction patients who followed a cardiac rehabilitation programme.

Humans↗
PubMedDate not supplied

Juvenile chronic arthritis: a biobehavioral disease. Some unsolved questions.

This review presents a multidimensional biopsychosocial model suitable for evaluating medical and psychosocial empirical findings in juvenile chronic arthritis (JCA). The possible predisposing, provoking and modifying variables that have been assessed in studies of JCA are presented, together with suggestions for further research. The model is appropriate for structuring and validating data in future longitudinal studies and may also serve as a frame of reference for a multi-professional team approach in the care of rheumatic children and their families.

Adolescent↗
PubMedDate not supplied

Elderly patients' satisfaction with hospital care.

OBJECTIVES: The aim of this study was to assess patient satisfaction with the geriatric services of a district general hospital and to examine whether there was a difference in satisfaction between patients in hospital and those who had been recently discharged. METHODS: A structured and validated patient satisfaction questionnaire was administered before discharge to hospitalised patients with a mental test score of 8 or more. It was also administered to a group of patients in the community who had been discharged from hospital not more than 72 hours earlier. The questionnaire was designed to assess seven separate areas, and contained 51 statements with which patients were asked to agree or disagree. Statistical analysis was by the Mann-Whitney U test and p < 0.05 was taken as significant. A total of 134 elderly patients (> 72 years) were surveyed over a four-month period. RESULTS: Satisfaction with the hospital geriatric service was high in both groups of patients. However, patient satisfaction differed between the two groups in three areas: interpersonal aspects; access, availability and convenience of the health services; and financial aspects.

Aged↗
PubMed2005

The multidimensional nature of ageism: construct validity and group differences.

The authors investigated the factor structure and construct validity of the Fraboni Scale of Ageism and the age and gender differences in ageism scores. Confirmatory factor analyses supported the multidimensional nature of FSA scores and generally corroborated the initial factor structure reported by M. Fraboni, with some notable exceptions. Essentially, the present findings were aligned with theoretical models of ageism that emphasize both cognitive facets and affective facets. That is, on the basis of their factor analytic findings, the authors redefined Fraboni's original factors of Antilocution, Avoidance, and Discrimination as Stereotypes, Separation, and Affective Attitudes, respectively, because of the clustering of items within factors. The revised 3-factor structure accounted for 36.4% of the variance in FSA scores. FSA factor scores significantly related to other scores from other measures of age-related attitudes, with higher correlations among factors that were similar in terms of their cognitive nature versus their affective nature. Finally, younger individuals and men had significantly higher ageism scores on the FSA than older individuals and women. The authors discussed the importance of adequately assessing ageism, with particular emphasis devoted to the understanding of age bias.

Adolescent↗
PubMedDate not supplied

Boiling points of halogenated aliphatic compounds: a quantitative structure-property relationship for prediction and validation.

Halogenated aliphatic compounds have many technical uses, but substances within this group are also ubiquitous environmental pollutants that can affect the ozone layer and contribute to global warming. The establishment of quantitative structure-property relationships is of interest not only to fill in gaps in the available database but also to validate experimental data already acquired. The three-dimensional structures of 240 compounds were modeled with molecular mechanics prior to the generation of empirical descriptors. Two bilinear projection methods, principal component analysis (PCA) and partial-least-squares regression (PLSR), were used to identify outliers. PLSR was subsequently used to build a multivariate calibration model by extracting the latent variables that describe most of the covariation between the molecular structure and the boiling point. Boiling points were also estimated with an extension of the group contribution method of Stein and Brown.

Journal Article↗
PubMed2000

Novel inhibitors of DNA gyrase: 3D structure based biased needle screening, hit validation by biophysical methods, and 3D guided optimization. A promising alternative to random screening.

Random screening provided no suitable lead structures in a search for novel inhibitors of the bacterial enzyme DNA gyrase. Therefore, an alternative approach had to be developed. Relying on the detailed 3D structural information of the targeted ATP binding site, our approach combines as key techniques (1) an in silico screening for potential low molecular weight inhibitors, (2) a biased high throughput DNA gyrase screen, (3) validation of the screening hits by biophysical methods, and (4) a 3D guided optimization process. When the in silico screening was performed, the initial data set containing 350 000 compounds could be reduced to 3000 molecules. Testing these 3000 selected compounds in the DNA gyrase assay provided 150 hits clustered in 14 classes. Seven classes could be validated as true, novel DNA gyrase inhibitors that act by binding to the ATP binding site located on subunit B: phenols, 2-amino-triazines, 4-amino-pyrimidines, 2-amino-pyrimidines, pyrrolopyrimidines, indazoles, and 2-hydroxymethyl-indoles. The 3D guided optimization provided highly potent DNA gyrase inhibitors, e. g., the 3,4-disubstituted indazole 23 being a 10 times more potent DNA gyrase inhibitor than novobiocin (3).

Anti-Infective Agents↗
PubMed2005

Vacuolar degradation of rat liver CYP2B1 in Saccharomyces cerevisiae: further validation of the yeast model and structural implications for the degradation of mammalian endoplasmic reticulum P450 proteins.

Mammalian hepatic cytochromes P450 (P450s) are endoplasmic reticulum (ER)-anchored hemoproteins with highly variable half-lives. CYP3A4, the dominant human liver drug-metabolizing enzyme, and its rat liver orthologs undergo ubiquitin (Ub)-dependent 26S proteasomal degradation after suicide inactivation or after heterologous expression in Saccharomyces cerevisiae. In contrast, rat liver CYP2C11 is degraded by the vacuolar "lysosomal" pathway when similarly expressed in yeast. The structural determinants that commit P450s to proteasomal or lysosomal degradation are unknown. To further validate S. cerevisiae as a model for exploring mammalian P450 turnover, the degradation of phenobarbital-inducible liver CYP2B1, an enzyme reportedly degraded via the rat hepatic autophagic-lysosomal pathway, was examined in a yeast strain (pep4delta) deficient in vacuolar degradation and its isogenic wild-type control (PEP4). Although CYP2B1 was equivalently expressed in both strains during early logarithmic growth, its degradation was retarded in pep4delta strain, remaining at a level 5-fold higher than that in PEP4 yeast when monitored at the stationary phase. No comparable CYP2B1 stabilization was detected in yeast genetically deficient in the ER Ub-conjugating enzyme Ubc6p or Ubc7p or defective in 19S proteasomal subunit Hrd2p. Thus, as in the rat liver, CYP2B1 is a target of vacuolar/lysosomal rather than proteasomal degradation in yeast, thereby further validating this model for mammalian P450 turnover. It is intriguing that a chimeric protein, CYP2B1-3A4CT, with the CYP3A4 C-terminal heptapeptide grafted onto the CYP2B1 C terminus, was proteasomally degraded after similar expression. Such diversion of CYP2B1 from its predominantly vacuolar degradation suggests that the CYP3A4 heptapeptide could either actively signal its proteasomal degradation or block its vacuolar proteolysis.

Amino Acid Sequence↗
PubMed2006

Can concept sorting provide a reliable, valid and sensitive measure of medical knowledge structure?

CONTEXT: Evolution from novice to expert is associated with the development of expert-type knowledge structure. The objectives of this study were to examine reliability and validity of concept sorting (ConSort) as a measure of static knowledge structure and to determine the relationship between concepts in static knowledge structure and concepts used during diagnostic reasoning. METHOD: ConSort was used to identify static knowledge concepts and analysis of think-aloud protocols was used to identify dynamic knowledge concepts (used during diagnostic reasoning). Intra- and inter-rater reliability, and correlation across cases, were evaluated. Construct validity was evaluated by comparing proportions of nephrologists and students with expert-type knowledge structure. Sensitivity and specificity of static knowledge concepts as a predictor of dynamic knowledge concepts were estimated. RESULTS: Thirteen first-year medical students and 19 nephrologists participated. Intra- and inter-rater agreement for determination of static knowledge concepts were 1.0 and 0.90, respectively. Reliability across cases was 0.45. The proportions of nephrologists and students identified as having expert-type knowledge structure were 82.9% and 55.8%, respectively (p=0.001). Sensitivity and specificity of ConSort((c)) in predicting concepts that were used during diagnostic reasoning were 96.8% and 27.8% for nephrologists and 87.2% and 55.1% for students. CONCLUSIONS: ConSort is a reliable, valid and sensitive tool for studying static knowledge structure. The applicability of tools that evaluate static knowledge structure should be explored as an addition to existing tools that evaluate dynamic tasks such as diagnostic reasoning.

Alberta↗
PubMed2006

Correcting ligands, metabolites, and pathways.

BACKGROUND: A wide range of research areas in bioinformatics, molecular biology and medicinal chemistry require precise chemical structure information about molecules and reactions, e.g. drug design, ligand docking, metabolic network reconstruction, and systems biology. Most available databases, however, treat chemical structures more as illustrations than as a datafield in its own right. Lack of chemical accuracy impedes progress in the areas mentioned above. We present a database of metabolites called BioMeta that augments the existing pathway databases by explicitly assessing the validity, correctness, and completeness of chemical structure and reaction information. DESCRIPTION: The main bulk of the data in BioMeta were obtained from the KEGG Ligand database. We developed a tool for chemical structure validation which assesses the chemical validity and stereochemical completeness of a molecule description. The validation tool was used to examine the compounds in BioMeta, showing that a relatively small number of compounds had an incorrect constitution (connectivity only, not considering stereochemistry) and that a considerable number (about one third) had incomplete or even incorrect stereochemistry. We made a large effort to correct the errors and to complete the structural descriptions. A total of 1468 structures were corrected and/or completed. We also established the reaction balance of the reactions in BioMeta and corrected 55% of the unbalanced (stoichiometrically incorrect) reactions in an automatic procedure. The BioMeta database was implemented in PostgreSQL and provided with a web-based interface. CONCLUSION: We demonstrate that the validation of metabolite structures and reactions is a feasible and worthwhile undertaking, and that the validation results can be used to trigger corrections and improvements to BioMeta, our metabolite database. BioMeta provides some tools for rational drug design, reaction searches, and visualization. It is freely available at http://www.cmbi.ru.nl/biometa/ provided that the copyright notice of all original data is cited. The database will be useful for querying and browsing biochemical pathways, and to obtain reference information for identifying compounds. However, these applications require that the underlying data be correct, and that is the focus of BioMeta.

Computational Biology↗
PubMed1994

Evaluating and validating two methods for estimating brain structure volumes: tessellation and simple pixel counting.

Developments in imaging technology have made three-dimensional visualization of internal brain structures possible with excellent resolution. Since improved visualization implies improved measurement, these advances hold promise to more accurately measure the volumes of internal structures. As new technologies and techniques emerge, evaluating the relative benefits of measurement methods becomes necessary. We compared and evaluated two methods of estimating volumes from images of brain structures. One method counted pixels within a region of interest, while the other method tessellated the surface between tracings on adjacent slices. Our study assessed both measurement error for true phantom volumes and method disparity for in vivo structures in a randomly selected sample of subjects (n = 100). For our comparisons, we focused on the temporal lobe, ventricular system, and hippocampus. Bias, independence of measurement errors and maximal discrimination of individual differences are properties that are relevant to validating and evaluating measurements of cerebral structure. Pixel counting proved to be the more robust of the two methods, being less sensitive to nuisance-interactions between size of object, shape, and slice thickness. Clinical and research applications of imaging techniques may have distinctive but overlapping needs when evaluating and validating new developments in imaging.

Adult↗
PubMed2000

Experimental validations of the HELS method for reconstructing acoustic radiation from a complex vibrating structure

This paper presents experimental validations of the Helmholtz Equation Least Squares (HELS) method [Wang and Wu, J. Acoust. Soc. Am. 102, 2020-2032 (1997); Wu and Wang, U.S. Patent Number 5712805 (1998); Wu, J. Acoust. Soc. Am. 107, 2511-2522 (2000)] on reconstruction of the radiated acoustic pressures from a complex vibrating structure. The structure under consideration has geometry and dimensions similar to those of a real passenger vehicle front end. To simulate noise radiation from a vehicle, a high fidelity loudspeaker installed inside the structure at the location of the engine is employed to generate both random and harmonic acoustic excitations. The radiated acoustic pressures are measured over a finite planar surface above the structure by a microphone. The measured data are taken as input to the HELS formulation to reconstruct the acoustic pressures on the top surface of the structure as well as in the field. The reconstructed acoustic pressures are then compared with measured ones at the same locations. Also shown are comparisons of the reconstructed and measured acoustic pressure spectra at various locations on the surface. Results show that satisfactory reconstruction can be obtained on the top surface of the structure subject to both random and harmonic excitations. Moreover, the more measurements and the closer their distances to the source surface, the more accurate the reconstruction. The efficiency of the HELS method may decrease with increasing of the excitation frequency. This high frequency difficulty is inherent in all expansion theories.

Journal Article↗
PubMed1998

Validation tools: can they indicate the information content of macromolecular crystal structures?

The explosive increase in the number of published three-dimensionsal structures of macromolecules determined by X-ray analysis places a responsibility on experimentalists, referees and curators of databases to ensure correspondence between the structure parameters and data. Validation tools will evolve as more appropriate statistical techniques and new information, such as that from proteins analysed at atomic resolution, becomes available.

Crystallography↗
PubMed2003

Screening of high production volume chemicals for estrogen receptor binding activity (II) by the MultiCASE expert system.

A structurally and functionally diverse and cross-validated quantitative structure-activity knowledge database generated by the MultiCASE expert system was used to screen 2526 high production volume chemicals (HPVCs) for their estrogen receptor binding activity. 73 HPVCs were found to contain structural features or biophores that have been documented as having the ability to bind to the estrogen receptor. Potential chemicals were ranked according to their quantitatively predicted ER binding potential and the details of the biophores found in them are discussed.

Animals↗
PubMed1997

Inclusion of conserved buried water molecules in the model structure of rat submaxillary kallikrein.

A new approach to the molecular modelling of homologous serine proteases is adopted, by including a set of 21 buried waters known to be preserved in enzymes sharing the primary specificity of trypsin, in the homology modelling of rat submaxillary gland kallikrein. Buried waters--water molecules sequestered from bulk solvent within a protein matrix--appear to be integral conserved components of all serine proteases of known structure and should be incorporated into serine protease models built on the basis of sequence/structural homology to this family. The absence of such waters might induce errors in a force field simulation, favouring the formation of nonexistent hydrogen bonds and locally inaccurate structure. The kallikrein model refinement has led to the conclusion that an additional buried water should be added to the original rigid matrix of 21 conserved water molecules. The structurally preserved protein cavities of such waters validate the modelled structure.

Amino Acid Sequence↗