Search PubMed⌕ Search

Biomedical subjects

J Brender

Publications and source records attributed to J Brender.

31 records · Page 2Linked to original sources
PubMed1994

A methodology for evaluation of knowledge-based systems in medicine.

Evaluation is critical to the development and successful integration of knowledge-based systems into their application environment. This is of particular importance in the medical domain--not only for reasons of safety and correctness, but also to reinforce the users' confidence in these systems. In this paper we describe an iterative, four-phased development evaluation cycle covering the following areas: (i) early prototype development, (ii) validity of the system, (iii) functionality of the system, and (iv) impact of the system.

Artificial Intelligence↗
PubMed1993

Problem-oriented management of laboratory work through dynamic test scheduling.

This paper gives an overview of problems inherent in dynamic test scheduling together with some model solutions. Dynamic test schedules are decision tree-like protocols for cost-efficient management of analytical production in a clinical laboratory. The present analysis is based on previous practical experience and concludes that it is not feasible to introduce dynamic test scheduling on a large scale without computer-based support, because of the increase in complexity of the laboratory work processes. Further, our experience is that it is extremely complex to incorporate the dynamic test scheduling functionality into an existing Laboratory Information System (LIS). The approach pursued in the OpenLabs (A2028) AIM Project for implementing dynamic test scheduling is to provide the necessary functionality as a stand-alone module interconnected with a LIS in an open systems solution.

Clinical Laboratory Information Systems↗
PubMed1991

Factors influencing the transferability of medical decision support systems.

Transferability is a key issue in the development and implementation of medical decision support systems. Such systems have up to now tended to be confined to the development site. Transferability represents the integrated effect of several more basic attributes of Decision Support Systems. These attributes can be considered to belong to two main groups: those concerned with the Medical Domain (of the system) and those concerned with the Information Technology by which the System functions. Among the Domain issues the most important are: Epidemiology, Terminology and Methodology. Concerning the Information Technology issues the most important are: Knowledge Acquisition and Representation methods, Database design and integration with inference mechanism. The effect of each of the individual factors is considered by illustrations from the literature and by studying the results of recent experiments where databases and decision support systems from different countries are interchanged. This exercise allows some planning in the design of future systems with the aim of improving overall transferability and therefore applicability.

Artificial Intelligence↗
PubMed1990

Information enhancement in clinical decision making by controlled data generation.

The aim of this presentation is to present the principles in simultaneous data reduction and information enhancement through the regulation of data generation. This regulation of data generation, which has the purpose of relieving the problem of data pollution and information intoxication, is achieved through an integration of the clinical management of the patient problem with the paraclinical data production service. Thereby, the focus is on the initiation of new data rather than on interpretation of existing data.

Chemistry, Clinical↗
PubMed1987

A sensitive solid-phase immunosorbent assay for tissue-type plasminogen activator activity in plasma using trinitrobenzoylated poly-D-lysine as a stimulator for plasminogen activation.

A sensitive, specific and precise immunosorbent assay for tissue-type plasminogen activator (t-PA) activity in plasma was developed. It measured the single-chain and the two-chain forms of t-PA with equal sensitivity. The assay involved (I) coating of wells in microtiter plates with a monoclonal antibody directed towards an epitope on t-PA apart from the catalytic active site, (II) binding of t-PA to the solid-phase antibody, (III) activation of plasminogen by antibody-bound t-PA in the presence of a new potent stimulator, trinitrobenzyl alkylated poly-D-lysine (TNB-poly-D-lysine) and measurement of plasmin activity with D-Val-Leu-Lys-pNA. Plasma samples were acid-treated and diluted 80 times in order to minimize the inhibitory effect of plasma on the assays. The assay could be performed within one working day with precoated microtiter plates. The sensitivity of the assay for t-PA in plasma was 1 pM (approximately 70 ng/l). The recoveries of single-chain and two-chain t-PA added to plasma was 97-104%. The intraassay coefficient of variation was 3.4-5.1% and the interassay coefficient of variation was 7.8-18%. Resting values of t-PA in plasma for 42 healthy subjects ranged between 0 and 30 pM (median: 4.1 pM). The values after 10 min venous occlusion ranged between 1.2 and 520 pM (median: 100 pM). The t-PA concentrations determined by the immunosorbent assay correlated well with euglobulin clot lysis time measurements (r = 0.940).

Antibodies↗
PubMed1987

The incidence and risk of early postoperative small bowel obstruction. A cohort study.

Early postoperative small bowel obstruction is a rare (0.69 percent incidence) but serious postoperative complication with a relatively high mortality rate (17.8 percent). Operations performed below the transverse mesocolon impose an increased risk, whereas those limited to the upper abdomen are virtually free of risk. The clinical picture of a patient who initially manifests a return of gut function and advances to a diet, but then has loss of bowel function with distention and pain is most characteristic of early postoperative small bowel obstruction. Any patient in the high-risk group demonstrating this clinical picture should be presumed to have a mechanical small bowel obstruction, and early operation should be considered.

Abdomen↗
PubMed1986

Risk of postmenopausal hip fracture in Mexican American women.

To assess the risk of hip fracture in Mexican Americans, the ethnicity of 80 women aged 50 years and over admitted with hip fractures to a Texas hospital was compared with that of age-matched women hospitalized for other reasons. The risk of fracture for Mexican Americans was only 35 per cent that of Whites (95% CI = 19 per cent, 65 per cent). This finding was confirmed in a chart survey performed in a second hospital population. These results suggest that Mexican American women may receive less potential benefit from preventive measures for hip fracture than Whites.

Aged↗
PubMed1985

Zymogen-activation kinetics. Modulatory effects of trans-4-(aminomethyl)cyclohexane-1-carboxylic acid and poly-D-lysine on plasminogen activation.

The kinetics of plasminogen activation catalysed by urokinase and tissue-type plasminogen activator were investigated. Kinetic measurements are performed by means of a specific chromogenic peptide substrate for plasmin, D-valyl-L-leucyl-L-lysine 4-nitroanilide. Two methods are proposed for the analysis of the resulting progress curve of nitroaniline formation in terms of zymogen-activation kinetics: a graphical transformation of the parabolic curve and transformation of the curve for nitroaniline production into a linear progress curve by the addition of a specific inhibitor of plasmin, bovine pancreatic trypsin inhibitor. The two methods give similar results, suggesting that the reaction between activator and plasminogen is a simple second-order reaction at least at plasminogen concentrations up to about 10 microM. The kinetics of both Glu1-plasminogen (residues 1-790) and Lys77-plasminogen (residues 77-790) activation were investigated. The results confirm previous observations showing that trans-4-(aminomethyl)cyclohexane-1-carboxylic acid at relatively low concentrations enhances the activation rate of Glu1-plasminogen but not that of Lys77-plasminogen. At higher concentrations both Glu1- and Lys77-plasminogen activation are inhibited. The concentration interval for the inhibition of urokinase-catalysed reactions is shown to be very different from that of the tissue-plasminogen activator system. Evidence is presented indicating that binding to the active site of urokinase (KD = 2.0 mM) is responsible for the inhibition of the urokinase system, binding to the active site of tissue-plasminogen activator is approx. 100-fold weaker, and inhibition of the tissue-plasminogen activator system, when monitored by plasmin activity, is mainly due to plasmin inhibition. Poly-D-lysine (Mr 160 000) causes a marked enhancement of plasminogen activation catalysed by tissue-plasminogen activator but not by urokinase. Bell-shaped curves of enhancement as a function of the logarithm of poly-D-lysine concentration are obtained for both Glu1- and Lys77-plasminogen activation, with a maximal effect at about 10 mg/litre. The enhancement of Glu1-plasminogen activation exerted by trans-4-(aminomethyl)cyclohexane-1-carboxylic acid is additive to that of poly-D-lysine, whereas poly-D-lysine-induced enhancement of Lys77-plasminogen activation is abolished by trans-4-(aminomethyl)cyclohexane-1-carboxylic acid. Analogies are drawn up between the effector functions of poly-D-lysine and fibrin on the catalytic activity of tissue-plasminogen activator.

Aprotinin↗
PubMed1975

Blood-brain transfer of d-glucose, l-leucine, and l-tryptophan in the rat.

Recently Oldendorf developed a method for measurement of the early uptake of substances from the capillary bed into brain tissue after a single capillary passage of a bolus injected rapidly into the common carotid artery of the rat. The uptake of a test substance is expressed relative to the uptake of a highly diffusible reference substance, tritiated water. In this study experimental data are presented allowing to correct the uptake values for the unknown loss of tritiated water, so that the fractional unidirectional uptake (Extraction, E) can be calculated. This method is used to investigate the uptake kinetics for D-glucose, L-leucine, and L-tryptophan. For the three substances investigated the uptake kinetics involved both saturation and linear kinetics. Km values of 11 mM for D-glucose, 0.16 mM for D-glucose, 0.16 mM for L-leucine, and 0.19 mM for L-tryptophan were found. The uptake capacity, Vm, was calculated using a blood flow value of 0.85 ml/(g x min); Vm was for D-glucose 1.6, for L-leucine 0.027, and for L-trytophan 0.024 mumol/(g x min). The D-glucose Vm in the present study is comparable with Vm values in the literature, and indicates that the method may be employed for quantitative analyses of the blood-brain transfer of solutes.

Animals↗
PubMedDate not supplied

User-requirements driven learning.

This paper describes an approach for deriving classification knowledge from databases, taking into account user preferences. These preferences especially concern the trade-off between different kinds of costs and performance indicators of the classification scheme to be developed. We analyze what knowledge, provided by the user, can be used at various stages of the machine learning process to influences the development of the classifier. We restrict ourselves in this paper mainly to the generation of classification trees.

Algorithms↗
PubMedDate not supplied

Trends in assessment of IT-based solutions in healthcare and recommendations for the future.

State-of-the-art assessments of IT-based solutions in Healthcare is discussed in this paper. Special emphasis is placed on the human and organisation-centred perspective at the development of IT-based solutions. Based on this and basic conditions for system analysis and design reported in the literature, requirements for a methodology for user-driven, constructive assessment during the entire life-cycle of the IT-based system are synthesised. Finally, the outcome is discussed in the light of the presentations on technology assessment during the MIE 97 Congress and other related literature.

Computer Systems↗