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PubMedDate not supplied

Interpretation of laboratory results using multidimensional scaling and principal component analysis.

Principal component analysis (PCA) and multidimensional scaling (MDS) are a set of mathematical techniques which uncover the underlying structure of data by examining the relationships between variables. Both MDS and PCA use proximity measures such as correlation coefficients or Euclidean distances to generate a spatial configuration (map) of points where distances between points reflect the relationship between individuals with their underlying set of data. Multidimensional scaling, when compared to PCA, gives more readily interpretable solutions of lower dimensionality and does not depend on the assumption of a linear relationship between variables. Both MDS and PCA were applied to electrolyte profiles of patients with acute renal failure and patients without apparent disease. The MDS was superior to PCA in separating renal patients from normal patients. The one-dimensional and two-dimensional solutions of MDS and PCA were compared.

Acute Kidney Injury↗
PubMed1986

[Monitoring of cardiac output during use of bupivacaine 0.75% by ventriculography (99mTC)].

Fifteen patients undergoing orthopaedic surgery on the lower limbs were give continuous epidural anaesthesia with bupivacaine 0.75%. It was looked after changes in heart frequency, beat volume and changes in heart rhythm. Changes in cardiac output were investigated by ventriculography with 99mTC during 4 periods--10 min before and 10, 20 and 30 min after epidural blockade--the cardiac output was measured by a computer mathematically. Each patient received 2 mg/kg body weight of bupivacaine 0.75%. Besides the observation of blood pressure, heart rate and electrocardiogram the venous plasma levels of bupivacaine were measured up to 60 min after blockade. The results showed no changed in cardiac output. Except for one case with bradycardia--which could be treated with atropine--no changes in heart frequency occurred. Tachy- or bradycardia was not seen at all. Besides rare respiratory sinus arrhythmia no arrhythmia could be detected. The venous plasma levels of bupivacaine increased after 30 min up to 0.81 microgram/ml. The highest concentration measured was 1.45 microgram/ml 10 min after injection of bupivacaine. According to the results of the study the following statement can be given: Following bupivacaine 0.75% (2 mg/kg) given epidurally no changes in cardiac output, no changes in beat frequency, no pathological changes in cardiac rhythm and no specific cardiac toxicity related to bupivacaine 0.75% could be found in this study.

Adult↗
PubMed1984

A new approach to the design of information systems for foodservice management in health care facilities.

An organizational framework for integrating foodservice data into an information system for management decision making is presented. The framework involves the application to foodservice of principles developed by the disciplines of managerial economics and accounting, mathematics, computer science, and information systems. The first step is to conceptualize a foodservice system from an input-output perspective, in which inputs are units of resources available to managers and outputs are servings of menu items. Next, methods of full cost accounting, from the management accounting literature, are suggested as a mechanism for developing and assigning costs of using resources within a foodservice operation. Then matrix multiplication is used to illustrate types of information that matrix data structures could make available for management planning and control when combined with a conversational mode of computer programming.

Accounting↗
PubMed1978

[Adipocyte size in primary hypertriglyceridemia with and without obesity (author's transl)].

Adipose tissue cellularity of patients with endogenous hypertriglyceridemia whether associated with obesity or not has been studied by means of a semiautomatic method of counting and sizing osmium tetroxide fixed adipocytes. Cell population distributions were analyzed by mathematical computation. The Coulter Counter system was able to determine mean diameter (or volume) and cell size dispersion which defined adipocyte population. An overall shift of cell population size has been found to characterize adipose tissue cellularity of the different groups examined. Adipocyte population in the obese was defined by increased fat cell size with overlapping distributions between both groups of same weight. Nevertheless normolipemic obese patients were characterized by larger cell size than hypertriglyceridemic subjects matched for adiposity index. The results are discussed in relation to the removal defect found in endogenous hypertriglyceridemia.

Adipose Tissue↗
PubMed1991

A mathematical model and computer simulation study of insulin receptor regulation.

A homeomorphic mathematical model of cell surface insulin receptor regulation is developed. The overall structure of the model is based on molecular mechanisms suggested by in vivo and in vitro experimental evidence from many different cell types. Model parameters correspond to cellular processes which are constrained by known boundry value conditions. As an example, computer simulation results are compared with published data from BC3H-1 myocytes in culture. With appropriate parameter choice, this model is able to simulate data from other cell types. Cellular processes which are explicitly represented in the model include: bound and unbound receptor endocytosis, receptor recycling, intracellular receptor degradation, and state-dependent receptor synthesis. Most of these processes are represented as first-order events. Using more complex representations of the model structure with higher order rate constants or saturable pathways does not qualitatively improve simulation results. Simulations are able to reproduce ligand-induced down and up regulation of receptors as well as the initial spontaneous display of surface insulin receptors. To demonstrate the behavior of our model and illustrate its utility for explaining insulin receptor regulation for a variety of conditions, simulations for which experimental data is unavailable for direct comparison are also shown. We believe the structure of our model is sufficient to explain insulin receptor regulation in a wide variety of cell types. In addition our model may aid in understanding the receptor component of insulin resistance (decreased sensitivity or responsiveness to insulin) seen in pathological states such as obesity and diabetes mellitus. Finally, this model may be applicable to the study of the regulation of other polypeptide hormone receptors.

Cell Membrane↗
PubMed1991

A mathematical model and computer simulation study of insulin sensitive glucose transporter regulation.

A mathematical model of insulin sensitive glucose transporter regulation is developed. Model structure is based on experimental evidence from adipocytes and myocytes. Model parameters correspond with known cellular processes. As an example, computer simulation results are compared with data from rat adipocytes. Cellular processes explicitly represented in the model include state-dependent glucose transporter synthesis and degradation rates, insulin sensitive glucose transporter translocation rates, and a glucose transporter endocytosis rate. Most of these processes are represented as first-order events. Using more complex representations of the model structure (e.g. higher order rate constants or saturable pathways) or alternative structures did not result in qualitatively better results. The model is able to accurately simulate the insulin sensitive, insulin concentration dependent, reversible translocation of glucose transporters observed in normal adipocytes. The model is also able to accurately simulate the changes in regulation of glucose transporter translocation observed with increases in cell surface area. Finally, the model can simulate pathogenic states which induce impairment of glucose transporter regulation (e.g. altered glucose transporter regulation in adipocytes from rats on high fat diets, rats with streptozotocin induced diabetes, and fasted rats). Since the structure of our model is sufficient to explain glucose transporter regulation in both normal and pathological states, it may aid in understanding the post-receptor components of insulin resistance (decreased sensitivity or responsiveness to insulin) seen in pathological states such as obesity and diabetes mellitus.

Adipose Tissue↗
PubMed1985

Validation of a mathematical procedure for computer analysis of flow cytometric DNA data in human tumors.

The determination of tritiated thymidine labeling index and the percentage of cells with S phase DNA content was performed on cell suspensions obtained from 69 patients with non-Hodgkin's lymphoma. The distributions of cells in the cell cycle by computer analysis of flow cytometric data were obtained by two mathematical procedures: the widely adopted Fried model and a new one proposed by Bruni et al. A significant agreement was observed by checking the Spearman index (rs) between the percentages of cells in the different cell cycle phases (G0/1, rs = 0.76; S, rs = 0.60; and G2 + M, rs = 0.43; p less than 0.001) determined by the two procedures. Similarly, a good correlation was observed between the labeling index (LI) and the S phase values obtained by the Fried (rs = 0.45, p less than 0.001) and Bruni (rs = 0.69, p less than 0.001) models, but with a higher agreement for the latter one. The S phase by the Bruni model was also superior in predicting LI: in fact, by employing the S cutoff value of 12%, a better agreement between low LI and low S phase or high LI and high S phase was observed with the Bruni procedure (90%) than with the Fried model (72%). Finally, the analysis of the prognostic significance of the different kinetic variables confirmed the prognostic relevance of LI at any time; the S phase percentage as determined by Bruni et al. was discriminant of survival only at shorter times, and no prognostic significance could be ascribed to S phase according to the Fried procedure.

Adult↗
PubMed1991

Theory of ocular dominance column formation. Mathematical basis and computer simulation.

A general theory previously proposed by the author which describes synaptic stabilization on the basis of three basic assumptions is employed for the understanding of ocular dominance column formation. A reduced mathematical model is constructed based on the thermodynamics in the Ising spin variables representing the afferent synaptic connection distribution. The results of Monte Carlo simulations on the segregation of ipsilateral and contralateral synaptic terminals in the input layer of the primary visual cortex suggest the existence of phase transition phenomena. Three types of ocular dominance column patterns--stripe, blob, and uniform--are visualized according to the values of the correlation strength and the degree of imbalance in activity between the left and right retinas. The theory presented here successfully explains how ocular dominance columns are developed.

Animals↗
PubMed1978

[Role of computer technology and mathematical modelling in the treatment of patients after operations on the heart].

On the basis of ten-year experience in theoretical studies and experimental tests mathematical models of hemodynamics were built for the follow-up of parameters of the cardiovascular system which cannot be determined by means of any other modern methods. Three years of clinical studies of the Hewlett-Pachard monitoring computer system and its modification helped to elaborate the mathematical backing, a bank of mathematical models, original automatic programs for measuring the cardiac index, the index of myocardial viability, etc. The automatic system provides for an individual approach in assessing the patient's condition in actual time and for control of the treatment.

Cardiac Surgical Procedures↗