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Biomedical subjects

K Brodda

Publications and source records attributed to K Brodda.

16 recordsLinked to original sources
PubMed1990

[The base data from Weight Watcher's groups as the parameter for long-term follow-up of weight reduction].

The available data of members of Weight Watchers groups were statistically evaluated and their efficiency is discussed with respect to the underlying therapeutic concept. As a result of the data evaluation and the discussion of the literature it can be concluded: 1. The time of active membership in the group correlates with the weight loss. 2. Dropouts can be expected at the beginning of the therapy and have usually a greater obesity than other members. An early motivation has to consider the slower success in those people with a high degree of obesity. 3. A continuous motivation and re-motivation is of greatest importance to prevent any weight gain after the end of group therapy. This re-motivation program should be established within the group; members who succeeded in losing weight should return for meetings at regular intervals.

Adult↗
PubMed1990

Uptake and metabolism of retinoic acid induces inhibition of cell growth: a study in a rat rhabdomyosarcoma cell line (BA-HAN-1C) using nonlinear theoretical models.

Retinoic acid causes a significant inhibition of cell growth of the tumor cell line BA-HAN-1C. This growth inhibition is the same whether the cells are treated with a pulse dose of retinoic acid (RA) or continuously expand to RA. The determination of RA and its degradation products within the culture medium and in the cells showed that after 24 hours 13-cis-RA was the major retinoid in all cells (96 ng/10(6) cells); all-trans-RA represented 56 ng/10(6) cells. After 48 hours 4-hydroxy-RA and a small amount of 5,6-epoxy-RA was found in the cells and also in the culture medium. 4-hydroxy-RA increased up to 96 hours, whereas 13-cis- and all-trans-RA were not detectable in the cells after 96 hours. We conclude that the BA-HAN-1C cells take up and metabolize RA. Nonlinear fit analysis of the time behavior of the RA concentration in medium demonstrates that the RA uptake unexpectedly follows a mono-exponential time function. Discussion of the experimental results in connection with a proper compartment model shows that uptake and metabolism of RA cannot be described really by a first order kinetics. The mathematical analysis leads to a more complicated kinetic model with certain restrictions for the corresponding rate constants.

Animals↗
PubMed1986

Rapid determination of vitamin A (retinol) and vitamin E (alpha-tocopherol) in human serum by isocratic adsorption HPLC.

The simultaneous determination of alpha-tocopherol and retinol in human serum is reported. The separation is carried out by means of isocratic HPLC on adsorption columns. UV-Detection is possible by using either one wavelength for both compounds (300 nm), or after a lambda change mode with typical wavelengths for alpha-tocopherol (292 nm) and retinol (325 nm). According to short retention times (10 min) and rapid extraction the method is useful for clinical research and allows about 50 analyses per day and operator. Blood from 176 human volunteers was collected and alpha-tocopherol and retinol levels in serum determined with this method. Statistical evaluation of different selected groups shows typical significant differences of alpha-tocopherol and retinol concentrations in smokers and oral contraceptive users.

Adsorption↗
PubMed1985

[Importance of thyroid hormone determination in the diagnosis of hyperthyroidism--significant improvement in medical assessment using decision theory results].

A "schematic" classification of the results of serum thyroid hormone measurements on the basis of mathematical decision theory proves to be superior to the physicians' conventional evaluation. That has been shown by comparison with the evaluations made by three experienced doctors. When using no control regions (but the results of serum T4, FT4 and T3 simultaneously) the physicians' rates of misrecognition (0-2% false positives, 20-27% false negatives) are only a little lower than when classifying schematically on the basis of only one thyroid hormone. The construction of a suitable control region, however, results when T3 alone is used, in only 7% false negative and 0% false positive results, while these rates remain nearly unchanged for the physicians' evaluations. The optimum application of mathematical decision theory is only possible with the knowledge of the statistical distributions of the thyroid hormone data, both for a representative collective of normals and that of patients with proven hyperthyroidism. Thus, quantitative criteria for the effectiveness of each set of thyroid hormones can be constructed and a multivariate analysis can be performed, in our example - when applying suitable control regions - even with vanishing rates of misrecognition.

Decision Theory↗
PubMed1984

On the optimum selection of diagnostic tests in computer-aided differential diagnosis.

A new method with multivariate individual selection of diagnostic tests for computer-aided differential diagnosis is presented. It has been developed on the basis of new results of our own in the field of mathematical decision theory. Its application to the differential diagnosis of four congenital heart diseases by means of ECG features proves our method to be superior to the usual multivariate statistical analysis. Establishing the individual optimum sequence of diagnostic tests for each patient our diagnostic procedure needs only two-thirds of the diagnostic tests used by the methods until now without an increase of the error rate. The error rate can be further reduced by additional introduction of the so-called reserved diagnostic statement. The managing of our procedure may be compared with the diagnostic behavior of a physician.

Child↗
PubMed1980

A computer program suitable for analysis of choice of categories in biomedical data recognition problems.

The optimum choice of categories in problems of medical data recognition is governed by the choice of categories, the selection of appropriate features, and by the choice of a loss function. Under these circumstances it is often difficult to find out the suitable classification scheme. The computer program described here serves for the design of the optimum recognition procedure. The Bayes rule is used as decision rule. A criterion for the comparison of different choice of categories is given. The program can be performed after estimation of the underlying prior probabilities and the conditional densities obtained from a training set, and before testing the decision rule with real data.

Classification↗
PubMed1978

Changes of the ratio between myelin thickness and axon diameter in the human developing sural nerve.

Axon caliber and myelin sheath thickness of individual nerve fibers were evaluated in the developing human sural nerve using three different methods of measurement: 1. ocular micrometer evaluation of large fibers, 2. photographic enlargements for evaluating large numbers of nerve fibers of all sizes, and 3. electron microscopic enlargements for more precise measurements in selected nerves. The average axonal diameter doubles from 5 months gestation to about 5 years of age. Large fiber group axons increase, during the same period, by a factor of 3--3.5 with a slight decrease thereafter. The myelin thickness increases more slowly, but continuously, between 5 months gestation until the age of 14. This asynchronous development of axons and myelin sheaths results in a statistically significant change of the ratio between axonal caliber and myelin thickness. The slope of the regression line is steeper in older than in younger individuals, and the correlation coefficient increases during development of the nerve.

Adolescent↗
PubMed1975

On the theory of base excess curve in the Siggaard-Andersen nomogram.

Two definitions of the base excess (BE) curve are known. The first definition is a geometrical one. We call the second definition the physicochemical one. These definitions are only valid if the water shift between red blood cells and plasma caused by pH alteration is neglected. We show that under this condition the BE curve cannot be calculated according to the mentioned definition. On the contrary we get a well-defined BE curve by calculation only if water shift is taken into account. In that case we must modify the physicochemical definition. The modified equations redefining the BE curve are derived. Furthermore the equivalence of both the geometrical definition and the modified physicochemical definition is shown. Using the modified definition the BE curve is calculated and compared to the curve measured by SIGGARD-ANDERSEN.

Acid-Base Equilibrium↗