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Biomedical subjects

F Kaden

Publications and source records attributed to F Kaden.

11 recordsLinked to original sources
PubMed1992

Applying machine learning methods for finding significant amino acid properties in proteins.

There are several possibilities for definition and derivation of sequence patterns associated with structural motifs, in particular on the secondary structure level which may be used to predict these structure elements. Sequence patterns consist of a number of consecutive positions along the polypeptide chain from which a certain quantity is specified. One of the important factors in deriving sequence patterns in terms of amino acid properties is how to find the most characteristic properties to specify a certain position and thus to avoid redundant physical information. We have applied machine learning methods to select the most significant amino acid properties describing a structurally determined sequence position. Results are given for the beginning of alpha-helices. These methods may link the gap between amino acid patterns and property patterns and thus are valuable to improve protein structure prediction.

Amino Acids↗
PubMed1992

Analysis of protein sheet topologies by graph theoretical methods.

In order to find rules for the secondary structure prediction of proteins which describe the (sequentially) long-range interactions in sheet structures methods of applied graph theory were used. The so called beta graph which describes the sheet topology was defined for every protein in the Brookhaven Data Bank containing beta sheets. The resemblance of proteins at that topological level is discussed, and four notations and graphic representations of sheets which describe the sequential and topological neighborhoods of the strands were derived. This description level supports the usage of data structures which allow the implementation of efficient algorithms for the analysis and comparison of beta structures in proteins. A computer program for the representation and retrieval of bibliographic data and beta sheet structures was implemented. Some examples for substructure search illustrate the usefulness of the program. Two graphic catalogues were compiled: one contains all beta graphs of PDB proteins and the other all occurring different greek key descriptions.

Computer Simulation↗
PubMed1978

[The effect of etilefrine and dihydroergotamine on sympathetic nervous system activity when standing up (author's transl)].

Systolic blood pressure, heart rate and concentrations of adrenaline, noradrenaline and dopamine as well as plasma dopamine-beta-hydroxylase (DBH) were measured in 22 subjects in recumbency and on standing up. Six subjects each had previously been given intravenously dihydroergotamine (0.5 mg) or etilefrine (0.25 mg/min) or a placebo. It was demonstrated that orthostasis leads to an increased activity of the sympathetic nervous system and the adrenal system. After administration of dihydroergotamine there was a diminished reaction of the sympathetic nervous system with an increase of venous tone which counteracted the decrease in cardiac output. Etilefrine, on the other hand, inhibited the sympatho-adrenal reaction on orthostasis and decreased the liberation of adrenaline. It acts directly via stimulation of alpha-and beta-receptors and is thus predominantly indicated if there is insufficient response of the baroreceptor reflex at its efferent limb.

Adult↗
PubMed1977

[Dopamin-beta-hydroxylaseaktivität im Plasma von Dialysepatienten (author's transl)].

Plasma dopamin-b-hydroxylase (DBH) was studied in 70 healthy control persons and in 37 hemodialysed patients. Basal DBH in controls corresponded to 50.0 +/- 29.3 IU. There was was no significant difference between males (53.9 +/1 33.8 IU) and females (47.4 +/- 25 IU); no correlation could be found between age and plasma DBH. In hemodialysed patients basal DBH levels were significantly (p less than 0.01) decreased (32.5 %/- 17.6 IU), suggesting lowered sympathetic activity and/or abnormalities in release, distribution space, or metabolism of DBH. During hemodialysis plasma DBH activity rose during ultrafiltration. This finding indicates a directionally appropriate sympathetic reflex response to volume depletion in dialysed patients.

Adolescent↗
PubMedDate not supplied

[Injection methods for the demonstration of the coronary arterial vasculature (author's transl)].

Four different methods for the demonstration of the coronary arterial vasculature are examined. Among the techniques studied corrosion casts (epoxid- and acrylic resin) permit the best qualitative and quantitative evaluation of superficial and deep arteries and arterioles. Down to the smallest infusible vessels of 15-25 mum there is practically no shrinkage. X-ray arteriography with an aqueous solution of barium sulphate is less suitable because X-rays allow no satisfactory stereoscopic view. The demonstration of arterioles and collaterals is limited to vessels larger than 50 mum because of the low resolution of the X-ray tube. Silicone rubber does not only fill the arteries, but also the capillary bed and the venous system. Therefore deeper parts of the vasculature can only be studied after slicing the heart. The substantial shrinkage of the material makes quantitative measurements difficult.

Animals↗