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Biomedical subjects

G Koester

Publications and source records attributed to G Koester.

9 recordsLinked to original sources
PubMed1993

Bullous pyoderma gangrenosum.

Pyoderma gangrenosum is a necrotizing, ulcerative process commonly associated with inflammatory bowel disease but also occurring in several other systemic illnesses. When associated with myelodysplastic syndromes, its clinical appearance is often atypical. We describe a patient with severe, refractory bullous pyoderma gangrenosum. At autopsy cardiac involvement was demonstrated, a finding not previously reported. Patients with this unusual variant of pyoderma gangrenosum have a grave prognosis.

Female↗
PubMed1986

[In vitro model for the study of the concentration kinetics of antibiotic combinations and their antibacterial activity].

The concentration kinetics of combinations of antibiotics similar to those taking place after i.v. administration was simulated in an in vitro model taking into account the different half-life periods of the antibiotics. A hose pump was used for continuous supply of sterile nutrient to a liquid bacterial culture containing both antibiotics in a preselected concentration and for removal of fluid from the system at an identical flow rate. To account for the different half-life periods of the antibiotics, a solution containing the antibiotic having a longer half-life in a corresponding concentration was continuously added by pumping. Samples were taken at fixed intervals to determine bacterial counts and check the expected concentrations of active substance did not contain antibiotics. This model has been developed to enable a determination of the dynamic relationship between the course of concentrations of antibiotics and their antibacterial activity. To permit a statement on the synergistic, indifferent or antagonistic activity of the combination, in analogy to the FIC indices in the checkerboard technique, the relative reduction of the bacterial count by the combination as compared to the individual components at time t was calculated. The model has been demonstrated by the example of the combined action of azlocillin and gentamicin against a strain of Klebsiella pneumoniae. In a simple way, the model permits any increase in the number of combination partners having different half-life periods. The mathematical development of the model is explained in detail.

Anti-Bacterial Agents↗
PubMed1981

Effects of iodoacetic acid on relaxation parameters of the rabbit papillary muscle.

Measurements have been made of isometric contractions and diastolic oscillations (after-contractions) in right ventricular rabbit papillary muscles at a temperature of 14.5 degrees C. The relaxation courses can be described as damped harmonic oscillations superposed on an exponential descending carrier function by using a model with six parameters. The influence of iodoacetic acid (10(-4) M) was investigated on contraction and relaxation parameters which result from approximation of the measured force values. The following changes were observed: 1. Decrease of the contraction height as well as of the amplitudes of diastolic oscillations. 2. Increase in the damping ratio and in the period of diastolic oscillations both calculated from relaxation parameters. 3. Diminution of the force range which is passed by the carrier function within 6 s of relaxation time accompanied by a transition to contracture. A fast and a slow Ca sequestration process are supposed to exist. The results indicate that both of them are influenced by iodoacetic acid.

Animals↗
PubMed1980

[Potentiation and staircase phenomena in rabbit heart atrium and their connection with inotropic vague effects].

At spontaneously beating rabbit atria in vitro longtime pauses of contraction were produced by vagal stimulation. After finishing the stimulation at once contractions took place; the first of them was potentiated. During the vagal pauses various beat interval programs were realized. After removing the sinusoidal node the same programs were repeated by variation of drive interval length. Their effects were compared to the effects in vagal pauses. All these effects were simulated by a two stores three phases model. This model allows description of potentiation and staircase phenomena as well as inotropic vagal effect and inotropic vagal escape. It suggests a connection between this two kinds of phenomena.

Animals↗
PubMed1975

[Adaptation of electropic and ionotropic vagal effects on the isolated rabbit atrium].

Long-time vagal stimulation induces a decrease of electrotropic and inotropic effects on the isolated rabbit atrium in spite of constant stimulation frequency. This decrease is defined as effect adaptation. To compensate this effect adaptation, the n. vagus was stimulated with increasing stimulation frequency. Compensation is possible for a certain period referred to as control time. The adaptation of the electrotropic effects is more delayed and weaker than the inotropic effect adaptation. The control times of the electrotropic effect are longer than those of the inotropic effect. Acetylcholine perfusion without vagal stimulation shows the same results. It was shown that the effect adaptaion does not result from depletion of acetylcholine stores or from co-stimulation of sympathetic nerve fibres. The effect adaptation is discussed as being the result of machano-electrical coupling.

Acetylcholine↗
PubMed1975

[Quantitative description of the adaptation of vagal effects by means of an electromechanical coupling model].

A four compartments model describes the electrotropic and the inotropic vagal effect time courses during long time stimulation. The model realises electro-mechanical coupling. A differential equation for the coupling model is developed, solutions are given and a numerical treatment is described. The model shows the essential properties of effect adaptation: time delay and smaller extent of electrotropic effect adaptation.

Action Potentials↗