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Biomedical subjects

G Küchler

Publications and source records attributed to G Küchler.

At least 37 records · Page 2Linked to original sources
PubMed1981

Effects of repeated fatiguing rhythmical hand work.

In a model work place (hand-grip dynamometer), eleven subjects performed rhythmical hand-grip contractions to exhaustion (frequency 30/min). In each working cycle the contraction and rest phases were distinguished. The work to exhaustion was repeated four times (four working periods with 156-min rest intervals). The tests were performed at 40, 60, 80, 100% MVC. Analysis of Variance showed no difference in the group means (mean values of each working period and load level) for the duration of the contraction or rest phases, the integrated bioelectrical muscle activity (iEMG) of flexors, extensors, brachioradialis (iEMG referred to working cycle and contraction phase) or iEMG of the thenar muscles (referring to the working cycle), or in the duration of the R-R interval in the ECG during comparable periods of the experiments. The endurance times decreased from working period 1-4, and a similar decrease occurred in the force-time product. It may be concluded from these results that 15 min rest is insufficient for adequate recovery from hand-exhaustion exercise.

Adult↗
PubMed1980

The influence of free fatty acids on functional properties of isolated skeletal muscles. Octanoate action on membrane resistance.

1. Na-octanoate (in Ringer's solution) affects the membrane resistance of isolated frog skeletal muscle fibres in a biphasic way. Initially there is an increase followed by a more slowly developing decrease. The effect depends on both the concentration of the fatty acid (1-20 mM) and the time of exposure (2-20 min). 2. In muscles exposed either to isotonic K2SO4 or to Ringer's solution with Cl- substituted by methylsulphage, the octanoate-induced resistance drop is the same as in normal Ringer's solution whereas an initial increase is not observed. 3. In Na-free (Tris-) Ringer's solution, only an increase in membrane resistance is caused by octanoate. 4. The results suggest that Na-octanoate decreases the conductance of the resting muscle cell membrane for anions (Cl-1) whereas the permeability for cations (Na+, K+) is increased.

Action Potentials↗
PubMed1980

Octanol and octanoate induced inhibition of the mechanical activity of isolated frog skeletal muscles.

Octanol (1 mM) or octanoate (10 mM) almost totally depress the contraction amplitude of directly stimulated muscles in a few minutes. Octanoate in a concentration of 2 mM/l decreases the contraction amplitude by 20% and retards the caffeine contracture. The ratio between twitch and tetanus is affected by octanol only. The results suggest that octanol and octanoate alter binding or releasing properties for Ca2+ of skeletal muscle cells.

Animals↗
PubMed1980

Properties of a combined sensor for dynamic measurement of oxygen in simulated respiration.

A combined sensor supplying momentary values of respiratory functions (flow, PO2, and temperature) for calculation of oxygen intake is tested in simulated respiration. Signal conditioning reduces the errors caused by the influence of CO2 on the sensitivity of the oxygen electrode, by the electrode response and time lag. Oxygen intake of 0.38 and 1.49 liters/min simulated by injection of N2 into the respiration pump (10--40 cycles/min) is analyzed by means of the combined sensor (signals conditioned; time constant about 40 msec) and calculated with a mean error of about -10%. The error rises with increase of the time constant as well as the respiration frequence.

Carbon Dioxide↗
PubMed1980

[Effect of homologous n-alkanoic acids on the function of isolated skeletal muscles. IV. Effect of Na-octanoate on action potentials].

Na-octanoate decreases the amplitude, the rate of rise, and the rate of repolarization of the action potential of isolated frog skeletal muscle fibres. The threshold for excitation is increased but the conduction velocity of the action potential is decreased by octanoate. The effects depend on both the concentration of the fatty acid (0.5-8 mM) and the time of exposure (5-20 min). It is suggested that octanoate alters the conductance changes associated with a membrane action potential. The possible role of an octanoate-induced decrease in Cl(-)-permeability is discussed.

Action Potentials↗
PubMed1980

[Effect of homologous n-alkanoic acids on the function of isolated skeletal muscles. V. Relations between twitch, tetanus and contracture].

Twitch, tetanus, and contractures induced by potassium ions (K+) or caffeine were investigated on isolated bundles of frog muscles. Using supramaximal stimuli the twitch amplitude amounts to about 50% of the tetanic tension (22 degrees C). Usually the contracture in 190 mM K+ is smaller than the tetanic tension, in 20 mM caffeine the contracture maximum corresponds to the tetanus amplitude. All of the mechanical answers are diminished if the fibres were bathed in solutions containing 2.5 to 10 mM Na-octanoate or 0.5 mM decanoic acid. Twitch and tetanic tensions decrease nearly in the same degree. A sequence of tetanic stimulations in a distance of 2 s induces a depression of the amplitudes. Fatty acids increase this depression and delay restoration between the series. Contractures in 190 mM K+ are diminished by a preceding bath in 10 mM Na-octanoate. Contractures with submaximum concentrations of K+ were decreased by lower concentrations of octanoate. The caffeine induced contractures are delayed by fatty acids, but the maximum tension is not reduced. It is supposed that the mobilisation of calcium ions is alterated by fatty acids. The decreasing effect of fatty acids on the mechanical activity, induced by different ways of the muscles' stimulation suggests that the main action may take place in the process of mechanical coupling, probably during the activation of calcium ions.

Animals↗
PubMed1978

[Muscle activity and heart rate during rhythmical work using a hand ergometer. II. Heart rate, mechanical and bioelectrical activity of muscles during work with different loads and in relation to endurance].

The study has been made to analyse changes in heart rate, in mechanical and bioelectrical muscle activity during thythmical handgrip contractions. Loads of 20% to 100% of the maximal voluntary contraction (MVC) were applied. The working frequency was 30 cpm. With loads of 40%--100% of the maximal voluntary contraction (MVC) the following characteristic changes were obtained: Both the plane of the mechanogram and the duration of the mechanogram increased permanently. The heart rate rose to the end of the experiment and so did the EMGs of the flexor, the extensor, the brachioradial muscle and the muscle of the thenar. The rate of the rise (%/s) of all physiological functions was greatest during maximal load test and decreased with decreasing contraction strength. The endurance as a function of the force showed a parabolic curve. The physical endurance capacity of this rhythmical hand work is between 20% and 40% MVC.

Female↗
PubMed1977

[Influence of homologous n-alcanoic acids on the function properties of isolated skeletal muscles. III. Contractures by fatty acids and relations to the effects of caffeine].

The influences of octanoic, decanoic, and hexadencanoic acid were tested on the contracture capability of isolated skeletal muscle of frogs and rats. 1. 100 mM octanoic or 10mM decanoic acid induce contractures in skeletal mucles after 20-30 min of exposure. 2. The time of exposure necessary for induction of contractures is shortened by an increase of bath temperature, electrical stimulation or KCl-depolarization of muscles. 3. Simultaneous addition of fatty acid and caffeine (10 mM) effects a depression and a delay of the caffeine contracture. The contractures evoked by 5 mM caffeine are inhibited by lower concentrations of fatty acids (1 mM octaonoic acid, 0,1 mM hexadecanoic acid). 4. After the complete development of a caffeine (or fatty acid) contracture the muscle is not able to develop an identical contracture by a second application of the same drug, even after intermediate treatment during one or two hours in Ringer solution. If the contracture is interrupted one minute after the caffeine application by changing the solution, the tension returns quickly to the resting level. A subsequent addition of caffeine (10 mM) after about 10 minutes effects an identical contracture. Thus the effect of fatty acids on caffeine contracture may be studied on the same muscle which served as its own control. 5. As mechanisms involved in the development of fatty acid contractures and in the inhibition of caffeine contractures, interactions of free fatty acids and lipids of biological membranes are disucssed. Especially, there may be changes of the calcium affinity of cellular membranes.

Animals↗
PubMed1977

[Muscle activity and heart rate during rhythmical work on the hand ergometer. I. Heart rate, bioelectric muscle activity and mechanogram relative to the strength of contraction].

The experiments were carried out on 11 subjects ranging in the age from 23 to 37 years. Heart rate, integrated electrical activity from 4 muscles of the forearm and the hand and mechanical activity were measured simultaneously during rhythmical work using a hand-ergometer. The strength of the dynamic contractions was 20, 40, 60, 80 and 100% of a maximal voluntary contraction. The mean values of the maximal voluntary contraction obtained on male subjects were 57.3 kp and on female subjects 33.2 kp. The results showed that during dynamic contractions mechanical activity was related to the integrated electrical activity and both integrated electrial activity of 3 muscles and heart rate were linearly related to the load. The correlation coefficients for the EMG/EMG relationships of different muscles and for the EMG/heart rate varied between 0.83 and 0.98.

Adult↗
PubMed1977

[Influence of static muscle tension on acoustically evoked brain potentials, changes in skin resistance and bioelectric muscle activity].

Auditory evoked brain potentials (AEP), galvanic skin responses (GSR) and auditory evoked bioelectrical muscular responses were recorded in 16 male human subjects during voluntary isometric contraction of m. triceps brachii dexter. The electromygraphically controlled strength of muscular innervation corresponded to 20, 30, 40 and 50% of the maximal voluntary contraction. The trials were organized according to a change-over design. The following results could be obtained: The stepwise increase of the strength of muscular innervation effected an increase of the mean amplitude of auditory evoked EMG responses. The N1-P2 amplitudes of the AEP decreased with increasing strength of muscular innervation. The mean amplitude of the auditory evoked galvanic skin response was not changed significantly by the strength of muscular innervation, however, the spontaneous changes in galvanic skin resistance increased monotonously. Habituation effects were evident regarding amplitudes of AEP and GSR. The results indicate that muscular activity affects sensory information processing.

Acoustic Stimulation↗
PubMed1976

[Influence of homologous n-alkanoic on functional properties of isolated skeletal muscles. II. Membrane resting potential and the osmotic effectiveness of alkanoic acid].

The influence of butyric, hexanoic, octanoic, and decanoic acid on the membrane resting potential of isolated frog skeletal muscles were studied and the osmotic effects of n-alkanoic acids tested. 1. n-alkanoic acids cause osmotic effects like impermeable non-electrolytes (sucrose). Therefore, the permeability to alkanoic acids of the resting muscle cell membrane seems to be small. There are no differences between the acids tested. 2. The membrane resting potential is differently affected. Butyric acid in high concentration effects a hyperpolarization of the membrane whereas higher homologues (C6--C10) cause a depolarization. The depolarizing action increases with increasing concentration, exposure, and with the length of the hydrocarbon chain of the alkanoic acids. 3. It is suggested that osmotic effects are the cause for hyperpolarization of the membrane by high concentrations of butyric acid. 4. The depolarizing action of hexanoic, octanoic, and decanoic acid is discussed with regard to alterations induced by alkanoic acids in the membrane permeability and/or in the metabolism of the cells.

Alkanes↗
PubMed1976

[Influence of homologous n-alkanoic acids on functional properties of isolated skeletal muscles. I. Muscle contraction].

1. The contractility of isolated muscles of the frog (and in some instances of the rat) was investigated at room temperature in Ringer's solutions containing homologous alkanoic acids (100 mM C4 to 0.4 mM C10). 2. Free fatty acids decrease the contraction amplitudes evoked by direct stimulation. The effects increase with concentration, exposure, and chain length of the fatty acids. In Ringer's solution the changes are totally or partly reversible. 3. The depression of contraction amplitude induced by free fatty acids is removed by small concentrations of caffeine (2--5 mM) in Ringer's solution. 4. Interactions of fatty acids with different structures of skeletal muscle (mitochondria, sarcolemma and membranes of sarcoplasmic vesicles) are discussed. The distinct effect of fatty acids on stimulated muscles and the importance of membranes in the regulation of the calcium ion concentration in the cytoplasm suggest that fatty acids interact with membrane lipids.

Alkanes↗
PubMed1976

A combined sensor suitable for telemetering respiratory functions.

A system for measuring oxygen consumption from momentary respiratory values of free moving person is described. The main part presented here is a sensor consisting of a flowmeter based on the impeller principle, called 'Wirbelrespirometer', joint with a polarographic electrode sensitive to oxygen, and a very fast reacting thermistor. First comparative studies in computation of respiratory volume and oxygen consumption yielded average deviations against comparison methods of less than +/- 1% for computation of volume, and +/- 4% for computation of oxygen consumption.

Electrodes↗
PubMed1975

[Influence of homologous n-alcanols on functional properties of isolated skeletal muscles IV. Action potential].

The influence of homologous n-alkyl alcohols (C2, C4, C8) on the membrane action potentials of isolated frog skeletal muscle fibres has been studied using the sucrose-gap method. 1. The alcanols tested effect a decrease in the height of the action potential and prolong the recovery phase of the spike. The threshold for excitation is increased. 2. The amplitude of these alcanol induced effects depends on the concentration of the alcanols, on the time of exposure and on the length of the hydrocarbon chain of the alcanols. 3. Membrane resistance, membrane resting potential, and membrane capacity are not affected by concentrations of alcanols which effect changes in the membrane action potential. 4. The findings are discussed in regard to alterations induced by alcanols in the conductance changes associated with a membrane action potential.

Action Potentials↗
PubMed1975

[The spectrum analysis of the electromyogram: the adaptation of autoregressive models to the interference electromyogram].

Power-density spectra of interference electromyograms of M. biceps brach. and triceps brach. from two subjects were estimated by the Tukey spectral window and by autoregressive series. By fitting autoregressive models parametric represeentations of spectra are obtained. The models for the electromyograms obtained from biceps (agonist) and triceps (antagonist) differed in the length of the autoregressive series. The intra-individual variation of the spectra from three time intervals of the same contraction was relatively small.

Adaptation, Physiological↗