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Biomedical subjects

F Vyskocil

Publications and source records attributed to F Vyskocil.

At least 109 records · Page 6Linked to original sources
PubMed1983

The measurement of K+e concentration changes in human muscles during volitional contractions.

Changes of extracellular potassium concentration [( K+]e) were measured in human muscles during volitional isometric contractions using liquid ion-exchanger electrodes. In principle, an intramuscular injection needle containing a microelectrode with a side-pore was inserted into the brachioradialis muscle. After insertion of the needle, the glass ion-selective microelectrode (ISM) could be moved out of the protective trocar shield into the muscle tissue. The average values of [K+]e in human muscles during maximal effort rose from 4.5 mmol/l K+ to 9.5 mmol/l K+. These values correspond closely to those previously found in muscles of experimental animals.

Extracellular Space↗
PubMed1982

Primary afferent depolarization and changes in extracellular potassium concentration induced by L-glutamate and L-proline in the isolated spinal cord of the frog.

To test the hypothesis that L-proline acts as an antagonist on glutamate receptors [17, 18], the interaction between L-glutamate and L-proline was studied in the isolated spinal cord of the frog. Glutamate at concentrations of 10(-6) -5 x 10(-3) mol/l depolarized the primary afferent fibres and increased extracellular potassium concentration, [K+]e, by 0.3-4 mmol/l. Repeated applications lead to inactivation of the response. L-Proline at 5 x 10(-3) -10(-2) mol/l, also depolarized the primary afferents and increased [K+]e by 0.5-2 mmol/l, but there was only a slight decrease of the effects after repeated application. The effects were additive when the amino acids were applied simultaneously. The effect of L-proline was still present when it was applied during inactivation of the glutamate receptors. This suggests that L-glutamate and L-proline act on different receptors.

Afferent Pathways↗
PubMed1982

The comparison of vanadyl (IV) and insulin-induced hyperpolarization of the mammalian muscle cell.

Extracellularly applied vanadyl (IV) hyperpolarized the membrane potential of mouse diaphragm muscle from about -74.0 mV up to -81.7 mV. The hyperpolarizing effect of 10(-4) mol.I-1 vanadyl (IV) is comparable with hyperpolarization induced by 100 mU.ml-1 insulin. Both compounds increased the intracellular K+ concentration, the hyperpolarizing effect of vanadyl (IV) and insulin is blocked by ouabain and is unaffected by removal of K+ from the external medium. Triggering of the release of intracellular K+ associated with cellular proteins is proposed as the mechanism of vanadyl (IV) and insulin-induced hyperpolarization.

Animals↗
PubMed1982

Postdenervation changes of intracellular potassium and sodium measured by ion selective microelectrodes in rat soleus and extensor digitorum longus muscle fibres.

The intracellular concentration of free [K+]i and [Na+]i in innervated and denervated rat extensor digitorum longus (EDL) and soleus (SOL) muscles was measured by double-barrel glass microelectrodes filled with liquid ion exchanger. In both muscles, postdenervation fall of resting membrane potential was accompanied by a decrease of [K+]i and increase of [Na+]i. The relative permeability, PNa/PK of the muscle fibre membrane increased three times in EDL and 1.5 times in SOL respectively by the third day of denervation and then dropped within 14 days to the values which were only slightly but significantly lower than the control ones.

Animals↗
PubMed1982

Extracellular potassium concentration in normal and denervated hind limb muscles of the rat.

K+-sensitive electrodes with a side pore were used for measuring extracellular potassium levels in control muscles and in the gastrocnemius, extensor digitorum and soleus muscles of the rat, one, 8 and 14 days after denervation. In all cases, the extracellular potassium level was close to 5 mmol.1-1. There were no substantial differences between muscles of different functional and morphological types and between control and denervated muscles. Elevated extracellular potassium cannot therefore be the reason for increased sensory outflow of impulses observed after motor denervation.

Animals↗
PubMed1981

Induction of extrajunctional acetylcholine sensitivity of rat EDL muscle by peptidic component of peripheral nerve.

The induction of extrajunctional ACh-sensitivity was studied electrophysiologically 4 days after implantation of segments of the sciatic nerve, segments of dorsal and ventral spinal roots and silastic plates, containing some components of peripheral nerve onto surface fibres of innervated rat extensor digitorum longus muscle. It has been found that extrajunctional ACh-sensitivity can be induced by a piece of rat sciatic nerve and by peptidic material of about 8,000 and 10,000 mol. wt. No sensitivity was induced by segments of ventral and dorsal roots, by a piece of rabbit sciatic nerve and by rat sciatic nerve sectioned 7 days prior to implantation. The active nerve fractions lost its inducing potency after pepsin pre-treatment and irradiation with UV-light. Peripheral nerve probably contains some specific factor, peptidic in nature, which is able to induce the ACh-sensitivity of muscle fibre membrane.

Acetylcholine↗
PubMed1981

The effect of vanadate on the electrogenic Na+/K+ pump, intracellular Na+ concentration and electrophysiological characteristics of mouse skeletal muscle fibre.

The present study reports a discrepancy between the effects of vanadate on the membrane Na+-K+-ATPase and the Na+/K+ pump of the skeletal muscle. Vanadate in concentration 4 X 10(-6) mol/l which is necessary to block the enzyme Na+-K+-ATPase activity of membrane fractions failed to inhibit the electrogenic Na+/K+ pump of intact muscle cells. The effect of vanadate on the electrophysiological parameters of the muscle fibre membrane required much higher vanadate levels, but again, Na+/K+ pump was still active. Vanadate in concentrations 4 X 10(-4) and 4 X 10(-5) mol/l depolarized the membrane potential and decreased the membrane resistance [apparently in consequence of enhanced passive membrane permeability for Na+ ions]. Action potentials and the electrical excitability of the muscle fibre membrane were reduced by these vanadate concentrations.

Action Potentials↗
PubMed1981

Functional properties of muscle autografts substituted for the rat levator ani muscle.

The present report deals with the functional properties (contraction parameters and neuromuscular transmission) of muscle grafts and transposed muscles substituted for the levator ani muscle in the rat. The experiments were divided into four main groups. Group I - the levator ani [LA] was excised and replaced in its own bed. Group II - the extensor digitorum longus, a fast muscle (with or without predenervation), and Group III - the soleus, a slow twitch muscle, were substituted for the LA. In group IV, the gracilis anterior muscle was either freely grafted in place of the LA or transposed a) with intact innervation, b) with its vascular supply intact or c) with preserved neuro-vascular supply. The optimum results of twitch and tetanic tension, and the amplitude of stimulation EMG responses was found in the case of LA resutured into its own bed and in the case transposition of the gracilis anterior muscle had been performed with its neuro-vascular supply intact in place of the LA. On the basis of these functional findings and morphological and anatomical observations (Grim et al. 1982), a surgical procedure is suggested for patients with anal incontinence (Grim et al. 1981, Dittertová-Vlasáková et al. 1982).

Anal Canal↗
PubMed1980

A specific enzyme is not necessary for vanadate-induced oxidation of NADH.

It has recently been found that ortho- or metavanadate can effectively block (Na+ + K+)ATPase and that it loses its blocking potency when reduced to the vanadyl (VO2+) ion. The question arose whether vanadate could be involved (reduced) in an NAD-linked enzymatic redox system of the cell. Here we have studied the effect of vanadate on malate dehydrogenase (MDH, EC1.1.1.37) catalysed oxidation of NADH during the formation of malate from oxalacetate in vitro. The MDH reaction was accelerated by vanadate, but we found thatr vanadate does not require the presence of any specific enzyme or substrate to mediate NADH oxidation.

Buffers↗
PubMed1980

Effect of temperature and ouabain on th Na+--K+ activated membrane ATPase and electrogenic ionic pump of the golden hamster and mouse diaphragm.

The activity of membrane Na+--K+-ATPase and electrogenic ionic pump was estimated by biochemical and electrophysiological techniques on diaphragm muscles of mouse and non-hibernating golden hamster between 5 degrees C to 37 degrees C. The electrogenic capacity of ionic pump (measured as maximum hyperpolarization after adding 5 nmol/l K+ to Na+-enriched muscle) was highest at 37 degrees C for the mouse and between 25--30 degrees C for the golden hamster. At lower temperatures (15 degrees C--5 degrees C), the hyperpolarization after adding K+ reversed to depolarization between 15 degrees C and 10 degrees C in the case of the mouse. In the hamster, the slight hyperpolarization persisted even at 5 degrees C. With decreasing temperature, the activity of membrane ATPase of mouse and hamster membrane fraction decreased in both cases to the same extent between 37--25 degrees C. Within the temperature range between 10 degrees C and 5 degrees C the activity of this enzyme of hamster preparations was about 2.4 times higher than in the case of the mouse. In the mouse Na+-enriched diaphragm, ouabain (10(-4) mol/l) decreased the resting membrane potential (RMP) in a K+-free solution at 20 degrees C by about 5 mV, but in the golden hamster preparation, ouabain in the same concentration increased RMP of Na+-enriched diaphragm fibres by more than 5 mV. The activity of membrane ATPase of hamsters was increased by 10(-4) mol/l ouabain more than 2.5 times in a K+-free reaction medium, whereas in the case of the mouse no change of enzyme activity was observed. This indicates that ouabain can be substituted for potassium as an activator of membrane ATPase in the sarcolemma of golden hamster muscle fibres.

Animals↗
PubMed1979

Activation of membrane Na+/K+-ATPase of mouse skeletal muscle by acetylcholine and its inhibition by alpha-bungarotoxin, curare and atropine.

The effect of acetylcholine and of three cholinolytic compounds (alpha-bungarotoxin, curare and atropine) on electrogenic Na+/K+ pump and activity of the membrane Na+/K+-ATPase of mouse skeletal muscles was studied. It was found that acetylcholine potentiated both the muscle electrogenic ionic pump and the Na+/K+-ATPase activity of crude membrane fractions. The cholinolytic drugs had inhibitory effects on both parameters, with the exception of curare which was ineffective in blocking the electrogenic ionic pump.

Acetylcholine↗
PubMed1979

Spontaneous junctional currents in Drosophila muscle fibres: effects of temperature, membrane potential and ethanol.

Fast, slow and fast multiquantal spontaneous junctional currents were recorded from glutamate sensitive muscle fibres of Drosophila larvae. Decrease of temperature and hyperpolarization prolonged the time course of fast currents. Ethanol (0.4 M) markedly shortened their duration, whereas several other drugs known to modify the time course of currents at cholinergic synapses were ineffective at this neuromuscular junction.

Drosophila melanogaster↗