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Biomedical subjects

A Szücs

Publications and source records attributed to A Szücs.

At least 19 recordsLinked to original sources
PubMed2004

Orgasmic aura--a report of seven cases.

We report on seven patients who experienced an orgasmic aura at the start of their seizures. The patients (five women, two men) were aged 36-58. Three of seven patients described the exact nature of their auras only many years after their appearance, when the epilepsy diagnostic procedure became more intensive due to drug resistance. Moreover, one patient even refused any new therapeutical options due to the reportedly positive role of the orgasmic aura in her life. All of our patients had temporal lobe epilepsy. The clinical picture, EEG, MRI or SPECT findings suggested a right temporal epileptic focus in six patients, while in one patient the epileptogenic region was localised in the left temporal lobe. In the latter case, the left hemisphere was speech-dominant, while in the other cases no Wada tests were done. Our results confirm that orgasmic aura could be considered as an ictal lateralising sign to the right hemisphere, however, it has no 100% lateralising value.

Adult↗
PubMed2004

Intentional seizure interruption may decrease the seizure frequency in drug-resistant temporal lobe epilepsy.

We investigated the nature of preictal subjective phenomena and whether they had any effect on the seizure frequency in 95 adult patients with medial temporal lobe epilepsy. Seventy-three (77%) patients indicated that they experienced seizure-provoking factors. Ten patients (11%) had prodromas independent of auras, while auras occurred in 89%. Forty-four patients (46%) reported that that they had tried to stop their seizures in the presence of prodroma or aura and this action had resulted in success at least once. Twenty-one patients (22%) regularly tried to stop their seizures because this effort was often successful according to their interpretation. Patients who reported that they could frequently inhibit their seizures had 1.8 +/- 1.6 seizures/month, a significantly lower mean seizure frequency than those 74 patients who did not do it regularly (4.6 +/- 4.8 seizures/month, P<0.001). Patients who reported regular experience in inhibiting intentionally their seizures more often had affective (P=0.05) and vertiginous auras (P<0.01) as well as isolated auras (P<0.05). Patients who experienced provoking factors showed the same seizure frequency as those who did not. Our results suggest that intentional seizure inhibition had an impact on the severity of drug-resistant epilepsy.

Adolescent↗
PubMed2002

Orgasmic aura originates from the right hemisphere.

The authors present a patient with right mesiotemporal epileptogenic region who experienced orgasmic epileptic aura. Twenty-two similar published cases were also evaluated. Among 15 patients with unilateral EEG foci, 13 (87%) had right and 2 (13%) had left focus. All of the nine patients who had sufficient data on ictal onset area had right-sided seizure onset. The authors suggest that orgasmic aura is an ictal lateralizing sign to the right hemisphere.

Adult↗
PubMed2001

Extended dynamic clamp: controlling up to four neurons using a single desktop computer and interface.

The dynamic clamp protocol allows an experimenter to simulate the presence of membrane conductances in, and synaptic connections between, biological neurons. Existing protocols and commercial ADC/DAC boards provide ready control in and between < or =2 neurons. Control at >2 sites is desirable when studying neural circuits with serial or ring connectivity. Here, we describe how to extend dynamic clamp control to four neurons and their associated synaptic interactions, using a single IBM-compatible PC, an ADC/DAC interface with two analog outputs, and an additional demultiplexing circuit. A specific C++ program, DYNCLAMP4, implements these procedures in a Windows environment, allowing one to change parameters while the dynamic clamp is running. Computational efficiency is increased by varying the duration of the input-output cycle. The program simulates < or =8 Hodgkin-Huxley-type conductances and < or =18 (chemical and/or electrical) synapses in < or =4 neurons and runs at a minimum update rate of 5 kHz on a 450 MHz CPU. (Increased speed is possible in a two-neuron version that does not need auxiliary circuitry). Using identified neurons of the crustacean stomatogastric ganglion, we illustrate on-line parameter modification and the construction of three-member synaptic rings.

Algorithms↗
PubMed2001

Nonlinear behavior of sinusoidally forced pyloric pacemaker neurons.

Periodic current forcing was used to investigate the intrinsic dynamics of a small group of electrically coupled neurons in the pyloric central pattern generator (CPG) of the lobster. This group contains three neurons, namely the two pyloric dilator (PD) motoneurons and the anterior burster (AB) interneuron. Intracellular current injection, using sinusoidal waveforms of varying amplitude and frequency, was applied in three configurations of the pacemaker neurons: 1) the complete pacemaker group, 2) the two PDs without the AB, and 3) the AB neuron isolated from the PDs. Depending on the frequency and amplitude of the injected current, the intact pacemaker group exhibited a wide variety of nonlinear behaviors, including synchronization to the forcing, quasiperiodicity, and complex dynamics. In contrast, a single, broad 1:1 entrainment zone characterized the response of the PD neurons when isolated from the main pacemaker neuron AB. The isolated AB responded to periodic forcing in a manner similar to the complete pacemaker group, but with wider zones of synchronization. We have built an analog electronic circuit as an implementation of a modified Hindmarsh-Rose model for simulating the membrane potential activity of pyloric neurons. We subjected this electronic model neuron to the same periodic forcing as used in the biological experiments. This four-dimensional electronic model neuron reproduced the autonomous oscillatory firing patterns of biological pyloric pacemaker neurons, and it expressed the same stationary nonlinear responses to periodic forcing as its biological counterparts. This adds to our confidence in the model. These results strongly support the idea that the intact pyloric pacemaker group acts as a uniform low-dimensional deterministic nonlinear oscillator, and the regular pyloric oscillation is the outcome of cooperative behavior of strongly coupled neurons, having different dynamical and biophysical properties when isolated.

Action Potentials↗
PubMed2000

Synchronous behavior of two coupled electronic neurons.

We report on experimental studies of synchronization phenomena in a pair of analog electronic neurons (ENs). The ENs were designed to reproduce the observed membrane voltage oscillations of isolated biological neurons from the stomatogastric ganglion of the California spiny lobster Panulirus interruptus. The ENs are simple analog circuits which integrate four-dimensional differential equations representing fast and slow subcellular mechanisms that produce the characteristic regular/chaotic spiking-bursting behavior of these cells. In this paper we study their dynamical behavior as we couple them in the same configurations as we have done for their counterpart biological neurons. The interconnections we use for these neural oscillators are both direct electrical connections and excitatory and inhibitory chemical connections: each realized by analog circuitry and suggested by biological examples. We provide here quantitative evidence that the ENs and the biological neurons behave similarly when coupled in the same manner. They each display well defined bifurcations in their mutual synchronization and regularization. We report briefly on an experiment on coupled biological neurons and four-dimensional ENs, which provides further ground for testing the validity of our numerical and electronic models of individual neural behavior. Our experiments as a whole present interesting new examples of regularization and synchronization in coupled nonlinear oscillators.

Animals↗
PubMed2000

Analysis and modulation of spike trains and oscillations in identified neural network of Lymnaea stagnalis L.

Identified neurons and members of functionally characterized clusters of the central nervous system of Lymnaea stagnalis L. were studied. Long-term spike trains (10-100 min) were collected using current clamp method. Firing patterns were analyzed by several mathematical tools e.g.: spike density function (SDF), interspike interval (ISI), Fourier-transform. Both the spike trains and oscillation of firing were modulated by 5HT (2 x 10(-5) M) and mu-opioid peptides (10(-5) M). Co-application of 5HT (2 x 10(-5) M) and DAGO (10(-5) M) turned the firing of the neurons (RPeD1 and A cells) opposite to the running pattern and eliminated the 0.3 Hz oscillation causing a new slow periodicity (0.1-0.05 Hz).

Action Potentials↗
PubMed2000

Nonlinear activity of identified Lymnaea neurons.

Two long-lasting discharges of action potentials were recorded from a buccal cell of the pond snail, respectively, before and after superfusing the preparation with low-calcium solution. The corresponding sequences of interspike intervals were then analysed by the nonlinear prediction methods. The results yield evidence of a small but clear nonlinearity only in the second of analysed tachograms. This finding is evaluated and discussed.

Action Potentials↗
PubMed1999

Distinct responses of osphradial neurons to chemical stimuli and neurotransmitters in Lymnaea stagnalis L.

1. In Lymnaea stagnalis L. (Pulmonata, Basommatophora) the neurons in the osphradium were visualized by staining through the inner right parietal nerve by 5,6-carboxyfluorescein (5,6-CF). Three types of neurons were identified: three large ganglionic cells (GC1-3; 80-100 microns), the small putative sensory neurons (SC; 20 microns) and very small sensory cells (3-5 microns). 2. The ganglionic and putative sensory neurons were investigated by whole cell patch-clamp method in current-clamp condition. The three giant ganglionic neurons (GC1-3) located closely to the root of osphradial nerve, had a membrane potential (MP) between -30 and -70 mV and showed tonic or bursting activities. The small putative sensory cells (SCs) scattered throughout the osphradial ganglion, possessed a MP between -25 and -55 mV and showed an irregular firing pattern with membrane oscillations. At resting MP the GC1-3 cells were depolarized and increased the frequency of their firing, while the SCs were hyperpolarized and inhibited by NaCl (10(-2) M) and L-aspartate (10(-5) M) applied to the osphradium. 3. 5-Hydroxytryptamine (5HT, 10(-6) M), gamma-aminobutyric acid (GABA; 10(-6) M) and the GABAB agonist baclofen (10(-6) M) depolarized the neurons GC1-3 and increased their firing frequency. In contrast, on the GC1-3 neurons, acetylcholine (Ach; 10(-6) M) and FMRFamide (10(-6) M) caused hyperpolarization and cessation of the firing activity. The 5HT effect was blocked by mianserin (10(-6) M) but picrotoxin (10(-5) M) failed to block the GABA-induced effect on the GC1-3 cells. 4. The small putative sensory neurons (SCs) were excited by Ach (10(-6) M) and 5HT (10(-6) M) but were inhibited by GABA (10(-6) M). FMRFamide (10(-6) M) had a biphasic response. The Ach effect was blocked by hexamethonium (10(-6) M) and tetraethylammonium (10(-6) M), indicating the involvement of nicotinic cholinergic receptors. 5. The distinct responses of the two populations of osphradial neurons to chemical stimuli and neurotransmitters suggest that they can differently perceive signals from environment and hemolymph.

Acetylcholine↗
PubMed1999

[The role of plastic shock absorbers in dental implantation].

The mechanical behaviour of different plastics (PE, PP, PI, PA, ABS, POM) was examined by static and dynamic loading. Detection of microdeformations and photoelastic stress analysis served as the examination method. According to the results, polyethylene is unsuitable, however the other plastics, with clauses, are suitable as shock absorbers. Apart from the mechanical investigation photoelastic stress analysis also revealed the benefit of osseointegration in force transmission to the bone.

Dental Implants↗
PubMed1999

Influence of HgCl2 on the osphradial multisensory system of Lymnaea stagnalis L.

The osphradial multisensory system of Lymnaea stagnalis L. (Pulmonata, Basommatophora) was used to demonstrate the modulation of chemosensory information both at periphery and central nervous system (CNS) following heavy metal treatments. A semi-intact preparation including osphradium, CNS and the right inner parietal nerve (r.i.p.n.) connecting them was used to record both extracellular activity of nerve and intracellular activity of central neurons receiving information from osphradium. The ion currents of osphradium were recorded using patch-clamp method. The changes in nerve and neuronal activity were expressed by averaging of firing frequency and interspike intervals. The chemosensory function of osphradium was shown by application of L-aspartate, urea, saccharose and stagnant water to its surface. The central neurons reacting to the stimulation ofosphradium were located to visceral, right parietal, pedal and cerebral ganglia of Lymnaea. Both the acute and chronic treatments with HgCl2 damaged the sensory function of osphradium traced on the flow of information from periphery to central neurons. At the same time, mercury chloride modified the synaptic connections of respiratory pattern generators as well as the Ca- and K-dependent ion currents of osphradial neurons. The results proved the multisensory role of osphradium sensing the alterations in the environment and its usefulness in monitoring the effects of pollutants at various level of regulation from chemosensory epithelium to CNS.

Animals↗
PubMed1999

Periodic and oscillatory firing patterns in identified nerve cells of Lymnaea stagnalis L.

Firing patterns in identified neurons of Lymnaea stagnalis L. were analyzed by various mathematical methods including spike density function (SDF), interspike-interval histograms (ISI), Fourier transform and correlation analysis. Input-3 (IP3) events observed in most of the neurons of the respiratory regulatory system caused prominent changes in the firing frequency of the cells. Similarly, quasiperiodic firing patterns were observed in the neurons of buccal ganglia controlling feeding behavior. Apart from the known periodic patterns a fine oscillation of firing rate was observed in a large number of neurons in the visceral and parietal ganglia. The frequency of this oscillation varied between 0.2 and 0.4 Hz. The most obvious oscillatory patterns were found in the A-cells presumably resulted by periodically appearing synaptic excitation. Moderate intracellular hyperpolarizing current injection, low-Ca/high-Mg saline and application of d-tubocurarine failed to abolish the slow oscillations. Application of Ca-channel blocker cadmium, however, completely eliminated the oscillation in a reversible manner.

Action Potentials↗
PubMed1998

[Experience with percutaneous endoscopic gastrostomy in the nutrition of a patient with 3rd and 4th degree facial burns].

Recovery after thermal injury depends in great proportion on nutrition. A major problem is accounted in patients with facial burn, because they can not be nourished per vias naturales. Eliminating disadvantages of parenteral nutrition, but utilizing the advantages of enteral nutrition, we have tried a new method of treatment in a patient whose case is presented. On the second day after injury a percutaneous endoscopic gastrostomy was made. On the 7th day after injury and on the 4th day from the beginning of enteral nutrition complete intake of food and liquid was assured through the percutaneous endoscopic gastrostoma. We had no complication related to the gastrostoma. Nutrition through the percutaneous endoscopic gastrostoma at our patient provided a "natural" route to assure liquid, electrolite and energy balance, prevented atrophy of intestinal mucosa and its metabolic and immunologic complications. With the use of percutaneous endoscopic gastrostoma the possible complications of central line catheter were omitted. Our opinion is that percutaneous endoscopic gastrostomy is a safe and effective method for the clinical nutrition of burned patients.

Accidental Falls↗
PubMed1997

Opposite effects of interleukin-2 and interleukin-4 on GABA-induced inward currents of dialysed Lymnaea neurons.

1. The effects of interleukin-2 (rhIL-2) and interleukin-4 (rhIL-4) were investigated on gamma-aminobutyric acid (GABA)-induced inward currents on isolated, identified neurons of Lymnaea stagnalis L. (Mollusca, Gastropoda) by using a concentration clamp technique. 2. It was shown that the interleukins modified the GABA-induced inward current in an opposite direction: rhIL-2 (2-100 U/ml) decreased the peak value of IGABA in a dose-dependent manner, whereas rhIL-4 (0.2-100 U/ml), on the contrary, potentiated it. Both types of modulation were partially or fully reversible. 3. The reversal potential of IGABA was not shifted by these cytokines. 4. The time-to-peak value and inactivation time constant of the gamma-aminobutyric acid (GABA)-induced current was decreased by rhIL-4. The modulatory effect of rhIL-4 was eliminated after conjugation of this cytokine with its antibody. 5. It appears that cytokines could play a role in regulating the neural excitability through GABA-erg mechanisms.

Animals↗
PubMed1997

Effects of inorganic mercury and methylmercury on the ionic currents of cultured rat hippocampal neurons.

1. The effects of inorganic Hg2+ and methylmercuric chloride in the ionic currents of cultured hippocampal neurons were studied and compared. We examined the effects of acute exposure to the two forms of mercury on the properties of voltage-activated Ca2+ and Na+ currents and N-methyl-D-aspartate (NMDA)-induced currents. 2. High-voltage activated Ca2+ currents (L type) were inhibited by both compounds at low micromolar concentrations in an irreversible manner. Mercuric chloride was five times as potent as methylmercury in blocking L-channels. 3. Both compounds caused a transient increase in the low-voltage activated (T-type) currents at low concentrations (1 microM) but blocked at higher concentrations and with longer periods of time. 4. Inorganic mercury blockade was partially use dependent, but that by methylmercury was not. There was no effect of exposure of either form of mercury on the I-V characteristics of Ca2+ currents. 5. Na(+)- and NMDA-induced currents were essentially unaffected by either mercury compound, showing only a delayed nonspecific effect at a time of overall damage of the membrane. 6. We conclude that both mercury compounds show a relatively selective blockade of Ca2+ currents, but inorganic mercury is more potent than methylmercury.

Animals↗
PubMed1996

Characterization of the GABA response on identified dialysed Lymnaea neurons.

1. The effect of gamma-aminobutyric acid has been studied on identified, internally perfused dialysed neurons of Lymnaea stagnalis L. (Pulmonata, Basommatophora). It was shown that: On the majority of neurons GABA (10(-8)-10(-3) M) depolarized the membrane with a decrease in input resistance and activated a Cl- dependent inward current with -20 +/- 4 mV E(GABA). In some cells, the outward current with -67 +/- 8 mV E(GABA) was also recorded. 2. The GABA-induced inward current was fast (1.5 +/- 0.3 sec, n = 4) or slow (3.2 +/- 0.2 sec, n = 3) peaking in a voltage-independent manner. The inactivation phase could be fitted by one or two exponentials characterized with fast (tau = 0.7 sec) and slow (tau = 3.6 sec) time constants. The outward current component was slow and activated at more positive Vh(-30-20 mV). 3. The agonist effects (GABA and muscimol) indicated the involvement of GABA(A) receptors and Cl-permeability changes in activating inward current. Picrotoxin (10(-5)-10(-4) M) and Cd2+ completely inhibited the GABA-activated inward current also affecting E(GABA). Furosemide was without effect on the peak value of GABA-induced inward current, but slightly modified the slope of inactivation. 4. High concentrations of Ca-ions and their substitution with Ba-ions in extracellular saline failed to alter the GABA-induced inward current. However, omission of Cl-ions from extracellular media shifted E(GABA) to the right by 18 +/- 8 mV (n = 4). 5. Omission of Cl-ions from intracellular saline led to inhibition of the fast component of GABA-induced inward current. Full recovery followed readdition of Cl-ions. 6. The results are in agreement with the data obtained on cloned Lymnaea GABA receptors.

Animals↗