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Biomedical subjects

Z Horváth

Publications and source records attributed to Z Horváth.

At least 19 recordsLinked to original sources
PubMed1992

High-frequency network oscillation in the hippocampus.

Pyramidal cells in the CA1 hippocampal region displayed transient network oscillations (200 hertz) during behavioral immobility, consummatory behaviors, and slow-wave sleep. Simultaneous, multisite recordings revealed temporal and spatial coherence of neuronal activity during population oscillations. Participating pyramidal cells discharged at a rate lower than the frequency of the population oscillation, and their action potentials were phase locked to the negative phase of the simultaneously recorded oscillatory field potentials. In contrast, interneurons discharged at population frequency during the field oscillations. Thus, synchronous output of cooperating CA1 pyramidal cells may serve to induce synaptic enhancement in target structures of the hippocampus.

Action Potentials↗
PubMed1992

Light microscopic response of neuronal somata, dendrites and axons to post-mortem concussive head injury.

Forty anesthetized rats were cooled below 3 degrees C by 30-min transcardial perfusion of chilled physiological saline before a concussive head injury. The animals were then perfusion-fixed with a buffered formaldehyde-glutaraldehyde solution. Another forty rats were fixed by 30-min transcardial perfusion of the same fixative before a similar concussive head injury. In brain sections of both groups of animals a new silver method stained, in a Golgi-like fashion, a number of neurons and long axonal segments scattered among unstained ones. The similarity between these findings and those obtained following in vivo concussive head injuries described in accompanying papers suggests that the formation of traumatically induced argyrophilic neuronal damage is independent of metabolic processes, i.e., it may be a primary morphopathological process.

Animals↗
PubMed1992

Time course of changes in long-term potentiation of synaptic transmission following subcortical deafferentation on the rat hippocampus.

Brief tetanic stimulation potentiates synaptic transmission both in the CA1 and dentate area of slices cut from normal rats. This long-term potentiation (LTP) was assayed in slices made at various times from rats subjected to complete bilateral sectioning of all subcortical afferents which enter the hippocampus. Over about one week survival time, LTP is present in the CA1 region of all and also in the fascia dentata of about 50% of slices. We found no signs of LTP in the dentate area of slices cut over 8 weeks after deafferentation, while the responses were clearly potentiated in the CA1 area of the same slices. Four week was the longest period when a somewhat modified version of LTP could be produced in the subcortically deafferented dentate area. The results confirm previous reports that subcortical afferents mediate some unknown factors essential for maintenance of long-term plasticity of intrinsic synapses in the fascia dentata. This unidentified, perhaps trophic influence diminishes in about 4 weeks after severing the subcortical fibers. In contrast, maintenance of subcortical inputs are apparently not required for the LTP in the intrinsic CA1 synapses.

Afferent Pathways↗
PubMed1992

DNASK--a new image analysis module for TV image cytometry.

The DNASK is a PC-based image analysis module for quantitative cytological and histological examinations on Feulgen-Schiff preparations. The module consists of a frame grabber, a CCD black and white video camera and the DNASK software package which can be incorporated in an IBM compatible PC-AT joining to a standard pathological research photo microscope. The use of 386 IBM AT systems leads to significant decrease of the measurement's time. Mono- or color VGA graphics card should be used. The resolution of the images is 512 x 512 pixels and 256 gray values. The image caption is made in less than 0.5 second, the measurement of a cell nuclei (18 parameters) takes less, than 5 seconds (IBM AT 286). The camera is a standard CCD one. The microscope should be a good quality, modern microscope with built-in light source, however, the application of voltage stabiliser is strongly recommended. The software is able to measure the parameters mostly used and suggested in the international literature: 15 morpho- and densitometric parameters of the cell nuclei 6 DNA histogram parameters of the measured case, like DNA Index, 2c deviation Index, 5c exceeding rate, G1-S-G2 phase fraction ratio. The system supports the grouping of the measured cases and at the end of a study results of the single measurements can be collected and summarized in an ASCII file, which is readable by major statistical programpackages. The DNASK has a special graphical user interface for the control of the program.

Algorithms↗
PubMed1991

Hippocampal grafts into the intact brain induce epileptic patterns.

Spontaneous hippocampal EEG activity and evoked field potentials were investigated in intact rats and in animals with fetal hippocampal grafts. Pieces of hippocampal grafts, derived from 15- to 16-day-old fetuses, were used to prepare cell suspensions and grafted directly into the intact hippocampus. Control animals received suspension grafts of the cerebellum derived from fetuses of identical age. Host hippocampal electrical patterns were monitored with chronic single electrodes or with a 16-microelectrode probe from 7 to 10 months after grafting. In contrast to previously reported high survival rates of fetal grafts in studies with damage to the host brain prior to grafting, survival of both hippocampal (60%) and cerebellar grafts (20%) was very poor in the intact hippocampus. In animals with cerebellar transplants or without surviving grafted neurons the electrical activity of the host hippocampus was indistinguishable from normal controls. In rats with hippocampal grafts short duration, large amplitude EEG spikes (up to 10 mV) were recorded, predominantly during immobility. When the EEG spikes (putative interictal spikes) were of large amplitude and contained population spikes, test evoked responses delivered to the perforant path were suppressed after the spontaneous events. In contrast, evoked responses were facilitated by interictal spikes without population spikes. The threshold of electrically induced afterdischarges did not differ significantly between groups of intact rats and animals with or without hippocampal grafts. However, in three rats with hippocampal grafts the evoked afterdischarges were associated with behavioral seizures. In two of these rats spontaneously occurring seizures were also observed. Synaptophysin-immunoreactivity demonstrated growth of the host mossy fibers into the graft.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholinesterase↗
PubMed1991

Emergence and propagation of interictal spikes in the subcortically denervated hippocampus.

Spontaneous and evoked field potentials and cellular discharges of the subcortically denervated dorsal hippocampus were studied by multisite recordings in the freely behaving rat. Characteristic short-duration (< 100 ms), large-amplitude (up to 10 mV) transients, termed interictal spikes (IIS), were seen after fimbria-fornix (FF) lesion. Both pyramidal cells and putative interneurons fired maximally during IIS, with some interneurons sustaining long bursts (up to 400 ms) of high-frequency discharges (400-600 Hz) after the IIS. The speed of propagation of IIS along the longitudinal axis of the hippocampus varied from 0.2 m/s to > 3 m/s. The majority of IIS (type 1) could be accounted for by an enhanced activity of the intrahippocampal associational systems; a second class of IIS (type 2) had positive polarities in the stratum radiatum of CA1 and CA3 and propagated very rapidly (> 1.5 m/s). The authors propose that type 2 IIS reflect somatic depolarization and discharge of pyramidal neurons due to nonsynaptic (probably ephaptic) effects. Ephaptic interactions may also explain the longitudinal propagation of IIS at speeds higher than the conduction velocities (0.5 m/s) of hippocampal fiber systems. IIS emerged during the first 3 weeks after fimbria-fornix lesion, their incidence reaching a plateau of 2/min thereafter. During the same time period, paired-pulse suppression increased in the dentate gyrus. The amplitude of test responses to angular bundle stimulation was potentiated by small-amplitude IIS but suppressed by large-amplitude IIS. The incidence of IIS was significantly suppressed during walking relative to standing still. Tetanic stimulation of the angular bundle or handling-induced stress resulted in a 10- to 20-fold increase in the incidence of IIS that lasted for about 30 minutes. There was a negative correlation between evoked field PSP slope and population spike amplitude in the dentate gyrus of FF-lesioned rats; this correlation was positive in intact rats. The authors attribute the above pathophysiological changes to sprouting of both excitatory and inhibitory GABAergic pathways as a result of denervation of the intrahippocampal circuitry. They hypothesize that the majority of the observed physiological alterations can be traced to a weakening of feedforward inhibition coupled with an enhancement of feedback inhibition and excitation.

Animals↗
PubMed1991

Neomorph and leaf differentiation as alternative morphogenetic pathways in soybean tissue culture.

Somatic embryogenesis and organogenesis were induced on immature cotyledons of different soybean cultivars. The anatomical investigation of morphogenesis proved neomorph differentiation instead of somatic embryos, and leaf formation instead of shoot development. While normal embryos were induced in 0-3.1% of the explants, neomorphs developed at a much higher rate i.e. in 10.5-78.9% depending on the genotype. Likewise organogenesis preferably followed the pathway of leaflet development (3.1-26.3%) than that of shoot tip formation (0-2.6%). Low plant regeneration frequency of soybean can partly be explained with these two alternative abortive pathways of morphogenesis probably induced with higher frequency than the normal pathways by the generally used in vitro methods.

Culture Techniques↗
PubMed1990

Long-term potentiation in slices from subcortically deafferented hippocampi.

Long-term potentiation (LTP) can be initiated in CA1, but not in the dentate, region of slices from rats with bilateral subcortical deafferentation at 8 week survival time. At about one week survival time, LTP is present in the CA1 region of all and also in the dentate of about 50% of slices. The results suggest that subcortical cholinergic and catecholaminergic inputs are not required for the LTP in the CA1 area of the rat hippocampus.

Afferent Pathways↗
PubMed1988

Perforant path activation of the hippocampus: spatial distribution, effects of urethane and atropine.

Spatial distribution of field responses evoked by perforant path stimulation were studied in the hippocampus of both anaesthetized and drug-free rats. Simultaneous recordings with an array of 4 electrodes allowed us to construct a 2-dimensional map of the evoked field potentials. In addition, we examined the effects of atropine-SO4 and urethane on the amplitude of the dentate response. Trisynaptic activation of the CA1 region occurred regularly in the drug-free rat while CA1 population spikes were rarely seen in the anaesthetized animal. The latency of the CA1 population spike was shortest at the fimbrial side and increased gradually towards the subicular side. In the dentate gyrus atropine increased the amplitude of the population spike. We suggest that atropine may interfere with the septo-hippocampal feed-forward inhibition, and urethane may decrease the effectiveness of the perforant path-granule cell synapse, as well as the intrahippocampal excitatory circuit.

Animals↗
PubMed1985

Oxytocin and a C-terminal derivative (Z-prolyl-D-leucine) attenuate tolerance to and dependence on morphine and interact with dopaminergic neurotransmission in the mouse brain.

The effects of oxytocin (OXT) and of dipeptides derived from the C-terminal portion of oxytocin (Z-prolyl-leucine and Z-prolyl-D-leucine) on the development of acute and chronic tolerance to, and dependence on morphine were tested in the mouse. Oxytocin and the dipeptides attenuated the development of acute and chronic tolerance to the antinociceptive effect of morphine and delayed the onset of the naloxone-precipitated withdrawal syndrome. Both oxytocin and Z-prolyl-D-leucine affected drug-induced behavioural responses related to dopamine (DA) in the brain. Thus, oxytocin potentiated the hypermotility induced by a large dose of apomorphine and decreased the supersensitivity of the DA receptors. Small doses of Z-prolyl-D-leucine inhibited the hypomotility elicited by a small dose of apomorphine and potentiated the hyperactivity induced by amphetamine. The data indicate that both oxytocin and Z-prolyl-D-leucine affect tolerance to and dependence on morphine. While oxytocin interacts mainly with postsynaptic DA-ergic neuronal elements, the dipeptide primarily affects DA-ergic neurotransmission at the presynaptic level.

Animals↗
PubMed1985

Effect of metal ions on the aspartate transaminase (E.C.2.6.1.1.) activity in tobacco tissue culture.

Aspartate transaminase enzyme was prepared from tobacco tissue cultures. Effect of 13 different metal ions on the enzyme activity was preliminarily studied. The enzyme activity was inhibited by five ions, namely Cd2+, Hg2+, Zn2+, Cu2+, and Ag+. None of the ions investigated enhanced the activity. Fe2+ caused an apparent activity increase in the reaction mixture. Pyridoxal-phosphate enhanced this effect of the Fe2+.

Aspartate Aminotransferases↗
PubMed1985

Transplantation of cerebral actinomycosis simulating malignant brain tumor into nude mice. Report of a case.

A case of actinomycotic brain abscess simulating malignant brain tumor is presented. Diagnosis was made by histological examination of the operative specimen and of the organs of xenotransplanted Nude mice. The patient survived 3 months after the operation. None of the characteristic organisms could be detected microscopically at the autopsy in the brain and the lung. Xenotransplantation into Nude mice may be a useful method for the relatively quick identification of the causative agent in cases suspected of actinomycosis.

Actinomycosis↗
PubMed1985

Campylobacter strains isolated from slaughtered chickens: their sensitivity to antibiotics and resistance to erythromycin.

Antibiograms for 304 Campylobacter strains isolated in Csongrád county from slaughtered chickens in the years 1981 to 1983 were determined with the disk-agar diffusion method. The isolates, originating from two poultry-processing plants and two canteen kitchens proved to be sensitive to nalidixic acid, chloramphenicol, gentamicin and nitrofurantoin and resistant to penicillin. The antibiogram depended on the source of samples and, to a higher degree, on the year of sampling. The frequency of strains resistant to erythromycin was 5.7% in 1981 and 39.8% in 1983; for the resistant strains the minimum inhibiting concentration was greater than 250 micrograms erythromycin per ml. In the same periods 25.0% and 32.8% of the isolates were resistant to tetracycline and 23.3% and 49.2% to lincomycin, respectively. Simultaneous resistance to tetracycline, lincomycin and erythromycin occurred in 16.4% of the isolates.

Animals↗