Biomedical subjects

F Stastný

Publications and source records attributed to F Stastný.

At least 19 recordsLinked to original sources

PubMed2006

Does neonatal brain ischemia induce schizophrenia-like behavior in young adult rats?

Perinatal cerebral hypoxia represents a major cause of obstetric complications and the resulting transient oxygen deficiency might belong to early risk factors for schizophrenia. The aim of this study was to evaluate possible long-term behavioral changes induced by one hour of continuous bilateral common carotid artery occlusion in 12-day-old male rats. Post-ischemic behavioral disturbances were evaluated in social (play) behavior on postnatal day 22 (PND 22), open field test (PND 35 and 50) and prepulse inhibition of the acoustic startle reflex (PND 50). Transient ischemia in neonatal rats was not significantly altered in social dyadic interactions evaluated in pre-weaning pups, but resulted in enhanced locomotor activity in pubertal rats (PND 35) and impaired prepulse inhibition of the startle reflex in post-pubertal males (PND 50). These behavioral alterations suggest that perinatal hypoxic/ischemic insults may represent a risk factor for later manifestation of specific features relevant to schizophrenia in predisposed individuals.

Acoustic Stimulation↗

PubMed2005

The influence of interleukin-1beta on gamma-glutamyl transpepidase activity in rat hippocampus.

Brain infections as well as peripheral challenges to the immune system lead to an increased production of interleukin-1beta (IL-1beta), a cytokine involved in leukocyte-mediated breakdown of the blood-brain barrier. The effects of IL-1beta have been reported to depend on whether the route of administration is systemic or intracerebral. Using 50-day-old male rats, we compared the effects of IL-1beta on brain gamma-glutamyl transpeptidase (GGT; an enzymatic marker of brain capillary endothelium) at 2, 24 and 96 h after either an intravenous (i.v.) injection of 5 microg IL-1beta or an intracerebroventricular (i.c.v. - lateral ventricle) infusion of 50 ng IL-1beta. When the i.v. route was used, the GGT activity underwent small but significant changes; decreasing in the hippocampus 2 h after the i.v. injection, increasing 24 h later and returning to control levels at 96 h. No significant changes in the hippocampal GGT activity were observed at 2 and 24 h following the i.c.v. infusion. The GGT activity in the hypothalamus remained unchanged regardless of the route of IL-1beta administrations. Similar changes in GGT activity were revealed histochemically. The labeling was found mainly in the capillary bed, the changes being most evident in the hippocampal stratum radiatum and stratum lacunosum-moleculare. A transient increase in GGT activity at 24 h, together with a less sharp delineation of GGT-stained vessels, may reflect IL-1beta induced increased turnover of glutathione and/or oxidative stress, that may in turn, be related to altered permeability of the blood-brain barrier in some neurological and mental disorders, including schizophrenia.

Animals↗

PubMed2002

Nitric oxide synthase inhibition and glutamate binding in quinolinate-lesioned rat hippocampus.

The effect of lesions induced by bilateral intracerebroventricular (i.c.v.) injection of quinolinate (250 nmol of QUIN/ventricle), a selective N-methyl-D-aspartate (NMDA) receptor agonist, on [3H]glutamate ([3H]Glu) binding to the main types of both ionotropic and metabotropic glutamate receptors (iGluR and mGluR) was investigated in synaptic membrane preparations from the hippocampi of 50-day-old rats. The membranes from QUIN injured brains revealed significantly lowered binding in iGluR (by 31%) as well as in mGluR (by 22%) as compared to the controls. Using selected glutamate receptor agonists as displacers of [3H]Glu binding we found that both the NMDA-subtype of iGluR and group I of mGluR are involved in this decrease of binding. Suppression of nitric oxide (NO) production by N(G)-nitro-L-arginine (50 nmol of NARG/ventricle) or the increase of NO generation by 3-morpholinylsydnoneimine (5 nmol of SIN-1/ventricle) failed to alter [3H]Glu or [3H]CPP (3-((D)-2-carboxypiperazin-4-yl)-[1,2-(3)H]-propyl-1-phosphonic acid; NMDA-antagonist) binding declines caused by QUIN-lesions. Thus, our findings indicate that both the NMDA-subtype of iGluR and group I of mGluR are susceptible to the QUIN-induced neurodegeneration in the rat hippocampus. However, the inhibition of NO synthesis did not reveal any protective action in the QUIN-evoked, NMDA-receptor mediated decrease of [3H]Glu binding. Therefore, the additional mechanisms of QUIN action, different from direct NMDA receptor activation/NO production (e.g. lipid peroxidation induced by QUIN-Fe-complexes) cannot be excluded.

Animals↗

PubMed1997

Specific [3H]glutamate binding in the cerebral cortex and hippocampus of rats during development: effect of homocysteine-induced seizures.

Specific [3H]glutamate binding to synaptic membranes from the cerebral cortex and hippocampus of 7-, 12- and 18-day-old rats was examined, both in control animals and during seizures induced by homocysteine. In the cerebral cortex a transient peak of glutamate binding was observed in 7-day-old group, whereas in the hippocampus it occurred in 12-day-old animals. Total specific [3H]glutamate binding was not influenced by preceding seizure activity in either of the age groups and both the studied regions. NMDA- and QA-sensitive glutamate bindings represent the highest portion of the total binding. Moreover, NMDA-sensitive binding in the cerebral cortex of 7-day-old rats is significantly higher as compared to the two more mature groups. The proportion of individual receptor subtypes on total binding in each age group was not influenced by preceding seizure activity. However, NMDA-sensitive binding in the hippocampus of 12-day-old rats, sacrificed during homocysteine-induced seizures, was significantly increased as compared to corresponding controls. In contrast to the effect of NMDA, AMPA, kainate and quisqualate which displaced to a different extent [3H]glutamate binding, homocysteine had no effect when added to membrane preparations. Similarly, [3H]CPP and [3H]AMPA bindings were not affected in the presence of homocysteine. It thus seems unlikely that homocysteine is an effective agonist for conventional ionotropic glutamate receptors. Its potential activity at some of the modulatory sites at the NMDA receptor channel complex or at metabotropic receptors has to be clarified in further experiments.

Aging↗

PubMed1997

The effect of quinolinate on rat brain lipid peroxidation is dependent on iron.

Quinolinate, an endogenous excitotoxic metabolite of tryptophan with affinity to the N-methyl-D-aspartate type of glutamate receptor, is known as a stimulator of lipid peroxidation in vitro [Neurochem. Res. (1991) 16, 1139-1143]. To analyse the mechanism of this quinolinate toxicity we used the thiobarbituric acid test to measure malondialdehyde in homogenates of rat cerebral hemispheres incubated in air at 37 degrees C for 30 min in the presence of 0.015-15.0 mM quinolinate, endogenous iron or 0.5-2.0 microM FeSO4 and with or without 250 microM ascorbate. Quinolinate in the concentrations of 0.15-2.5 mM stimulated lipid peroxidation in the homogenates in the presence of 0.5-2.0 microM Fe2+. However, quinolinate concentrations higher than 3.0 mM inhibited the lipid peroxidation at all the tested concentrations of iron. In the presence of a potent iron chelator (10 microM deferoxamine) quinolinate completely failed to induce lipid peroxidation in rat brain homogenates. Spectral analysis revealed that quinolinate is able to form a complex with Fe2+. The results suggest that quinolinate does not have a direct peroxidative effect, but that it modulates lipid peroxidation via its interaction with iron.

Animals↗

PubMed1996

Relationship between kinetic properties of gamma-glutamyl transpeptidase and the structure of its saccharide moiety.

Gamma-glutamyl transpeptidase (EC 2.3.2.2; GGT) is a plasma-membrane bound glycoenzyme, the saccharide moiety of which is rather heterogeneous and organ specific. It has been stated that GGT catalyses three types of reactions, i.e., hydrolysis, transpeptidation and autotranspeptidation. The initial velocity equation, involving all these reactions, is shown in the present report. Mathematical analysis of the equation resulting in a definition of the constant of half saturation (Khs). The value of Khs was used for characterization of kinetics of GGT from rat organs differing in the structure of GGT oligosaccharide chains. No significant organ differences were found, when the Khs values of GGT from the brain, kidney and pancreas equalled 0.61 mM, 0.68 mM and 0.68, respectively. On the contrary, when two different glycoforms of GGT from the pancreas were compared, distinct values of Khs were obtained (1.43 mM and 0.67 mM, respectively). It is therefore being suggested that the saccharide chains of GGT are involved in its kinetic properties. However, this effect is masked when the enzyme, non-fractionated into glycoforms, is analysed, even though the saccharide moiety is specific for the organ studied.

Animals↗

PubMed1996

Analysis of kinetic properties of gamma-glutamyl transpeptidase from rat kidney.

The initial rate kinetics of rat kidney gamma-glutamyl transpeptidase were measured using L-gamma-glutamyl-p-nitroanilide and glycyl-glycine as the donor and the acceptor substrate, respectively. Experimental data were fitted with the initial rate equation, and the obtained results indicated that: (1) Michaelis constants for transpeptidation (Kb), autotranspeptidation (Ka), and hydrolysis (Kh) are 8.56 mmol/l, 2.02 mmol/l and 0.005 mmol/l, respectively. (2) The maximum rate of transpeptidation (Vb) exceeds that of hydrolysis (Vh) and autotranspeptidation (Va) 160 times and 5 times, respectively. (3) A comparison of the ratios of maximal rate: Michaelis constant of individual reactions shows that hydrolysis is approximately 10 times more efficient than the remaining two reactions. (4) Under routine conditions used for gamma-glutamyl transpeptidase estimation, transpeptidation is the prevalent reaction.

Animals↗

PubMed1994

Altered glutamate binding following quinolinate lesions in developing rat brain.

To define the ontogeny of "excitotoxic" neurodegeneration further, bilateral intracerebroventricular injection of N-methyl-D-aspartate agonist, quinolinate (QUIN), was administered to rats at Postnatal Days 12, 30, and 50. Excitotoxic injury was quantified by means of changes in [3H]glutamate binding to membranes isolated from the entorhinal cortex, hippocampal formation, cerebellum, and medulla oblongata 4 days after the injection of QUIN. Binding was significantly decreased only in the hippocampal formation of 30- and 50-day-old rats (by 25 and 32%, respectively). In contrast, binding to cortical membranes was elevated by 29 and 56% at Postnatal Days 30 and 50, respectively. Observed changes in the binding of glutamate were due to modifications in the equilibrium binding constants rather than in the density of the receptors. In the cerebellum, which exhibited the highest developmental increase, the statistically significant decrease of the binding (by 36%) following QUIN lesion was only observable on Day 30. The effects of QUIN lesions were not statistically significant in the medulla oblongata. The results suggest that in 30- and 50-day-old rats QUIN can be implicated in neurodegeneration of the entorhinohippocampal complex.

Animals↗

PubMed1994

Relationship between gamma-glutamyl transpeptidase activity and sialic acid content in some organs and brain regions of the developing rat.

The activity of gamma-glutamyl transpeptidase (GGT) and the sialic acid (SA) content were found to be specific in five brain regions of 7- and 50-day-old rats. While a low GGT activity was accompanied by high sialylation in the whole brain a high GGT activity and low sialylation were observed in kidney and pancreas. Similar findings were obtained for some brain regions investigated. However, the developmental differences were not characterized by such relationship. Concanavalin A affinity chromatography of GGT from brain of 7- and 50-day-old rats revealed no remarkable changes in GGT sialylation although the enzyme activity is almost 3 times higher in brain membranes of the older group. It can be concluded that in spite of an apparent relationship between GGT activity and membrane sialylation, the amount of SA linked to the GGT molecule is not related to differences in enzyme activity.

Aging↗

PubMed1993

Effect of repeated hyperammonemia on Na(+)-dependent binding of glutamate in rat cortical and hippocampal synaptic membranes.

Na(+)-dependent binding of L-glutamate in cortical and hippocampal synaptic membranes from hyperammonemic rats was compared to corresponding data in the controls. In hippocampal membranes, repeated hyperammonemia resulted in a 13% and 18% decrease in binding in 20-day-old and 50-day-old rats, respectively. The decrease was statistically significant (P < 0.05) in the older animals and Scatchard analysis revealed a 19% reduction in the number of binding sites without any changes in the affinity. Within the hippocampal formation, the binding in the dentate gyrus was the most sensitive to hyperammonemia where a 21% decrease was found (P < 0.01), whilst the decline of binding in CA1 and CA3 areas of the hippocampus proper was not significant. The results support the idea that excessive accumulation of extracellular glutamate during hyperammonemia is a consequence not only of its increased release, but also of the blocking of Na(+)-dependent binding of glutamate to specific uptake sites.

Aging↗

PubMed1992

The effect of ammonia and pH on brain gamma-glutamyl transpeptidase in young rats.

Acute hyperammonemia, induced by two consecutive injections of ammonium acetate (550 and 450 mg per kg b.wt.), decreased the activity of gamma-glutamyl transpeptidase (GGT) in most brain regions of 18- and 30-day-old rats. This decrease in the brain GGT activity was more pronounced in younger than in older rats. After the addition of NH4Cl to the incubation medium, the inhibitory action of NH4+ on this enzyme activity was also demonstrated in crude synaptosomal membranes at pH 7.4, but in a range of NH4+ concentrations many-times higher than those found in the plasma or brains of young hyperammonemic rats. Because similar concentrations of NH4+ stimulated the activity of the purified enzyme from rat kidney (mainly at pH 9.0), the inhibition of GGT activity in the young rat brain is probably mediated indirectly and not by a direct interaction of ammonia with the enzyme molecules.

Acetates↗

PubMed1992

Developmental changes in the activity of membrane-bound gamma-glutamyl transpeptidase and in the sialylation of synaptosomal membranes from the chick embryonic brain.

gamma-Glutamyl transpeptidase (GGT) is a membrane-bound sialoglycoprotein. The developmental changes in GGT activity and in sialic acid content were determined in a crude synaptosomal membrane fraction from the cerebral hemispheres of the chick embryo between days 11 and 19 of incubation. The GGT activity increased almost eightfold during the examined developmental period, while sialic acid content rose significantly only between days 11 and 15. Cortical administered on day 13 significantly increased GGT activity. On the other hand, the content of membrane bound sialic acid was not substantially affected. The value of the GGT apparent Michaelis constant (Kmapp) for gamma-glutamyl-p-nitroanilide in the presence of 20 mmol.l-1 glycylglycine was 1.5 mmol.l-1 and cortisol did not influence it. However, Vmax was increased by this hormone. The affinity of GGT to concanavalin A (ConA) did not change during development. Neither the administration of cortisol nor neuroaminidase treatment had any effect on the interaction of GGT with ConA. Desialylation of crude synaptosomal fraction did not change GGT activity. The results presented here suggest no developmental nor functional relationship between the activity of GGT and the level of sialylation in synaptosomal membranes from the cerebral hemispheres of the chick embryo.

Animals↗

PubMed1992

Effect of gamma-glutamyl transpeptidase inhibitors on the transport of glutamate into neuronal and glial primary cultures.

Inhibitors of gamma-glutamyl transpeptidase (mixture of serine and borate--13 mM, kainic acid--5 mM and 6-diazo-5-oxo-L-norleucine--2 mM) significantly suppressed glutamate uptake into cultured neurones and glial cells. The simultaneous application of any of these inhibitors with ouabain resulted in a further decline in glutamate uptake. It can be speculated that gamma-glutamyl transpeptidase significantly contributes to glutamate transport into nerve cells in the early period of brain development until the Na(+)-K(+)-gradient is fully constituted.

Aging↗

PubMed1992

Fractionation of gamma-glutamyl transpeptidase from the rat brain, kidney and pancreas by concanavalin A affinity chromatography.

gamma-Glutamyl transpeptidase (GGT) in tissue extracts from five brain regions, the kidney and pancreas of 50-day-old rats was examined for its specific activity and affinity to immobilized concanavalin A (Con A). According to their descending GGT activity, the tissue extracts were classified in the following order: kidney >> pancreas >> olfactory bulbs > medulla oblongata > hippocampus > cerebellum > frontal cortex. Using different concentrations of methyl-alpha-D-mannopyranoside for the elution of GGT from Con A-Sepharose column, the enzyme from brain regions could be separated into five fractions, two of which contained about 75% of the total GGT activity without regional differences in elution profiles. Almost complete GGT activity in kidney tissue extracts was eluted in a single peak whereas the enzyme from pancreas exhibited two peaks.

Animals↗

PubMed1991

Effects of MK-801, ketamine and alaptide on quinolinate models in the maturing hippocampus.

The ability of the N-methyl-D-aspartate receptor antagonists, MK-801, ketamine and alaptide [a newly synthesized cyclo(1-amino-1-cyclopentane-carbonyl-L-alanyl) with protective properties in models of hypoxia], to prevent neuronal degeneration caused by intracerebroventricular application of quinolinic acid was investigated. Neurodegenerative effects of quinolinate in the hippocampal formation were found to increase with the degree of maturity of glutamatergic target structures. A protective potency of the N-methyl-D-aspartate receptor antagonists was observed at all developmental stages studied (12- and 30-day-old and adult rats). MK-801 showed the highest efficacy, alaptide the lowest. These findings suggest a parallelism in maturity of glutamatergic transmission processes as one prerequisite of quinolinate vulnerability and postnatal increases of target fields of the protectives. Application of MK-801 or ketamine after quinolinate injection intensified their protective effects when compared to simultaneous or preadministration. This observation is interpreted as indicating that quinolinate is a prompter of a delayed neurodegenerative process rather than acting immediately as a toxicant.

Animals↗

PubMed1991

Interaction of kainic acid with Na(+)-dependent glutamate binding and uptake in the cerebral cortex of the developing mouse.

The effect of kainic acid, a structural analogue and specific agonist of glutamate, was studied on the Na(+)-dependent binding and uptake of this amino acid in cerebral cortex preparations from 7-day-old and 30-day-old mice. The specific binding of glutamate to a crude synaptic membrane fraction and uptake into cortical slices increased several fold during this period. Kainic acid (0.5 mM or 5 mM) significantly reduced glutamate binding and this effect was more pronounced in membrane fractions from older animals. In contrast to this, the inhibitory action of kainic acid on glutamate uptake was twofold more potent in 7-day-old mice. The results are discussed from the viewpoint of the relationship between the Na(+)-dependent binding of glutamate and its uptake.

Animals↗

PubMed1990

Quinolinate neurotoxicity and glutamatergic structures.

Neurotoxic properties of quinolinic acid following intracerebroventricular application were investigated in the hippocampal formation of 12- and 30-day-old rats. Quinolinic acid neurodegenerative potency was found to depend on the survival time, the dose applied and the developmental stage of the animal. Pretreatment with kynurenic acid and ketamine as well as the transection of the perforant path were noted to protect major parts of the hippocampal cell layers from quinolinic acid-induced degenerative effects. The results are interpreted in view of a putative dependence of quinolinic acid neurotoxicity on the presence of established synaptic, in particular glutamatergic, processes which play a major role in the hippocampal formation and mature during the first postnatal weeks. For comparison, we studied local effects of quinolinic acid on superior cervical and dorsal root ganglia in which glutamate inputs obviously do not occur; no signs of neuronal vulnerability were seen.

Age Factors↗

PubMed1990

Cytotoxic effect of glutamate and its agonists on mouse hippocampal neurons.

The neurodegenerative action of the excitatory amino acid neurotransmitter (glutamate) and its exogenous (N-methyl-D-aspartate, kainate) or endogenous (quinolinate) analogues were studied on cultures of dissociated nerve cells from the embryonal mouse hippocampus. The exposure of primary cultures for 3-6 h to these excitotoxins showed that neurons were vulnerable to both glutamate and all tested agonists which induced the swelling and vacuolization of neuronal bodies accompanied by degeneration of their dendrites. This process terminated by complete cell destruction. The neurotoxic effect of glutamate (1 mM) was not suppressed by a competitive NMDA receptor antagonist (D, L-2-amino-5-phosphonovalerate, 0.3 mM) and was only slightly prevented by gamma-D-glutamylglycine (3mM). The protective action of the latter was more evident in the presence of lower glutamate concentration (0.5 mM). The excitotoxic effect of N-methyl-D-aspartate (0.1 mM) or quinolinate (0.5mM) was almost completely blocked by both antagonists. In contrast, D, L-2-amino-5-phosphonovalerate failed to protect hippocampal neurons from damage induced by kainate while partial antagonism of kainate neurotoxicity was observed with gamma-D-glutamylglycine. These finding suggest that glutamate neurotoxicity may be derived, mainly, from the non-NMDA type(s) of glutamate receptor present on hippocampal cell membranes with a low effectiveness to suppress this effect by selective competitive NMDA antagonist. Possible involvement of glutamate receptor(s) in the early dendritic outgrowth of hippocampal neurons and in the process of neuronal "cell death" is discussed.

2-Amino-5-phosphonovalerate↗