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M V Onufriev

Publications and source records attributed to M V Onufriev.

At least 19 recordsLinked to original sources
PubMed2006

Caspase-like activity is essential for long-term synaptic plasticity in the terrestrial snail Helix.

Although caspase activity in the nervous system of mollusks has not been described before, we suggested that these cysteine proteases might be involved in the phenomena of neuroplasticity in mollusks. We directly measured caspase-3 (DEVDase) activity in the Helix lucorum central nervous system (CNS) using a fluorometrical approach and showed that the caspase-3-like immunoreactivity is present in the central neurons of Helix. Western blots revealed the presence of caspase-3-immunoreactive proteins with a molecular mass of 29 kDa. Staurosporin application, routinely used to induce apoptosis in mammalian neurons through the activating cleavage of caspase-3, did not result in the appearance of a smaller subunit corresponding to the active caspase in the snail. However, it did increase the enzyme activity in the snail CNS. This suggests differences in the regulation of caspase-3 activity in mammals and snails. In the snail CNS, the caspase homolog seems to possess an active center without activating cleavage typical for mammals. In electrophysiological experiments with identified snail neurons, selective blockade of the caspase-3 with the irreversible and cell-permeable inhibitor of caspase-3 N-benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val-Asp-(OMe)-fluoro-methylketone prevented development of the long-term stage of synaptic input sensitization, suggesting that caspase is necessary for normal synaptic plasticity in snails. The results of our study give the first direct evidence that the caspase-3-like activity is essential for long-term plasticity in the invertebrate neurons. This activity is presumably involved in removing inhibitory constraints on the storage of long-term memory.

Animals↗
PubMed2005

Central administration of a caspase inhibitor impairs shuttle-box performance in rats.

Recent studies suggest that caspase-3-mediated mechanisms are essential for neuronal plasticity. N-benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val- Asp(OMe)-fluoromethyl ketone (z-DEVD-fmk), a caspase inhibitor with predominant specificity toward caspase-3, has been shown to block long-term potentiation in hippocampal slices. Intrahippocampal infusion of a caspase-3 inhibitor to rats has been shown to significantly impair spatial memory in the water maze. The present work was designed to study whether i.c.v. administration of a caspase-3 inhibitor z-DEVD-fmk impairs learning in other tasks related to specific forms of memory in rats. The rats received bilateral injections of z-DEVD-fmk or N-benzyloxycarbonyl-Phe-Ala-fluoromethyl ketone (z-FA-fmk) ("control" peptide) at a dose of 3 nmol. Administration of z-DEVD-fmk significantly decreased the number of avoidance reactions in some blocks of trials in the active avoidance (shuttle box) learning, while z-FA-fmk had no effect as compared with intact rats. However, only a slight effect of the caspase inhibitor across the session was found. z-DEVD-fmk impaired development of some essential components of the two-way active avoidance performance, such as escape reaction, conditioned fear reaction, and inter-trial crossings. Measurement of caspase-3 activity in rat brain regions involved in active avoidance learning revealed most expressed z-DEVD-fmk-related inhibition of the enzyme activity (about 30%) in the fronto-parietal cortex. A similar effect was close to significant in the hippocampus, but not in the other cerebral structures studied. In primary cultures of cerebellar neurons z-DEVD-fmk (2-50 microM) inhibited caspase-3 activity by 60-87%. We suggest that moderate inhibition of caspase-3 resulting from the central administration of z-DEVD-fmk to rats may impair active avoidance learning. Taking into account previous data on the involvement of neuronal caspase-3 in neuroplasticity phenomena we assume that the enzyme may be important for selected forms of learning.

Animals↗
PubMed2003

Single intracerebroventricular administration of amyloid-beta (25-35) peptide induces impairment in short-term rather than long-term memory in rats.

Ample experimental evidence indicates that intracerebral injection or infusion of amyloid-beta peptides (Abeta) to rodents induces learning and memory impairments as well as neurodegeneration in brain areas related to cognitive function. In the present study, we assessed the effects of a single intracerebroventricular (i.c.v.) injection of aggregated Abeta fragment (25-35) at a dose of 15nmol/rat on short-term and long-term memory in rats during the 6-month post-surgery period. The results demonstrate that Abeta(25-35)-induced memory impairments in spontaneous alternation behavior in a Y-maze at 17, 36, and 180 days after the surgery as well as in a social recognition task 110 days post-surgery. Abeta(25-35) also impaired spatial memory in an 8-arm radial maze, but did not influence performance of the step-down passive avoidance task. These results suggest that Abeta(25-35) preferably induces impairments of spatial and non-spatial short-term (working) memory rather than long-term memory in rats.

Amyloid beta-Peptides↗
PubMed2003

Administration of aggregated beta-amyloid peptide (25-35) induces changes in long-term potentiation in the hippocampus in vivo.

Intracereroventricular administration of aggregated beta-amyloid protein fragment (25-35) (7.5 nmol/ventricle) was followed one month later by significant changes in the dynamics of long-term potentiation in the hippocampus in vivo, expressed as powerful and stable increases in the amplitude of evoked potentials. This phenomenon may be associated with oxidative stress in the hippocampus, which has previously been demonstrated in this model, and, thus, with disturbances in ion homeostasis.

Amyloid beta-Peptides↗
PubMed2003

Nitric oxide synthase activity in Fasciola hepatica: a radiometric study.

The activity of neuronal nitric oxide synthase (nNOS) in homogenates of adult Fasciola hepatica was measured by the direct radiometric assay of the production of L-[3H]citrulline. This is the first radiometric study of the activity of nNOS in a fluke. The effect of arginase was tested. In the presence of L-valine, which is an inhibitor of arginase, the formation of L-[3H]citrulline decreased from 12% to 38%, depending on the time of incubation. This means that the arginase activity in the worm is high, and has to be taken into consideration when measuring the activity of nNOS. When co-factors, such as H4B, and NADPH, were omitted the formation of L-[3H]citrulline decreased significantly (29%). The effects of several nNOS inhibitors were tested. N(omega)-nitro-L-arginine (L-NAME), aminoguanidine and S-methyl-L-thiocitrulline added at a concentration of 1 mM inhibited the L-[3H]citrulline formation by 28%, 15% and 14%, respectively. Chelation of Ca2+ with 1 mM EGTA resulted in a 40% decrease in the formation of L-[3H]citrulline. These results indicate the presence of nNOS activity in homogenates of F. hepatica.

Animals↗
PubMed2001

Periods of postnatal maturation of hippocampus: synaptic modifications and neuronal disconnection.

The paired-pulse paradigm was used to study the maturation of CA1 population spikes (PS) in the hippocampal slices of Wistar rats. Measurements were taken daily, from postnatal day (PN) 14 to PN27. In the slices from younger animals, inputs exhibit strong paired-pulse profile, which may be associated with low synaptic efficacy. Both responses increased during the third week of life, however, PS1 increased faster so that the PS1/PS2 ratio increased during the early period and remained increased thereafter. This may reflect postnatal modifications of synaptic transmission mediating the increase in hippocampal responses. Modifications of synaptic efficacy are prevailing during early phases while other mechanisms take over at later stages. Partial correlation analysis suggests that the decline of PS amplitude after PN19 may be due to the decrease in the number of connected neurons rather than to modifications of the synaptic efficacy. Thus, the actual direction and magnitude of postnatal PS maturation is suggested to depend on the balance of these two factors. The transient decline of PS amplitude coincided with a period of caspase-3 activation. There was a clear general trend for caspase-3 activity to decrease before PN17, while the inverse trend was observed during next period up to PN21.

Action Potentials↗
PubMed2000

Role of nitric oxide in the ethylcholine aziridinium model of delayed apoptotic neurodegeneration in vivo and in vitro.

The involvement of nitric oxide in neurodegenerative processes still remains incompletely characterized. Although nitric oxide has been reported to be an important mediator in neuronal degeneration in different models of cell death involving NMDA-receptor activation, increasing evidence for protective mechanisms has been obtained. In this study the role of nitric oxide was investigated in a model of NMDA-independent, delayed apoptotic cell death, induced by the neurotoxin ethylcholine aziridinium ethylcholine aziridinium both in vivo and in vitro. For the in vivo evaluation rats received bilateral intracerebroventricular injections of ethylcholine aziridinium (2nmol/ventricle) or vehicle. In the hippocampus a transient decrease in nitric oxide synthase activity occurred, reaching its lowest levels three days after ethylcholine aziridinium treatment (51.7+/-9.8% of controls). The decrease coincided with the maximal reduction in choline acetyltransferase activity as marker for the extent of cholinergic lesion. The effect of pharmacological inhibition of nitric oxide synthase was tested by application of various nitric oxide synthase inhibitors with different selectivity for the nitric oxide synthase-isoforms. Unspecific nitric oxide synthase inhibition resulted in a significant potentiation of the loss of choline acetyltransferase activity in the hippocampus measured seven days after ethylcholine aziridinium application, whereas the specific inhibition of neuronal or inducible nitric oxide synthase was ineffective. These pharmacological data are suggestive for a neuroprotective role of nitric oxide generated by endothelial nitric oxide synthase. In vitro experiments were performed using serum-free primary neuronal cell cultures from hippocampus, cortex and septum of E15-17 Wistar rat embryos. Ethylcholine aziridinium-application in a range of 5-80microM resulted in delayed apoptotic neurodegeneration with a maximum after three days as confirmed by morphological criteria, life-death assays and DNA laddering. Nitric oxide synthase activity in harvested cells decreased in a dose- and time-dependent manner. Nitric oxide production as determined by measurement of the accumulated metabolite nitrite in the medium was equally low in controls and in ethylcholine aziridinium treated cells (range 0.77-1.86microM nitrite). An expression of inducible nitric oxide synthase messenger RNA could not be detected by semiquantitative RT-PCR 13h after ethylcholine aziridinium application. The present data indicate that in a model of delayed apoptotic neurodegeneration as induced by ethylcholine aziridinium neuronal cell death in vitro and in vivo is independent of the cytotoxic potential of nitric oxide. This is confirmed by a decrease in nitric oxide synthase activity, absence of nitric oxide production and absence of inducible nitric oxide synthase expression. In contrast, evidence for a neuroprotective role of nitric oxide was obtained in vivo as indicated by the exaggeration of the cholinergic lesion after unspecific nitric oxide synthase inhibition by N-nitro-L-arginine methylester.

Animals↗
PubMed2000

A radiometric analysis of nitric oxide synthase activity in Hymenolepis diminuta.

The free radical nitric oxide (NO) is a neuronal messenger which is synthesized from L-arginine and O2 by nitric oxide synthase (NOS). In the synthesis NO and L-citrulline are produced in a stoichiometric 1:1 relation. The activity of NOS was analysed in homogenates of the rat tapeworm Hymenolepis diminuta by measuring the formation of L-[3H]citrulline after incubation with L-[3H]arginine. The nature of NOS in H. diminuta was determined by studying the effect of 3 types of NOS inhibitors: (1) L-NAME, (2) EGTA, (3) 7-nitro-indazole. All inhibitors caused a significant but not complete reduction in the formation of L-[3H]citrulline. The results are discussed against the background of nerve cells and fibres positive for NADPH-diaphorase staining in H. diminuta.

Animals↗
PubMed1999

[The effect of oxidative stress on brain nitric oxide synthase activity in vivo and in vitro].

Within 8 days of a 10-min cardiac arrest, accumulation of material reacting with 2-thiobarbituric acid was revealed in the hippocampus (74%) and cerebellum (47%) of male Wistar rats. Oxidative stress was accompanied by a twofold decrease of the nitric oxide synthase activity in the brain tissue. In vitro experiments showed a dose-dependent decrease of nitric oxide synthase activity in the brain homogenates as a result of the oxidative stress induced by hydrogen peroxide or sodium hypochlorite. The findings suggest that the oxidative stress may decrease nitric oxide synthase activity as a result of direct effects of the active oxygen on the enzyme.

Animals↗
PubMed1997

Prophylaxis of encephalopathies and risk factors of atherogenesis development in the postresuscitation period in rats by means of succinic acid.

The effect of oral administration of succinic acid was studied in 66 rats exposed to 10 min cardiac arrest with further resuscitation. A total of 30 mg/kg of the drug were administered daily for 5 days starting with day 3 up to day 7 after resuscitation. The experiments have revealed that treatment with succinic acid caused normalization of the orienting behavior in an 'open field' test, decrease of the intensity of response to electric shock, normalization of free radical formation in the brain and serum and reduced cerebral morphological changes. The succinic acid prevented the increase of cholesterol, triglyceride and low density lipoproteins in the blood. The data suggested that after additional trials the succinic acid could be used to prevent development of postresuscitation encephalopathies (3 months after reanimation).

Animals↗
PubMed1997

Postresuscitation changes in brain free radical-mediated processes and nitric oxide synthase activity in rats: effects of individual behavior in "emotional resonance" test.

Effects of 7-min cardiac arrest and individual behavior on free radical-mediated processes and nitric oxide synthase (NOS) activity was evaluated in brains of male Wistar rats one hour and one week after resuscitation. "Emotional resonance" test was used for the behavioral selection of rats. The test includes factors of significance for rats: the choice between large and lighted or small and dark space as well as signals of pain of another rat. Free radical generation (using chemiluminescence method), superoxide scavenging/generating activity, substances reacting with 2-thiobarbituric acid and NOS activity (by measuring mononitrosyl iron complex of NO with diethyl dithiocarbamate and endogenous brain Fe2+ by electron spin resonance spectroscopy) were determined in cerebral cortex, cerebellum and hippocampus. Cardiac arrest induced oxidative stress accompanied by the loss of NOS activity, as well as compensatory changes of free radical-mediated processes in cerebral cortex. Oxidative stress was also evident in cerebellum and, to a lesser extent, in hippocampus. Most of neurochemical differences between behavioral groups were induced by cardiac arrest. These differences were global, related to a specific brain region or became apparent in cerebral lateralization of biochemical indices.

Adaptation, Psychological↗
PubMed1996

Cardiac arrest induces decrease of nitric oxide synthase activity and increase of free radical generation in rat brain regions.

Rats were subjected to 15 min cardiac arrest and sacrificed 1 h or 15-20 days after resuscitation. Homogenates of brain regions were assayed for nitric oxide synthase (NOS) activity (by measuring the mononitrosyl iron complex of NO with diethyl dithiocarbamate and endogenous brain Fe2+ using electron spin resonance spectroscopy) and generation of free radicals (FRG; by measuring H2O2-induced, luminol-dependent chemiluminescence). Cardiac arrest induced marked decrease of NOS activity and the increase of FRG, most prominent in cerebellum and less marked in cerebral cortex. Two groups of rats were revealed 15-20 days after cardiac arrest: with NOS activity significantly lower than control and not different from control. Positive linear inter-regional cross-correlations of both NOS activity and FRG (except of the group 1 h after resuscitation) as well as negative correlations between NOS and FRG were demonstrated.

Animals↗
PubMed1996

Oxidative stress in the brain following intraventricular administration of ethylcholine aziridinium (AF64A).

AF64A is a toxic analog of choline that disrupts high affinity choline transport and produces a persistent presynaptic cholinergic hypofunction. The observed neuroprotectant effects of Vitamin E in the AF64A model suggested that oxidative stress contributed to the cholinotoxicity of AF64A. The studies presented here examined whether intraventricular injection of AF64A produces oxidative stress in the brain of male Wistar rats. Indices of oxidative stress including thiobarbituric acid reactive species (TBARS), free radical generation using hydrogen peroxide-induced, luminol-dependent chemiluminescence (CL) and superoxide scavenging/generating activity were measured in cerebral cortex, hippocampus and the rest of the brain, without cerebellum, 1, 3 or 5 days after bilateral intraventricular injection of 3 nmol of AF64A or artificial CSF (sham surgery). The sham operation itself induced oxidative stress throughout the brain (increased TBARS, CL and superoxide generation). In addition to the oxidative stress of the sham surgery AF64A increased basal TBARS on day 1 and Fe/ascorbate-induced TBARS on days 3 and 5 throughout the brain. AF64A produced compensatory 'antioxidative' changes as well with increased superoxide scavenging activity observed on day 3 and decreased basal TBARS on day 5. AF64A also induced specific changes in the hippocampus including a decrease of CL and an increase of superoxide scavenging activity on day 5. The increased superoxide scavenging activity persisted up to 126 days. The results of the present study provide the first direct evidence that AF64A induces oxidative stress following intraventricular injection.

Animals↗
PubMed1994

NO synthase and free radical generation in brain regions of old rats: correlations with individual behaviour.

We have investigated the activity of NO synthase (NOS) and generation of free radicals (FRG) in selected brain regions of old male Wistar rats. Using the emotional resonance test, two groups of rats were selected for the experiment: passive, preferring dark space and active, preferring light space. Highest NOS activity and FRG were seen in cerebellum. As a rule, NOS activity was lower and FRG higher in the respective brain regions of active rats than in passive rats. Positive linear inter-regional cross-correlations of NOS activity as well as of FRG were found. When all rats were assessed as one group, negative correlations between NOS and FRG in cerebral cortex were revealed.

Aging↗