Biomedical subjects

C Zona

Publications and source records attributed to C Zona.

At least 19 recordsLinked to original sources

PubMed2005

Optimisation study of alpha-cyclotron production of At-211/Po-211g for high-LET metabolic radiotherapy purposes.

The production of no-carrier-added (NCA) alpha-emitter (211)At/(211g)Po radionuclides for high-LET targeted radiotherapy and immunoradiotherapy, through the (209)Bi(alpha,2n) reaction, together with the required wet radiochemistry and radioanalytical quality controls carried out at LASA is described, through dedicated irradiation experiments at the MC-40 cyclotron of JRC-Ispra. The amount of both the gamma-emitter (210)At and its long half-lived alpha-emitting daughter (210)Po is optimised and minimised by appropriate choice of energy and energy loss of alpha particle beam. The measured excitation functions for production of the main radioisotopic impurity (210)At-->(210)Po are compared with theoretical predictions from model calculations performed at ENEA.

Astatine↗

PubMed2005

Exposure to 50 Hz electromagnetic radiation promote early maturation and differentiation in newborn rat cerebellar granule neurons.

The wish of this work is the study of the effect of electromagnetic (EMF) radiations at a frequency of 50 Hz on the development of cerebellar granule neurons (CGN). Granule neurons, prepared from newborn rat cerebellum (8 days after birth), were cultured after plate-seeding in the presence of EMF radiations, with the plan of characterizing their cellular and molecular biochemistry, after exposure to the electromagnetic stimulus. Five days challenge to EMF radiations showed, by the cytotoxic glutamate (Glu) pulse test, a 30% decrease of cells survival, while only 5% of mortality was reported for unexposed sample. Moreover, blocking the glutamate receptor (GluR) with the Glu competitor MK-801, no toxicity effect after CGN challenge to EMF radiations and Glu was detected. By patch-clamp recording technique, the Kainate-induced currents from 6 days old exposed CGN exhibited a significant increase with respect to control cells. Western blot and reverse transcription-polymerase chain reaction (RT-PCR) analyses show that EMF exposure of rats CGN, induces a change in both GluRs proteins and mRNAs expression with respect to control. In addition, the use of monoclonal antibody raised against neurofilament protein (NF-200) reveals an increase in NF-200 synthesis in the exposed CGN. All these results indicate that exposure to non-ionizing radiations contribute to a premature expression of GluRs reducing the life span of CGN, leading to a more rapid cell maturation.

Animals↗

PubMed2003

alpha-Amino-3-hydroxy-5-methyl-isoxazole-4-propionate receptors in spinal cord motor neurons are altered in transgenic mice overexpressing human Cu,Zn superoxide dismutase (Gly93-->Ala) mutation.

There are many evidences implicating glutamatergic toxicity as a contributory factor in the selective neuronal injury occurring in amyotrophic lateral sclerosis (ALS). This neurodegenerative disorder is characterized by the progressive loss of motor neurons, whose pathogenesis is thought to involve Ca(2+) influx mediated by alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate receptors (AMPARs). In the present study we report alterations in the AMPARs function in a transgenic mouse-model of the human SOD1(G93A) familial ALS. Compared with those expressed in motor neurons carrying the human wild type gene, AMPAR-gated channels expressed in motor neurons carrying the human mutant gene exhibited modified permeability, altered agonist cooperativity between the sites involved in the process of channel opening and were responsible for slower spontaneous synaptic events. These observations demonstrate that the SOD1(G93A) mutation induces changes in AMPAR functions which may underlie the increased vulnerability of motor neurons to glutamatergic excitotoxicity in ALS.

Alanine↗

PubMed2003

Altered long-term corticostriatal synaptic plasticity in transgenic mice overexpressing human CU/ZN superoxide dismutase (GLY(93)-->ALA) mutation.

Apart from the extensive loss of motor neurons, degeneration of midbrain dopaminergic cells has been described in both familial and sporadic forms of amyotrophic lateral sclerosis (ALS). Mice overexpressing the mutant human Cu/Zn superoxide dismutase (SOD1) show an ALS-like phenotype in that they show a progressive death of motor neurons accompanied by degeneration of dopaminergic cells. To describe the functional alterations specifically associated with this dopaminergic dysfunction, we have investigated the corticostriatal synaptic plasticity in mice overexpressing the human SOD1 (SOD1+) and the mutated (Gly(93)-->Ala) form (G93A+) of the same enzyme. We show that repetitive stimulation of the corticostriatal pathway generates long-term depression (LTD) in SOD1+ mice and in control (G93A-/SOD1-) animals, whereas in G93A+ mice the same stimulation generates an N-methyl-D-aspartic acid receptor-dependent long-term potentiation. No significant alterations were found in the intrinsic membrane properties of striatal medium spiny neurons and basal corticostriatal synaptic transmission of G93A+ mice. Bath perfusion of dopamine or the D(2) dopamine receptor agonist quinpirole restored LTD in G93A+ mice. Consistent with these in vitro results, habituation of locomotor activity and striatal-dependent active avoidance learning were impaired in G93A+ mice. Thus, degeneration of dopaminergic neurons in the substantia nigra of G93A+ mice causes substantial modifications in striatal synaptic plasticity and related behaviors, and may be a cellular substrate of the extrapyramidal motor and cognitive disorders observed in familial and sporadic ALS.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed2001

Levetiracetam does not modulate neuronal voltage-gated Na+ and T-type Ca2+ currents.

This study investigated whether the mechanism of action of levetiracetam (LEV) is related to effects on neuronal voltage-gated Na+ or T-type Ca2+currents. Rat neocortical neurones in culture were subjected to the whole-cell mode of voltage clamping under experimental conditions designed to study voltage-gated Na+ current. Additionally, visually identified pyramidal neurones in the CA1 area of rat hippocampal slices were subjected to the whole-cell mode of voltage clamping under experimental conditions designed to study low-voltage-gated (T-type) Ca2+ current. LEV (10 microM-1 mM) did not modify the Na+ current amplitude and did not change (200 microM) the steady-state activation and inactivation, the time to peak, the fast kinetics of the inactivation and the recovery from the steady-state inactivation of the Na+ current. Likewise, LEV (32-100 microM) did not modify the amplitude and did not change the steady-state activation and inactivation, the time to peak, the fast kinetics of the inactivation and the recovery from the steady-state inactivation of the T-type Ca2+current. In conclusion, neuronal voltage-gated Na+ channels do not appear directly involved in the antiepileptic mechanism of action of LEV, and LEV was devoid of effect on the low-voltage-gated (T-type) Ca2+ current in hippocampal neurones.

Animals↗

PubMed2000

Effect of P2 purinoceptor antagonists on kainate-induced currents in rat cultured neurons.

The action of purinergic antagonists on kainate-induced currents was studied in rat cortical neurons in primary culture using the whole-cell configuration of the patch-clamp technique. The amplitude of the currents induced by kainate in cortical neurons was concentration-dependent (EC(50)=106 microM). Pyridoxal-phosphate-6-azophenyll-2',4'-disulphonic acid 4-sodium (PPADS), a P2X antagonist, was ineffective in the reduction of the kainate-induced current in cortical neurons, while 2, 2'-pyridylisatogen (PIT), basilen blue (BB) and suramin, respectively two selective P2Y and a non-selective P2 receptor antagonist, caused a reduction in the amplitude of the current induced by kainate. BB decreased the inward current induced by kainate at all holding potentials and the reduction was dose-dependent (EC(50)=34 microM). The total conductance of the neurons for the kainate-induced current was significantly reduced (P<0.01) and the effect was completely reversible. BB furthermore reduced the kainate-induced current in granule and hippocampal neurons and decreased the amplitude of the alpha-amino-3-hydroxy-5-methyl-4-isoxalepropionic acid (AMPA)-evoked current in cortical neurons. Cholera toxin (ChTx) did not affect the action of BB on the kainate-induced currents in cortical neurons and moreover, when guanosine 5'-o-(3-thiotriphosphate) (GTPgammaS) was added to the electrode solution, the kainate-induced currents were still reduced by 100 microM BB. The maximal response to kainate decreased in the presence of 20 microM BB without changing its EC(50), indicating a non-competitive mechanism of inhibition. These results demonstrate that preferential P2Y receptor antagonists are able to modulate the kainate and AMPA-induced currents in central neurons, suggesting a potential use of these compounds as neuroprotective agents.

Action Potentials↗

PubMed1999

Neuroprotective effects of riluzole: an electrophysiological and histological analysis in an in vitro model of ischemia.

The protective effects of riluzole against the neuronal damage caused by O2 and glucose deprivation (ischemia) was investigated in rat cortical slices by recording electrophysiologically the cortico-cortical field potential and by evaluating histologically the severity of neuronal death. Five minutes of ischemia determined an irreversible depression of the amplitude of the field potential. In addition, this insult caused a clear enhancement of the number of death cells that were specifically colored with trypan blue (a vital colorant which stains altered cells). We found that riluzole, which by itself depressed the synaptic transmission, neuroprotected when perfused 15-20 min before and during ischemia. In fact, due to the treatment with riluzole, the ischemia-induced irreversible depression of the field potential recovered and less cells were stained with trypan blue. These findings demonstrate that riluzole prevents neuronal death in an in vitro model of ischemia and suggest a therapeutic use of this drug in order to reduce the pathophysiological outcomes of stroke.

Animals↗

PubMed1998

Voltage-activated sodium currents in a cell line expressing a Cu,Zn superoxide dismutase typical of familial ALS.

The whole-cell configuration of the patch-clamp recording was used to study the voltage-dependent Na+ currents in a model system for the familial form of amyotrophic lateral sclerosis (ALS) associated with mutations in Cu,Zn superoxide dismutase. Here we report that the amplitude of voltage-gated Na+ currents is significantly reduced in cell lines expressing mutant Cu,Zn superoxide dismutase G93A when compared with the parental, untransfected cell line and to a cell line expressing the wild-type enzyme. This effect is associated with a shift toward positive values of the steady-state inactivation curve of the Na+ currents. These results indicate that expression of a Cu,Zn superoxide dismutase typical of patients affect with familial ALS influence the functionality of the voltage-dependent Na+ channels; this effect may contribute to the pathogenesis of the disease.

4-Aminopyridine↗

PubMed1998

An electrophysiological analysis of the protective effects of felbamate, lamotrigine, and lidocaine on the functional recovery from in vitro ischemia in rat neocortical slices.

We used field potential recording techniques to examine whether felbamate (FBM), lamotrigine (LTG), and lidocaine (LID) protect against the irreversible functional damage induced by transient ischemia. Five minutes of ischemia caused a depression of the field potential in rat cortical slices, which did not recover even after more than 1 h of washout. The N-methyl-D-aspartate (NMDA) antagonist ketamine (50 microM) protected against depression of the field caused by ischemia. On the other hand, the non-NMDA antagonist 6-cyano-7-nitroquinoxaline-2.3-dione (CNQX) (10 microM) had protective effects only if co-applied with ketamine. We found that either FBM (30-300 microM), which did not modify the amplitude of the field EPSP, or LTG (10-300 microM), which reversibly depressed the excitatory synaptic transmission, had a marked protective effect when superfused before and during the ischemic insult. After FBM (100 microM) and LTG (100 microM), the field EPSP recovered by 84 +/- 1% and 73 +/- 2.7% of control, respectively. Furthermore, LID (30-300 microM) was less effective than FBM and LTG in inducing a functional recovery from the damage caused by ischemia (58 +/- 1.8%). The rank order of potency, based on the maximal protection caused by the three drugs, was FBM > LTG > LID. Our results suggest that a noticeable neuroprotection can be obtained during glucose and O2 deprivation by preventive therapeutic regimens which use the two recently marketed anticonvulsant drugs, FBM and LTG.

Action Potentials↗

PubMed1998

Riluzole interacts with voltage-activated sodium and potassium currents in cultured rat cortical neurons.

The actions of the neuroprotective and anticonvulsant agent riluzole on voltage-activated currents were studied in primary cultures of rat cortical neurons by using whole-cell patch-clamp recording techniques. Isolated Na+, Ca2+ and K+ currents were generated in these cells by depolarizing commands from a holding potential of - 80 mV. Riluzole (10-300 microM) reversibly reduced in a dose-dependent manner the inward Na+ currents with an IC50 of 51 microM in all the tested neurons (n=29). This drug also shifted the steady-state inactivation curve of the sodium current towards more negative values (about 20mV, n=15) while it did not change significantly the decay phase of the Na+ current. Furthermore, riluzole (100 and 300 microM; n=5 and n=3, respectively) did not modulate the inward Ca2+ currents evoked by depolarizing steps on cortical cells. An additional concentration-dependent effect of riluzole was observed on the outward potassium currents. In fact, while the amplitude of the peak of the outward current (IA) was not changed significantly, the amplitude of the late component of the outward K+ current (Iss) was markedly decreased during the perfusion of riluzole (IC50=88 microM; n=16). It is concluded that riluzole modulates the Na+- and the late K+-dependent currents in cortical neurons. Both phenomena may explain, at least in part, the anticonvulsant and neuroprotective properties of this compound.

4-Aminopyridine↗

PubMed1997

Topiramate attenuates voltage-gated sodium currents in rat cerebellar granule cells.

Whole-cell, voltage-clamp recordings were made from rat cerebellar granule cells in culture under experimental conditions designed to study voltage-gated Na+ currents that were elicited by depolarizing commands from a holding potential of -60 mV up to +20 mV. These tetrodotoxin-sensitive inward currents were reduced in a dose-related manner by bath application of the structurally novel, anticonvulsant drug topiramate (10-1000 microM; n = 16). Dose-response analysis of this effect revealed an IC50 of 48.9 microM. Topiramate also made the steady-state inactivation curve of this current shift toward more negative values (midpoint of the inactivation curve -46.9 mV under control conditions and -56.5 mV during topiramate application; n = 5). We propose that these effects may contribute to control the sustained depolarizations with repetitive firing of action potentials that occur within neuronal networks during seizure activity. Therefore they may represent a mechanism of action for this novel anticonvulsant drug.

Animals↗

PubMed1997

NMDA receptor modulation by a conditioned medium derived from rat cerebellar granule cells.

Our previous studies have shown that the response to the excitotoxic action of glutamate by cultured cerebellar granule cells depends upon the cell density or the volume of medium in which they have been grown: the higher the cell density or the lower the volume, the higher the response to glutamate. We have hypothesized that this variable response is due to the formation in culture of a glutamate-sensitizing activity GSA more abundantly in conditioned medium derived from high-density or low-volume cultures than that present in low-density or high volume cultures and capable of restoring sensitivity in previously resistant granule cells. In order to elucidate the mechanism of action of glutamate-sensitizing activity, we measured the extent and function of NMDA receptors in low- and high-volume cultures and assessed the effect of glutamate-sensitizing activity on the same receptors. We found that under high-volume conditions the extent of MK-801 binding, the amount of NMDA receptor type 1, the currents evoked in whole cells after an NMDA pulse and the response of cultured cells to this ligand were markedly reduced compared with low-volume cultures. Addition of glutamate-sensitizing activity to high-volume cultures increased their glutamate sensitivity, the NMDA-evoked currents, the extent of MK-801 binding and the amount of NMDA receptor type 1 protein present. The corresponding mRNA transcripts, on the contrary, were unchanged in high-volume, low-volume and high-volume GSA-treated cultures.

Animals↗

PubMed1997

Lamotrigine reduces voltage-gated sodium currents in rat central neurons in culture.

PURPOSE: To study the mechanism or mechanisms of action of lamotrigine (LTG) and, in particular, to establish its effects on the function of NA+ channels in mammalian central neurons. METHODS: Rat cerebellar granule cells in culture were subjected to the whole-cell mode of voltage clamping under experimental conditions designed to study voltage-gated Na+ currents. RESULTS: Extracellular application of LTG (10-500 microM, n = 21) decreased in a dose-related manner a tetrodotoxin-sensitive inward current that was elicited by depolarizing commands (from -80 to +20 mV). The peak amplitude of this Na(+)-mediated current was diminished by 38.8 +/- 12.2% (mean +/- SD, n = 6) during application of 100 microM LTG, and the dose-response curve of this effect indicated an IC50 of 145 microM. The reduction in the inward currents produced by LTG was not associate with any significant change in the current decay, whereas the voltage dependency of the steady-state inactivation shifted toward more negative values (midpoint of the inactivation curve: -47.5 and -59.0 mV under control conditions and during application of 100 microM LTG, respectively, n = 4). CONCLUSIONS: Our findings indicate that LTG reduces the amplitude of voltage-gated Na+ inward current in rat cerebellar granule cells and induces a negative shift of the steady-state inactivation curve. Both mechanisms may be instrumental in controlling the repetitive firing of action potentials (AP) that occurs in neuronal networks during seizure activity.

Animals↗

PubMed1995

Human recombinant IGF-I induces the functional expression of AMPA/kainate receptors in cerebellar granule cells.

We have previously reported that an excitatory amino acid resistant phenotype (EAA-) of rat cerebellar granule cells becomes EAA sensitive (EAA+) when cultured in the presence of human recombinant IGF-I. In order to assess the mechanism through which this somatomedin upmodulates the functional expression of EAAs receptors, we have performed studies using the whole-cell configuration of the patch-clamp technique to study macroscopic currents evoked by the application in the bath of kainate to (EAA-) and (EAA+) neurons, and compared their properties to sister cultures grown in classical conditions employing whole foetal calf serum (FCS). Kainate elicited macroscopic, 6-cyano-7-nitroquinoxaline-2,3-dione sensitive, inward currents at a holding potential of -60 mV in almost all the patched cells but the mean amplitude of the current was consistently smaller in (EAA-) neurons compared to (EAA+) neurons although the amplitude was still smaller than that observed in FCS-cultured neurons. The amplitude of the responses induced by kainate was a linear function of the membrane potential in the three groups of cells and the reversal potential of the currents was about 0 mV, suggesting that the general property of each channel is identical in all three types of neurons while the different conductances observed are due either to a decreased expression, a different permeability or an altered affinity of the single receptor.

6-Cyano-7-nitroquinoxaline-2,3-dione↗

PubMed1994

Age-dependent appearance of synaptic currents in rat neocortical neurons in culture.

Rat neocortical neurons grown in dissociated cell culture were recorded with the whole-cell patch-clamp technique. Spontaneous inward currents were observed in cells that were held at a membrane potential of -80 mV in medium containing tetrodotoxin and Cd2+. These currents displayed amplitudes up to 140 pA and rise time of 1.8 +/- 0.2 ms (mean +/- SD, n = 15). They reversed near 0 mV and showed no voltage-dependent frequency of occurrence. Hence, they were presumably due to spontaneous release of transmitter. The inward currents appeared around day 10 in culture and were detected up to 4 weeks. When cells of different ages were compared, the maximal probability of recording these inward events occurred at around 3 weeks in culture. The inward currents were not reduced by application of bicuculline methiodide which is a competitive antagonist of the GABAA receptor, but were blocked by the broad-spectrum glutamate receptor antagonist kynurenic acid. Moreover, spontaneous inward events were not affected by DL-2-aminophosphono-valerate (NMDA receptor antagonist) but disappeared following application of the non-NMDA receptors antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Our observations indicate that the inward currents represent miniature synaptic events that are primarily mediated by non-NMDA excitatory amino acid receptor subtypes. Furthermore, our findings indicate that they develop over time and are not present in neurons that are grown in culture for less than 10 days.

2-Amino-5-phosphonovalerate↗

PubMed1994

Effect of differentiation on hydrolysis and association of Leu-enkephalin to K562(S) cells.

Hydrolysis of Leu-enkephalin and association to cells of the peptide-radioactive label have been studied on the K562(S) erythroleukemic cell subline. Data obtained indicate that in the presence of these cells, Leu-enkephalin is hydrolyzed, that the peptide's radioactive label is partially associated to cells, and that these phenomena are related. Hydrolysis and association are inversely modified by the cells' differentiation: hydrolysis is increased and association is decreased in differentiated compared with nondifferentiated cells. Moreover, the ratio of hydrolysis by-products is dissimilar between differentiated and nondifferentiated cells as a result of a significant modification of the soluble enzymes' release. The alterations induced by differentiation on all parameters investigated seem to indicate significant changes in the membrane structures responsible for the mechanisms controlling these phenomena.

Amino Acid Sequence↗

PubMed1993

Sodium, calcium and late potassium currents are reduced in cerebellar granule cells cultured in the presence of a protein complex conferring resistance to excitatory amino acids.

Whole-cell, patch-clamp recordings were used to study voltage-gated currents generated by cerebellar granule cells that were cultured in medium containing either 10% fetal calf serum (hereafter termed S + granules) or neurite outgrowth and adhesion complex (NOAC, hereafter called NOAC granules). NOAC is a protein complex found in rabbit serum that renders granules resistant to the excitotoxic action of excitatory amino acids. During depolarizing commands both S+ and NOAC granules generated Na+ and Ca2+ inward currents and an early and a late K+ outward currents. However, Na+ and Ca2+ inward currents and late outward K+ currents recorded in NOAC granules were smaller than those seen in S+ granules. Furthermore, although of similar amplitude, early K+ currents displayed different kinetics in the two types of neurons. Thus, these data demonstrate that the electrophysiological properties of cerebellar granules, and probably of other neuronal populations, depend upon serum components and raise the possibility that an analogous modulation might be operative in vivo, and play a role in development, synaptic plasticity or neuropathological processes.

4-Aminopyridine↗

PubMed1993

Recombinant human insulin-like growth factor I exerts a trophic action and confers glutamate sensitivity on glutamate-resistant cerebellar granule cells.

Cerebellar granule cells grown in the presence of a serum complex differentiate but are resistant to the lethal action of excitatory amino acids. When these cells are grown also in the presence of insulin-like growth factor I (IGF-I) they become fully susceptible to the toxic, lethal action of glutamate. The glutamate-sensitizing action of IGF-I is dependent on concentration (half-maximal effect at 2-4 ng/ml) and time (half-maximal effect at 2-4 days in vitro) and is paralleled by the appearance of functionally active, glutamate-activated, Ca2+ channels and of voltage-gated Na+ and late K+ channels. IGF-I-induced glutamate sensitivity is rapidly reversible (t1/2 = 30-60 min) after removal of this somatomedin. The action of IGF-I is not mimicked by IGF-II, nerve growth factor, basic or acidic fibroblast growth factor, platelet-derived growth factor, or tumor necrosis factor alpha. We postulate that the constitutive phenotype of cerebellar granule cells is glutamate-resistant and becomes responsive to excitatory amino acids under the action of epigenetic cues among which IGF-I may be one of those operative in vivo.

Animals↗