A magnetic glassy phase in Fe(1+y)Se(x)Te(1-x) single crystals.

The evolution of magnetic order in Fe1+ySexTe1-x crystals as a function of Se content was investigated by means of ac/dc magnetometry and muon-spin spectroscopy. Experimental results and self-consistent density functional theory calculations both indicate that muons are implanted in vacant iron-excess sites, where they probe a local field mainly of dipolar origin, resulting from an antiferromagnetic (AFM) bicollinear arrangement of iron spins. This long-range AFM phase becomes progressively disordered with increasing Se content.

First direct observation of the Van Hove singularity in the tunnelling spectra of cuprates.

In two-dimensional (2D) lattices, the electronic levels are unevenly spaced, and the density of states (DOS) displays a logarithmic divergence known as the Van Hove singularity (VHS). This is the case in particular for the layered cuprate superconductors. The scanning tunnelling microscope (STM) probes the DOS, and is therefore the ideal tool to observe the VHS.

Imaging the essential role of spin fluctuations in high-T(c) superconductivity.

We have used scanning tunneling spectroscopy to investigate short-length electronic correlations in three-layer Bi2Sr2Ca2Cu3O(10+delta) (Bi-2223). We show that the superconducting gap and the energy Omega(dip), defined as the difference between the dip minimum and the gap, are both modulated in space following the lattice superstructure and are locally anticorrelated. Based on fits of our data to a microscopic strong-coupling model, we show that Omega(dip) is an accurate measure of the collective-mode energy in Bi-2223.

Preeminent role of the van Hove singularity in the strong-coupling analysis of scanning tunneling spectroscopy for two-dimensional cuprate superconductors.

In two dimensions the noninteracting density of states displays a van Hove singularity (VHS) which introduces an intrinsic electron-hole asymmetry, absent in three dimensions. We show that due to this VHS the strong-coupling analysis of tunneling spectra in high-Tc superconductors must be reconsidered. Based on a microscopic model which reproduces the experimental data with excellent accuracy, we elucidate the peculiar role played by the VHS in shaping the tunneling spectra, and show that more conventional analysis of strong-coupling effects can lead to severe errors.

A cell-permeable peptide inhibitor TAT-JBD reduces the MPP+-induced caspase-9 activation but does not prevent the dopaminergic degeneration in substantia nigra of rats.

Many studies showed that 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) which was widely used to produce Parkinson's disease (PD)-like models in animals can elicit apoptosis with increase of caspase activity via its neurotoxic metabolite 1-methyl-4-phenylpyridinium ion (MPP(+)). Another pathway shown in MPTP-mediated nigrostriatal dopaminergic cell death involved the c-Jun-N-terminal kinases (JNKs) which are stress-activated protein kinases (SAPKs). Activation of the JNKs leads to the activation of transcription factors such as c-Jun that regulates its own expression.

Regulation of initiation factors controlling protein synthesis on cultured astrocytes in lactic acid-induced stress.

The goals of this work were first to assess whether the lactic acidosis observed in vivo in ischemia may by itself explain the inhibition of protein synthesis described in the literature and second to study the factors controlling the initiation of protein synthesis under lactic acid stress. Primary rat astrocyte cultures exposed to pH 5.25 underwent cell death and a strong inhibition of protein synthesis assessed by [3H]methionine incorporation, which was solely due to acidity of the extracellular medium and was not related to lactate concentrations.

Group I metabotropic glutamate receptors activate the p70S6 kinase via both mammalian target of rapamycin (mTOR) and extracellular signal-regulated kinase (ERK 1/2) signaling pathways in rat striatal and hippocampal synaptoneurosomes.

Group I metabotropic glutamate receptors (mGluRs) have been demonstrated to play a role in synaptic plasticity via a rapamycin-sensitive mRNA translation signaling pathway. Various growth factors can stimulate this pathway, leading to the phosphorylation and activation of mammalian target of rapamycin (mTOR), a serine/threonine protein kinase that modulates the activity of several translation regulatory factors, such as p70S6 kinase. However, little is known about the cellular and molecular mechanisms that bring the plastic changes of synaptic transmission after stimulation of group I mGluRs.

Production of two vaccinating recombinant rotavirus proteins in the milk of transgenic rabbits.

Rotaviruses are the main cause of infantile viral gastroenteritis worldwide leading to approximately 500,000 deaths each year mostly in the developing world. For unknown reasons, live attenuated viruses used in classical vaccine strategies were shown to be responsible for intussusception (a bowel obstruction). New strategies allowing production of safe recombinant non-replicating rotavirus candidate vaccine are thus clearly needed.

Lactic acidosis stimulates ganglioside and ceramide generation without sphingomyelin hydrolysis in rat cortical astrocytes.

Acidosis is a ubiquitous feature of cerebral ischemia, and triggers a cascade of biochemical events that results in neuronal injury. The purpose of this study was to evaluate the effects of lactic acidosis on the ganglioside composition, the ceramide and sphingomyelin (SM) levels in rat cortical astrocytes. Primary astrocyte cultures were exposed to lactic acid (pH 5.

The up-regulation of the striatal dopamine transporter's activity by cAMP is PKA-, CaMK II- and phosphatase-dependent.

The neuronal dopamine transporter (DAT) is a presynaptic plasma membrane protein mediating the re-uptake of dopamine released from synaptic cleft into the nerve terminals. While the regulation of its activity by protein kinase C signalling is well-characterized, there is controversial debate about its regulation by protein kinase A (PKA) signalling. In rat striatal synaptosomes, we showed that a cell-permeable cyclic adenosine 3',5'-monophosphate analogue up-regulated the DAT capacity without modification of its efficiency.

Effect of ischemia on TBARS and lactate production in several cerebral regions of anaesthetised and awake rats.

The premise of neuroprotective therapy for acute ischemic stroke is based upon the possibility to interfere with the cellular ischemic cascade, so the understanding of the mechanisms and consequences of cerebral ischemia is necessary. The relationship between lipid peroxidation and acidosis was investigated in several regions of rat brain following ischemia without reperfusion. Male Wistar rats (280-300 g) were anaesthetised (Ketalar 33 mg/kg and Rompun 6.

DHA-enriched phospholipid diets modulate age-related alterations in rat hippocampus.

Our previous work on rat hippocampus showed that a loss of docosahexaenoic acid (DHA) occurs in the fatty acid composition of phosphatidylethanolamine (PE), plasmenylethanolamine (PmE) and phosphatidylserine (PS) with increasing age. The present study investigated whether a DHA-enriched phospholipid dietary supplement could restore DHA levels and cholinergic activity. Male rats were fed a balanced diet containing both linoleic and alpha-linolenic acids until the age of 2, 18 and 21 months.

Induction of heat shock proteins (HSPs) by sodium arsenite in cultured astrocytes and reduction of hydrogen peroxide-induced cell death.

Induction of heat shock proteins (HSPs) protects cells from oxidative injury. Here Hsp72, Hsp27 and heme oxygenase-1 (HO-1) were induced in cultured rat astrocytes, and protection against oxidative stress was investigated. Astrocytes were treated with sodium arsenite (20-50 micro m) for 1 h, which was non-toxic to cells, 24 h later they were exposed to 400 micro m H2O2 for 1 h, and cell death was evaluated at different time points.

Sulfatide and GM1 ganglioside modulate the high-affinity dopamine uptake in rat striatal synaptosomes: evidence for the involvement of their ionic charges.

The present study was undertaken to examine the effects of the anionic glycolipids GM1 ganglioside and sulfatide on the high-affinity dopamine (DA) uptake in rat striatal synaptosomes. After 1h of incubation, GM1 stably bound to synaptosomes and modified the activity of the neuronal dopamine transporter (DAT). With 1.

Aluminum L-glutamate complex in rat brain cortex: in vivo prevention of aluminum deposit by magnesium D-aspartate.

Our previous experiments in the rat showed that aluminum L-glutamate complex (Al L-Glu) crosses the blood-brain barrier and accumulates in selective brain areas and that Al salts may increase D-aspartic acid forms in living brain proteins, probably by inducing more thermodynamically stable structures than L isomers. As magnesium blocks NMDA receptors, D-aspartic acid was used in the present study in the form of magnesium salt to prevent the excitotoxicity of dicarboxylic amino acids. Effects on brain amino acids and Al cortex levels in mature rats were studied after chronic treatment with Al L-Glu or Na L-Glu alone or in association with magnesium D-aspartate (Mg D-Asp).

Impairment of the neuronal dopamine transporter activity in MPP(+)-treated rat was not prevented by treatments with nitric oxide synthase or poly(ADP-ribose) polymerase inhibitors.

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes, via its metabolite MPP(+), damages of the nigrostriatal dopaminergic pathway, similar to those observed in Parkinson's disease. An intranigral injection of 10 microg MPP(+) in rat induced a decrease of about 30% of the neuronal dopamine transporter (DAT) activity 21 days after lesion. Based on the hypothesis that MPTP/MPP(+) neurotoxicity involves the nitric oxide (NO) production and/or an activation of poly(ADP-ribose) polymerase (PARP), we investigated the preventive effects of a treatment either with L-Name, a NO synthase (NOS) inhibitor or 3-aminobenzamide, a PARP inhibitor on the reduction of dopamine uptake induced by MPP(+).

Evidence against a major role of plasmalogens in the resistance of astrocytes in lactic acid-induced oxidative stress in vitro.

Astrocytes are known to play a key role in buffering extracellular pH variations and, in addition, they are particularly resistant to oxidative stress and subsequent lipid peroxidation. This great resistance may be ascribed to the presence of high concentrations of certain antioxidants, but another explanation may be the presence of a high quantity of plasmalogens, which are a special group of glycerophospholipids characterized by a vinyl ether bond instead of an ester bond in the sn-1 position of the glycerol backbone. Plasmalogens are sensitive to free radical attack and acidity, and numerous works have supported the hypothesis that they may be antioxidant molecules that protect cells from oxidative stress.

Age-related changes in ethanolamine glycerophospholipid fatty acid levels in rat frontal cortex and hippocampus.

Morphological and biochemical alterations are associated with a progressive age-related cognitive deficit. Plasmenylethanolamine, the major brain plasmalogen, may be modified during aging because of a possible antioxidant role and involvement in synaptic transmission. Two- and 18-month-old rats were used to study the effect of aging on the levels and acyl composition of plasmenylethanolamine (PmE), phosphatidylethanolamine (PE), and phosphatidylserine (PS) in the frontal cortex and hippocampus.

Non-thermal effects of continuous 2.45 GHz microwaves on Fas-induced apoptosis in human Jurkat T-cell line.

Non-thermal effects of microwaves (MWs) are one of the main issues studied for revising standards. The effects of MW exposure on apoptosis at non-thermal level (48 h, 2.45 GHz, 5 mW/cm2) have been studied.

Synthesis and antioxidant activity of new tetraarylpyrroles.

The synthesis and in vitro antioxidant activity of 17 new tetraarylpyrroles are investigated by 2 tests highly documented in the literature: capability to prevent Fe(2+)-induced lipid peroxidation on microsomes, which is a membrane preparation rich in polyunsaturated fatty acids, and direct scavenging effect on a stable free radical, 1,l-diphenyl-2-picryl-hydrazyl (DPPH). For the Fe(2+)-induced microsomal lipid peroxidation system, the results show that molecules which possess 2-pyrazinyl or 2-pyridyl in the 3- and 4-positions on the pyrrole ring are the most efficient. Introduction of methoxy groups on the phenyl ring in the 2- and 5-positions increases the effects but the higher activity is obtained with 2-furyl or 2-thienyl.

Origin of 4-hydroxynonenal incubation-induced inhibition of dopamine transporter and Na+/K+ adenosine triphosphate in rat striatal synaptosomes.

Previous experiments reported that an incubation of striatal synaptosomes with 4-hydroxynonenal (4-HNE) resulted in an inhibition of dopamine (DA) uptake and Na+/K+ adenosine triphosphate (ATPase) activity. The present work investigated whether theses inhibitions are related to a 4-HNE binding to the DA transporter (DAT) and the Na+/K+ ATPase. The number of specific [125I]-PE21 binding sites on the DAT was significantly reduced after incubation with 4-HNE.

Origin of extracellular dopamine increase induced by lactic acid striatal perfusion monitored by microdialysis in the awake rat.

In previous studies we showed that a striatal lactic acid perfusion-induced lactacidosis produces a diphasic increase in extracellular dopamine (DA). In the present study, different pharmacological reagents were used to determine the origin of accumulated DA. Our data show that both DA accumulations were totally suppressed by tetrodotoxin and nicardipine, indicating a relationship with membrane depolarization and a Ca(2+)-dependent effect.

Lactic acid-induced increase of extracellular dopamine measured by microdialysis in rat striatum: evidence for glutamatergic and oxidative mechanisms.

Striatal lactacidosis was induced by direct lactic acid perfusion to obtain a local pH as close as possible to that observed in ischemia. In a previous study we showed that such lactacidosis produces a diphasic increase in extracellular dopamine (DA). The present work investigated whether DA accumulation is related to a glutamatergic mechanism and/or production of reactive oxygen species (ROS) in the striatum.

[Tox-Didact:CD-ROM for toxicology education. Value in hospital toxicology].

New teaching techniques should allow students more independence in their training, particularly in learning from problems and using clinical reasoning. We designed Tox-Didact, a modular multimedia educational software program, which is suitable for both students and professionals, regardless of their orientation (pharmacy or medicine) or level. Each module concerns four domains: diagnosis, biological monitoring, curative treatment and prevention.