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Biomedical subjects

C Yardin

Publications and source records attributed to C Yardin.

14 recordsLinked to original sources
PubMed2000

N-methyl-D-aspartate receptor blockade enhances neuronal apoptosis induced by serum deprivation.

Neuronal apoptosis a hallmark of brain development could also be involved in neurodegenerative diseases. Glutamate toxicity is widely proposed as an important factor in the pathogenesis of neurological disorders. We show here that, in rat primary cortical cultures, the blockade of N-methyl-D-aspartate (NMDA) glutamate receptors exacerbated neuronal apoptosis induced by serum deprivation. This effect is observed at early stage of cultures (9 days in vitro (DIV)) and mildly decreases in more mature cultures (13 and 15 DIV). At the opposite, low concentrations of NMDA (5 microM) or glutamate (5 microM) prevented the neuronal apoptosis induced by trophic support withdrawal. In primary cortical cultures, the proapoptotic effect of trophic support removal can be modulated by NMDA receptors depending upon the magnitude of these glutamate receptor activation.

Animals↗
PubMed1998

Mild kainate toxicity produces selective motoneuron death with marked activation of CA(2+)-permeable AMPA/kainate receptors.

Motoneuron death could be produced by higher sensitivity to excitoxicity during the development and pathological conditions. We report here that in ventral spinal cord cultures mild kainate exposure (12.5 microM, 20 min or 100 microM, 2.5 min) induced selective cobalt stain of motoneurons, indicating a specific Ca2+ entry through the Ca(2+)-permeable AMPA/kainate receptors. This result was associated with a selective motoneuron death as previously described. In these cultures, motoneuron immunoreactivity for the Ca2+ buffering protein, calretinin was negative. These findings suggest that the selective motoneuron death due to a mild excitotoxic insult could be linked to a marked Ca2+ influx associated with the lack of some Ca2+ buffering proteins.

Animals↗
PubMed1998

Brefeldin A-induced apoptosis is expressed in rat neurons with dephosphorylated tau protein.

Brefeldin A (BFA) is a fungus metabolite (penicillum brefeldanum) that is known to produce the disintegration of the Golgi apparatus in exposed cells, and apoptosis in various cancer cells. This study reports that in rat primary cortical cell cultures BFA also produces apoptosis assessed by the TUNEL method and DAPI (4',6-diemidino-2-phenylindole) staining. The percentages of apoptotic neurons range from 26.9% +/- 8.3 to 43.2 +/- 2.5% in cultures exposed from 4 to 8 h to BFA (10 microg/ml). A double fluorescent staining, using AT8 antibody (phosphorylated tau) or tau1 antibody (dephosphorylated tau) associated with DAPI labeling reveals that tau1 positive neurons are more sensitive to BFA-induced apoptosis compared to AT8 positive neurons. This result and previous results using other apoptosis inducers suggest that tau phosphorylation in the vicinity of the AT8-tau1 epitopes is a marker of resistance or sensitivity to neuronal apoptosis in rat cortical cell cultures.

Adrenal Cortex↗
PubMed1998

FK506 antagonizes apoptosis and c-jun protein expression in neuronal cultures.

FK506 is an immunosuppressive drug that binds to FK506 binding protein (FKBPs), a subgroup of cytosolic proteins called immunophillins. Previous works have revealed that FK506 protects neural cells from ischemia or excitotoxicity. Here we report that FK506 (10(-6) M) and not cyclosporine A (10(-6) M) blocks neuronal apoptosis induced by serum deprivation in rat neuronal cultures. In addition the immunohistochemical staining of C-jun protein in deprived cultures is markedly attenuated by FK506. The proportion of C-jun-positive neurons in control cultures, in serum-deprived cultures (48 h) and in serum-deprived cultures exposed to FK506 (10(-6) M) were 12.5%, 56.5% and 16.5%, respectively. The down-regulation of C-jun could play a major role in the anti-apoptotic action of FK506 in stressed neuronal cultures.

Animals↗
PubMed1998

Neuronal apoptosis is associated with a decrease in tau mRNA expression.

Apoptosis is a programmed cell death that occurs during the development of the nervous system and in neurodegenerative disorders. Tau protein is a microtubule-associated protein which promotes microtubule polymerization and stabilization. Apoptosis was induced in primary neuronal cultures by glutamate exposure (200 microM, 15 min) or by serum deprivation, and tau mRNA levels were studied by quantitative in situ hybridization in apoptotic and non apoptotic neurons. Compared to controls, tau mRNA expression was decreased in apoptotic neurons produced by excitotoxicity or trophic support withdrawal. Under these conditions, resistant neurons to apoptosis display either increased tau mRNA levels after glutamate exposure or a stable tau mRNA expression after serum deprivation. In conclusion, in this in vitro model, neurons which are resistant and sensitive to apoptosis can be differentiated according to tau mRNA expression.

Animals↗
PubMed1997

NMDA induces apoptosis and necrosis in neuronal cultures. Increased APP immunoreactivity is linked to apoptotic cells.

In rat neuronal cultures exposed for a prolonged period (16 h) to a low concentration of N-methyl-D-aspartate (NMDA; 20 microM) two different types of neuronal death were observed, necrosis and apoptosis. The immunocytochemical study of necrotic neurons revealed the absence of amyloid precursor protein (APP) labeling in the cytoplasmic region. In contrast, neuronal apoptosis was associated with an increase in cytoplasmic APP immunoreactivity. In addition, the presence of extracellular APP was also detected around some apoptotic neurons, suggesting that apoptosis could contribute to the presence of extracellular APP.

Amyloid beta-Protein Precursor↗
PubMed1997

Cultured neurons expressing phosphorylated tau are more resistant to apoptosis induced by NMDA or serum deprivation.

Apoptosis is a programmed cell death that occurs during the development of the nervous system and in neurodegenerative disorders. Tau protein is a cytoskeletal component that promotes microtubule polymerization and stabilization. Apoptosis was induced in primary neuronal cultures by a prolonged exposure (16 h) to the NMDA (N-methyl-D-aspartate 20 microM) or by serum deprivation. The percentages of apoptotic neurons expressing phosphorylated tau (AT8) immunoreactivity are comparable in control and NMDA-exposed cultures (7.5 +/- 1.9 and 6.9 +/- 1.9%, respectively). At the opposite, the percentage of apoptotic neurons expressing de-phosphorylated tau (tau 1) immunolabelings is dramatically increased in NMDA-treated cultures (X 2.3 of controls). Similar results were also observed 48 h after serum deprivation. These results demonstrate in vitro that under these conditions, resistant and sensitive cortical neurons to apoptosis can be partly differentiated according to their phosphorylated tau immunoreactivities.

Animals↗
PubMed1997

Identical chromosome imbalance in two siblings born to a mother with a double reciprocal translocation.

We report the case of a woman who carried two reciprocal translocations. Her karyotype was 46,XX,t(3;12)(q12;q21)(4;17)(p14;p13). She had two children, a phenotypically normal daughter (karyotype (46,XX,t(3;12)(q12;q21)) and a son with partial 4p trisomy (karyotype 46,XY,t(3;12) (q12;q21),-17,+maternal der(17)). She was pregnant with a female fetus who had the same karyotype as her son. She also reported a history of two spontaneous abortions. This viable recurrent abnormality was due to the maternal (4;17) translocation with meiotic segregation type 2:2 adjacent 1. In this case of the two reciprocal translocations carried by the mother, one led to imbalances, whereas the other remained balanced in the viable offspring.

Adult↗
PubMed1996

Modifications of neuronal phosphorylated tau immunoreactivity induced by NMDA toxicity.

Glutamate toxicity has been involved in the pathophysiology of a large variety of neurodegenerative disorders. Tau Protein is a micro-tubule-associated protein that promotes microtubule polymerization and stabilization. Phosphorylated tau protein accumulates in paired helical neurofilaments, the major constituent of neurofibrillary tangles observed in the brain of patients suffering from Alzheimer disease (AD). In this study, using confocal laser microscopy and immunoblot analysis, we report that acute (500 mu M for 15 min) or chronic (20 mu M for 16 h) N-methyl-D-aspartate (NMDA) neuronal toxicities modify the immunoreactivity of phosphorylated tau. Neuronal degeneration produced by N-methyl-D-aspartate is associated with an augmented immunolabeling of phosphorylated tau proteins at serine 202 (AT8 antibody) as observed in paired helical neurofilaments. This finding could help to determine the cellular mechanisms at the origin of neuronal degeneration associated with modifications of phosphorylated tau immunoreactivity produced by receptor-mediated extracellular signals.

Alzheimer Disease↗
PubMed1996

Link between peripheral neuropathy and monoclonal dysglobulinemia: a study of 66 cases.

The association of peripheral neuropathy (PN) and monoclonal dysglobulinemia has often been reported, although a direct link between the two is not readily established. Linkage is generally based on consideration of the clinical, electrophysiological and immunological findings along with details of the course. We report here a study of 66 of our own cases which benefitted from immunological and immunopathological analyses of serum. In 62 of these cases, histological and immunopathological examinations of nerve biopsy specimens were realized. Such a discussion about a link between the dysglobulinemia and the peripheral neuropathy is of clinical interest as it provides information for decisions about the continuation of potentially neurotoxic chemotherapy. In this prospective study conducted on a case by case basis, the origin of the neuropathy, whether due to the chemotherapy, the dysimmune process, the presence of abnormal immunoglobulins in the nerve, amyloid deposits, infiltration of nerve parenchyme by abnormal cells, or a combination of one or more of these mechanisms, could be determined in most cases. We divided our population of 66 patients into 4 etiological groups: group 1: direct link (56.1%), group 2: indirect link (12.7%), group 3: no link (10.6%), group 4: doubtful link (21.2%). In group 1 we found a statistically significant association between the peripheral neuropathy and an IgM kappa MGUS.

Humans↗
PubMed1994

Glutamate increases tau phosphorylation in primary neuronal cultures from fetal rat cerebral cortex.

Tau proteins are microtubule-associated proteins which promote microtubule polymerisation and stabilization. AT8 is a new monoclonal antibody raised against a phosphorylated Tau protein probably at Serine 202. Tau protein, recognized by AT8 antibody is present in fetal human and rat brains, and in Alzheimer's brains. Here we report that glutamate an excitatory neurotransmitter and also a potent excitotoxin produces in primary neuronal cultures a rapid increase in phosphorylated Tau protein immunoreactivity using AT8 antibody. Glutamate augments neuronal Tau immunoreactivity by 225% using laser confocal immunocytochemistry and by 355% on immunoblot analysis. This experimental model of Tau protein modifications could help to decipher the intracellular biochemical pathways at the origin of phosphorylated Tau protein.

Animals↗
PubMed1994

Prevention of HIV coat protein (gp120) toxicity in cortical cell cultures by riluzole.

Neurological complications observed in HIV-infected patients are very frequent. Neocortical lesions include reduced neuronal density due to neuronal degeneration. The HIV envelope protein gp120 has potent neurotoxic properties in cell cultures blocked either by NMDA antagonists or calcium channel antagonists. Moreover, human monocytoid cell lines infected by HIV release endogenous toxic factors with comparable cellular actions. We have analysed the effects of riluzole, a compound reducing the excitatory amino acid release on gp120-induced neurotoxicity in primary neuronal cultures. Riluzole, which blocks the release of glutamate and aspartate from nerve terminals, prevents (10(-7) M) the neuronal degeneration produced by 20 pM of gp120 in cortical cell cultures. This result could suggest that toxic factors produced by activated macrophages might increase glutamate release, and that this may be prevented by riluzole.

Animals↗
PubMed1994

Synaptophysin expression during in vitro neuronal differentiation. An immunocytochemical and a confocal laser microscopic study.

Primary neuronal cultures from mammalian fetal brains are widely used for morphological, biochemical and pharmacotoxicological studies. The usefulness of relatively pure neuronal cultures are now demonstrated for such studies. We have compared the neuronal survival and differentiation, the synaptophysin expression and the glial cell percentage in primary neuronal cultures using two different media: a M1 medium containing 10 % fetal calf serum and a M2 medium supplemented with hormones, ions and chemicals. Our study demonstrates that the M2 medium (a serum-free defined medium) is associated with an increased survival at 14 days of culture, an earlier neuronal differentiation and synaptophysin expression in cell bodies and neurites as it was confirmed by immunocytochemical and confocal laser microscopic studies.

Animals↗