Close Window. Close Window. Thank you for choosing to subscribe to the eTOC for Pediatric Researc... more Close Window. Close Window. Thank you for choosing to subscribe to the eTOC for Pediatric Research. Enter your Email address: Wolters Kluwer Health may email you for journal alerts and information, but is committed to maintaining ...
International journal of developmental neuroscience : the official journal of the International Society for Developmental Neuroscience, 1999
Glutamate NMDA receptor has been implicated in brain developmental processes as well as in excito... more Glutamate NMDA receptor has been implicated in brain developmental processes as well as in excitotoxicity and seizure mediation. A previous study has shown that an acute episode of seizures for 30 min in rats altered NMDA receptor characteristics, mainly in the very immature animal. In order to assess whether receptor modifications may also account for long-lasting cerebral disabilities, medium- and long-term consequences of repeated seizures in developing rats on brain NMDA receptor properties were investigated. Seizures were induced once a day for 3 consecutive days, either from post-natal day 5 (P5) to P7 or from P15 to P17. NMDA receptors were then analysed at P15, P25 and P60 (adulthood) by measuring specific binding of [3H]MK-801 on brain membrane preparations. In addition, allosteric modulation of NMDA receptors by exogenous glutamate and glycine was investigated. Seizures from P5 to P7 led to a 22% increase in the density of [3H]MK-801 binding sites measured at P15, but did ...
Severe hypoxia was shown to induce apoptotic death in developing brain neurons, whereas mild hypo... more Severe hypoxia was shown to induce apoptotic death in developing brain neurons, whereas mild hypoxia was demonstrated to stimulate neurogenesis. Since the apoptotic process may share common pathways with mitosis, expression profiles of proteins involved in apoptosis or the cell cycle were analyzed by immunohistochemistry and/or western blotting, in relation with cell outcome of cultured neurons from fetal rat forebrain subjected to either lethal (6 h) or non-lethal (3 h) hypoxia (95% N(2)/5% CO(2)). Hypoxia for 6 h led to apoptosis that was inhibited by the cell cycle blocker olomoucine. Transient overexpression of proliferating cell nuclear antigen was followed by increasing expression of p53, p21, Bax and caspases, whereas Bcl-2 and heat shock proteins were progressively repressed. Conversely, a 3-h hypoxic insult initiated neuronal mitosis, with increased thymidine incorporation. In these conditions, levels of proliferating cell nuclear antigen, Rb, Bcl-2 and heat shock proteins were persistently elevated, while expression of p53, p21, Bax and caspases gradually decreased. These data confirm that hypoxia promotes cell cycle activation, whatever the stress intensity. This process is then aborted following apoptosis-inducing hypoxia, whereas sublethal insult would trigger neurogenesis, at least in developing brain neurons in vitro, by stimulating timed expression of neurogenic and survival-associated proteins.
Gestational methyl donor deficiency (MDD) leads to growth retardation as well as to cognitive and... more Gestational methyl donor deficiency (MDD) leads to growth retardation as well as to cognitive and motor disorders in 21-d-old rat pups. These disorders are related to impaired neurogenesis in the cerebral neurogenic areas. Olfactory bulbs (OB), the main target of neuronal progenitors originating from the subventricular zone, play a critical role during the postnatal period by allowing the pups to identify maternal odour. We hypothesised that growth retardation could result from impaired suckling due to impaired olfactory discrimination through imbalanced apoptosis/neurogenesis in the OB. Since neurosteroidogenesis modulates neurogenesis in OB, in the present study, we investigated whether altered neurosteroidogenesis could explain some these effects. Pups born to dams fed a normal diet (n 24) and a MDD diet (n 27) were subjected to olfactory tests during the lactation and weaning periods (n 24 and 20, respectively). We studied the markers of apoptosis/neurogenesis and the expression levels of the key neurosteroidogenic enzyme aromatase, the cholesterol-transfer protein StAR (steroidogenic acute regulatory protein) and the ERα oestrogen receptor and the content of oestradiol in OB. The 21-d-old MDD female pups displayed lower body weight and impaired olfactory discrimination when compared with the control pups. MDD led to greater homocysteine accumulation and more pronounced apoptosis, along with impaired cell proliferation in the OB of female pups. The expression levels of aromatase, StAR and ERα as well as the content of oestradiol were lower in the OB of the MDD female pups than in those of the control female pups. In conclusion, gestational MDD may alter olfactory discrimination performances by affecting neurogenesis, apoptosis and neurosteroidogenesis in OB in a sex-dependent manner. It may be involved in growth retardation through impaired suckling.
Previous work has shown that 6h-hypoxia followed by reoxygenation for up to 96h induces delayed a... more Previous work has shown that 6h-hypoxia followed by reoxygenation for up to 96h induces delayed apoptotic death through changes in synthesis of specific proteins in cultured neurons from the fetal rat forebrain (Pediatr Res, 1997, 41: 289A). The inducible AP-1 ...
Both hypoxia and bilirubin are common risk factors in newborns, which may act synergistically to ... more Both hypoxia and bilirubin are common risk factors in newborns, which may act synergistically to produce anatomical and functional disturbances of the CNS. Using primary cultures of neurons from the fetal rat brain, it was recently reported that neuronal apoptosis accounts for the deleterious consequences of these two insults. To investigate the influence of hypoxia, bilirubin, or their combination on the outcome of neuronal cells of the immature brain, and delineate cellular mechanisms involved, 6-d-old cultured neurons were submitted to either hypoxia (6 h), unconjugated bilirubin (0.5 microM), or to combined conditions. Within 96 h, cell viability was reduced by 22.7% and 24.5% by hypoxia and bilirubin, respectively, whereas combined treatments decreased vital score by 34%. Nuclear morphology revealed 13.4% of apoptotic cells after hypoxia, 16.2% after bilirubin, and 22.6% after both treatments. Bilirubin action was specifically blocked by the glutamate receptor antagonist MK-801, which was without effect on the consequences of hypoxia. Temporal changes in [(3)H]leucine incorporation rates as well as beneficial effects of cycloheximide reflected a programmed phenomenon dependent upon synthesis of selective proteins. The presence of bilirubin reduced hypoxia-induced alterations of cell energy metabolism, as reflected by 2-D-[(3)H]deoxyglucose incorporation, raising the question of free radical scavenging. Measurements of intracellular radical generation, however, failed to confirm the antioxidant role of bilirubin. Taken together, our data suggest that low levels of bilirubin may enhance hypoxia effects in immature neurons by facilitating glutamate-mediated apoptosis through the activation of N:-methyl-D-aspartate receptors.
In order to further analyze the development of glutamatergic pathways in neuronal cells, the expr... more In order to further analyze the development of glutamatergic pathways in neuronal cells, the expression of excitatory amino acid receptors was studied in a model of neurons in primary culture by measuring the specific binding of L-[3H]glutamate under various incubation conditions in 8-day-old intact living neurons isolated from the embryonic rat forebrain, as well as in membrane preparations from these cultures and from newborn rat forebrain. In addition, the receptor responsiveness to glutamate was assessed by studying the uptake of tetraphenylphosphonium (TPP+) which reflects membrane polarization. In the presence of a potent inhibitor of glutamate uptake, the radioligand bound to a total number of sites of 36.7 pmol/mg protein in intact cells incubated in a Tris buffer containing Na+, Ca2+, and Cl-, with a Kd around 2 microM. In the absence of the above ions, [3H]glutamate specific binding diminished to 14.2 pmol/mg protein with a Kd-value of 550 nM. Under both of the above conditions, similar Kd were obtained in membranes isolated from cultures and from the newborn brain. However, Bmax-values were significantly lower in culture membranes than in intact cells or newborn membranes. Displacement studies showed that NMDA was the most potent compound to inhibit [3H]glutamate binding in membranes obtained from cultured neurons as well as from the newborn brain, whereas quisqualate, AMPA, kainate and trans-ACPD were equally effective.(ABSTRACT TRUNCATED AT 250 WORDS)
The regional distribution of c-fos mRNA in the mouse brain has been investigated by in situ hybri... more The regional distribution of c-fos mRNA in the mouse brain has been investigated by in situ hybridization autoradiography after seizures induced by an acute electroconvulsive shock (ECS). ECS led to a widespread induction of the proto-oncogene c-fos in the brain, with highest concentrations in discrete areas within the limbic system and also in the hypothalamus and cerebellum. The mild stress of sham treatment in earclipped animals induced a weaker and qualitatively different pattern of c-fos mRNA expression involving the cortex, hippocampus, and cerebellum. These data suggest the usefulness of c-fos in situ hybridization as a marker of neuronal stimulation and in mapping a range of effects from a mild stress to the robust changes of an electroconvulsive seizure.
Close Window. Close Window. Thank you for choosing to subscribe to the eTOC for Pediatric Researc... more Close Window. Close Window. Thank you for choosing to subscribe to the eTOC for Pediatric Research. Enter your Email address: Wolters Kluwer Health may email you for journal alerts and information, but is committed to maintaining ...
International journal of developmental neuroscience : the official journal of the International Society for Developmental Neuroscience, 1999
Glutamate NMDA receptor has been implicated in brain developmental processes as well as in excito... more Glutamate NMDA receptor has been implicated in brain developmental processes as well as in excitotoxicity and seizure mediation. A previous study has shown that an acute episode of seizures for 30 min in rats altered NMDA receptor characteristics, mainly in the very immature animal. In order to assess whether receptor modifications may also account for long-lasting cerebral disabilities, medium- and long-term consequences of repeated seizures in developing rats on brain NMDA receptor properties were investigated. Seizures were induced once a day for 3 consecutive days, either from post-natal day 5 (P5) to P7 or from P15 to P17. NMDA receptors were then analysed at P15, P25 and P60 (adulthood) by measuring specific binding of [3H]MK-801 on brain membrane preparations. In addition, allosteric modulation of NMDA receptors by exogenous glutamate and glycine was investigated. Seizures from P5 to P7 led to a 22% increase in the density of [3H]MK-801 binding sites measured at P15, but did ...
Severe hypoxia was shown to induce apoptotic death in developing brain neurons, whereas mild hypo... more Severe hypoxia was shown to induce apoptotic death in developing brain neurons, whereas mild hypoxia was demonstrated to stimulate neurogenesis. Since the apoptotic process may share common pathways with mitosis, expression profiles of proteins involved in apoptosis or the cell cycle were analyzed by immunohistochemistry and/or western blotting, in relation with cell outcome of cultured neurons from fetal rat forebrain subjected to either lethal (6 h) or non-lethal (3 h) hypoxia (95% N(2)/5% CO(2)). Hypoxia for 6 h led to apoptosis that was inhibited by the cell cycle blocker olomoucine. Transient overexpression of proliferating cell nuclear antigen was followed by increasing expression of p53, p21, Bax and caspases, whereas Bcl-2 and heat shock proteins were progressively repressed. Conversely, a 3-h hypoxic insult initiated neuronal mitosis, with increased thymidine incorporation. In these conditions, levels of proliferating cell nuclear antigen, Rb, Bcl-2 and heat shock proteins were persistently elevated, while expression of p53, p21, Bax and caspases gradually decreased. These data confirm that hypoxia promotes cell cycle activation, whatever the stress intensity. This process is then aborted following apoptosis-inducing hypoxia, whereas sublethal insult would trigger neurogenesis, at least in developing brain neurons in vitro, by stimulating timed expression of neurogenic and survival-associated proteins.
Gestational methyl donor deficiency (MDD) leads to growth retardation as well as to cognitive and... more Gestational methyl donor deficiency (MDD) leads to growth retardation as well as to cognitive and motor disorders in 21-d-old rat pups. These disorders are related to impaired neurogenesis in the cerebral neurogenic areas. Olfactory bulbs (OB), the main target of neuronal progenitors originating from the subventricular zone, play a critical role during the postnatal period by allowing the pups to identify maternal odour. We hypothesised that growth retardation could result from impaired suckling due to impaired olfactory discrimination through imbalanced apoptosis/neurogenesis in the OB. Since neurosteroidogenesis modulates neurogenesis in OB, in the present study, we investigated whether altered neurosteroidogenesis could explain some these effects. Pups born to dams fed a normal diet (n 24) and a MDD diet (n 27) were subjected to olfactory tests during the lactation and weaning periods (n 24 and 20, respectively). We studied the markers of apoptosis/neurogenesis and the expression levels of the key neurosteroidogenic enzyme aromatase, the cholesterol-transfer protein StAR (steroidogenic acute regulatory protein) and the ERα oestrogen receptor and the content of oestradiol in OB. The 21-d-old MDD female pups displayed lower body weight and impaired olfactory discrimination when compared with the control pups. MDD led to greater homocysteine accumulation and more pronounced apoptosis, along with impaired cell proliferation in the OB of female pups. The expression levels of aromatase, StAR and ERα as well as the content of oestradiol were lower in the OB of the MDD female pups than in those of the control female pups. In conclusion, gestational MDD may alter olfactory discrimination performances by affecting neurogenesis, apoptosis and neurosteroidogenesis in OB in a sex-dependent manner. It may be involved in growth retardation through impaired suckling.
Previous work has shown that 6h-hypoxia followed by reoxygenation for up to 96h induces delayed a... more Previous work has shown that 6h-hypoxia followed by reoxygenation for up to 96h induces delayed apoptotic death through changes in synthesis of specific proteins in cultured neurons from the fetal rat forebrain (Pediatr Res, 1997, 41: 289A). The inducible AP-1 ...
Both hypoxia and bilirubin are common risk factors in newborns, which may act synergistically to ... more Both hypoxia and bilirubin are common risk factors in newborns, which may act synergistically to produce anatomical and functional disturbances of the CNS. Using primary cultures of neurons from the fetal rat brain, it was recently reported that neuronal apoptosis accounts for the deleterious consequences of these two insults. To investigate the influence of hypoxia, bilirubin, or their combination on the outcome of neuronal cells of the immature brain, and delineate cellular mechanisms involved, 6-d-old cultured neurons were submitted to either hypoxia (6 h), unconjugated bilirubin (0.5 microM), or to combined conditions. Within 96 h, cell viability was reduced by 22.7% and 24.5% by hypoxia and bilirubin, respectively, whereas combined treatments decreased vital score by 34%. Nuclear morphology revealed 13.4% of apoptotic cells after hypoxia, 16.2% after bilirubin, and 22.6% after both treatments. Bilirubin action was specifically blocked by the glutamate receptor antagonist MK-801, which was without effect on the consequences of hypoxia. Temporal changes in [(3)H]leucine incorporation rates as well as beneficial effects of cycloheximide reflected a programmed phenomenon dependent upon synthesis of selective proteins. The presence of bilirubin reduced hypoxia-induced alterations of cell energy metabolism, as reflected by 2-D-[(3)H]deoxyglucose incorporation, raising the question of free radical scavenging. Measurements of intracellular radical generation, however, failed to confirm the antioxidant role of bilirubin. Taken together, our data suggest that low levels of bilirubin may enhance hypoxia effects in immature neurons by facilitating glutamate-mediated apoptosis through the activation of N:-methyl-D-aspartate receptors.
In order to further analyze the development of glutamatergic pathways in neuronal cells, the expr... more In order to further analyze the development of glutamatergic pathways in neuronal cells, the expression of excitatory amino acid receptors was studied in a model of neurons in primary culture by measuring the specific binding of L-[3H]glutamate under various incubation conditions in 8-day-old intact living neurons isolated from the embryonic rat forebrain, as well as in membrane preparations from these cultures and from newborn rat forebrain. In addition, the receptor responsiveness to glutamate was assessed by studying the uptake of tetraphenylphosphonium (TPP+) which reflects membrane polarization. In the presence of a potent inhibitor of glutamate uptake, the radioligand bound to a total number of sites of 36.7 pmol/mg protein in intact cells incubated in a Tris buffer containing Na+, Ca2+, and Cl-, with a Kd around 2 microM. In the absence of the above ions, [3H]glutamate specific binding diminished to 14.2 pmol/mg protein with a Kd-value of 550 nM. Under both of the above conditions, similar Kd were obtained in membranes isolated from cultures and from the newborn brain. However, Bmax-values were significantly lower in culture membranes than in intact cells or newborn membranes. Displacement studies showed that NMDA was the most potent compound to inhibit [3H]glutamate binding in membranes obtained from cultured neurons as well as from the newborn brain, whereas quisqualate, AMPA, kainate and trans-ACPD were equally effective.(ABSTRACT TRUNCATED AT 250 WORDS)
The regional distribution of c-fos mRNA in the mouse brain has been investigated by in situ hybri... more The regional distribution of c-fos mRNA in the mouse brain has been investigated by in situ hybridization autoradiography after seizures induced by an acute electroconvulsive shock (ECS). ECS led to a widespread induction of the proto-oncogene c-fos in the brain, with highest concentrations in discrete areas within the limbic system and also in the hypothalamus and cerebellum. The mild stress of sham treatment in earclipped animals induced a weaker and qualitatively different pattern of c-fos mRNA expression involving the cortex, hippocampus, and cerebellum. These data suggest the usefulness of c-fos in situ hybridization as a marker of neuronal stimulation and in mapping a range of effects from a mild stress to the robust changes of an electroconvulsive seizure.
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