The Experts below are selected from a list of 696 Experts worldwide ranked by ideXlab platform
Om P Mishra - One of the best experts on this subject based on the ideXlab platform.
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effect of 7 nitroindazole sodium on the cellular distribution of neuronal nitric oxide synthase in the cerebral cortex of hypoxic newborn piglets
Neurochemical Research, 2006Co-Authors: Christos D Katsetos, Karen I Fritz, Nehal A Parikh, Agustin Legido, Maria Delivoriapapadopoulos, Om P MishraAbstract:Cerebral hypoxia results in generation of nitric oxide (NO) free radicals by Ca++-dependent activation of neuronal nitric oxide synthase (nNOS). The present study tests the hypothesis that the hypoxia-induced increased expression of nNOS in cortical neurons is mediated by NO. To test this hypothesis the cellular distribution of nNOS was determined immunohistochemically in the cerebral cortex of hypoxic newborn piglets with and without prior exposure to the selective nNOS inhibitor 7-nitroindazole sodium (7-NINA). Studies were conducted in newborn piglets, divided into normoxic (n = 6), normoxic treated with 7-NINA (n = 6), hypoxic (n = 6) and hypoxic pretreated with 7-NINA (n = 6). Hypoxia was induced by lowering the FiO2 to 0.05–0.07 for 1 h. Cerebral tissue hypoxia was documented by decrease of ATP and phosphocreatine levels in both the hypoxic and 7-NINA pretreated hypoxic groups (P < 0.01). An increase in the number of nNOS immunoreactive neurons was observed in the frontal and parietal cortex of the hypoxic as compared to the normoxic groups (P < 0.05) which was attenuated by pretreatment with 7-NINA (P < 0.05 versus hypoxic). 7-NINA affected neither the cerebral energy metabolism nor the cellular distribution of nNOS in the cerebral cortex of normoxic animals. We conclude that nNOS expression in cortical neurons of hypoxic newborn piglets is NO-mediated. We speculate that nNOS inhibition by 7-NINA will protect against hypoxia-induced NO-mediated neuronal death.
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nitric oxide mediated expression of bax protein and dna fragmentation during hypoxia in neuronal nuclei from newborn piglets
Brain Research, 2002Co-Authors: Alan B Zubrow, Qazi M Ashraf, Juan R Ballesteros, Karen I Fritz, Maria Delivoriapapadopoulos, Om P MishraAbstract:The present study tests the hypothesis that nitric oxide mediates the hypoxia-induced increase in expression of Bax and in DNA fragmentation in the cerebral cortex of newborn piglets, and that administration of N-nitro-l-arginine (NNLA), a nitric oxide synthase inhibitor, will prevent a change in hypoxia-induced expression of apoptotic genes and DNA damage. Piglets were assigned to normoxic, hypoxic, or NNLA-pretreated hypoxic groups. Cerebral tissue hypoxia was documented biochemically by measuring ATP and phosphocreatine (PCr) levels. Cerebral cortical neuronal nuclei were isolated and nuclear proteins were separated electrophoretically and probed with specific antibodies against Bcl-2 or Bax proteins. Neuronal nuclear DNA from normoxic, hypoxic, and NNLA-pretreated hypoxic animals was isolated, separated by electrophoresis on 1% agarose gel and stained with ethidium bromide. Cerebral hypoxia resulted in an increase in nuclear membrane Bax protein levels from 121.33±47.7 optical density (OD)×mm2 in normoxic to 273.67±67.3 OD×mm2 in hypoxic group (P<0.05 vs. normoxic), but levels in NNLA-pretreated hypoxic group were 155.78±48.3 OD×mm2 (P<0.05 vs. hypoxic, P=NS vs. normoxic). Similarly, cerebral hypoxia resulted in the density of DNA fragments increasing from 1530.3±309.8 OD/mm2 in the normoxic group to 5383.3±775 OD/mm2 in the hypoxic group (P<0.05), while levels in NNLA-pretreated hypoxic group were 3574.0±952 OD/mm2 (P<0.05 compared to hypoxic and normoxic groups). The data show that NNLA-pretreatment prevents the hypoxia-induced increase in Bax expression and DNA fragmentation demonstrating that the hypoxia-induced Bax gene expression and the DNA fragmentation are NO-mediated.
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effect of in utero hypoxia on the ouabain strophanthidin binding site of the fetal guinea pig brain cell membrane na k atpase
Neuroscience Letters, 1995Co-Authors: Ernie Graham, Om P Mishra, Maria DelivoriapapadopoulosAbstract:This study investigates the effect of hypoxia on the high affinity strophanthidin/ouabain binding site of brain cell membrane Na+,K+-ATPase in 30, 45 and 60 day (term) fetal guinea pigs. Studies were performed on 30 fetuses randomized to either normoxic or hypoxic conditions. The hypoxic fetuses were exposed to maternal hypoxia (FiO2 = 7%) for 60 min. Brain cell membrane fractions were prepared, and the rate of ATP hydrolysis was determined at varying concentrations of strophanthidin. In every experiment with 45 and 60 day brain preparations hypoxia caused a leftward shift in the IC50, but this did not reach the level of statistical significance (4.0 × 10−5 normoxic, 9.0 × 10−6 hypoxic, P = 0.069, at 45 days; 9.5 × 10−6 M normoxic, 8.5 × 10−6 M hypoxic, P = 0.23, at 60 days). If hypoxia does cause a true left shift this would indicate greater sensitivity of the hypoxic brain to inhibitor. In addition, [3H]ouabain binding studies were performed. In the 30 day normoxic brain preparations, the Kd was 24.7 ± 5.6 nM, and the Bmax was 0.26 ± 0.08 pmol/mg protein. At 45 days the ouabain binding sites showed no change in affinity following hypoxia (Kd = 14.6 ± 1.7 nM normoxic, 13.0 ± 0.8 nM hypoxic, P = NS); however, there was a significant decrease in receptor number following hypoxia (Bmax = 22.1 ± 2.2 pmol/mg protein normoxic, 16.9 ± 0.3 pmol/mg protein hypoxic, P < 0.05). In 60 day hypoxic brain, ouabain binding sites showed a significant decrease in Kd (Kd = 213.3 ± 39.0 nM normoxic, 161.1 ± 33.6 nM hypoxic, P < 0.05) reflecting an increased affinity, and a significant decrease in Bmax (154.7 ± 61.6 pmol/mg protein normoxic, 76.0 ± 28.5 pmol/mg protein, hypoxic, P = 0.02). At 45 days only Bmax is changed by hypoxia, indicating that following hypoxia, there are fewer enzyme molecules, but the remaining molecules are not affected. Term brain Na+,K+-ATPase molecules are even more sensitive to hypoxia, with hypoxia resulting in a decrease in both Bmax and Kd. This suggests that a term not only are there fewer enzyme molecules following hypoxia, but that remaining molecules are modified as well.
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protective effect of mgso4 infusion on nmda receptor binding characteristics during cerebral cortical hypoxia in the newborn piglet
Brain Research, 1994Co-Authors: David J Hoffman, Om P Mishra, Peter J Marro, Jane E Mcgowan, Maria DelivoriapapadopoulosAbstract:This study tests the hypothesis that magnesium, a selective non-competitive antagonist of the NMDA receptor, will attenuate hypoxia-induced alteration in NMDA receptors and preserve MK-801 binding characteristics during cerebral hypoxia in vivo. Anesthetized, ventilated and instrumented newborn piglets were divided into three groups: normoxic controls were compared to untreated hypoxic and Mg(2+)-treated hypoxic piglets. Cerebral hypoxia was induced by lowering the FiO2 to 5-7% and confirmed biochemically by a decrease in the levels of phosphocreatine (82% lower than control). The Mg(2+)-treated group received MgSO4 600 mg/kg over 30 min followed by 300 mg/kg administered during 60 min of hypoxia. Plasma Mg2+ concentrations increased from 1.6 +/- 0.1 mg/dl to 17.7 +/- 3.3 mg/dl. 3H-MK-801 binding was used as an index of NMDA receptor modification. The Bmax in control, hypoxic and Mg(2+)-treated hypoxic piglets was 1.09 +/- 0.17, 0.70 +/- 0.25 and 0.96 +/- 0.14 pmoles/mg protein, respectively. The Kd for the same groups were 10.02 +/- 2.04, 4.88 +/- 1.43 and 8.71 +/- 2.23 nM, respectively. The Bmax and Kd in the hypoxic group were significantly lower compared to the control and Mg(2+)-treated hypoxic groups, indicating a preservation of NMDA receptor number and affinity for MK-801 during hypoxia with Mg2+. The activity of Na+, K+ ATPase, a marker of neuronal membrane function, was lower in the hypoxic group compared to the control and Mg(2+)-treated hypoxic groups. These findings show that MgSO4 prevents the hypoxia-induced modification of the NMDA receptor and attenuates neuronal membrane dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)
Richard P. Hill - One of the best experts on this subject based on the ideXlab platform.
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hypoxia and metabolism hypoxia dna repair and genetic instability
Nature Reviews Cancer, 2008Co-Authors: Robert G Bristow, Richard P. HillAbstract:Intratumoural hypoxia is a negative prognostic indicator and can underlie therapeutic resistance for many patients. This Review explores the differential biological effects of acute hypoxia versus longer-term, chronic hypoxia on genomic instability and DNA damage repair pathways. What does this mean for therapeutic strategies? Areas of hypoxic tumour tissue are known to be resistant to treatment and are associated with a poor clinical prognosis. There are several reasons why this might be, including the capacity of hypoxia to drive genomic instability and alter DNA damage repair pathways. Significantly, current models fail to distinguish between the complexities of the hypoxic microenvironment and the biological effects of acute hypoxia exposures versus longer-term, chronic hypoxia exposures on the transcription and translation of proteins involved in genetic stability and cell survival. Acute and chronic hypoxia might lead to different biology within the tumour and this might have a direct effect on the design of new therapies for the treatment of hypoxic tumours.
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hypoxia and metabolism hypoxia dna repair and genetic instability
Nature Reviews Cancer, 2008Co-Authors: Robert G Bristow, Richard P. HillAbstract:Areas of hypoxic tumour tissue are known to be resistant to treatment and are associated with a poor clinical prognosis. There are several reasons why this might be, including the capacity of hypoxia to drive genomic instability and alter DNA damage repair pathways. Significantly, current models fail to distinguish between the complexities of the hypoxic microenvironment and the biological effects of acute hypoxia exposures versus longer-term, chronic hypoxia exposures on the transcription and translation of proteins involved in genetic stability and cell survival. Acute and chronic hypoxia might lead to different biology within the tumour and this might have a direct effect on the design of new therapies for the treatment of hypoxic tumours.
Zhong Yun - One of the best experts on this subject based on the ideXlab platform.
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the anti protozoan drug nifurtimox preferentially inhibits clonogenic tumor cells under hypoxic conditions
American Journal of Cancer Research, 2017Co-Authors: Qun Lin, Hoon Kim, Zhong YunAbstract:Tumor hypoxia is an independent prognostic indicator of tumor malignant progression and poor patient survival. Therefore, eradication of hypoxic tumor cells is of paramount importance for successful disease control. In this study, we have made a new discovery that nifurtimox, a clinically approved drug to treat Chagas disease caused by the parasitic protozoan trypanosomes, can function as a hypoxia-activated cytotoxin. We have found that nifurtimox preferentially kill clonogenic tumor cells especially under the hypoxic conditions of ≤0.1% O2. Mechanistically, nifurtimox becomes activated after tumor cells enter into a fully hypoxic state, as shown by the stabilization of the Hypoxia-Inducible Factor 1α (HIF-1α). Nifurtimox specifically induces the formation of 53BP1 foci, a hallmark of DNA double-stranded breaks, in hypoxic tumor cells. Hypoxia-dependent activation of nifurtimox involves P450 (cytochrome) oxidoreductase. The anti-protozoan drug nifurtimox holds promise as a new hypoxia-activated cytotoxin with the potential to preferentially eliminates severely hypoxic tumor cells.
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hypoxia activated cytotoxicity of benznidazole against clonogenic tumor cells
Cancer Biology & Therapy, 2016Co-Authors: Qun Lin, Zhong YunAbstract:Solid tumors contain numerous regions with insufficient oxygen concentrations, a condition termed hypoxia. Tumor hypoxia is significantly associated with metastasis, refractory to conventional cancer therapies, and poor patient survival. Therefore, eradication of hypoxic tumor cells will likely have significant impact on the overall progression-free patient survival. This article reports a new discovery that Benznidazole, a bioreductive drug currently used to treat Chagas disease caused by the parasitic protozoan Trypanosoma cruzi, is activated by hypoxia and can kill clonogenic tumor cells especially those under severe hypoxic conditions (≤0.1 % O2). This type of hypoxia selectivity is important in that severely hypoxic tumor microenvironment is where tumor cells exhibit the strongest resistance to therapy. Mechanistically, activation of Benznidazole coincides with the stabilization of the Hypoxia-Inducible Factor 1α (HIF-1α), suggesting that Benznidazole is activated after tumor cells have entered into a fully hypoxic state. Under such hypoxic conditions, Benznidazole induces the formation of 53BP1 foci, a hallmark of DNA double-stranded breaks that can cause clonogenic inhibition or cell death. These results demonstrate that Benznidazole is a hypoxia-activated cytotoxin with the potential to specifically eliminate hypoxic tumor cells.
Candice D Fike - One of the best experts on this subject based on the ideXlab platform.
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l citrulline ameliorates chronic hypoxia induced pulmonary hypertension in newborn piglets
American Journal of Physiology-lung Cellular and Molecular Physiology, 2009Co-Authors: Madhumita Ananthakrishnan, Frederick E Barr, Marshall L Summar, Heidi A B Smith, Mark R Kaplowitz, Gary Cunningham, Jordan A Magarik, Yongmei Zhang, Candice D FikeAbstract:Newborn piglets develop pulmonary hypertension and have diminished pulmonary vascular nitric oxide (NO) production when exposed to chronic hypoxia. NO is produced by endothelial NO synthase (eNOS) in the pulmonary vascular endothelium using l-arginine as a substrate and producing l-citrulline as a byproduct. l-Citrulline is metabolized to l-arginine by two enzymes that are colocated with eNOS in pulmonary vascular endothelial cells. The purpose of this study was to determine whether oral supplementation with l-citrulline during exposure of newborn piglets to 10 days of chronic hypoxia would prevent the development of pulmonary hypertension and increase pulmonary NO production. A total of 17 hypoxic and 17 normoxic control piglets were studied. Six of the 17 hypoxic piglets were supplemented with oral l-citrulline starting on the first day of hypoxia. l-Citrulline supplementation was provided orally twice a day. After 10 days of hypoxia or normoxia, the animals were anesthetized, hemodynamic measurements were performed, and the lungs were perfused in situ. Pulmonary arterial pressure and pulmonary vascular resistance were significantly lower in hypoxic animals treated with l-citrulline compared with untreated hypoxic animals (P < 0.001). In vivo exhaled NO production (P = 0.03) and nitrite/nitrate accumulation in the perfusate of isolated lungs (P = 0.04) were significantly higher in l-citrulline-treated hypoxic animals compared with untreated hypoxic animals. l-Citrulline supplementation ameliorated the development of pulmonary hypertension and increased NO production in piglets exposed to chronic hypoxia. We speculate that l-citrulline may benefit neonates exposed to prolonged periods of hypoxia from cardiac or pulmonary causes.
Maria Delivoriapapadopoulos - One of the best experts on this subject based on the ideXlab platform.
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effect of 7 nitroindazole sodium on the cellular distribution of neuronal nitric oxide synthase in the cerebral cortex of hypoxic newborn piglets
Neurochemical Research, 2006Co-Authors: Christos D Katsetos, Karen I Fritz, Nehal A Parikh, Agustin Legido, Maria Delivoriapapadopoulos, Om P MishraAbstract:Cerebral hypoxia results in generation of nitric oxide (NO) free radicals by Ca++-dependent activation of neuronal nitric oxide synthase (nNOS). The present study tests the hypothesis that the hypoxia-induced increased expression of nNOS in cortical neurons is mediated by NO. To test this hypothesis the cellular distribution of nNOS was determined immunohistochemically in the cerebral cortex of hypoxic newborn piglets with and without prior exposure to the selective nNOS inhibitor 7-nitroindazole sodium (7-NINA). Studies were conducted in newborn piglets, divided into normoxic (n = 6), normoxic treated with 7-NINA (n = 6), hypoxic (n = 6) and hypoxic pretreated with 7-NINA (n = 6). Hypoxia was induced by lowering the FiO2 to 0.05–0.07 for 1 h. Cerebral tissue hypoxia was documented by decrease of ATP and phosphocreatine levels in both the hypoxic and 7-NINA pretreated hypoxic groups (P < 0.01). An increase in the number of nNOS immunoreactive neurons was observed in the frontal and parietal cortex of the hypoxic as compared to the normoxic groups (P < 0.05) which was attenuated by pretreatment with 7-NINA (P < 0.05 versus hypoxic). 7-NINA affected neither the cerebral energy metabolism nor the cellular distribution of nNOS in the cerebral cortex of normoxic animals. We conclude that nNOS expression in cortical neurons of hypoxic newborn piglets is NO-mediated. We speculate that nNOS inhibition by 7-NINA will protect against hypoxia-induced NO-mediated neuronal death.
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nitric oxide mediated expression of bax protein and dna fragmentation during hypoxia in neuronal nuclei from newborn piglets
Brain Research, 2002Co-Authors: Alan B Zubrow, Qazi M Ashraf, Juan R Ballesteros, Karen I Fritz, Maria Delivoriapapadopoulos, Om P MishraAbstract:The present study tests the hypothesis that nitric oxide mediates the hypoxia-induced increase in expression of Bax and in DNA fragmentation in the cerebral cortex of newborn piglets, and that administration of N-nitro-l-arginine (NNLA), a nitric oxide synthase inhibitor, will prevent a change in hypoxia-induced expression of apoptotic genes and DNA damage. Piglets were assigned to normoxic, hypoxic, or NNLA-pretreated hypoxic groups. Cerebral tissue hypoxia was documented biochemically by measuring ATP and phosphocreatine (PCr) levels. Cerebral cortical neuronal nuclei were isolated and nuclear proteins were separated electrophoretically and probed with specific antibodies against Bcl-2 or Bax proteins. Neuronal nuclear DNA from normoxic, hypoxic, and NNLA-pretreated hypoxic animals was isolated, separated by electrophoresis on 1% agarose gel and stained with ethidium bromide. Cerebral hypoxia resulted in an increase in nuclear membrane Bax protein levels from 121.33±47.7 optical density (OD)×mm2 in normoxic to 273.67±67.3 OD×mm2 in hypoxic group (P<0.05 vs. normoxic), but levels in NNLA-pretreated hypoxic group were 155.78±48.3 OD×mm2 (P<0.05 vs. hypoxic, P=NS vs. normoxic). Similarly, cerebral hypoxia resulted in the density of DNA fragments increasing from 1530.3±309.8 OD/mm2 in the normoxic group to 5383.3±775 OD/mm2 in the hypoxic group (P<0.05), while levels in NNLA-pretreated hypoxic group were 3574.0±952 OD/mm2 (P<0.05 compared to hypoxic and normoxic groups). The data show that NNLA-pretreatment prevents the hypoxia-induced increase in Bax expression and DNA fragmentation demonstrating that the hypoxia-induced Bax gene expression and the DNA fragmentation are NO-mediated.
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effect of in utero hypoxia on the ouabain strophanthidin binding site of the fetal guinea pig brain cell membrane na k atpase
Neuroscience Letters, 1995Co-Authors: Ernie Graham, Om P Mishra, Maria DelivoriapapadopoulosAbstract:This study investigates the effect of hypoxia on the high affinity strophanthidin/ouabain binding site of brain cell membrane Na+,K+-ATPase in 30, 45 and 60 day (term) fetal guinea pigs. Studies were performed on 30 fetuses randomized to either normoxic or hypoxic conditions. The hypoxic fetuses were exposed to maternal hypoxia (FiO2 = 7%) for 60 min. Brain cell membrane fractions were prepared, and the rate of ATP hydrolysis was determined at varying concentrations of strophanthidin. In every experiment with 45 and 60 day brain preparations hypoxia caused a leftward shift in the IC50, but this did not reach the level of statistical significance (4.0 × 10−5 normoxic, 9.0 × 10−6 hypoxic, P = 0.069, at 45 days; 9.5 × 10−6 M normoxic, 8.5 × 10−6 M hypoxic, P = 0.23, at 60 days). If hypoxia does cause a true left shift this would indicate greater sensitivity of the hypoxic brain to inhibitor. In addition, [3H]ouabain binding studies were performed. In the 30 day normoxic brain preparations, the Kd was 24.7 ± 5.6 nM, and the Bmax was 0.26 ± 0.08 pmol/mg protein. At 45 days the ouabain binding sites showed no change in affinity following hypoxia (Kd = 14.6 ± 1.7 nM normoxic, 13.0 ± 0.8 nM hypoxic, P = NS); however, there was a significant decrease in receptor number following hypoxia (Bmax = 22.1 ± 2.2 pmol/mg protein normoxic, 16.9 ± 0.3 pmol/mg protein hypoxic, P < 0.05). In 60 day hypoxic brain, ouabain binding sites showed a significant decrease in Kd (Kd = 213.3 ± 39.0 nM normoxic, 161.1 ± 33.6 nM hypoxic, P < 0.05) reflecting an increased affinity, and a significant decrease in Bmax (154.7 ± 61.6 pmol/mg protein normoxic, 76.0 ± 28.5 pmol/mg protein, hypoxic, P = 0.02). At 45 days only Bmax is changed by hypoxia, indicating that following hypoxia, there are fewer enzyme molecules, but the remaining molecules are not affected. Term brain Na+,K+-ATPase molecules are even more sensitive to hypoxia, with hypoxia resulting in a decrease in both Bmax and Kd. This suggests that a term not only are there fewer enzyme molecules following hypoxia, but that remaining molecules are modified as well.
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protective effect of mgso4 infusion on nmda receptor binding characteristics during cerebral cortical hypoxia in the newborn piglet
Brain Research, 1994Co-Authors: David J Hoffman, Om P Mishra, Peter J Marro, Jane E Mcgowan, Maria DelivoriapapadopoulosAbstract:This study tests the hypothesis that magnesium, a selective non-competitive antagonist of the NMDA receptor, will attenuate hypoxia-induced alteration in NMDA receptors and preserve MK-801 binding characteristics during cerebral hypoxia in vivo. Anesthetized, ventilated and instrumented newborn piglets were divided into three groups: normoxic controls were compared to untreated hypoxic and Mg(2+)-treated hypoxic piglets. Cerebral hypoxia was induced by lowering the FiO2 to 5-7% and confirmed biochemically by a decrease in the levels of phosphocreatine (82% lower than control). The Mg(2+)-treated group received MgSO4 600 mg/kg over 30 min followed by 300 mg/kg administered during 60 min of hypoxia. Plasma Mg2+ concentrations increased from 1.6 +/- 0.1 mg/dl to 17.7 +/- 3.3 mg/dl. 3H-MK-801 binding was used as an index of NMDA receptor modification. The Bmax in control, hypoxic and Mg(2+)-treated hypoxic piglets was 1.09 +/- 0.17, 0.70 +/- 0.25 and 0.96 +/- 0.14 pmoles/mg protein, respectively. The Kd for the same groups were 10.02 +/- 2.04, 4.88 +/- 1.43 and 8.71 +/- 2.23 nM, respectively. The Bmax and Kd in the hypoxic group were significantly lower compared to the control and Mg(2+)-treated hypoxic groups, indicating a preservation of NMDA receptor number and affinity for MK-801 during hypoxia with Mg2+. The activity of Na+, K+ ATPase, a marker of neuronal membrane function, was lower in the hypoxic group compared to the control and Mg(2+)-treated hypoxic groups. These findings show that MgSO4 prevents the hypoxia-induced modification of the NMDA receptor and attenuates neuronal membrane dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)
