Hypoxic Control Group Research Articles

Protective effects of novel single compound, Hirsutine on hypoxic neonatal rat cardiomyocytes

Uncaria rhynchophylla is a traditional Chinese herb that has been applied in China for treatment of ailments of the cardiovascular system, but little is known about its active constituents and effect in cardiomyocytes. In present study, we investigated the cardioprotective effect of 0.1 μΜ, 1 μΜ and 10 μΜ Hirsutine isolated from the methanolic extracts of Uncaria rhynchophylla by high performance liquid chromatography (HPLC) on neonatal rat cardiomyocytes treated with hypoxia to determine the mechanism underlying the protective effect with regard to cardiac anti-oxidant enzymes and apoptosis genes. Hirsutine significantly increased the viability of cardiomyocytes injured by hypoxia. Gene expression levels of proapoptotic genes (Bax, Fas and caspase-3) were significantly downregulated compared with the hypoxic control group (P < 0.05), whereas the expression level of Bcl-2 was upregulated following Hirsutine treatment (P < 0.05). Correspondingly, Hirsutine treatment increased Bcl-2 protein level and decreased Bax protein level. Assay investigating cardiac anti-oxidant enzymes provided further evidence for the protective effect of Hirsutine, as indicated by the induction of the anti-oxidant enzymes superoxide dismutase. The results of present study suggest that the mechanism of action of Hirsutine in hypoxic neonatal rat cardiomyocytes may be related to its anti-oxidant and anti-apoptotic properties. This may open an avenue for developing novel candidate compounds with cardioprotective effect from unique Chinese plant.

Interaction Between Intermittent Hypoxia and Sprint Interval Training on Efficiency and Economy

VO2max, efficiency and economy play important roles in endurance performance. These improvements have been elicited separately through endurance and sprint interval training (SIT) and intermittent hypoxic exposure (IHE). However, there is limited data of the interaction of SIT and IHE on endurance performance. PURPOSE: To compare the effects of IHE, SIT, and a combination of IHE/SIT on VO2max and submaximum energy costs. METHODS: 20 healthy male subjects (age: 26 ± 4yrs, ht: 179 ± 7cm, wt: 85 ± 18kg, VO2max: 52.32±14.32ml/kg/min) were split into 4 groups for a 2 wk training study. The 4 groups consisted of a normoxic control group (NC) (n=5), a normoxic training group (NST) (n=5), an intermittent hypoxic control group (IHC) (n=5) and an intermittent hypoxic training group (IHST) (n=5). All volunteers spent ∼ 10 days within 12 day period in a hypoxic enclosure. The IHE and normoxic conditions were blinded to the participants. The intermittent hypoxic and normoxic groups were exposed for 3 hours to a simulated altitude of 90.34 ± 1.35 mmHg and ∼149 mmHg PiO2, respectively. The training groups performed 6 SIT sessions on a cycle ergometer over a 2 wk period. Each SIT session included 4-7 × 30 second all out sprints with a resistance of 7.5% of body weight. Hypoxic or normoxic exposure was conducted immediately after each SIT session. Pre and post maximal (1min incremental ramp) and submaximal cycle ergometer tests (60 min @ 10% below ventilatory threshold) were conducted 1 wk before and after the last IHE or normoxic exposure. The following variables were measured: VO2max, gross efficiency (GEF), net efficiency (NEF) and economy (EC). A mixed model repeated measures ANOVA was used to analyze the differences between IHE, SIT and IHST. RESULTS: Post intervention, there were no significant effects between the 4 groups for VO2max (p=0.307), GEF (p=0.207), NEF (p=0.349), and EC (p=0.349). CONCLUSION: Two weeks of IHE, SIT or IHST does not have a significant effect on VO2max, GEF, NEF or EC. Therefore, 2 wks of IHE to a simulated altitude of ∼4000 m nor 2 wks of sprint interval training; or a combination of the two training interventions are ineffective in improving VO2max or submaximum energy costs in males with above average fitness.

Redundant Mechanisms for Vascular Growth Factors in Retinopathy of Prematurity in vitro

Background: Current treatments for retinopathy of prematurity (ROP) targeting single vascular growth factors are ineffective in preventing neoangiogenesis. Methods: We investigated the redundant/compensatory mechanisms between vascular growth factors in ROP. Cultured retinal vascular endothelial cells under CoCl₂-induced hypoxia were transfected with recombinant adeno-associated virus type 2-vascular endothelial growth factor (VEGF) or pGIPZ-VEGF RNA interference to up- and downregulate VEGF expression, respectively. At 48 h after transfection, basic fibroblast growth factor (bFGF) and angiopoietin 1 (ANG1) gene expression as well as mitotic cycle changes were analyzed in the cells and correlated with the change in VEGF expression. Results: Compared with the normal control group 1, at 30 min, 12 h and 24 h, the expressions of VEGF, bFGF and ANG1 in the hypoxia control group 2 were significantly higher. In the highly expressing VEGF group (group 3), the expressions of bFGF and ANG1 were downregulated, while in the low-expressing VEGF group 4, the expressions of bFGF and ANG1 were significantly upregulated. In the bevacizumab treatment group 5, the expressions of VEGF, bFGF and ANG1 were similar to those in group 2, and the difference was not significant. Conclusions: A compensatory mechanism (redundancy) exists between vascular growth factors in ROP. Such a phenomenon could partially explain why the inhibition of a single growth factor cannot effectively prevent the recurrence of neovascularization in ROP. A more effective strategy for treating ROP may be to inhibit VEGF and its redundant pathways.

Effects of Tan IIA on expression of HIF-la and c-Met in gastric cancer SGC7901 cells under hypoxia

Objective To study the effects of Tan Ⅱ A on the expression of c-Met and HIF-lα in gastric cancer SGC7901 cells under hypoxia and the correlation between c-Met and HIF-lα expression. Methods The model of hypoxia was established by CoCl2. There were three groups; normal control group, hypoxia control group, and hypoxia combined with different concentrations of Tan ⅡA group. After Tan ⅡA was added to the media with 0.5, 2.0 and 10.0 mg/L respectively for 48 h under hypoxia, the expression of HIF-1α and c-Met protein was detected by immunocytochemical staining. Results Immunocytochemical staining revealed that the expression of HIF-1α and c-Met protein was inhibited by Tan ⅡA in a dose-dependent manner under hypoxia. High positive correlation was found between the expression of HIF-1α and c-Met (n = 4, r = 0. 996, P <0.01). Conclusion Tan ⅡA might inhibit the expression of c-Met protein via down-regulation of HIFlα protein expression under hypoxia, suggesting that Tan ⅡA might play an important role in fighting against hypoxia-stimulated invasion and metastasis of tumor. Key words: Stomach neoplasms ; Tanshinone Ⅱ A ; Anoxia ; Hypoxia-inducible factor 1 ;

The effects of HIF-1alpha on gene expression profiles of NCI-H446 human small cell lung cancer cells

BackgroundGene targeted therapy refers to any therapy focused on one of the many biological features of the tumor. Such features are mediated by specific genes that are involved in tumor metastasis, recurrence, poor response to chemotherapy and others. Hypoxia is an important pathognomonic feature of many malignant tumors including SCLC (small cell lung cancer). HIF-1alpha, which is induced by hypoxia, is the most important regulatory factor of many specific genes that can influence the biological features of tumors.MethodsIn this study, we tried to elucidate the changes in gene expression profiles of SCLC NCI-H446 cells mediated by HIF-1alpha. According to different treatments of cells, three experimental pairwise comparisons were designed: hypoxia group vs. control group, Ad5-HIF-1alpha group vs. Ad5 group, and Ad5-siHIF-1 alpha group Vs Ad5 group.ResultsResults from the analysis of gene expression profiles indicated that there were 65 genes upregulated and 28 genes downregulated more than two-fold in all three experimental pairwise comparisons. These genes were involved in transport, signal-transduction, cell adhesion/motility, growth factor/cytokines, transcription, inflammatory response, metabolic process, in addition to others. SOCS1, IGFBP5, IL-6 and STAT3 were also upregulated at protein level. SOCS1 could significantly induce apoptosis and suppress growth of NCI-H446 cells but HIF-1alpha could induce growth and suppress apoptosis.ConclusionsThrough this research, we are trying to find novel functional genes that are mediated by HIF-1alpha and provide the theoretical basis for new therapeutic targets. HIF-1 alpha maybe upregulate the expression of SOCS1 through mediation of STAT3 and IL-6. In addition, SOCS1 could significantly induce apoptosis and suppress growth of NCI-H446 cells. This was contrary to HIF-1alpha and it indicated that there might be an antagonism effect between HIF-1alpha and SOCS1 on regulating growth and apoptosis of NCI-H446 cells.

Cerebral Amino Acid Profiles after Hypoxia-Reoxygenation and N-Acetylcysteine Treatment in the Newborn Piglet

Background: Neonatal hypoxia-ischemia (HI) is a common clinical occurrence. Recently, much evidence has been gathered to suggest that oxygen free radicals are implicated in the pathogenesis of hypoxia-reoxygenation injury through the initiation and propagation of toxic cascades including glutamate excitotoxicity and the manifestation of post-HI neurologic disorders. Following HI, excessive free radicals are formed and antioxidant defenses are diminished. N-acetylcysteine (NAC) is a clinically available antioxidant and has been previously shown to reduce oxidative stress and scavenge free radicals in multiple models of brain injury. Objectives: Using an acutely instrumented swine model of neonatal hypoxia-reoxygenation, the objective of the present study was to examine the neurochemical effects of NAC administration in 5 brain regions exquisitely vulnerable to severe hypoxia. Methods: In a blinded fashion, newborn piglets (1–4 d, 1.4–2.2 kg) were block randomized into surgical sham (SHAM), hypoxic control (HC) and NAC-treated (H-NAC) groups. Both HC and H-NAC piglets were subject to 2 h of alveolar hypoxia (paO₂ = 20–40 mm Hg) and then resuscitated with 100% O₂for 1 h followed by 21% for an additional 3 h. Results: Our results show that two hours of severe hypoxemia causes metabolic acidosis and significant changes in cerebral amino acids including glutamate, aspartate and alanine, in all brain regions investigated including the cortex, basal ganglia and thalamus. The administration of NAC 10 min into the reoxygenation period and subsequently continued as an infusion, maintains post-resuscitation amino acid neurochemistry at the levels observed in SHAM piglets. Conclusions: In newborn piglets that have sustained brain injury related to hypoxia/reoxygenation, the administration of NAC does not disrupt cerebral amino acid balance and maintains cerebral amino acid homeostasis.

PROTECTIVE EFFECTS OF LEONURINE IN NEONATAL RAT HYPOXIC CARDIOMYOCYTES AND RAT INFARCTED HEART

1. Previous studies have shown that extracts of Herba leonuri, predominantly containing the phytochemical components leonurine and stachydrine, provide protective effects in the ischaemic myocardium by acting as free radical scavengers and inhibiting the formation of reactive oxygen species. 2. The present study was designed to investigate the cardioprotective effects of 10(-6) mol/L leonurine on neonatal rat cardiomyocytes treated with hypoxia plus serum deprivation, a component of ischaemia, and to determine the mechanisms underlying the protective effects with regard to cardiac anti-oxidant enzymes and apoptosis genes. Cardiomyocytes were treated with leonurine 8 h prior to exposure to hypoxia. In addition, we investigated the effects of 7.5 and 15 mg/kg leonurine, administered to rats i.p. for 7 days prior to left coronary artery ligation, on subsequent infarct size of the ischaemic heart. 3. Leonurine significantly increased the viability of cardiomyocytes injured by hypoxia. In the leonurine-treated group, gene expression levels of pro-apoptotic genes, namely Bax and Fas, were significantly downregulated (by 0.95- and 0.72-fold, respectively; P < 0.001) compared with the hypoxic control group, whereas the expression of Bcl-2 and Bcl-xl was upregulated following leonurine treatment (by 1.03- and 1.07-fold, respectively; P < 0.05). Correspondingly, leonurine treatment increased Bcl-2 protein levels and decreased Bax protein levels. Assays investigating cardiac anti-oxidant enzymes provided further evidence for a protective effect of leonurine, as indicated by the induction of the anti-oxidant enzymes superoxide dismutase and catalase. Furthermore, leonurine decreased infarct size in ischaemic rat heart. 4. The results of the present study suggest that the mechanisms of action of leonurine in hypoxic neonatal rat cardiomyocytes and infarcted rat heart may be related to its anti-oxidant and anti-apoptotic properties.

Effects of N-Acetylcysteine on Intestinal Reoxygenation Injury in Hypoxic Newborn Piglets Resuscitated with 100% Oxygen

Background: Neonatal asphyxia may lead to the development of ischemia-reperfusion induced intestinal injury, which is related to oxygen-derived free radical production. N-Acetylcysteine (NAC) is a thiol-containing antioxidant which increases intracellular stores of glutathione. Objectives: Using a swine model of neonatal hypoxia-reoxygenation, we examined whether administration of NAC after resuscitation improved intestinal perfusion and reduced intestinal damage. Methods: Twenty-four piglets (1–4 days old, 1.4–2.2 kg) were anesthetized and acutely instrumented for continuous monitoring of superior mesenteric arterial flow and oxygen delivery. Alveolar hypoxia was induced for 2 h, followed by resuscitation with 100% oxygen for 1 h and 21% oxygen for 3 h. Animals were randomized to sham-operated, hypoxic control and NAC treatment (150 mg/kg i.v. at 0 or 10 min of reoxygenation followed by infusion 100 mg/kg/h) groups. During hypoxia-reoxygenation, intestinal tissue glutathione content, caspase-3 activity and reoxygenation injury were examined. Results: After 2 h of hypoxia, piglets were acidotic and hypotensive, with significantly depressed blood flow and oxygen delivery to the small intestine. Upon reoxygenation, hemodynamics recovered as did oxygen supply to the small intestine. After 4 h of reoxygenation, the NAC treatment improved mesenteric flow and oxygen delivery. Despite reducing the increase in caspase-3 activities after hypoxia-reoxygenation by NAC treatment, no significant differences in the glutathione content and histological grading of ileal injury were found among the experimental groups. Conclusions: In newborn piglets with hypoxia-reoxygenation, NAC may improve mesenteric blood flow and oxygen delivery without significant effect on tissue glutathione content. The protective role of NAC in the reoxygenated intestine after severe hypoxia warrants further investigation.

Carbon dioxide directly suppresses spontaneous migration, chemotaxis, and free radical production of human neutrophils

Carbon dioxide (CO(2)) insufflation during laparoscopy has been shown to dampen the systemic stress response to surgery. This is related to a suppression of peritoneal macrophage functions. In vivo data suggest that CO(2) can also affect neutrophils (polymorphonuclear cells, PMNs), the most abundant cell type in the inflamed peritoneal cavity. Nonetheless, the direct effects of CO(2) on PMNs have not yet been investigated. PMNs were isolated from peripheral blood of healthy volunteers and incubated with (1) CO(2) (100% CO(2), pH 6.2), (2) hypoxic control (95% helium/5% CO(2), pH 7.4), and (3) control (95% air/5% CO(2), pH 7.4). Spontaneous and IL-8-induced migrations (chemokinesis and chemotaxis) during 2 h of exposure to different gases were measured with a transwell chamber system. The release of reactive oxygen species (ROS, luminometry) was determined after 15-min and 2-h exposures. In other sets of experiments, PMNs were exposed for 2 h or 4 h and kept under normal conditions for 18 h with lipopolysaccharide (LPS) stimulation thereafter. Final viability and apoptosis were assessed with fluorometry. Exposure to 100% CO(2) completely blocked spontaneous and IL-8 induced migration of PMNs (p < 0.001 vs. controls). Neutrophil migration was slightly diminished in the hypoxic control group. PMA-stimulated ROS production was reduced even after short exposure to 100% CO(2)(p < 0.05). We observed a slight increase of caspase-3/7 activity after exposure to 100% CO(2) and/or hypoxia; however, total viability was not affected. CO(2) incubation directly and temporarily suppresses the proinflammatory functions of PMNs; this is caused only partially by the concomitant hypoxia. This effect will contribute to the dampened inflammatory response to laparoscopic surgery. Further studies are needed to investigate whether the temporary suppression of neutrophil functions could affect the clearance of bacterial contaminations.

N-ACETYLCYSTEINE IMPROVES THE HEMODYNAMICS AND OXIDATIVE STRESS IN HYPOXIC NEWBORN PIGS REOXYGENATED WITH 100% OXYGEN

Neonatal asphyxia may lead to cardiac and renal complications perhaps mediated by oxygen free radicals. Using a model of neonatal hypoxia-reoxygenation, we tested the hypothesis that N-acetylcysteine (NAC) would improve cardiac function and renal blood flow. Eighteen piglets (aged 1-4 days old, weighing 1.4-2.2 kg) were anesthetized and acutely instrumented for continuous monitoring of pulmonary and renal artery flow (cardiac index [CI] and renal artery flow index [RAFI], respectively) and mean blood pressure. Alveolar hypoxia was induced for 2 h, followed by resuscitation with 100% oxygen for 1 h and 21% oxygen for 3 h. Animals were randomized to sham-operated, hypoxic control, and NAC treatment (i.v. bolus of 150 mg/kg given at 10 min of reoxygenation followed by 100 mg/kg per h infusion) groups. Myocardial and renal tissue glutathione content and lipid hydroperoxide levels were assayed, and histology was examined. After 2 h of hypoxia, all animals were acidotic (pH 6.96 +/- 0.04) and in cardiogenic shock with depressed renal blood flow. Upon reoxygenation, CI and RAFI increased but gradually deteriorated later. The NAC treatment prevented the decreased CI, stroke volume, mean blood pressure, systemic oxygen delivery, RAFI, and renal oxygen delivery at 2 to 4 h of reoxygenation observed in hypoxic controls (versus shams, all P < 0.05). The myocardial and renal tissue glutathione content was significantly higher in the NAC treatment group (versus controls). The CI and RAFI at 4 h of reoxygenation correlated with the tissue glutathione redox ratio (r = 0.5 and 0.6, respectively, P < 0.05). There were no significant differences in heart rate, pulmonary artery pressure, systemic oxygen uptake, and tissue lipid hydroperoxide levels between groups. No histologic injury was found in the heart or kidney. In this porcine model of neonatal hypoxia and 100% reoxygenation, NAC improved cardiac function and renal perfusion, with improved tissue glutathione content.

Inhibitory effect of HCPT on expression of HIF-1α and downstream genes in hypoxic human cervical SiHa cancer cells

The hypoxic model to simulate hypoxic microenvironment in solid tumors was established and the effect of hydrocamptothecin (HCPT) on the hypoxia-induced over-expression of HIF-1alpha and VEGF genes was explored. Human cervical cancer SiHa cells were cultured in vitro under hypoxic conditions (37 degrees C, 5% CO(2), 1% O(2)) and treated with different concentrations of HCPT for 24 h. The mRNA and protein expression levels of HIF-1alpha, VEGF and Glut1 in SiHa cells were detected by semi-quantitative RT-PCR and Western blot respectively. Normoxic control groups were exposed to normoxic conditions for 24 h. Under normoxic conditions, HCPT had no obvious effects on the HIF-1alpha and VEGF gene expression. Hypoxia induced the up-regulation of HIF-1alpha protein and downstream VEGF gene, and HCPT showed a dose-dependently inhibitory effect on the hypoxia-induced over-expression of HIF-1alpha protein and VEGF gene expression in SiHa cells, whereas HCPT had no significant effect on the HIF-1alpha mRNA expression. No difference in HCPT cytotoxicity was observed between hypoxic groups and normoxic control groups. It was suggested that HCPT could inhibit the expression of HIF-1alpha protein and downstream VEGF gene in hypoxic SiHa cells in a dose-dependent manner, and the inhibitory effect was not related with HCPT cytotoxicity.

Effects of simulated high-altitude hypoxia stress on hippocampal monoamine metabolism in rat

目的 探讨模拟高原低氧应激对大鼠海马细胞外液中单胺递质及其代谢产物的影响.方法雄性SD大鼠分为低氧应激组和正常对照组(每组各8只).将低氧应激组动物置于模拟海拔6000m低压舱内24h后,采用推挽灌流方法收集海马细胞外液,高效液相色谱-电化学检测法(HPLC-ECD)测定灌流液中去甲肾上腺素(NE)、多巴胺(DA)、3-甲氧4羟苯乙酸(DOPAC)、高香草酸(HVA)、5-羟色胺(5-HT)和5-羟吲哚乙酸(5-HIAA)含量,并采用放射免疫法测定血浆皮质酮(CORT)水平.结果与正常对照组比较,低压舱内处理后大鼠血浆皮质酮水平[(2.59±0.59)μg/ml]显著高于对照组[(0.84±0.29)μg/ml](P＜0.01);海马细胞外液中NE水平[(813.77±196.14)pg/50μl]显著低于对照组[(1209.20±282.01)pg/50μl](P＜0.01),5-HT水平[(82.65±26.35)pg/50μl]显著高于对照组[(53.35±27.88)pg/50μl](P＜0.05),DOPAC、HVA和5-HIAA水平均显著低于对照组(P＜0.05、0.01和0.05).结论模拟高原低氧应激显著影响大鼠海马单胺递质代谢。

Doppler tissue imaging in assessment of pulmonary hypertension-induced right ventricle dysfunction

We aimed to assess the accuracy of Doppler tissue imaging (DTI) in detecting right ventricle (RV) dysfunction and electromechanical coupling alteration following pulmonary hypertension (PHT) in rat. PHT was induced by chronic hypoxia exposure (hypoxic PHT) or monocrotaline treatment (monocrotaline PHT). In both PHT models, we observed transparietal RV pressure increase and remodeling, including hypertrophy and dilation. Conventional echocardiography provided evidence for pulmonary outflow impairment with midsystolic notch and acceleration time decrease in PHT groups (21.7 +/- 1.6 and 13.2 +/- 2.9 ms in hypoxic and monocrotaline PHT groups vs. 28.1 +/- 1.0 ms in control). RV shortening fraction was decreased in the monocrotaline PHT group compared with the hypoxic PHT and control groups. Combining conventional Doppler and DTI was more helpful to detect RV diastolic dysfunction in the monocrotaline PHT group (E/Ea ratio = 17.0 +/- 1.4) compared with the hypoxic PHT and control groups (11.5 +/- 0.7 and 10.2 +/- 0.4, respectively). Tei index measured using DTI highlighted global RV dysfunction in the monocrotaline PHT group (1.36 +/- 0.24 vs. 0.92 +/- 0.05 and 0.86 +/- 0.05 in the hypoxic PHT and control groups, respectively). Q-Sm time measured from the onset of Q wave to the onset of DTI Sm wave was increased in both PHT groups. PHT-induced electromechanical coupling alteration was confirmed by in vitro activation-contraction delay measurements on isolated RV papillary muscle, and both Q-Sm time and activation-contraction delay were correlated with PHT severity. We demonstrated that Q-Sm time measured in DTI was an easily and convenient index to detect early RV electromechanical coupling alteration in both moderate and severe PHT.

The protective effect of hypoxic preconditioning against light-induced photoreceptor degeneration in mice

To study the protective roles of hypoxic preconditioning in light induced retinal injury in a mice model and investigate the possible mechanism of related gene regulation. 54 BALB/c mice were randomly divided into simple light exposure group (SL), hypoxic pretreatment group (HP) and control group (CON). The mice of SL and HP were continually exposed to light for 3 h, which built model of light-induced damage. Morphologic changes of photoreceptor cells in different group were examined by light microscope and the apoptosis was detected by TdT-mediated dUTP nick end labeling. Different expressions of c-fos and caspase-1 gene were examined by immunohistochemical staining. In group SL, the photic injury appeared very obviously and early. Different changes appeared in the outer nuclear layer after light exposure. Photic injury was aggravated following the increased light exposure. Positive staining of c-fos and caspase-1 could be seen in the outer nuclear layer. In group HP, the changes of retinal morphology appeared slightly and lately. Compared with group SL, caspsae-1 expression was decreased obviously, while no difference was seen in the expression of c-fos. The retinal structures was normal in the mice of control group and c-fos and caspase-1 were stained negative. Hypoxic preconditioning has neuroprotective effect on photoreceptor cells by inhibiting the expression of apoptosis-related genes in photic injured mice model. caspase-1 may be involved in the protective mechanism.

Sprint-Interval Training-Induced Alterations of Myosin Heavy Chain Isoforms and Enzyme Activities in Rat Diaphragm: Effect of Normobaric Hypoxia

The purpose of this study was twofold: (i) to investigate if sprint-interval training (SIT) alters myosin heavy chain (MyHC) isoform composition and bioenergetic properties within the rat diaphragm, and (ii) to determine if mild normobaric hypoxia would enhance the effects of SIT-induced diaphragmatic adaptation. Male Wistar rats (8 weeks old) were randomly assigned to one of four groups (n = 7/group): (i) normoxic control (NC); (ii) normoxic training (NT); (iii) hypoxic control (HC); or (iv) hypoxic training (HT). The NT and HT groups were engaged in SIT (1 min sprint and 2-5 min rest, 6-10 sets/day, 5-6 days/week) on a treadmill for 9 weeks. Animals in the HC and HT groups were exposed to normobaric hypoxia (14.5% O(2)) during an SIT program from the 4th week of the training period. After completion of the training program, MyHC composition, citrate synthase (CS) activity, and lactate dehydrogenase (LDH) activity in the diaphragm and plantaris muscle were analyzed. An analysis of diaphragmatic MyHC composition demonstrated increased type IIa and decreased type IId/x for both training groups (P < 0.05), with the HT group producing greater changes than the NT group (P < 0.05). The plantaris muscle, however, showed increased Type IIa and IId/x and decreased Type IIb for both the NT and HT groups (P < 0.05). CS activity increased only for the training groups (P < 0.05), and this change was greater for the HT group in the diaphragm and for the NT group in the plantaris muscle (P < 0.05). Further, diaphragmatic LDH activity in HT was significantly lower (P < 0.05) than in HC and NT. These findings demonstrated that SIT could induce alterations in MyHC composition from fast to slow within type II isoforms and also improve the oxidative capacity in the diaphragm and plantaris muscles. It is of importance that our data revealed that SIT-induced diaphragmatic adaptations were enhanced when SIT was performed in normobaric hypoxia.

Prolonged Nitric Oxide Inhalation Fails to Regress Hypoxic Vascular Remodeling in Rat Lung

The purpose of present study was to investigate whether long-term nitric oxide (NO) inhalation during the recovery in air might improve the regression of chronic hypoxic pulmonary hypertension (PH) and vascular changes. The rats were exposed to 10 ppm of NO in air for 10 days (n = 12) and 30 days (n = 4), or 40 ppm of NO in air for 10 days (n = 6) and 30 days (n = 12) following 10 days of hypobaric hypoxia (380 mm Hg, 10% oxygen). For each NO group, air control rats following hypoxic exposure were studied at the same time (n = 13, 11, 9, and 11, respectively). Normal air rats (n = 6) without hypoxic exposure and rats (n = 7) following 10 days of hypoxic exposure were used as normal and chronic hypoxic control groups, respectively. Muscularization of normally nonmuscular peripheral arteries and medial hypertrophy of normally muscular arteries were assessed by light microscopy. An additional 16 rats were used to investigate the recovery of pulmonary artery pressure with (n = 8) and without NO inhalation (n = 8) after 10 days of hypobaric hypoxia. Long-term hypoxia-induced PH, right ventricular hypertrophy (RVH), and hypertensive pulmonary vascular changes, each of which regressed partly after recovery in room air. There were no differences among rats with and without NO during each recovery period in RVH, medial wall thickness of muscular artery, and the percentages of muscularized arteries at the alveolar wall and duct levels. Continuous inhaled 40 ppm NO decreased pulmonary artery pressure from 40.1 +/- 1.1 to 29.9 +/- 3.8 mm Hg (mean +/- SE) [n = 8], which was not different in the rats without NO inhalation (n = 8). Urine nitrate level was higher in rats that had inhaled NO. Continuous NO inhalation showed no effect on regression of pulmonary vascular remodeling in chronic hypoxic PH after returning to room air.

Effect of a carbohydrate supplement on feeding behaviour and exercise in rats exposed to hypobaric hypoxia

The effect of a carbohydrate supplement, offered as a diet option, on feeding behaviour, body weight gain, and endurance exercise was studied in rats exposed to hypobaric hypoxia. Male albino rats (n=35) were randomly divided into 5 groups; hypoxic supplemented and control groups; normoxic supplemented and control groups, and an untreated control group. After treadmill training for 5 days, the hypoxic groups were exposed to simulated high altitude equivalent to 6960m for 18 days continuously. Food and water intakes, body weight and endurance exercise were recorded before and during the exposure period. Blood glucose, insulin, muscle and liver glycogen were assayed at the end of the exposure period. Hypobaric hypoxia resulted in a significant decrease in food and water intake, and body weight, and reduced endurance exercise capacity compared to the basal and normoxic group values. The carbohydrate supplement did not ameliorate the hypoxia-induced loss in body weight, but however, significantly delayed the onset of fatigue during exercise in the supplemented rats compared to the hypoxic control group.

Regional vulnerability to chronic hypoxia and chronic hypoperfusion in the rat brain

The purpose of this study was to compare the pathological findings of injury induced by chronic hypoperfusion and by chronic hypoxia in rat brain. Adult male Wistar rats were divided into three groups: chronic hypoperfusion ( n=5), chronic hypoxia ( n=5), and normal control groups ( n=5). Hypoperfusion was induced by ligation of the bilateral carotid arteries under 2.5% halothane anesthesia. Chronic hypoxia was induced by keeping the animals in a chamber with an atmosphere of 10% O 2 in N 2 for 3 weeks. Twelve weeks later (chronic hypoperfusion group) and 3 weeks later (chronic hypoxia group), the animals were sacrificed and perfused through the femoral artery with a fixative containing 4% paraformaldehyde. Hematoxylin and eosin staining was done in all sections in the three groups, and the number of normal-appearing cells was counted. Normal-appearing cells in CA3 were significantly decreased in the chronic hypoperfusion group compared with those in the chronic hypoxia group, although neurons in CA1, CA2 and CA4 in both groups were equally damaged. We concluded that the CA3 hippocampus shows different vulnerabilities to chronic hypoperfusion and chronic hypoxia, possibly owing to a difference in the kinds of glutaminergic receptors.

Adenosine receptor blockade and hypoxia-tolerance in rainbow trout and Pacific hagfish. I. Effects on anaerobic metabolism

The physiological properties of adenosine may be essential in the control of energy metabolism for the survival of animals exposed to oxygen shortages. Accordingly, we tested the hypothesis that adenosine modulates metabolic regulation in rainbow trout and Pacific hagfish exposed to acute hypoxia. Treatment of hypoxic rainbow trout (PwO2=3.33 or 4.00 kPa) with the adenosine receptor (AR) blocker theophylline was associated with greater increases in plasma [lactate], more rapid and pronounced metabolic acidosis, higher tissue [lactate], and lower heart creatine charge and glycogen content than in the hypoxic controls. The recruitment of anaerobic metabolism in hypoxic trout treated with enprofylline, an AR blocker with very weak affinity, was intermediate to that of the hypoxic theophylline-injected and control groups. In hagfish, plasma [lactate] increased following exposure to a PwO2 of 1.33 kPa but did not increase following exposure to 3.33 kPa and, like plasma acidosis, it was greatest in the animals treated with theophylline. These findings indicate that AR blockade results in a more rapid and pronounced recruitment of anaerobic metabolism following acute hypoxic exposure, and while rainbow trout and Pacific hagfish show marked differences in their responses to hypoxia, adenosine appears to play an important protective role in both species.

Acute hypoxia and endogenous renal endothelin.

Endothelin (ET) is a potent vasoconstrictor peptide of endothelial cell origin. Recent studies have suggested a nonvascular paracrine and/or autocrine role for endothelin in the kidney. This study was designed to elucidate the renal ET response to acute moderate hypoxia, as reflected by urinary ET excretory rate and renal tissue ET immunoreactivity, and to correlate these responses to the hemodynamic and excretory changes during hypoxia. Experiments were conducted in two groups of anesthetized dogs: hypoxic group (10% O2 ventilation: PO2, 44 mm Hg; N = 7) and time control group (room air ventilation: PO2, 111 mm Hg; N = 6). After 60 min of hypoxia or room air ventilation, kidneys were harvested and stained immunohistochemically for ET. Acute moderate hypoxia was associated with significant increases in urinary ET excretion, urine flow, urinary sodium excretion, and fractional excretion of sodium (P < 0.05). There was no significant change in GFR, RBF, renal vascular resistance, or mean arterial pressure. Renal immunohistochemistry for ET revealed increased staining in the proximal and distal tubules in the hypoxic group as compared with controls. This study demonstrates that acute moderate hypoxia results in increased urinary ET excretion and renal tubular ET immunoreactivity, in association with diuresis and natriuresis, and suggests a nonvascular role of endogenously produced renal ET in the regulation of sodium homeostasis during hypoxia.