Effects of Acute Hypoxia and Reoxygenation on Hematological Parameters, Antioxidant Activity, and Hypoxia-Related Genes Expressions in Rainbow Trout and Steelhead

During an acute hypoxia exposure, impairment of memory is one of the most frequently reported symptoms, either during hypoxia awareness training of aircrews or after an in-flight hypoxic incident. However, the effects of acute hypoxia on memory have been little studied in laboratory-controlled conditions. Moreover, none of these studies were performed in hypobaric conditions. The main aim of our study was to investigate the effects of acute hypobaric hypoxia on working memory (WM). This study also aimed to find links between physiological measurements and cognitive performance during acute hypoxia exposure. During hypoxia awareness training, 28 subjects (experimental group) were exposed to a simulated altitude level of 10,000 m (31,000 ft) in a hypobaric chamber, while 29 subjects (control group) stayed at sea level. WM was assessed in both groups with the Paced Auditory Serial Addition Test (PASAT). Peripheral oxygen saturation (SpO2) and heart rate were recorded. WM was strongly impaired in the hypoxic group. One major finding is that hypoxia highly increased the mean error frequency rate. WM performance decreased linearly with hypoxemia, but SpO2 was weakly predictive of PASAT performance and vice versa. WM is impaired by acute hypobaric hypoxia. Given the importance of WM in aircraft piloting and its sensitivity to hypoxia, the PASAT, in association with SpO2 and EEG recordings, could improve both hypoxia training and our understanding of the effects of hypoxia on memory.

Effects of acute hypoxia on intracellular-pH regulation in astrocytes cultured from rat hippocampus

Although several investigations have demonstrated the beneficial effects of chrysin (CH), there is limited information on its supportive effects on rainbow trout (Oncorhynchus mykiss) physiology. In this work, fish were fed with pellets containing 0, (CH0) 100 (CH100), 300 (CH300), 500 (CH500) and 700 (CH700) mg/kg chrysin for 56 days, then the specimens weighed and were exposed to 14-day crowding stress. Innate immune responses, antioxidant capacity, hematology indices, and biochemical parameters were tested before and after crowding stress. The final weight (FW), weight gain (WG), and specific growth rate (SGR) increased, and feed conversion ratio (FCR) decreased in the groups fed diets containing CH300-CH700 compared to control group. Also, the optimum dose for maximum and minimum SGR and FCR were obtained at 470 and 490 mg CH (P < 0.05), according to the polynomial regression test, respectively. There was an interaction between dietary CH and crowding stress on immune responses, antioxidant defense, hematological and serum biochemical parameters. Before stress, serum and mucus immune responses [lysozyme and alternative complement (ACH50) activity, and total immunoglobulin (Ig)] were increased in CH300 group (P < 0.05). After stress, immunological activities were improved by diets supplemented with 300–700 mg/kg of chrysin. Before stress, red blood cell (RBC) count, percentage of hematocrit (HCT), blood leukocyte (WBC) count, and monocyte (MON) count clearly increased in the CH300 group (P < 0.05). After stress, hematological parameters were enhanced in the CH-treated fish compared to the control. The lowest serum biochemical parameters (liver enzymes, and glucose) values were noticed in CH500 treatment before stress, except for cortisol. After stress, serum biochemical parameters in response to all dietary treatments significantly decreased, except for aspartate aminotransferase (AST) (P < 0.05). Before stress, antioxidant enzymes activities significantly improved in fish fed with diets containing 300 and 500 mg of CH (P < 0.05). After stress, administration of 300–700 mg CH remarkably boosted antioxidant enzymes activities (P < 0.05). MDA value decreased in response to diets containing 300–700 mg CH, before and after stress. In summary, CH300 and CH500 diets more effectively boosted growth performance and reduced the harmful effects of crowding on health status of the rainbow trout.

Effect of acute hypoxia on metabolism and ventilation in awake piglets

Although hypoxia has the potential to impair the cognitive function, the effects of acute hypoxia on the high-order brain function (executive and/or inhibitory processing) and somatosensory ascending processing remain unknown. We tested the hypothesis that acute hypoxia impairs both motor executive and inhibitory processing and somatosensory ascending processing. Fifteen healthy subjects performed two sessions (sessions 1 and 2), consisting of electroencephalographic event-related potentials with somatosensory Go/No-go paradigms and somatosensory-evoked potentials (SEPs) under two conditions (hypoxia and normoxia) on different days. On 1 day, participants breathed room air in the first and second sessions of the experiment; on the other day, participants breathed room air in the first session, and 12% O2 in the second session. Acute hypoxia reduced the peak amplitudes of Go-P300 and No-go-P300, and delayed the peak latency of Go-P300. However, no significant differences were observed in the peak amplitude or latency of N140, behavioral data, or the amplitudes and latencies of individual SEP components between the two conditions. These results suggest that acute hypoxia impaired neural activity in motor executive and inhibitory processing, and delayed higher cognitive processing for motor execution, whereas neural activity in somatosensory processing was not affected by acute hypoxia.NEW & NOTEWORTHY Hypoxia has the potential to impair the cognitive function, but the effects of acute hypoxia on the cognitive function remain debatable. We investigated the effects of acute hypoxia on human cognitive processing using electroencephalographic event-related potentials and somatosensory-evoked potentials. Acute normobaric hypoxia impaired neural activity in motor executive and inhibitory processing, but no significant differences were observed in neural activity in somatosensory processing.

Effects of acute hypoxia and reoxygenation on histological structure, antioxidant response, and apoptosis in razor clam Sinonovacula constricta

Oxygen is a vital element in aquatic environments. The concentration of oxygen to which aquatic organisms are exposed is influenced by salinity, water temperature, weather, and surface water runoff. Hypoxia has a serious effect on fish populations, and can lead to the loss of habitat and die-offs. Therefore, in the present study we used next-generation sequencing technology to characterize the transcriptomes of Pelteobagrus vachelli and identified 70 candidate genes in the HIF-1 signaling pathway that are important for the hypoxic response in all metazoan species. For the first time, the present study reported the effects of acute hypoxia and reoxygenation on oxygen sensors, respiratory metabolism, and hematology indices in P. vachelli. The predicted physiological adjustments show that P. vachelli's blood oxygen-carrying capacity was increased through increased RBC, HB, and SI after hypoxia exposure. Glycolysis-related enzyme activities (PFK, HK, and PK) and LDH in the brain and liver also increased, indicating a rise in anaerobic metabolism. The observed reduction in oxidative enzyme level (CS) in the liver during hypoxia suggests a concomitant depression in aerobic metabolism. There were significant increases in oxygen sensor mRNA expression and HIF-1α protein expression during hypoxia and reoxygenation exposure, suggesting that the HIF-1 signaling pathway was activated in the liver and brain of P. vachelli in response to acute hypoxia and reoxygenation. Our findings suggest that oxygen sensors (e.g., HIF-1α) of P. vachelli are potentially useful biomarkers of environmental hypoxic exposure. These data contribute to a better understanding of the molecular mechanisms of the hypoxia signaling pathway in fish under hypoxia and reoxygenation.

The potential direct and modulating effects of acute hypoxia on catecholamine secretion in rainbow trout (Oncorhynchus mykiss) were assessed in situ, using a perfused cardinal vein preparation, and in vivo, using chronically cannulated fish. Acute (10 min) perfusion with hypoxic (P(O2)<10 mmHg) saline or homologous hypoxic blood did not have a statistically significant effect on basal (non-stimulated) catecholamine secretion. A field stimulation technique was used to excite the sympathetic nerves innervating the chromaffin cells electrically in situ under conditions of high-P(O2) (saline P(O2)=152 mmHg; 1 mmHg=0.133 kPa) or low-P(O2) (saline P(O2)<10 mmHg) perfusion at constant P(CO2) (2.3 mmHg). The results demonstrated that neuronally evoked catecholamine secretion was significantly lowered by 50 % during perfusion with hypoxic saline. To assess whether the inhibitory effect of hypoxia during neuronal stimulation in situ resulted from modulation of nicotinic and/or muscarinic receptor-linked pathways, perfused posterior cardinal vein preparations were injected with selective nicotinic (10(-)(7) or 10(-)(6 )mol kg(-)(1) nicotine) or muscarinic (10(-)(3 )mol kg(-)(1) methacholine) receptor agonists. For both doses of nicotine, catecholamine secretion was significantly lowered during hypoxia by 55 %. During muscarinic receptor stimulation, perfusion with hypoxic saline caused a 42 % reduction in the rate of catecholamine secretion. In contrast, catecholamine secretion elicited by depolarising levels of KCl (60 mmol l(-)(1)) was unaffected by the oxygen status of the perfusate. In vivo, intra-arterial injections of nicotine (300-600 nmol kg(-)(1)) into normoxic (water P(O2)=155 mmHg) or moderately hypoxic fish (water P(O2)=80 mmHg) caused a dose-dependent elevation of circulating catecholamine levels. However, despite the inhibitory influence of localised hypoxia on chromaffin cell responsiveness previously demonstrated in situ, the increase in plasma catecholamine levels after intra-arterial injection of nicotine was significantly enhanced in the hypoxic fish. The differences between the results from the in vivo and in situ experiments may reflect the contribution of higher control centres and modulating factors in vivo that are absent in situ.

This paper evaluates the response of trout exposed to acute hypoxia between 8.7 mgO2/l (controls) and 1.4 mgO2/l. Temperature, pH, NH4, oxygen consumption rate and spleen-somatic index (SSI) were evaluated. Blood cell counts, oxidative radicals (ORs) production and immature erythrocytes were assessed to evaluate their relationship with the degree of hypoxia. Acute hypoxia induced a decrease in water pH (p < 0.05), oxygen consumption rate (60% less), SSI (55% less) and a significant increase of water ammonium concentration (p < 0.05). Haematocrit increased significantly starting at 4.8 mgO2/l, as well as an increase in the total number of leukocytes (up to 50% in some fish). Starting at 2 mgO2/l, swelling of erythrocytes was induced and a decrease in the potential production of ORs, showing a negative correlation to immature erythrocyte numbers. These results suggest that lower than normal oxygen concentrations may jeopardize ORs production and hence non-specific defence mechanisms in trout. High percentages of immature erythrocytes can be used as a simple and inexpensive indicator of both hypoxic events and impairment of ORs production in the absence of bleeding, haemolysis, anti-anaemia treatments and/or increased temperature.

Investigation of long-term bisphenol A exposure on rainbow trout (Oncorhynchus mykiss): Hematological parameters, biochemical indicator, antioxidant activity, and histopathological examination.

The results of assessing the effect of replacing fish meal with soy protein concentrate at 10, 17, 24 and 30% of feed weight on hematological and biochemical parameters of rainbow trout blood are presented. According to the results of clinical and gross anatomy examination, it was found that soy concentrate at 24 and 30% of feed weight led to both a decrease in cavity fat accumulation and intestinal hyperemia, which may indicate the onset of intestinal inflammation. At lower concentrations (10 and 17% of feed weight), no such changes were detected in the intestine. Experiments showed that soy concentrate at 24 and 30% of feed weight increased the number of neutrophils and monocytes in the fish blood, while decreasing the leukocyte count. Lower doses of soy concentrate had no effect on hematological parameters. The key change in blood biochemical parameters was an increase in aspartaminotransferase activity and serum protein (albumin and globulin) concentrations, observed in the groups fed higher doses of soy concentrate. Preliminary data suggest that incorporating soy concentrate at 24 and 30% of feed weight may impair rainbow trout physiological parameters due to altered amino acid composition and the presence of anti-nutritional factors. However, soy concentrate had no observable effect on growth; all experimental groups exhibited similar growth dynamics.

The effect of acute hypoxia on prostaglandin release in perfused human fetal placenta

Acute hypoxia is a common stress in aquaculture, and causes energy deficiency, oxidative damage and death in fish. Many studies have confirmed that acute hypoxia activated hif1α expression, anaerobic glycolysis and antioxidant system in fish, but the effects of acute hypoxia on lipid and protein metabolism, organelle damage, and the functions of hif2α and hif3α in economic fishes have not been well evaluated. In the present study, turbot was exposed to acute hypoxia (2.0 ± 0.5mg/L) for 6h, 12h, and 24h, respectively. Then, the contents of hemoglobin (HB), metabolite, gene expressions of hifα isoforms, energy homeostasis, endoplasmic reticulum (ER) stress, and apoptosis were measured. The results suggested that turbot is intolerant to acute hypoxia and the asphyxiation point is about 1.5mg/L. Acute hypoxia induced perk-mediated ER stress, and increased lipid peroxidation and liver injury in turbot. The blood HB level and liver vegfab expression were increased under hypoxia, which enhances oxygen transport. At hypoxia stress, hif3α, anaerobic glycolysis-related genes expression, and lactate content were increased in the liver, and glycogen was broken down to ensure ATP supply. Meanwhile, hif2α, lipid synthesis-related genes expression, and TG content were increased in the liver, but the lipid catabolism and protein synthesis were suppressed during hypoxia, which reduced the oxygen consumption and ROS generation. Our results systematically illustrate the metabolic and physiological changes under acute hypoxia in turbot, and provide important guidance to improve hypoxia tolerance in fish.

The effects of acute hypoxia on the intensity of free-radical processes in the basal nuclei (caudate nucleus, globus pallidus, nucleus accumbens, amygdalar complex) and the behavior of rats in an open field were studied in conditions of an altered photoperiod. Constant darkness was found to eliminate the effects of acute hypoxia on the intensity of lipid peroxidation (LPO), to preserve superoxide dismutase and catalase activities at higher levels, and to decrease glutathione peroxidase activity. In the light, there were increases in the sensitivity of neurons in the basal nuclei to acute hypoxia, which was manifest as intensification of LPO due to increased formation of diene conjugates. Catalase activity in almost all structures was significantly greater even than in intact rats. Altered photoperiods were found to modulate the effects of acute hypoxia on measures of activity in rats in the open field, the nature of the changes depending on the nature of the change in photophases.

To study Megalobrama amblycephala adaption to water hypoxia, the changes in physiological levels, innate immune responses, redox balance of M.amblycephala during hypoxia were investigated in the present study. When M. amblycephala were exposed to different dissolved oxygen (DO) including control (DO: 5.5 mg/L) and acute hypoxia (DO: 3.5 and 1.0 mg/L, respectively), hemoglobin (Hb), methemoglobin (MetHb), glucose, Na+, succinatedehydrogenase (SDH), lactate, interferon alpha (IFNα), and lysozyme (LYZ), except hepatic glycogen and albumin gradually increased with the decrease of DO level. When M. amblycephala were exposed to different hypoxia time including 0.5 and 6 h (DO: 3.5 mg/L), and then reoxygenation for 24 h after 6 h hypoxia, Hb, MetHb, glucose, lactate, and IFNα, except Na+, SDH, hepatic glycogen, albumin, and LYZ increased with the extension of hypoxia time, while the above investigated indexes (except albumin, IFNα, and LYZ) decreased after reoxygenation. On the other hand, the liver SOD, CAT, hydrogen peroxide (H2O2), and total ROS were all remained at lower levels under hypoxia stress. Finally, Hif-1α protein in the liver, spleen, and gill were increased with the decrease of oxygen concentration and prolongation of hypoxia time. Interestingly, one Hsp70 isoforms mediated by internal ribozyme entry site (IRES) named junior Hsp70 was only detected in liver, spleen and gill. Taken together, these results suggest that hypoxia affects M. amblycephala physiology and reduces liver oxidative stress. Hypoxia-reoxygenation stimulates M. amblycephala immune parameter expressions, while Hsp70 response to hypoxia is tissue-specific.