Excess Oxygen Consumption Research Articles

Hypoxia Pathways in Parkinson’s Disease: From Pathogenesis to Therapeutic Targets

The human brain is highly dependent on oxygen, utilizing approximately 20% of the body’s oxygen at rest. Oxygen deprivation to the brain can lead to loss of consciousness within seconds and death within minutes. Recent studies have identified regions of the brain with spontaneous episodic hypoxia, referred to as “hypoxic pockets”. Hypoxia can also result from impaired blood flow due to conditions such as heart disease, blood clots, stroke, or hemorrhage, as well as from reduced oxygen intake or excessive oxygen consumption caused by factors like low ambient oxygen, pulmonary diseases, infections, inflammation, and cancer. Severe hypoxia in the brain can manifest symptoms similar to Parkinson’s disease (PD), including cerebral edema, mood disturbances, and cognitive impairments. Additionally, the development of PD appears to be closely associated with hypoxia and hypoxic pathways. This review seeks to investigate the molecular interactions between hypoxia and PD, emphasizing the pathological role of hypoxic pathways in PD and exploring their potential as therapeutic targets.

Lacustrine groundwater discharge-derived carbon and nitrogen to regulate biogeochemical processes as revealed by stable isotope signals in a large shallow eutrophic lake

Eutrophic shallow lakes are hotspots of carbon (C) and nitrogen (N) accumulation and transformation, and are increasingly recognized as important sources of greenhouse gases (GHGs: CO2, CH4 and N2O). Lacustrine groundwater discharge (LGD) is a crucial component of the water budget and terrestrial material delivery for lakes, but its interplays with intrinsic CN biogeochemical processes remain less tackled. In this study, C and N ingredients and multiple stable isotopes (δ2H, δ18O, δ13C, and δ15N) were measured seasonally in groundwater, river water and lake water of a large eutrophic shallow lake in eastern China. The results revealed that groundwater is enriched with various forms of C and N that have similar sources and pathways as surface water in the lake and rivers. The isotope balance model also indicated that LGD derived C and N contribute significantly to lake inventories in addition to river runoff. These allochthonous C and N provide extra substrates for related biogeochemical processes, such as algae proliferation, organic matter degradation, methanogenesis and denitrification. Simultaneously, the excess oxygen consumption leads to depletion and hypoxia in the lake, further facilitating the processes of methanogenesis and denitrification. LGD functions not only as an external source of C and N that directly increases GHG saturations, but also as a mediator of internal CN pathways, which significantly affect hypoxia formation, GHG productions and emissions in the eutrophic lake. This study highlights the unrevealed potential regulation of LGD on biogeochemical processes in the eutrophic lake, and underscores the need for its consideration in environmental and ecological studies of lakes both regionally and globally.

Evaluation of the Şerefiye (Zara-Sivas) Dam According to Water Quality Indexes

With the aim of determining the water quality of Şerefiye Dam, Sivas province, the present study was carried out on the samples collected monthly from 3 stations between January 2014 and December 2014. In the analyses, which examined 25 variables, water quality was determined using the World Health Organization drinking water standards, water quality index (WQI), sodium absorption ratio (SAR), sodium percentage, permeability index (PI), magnesium index, irrigation index, and the Surface Water Quality Regulation (SWQR) of the Turkish Ministry of Forestry and Water Affairs. The mean value of water quality index in the dam was found to be 46.82 and the mean value of IWOI irrigation was found to be 3.90. The results obtained here showed that Şerefiye Dam was in the "very good" class in terms of water quality index and irrigation water quality. In addition, there was no oxygen deficiency due to excessive oxygen consumption during organic matter decomposition. The water quality parameters were much lower than the thresholds set in the SWQR, but according to the results of factor analysis (FA), the main variables responsible for the processes in the ecosystem were TSS, COD, SO3, SO4, EC, BOD, NO3, NH4, DO and Fe

The effect of progressive hypoxia on swimming mode and oxygen consumption in the pile perch, Phanerodon vacca

The effect of progressive hypoxia on swimming mode and oxygen consumption in the pile perch, Phanerodon vacca

Oxygen uptake during the last bouts of exercise incorporated into high-intensity intermittent cross-exercise exceeds the [formula omitted] O2max of the same exercise mode

Oxygen uptake (V˙ O2) was measured during a non-exhaustive high-intensity intermittent cross-exercise (HIICE) protocol consisting of four alternating bouts of 20 ​s running (R) and three bouts of bicycle exercise (BE) at ∼160% and ∼170% maximal oxygen uptake (V˙ O2max), respectively, with 10 ​s between-bout rests (sequence R-BE-R-BE-R-BE-R). The V˙ O2 during the last BE ([52.2 ​± ​5.0] mL·kg−1·min−1) was significantly higher than the V˙ O2max of the BE ([48.0 ​± ​5.4] mL·kg−1·min−1, n ​= ​30) and similar to that of running. For clarifying the underlying mechanisms, a corresponding HIICE-protocol with BE and arm cranking ergometer exercise (AC) was used (sequence AC-AC-BE-AC-BE-AC-AC-BE). In some experiments, thigh blood flow was occluded by a cuff around the upper thigh. Without occlusion, the V˙ O2 during the AC ([39.2 ​± ​7.1] mL·kg−1·min−1 [6th bout]) was significantly higher than the V˙ O2max of AC ([30.2 ​± ​4.4] mL·kg−1·min−1, n ​= ​7). With occlusion, the corresponding V˙ O2 ([29.8 ​± ​3.9] mL·kg−1·min−1) was reduced to that of the V˙ O2max of AC and significantly less than the V˙ O2 without occlusion. These findings suggest that during the last bouts of HIICE may exceed the of the specific exercise, probably because it is a summation of the V˙ O2 for the ongoing exercise plus excess post-oxygen consumption (EPOC) produced by the previous exercise with a higher V˙ O2max.

Intermittent normobaric hypoxia alters substrate partitioning and muscle oxygenation in individuals with obesity: implications for fat burning.

This single-blind, crossover study aimed to measure and evaluate the short-term metabolic responses to continuous and intermittent hypoxic patterns in individuals with obesity. Indirect calorimetry was used to quantify changes in resting metabolic rate (RMR), carbohydrate (CHOox, %CHO), and fat oxidation (FATox, %FAT) in nine individuals with obesity pre and post: 1) breathing normoxic air [normoxic sham control (NS-control)], 2) breathing continuous hypoxia (CH), or 3) breathing intermittent hypoxia (IH). A mean peripheral oxygen saturation ([Formula: see text]) of 80-85% was achieved over a total of 45 min of hypoxia. Throughout each intervention, pulmonary gas exchanges, oxygen consumption (V̇o2) carbon dioxide production (V̇co2), and deoxyhemoglobin concentration (Δ[HHb]) in the vastus lateralis were measured. Both RMR and CHOox measured pre- and postinterventions were unchanged following each treatment: NS-control, CH, or IH (all P > 0.05). Conversely, a significant increase in FATox was evident between pre- and post-IH (+44%, P = 0.048). Although the mean Δ[HHb] values significantly increased during both IH and CH (P < 0.05), the greatest zenith of Δ[HHb] was achieved in IH compared with CH (P = 0.002). Furthermore, there was a positive correlation between Δ[HHb] and the shift in FATox measured pre- and postintervention. It is suggested that during IH, the increased bouts of muscle hypoxia, revealed by elevated Δ[HHb], coupled with cyclic periods of excess posthypoxia oxygen consumption (EPHOC, inherent to the intermittent pattern) played a significant role in driving the increase in FATox post-IH.

The Length And Magnitude Of Exercise Analgesia Following Exercise Is Correlated With Excess Post-oxygen Consumption

The Length And Magnitude Of Exercise Analgesia Following Exercise Is Correlated With Excess Post-oxygen Consumption

A large aerobic scope and complex regulatory abilities confer hypoxia tolerance in larval toadfish, Opsanus beta, across a wide thermal range

Few studies have been performed on early-life stage toadfish, and none have addressed their tolerance to temperature and hypoxia despite large seasonal temperature fluctuations and daily hypoxia in their natural environment. The first directed captive breeding of Opsanus beta allowed the examination of larval oxygen demands and hypoxia tolerance across the range of their environmental temperatures (23–33 °C). Larval toadfish exhibited a surprisingly large aerobic scope across the tested temperature range. In response to progressive hypoxia, larval toadfish showed early metabolic depression and a low regulation index (RI), while juveniles had higher regulatory abilities but, unexpectedly, a lower aerobic scope. Larval and juvenile toadfish survived hours of severe hypoxia, but larval fish had a higher excessive post-hypoxia oxygen consumption, yet their metabolic rate returned to RMR in the same timeframe as the juveniles, likely due to their higher aerobic scope. We defined hypoxia tolerance using a physiological trait, p50, the oxygen tension in which oxygen uptake is reduced to 50 % of the metabolic rate at rest and determined it at all tested temperatures. Comparing these p50 values to environmental conditions in Florida Bay using hourly temperature and oxygen measurements from January 2014–October 2021 revealed that larval toadfish rarely experience < p50 conditions (11 % of events). Further, the median duration of these events was 3 h. The metabolic performance of larval toadfish combined with temperature and oxygen observations from their natural environment reveals the fascinating strategy in which larval toadfish survive diel hypoxia across seasons.

Acute hydrogen sulfide exposure in post-smolt Atlantic salmon (Salmo salar): Critical levels and recovery

Despite the importance of Atlantic salmon in marine aquaculture production systems, remarkably little is known about the effects of hydrogen sulfide (H2S) on the physiology of the species. In recent years, mass mortalities of Atlantic salmon have been reported in recirculating aquaculture systems (RAS) due to acute H2S exposure. This highlights the importance of obtaining a better understanding of tolerance thresholds and metabolic responses to this toxic gas. The toxicity of H2S is exerted at the level of the mitochondria, where impairment of the enzyme cytochrome c oxidase inhibits cellular respiration. Because H2S depresses oxygen uptake (MO2), intermittent flow-through respirometry, a common method for assessing the metabolic response to various stressors in fishes, is a suitable method to determine concentration thresholds for when H2S affects the metabolism of Atlantic salmon. During exposure trials, 3 size groups (range ⁓100-500 g) of fish were acclimated to control conditions to obtain baseline measurements, whereafter they were exposed to progressively increasing H2S concentrations (0.53 ± 0.14 μM h−1) until MO2 decreased below the standard metabolic rate or loss of equilibrium occurred, which we considered to be the critical H2S concentration (H2Scrit). Fish were then allowed to recover in H2S free water to determine the excess oxygen consumption (EOC) following H2S exposure. The results show that Atlantic salmon have a lower tolerance to H2S than previously estimated, with a mean H2Scrit of 1.78 ± 0.39 μM H2S, which was independent of size. During recovery, the estimated EOC greatly exceeded the accumulated oxygen deficit (DO2) in all groups, and the small salmon had a significantly larger EOC. While the magnitude of the EOC was greater for small salmon, it did not differ in duration (recovery time) among the different sizes of fish. The larger EOC showed that H2S exposure had a greater effect on the recovery phase of the small salmon, and exposure to H2S may leave the fish more vulnerable to other stressors post-exposure. This study provides specific values that underline the sensitivity of Atlantic salmon to acute H2S exposure and emphasizes the importance of the aquaculture industry to implement mitigating strategies for the occurrence of H2S at production facilities.

The role of turbulence in the characteristic velocity and length of rocket combustors

High-fidelity direct numerical simulations are conducted to investigate combustion performance in high-pressure methane-oxygen diffusion flames with different inlet turbulence. The results are post-processed to investigate the influence of turbulence on characteristic velocity and length. It is found that despite the eminent fuel-rich non-premixed configuration of the flame, a substantial amount of heat release takes place in premixed lean conditions. It is found that the occurrence of this phenomenon increases with the turbulent kinetic energy due to the mixing enhancement driven by the greater strain rate. The greater prevalence of lean combustion is beneficial for combustion performance near injection but detrimental for the completion of chemical reactions at downstream positions. It is found that excessive upstream oxygen consumption is responsible for this result. With more prevalence of lean combustion, oxygen is depleted sooner, and alternative reaction paths through carbon dioxide reduction are necessary to finalize the burning process. Moreover, it is observed that lower entry turbulence is beneficial for the downstream mixing intensity since it enhances the generation of radial velocity shear and flame-generated turbulence. The opposing effects of turbulence upstream and downstream determine the existence of optimal turbulence characteristics providing minimum characteristic length while achieving complete burnout. The combustion chamber volume savings associated with this optimal configuration are in the order of 50%.

Function and development of interneurons involved in brain tissue oxygen regulation.

The regulation of oxygen in brain tissue is one of the most important fundamental questions in neuroscience and medicine. The brain is a metabolically demanding organ, and its health directly depends on maintaining oxygen concentrations within a relatively narrow range that is both sufficiently high to prevent hypoxia, and low enough to restrict the overproduction of oxygen species. Neurovascular interactions, which are responsible for oxygen delivery, consist of neuronal and glial components. GABAergic interneurons play a particularly important role in neurovascular interactions. The involvement of interneurons extends beyond the perspective of inhibition, which prevents excessive neuronal activity and oxygen consumption, and includes direct modulation of the microvasculature depending upon their sub-type. Namely, nitric oxide synthase-expressing (NOS), vasoactive intestinal peptide-expressing (VIP), and somatostatin-expressing (SST) interneurons have shown modulatory effects on microvessels. VIP interneurons are known to elicit vasodilation, SST interneurons typically cause vasoconstriction, and NOS interneurons have to propensity to induce both effects. Given the importance and heterogeneity of interneurons in regulating local brain tissue oxygen concentrations, we review their differing functions and developmental trajectories. Importantly, VIP and SST interneurons display key developmental milestones in adolescence, while NOS interneurons mature much earlier. The implications of these findings point to different periods of critical development of the interneuron-mediated oxygen regulatory systems. Such that interference with normal maturation processes early in development may effect NOS interneuron neurovascular interactions to a greater degree, while insults later in development may be more targeted toward VIP- and SST-mediated mechanisms of oxygen regulation.

Proximal tubular epithelia-specific transcriptomics of diabetic mice treated with dapagliflozin

Based on recent clinical trials using sodium-glucose co-transporter 2 inhibitor (SGLT2i) demonstrating the significant improvement of outcomes of diabetic kidney disease (DKD), the paradigm shift from “glomerulocentric” to “tubule centric” pathophysiology in DKD progression has been highlighted. Several responsible mechanisms for renoprotective effects by SGLT2i have been proposed recently, but the changes in proximal tubule-specific gene expression by SGLT2i in diabetic mice have not been elucidated. We report the analysis of the proximal tubular-specific pathway, demonstrating the downregulation of oxidative phosphorylation in dapagliflozin-treated db/db mice, a type 2 diabetic model. After 8-week treatment of dapagliflozin for db/db mice having a proximal tubule-specific tdTomato reporter, tdTomato-positive cells were isolated by FACS. Pathway analysis of RNA sequencing of isolated tubular epithelia revealed that oxidative phosphorylation was downregulated in dapagliflozin-treated mice. However, depletion of renal tissue ATP content in db/db mice was ameliorated by dapagliflozin administration. Pimonidazole staining demonstrated renal cortical tissue hypoxia in db/db mice, which was improved by dapagliflozin administration. This study suggests that dapagliflozin can ameliorate the excessive oxygen and ATP consumption, and subsequent tissue hypoxia in the diabetic kidney, which may explain, in part, the responsible mechanisms of the renoprotective effects of dapagliflozin.

Role of Particle Resuspension in Maintaining Hypoxic Level in the Pearl River Estuary

AbstractEutrophication‐induced seasonal hypoxia in the coastal ocean has widely been attributed to the excessive oxygen consumption induced by settling and deposition of organic particles on sea floor. However, the role of particle resuspension in maintaining the hypoxic level has seldom been investigated based on field observations. Here, we carefully examined particle resuspension and its contribution to oxygen consumption in the Pearl River Estuary in July 2020. The bottom hypoxia was found to appear over the organic‐rich mudbelt off the estuary. Concentrated particles in suspension near the bottom, which were induced by particle resuspension rather than by particle settling, occurred near the front created by shelf salinity intrusions where bottom hypoxia appeared in the summer. The total dissolved oxygen (DO) depletion responsible for bottom hypoxia can be exclusively estimated from the DO budget during the tidal cycle. The water DO depletion dominated by particle resuspension is larger than or at least comparable to sediment oxygen demand. This highlights that the DO budget in the absence of particle resuspension overestimates the DO level in coastal hypoxia. Overall, our results suggest that particle resuspension play a vital role in maintaining the DO level of bottom hypoxia. This finding will be helpful to understand the impact of particle resuspension on coastal hypoxia, as well as other marine environmental problems in estuary and coastal ocean.

Pseudohypoxemia From Leukocyte Larceny in a Patient With Chronic Myelogenous Leukemia

Arterial blood gas (ABG) analysis is a generally reliable and frequently employed test for evaluating blood oxygen content. False readings of low oxygen content are rare but can be expected in specific clinical scenarios such as leukemia patients with marked leukocytosis who can develop “leukocyte larceny,” a phenomenon of excess oxygen consumption by leukocytes. Awareness of this phenomenon may lead to early recognition and avoidance of unnecessary diagnostic and therapeutic interventions. This case report presents a patient with marked leukocytosis from chronic myelogenous leukemia whose extubation was briefly delayed due to pseudohypoxemia on ABG measurements.

Effects of maximum repetition resistance exercise at different intensities on excess post-oxygen consumption: Examination by BIG3 exercises

Effects of maximum repetition resistance exercise at different intensities on excess post-oxygen consumption: Examination by BIG3 exercises

Cognitive impairment caused by hypoxia: from clinical evidences to molecular mechanisms.

Hypoxia is a state of reduced oxygen supply and excessive oxygen consumption. According to the duration of hypoxic period, it can be classified as acute and chronic hypoxia. Both acute and chronic hypoxia could induce abundant neurological deficits. Although there have been significant advances in the pathophysiological injuries, few studies have focused on the cognitive dysfunction. In this review, we focused on the clinical evidences and molecular mechanisms of cognitive impairment under acute and chronic hypoxia. Hypoxia can impair several cognitive domains such as attention, learning and memory, procession speed and executive function, which are similar in acute and chronic hypoxia. The severity of cognitive deficit correlates with the duration and degree of hypoxia. Recovery can be achieved after acute hypoxia, while sequelae or even dementia can be observed after chronic hypoxia, perhaps due to the different molecular mechanisms. Cardiopulmonary compensatory response, glycolysis, oxidative stress, calcium overload, adenosine, mitochondrial disruption, inflammation and excitotoxicity contribute to the molecular mechanisms of cognitive deficit after acute hypoxia. During the chronic stage of hypoxia, different adaptive responses, impaired neurovascular coupling, apoptosis, transcription factors-mediated inflammation, as well as Aβ accumulation and tau phosphorylation account for the neurocognitive deficit. Moreover, brain structural changes with hippocampus and cortex atrophy, ventricle enlargement, senile plaque and neurofibrillary tangle deposition can be observed under chronic hypoxia rather than acute hypoxia.

Effect of water salinity on the oxidative system of juveniles of the North Atlantic white shrimp Litopenaeus setiferus reared in biofloc technology

AbstractThis study evaluated the effect of biofloc technology (BFT) at 3 (lsBFT) and 35 (hsBFT) practice salinity units (psu) on the zootechnical performance, oxygen consumption, antioxidant activity, and oxidative damage of Litopenaeus setiferus juveniles reared in outdoor tanks. After 90 days, no significant differences were observed in terms of survival (p &gt; .05). The final weight as well as wet weight gain, final biomass, and feeding conversion ratio (FCR) showed higher values for shrimp reared with hsBFT than those reared with lsBFT (p &lt; .05). Compared to that for the hsBFT treatment, high oxygen consumption (VO2) was observed for the lsBFT treatment under fasting and postprandial conditions (p &lt; .05). The activity of the enzymes catalase, superoxide dismutase, and glutathione‐S‐transferase from shrimp muscle did not show significant differences between the treatments (p &gt; .05). Regarding the lipid peroxidation (LPO) and oxidized protein (PO) in muscle samples, no significant differences were observed in LPO, whereas the PO was significantly higher for the lsBFT treatment (p &lt; .05), which was related to higher fasting and postprandial oxygen consumption of the juveniles (p &lt; .05). The adaptation of L. setiferus juveniles reared in BFT at low salinity is relatively weak because of their low growth and excessive oxygen consumption and the oxidative damage (PO) produced.

Hypoxia tolerance and metabolic coping strategies in Oreochromis niloticus

The Nile tilapia (Oreochromis niloticus) is widely farmed in tropical and subtropical pond culture. O. niloticus is recognized as a species that is tolerant of hypoxic conditions, a trait that may largely be responsible for the success of this species in aquaculture. Until now, neither coping mechanisms nor a comparison of various indices of hypoxia tolerance to characterize the response to hypoxia, have been described. In the present study, Nile tilapia were subjected to hypoxia of increasing severity and duration to examine effects on metabolic rate (MO2) and post hypoxic oxygen debt. MO2 was measured during periods of severe hypoxia at 2.1 kPa O2 (10% oxygen saturation) lasting between 2 and 24 h at 27 °C. Hypoxia tolerance was assessed by determining the critical oxygen tension (Pcrit) and the pO2 at which loss of equilibrium (LOE) occurred. We show that the tolerance of Nile tilapia to severe hypoxia is largely achieved through a capacity for metabolic depression. Despite prolonged exposure to dissolved oxygen levels below Pcrit, the fish showed little excess post-hypoxic oxygen consumption (EPHOC) upon return to normoxic conditions. LOE did not occur until conditions became near-anoxic. Blood pH was not affected by severe hypoxia (2.1 kPa O2), but a significant acidosis occurred during LOE, accompanied by a significant elevation in lactate and glucose levels. The results from the present study indicate that Nile tilapia do not switch to anaerobic metabolism during hypoxia until pO2 falls below 2.1 kPa.

Micro-Oxygenation in Upflow Anaerobic Sludge Bed (UASB) Reactors Using a Silicon Membrane for Sulfide Oxidation.

Sulfide produced by sulphate-reducing bacteria in anaerobic reactors can seriously affect biogas quality. Microaeration has become a reliable way to remove sulfide, by promoting its oxidation. However, limited research is available regarding its application in upflow anaerobic sludge bed (UASB) reactors. In this research, silicon membranes were studied as a mechanism to dose oxygen in USAB reactors. Two configurations were tested: the membrane placed inside the reactor or in an external module. Our results show that the external membrane proved to be a more practical alternative, providing conditions for sulfide oxidation. This led to a reduction in its concentration in the liquid effluent and biogas. External membrane configuration achieved a sulfide conversion rate of 2.4 g-S m2 d−1. Since the membrane was not sulfide-selective, methane losses were observed (about 9%). In addition, excessive oxygen consumption was observed, compared to the stoichiometric requirement. As is the case for many membrane-based systems, membrane area is a key factor determining the correct operation of the system.

Excess post-oxygen consumption following resistance training with three types of exercise

Excess post-oxygen consumption following resistance training with three types of exercise