Hypoxia-induced Lethality Research Articles

Evolutionarily conserved mechanisms regulating hypoxia tolerance in Drosophila melanogaster

Hypoxia is one of the critical pathological elements in many human diseases, including ischemic stroke, myocardial infarction and solid tumors. Understanding the mechanisms regulating hypoxia tolerance or susceptibility is essential for developing effective strategies for medical therapy. In this regard, we generated hypoxia-tolerant Drosophila melanogaster populations through experimental hypoxia-directed evolution in the laboratory, sequenced and analyzed their genomes. In parallel, we took advantage of the natural evolution of humans at high-altitude regions and analyzed the whole genomes of Ethiopian and Andean highlanders. Through a comparative genomic approach, we obtained a group of evolutionarily conserved genes (28 human/23 Drosophila genes) that are potentially involved in regulating hypoxia tolerance in both human highlanders and the hypoxia-tolerant flies. We confirmed that ubiquitous knocking down of the conserved genes, such as grn/ GATA3, inv/ EN1, Mkk4/MAP2K4, Pxt/DUOX1/DUOX2, pyd/TJP1, RapGAP1/RAP1GAP2, Shal/KCN and shep/RBMS3 dramatically enhanced hypoxia tolerance in vivo in Drosophila melanogaster. In addition, we found that glial-specific knocking down of Egfr, grn, pyd and Shal rescued hypoxia-induced lethality. Furthermore, we found that some of these conserved genes (i.e., bnl, croc, Mkk4 and shep) are required by Notch activation-conferred survival in hypoxic environment, whereas Egfr, grn, pyd and Shal regulating hypoxia tolerance through Notch-independent mechanisms. We believe that these evolutionarily conserved mechanisms are novel targets that have a strong potential to be translated into therapeutic strategies to treat or prevent hypoxia-related diseases. This project is supported by NIH grant 1R21NS120023-01A1. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Effects of Methanolic Extract of Ginkgo biloba Leaf against Hypoxia-Induced Lethality in Mice

Introduction: Hypoxia defines as a condition in which body tissues do not take sufficient oxygen supply. Chronic hypoxia has various medical consequences. Recently, the role of hypoxia in the progression of COVID-19 disease has been proven. Ginkgo biloba is a valuable plant from more than 2000 years ago. Ginkgo has antioxidant activity and exhibits good scavenging activity on the free radicals therefore, it is considered helpful in treating diseases associated with the generation of free radicals, including chronic inflammation, cerebral infarction, ischemic heart disease, and aging.Material and Methods: In this study, anti-hypoxic activities of G. biloba methanolic leaf extract have been determined against hypoxia-induced lethality in mice to understand its usefulness in treating ischemia.Results: The extract showed weak activity in asphyctic model. At 125 mg/kg, it significantly delayed the time of death compared to the control group (p<0.05) but did not show any activities in haemic or circulatory hypoxia tests even at a higher tested dose, 250 mg/kg. Although, at this dose, extract prolonged the survival time more than 1 minute in circulatory model, but this increase was not statistically significant.Conclusion: In conclusion, results from this study showed that extract has weak anti-hypoxic effects in the treatment of hypoxia.

Dexamethasone vs COVID-19: An experimental study in line with the preliminary findings of a large trial.

BackgroundThe preliminary report of the RECOVERY large randomised controlled trial indicated a promising survival effect for dexamethasone therapy of coronavirus disease 2019 (COVID‐19). This study aimed to investigate the anti‐hypoxic activities of dexamethasone to understand a possible mechanism of its action in hypoxia‐induced lethality through experimental models of hypoxia.MethodsIn this investigation, 84 Male BALB/c mice were randomly divided into groups of seven (12 groups). Treatment groups received 10 days of dexamethasone intraperitoneal injection at both human dose (~0.1 mg/kg) and the animal does (~1 mg/kg). Control negative and positive groups were treated with 10 ml/kg of normal saline and 30 mg/kg of propranolol, respectively. Three experimental models of hypoxia, asphyctic, circulatory, and hemic were applied in this study.ResultsThe findings showed that dexamethasone significantly prolonged the latency for death in the asphyctic model concerning the control group in both humans (P < .0001) and animal dose (P < .0001). The results were also highly significant for both doses in the hemic model (P < .001). In the circulatory model, although a small increase was observed in death prolongation, results were not statistically significant for both doses in this model (P > .05).ConclusionsThis experimental in vivo investigation demonstrated an excellent protective effect for 10 days of dexamethasone treatment against hypoxia, especially in asphyctic and hemic models. In addition to promising dexamethasone outcomes, using propranolol as the positive control illustrated a very substantial anti‐hypoxic effect even much better than dexamethasone in all models. It seems that propranolol would be a safe, potential, and prudent choice to invest in treating COVID‐19 patients.

Magnesium Sulfate Attenuates Lethality and Oxidative Damage Induced by Different Models of Hypoxia in Mice.

Mg2+ is an important cation in our body. It is an essential cofactor for many enzymes. Despite many works, nothing is known about the protective effects of MgSO4 against hypoxia-induced lethality and oxidative damage in brain mitochondria. In this study, antihypoxic and antioxidative activities of MgSO4 were evaluated by three experimental models of induced hypoxia (asphyctic, haemic, and circulatory) in mice. Mitochondria protective effects of MgSO4 were evaluated in mouse brain after induction of different models of hypoxia. Antihypoxic activity was especially pronounced in asphyctic hypoxia, where MgSO4 at dose 600 mg/kg showed the same activity as phenytoin, which used as a positive control (P < 0.001). In the haemic model, MgSO4 at all used doses significantly prolonged latency of death. In circulatory hypoxia, MgSO4 (600 mg/kg) doubles the survival time. MgSO4 significantly decreased lipid peroxidation and protein carbonyl and improved mitochondrial function and glutathione content in brain mitochondria compared to the control groups. The results obtained in this study showed that MgSO4 administration has protective effects against lethality induced by different models of hypoxia and improves brain mitochondria oxidative damage.

Protective effects of ethanolic extract of Lemon Beebrush (Aloysia citrodora) leaf against hypoxia-induced lethality in mice

Lemon Beebrush, known as Lippia citroiodora and Aloysia citrodora is a known medicinal plant in Iran. Many biological activities have been reported from this plant. In spite of many works, nothing is known about protective effect of A. citrodora against hypoxia conditions. In this study, protective effects of A. citrodora leaf extract against hypoxia-induced lethality in mice were evaluated by three experimental models of hypoxia, asphyctic, haemic and circulatory. Its phenol and flavonoid contents and antioxidant activity were also evaluated. Statistically significant protective activities were established in some doses of extract in three models. Antihypoxic activity was especially pronounced in circulatory hypoxia where extract at 62.5 mg kg-1 prolonged the latency for death with respect to control group (p&lt;0.01). The effect was dose dependent. At 250 mg kg-1, it prolonged the latency for death with the same activity of propranolol (20 mg kg-1), that used as positive control (p&gt;0.05). Extract showed weak activity in haemic model. Only at the highest tested dose, 250 mg kg-1, it significantly prolonged latency for death with respect to control group (p&lt;0.05). Extract at this dose showed the same activity of propranolol which used as positive control (p&gt;0.05). In asphytic model, extract at the highest tested dose showed statistically significant activity respect to the control. At 250 mg kg-1, it significantly prolonged the latency for death (26.84 ± 4.11 vs. 19.45 ± 1.13 min, p = 0.0006). At 125 mg kg-1, it also prolonged survival time but this increase was not significantly different. Phenytoin that used as positive control kept mice alive for 29.60 ± 2.51 min (p&lt;0.0001). Extract at 250 mg kg-1 showed the same activity of phenytoin (p&gt;0.05). The total phenolic content was 342.9 ± 11.5 mg gallic acid equivalent/g of extract powder and flavonoid content was 90.2 ± 7.8 mg quercetin equivalent/g of extract powder. IC50 for DPPH radical-scavenging activity was 21.97 ± 2.4 mg/ml. The presence of polyphenols in this plant may be a proposal mechanism for reported antihypoxic activities.

Effects of novel hexahydropyrimidine derivatives as potential ligands of M1 muscarinic acetylcholine receptor on cognitive function, hypoxia-induced lethality, and oxidative stress in rodents

The neurodegenerative diseases have a complex pathogenetic mechanism comprising oxidative stress and receptor system dysfunction caused by various damaging factors such as, for example, brain hypoxia. The purpose of this study was to elucidate the influence of hexahydropyrimidine derivatives on learning, memory, and orientation and locomotor activities in the passive avoidance (PA) and open field (OF) tests and to evaluate these compounds for their potential antihypoxic and antioxidant action on normobaric hypercapnic hypoxia and toxic hypoxia models. We demonstrated that compounds 1a and 1e administered as a single 100 mg/kg dose (p.o.) one hour before the tests increased the latency time to enter the dark compartment for the first time and reduced the time spent in the dark compartment on the 2nd, 7th, and 14th days of PAT and increased the number of squares crossed and hole-pokings in the OF test. It was also shown that single administration of compounds 1a and 1e (in 100 mg/kg dose, p.o.) one hour before generation of hypoxia increased the life span of mice under normobaric hypoxia by 30% (P < 0.05) and, after injection of sodium nitroprusside, they decreased the malondialdehyde (MDA) level and increased the catalase level in the brain of mice. According to molecular docking results, compounds 1а and 1е are bound in the orthosteric active site of M1 muscarinic receptor via supramolecular interactions with a number of functional amino acids.The results indicate that hexahydropyrimidine derivatives have a beneficial effect on the memory, learning processes, and orientation and locomotor activities of rats in an unfamiliar environment and exhibit antihypoxic and antioxidant activities under hypoxia in mice. The cognitive enhancement can be mediated by the effect of lead compounds on the M1 muscarinic acetylcholine receptor.

Protective effects of methanolic extract of Vicia cracca against hypoxia-induced lethality in mice

Vicia genus has 45 species in Iran. Many protective and biological activities have been reported from these species. In spite of many works, nothing is known about protective effect of V. cracca against hypoxia conditions. In this study, protective effects of V. cracca extract against hypoxia-induced lethality in mice were evaluated by three experimental models of hypoxia, asphyctic, haemic and circulatory. Statistically significant protective activities were observed in some doses of extract in three models. Antihypoxic activity was especially pronounced in asphyctic model. Extract at 200 mg/kg prolonged survival time (27.37 ± 4.0 min) but was not comparable with that of phenytoin (39.80 ± 1.92). At 100 mg/kg it also prolonged survival time (24.76 ± 3.7 min) which was so higher than control group. In haemic model, V. cracca extract significantly and dose dependently prolonged survival time as compared to control group. At 200 mg/kg, extract was being capable of keeping the mice alive for 15.38 ± 1.93 min. It was also effective in circulatory model. V. cracca extract at 200 mg/kg prolonged survival time (16.84 ± 1.47 min) that was statistically significant as compared to control group (13.14 ± 0.51 min). V. cracca extract showed a very good protective effect against the hypoxia in some models. Specifically, they produced significant and dose-dependent effect on the model of asphytic and haemic hypoxia. The presence of polyphenols in this plant may be a proposal mechanism for reported antihypoxic activities of this plant.

Antihypoxic activities of constituents from Arenaria kansuensis

BackgroundIn previous investigation, we have identified antioxidative effects of water-soluble ethanolic extracts (named as AKE) from Arenaria kansuensis and inferred that these extracts or their constituents may also have antihypoxic activity. A. kansuensis has been widely used in traditional Tibetan medicine for altitude sickness (AS) and has been known as the herb of anti-inflammatory and hypoxia resistance for a long time. PurposeThe purpose of this study is to evaluate protective effects of AKE and its major constituents against hypoxia-induced lethality in mice and RSC96 cells. Study design and methodsHypoxia-induced lethality in mice was investigated by 3 experimental animal models of hypoxia. Meanwhile, we established a RSC96 cell model of hypoxia which applied to screen and assess the anti-hypoxic activity of compounds isolated from A. kansuensis. ResultsResults indicated that AKE dose-dependently prolonged survival time of hypoxia induced lethality in mice compared to vehicle group and exhibited significantly anti-hypoxic effect. AKE also enhanced the number of red blood cells (RBC) and the concentration of hemoglobin (HB). 8 compounds were bio-guided separated and purified from AKE based on the animal model and cell model of hypoxia. Among which pyrocatechol (C16) and tricin 7-O-β-d-glucopyranoside (C13) were confirmed to express better protective effects on cell damage induced by hypoxia, suggesting that these two compounds are major active constituents of AKE for anti-hypoxia. ConclusionThis study demonstrated that pyrocatechol and tricin 7-O-β-d-glucopyranoside could be therapeutic candidates for treatment of AS. It is the first time to find the major active constituents of AKE for anti-hypoxia. Meanwhile, a RSC96 cell model of hypoxia was established to screen anti-hypoxic activity of compounds for the first time.

Suppression of Bim by microRNA-19a may protect cardiomyocytes against hypoxia-induced cell death via autophagy activation.

Microvascular obstruction (MO), one of unfavorable complications of percutaneous coronary intervention (PCI), is responsible for the lost benefit of reperfusion therapy. Determination of microRNA-19a, a member of the miR-17-92 cluster, using quantitative real-time polymerase chain reaction (PCR) revealed notably down-regulated microRNA-19a, in myocardium with MO. Nonetheless, the role of miR-19a in MO and the underlying mechanism remains to be elucidated. To this end, an in vitro microembolization model in cardiomyocytes was used. Our data revealed that hypoxic exposure prompted cardiomyocyte apoptosis in a time-dependent manner accompanied by reduced miR-19a. miR-19a overexpression clearly ameliorated hypoxia-induced cell death (necrosis and apoptosis), at least in part, through switching on autophagy. Further dual-luciferase reporter assay and immunoblotting studies demonstrated that miR-19a-induced cytoprotection might be achieved in part through modulation of the specific target Bcl-2 interacting mediator of cell death, Bim, an apoptotic activator. Bim sufficiently interfered with miR-19a-induced LC3 conversion and increased cardiomyocyte apoptosis under hypoxia. Moreover, cardiomyocytes pretreated with 3-methyladenine conferred resistance to the cytoprotective effect of miR-19a and displayed notably increased TUNEL staining and caspase-3 activity. In conclusion, miR-19a protected cardiomyocytes against hypoxia-induced lethality at least in part via Bim suppression and subsequently autophagy activation.

The Antihypoxic and Sedative Activity of the Dry extract from Asperula odorata L

Introduction: Sweet Woodruff (Asperula odorata L.) is a perennial herb that is spread throughout the territory of Ukraine. This herb is widely used in folk medicine of Ukraine as a sedative medicine at neurosis, neurasthenia, hysteria, depression, applied locally at allergic rash, and it is also used at metritis and colpitis in homeopathy. Materials and methods: The air-dried herb of Asperula odorata was degreased with chloroform and then treated with the mixture of ethyl acetate-alcohol (8:2) to obtain a dry extract. Sedative activity was studied in the “open field” test. The protective effect of dry extract against hypoxia-induced lethality in mice was evaluated by experimental model of asphyctic hypoxia. HPLC analysis was used to identify the phenolic compounds in the dry extract. Results: The dry extract at the dose of 100 mg/kg in the “open field” test caused a signifi cant dose-dependent (p>0.05) decreasing of loco motor activity which has evidenced by potent sedative activity. The dry extract at the dose of 100 mg/kg showed a potent anti-hypoxic activity which has been confirmed by increasing mice lifetime by 34.8% in conditions of model hypoxia. The dry extract reveals a sedative activity on the CNS but it doesn’t have an adverse effect on skeletal muscle tone and coordination. In the dry extract, 16 phenolic compounds have been identified and quantified. Chlorogenic acid and cynarozide are dominant compounds. Conclusion: Our data have provided a rational base for the folkloric use of the dry extract from Sweet Woodruff as a sedative and antihypoxic drug.

Antihypoxic activities of the golden Chanterelle Mushroom, Cantharellus cibarius (higher Basidiomycetes).

Cantharellus cibarius is an edible mushroom with worldwide distribution. Because of its good radical scavenging and strong iron-chelating activity, this mushroom was nominated for assay of antihypoxic activity. Protective effects of Chanterelle extract against hypoxia-induced lethality in mice were evaluated by 3 experimental models of hypoxia: asphyctic, hemic, and circulatory. Antihypoxic activity was especially pronounced in the hemic model. The effect was dose dependent. C. cibarius extract (600 mg kg-1) kept the mice alive for 10.07 ± 1.18 min. It significantly (P < 0.0001) and dose dependently prolonged survival time compared to control group (7.00 ± 0.63 min). Extract at 300 mg kg-1 prolonged survival time to 9.94 ± 0.87 min, which was statistically significant (P < 0.0001) compared to control group. In circulatory model, C. cibarius extract (600 mg kg-1) was effective. It prolonged latency for death significantly with regard to the control group (15.18 ± 4.21 vs. 9.84 ± 0.75 min; P < 0.001). At 300 mg kg-1, the extract also prolonged survival time (13.57 ± 0.87 min), and this effect was also statistically significant compared to the control group (P < 0.01). Extract showed no activity in the asphyctic model. Mice in the control group died of hypoxia in 28.20 ± 3.27 min. Extract (600 mg kg-1) prolonged latency for death, but this activity was not statistically significant (P < 0.05). Phenytoin prolonged latency for death to 55.00 ± 6.05 min (P < 0.0001).

The effect of DN (dominant-negative) Ku70 and reoxygenation on hypoxia cell-kill: Evidence of hypoxia-induced potentially lethal damage

Purpose: To study the effect of DN (dominant-negative) Ku70 and reoxygenation on the hypoxia-induced cell-kill.Materials and methods: Cell lines were human colorectal carcinoma HCT8 and HT29 cells and their respective derivatives, v-HCT8 and v-HT29 infected with DNKu70-containing adenovirus. Cells were plated in glass tubes and made hypoxic by flushing N2 gas containing 0, 0.1 or 0.5% O2. Cell survival was determined by colony formation assay immediately after 0–96 h hypoxia. To reoxygenate medium were replaced fresh following 48 or 72 h in hypoxia and cells were incubated in aerobic environment for 2–24 h before survival assay.Results: When incubated in hypoxia, cells lost reproductive capability ∼ exponentially as a function of time in hypoxia, and depending on the O2 concentration. DNKu70 rendered cells more prone to hypoxia-induced cell-kill. Following reoxygenation cell survival increased rapidly but without detectable cell proliferation during first 24 hours. This evinced hypoxia-induced potentially lethal damage (PLD) that was repairable upon reoxygenation. DNKu70 did not significantly inhibit this repair.Conclusion: Hypoxia-induced cell lethality was facilitated by DNKu70, but substantially repaired upon reoxygenation. This may have negative impact on the effect of reoxygenation in cancer therapy.

Oxygen levels affect axon guidance and neuronal migration in Caenorhabditis elegans

Oxygen deprivation can cause severe defects in human brain development, yet the precise cellular and molecular consequences of varying oxygen levels on nervous system development are unknown. We found that hypoxia caused specific axon pathfinding and neuronal migration defects in C. elegans that result from the stabilization of the transcription factor HIF-1 (hypoxia-inducible factor 1) in neurons and muscle. Stabilization of HIF-1 through removal of the proteasomal HIF-1 degradatory pathway phenocopies the hypoxia-induced neuronal defects. Hypoxia-mediated defects in nervous system development depended on signaling through the insulin-like receptor DAF-2, which serves to control the level of reactive oxygen species that also affects axon pathfinding. Hypoxia exerted its effect on axon pathfinding, at least in part, through HIF-1-dependent regulation of the Eph receptor VAB-1. HIF-1-mediated upregulation of VAB-1 protected embryos from hypoxia-induced lethality, but increased VAB-1 levels elicited aberrant axon pathfinding. Similar genetic pathways may cause aberrant human brain development under hypoxic conditions.

The protective effect of Allium sativum L. clove aqueous and methanolic extracts against hypoxia-induced lethality in mice.

The antihypoxic activity of Allium sativum clove (garlic) aqueous and methanolic extracts was studied in mice. The extracts of garlic showed that the antihypoxic effect was dose-dependent. The minimum effective doses of aqueous and methanolic extracts were 0.2 g/kg and 5.12 g/kg, respectively. Phenytoin, 50 mg/kg, and R-phenylisopropyladenosine (R-PIA), 1.6 mg/kg (R-PIA) as positive controls increased survival time up to 52.5 +/- 2.9 min and 120.5 +/- 6 min, respectively, compared to normal saline (34.73 +/- 0.71 min). The high doses of aqueous (16.9 g/kg) and methanolic (12.8 g/kg) extracts increased survival time up to 73.17 +/- 4.9 and 68.41 +/- 3.7, respectively. These results indicated that the extracts of A. sativum cloves have a protective effect against hypoxia-induced lethality in mice.

Caenorhabditis elegans p53: role in apoptosis, meiosis, and stress resistance.

We have identified a homolog of the mammalian p53 tumor suppressor protein in the nematode Caenorhabditis elegans that is expressed ubiquitously in embryos. The gene encoding this protein, cep-1, promotes DNA damage-induced apoptosis and is required for normal meiotic chromosome segregation in the germ line. Moreover, although somatic apoptosis is unaffected, cep-1 mutants show hypersensitivity to hypoxia-induced lethality and decreased longevity in response to starvation-induced stress. Overexpression of CEP-1 promotes widespread caspase-independent cell death, demonstrating the critical importance of regulating p53 function at appropriate levels. These findings show that C. elegans p53 mediates multiple stress responses in the soma, and mediates apoptosis and meiotic chromosome segregation in the germ line.

Frequency of sexual dysfunction in depressed adults and impact on quality of life

The protective effect of moclobemide, a reversible and highly selective inhibitor of monoamine oxidase-A, against hypoxia-induced lethality was investigated in the present experiment. Moclobemide showed an apparent protective potency against hypoxia and significantly prolonged the latencies for convulsions and death in a dose-dependent manner. Hypothermia is known to protect animals from hypoxia. Moclobemide also decreased body temperature in mice; however, the hypothermic effect was unrelated to the antihypoxic effect. These results suggest that the protective effect of moclobemide in hypoxia is not due to a decrease in body temperature.

The role of H1- and H2-receptors in the effect of compound 48/80 in the asphyxiation and body temperature of mice.

Contribution of histamine H1- and H2-receptors to the effect of compound 48/80, a potent histamine releaser, upon asphyxiation and body temperature in mice was investigated in the present experiments. Compound 48/80 showed an apparent protective potency against hypoxia and significantly prolonged the latencies for convulsions and death in a dose-dependent manner. Compound 48/80 also decreased the body temperature, which was in relation with the antihypoxic effect. Both the H1-receptor antagonist, dimethindene, and the H2-receptor antagonist, ranitidine, attenuated the hypothermic effect of compound 48/80, indicating the involvement of central histamine through both the H1- and H2-receptors. Ranitidine had no effect on the protective effect of compound 48/80 against hypoxia-induced lethality, whereas dimethindene completely antagonized it. These results suggest that the protective effect of compound 48/80 against hypoxia is mediated through histamine H1-receptors and is not related to its ability to induce hypothermia.

The protective effect of moclobemide against hypoxia-induced lethality in mice is not due to a decrease in body temperature

The protective effect of moclobemide, a reversible and highly selective inhibitor of monoamine oxidase-A, against hypoxia-induced lethality was investigated in the present experiment. Moclobemide showed an apparent protective potency against hypoxia and significantly prolonged the latencies for convulsions and death in a dose-dependent manner. Hypothermia is known to protect animals from hypoxia. Moclobemide also decreased body temperature in mice; however, the hypothermic effect was unrelated to the antihypoxic effect. These results suggest that the protective effect of moclobemide in hypoxia is not due to a decrease in body temperature.

The role of H1 and H2 receptors in the effect of compound 48/80 on hypoxia-induced lethality and body temperature in mice

The role of H1 and H2 receptors in the effect of compound 48/80 on hypoxia-induced lethality and body temperature in mice

Protection by Disulfiram and Diethyldithiocarbamate against Hypoxia-Induced Lethality in Mice

The effects of disulfiram (DS) and its major metabolite, diethyldithiocarbamate (DEDC), on the survival time under normobaric and hypobaric hypoxia were examined in mice. At an ambient temperature of 24 degrees C, DS at 0.5-3.0 mmol/kg (i.p.) caused a marked dose-dependent prolongation of the survival time in mice subjected to both types of hypoxia. DEDC also prolonged the survival time, but the effect was less at its higher doses with decreased brain superoxide dismutase. The maximum effects of DS and DEDC were found at 3 hr and 1 hr after injection, respectively. Of the metabolites of DEDC, the copper complex with DEDC caused a significant effect, whereas neither diethylamine nor carbon disulfide did. Furthermore, DS, DEDC and copper complex caused marked hypothermia, and the time course changes of hypothermia by DS and DEDC closely paralleled those of the degree of anti-hypoxic effects, respectively. At an ambient temperature of 36 degrees C, in which the body temperature was maintained near the normal level, both DS and DEDC still exhibited a weak anti-hypoxic effect. These results suggest that DEDC itself, formed as a metabolite of DS, and partly the copper complex produced the anti-hypoxic effect, which could not be explained by concomitant hypothermia alone.