Fructose improves titanium dioxide nanoparticles induced alterations in developmental competence of mouse oocytes.

AIMS: We investigated the effects of intraperitoneal injections of titanium dioxide nanoparticles (TiO2 NPs, 100 mg/kg) for 5 consecutive days on the developmental competence of murine oocytes. Furthermore, study the effects of TiO2 NPs on antioxidant and oxidative stress biomarkers, as well as their effects on expression of apoptotic and hypoxia inducing factor-1α (HIF1A) protein translation. Moreover, the possible ameliorating effects of intraperitoneal injections of fructose (2.75 mM/ml) was examined. MATERIALS AND METHODS: Thirty sexually mature (8-12 weeks old; ~ 25 g body weight) female mice were used for the current study. The female mice were assigned randomly to three treatment groups: Group1 (G1) mice were injected intraperitoneal (ip) with deionized water for 5 consecutive days; Group 2 (G2) mice were injected ip with TiO2 NPs (100 mg/kg BW) for 5 consecutive days; Group 3 (G3) mice were injected ip with TiO2 NPs (100 mg/kg BW + fructose (2.75 mM) for 5 consecutive days. RESULTS: Nano-titanium significantly decreased expression of GSH, GPx, and NO, expression of MDA and TAC increased. The rates of MI, MII, GVBD and degenerated oocytes were significantly less for nano-titanium treated mice, but the rate of activated oocytes was significantly greater than those in control oocytes. TiO2 NPs significantly increased expression of apoptotic genes (BAX, Caspase 3 and P53) and HIF1A. Intraperitoneal injection of fructose (2.75 mM/kg) significantly alleviated the detrimental effects of TiO2 NPs. Transmission electron microscopy indicated that fructose mitigated adverse effects of TiO2 NPs to alter the cell surface of murine oocytes. CONCLUSION: Results of this study suggest that the i/p infusion of fructose for consecutive 5 days enhances development of murine oocytes and decreases toxic effects of TiO2 NPs through positive effects on oxidative and antioxidant biomarkers in cumulus-oocyte complexes and effects to inhibit TiO2-induced increases in expression of apoptotic and hypoxia inducing factors.

EFFICACY OF TOLAZOLINE AND VATINOXAN IN REDUCING ADVERSE EFFECTS OF BUTORPHANOL-AZAPERONE-MEDETOMIDINE IMMOBILIZATION IN ROCKY MOUNTAIN ELK (CERVUS CANADENSIS).

A mixture of butorphanol, azaperone, and medetomidine (BAM) is frequently used for immobilization of North American hoofstock. Common adverse effects include respiratory depression, hypoxemia, and bradycardia. In this nonblinded crossover study the efficacy of two a-2 adrenergic antagonists, tolazoline and vatinoxan, were evaluated in alleviating adverse effects of BAM in Rocky Mountain elk (Cervus canadensis). Early administration of these antagonists was hypothesized to cause an increase in heart rate, respiratory rate, partial pressure of oxygen (PaO2) and hemoglobin oxygen saturation (SpO2), as well as reduction in mean arterial blood pressure without affecting sedation levels. Eight captive adult female elk were immobilized on three separate occasions at least 14 d apart with 0.15 mg/kg butorphanol, 0.05 mg/kg azaperone, and 0.06 mg/kg medetomidine. Tolazoline (2 mg/kg IM), vatinoxan (3 mg/mg medetomidine IV) or sterile saline (2 ml IM) were administered 20 min postinduction. The BAM caused hypoxemia, bradycardia, and moderate hypertension, and because of the severe hypoxemia observed, all animals received intratracheal oxygen throughout immobilization. Heart rate, respiratory rate, rectal temperature, SpO2, PaO2, and systolic, diastolic, and mean arterial blood pressure were monitored every 5 min throughout the immobilization. Intramuscular tolazoline caused a brief but significant drop in mean arterial pressure compared with controls and a brief but nonsignificant increase in heart rate. Vatinoxan caused a significant drop in blood pressure and a brief significant increase in heart rate. Changes in respiratory rates and PaO2 were not observed with either antagonist; however, all animals received oxygen, which may have influenced this result. The depth of sedation was unchanged after administration of either drug.

Hypoxia inducible factor-1α facilitates transmissible gastroenteritis virus replication by inhibiting type I and type III interferon production.

Transmissible gastroenteritis virus (TGEV) is characterized by watery diarrhea, vomiting, and dehydration and is associated with high mortality especially in newborn piglets, causing significant economic losses to the global pig industry. Hypoxia inducible factor-1α (HIF-1α) has been identified as a key regulator of TGEV-induced inflammation, but understanding of the effect of HIF-1α on TGEV infection remains limited. This study found that TGEV infection was associated with a marked increase in HIF-1α expression in ST cells and an intestinal organoid epithelial monolayer. Furthermore, HIF-1α was shown to facilitate TGEV infection by targeting viral replication, which was achieved by restraining type I and type III interferon (IFN) production. In vivo experiments in piglets demonstrated that the HIF-1α inhibitor BAY87-2243 significantly reduced HIF-1α expression and inhibited TGEV replication and pathogenesis by activating IFN production. In summary, we unveiled that HIF-1α facilitates TGEV replication by restraining type I and type III IFN production in vitro, ex vivo, and in vivo. The findings from this study suggest that HIF-1α could be a novel antiviral target and candidate drug against TGEV infection.

The influence of hypoxaemia, hypotension and hypercapnia (among other factors) on quality of recovery from general anaesthesia in horses.

OBJECTIVE: To investigate the effect of hypoxaemia, hypotension and hypercapnia, among others, on quality of recovery from general anaesthesia in horses. STUDY DESIGN: Retrospective, single-centre study. ANIMALS: A sample of 1226 horses that underwent general anaesthesia between June 2017 and June 2021. METHODS: Horses and ponies weighing > 200 kg, aged > 6 months, anaesthetized using a xylazine- or medetomidine-isoflurane balanced anaesthesia protocol and presenting a complete anaesthetic record were included. Data were extracted from the clinic record system and from the original anaesthesia records. Recoveries were divided into 'good' and 'bad' based on the available recovery scores. Influence of hypoxaemia [PaO2 < 60 mmHg (7.99 kPa)], hypotension (mean arterial pressure < 70 mmHg for at least 15 minutes) and hypercapnia [PaCO2 > 60 mmHg (7.99 kPa)], anaesthesia protocol, body weight, age, breed, sex, American Society of Anesthesiologists status, type of procedure, emergency or nonemergency, duration of anaesthesia, positioning, times spent in lateral and sternal recumbency during recovery, time until standing and nonassisted or assisted recovery on the assigned recovery score (good/bad) were investigated using generalized linear regression analysis (p < 0.05). RESULTS: Hypoxaemia and prolonged duration of anaesthesia were significantly associated with a bad recovery score. No other factors had a significant influence on recovery quality. CONCLUSION AND CLINICAL RELEVANCE: Hypoxaemia and prolonged anaesthesia duration have a negative effect on quality of anaesthetic recovery in horses. Clinically, this highlights the importance of keeping anaesthetic time as short as possible and to monitor oxygenation and treat hypoxaemia as soon as possible.

Metabolomics and transcriptomics of embryonic livers reveal hypoxia adaptation of Tibetan chickens.

BACKGROUND: Exploring the hypoxia adaptation mechanism of Tibetan chicken is of great significance for revealing the survival law of Tibetan chicken and plateau animal husbandry production. To investigate the hypoxia adaptation of Tibetan chickens (TBCs), an integrative metabolomic-transcriptomic analysis of the liver on day 18 of embryonic development was performed. Dwarf laying chickens (DLCs), a lowland breed, were used as a control. RESULTS: A total of 1,908 metabolites were identified in both TBCs and DLCs. Energy metabolism and amino acid metabolism related differentially regulated metabolites (DRMs) were significantly enriched under hypoxia. Important metabolic pathways including the TCA cycle and arginine and proline metabolism were screened; PCK1, SUCLA2, and CPS1 were found to be altered under hypoxic conditions. In addition, integrated analysis suggested potential differences in mitochondrial function, which may play a crucial role in the study of chicken oxygen adaptation. CONCLUSIONS: These results suggest that hypoxia changed the gene expression and metabolic patterns of embryonic liver of TBCs compared to DLCs. Our study provides a basis for uncovering the molecular regulation mechanisms of hypoxia adaptation in TBCs with the potential application of hypoxia adaptation research for other animals living on the Qinghai-Tibet plateau, and may even contribute to the study of diseases caused by hypoxia.

Transcriptomic analysis of the hypoxia-inducible factor 1α impact on the gene expression profile of chicken fibroblasts under hypoxia.

Hypoxia-inducible factor 1 (HIF-1) is a transcriptional regulator that mediates cellular adaptive responses to hypoxia. Hypoxia-inducible factor 1α (HIF-1α) is involved in the development of ascites syndrome (AS) in broiler chickens. Therefore, studying the effect of HIF-1α on the cellular transcriptome under hypoxic conditions will help to better understand the mechanism of HIF-1α in the development of AS in broilers. In this study, we analyzed the gene expression profile of the chicken fibroblast cell line (DF-1) under hypoxic conditions by RNA-seq. Additionally, we constructed the HIF-1α knockdown DF-1 cell line by using the RNAi method and analyzed the gene expression profile under hypoxic conditions. The results showed that exposure to hypoxia for 48 h had a significant impact on the expression of genes in the DF-1 cell line, which related to cell proliferation, stress response, and apoptosis. In addition, after HIF-1α knockdown more differential expression genes appeared than in wild-type cells, and the expression of most hypoxia-related genes was either down-regulated or remained unchanged. Pathway analysis results showed that differentially expressed genes were mainly enriched in pathways related to cell proliferation, apoptosis, and oxidative phosphorylation. Our study obtained transcriptomic data from chicken fibroblasts at different hypoxic times and identified the potential regulatory network associated with HIF-1α. This data provides valuable support for understanding the transcriptional regulatory mechanism of HIF-1α in the development of AS in broilers.

Effects of Butorphanol on Respiration in White Rhinoceros (Ceratotherium simum) Immobilized with Etorphine-Azaperone.

This article reports on respiratory function in white rhinoceros (Ceratotherium simum) immobilized with etorphine-azaperone and the changes induced by butorphanol administration as part of a multifaceted crossover study that also investigated the effects of etorphine or etorphine-butorphanol treatments. Six male white rhinoceros underwent two immobilizations by using 1) etorphine-azaperone and 2) etorphine-azaperone-butorphanol. Starting 10 min after recumbency, arterial blood gases, limb muscle tremors, expired minute ventilation, and respiratory rate were evaluated at 5-min intervals for 25 min. Alveolar to arterial oxygen gradient, expected respiratory minute volume, oxygen consumption, and carbon dioxide production were calculated. Etorphine-azaperone administration resulted in hypoxemia and hypercapnia, with increases in alveolar to arterial oxygen gradient, oxygen consumption, and carbon dioxide production, and a decrease in expired minute ventilation. Muscle tremors were also observed. Intravenous butorphanol administration in etorphine-azaperone-immobilized white rhinoceros resulted in less hypoxemia and hypercapnia; a decrease in oxygen consumption, carbon dioxide production, and expired minute ventilation; and no change in the alveolar to arterial oxygen gradient and rate of breathing. We show that the immobilization of white rhinoceros with etorphine-azaperone results in hypoxemia and hypercapnia and that the subsequent intravenous administration of butorphanol improves both arterial blood oxygen and carbon dioxide partial pressures.

Hypoxia-related Y RNA fragments as a novel potential biomarker for distinguishing metastatic oral melanoma from non-metastatic oral melanoma in dogs.

Hypoxia may promote tumor progression, and hypoxically altered noncoding RNA (ncRNA) expression may play a role in metastasis. Canine oral melanoma (COM) frequently metastasizes, and ncRNA expression under hypoxia may be clinically significant. We aimed to elucidate ncRNA fragments whose expression is altered by hypoxia in COM-derived primary KMeC and metastatic LMeC cell lines using next-generation sequencing to validate these results in qRT-PCR, and then compare expression between metastatic and non-metastatic COM. The NGS analysis and subsequent qRT-PCR validation were performed using hypoxic and normoxic KMeC and LMeC cells, and clinical samples [tumor tissue, plasma, and plasma-derived extracellular vesicles] obtained from dogs with metastatic or non-metastatic melanoma were analyzed with qRT-PCR. Y RNA was significantly decreased in metastatic LMeC cells versus primary KMeC cells in hypoxic and normoxic conditions. The expression of Y RNA was decreased in dogs with metastatic melanoma versus those with non-metastatic melanoma for all clinical sample types, reflecting the pattern found with hypoxia. Receiver operating characteristic analysis demonstrated that Y RNA level is a promising biomarker for discriminating metastatic from non-metastatic melanoma in plasma [area under the curve (AUC) = 0.993, p < 0.0001] and plasma-derived extracellular vesicles (AUC = 0.981, p = 0.0002). Overall, Y RNA may be more resistant to hypoxic stress in the metastatic than the non-metastatic state for COM. However, further investigation is required to elucidate the biological functions of Y RNA under hypoxic conditions.

Hypoxia promotes proliferation and inhibits myogenesis in broiler satellite cells.

Breast muscle myopathies in broilers compromise meat quality and continue to plague the poultry industry. Broiler breast muscle myopathies are characterized by impaired satellite cell (SC)-mediated repair, and localized tissue hypoxia and dysregulation of oxygen homeostasis have been implicated as contributing factors. The present study was designed to test the hypothesis that hypoxia disrupts the ability of SC to differentiate and form myotubes, both of which are key components of myofiber repair, and to determine the extent to which effects are reversed by restoration of oxygen tension. Primary SC were isolated from pectoralis major of young (5 d) Cobb 700 chicks and maintained in growth conditions or induced to differentiate under normoxic (20% O2) or hypoxic (1% O2) conditions for up to 48 h. Hypoxia enhanced SC proliferation while inhibiting myogenic potential, with decreased fusion index and suppressed myotube formation. Reoxygenation after hypoxia partially reversed effects on both proliferation and myogenesis. Western blotting showed that hypoxia diminished myogenin expression, activated AMPK, upregulated proliferation markers, and increased molecular signaling of cellular stress. Hypoxia also promoted accumulation of lipid droplets in myotubes. Targeted RNAseq identified numerous differentially expressed genes across differentiation under hypoxia, including several genes that have been associated with myopathies in vivo. Altogether, these data demonstrate localized hypoxia may influence SC behavior in ways that disrupt muscle repair and promote the formation of myopathies in broilers.

Use of molidustat, a hypoxia-inducible factor prolyl hydroxylase inhibitor, in chronic kidney disease-associated anemia in cats.

BACKGROUND: Erythropoietic effects of molidustat, a hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitor, were previously demonstrated in healthy cats. OBJECTIVE: To evaluate the safety and erythropoietic effects of daily PO administration of molidustat in anemic cats with chronic kidney disease (CKD). ANIMALS: Twenty-one client-owned CKD cats (4-17 years old) with anemia. METHODS: Multicenter field study; randomized, masked, and placebo-controlled. Cats were treated PO once daily for 28 days with suspensions of control product (CP; n = 6) or 5 mg/kg of molidustat (n = 15). Hematocrit (HCT) was evaluated at weekly intervals. Individual cat treatment success was defined as a ≥4% point increase in HCT compared to baseline. RESULTS: Control group mean HCT remained low throughout the study (20.1%-23.4%). Mean HCT of molidustat-treated cats increased weekly, and a significant increase compared to baseline (23.6%) was first observed on Day 21 (27.3%; P < .001; 95% confidence interval [CI], 1.69-5.67). Compared to CP group, mean HCT was significantly higher on Day 21 (27.3% vs 20.1%; P < .001; 95% CI, 2.91-10.75) but not significantly higher on Day 28 (27.8% vs 23.4%; P = .06; 95% CI, -0.23 to 9.88). The number of individual treatment successes on Day 28 was higher among remaining molidustat-treated cats (7/14) compared to remaining control cats (1/5), but there was no significant difference between groups. CONCLUSIONS AND CLINICAL IMPORTANCE: Daily PO molidustat administration may stimulate a clinically relevant erythropoietic response in anemic cats with CKD. This HIF-PH inhibitor may be an alternative for managing anemia in cats compared to recombinant EPO treatment.

Identification of large yellow croakers (Larimichthys crocea) scavenger receptor genes: Involvement in immune response to Pseudomonas plecoglossicida infection and hypoxia-exposure experiments.

Scavenger receptors (SRs) are pattern recognition receptors involved in the innate immune defense against pathogen infection in fish. However, there has not been much research done on teleosts. In this study, 18 members of the SR gene family were found in large yellow croaker. The identification of the SR gene family showed that the protein length of SR members in large yellow croaker were quite different, and most SR genes were distributed in nuclear and endoplasmic. The evolutionary relationship, exon/intron structure and motif analysis revealed that members of the SR gene family were highly conserved. The results of the expression profiles after Pseudomonas plecoglossicida infection and hypoxia-exposure demonstrated that SR members were involved in inflammatory reactions. Especially, COLEC12 and SCARF1 exhibited substantial changes in response to both P. plecoglossicida and hypoxia stress, indicating their possible immunological functions. The result of this study revealed that SR genes played a vital part in the innate immune response of large yellow croaker, and would give important details for a deeper comprehension of the SR gene family's regulation mechanism under various conditions in large yellow croaker.

Asiatic acid increased locomotor and head width by inducing brain-derived neurotrophic factor in intrauterine hypoxia-exposed zebrafish.

Background: Hypoxia ischemia leads to abnormal behavior and growth. Prenatal hypoxia also decreases brain adaptive potential, which can cause fatal effects such as cell death. Asiatic acid (AA) in Centella asiatica is a neuroprotector through antioxidant and anti-inflammatory activities. Aim: This study aimed to analyze the effect of AA as a neuroprotector against hypoxia during intrauterine development on locomotor activity, head width, and brain-derived neurotrophic factor (BDNF) expression. Methods: The true experimental laboratory research used a posttest control-only design. Zebrafish embryos (Danio rerio) aged 0-2 dpf (days postfertilization) were exposed to hypoxia with oxygen levels reaching 1.5 mg/l. Then, AA was administered at successive concentrations, namely, 0.36, 0.72, and 1.45 µg/ml, at 2 hpf (hours postfertilization), 3, 6, and 9 dpf. Head width, velocity activity, and BDNF expression were observed. Results: Intrauterine hypoxia significantly decreased head width, velocity rate, and BDNF expression (<0.001). Administration of AA at all concentrations and age 9 dpf to zebrafish larvae with intrauterine hypoxia exposure increased head width ( p < 0.0001), velocity (p < 0.05), and relative mRNA expression of BDNF (p < 0.05). Conclusion: AA is potentially neuroprotective to the brain in zebrafish larvae exposed to hypoxia during intrauterine development.

Salmonella adhesion is decreased by hypoxia due to adhesion and motility structure crosstalk.

Initial stages of Salmonella Typhimurium infection involve a series of coordinated events aimed at reaching, attaching to, and invading host cells. Virulence factors such as flagella, fimbriae, and secretion systems play crucial roles in these events and are regulated in response to the host environment. The first point of contact between the pathogen and host is the intestinal epithelial layer, which normally serves as a barrier against invading pathogens, but can also be an entry site for pathogens. The integrity of this barrier can be modulated by the hypoxic environment of the intestines, created by the presence of trillions of microbes. Variable oxygen concentrations can strongly affect many functions of the gut, including secretion of cytokines and growth factors from the host site and affect the ability of Salmonella to persist, invade, and replicate. In this study, we investigated the first stages of Salmonella Typhimurium infection under hypoxic conditions in vitro and found that low oxygen levels significantly decreased bacterial adhesion. Using adhesion and motility assays, biofilm formation tests, as well as gene expression and cytokine secretion analysis, we identified a hypoxia-specific cross-talk between the expression of type 1 fimbriae and flagella, suggesting that altered flagellin expression levels affect the motility of bacteria and further impact their adhesion level, biofilm formation ability, and innate immune response. Overall, understanding how Salmonella interacts with its variable host environment provides insights into the virulence mechanisms of the bacterium and information regarding strategies for preventing or treating infections. Further research is required to fully understand the complex interplay between Salmonella and its host environment.

Regulatory effects of circular RNA on hypoxia adaptation in chicken embryos.

The Tibetan chicken, a native breed of the Tibetan plateau, is adapted to the high-altitude and hypoxic environment of the plateau. As endogenous molecules, circular RNAs (circRNAs) have been shown to play an important role in the adaptation to hypoxic environments and regulation of angiogenesis. In this study, highland Tibetan and lowland Chahua chicken eggs were incubated in a hypoxic environment and the chorionic allantoic membrane was collected for Ribo-Zero RNA sequencing. A total of 1,414 circRNAs, mostly derived from exons, were identified. Of these, 93 differentially expressed circRNAs were detected between Tibetan and Chahua chickens. Combined with the differentially expressed miRNAs and mRNAs identified in our previous study, we identified four circRNAs (circBRD1, circPRDM2, circPTPRS, and circDENND4C). These circRNAs may act as competing endogenous RNA (ceRNA) to upregulate APOA1 expression by absorbing novel_miR_589, thereby regulating angiogenesis and affecting hypoxia adaptation in chicken embryos. The regulatory circRNAs/novel_miR_589/APOA1 axis provides valuable evidence for a better understanding of the specific functions and molecular mechanisms of circRNAs in plateau hypoxia adaptation in Tibetan chickens.

The chorioallantoic membrane (CAM) is a key respiratory organ involved in early chicken embryo development. It is abundant in blood vessels and plays an important role in gas exchange in the chicken embryo. Hypoxia, a state of insufficient oxygen, can lead to abnormal angiogenesis. Tibetan chickens (TC), owing to their unique genetic background, have adapted to a hypoxic environment and are able to maintain the balance of angiogenesis. In this study, we aimed to identify potential circular RNAs (circRNAs) and their key regulatory networks related to angiogenesis by comparing highland and lowland chickens. Using RNA sequencing, we identified 93 circRNAs that were differentially expressed in the CAM between highland and lowland chickens. The key circRNAs and circRNA-miRNA-mRNA regulatory networks that affect angiogenesis were constructed using bioinformatic methods. This work provides a novel analysis of the molecular mechanisms of hypoxia adaptation in TC.

Hypoxia tolerance in fish depends on catabolic preference between lipids and carbohydrates.

Hypoxia is a common environmental stress factor in aquatic organisms, which varies among fish species. However, the mechanisms underlying the ability of fish species to tolerate hypoxia are not well known. Here, we showed that hypoxia response in different fish species was affected by lipid catabolism and preference for lipid or carbohydrate energy sources. Activation of biochemical lipid catabolism through peroxisome proliferator-activated receptor alpha (Pparα) or increasing mitochondrial fat oxidation in tilapia decreased tolerance to acute hypoxia by increasing oxygen consumption and oxidative damage and reducing carbohydrate catabolism as an energy source. Conversely, lipid catabolism inhibition by suppressing entry of lipids into mitochondria in tilapia or individually knocking out three key genes of lipid catabolism in zebrafish increased tolerance to acute hypoxia by decreasing oxygen consumption and oxidative damage and promoting carbohydrate catabolism. However, anaerobic glycolysis suppression eliminated lipid catabolism inhibition-promoted hypoxia tolerance in adipose triglyceride lipase (atgl) mutant zebrafish. Using 14 fish species with different trophic levels and taxonomic status, the fish preferentially using lipids for energy were more intolerant to acute hypoxia than those preferentially using carbohydrates. Our study shows that hypoxia tolerance in fish depends on catabolic preference for lipids or carbohydrates, which can be modified by regulating lipid catabolism.

Do air-breathing fish suffer branchial oxygen loss in hypoxic water?

In hypoxia, air-breathing fish obtain O2 from the air but continue to excrete CO2 into the water. Consequently, it is believed that some O2 obtained by air-breathing is lost at the gills in hypoxic water. Pangasionodon hypophthalmus is an air-breathing catfish with very large gills from the Mekong River basin where it is cultured in hypoxic ponds. To understand how P. hypophthalmus can maintain high growth in hypoxia with the presumed O2 loss, we quantified respiratory gas exchange in air and water. In severe hypoxia (PO2: ≈ 1.5 mmHg), it lost a mere 4.9% of its aerial O2 uptake, while maintaining aquatic CO2 excretion at 91% of the total. Further, even small elevations in water PO2 rapidly reduced this minor loss. Charting the cardiovascular bauplan across the branchial basket showed four ventral aortas leaving the bulbus arteriosus, with the first and second gill arches draining into the dorsal aorta while the third and fourth gill arches drain into the coeliacomesenteric artery supplying the gut and the highly trabeculated respiratory swim-bladder. Substantial flow changes across these two arterial systems from normoxic to hypoxic water were not found. We conclude that the proposed branchial oxygen loss in air-breathing fish is likely only a minor inefficiency.

Impacts of acute hypoxia on the short-snouted seahorse metabolism and behaviour.

Seahorses are one of the most unique and enigmatic animals, recognized as flagship species for several conservation issues. Unfortunately, seahorses' populations have been declining and their unique lifestyle may constrain the ability of these animals to evolve in the future climate scenarios. They inhabit shallow coastal waters that display daily or seasonal environmental fluctuations. Yet, few studies have scrutinized the impacts of climate changes on these iconic species. Within this context, the objective of this work was to test the effects of an extreme hypoxia exposure (~27 % dissolved oxygen for approximately 7 h) on the metabolism, behaviour and food intake of the temperate seahorse Hippocampus hippocampus. Regarding metabolism, hypoxia exposure led to a significant reduction in metabolic rates and an increase in ventilation rates. Seahorses showed signs of movement lethargy under oxygen depletion. The results show that a small but extreme exposure to hypoxia is tolerable by seahorses despite inducing metabolic and behavioural changes, that may jeopardize the future development and survival of these iconic organisms.

Hypoxia enhances steroidogenic competence of buffalo (Bubalus bubalis) granulosa cells.

Granulosa cells (GCs) synthesize estrogens needed for follicular growth. However, the effects of hypoxia on steroidogenesis in buffalo GCs remain unclear. In this study, the impacts of hypoxic conditions (5% oxygen) on estrogen synthesis in buffalo GCs were examined. The results showed that hypoxia improved both the expression levels of estrogen synthesis-related genes (CYP11A1, CYP19A1, and 3ß-HSD) and the secretion levels of estradiol in buffalo GCs. Hypoxic conditions promoted the sensitivity of buffalo GCs to FSH. Furthermore, inhibition of cAMP/PKA signaling pathway (H89, a cAMP/PKA signaling pathway inhibitor) reduced both the expression levels of estrogen synthesis-related genes (CYP11A1, CYP19A1, and 3ß-HSD) and the secretion levels of estradiol in hypoxia-cultured buffalo GCs. Besides, inhibition of cAMP/PKA signaling pathway lowered the responsiveness of buffalo GCs to FSH under hypoxic conditions. The present study indicated that hypoxia enhanced the steroidogenic competence of buffalo GCs principal by affecting cAMP/PKA signaling pathway and subsequent sensitivity of GCs to FSH.

Living in a hypoxic world: A review of the impacts of hypoxia on aquaculture.

Hypoxia is a harmful result of anthropogenic climate change. With the expansion of global low-oxygen zones (LOZs), many organisms have faced unprecedented challenges affecting their survival and reproduction. Extensive research has indicated that oxygen limitation has drastic effects on aquatic animals, including on their development, morphology, behavior, reproduction, and physiological metabolism. In this review, the global distribution and formation of LOZs were analyzed, and the impacts of hypoxia on aquatic animals and the molecular responses of aquatic animals to hypoxia were then summarized. The commonalities and specificities of the response to hypoxia in aquatic animals in different LOZs were discussed lastly. In general, this review will deepen the knowledge of the impacts of hypoxia on aquaculture and provide more information and research directions for the development of fishery resource protection strategies.

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.