共查询到20条相似文献,搜索用时 15 毫秒
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Synopsis The partitioning of O2 uptake between aquatic and aerial gas exchange and its dependence on ambient water PO2 was studied in the facultative air breathing teleost Synbranchus marmoratus, after acclimation to well aerated water and after acute and chronic exposure to hypoxic water. O2 uptake was also studied following acute air exposure and after prolonged entrapment in soil. Breathing rates during water and air breathing in response to reduced water PO2 and tidal volume during air breathing were also studied.
S. marmoratus satisfies its O2 requirement by water breathing alone until water PO2 falls below 30–50 mm Hg (switching PO2) depending on the acclimation history. Below the switching PO2, air breathing is adopted while active water breathing stops. The O2 uptake varied little for all groups when the principal mode of gas exchange changed at the switching PO2. The highest O2 uptake prevailed when the fish employed the mode of gas exchange in operation during the acclimation period (i.e. water breathing for normoxia-acclimated, air breathing for hypoxic-acclimated).Acclimation to chronic hypoxia gave a much higher switching PO2 55 mm Hg) than for the other groups (about 30 mm Hg).
S. marmoratus maintained its O2 uptake when acutely exposed to air. When entrapped in soil in an aestivating state, the O2 uptake was reduced to 25% of that in water or during acute air exposure. The overall gas exchange ratio for air breathing was very low (RE 0.1).Branchial water pumping increased with lowering of water PO2. The rate of air breathing was independent of water PO2.The findings are discussed in the light of the ecophysiological conditions confronting S. marmoratus. 相似文献
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Characterization and application of an optical sensor for quantification of dissolved O2 in shake-flasks 总被引:3,自引:0,他引:3
On-line measurement of dissolved O2 in shake-flasks was realized via immobilized sensor spots containing a fluorophore with an O2-dependent luminescent decay time. An unaffected sensor signal during 80 autoclaving cycles suggests multi-usage of sensor equipped shake-flasks. The sensor had a response time of 6 s. Quantification of gas-liquid mass transfer revealed maximum kLa values of 150 h–1, from which maximum O2 transfer capacity of 33 mM h–1 was calculated. Liquid volume and shaking frequency have a strong influence on kLa. Exemplified by cultivations of Corynebacterium glutamicum the importance of shaking rate for O2 supply of bacterial cultures is shown. Sampling of microbial cultures with intermittent shaking of a few minutes can cause O2 limitation. Based on the results of this work a simple and straightforward tool is now available for accurate O2 sensing in shake-flasks, which are widely used in microbial cultivations. 相似文献
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Theoretical calculations have been performed on the effects of changes in intrauterine pressure on maternal and fetal placental blood flows and pressures and transplacental O2 exchange. Initial conditions and contraction profiles may be “assumed normal” or abnormal. The model predicts that the fetal O2 deficit is most sensitive to the maximum intensity of the contraction and maternal mean arterial blood pressure, less sensitive to the duration of the contraction and far less sensitive to the value of maternal arterial PO2. The umbilical venous PO2 falls to a minimum at the peak of a contraction. Its level is most sensitive to contraction intensity and maternal blood pressure; while the value of maternal arterial PO2 has less effect and the duration of contraction has essentially no effect. There is interaction between factors so that the effect of simultaneous changes is not necessarily in proportion to the effects of individual changes. 相似文献
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Catecholamine (CAT) release from chromaffin tissue plays an essential role in the fetus which develops in a low O2 environment (hypoxia). To address molecular mechanisms regulating CAT secretion in low O2, we exposed a fetal chromaffin-derived cell line (MAH cells) to chronic hypoxia (CHox; 2% O2, 24 h) and assessed gene expression using microarrays, quantitative RT-PCR, and western blot. CHox caused a dramatic ∼12× upregulation of adenosine A2a receptor (A2aR) mRNA, an effect critically dependent upon hypoxia-inducible factor (HIF)-2α which bound the promoter of the A2aR gene. In amperometric studies, acute hypoxia and high K+ (30 mM) evoked quantal CAT secretion that was enhanced after CHox, and further potentiated during simultaneous A2aR activation by adenosine. A2aR activation also enhanced stimulus-induced rise in intracellular Ca2+ in control, but not HIF-2α-deficient, MAH cells. Thus, A2aR, adenosine, and HIF-2α are key contributors to the potentiation of CAT secretion in developing chromaffin cells during chronic hypoxia. 相似文献
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《Free radical research》2013,47(2):73-82
Recent investigations have indicated the presence of a fatty acid binding protein (FABP) in mammalian heart. This protein binds free fatty acids and their esters with high affinity, however, its physiological role remains unknown. Since FABP constitutes a significant amount of cystolic protein, it is likely that it would be a target for free radical attack. To test this hypothesis, FABP was examined for scavenging against free radicals such as the superoxide anion (O?2,). hydroxyl radical (OH') and hypochlorite radical (OCl') which may be present in an ischemic reperfused heart. Our results suggest that FABP scavenges O?2, OH' and OCl' as indicated by the FABP inhibition of O?2-dependent reduction of cytochrome c, OH'-dependent hydroxybenzoic acid formation and OCl'-mediated chemiluminescence response. FABP was found to be a more potent scavenger of these free radicals compared to bovine serum albumin. Furthermore, FABP was more effective in scavenging OH' than O?2, and inhibited OH' mediated lipid peroxidation process. These results indicate that FABP can scavenge free radicals which may be present in an ischemic/reperfused heart and, thus, may play a significant physiological role in the heart during ischemia and reperfusion. 相似文献
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Synopsis Oxygen uptake (VO2) during graded hypoxia, rate of hypoxia acclimation, breathing frequency (fR), breath volume (VS, R) and gill ventilation (VG) were measured in Hoplias malabaricus. Normoxia and hypoxia acclimated fish had similar and constant VO2 and VG in a range of water PO2 from 150 to 25 mmHg. Hypoxia acclimated fish showed significantly higher VO2 in severe hypoxia (PO2 <15 mmHg). Normoxia acclimated fish showed symptoms similar to hypoxic coma after 1 h of exposure to water PO2 of 10 mmHg whereas the same symptoms were observed only at PO2 of 5 mmHg for fish acclimated to hypoxia. Fish required 14 days to achieve full acclimation to hypoxia (PO2 ≥25 mmHg). Lowering of water PO2 from 150 to 25 mmHg resulted in normoxic fish showing a 3–2 fold increase in VG. The increase was the result of an elevation in VS, R rather than fR. Among normoxia acclimated specimens, small fish showed a higher VG per unit weight than the large ones in both normoxia (PO2 =150 mmHg) and hypoxia (PO2 = 15 mmHg). A decrease in the ventilatory requirement (VG/VO2) with increased body weight was recorded in hypoxia (PO2 = 15 mmHg). 相似文献
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Otto S. Wolfbeis 《BioEssays : news and reviews in molecular, cellular and developmental biology》2015,37(8):921-928
Luminescence‐based sensing schemes for oxygen have experienced a fast growth and are in the process of replacing the Clark electrode in many fields. Unlike electrodes, sensing is not limited to point measurements via fiber optic microsensors, but includes additional features such as planar sensing, imaging, and intracellular assays using nanosized sensor particles. In this essay, I review and discuss the essentials of (i) common solid‐state sensor approaches based on the use of luminescent indicator dyes and host polymers; (ii) fiber optic and planar sensing schemes; (iii) nanoparticle‐based intracellular sensing; and (iv) common spectroscopies. Optical sensors are also capable of multiple simultaneous sensing (such as O2 and temperature). Sensors for O2 are produced nowadays in large quantities in industry. Fields of application include sensing of O2 in plant and animal physiology, in clinical chemistry, in marine sciences, in the chemical industry and in process biotechnology. 相似文献
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We show the application of a novel optical on-line sensor fixed in spinner flasks for the online monitoring of dissolved O2 concentrations during mammalian cell growth. Using this sensor that requires only minute changes to the flask to be made,
we could determine the volumetric O2 transfer coefficient as well as O2 consumption rates. Under normal growth conditions the cells did not undergo O2 limitation. Also, the transfer of O2 from the atmosphere to the spinner flasks is influenced by the use of screw caps. The on-line measurement was further applied
to determine the O2 uptake rates which can then be used to monitor the metabolic state of the cells and also for online process monitoring. 相似文献
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Oxygen (O2) homeostasis is essential to the metazoan life. O2‐sensing or hypoxia‐regulated molecular pathways are intimately involved in a wide range of critical cellular functions and cell survival from embryogenesis to adulthood. In this report, we have designed an innovative hypoxia sensor (O2CreER) based on the O2‐dependent degradation domain of the hypoxia‐inducible factor‐1α and Cre recombinase. We have further generated a hypoxia‐sensing mouse model, R26‐O2CreER, by targeted insertion of the O2CreER‐coding cassette in the ROSA26 locus. Using the ROSAmTmG mouse strain as a reporter, we have found that this novel hypoxia‐sensing mouse model can specifically identify hypoxic cells under the pathological condition of hind‐limb ischemia in adult mice. This model can also label embryonic cells including vibrissal follicle cells in E13.5–E15.5 embryos. This novel mouse model offers a valuable genetic tool for the study of hypoxia and O2 sensing in mammalian systems under both physiological and pathological conditions. 相似文献
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A fascinating link between sterols and molecular oxygen (O2) has been a common thread running through the fundamental work of Konrad Bloch, who elucidated the biosynthetic pathway for cholesterol, to recent work supporting a role of sterols in the sensing of O2. Synthesis of sterols by eukaryotes is an O2-intensive process. In this review, we argue that increased levels of O2 in the atmosphere not only made the evolution of sterols possible, but that these sterols may in turn have provided the eukaryote with an early defence mechanism against O2. The idea that nature crafted sterols as a feedback loop to adapt to, or help protect against, the hazards of O2 is novel and enticing. We marshal several lines of evidence to support this thesis: (1) coincidence of atmospheric O2 and sterol evolution; (2) sterols regulate O2 entry into eukaryotic cells and organelles; (3) sterols act as O2 sensors across eukaryotic life; (4) sterols serve as a primitive cellular defence against O2 (including reactive oxygen species). Therefore, sterols may have evolved in eukaryotes partially as an adaptive response to the rise of terrestrial O2, rather than merely as a consequence of it. 相似文献
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Tara L. Lysechko Samuel M. S. Cheung Hanne L. Ostergaard 《The Journal of biological chemistry》2010,285(41):31174-31184
Pyk2 was identified as a Ca2+-dependent kinase, however, the regulation of Pyk2 by Ca2+ in T cells remains controversial. We found that Ca2+ mobilization preferentially induced Pyk2 phosphorylation in cytotoxic T lymphocytes (CTL). Furthermore, Pyk2 phosphorylation in CTL was not absolutely Ca2+ dependent but relied on the strength of T cell receptor stimulation. Ionomycin-stimulated Pyk2 phosphorylation did not require calmodulin activity, because phosphorylation was not inhibited by the calmodulin inhibitor W7, and we detected no Ca2+-regulated association between Pyk2 and calmodulin. Ca2+-stimulated Pyk2 phosphorylation was dependent on Src-family kinase activity, even at the Pyk2 autophosphorylation site. We sought to identify a Ca2+-regulated pathway that could trigger Pyk2 phosphorylation in T cells and found that ionomycin stimulated the production of reactive oxygen species and an H2O2 scavenger inhibited ionomycin-induced Pyk2 phosphorylation. Additionally, H2O2 induced strong Erk activation and ionomycin-stimulated Pyk2 phosphorylation was Erk dependent. These data support the conclusion that Ca2+ mobilization induces the production of reactive oxygen species, which in turn activate the Erk pathway, leading to Src-family kinase-dependent Pyk2 phosphorylation. Our data demonstrate that Pyk2 is not a Ca2+-dependent kinase in T cells but instead, increased intracellular Ca2+ induces Pyk2 phosphorylation through production of reactive oxygen species. These findings are consistent with the possibility that Pyk2 acts as an early sensor of numerous extracellular signals that trigger a Ca2+ flux and/or reactive oxygen species to amplify tyrosine phosphorylation signaling events. 相似文献
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The dynamics of nitric oxide (NO) and peroxynitrite concentration changes during brain ischemia/reperfusion are poorly understood.
In this paper, a NO-selective sensor was used to measure NO concentration changes in the rat brain hippocampus during global
brain ischemia/reperfusion. Four-vessel occlusion model of transient global brain ischemia was used. Global cerebral ischemia
was induced by occluding both common carotid arteries with artery nips (for 20 min) and reperfusion was induced by loosening
the artery nips. Results showed that the changes of NO concentration during global brain ischemia/reperfusion could be divided
into different stages. Together with the effects of O2 tension changes and NO synthase (NOS) on nitric oxide levels, we determined five stages in the NO concentration profile:
(1) acute O2-limited decrease stage; (2) O2-limited steady stage; (3) neuronal NOS activation stage; (4) acute O2-recovery elevation stage; and (5) O2-recovery steady stage. In addition, a chemical reaction network model was constructed to simulate the dynamics of peroxynitrite
during the reperfusion stage, and the effects of a change in the NO formation rate on the dynamics of peroxynitrite were investigated
specifically. Results show the rate of NO formation has a great influence on peroxynitrite dynamics. 相似文献
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To evaluate the efficiency of oxygen (O2) uptake from water through the fish gill lamellar system, a cost function (CF) representing mechanical power expenditure for water ventilation and blood circulation through the gill was formulated, by applying steady-state fluid mechanics to a homogeneous lamellar-channel model. This approach allowed us to express CF as the function of inter-lamellar water channel width (w) and to derive an analytical solution of the width (wmin) at the minimum CF. Morphometric and physiological data for rainbow trout in the literature were referred to calculate CF(w) curves and their wmin values at five intensity stages of swimming exercise. Obtained wmin values were evenly distributed around the standard measure of the width (ws = 24 μm) in this fish. Individual levels of CF(wmin) were also fairly close to the corresponding CF(ws) values within a 10% deviation, suggesting the reliability of approximating [CF(wmin) = CF(ws)]. The cost-performance of O2 uptake through the gill (ηg) was then assessed from reported data of total O2 uptake/CF(ws) at each intensity stage. The ηg levels at any swimming stage exceeded 95% of the theoretical maximum value, implying that O2 uptake is nearly optimally performed in the lamellar-channel system at all swimming speeds. Further analyses of O2 transport in this fresh water fish revealed that the water ventilation by the buccal/opercular pumping evokes a critical limit of swimming velocity, due to confined O2 supply to the peripheral skeletal muscles, which is avoided in ram ventilators such as tuna. 相似文献
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Bo Li Yuejin Zhang Juefu Liu Xin Xie Dan Zou Minqiang Li Jinhuai Liu 《Luminescence》2014,29(4):332-337
Au/La2O3 nanomaterials were prepared through calcining Au‐modified La(OH)3 precursors. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X‐ray diffractometry (XRD) were employed to characterize the as‐prepared samples. Benzene, a common volatile organic compound, was selected as a model to investigate the cataluminescence (CTL)‐sensing properties of the Au/La2O3 nanomaterials. Results indicated that the as‐prepared Au/La2O3 exhibited outstanding CTL properties such as stable intensity, high signal‐to‐noise values, and short response and recovery times. Under optimized conditions, the benzene assay exhibited a broad linear range of 1–4000 ppm, with a limit of detection of 0.7 ppm, which was below the standard permitted concentrations. Furthermore, the gas sensor system showed outstanding selectivity for benzene compared with seven other types of common volatile organic compounds (VOCs). The proposed gas sensor showed good characteristics with high selectivity, fast response time and long lifetime, which suggested the promising application of the Au/La2O3 nanomaterials as a novel highly efficient CTL‐sensing material. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Yuu Yoshida Haruto Ishikawa Shigetoshi Aono Yasuhisa Mizutani 《Biochimica et Biophysica Acta - Proteins and Proteomics》2012,1824(7):866-872
HemAT from Bacillus subtilis (HemAT-Bs) is a heme-containing O2 sensor protein that acts as a chemotactic signal transducer. Binding of O2 to the heme in the sensor domain of HemAT-Bs induces a conformational change in the protein matrix, and this is transmitted to a signaling domain. To characterize the specific mechanism of O2-dependent conformational changes in HemAT-Bs, we investigated time-resolved resonance Raman spectra of the truncated sensor domain and the full-length HemAT-Bs upon O2 and CO dissociation. A comparison between the O2 and CO complexes provides insights on O2/CO discrimination in HemAT-Bs. While no spectral changes upon CO dissociation were observed in our experimental time window between 10 ns and 100 μs, the band position of the stretching mode between the heme iron and the proximal histidine, ν(Fe–His), for the O2-dissociated HemAT-Bs was lower than that for the deoxy form on time-resolved resonance Raman spectra. This spectral change specific to O2 dissociation would be associated with the O2/CO discrimination in HemAT-Bs. We also compared the results obtained for the truncated sensor domain and the full-length HemAT-Bs, which showed that the structural dynamics related to O2 dissociation for the full-length HemAT-Bs are faster than those for the sensor domain HemAT-Bs. This indicates that the heme proximal structural dynamics upon O2 dissociation are coupled with signal transduction in HemAT-Bs. 相似文献