Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0003129 (Anoxia)
 551 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Changes in the abundance of sympatric Achromatium spp. in response to the artificial manipulation of redox conditions in sediment microcosms was determined by fluorescence in situ hybridization (FISH). Adaptation to different redox conditions was shown to be one mechanism that supported the coexistence of functionally similar Achromatium spp. In sediment microcosms, in which the overlying water was oxygenated, Achromatium community size and composition remained unchanged over time. However, imposition of anoxic conditions induced changes in community structure. Anoxia caused a reduction in the relative abundance of Achromatium sp. RY8 (72 +/- 4% to 49 +/- 2%) and an increase in Achromatium sp. RY5 (19 +/- 5% to 32 +/- 3%) and a newly identified Achromatium sp., RYKS (14 +/- 4% to 27 +/- 2%). In anoxic microcosms supplemented with a single addition of nitrate at different initial concentrations the relative decline in Achromatium sp. RY8 was dependent on the initial nitrate concentration. In these experiments nitrate was rapidly removed. In contrast, when high levels of nitrate were maintained by periodic replacement of the overlying water with nitrate supplemented anoxic water, the composition of the Achromatium community remained stable over time. This suggested that all of the coexisting Achromatium spp. are obligate or facultative anaerobes, but, Achromatium sp. RY8 was more sensitive to sediment redox conditions than the other Achromatium species. Given the heterogeneous nature of sedimentary environments, redox-related niche differentiation may promote coexistence of sympatric Achromatium spp.
 ...
PMID:Adaptation of sympatric Achromatium spp. to different redox conditions as a mechanism for coexistence of functionally similar sulphur bacteria. 1518 45

Painted turtles (Chrysemys picta) survive months of anoxic submergence, which is associated with large changes in the extracellular milieu where pH falls by 1, while extracellular K+, Ca++, and adrenaline levels all increase massively. While the effect of each of these changes in the extracellular environment on the heart has been previously characterized in isolation, little is known about their interactions and combined effects. Here we examine the isolated and combined effects of hyperkalemia, acidosis, hypercalcemia, high adrenergic stimulation, and anoxia on twitch force during isometric contractions in isolated ventricular strip preparations from turtles. Experiments were performed on turtles that had been previously acclimated to warm (25 degrees C), cold (5 degrees C), or cold anoxia (submerged in anoxic water at 5 degrees C). The differences between acclimation groups suggest that cold acclimation, but not anoxic acclimation per se, results in a downregulation of processes in the excitation-contraction coupling. Hyperkalemia (10 mmol L(-1) K+) exerted a strong negative inotropic effect and caused irregular contractions; the effect was most pronounced at low temperature (57%-97% reductions in twitch force). Anoxia reduced twitch force at both temperatures (14%-38%), while acidosis reduced force only at 5 degrees C (15%-50%). Adrenergic stimulation (10 micromol L(-1)) increased twitch force by 5%-19%, but increasing extracellular [Ca++] from 2 to 6 mmol L(-1) had only small effects. When all treatments were combined with anoxia, twitch force was higher at 5 degrees C than at 25 degrees C, whereas in normoxia twitch force was higher at 25 degrees C. We propose that hyperkalemia may account for a large part of the depressed cardiac contractility during long-term anoxic submergence.
 ...
PMID:Extracellular determinants of cardiac contractility in the cold anoxic turtle. 1622 37

Changes in oxygen levels occur frequently in aquatic environments; therefore, water organisms, including fishes, evolve a wide spectrum of adaptations to both anoxia/hypoxia and hyperoxia. The review describes oxidative damage to cellular constituents by reactive oxygen species, alterations in glutathione status, and response of antioxidant enzymes to variable oxygen availability in fish. Anoxia- and hypoxia-tolerant species demonstrate an anticipatory increase of some antioxidant enzymes during low-oxygen state in order to enhance their antioxidant potential for dealing with possible oxidative stress upon return to normoxia. Under hyperoxic conditions, it seems that the glutathione system plays an important adaptive role. Most stressful conditions lead to a quick increase in lipid peroxidation products that, in turn, are detoxified rapidly by respective low- and high-molecular weight antioxidants. A scheme on possible ways of regulating antioxidant enzymes by different oxygen levels is proposed.
 ...
PMID:Effects of different environmental oxygen levels on free radical processes in fish. 1675 Sep 25

Freshwater turtles of the Trachemys and Chrysemys genera are champion facultative anaerobes able to survive for several months without oxygen during winter hibernation in cold water. They have been widely used as models to identify and understand the molecular mechanisms of natural anoxia tolerance and the molecular basis of the hypoxic/ischemic injuries that occur in oxygen-sensitive systems and underlie medical problems such as heart attack and stroke. Peter L. Lutz spent much of his career investigating turtle anaerobiosis with a particular focus on the mechanisms of brain ion homeostasis and neurotransmitter responses to anoxia exposure and the mechanisms that suppress brain ion channel function and neuronal excitability during anaerobiosis. Our interests intersected over the mechanisms of metabolic rate depression which is key to long term anoxia survival. Studies in my lab have shown that a key mechanism of metabolic arrest is reversible protein phosphorylation which provides coordinated suppression of the rates of multiple ATP-producing, ATP-utilizing and related cellular processes to allow organisms to enter a stable hypometabolic state. Anoxia tolerance is also supported by selective gene expression as revealed by recent studies using cDNA library and DNA array screening. New studies with both adult T. scripta elegans and hatchling C. picta marginata have identified prominent groups of genes that are up-regulated under anoxia in turtle organs, in several cases suggesting aspects of cell function and metabolic regulation that have not previously been associated with anaerobiosis. These groups of anoxia-responsive genes include mitochondrially-encoded subunits of electron transport chain proteins, iron storage proteins, antioxidant enzymes, serine protease inhibitors, transmembrane solute carriers, neurotransmitter receptors and transporters, and shock proteins.
 ...
PMID:Anoxia tolerance in turtles: metabolic regulation and gene expression. 1703 57

Anoxia and hypoxia have been widely observed in estuarine and coastal regions over the past few decades; however, few reports have focused on the East China Sea (ECS). In June and August 2003, two cruises sampled at stations covering almost the entire shelf of the ECS to examine hypoxic events and their potential causes. In August, DO concentrations <2-3 mg l(-1) covered an area estimated at greater than 12,000 km(2) (or 432 km(3) volume). In contrast, water column DO concentrations exceeded 4 mg l(-1) throughout most of the shelf region. A sharp density gradient was observed under the mixed layer in August, restricting vertical re-aeration across this strong pycnocline. Oxygen depletion events, such as that described here for the ECS shelf, are fueled by decomposition of newly produced marine and river-borne biogenic substances (as well as older residual organic matter) deposited to the bottom waters.
 ...
PMID:Hypoxia in the East China Sea: one of the largest coastal low-oxygen areas in the world. 1744 32

Anoxia occurs annually in deeper waters of the central portion of the Chesapeake Bay and presently extends from Baltimore to the mouth of the Potomac estuary. This condition, which encompasses some 5 billion cubic meters of water and lasts from May to September, is the result of increased stratification of the water column in early spring, with consequent curtailment of reoxygenation of the bottom waters across the halocline, and benthic decay of organic detritus accumulated from plankton blooms of the previous summer and fall. The Chesapeake Bay anoxia appears to have had significant ecological effects on many marine species, including several of economic importance.
 ...
PMID:Chesapeake bay anoxia: origin, development, and significance. 1775 72

Anoxia occurs in bottom waters of stratified estuaries when respiratory consumption of oxygen, primarily by bacteria, outpaces atmospheric and photosynthetic reoxygenation. Once water becomes anoxic, bacterioplankton must change their metabolism to some form of anaerobic respiration. Analysis of redox chemistry in water samples spanning the oxycline of Chesapeake Bay during the summer of 2004 suggested that there was a succession of respiratory metabolism following the loss of oxygen. Bacterial community doubling time, calculated from bacterial abundance (direct counts) and production (anaerobic leucine incorporation), ranged from 0.36 to 0.75 day and was always much shorter than estimates of the time that the bottom water was anoxic (18 to 44 days), indicating that there was adequate time for bacterial community composition to shift in response to changing redox conditions. However, community composition (as determined by PCR-denaturing gradient gel electrophoresis analysis of 16S rRNA genes) in anoxic waters was very similar to that in surface waters in June when nitrate respiration was apparent in the water column and only partially shifted away from the composition of the surface community after nitrate was depleted. Anoxic water communities did not change dramatically until August, when sulfate respiration appeared to dominate. Surface water populations that remained dominant in anoxic waters were Synechococcus sp., Gammaproteobacteria in the SAR86 clade, and Alphaproteobacteria relatives of Pelagibacter ubique, including a putative estuarine-specific Pelagibacter cluster. Populations that developed in anoxic water were most similar (<92% similarity) to uncultivated Firmicutes, uncultivated Bacteroidetes, Gammaproteobacteria in the genus Thioalcalovibrio, and the uncultivated SAR406 cluster. These results indicate that typical estuarine bacterioplankton switch to anaerobic metabolism under anoxic conditions but are ultimately replaced by different organisms under sulfidic conditions.
 ...
PMID:Respiratory succession and community succession of bacterioplankton in seasonally anoxic estuarine waters. 1776 41

The deleterious effects of anoxia followed by reperfusion with oxygen in higher animals including mammals are well known. A convenient and genetically well characterized small-animal model that exhibits reproducible, quantifiable oxygen reperfusion damage is currently lacking. Here we describe the dynamics of whole-organism metabolic recovery from anoxia in an insect, Drosophila melanogaster, and report that damage caused by oxygen reperfusion can be quantified in a novel but straightforward way. We monitored CO(2) emission (an index of mitochondrial activity) and water vapor output (an index of neuromuscular control of the spiracles, which are valves between the outside air and the insect's tracheal system) during entry into, and recovery from, rapid-onset anoxia exposure with durations ranging from 7.5 to 120 minutes. Anoxia caused a brief peak of CO(2) output followed by knock-out. Mitochondrial respiration ceased and the spiracle constrictor muscles relaxed, but then re-contracted, presumably powered by anaerobic processes. Reperfusion to sustained normoxia caused a bimodal re-activation of mitochondrial respiration, and in the case of the spiracle constrictor muscles, slow inactivation followed by re-activation. After long anoxia durations, both the bimodality of mitochondrial reactivation and the recovery of spiracular control were impaired. Repeated reperfusion followed by episodes of anoxia depressed mitochondrial respiratory flux rates and damaged the integrity of the spiracular control system in a dose-dependent fashion. This is the first time that physiological evidence of oxygen reperfusion damage has been described in an insect or any invertebrate. We suggest that some of the traditional approaches of insect respiratory biology, such as quantifying respiratory water loss, may facilitate using D. melanogaster as a convenient, well-characterized experimental model for studying the underlying biology and mechanisms of ischemia and reperfusion damage and its possible mitigation.
 ...
PMID:Oxygen reperfusion damage in an insect. 1806 61

Some plant species can increase the mass flow of water from the soil to the root surface in response to the appearance of nitrate in the rhizosphere by increasing root hydraulic conductivity. Such behavior can be seen as a powerful strategy to facilitate the uptake of nitrate in the patchy and dynamically changing soil environment. Despite the significance of such behavior, little is known about the dynamics and mechanism of this phenomenon. Here we examine root hydraulic response of nitrate starved Zea mays (L.) plants after a sudden exposure to 5 mM NO(3)(-) solution. In all cases the treatment resulted in a significant increase in pressure-induced (pressure gradient approximately 0.2 MPa) flow across the root system by approximately 50% within 4 h. Changes in osmotic gradient across the root were approximately 0.016 MPa (or 8.5%) and thus the results could only be explained by a true change in root hydraulic conductance. Anoxia treatment significantly reduced the effect of nitrate on xylem root hydraulic conductivity indicating an important role for aquaporins in this process. Despite a 1 h delay in the hydraulic response to nitrate treatment, we did not detect any change in the expression of six ZmPIP1 and seven ZmPIP2 genes, strongly suggesting that NO(3)(-) ions regulate root hydraulics at the protein level. Treatments with sodium tungstate (nitrate reductase inhibitor) aimed at resolving the information pathway regulating root hydraulic properties resulted in unexpected findings. Although this treatment blocked nitrate reductase activity and eliminated the nitrate-induced hydraulic response, it also produced changes in gene expression and nitrate uptake levels, precluding us from suggesting that nitrate acts on root hydraulic properties via the products of nitrate reductase.
 ...
PMID:Nitrate induction of root hydraulic conductivity in maize is not correlated with aquaporin expression. 1867 12

Attempts have been made in dogs to lower the serum chlorides by means of various procedures. Of these the withholding of food, anoxemia, tissue destruction, anaphylactic shock, leucocytosis, and fever yielded negative results. Ingestion of large amounts of water lowered the chloride level independently of body temperature. The chloride drop under these circumstances could not be accounted for by excretion and appeared to run parallel with an increase in the serum water content. Experimental pneumococcus infection in two animals reduced the serum chloride concentration.
 ...
PMID:BLOOD CHLORIDES IN CONDITIONS ASSOCIATED WITH PNEUMONIA. 1986 67


<< Previous 1 2 3 4 5 Next >>