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PubMed1976

Regulation of cyanide-insensitive respiration in Neurospora.

1. Inhibition of either mitochondrial transcription or translation in Neurospora crassa results in the rapid production of the cyanide-insensitive pathway of mitochondrial respiration. Protein synthesis on cytoplasmic ribosomes is required for the appearance of cyanide-insensitive respiration in the culture. 2. Removal of the inhibition of transcription of translation results in a rapid return to cyanide-sensitive respiration. Additional protein synthesis in the cytoplasm is required for the loss of cyanide-insensitive respiratory activity while additional mitochondrial protein synthesis has no effect. 3. These studies indicate that a mitochondrial gene product is involved in a negative manner in the regulation of cyanide-insensitive respiration. When the mitochondrial product is present, the pathway is not expressed, when the mitochondrial product is absent, the pathway is expressed. 4. Studies with forced heterokaryons formed from respiratory-deficient mutants having cyanide-insensitive respiration and respiratory-competent auxotrophs indicate that the site of action of the mitochondrial gene product is external to the mitochondrion.

Chloramphenicol↗

PubMed2006

Respiration of the external mycelium in the arbuscular mycorrhizal symbiosis shows strong dependence on recent photosynthates and acclimation to temperature.

* Although arbuscular mycorrhizal (AM) fungi are a major pathway in the global carbon cycle, their basic biology and, in particular, their respiratory response to temperature remain obscure. * A pulse label of the stable isotope (13)C was applied to Plantago lanceolata, either uninoculated or inoculated with the AM fungus Glomus mosseae. The extra-radical mycelium (ERM) of the fungus was allowed to grow into a separate hyphal compartment excluding roots. We determined the carbon costs of the ERM and tested for a direct temperature effect on its respiration by measuring total carbon and the (13)C:(12)C ratio of respired CO(2). With a second pulse we tested for acclimation of ERM respiration after 2 wk of soil warming. * Root colonization remained unchanged between the two pulses but warming the hyphal compartment increased ERM length. delta(13)C signals peaked within the first 10 h and were higher in mycorrhizal treatments. The concentration of CO(2) in the gas samples fluctuated diurnally and was highest in the mycorrhizal treatments but was unaffected by temperature. Heating increased ERM respiration only after the first pulse and reduced specific ERM respiration rates after the second pulse; however, both pulses strongly depended on radiation flux. * The results indicate a fast ERM acclimation to temperature, and that light is the key factor controlling carbon allocation to the fungus.

Acclimatization↗

PubMed1982

Maturation of potassium-stimulated respiration in rat cerebral cortical slices.

Maximal dinitrophenol-stimulated respiration and K+-stimulated respiration were measured polarographically in cerebral cortical slices taken from rats aged 2-60 days. Increasing K+ concentrations produced an increase in respiration in slices from animals aged 15 days and older, but not in slices from animals aged 10 days and younger. Dinitrophenol-stimulated respiration, or the maximal respiratory capacity of the tissue, showed a similar increase between 10 and 15 days of age. At each age the maximal respiratory capacity was 6-8 ng at 0/mg protein min greater than the maximal K+-stimulated respiration.

2,4-Dinitrophenol↗

PubMed1994

Immediate and transient inhibition of the respiration of Escherichia coli under hyperosmotic shock.

The respiration of Escherichia coli is severely inhibited, during hyperosmotic stress period, as a consequence of plasmolysis; deplasmolysis allows the cell to recover respiration. A mutant lacking all K+ transport systems can neither deplasmolyze nor recover respiration unless betaine is present in the medium. Betaine, in these conditions, increases both cytoplasmic volume and respiration; this suggests a control of respiration by cytoplasmic volume.

Betaine↗

PubMed1969

The steps between depolarization and the increase in the respiration of frog skeletal muscle.

1. For many years it has been known that when muscles are depolarized by raising [K(+)](out) there is an increase in respiration, even at levels of depolarization below the threshold for a detectable contracture.2. K(+)-stimulated respiration occurs in muscles in which protein synthesis is blocked with puromycin. Stimulation does not depend upon activation of phosphorylase kinase. In muscle poisoned with IIA and kept in N(2), depolarizations below the threshold for contracture cause a fall in creatine phosphate. Apparently an ATPase is activated by depolarization; the resulting ADP is probably the trigger for the increase in oxygen uptake.3. When the T-tubules are destroyed by the glycerol-osmotic shock method depolarization does not produce an increase in respiration.4. Caffeine is known to stimulate respiration at concentrations below the threshold for producing a contracture. Muscles that have been made refractory to stimulation by potassium are still stimulated by caffeine: the action of caffeine is not antagonized by an increase in extracellular Mg(2+). Caffeine must act on a later step in excitation-contraction coupling.5. K(+)-stimulated respiration ultimately depends on the presence of Ca(2+) in the Ringer. However, the Ca(2+) can be replaced by Ni(2+). It is known that Ni(2+) does not activate actomyosin. Ni(2+) is not sequestered by isolated fragments of the sarcoplasmic reticulum. It seems that the Ni(2+) or Ca(2+) in the extracellular solution is required for a superficial step in excitation-contraction coupling.6. Respiration is also often stimulated when muscles are placed in an isotonic sucrose solution, even though the fibres are hyperpolarized. A trace amount of Ca(2+) in the sucrose solution is probably necessary for the response.7. An interaction between Ca(2+) and a superficial membrane receptor appears to be an essential, early step in excitation-contraction coupling.

Adenosine Triphosphatases↗

PubMed2001

Biogenic carbon cycling in the upper ocean: effects of microbial respiration.

Food-web processes are important controls of oceanic biogenic carbon flux and ocean-atmosphere carbon dioxide exchange. Two key controlling parameters are the growth efficiencies of the principal trophic components and the rate of carbon remineralization. We report that bacterial growth efficiency is an inverse function of temperature. This relationship permits bacterial respiration in the euphotic zone to be computed from temperature and bacterial production. Using the temperature-growth efficiency relationship, we show that bacterial respiration generally accounts for most community respiration. This implies that a larger fraction of assimilated carbon is respired at low than at high latitudes, so a greater proportion of production can be exported in polar than in tropical regions. Because bacterial production is also a function of temperature, it should be possible to compute euphotic zone heterotrophic respiration at large scales using remotely sensed information.

Atmosphere↗

PubMed1995

Soil and sediment bacteria capable of aerobic nitrate respiration.

Several laboratory strains of gram-negative bacteria are known to be able to respire nitrate in the presence of oxygen, although the physiological advantage gained from this process is not entirely clear. The contribution that aerobic nitrate respiration makes to the environmental nitrogen cycle has not been studied. As a first step in addressing this question, a strategy which allows for the isolation of organisms capable of reducing nitrate to nitrite following aerobic growth has been developed. Twenty-nine such strains have been isolated from three soils and a freshwater sediment and shown to comprise members of three genera (Pseudomonas, Aeromonas, and Moraxella). All of these strains expressed a nitrate reductase with an active site located in the periplasmic compartment. Twenty-two of the strains showed significant rates of nitrate respiration in the presence of oxygen when assayed with physiological electron donors. Also isolated was one member of the gram-positive genus Arthrobacter, which was likewise able to respire nitrate in the presence of oxygen but appeared to express a different type of nitrate reductase. In the four environments studied, culturable bacteria capable of aerobic nitrate respiration were isolated in significant numbers (10(4) to 10(7) per g of soil or sediment) and in three cases were as abundant as, or more abundant than, culturable bacteria capable of denitrification. Thus, it seems likely that the corespiration of nitrate and oxygen may indeed make a significant contribution to the flux of nitrate to nitrite in the environment.

Aerobiosis↗

PubMed1977

Delayed ultraviolet light-induced cessation of respiration by inadequate aeration of Escherichia coli.

Inadequately aerated Escherichia coli B/r cultures did not shut their respiration off 60 min after ultraviolet light (52 M/m2 at 254 nm) as they did when well supplied with oxygen. Since cessation of respiaration is associated with cell death, the result suggested that oxygen toxicity by superoxide radicals generated by cell metabolism might be responsible for cell death. The specific activity of superoxide dismutase, which scavenges O2- radicals, increased twofold after 90 min of adequate aeration, but the specific activity of catalase remained constant. Respiration and viability of irradiated cells were affected not at all by the presence of superoxide dismutase and only slightly by the presence of catalase. Metal ions such as Mn2+ and Fe2+ inducers of superoxide dismutase, had no effect on respiration and viability. When irradiated cells were incubated under N2 for 90 min, the respiration, growth, and viability time-course responses were the same as for the cells not exposed to anareobiosis. We conclude that superoxide anions generated at the time of irradiation play no part in cessation delays the ultraviolet light-induced synthesis of proteins responsible for the irreversible cessation of respiration.

Anaerobiosis↗

PubMed1978

Cyanide- and hydroxamate-resistant respiration in Neurospora crassa.

Strain inl-89601 of Neurospora crassa respires exclusively by means of the mitochondrial cytochrome chain. The respiration of this strain is entirely inhibited by cyanide or antimycin A, the classical inhibitors of cytochrome chain respiration. When this strain was grown in the presence of chloramphenicol, however, two additional terminal oxidases were detected. One of these oxidases is inhibited by substituted hydroxamic acids and has been described previously. The second oxidase was not inhibited by cyanide or hydroxamic acid but was inhibited by azide in the presence of both cyanide and hydroxamic acid. This azide-sensitive respiration was due to a single respiratory pathway with a Ki for azide of 200 micrometer. A small amount of azide-sensitive respiration was detected in mitochondrial fractions obtained from chloramphenicol-treated cells, and it is likely that the azide-sensitive oxidase is localized in the mitochondrion. The determinants for the azide-sensitive and hydroxamate-sensitive oxidases segregate in a Mendelian manner in crosses and are either unlinked or not closely linked to each other.

Azides↗

PubMed2002

Anaerobic respiration using Fe(3+), S(0), and H(2) in the chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans.

The chemolithoautotrophic bacterium Acidithiobacillus ferrooxidans has been known as an aerobe that respires on iron and sulfur. Here we show that the bacterium could chemolithoautotrophically grow not only on H(2)/O(2) under aerobic conditions but also on H(2)/Fe(3+), H(2)/S(0), or S(0)/Fe(3+) under anaerobic conditions. Anaerobic respiration using Fe(3+) or S(0) as an electron acceptor and H(2) or S(0) as an electron donor serves as a primary energy source of the bacterium. Anaerobic respiration based on reduction of Fe(3+) induced the bacterium to synthesize significant amounts of a c-type cytochrome that was purified as an acid-stable and soluble 28-kDa monomer. The purified cytochrome in the oxidized form was reduced in the presence of the crude extract, and the reduced cytochrome was reoxidized by Fe(3+). Respiration based on reduction of Fe(3+) coupled to oxidation of a c-type cytochrome may be involved in the primary mechanism of energy production in the bacterium on anaerobic iron respiration.

Anaerobiosis↗

PubMed2004

Proteome analyses of heme-dependent respiration in Lactococcus lactis: involvement of the proteolytic system.

Sugar fermentation was long considered the sole means of energy metabolism available to lactic acid bacteria. We recently showed that metabolism of Lactococcus lactis shifts progressively from fermentation to respiration during growth when oxygen and heme are available. To provide insights into this phenomenon, we compared the proteomic profiles of L. lactis under fermentative and respiratory growth conditions in rich medium. We identified 21 proteins whose levels differed significantly between these conditions. Two major groups of proteins were distinguished, one involved in carbon metabolism and the second in nitrogen metabolism. Unexpectedly, enzymes of the proteolytic system (PepO1 and PepC) which are repressed in rich medium in fermentation growth were induced under respiratory conditions despite the availability of free amino acids. A triple mutant (dtpT dtpP oppA) deficient in oligopeptide transport displayed normal respiration, showing that increased proteolytic activity is not an absolute requirement for respiratory metabolism. Transcriptional analysis confirmed that pepO1 is induced under respiration-permissive conditions. This induction was independent of CodY, the major regulator of proteolytic functions in L. lactis. We also observed that pepO1 induction is redox sensitive. In a codY mutant, pepO1 expression was increased twofold in aeration and eightfold in respiration-permissive conditions compared to static conditions. These observations suggest that new regulators activate proteolysis in L. lactis, which help to maintain the energetic needs of L. lactis during respiration.

Bacterial Proteins↗

PubMed1962

Effect of mycosuppressin on the respiration and growth of Mycobacterium tuberculosis.

Youmans, Anne S. (Northwestern University Medical School, Chicago, Ill.) and Guy P. Youmans. Effect of mycosuppressin on the respiration and growth of Mycobacterium tuberculosis. J. Bacteriol. 84:708-715. 1962.-A substance, called mycosuppressin, was found in the lungs of guinea pigs and rabbits vaccinated with BCG or with a particulate immunizing fraction isolated from mycobacterial cells, and was not found in lungs of unvaccinated animals. Mycosuppressin inhibited the endogenous respiration and the growth of the virulent H37Rv strain of Mycobacterium tuberculosis. It also inhibited the endogenous respiration of the avirulent H37Ra strain and the saprophyte, M. smegmatis, but it increased the respiration of M. phlei. The oxidation by the H37Rv strain of lactate, pyruvate, glycerol, and glucose was also inhibited. Cytochrome oxidase activity was suppressed. Mycosuppressin was most stable at pH 6 to 7. It was nondialyzable, stable at 98 C, and not affected by lyophilization or freezing. It was soluble, in alcohol and acetone, insoluble in ether and water. Under appropriate conditions, mycosuppressin combined with, or was adsorbed to, mycobacterial cells, and was inactivated by serum and bovine serum albumin. It did not inhibit but, instead increased markedly, the respiration of Staphylococcus aureus and Escherichia coli.

Animals↗

PubMed1966

Influence of glutamic acid on the endogenous respiration of Bacillus subtilis.

Clifton, C. E. (Stanford University, Stanford, Calif.), and John Cherry. Influence of glutamic acid on the endogenous respiration of Bacillus subtilis. J. Bacteriol. 91:546-550. 1966.-Amino acids serve as the major initial endogenous substrate for Bacillus subtilis. The endogenous activity of freshly harvested washed cells is high and falls off rapidly with time of shaking at 30 C to lower but still significant levels. The rate of O(2) consumption after the addition of glutamic acid also decreases as the cells age, but more slowly than noted for endogenous respiration. When cells were fed glutamate as soon as possible after harvesting, an apparent stimulation of endogenous respiration was noted. However, endogenous activity was inhibited if the cell suspensions were shaken for at least 1 hr before addition of the glutamate. Similar results were obtained with glycerol or glucose as exogenous substrates. Variation in rates of respiration with age of the cells, inherent instability of B. subtilis, and possible utilization of substances initially excreted by the cells appear to account for the variations noted regarding the influence of an exogenous substrate on endogenous respiration.

Ammonia↗

PubMed2006

Specific features of changes in levels of endogenous respiration substrates in Saccharomyces cerevisiae cells at low temperature.

The rate of endogenous respiration of Saccharomyces cerevisiae cells incubated at 0 degrees C under aerobic conditions in the absence of exogenous substrates decreased exponentially with a half-period of about 5 h when measured at 30 degrees C. This was associated with an indirectly shown decrease in the level of oxaloacetate in the mitochondria in situ. The initial concentration of oxaloacetate significantly decreased the activity of succinate dehydrogenase. The rate of cell respiration in the presence of acetate and other exogenous substrates producing acetyl-CoA in mitochondria also decreased, whereas the respiration rate on succinate increased. These changes were accompanied by an at least threefold increase in the L-malate concentration in the cells within 24 h. It is suggested that the increase in the L-malate level in the cells and the concurrent decrease in the oxaloacetate level in the mitochondria should be associated with a deceleration at 0 degrees C of the transport of endogenous respiration substrates from the cytosol into the mitochondria. This deceleration is likely to be caused by a high Arrhenius activation energy specific for transporters. The physiological significance of L-malate in regulation of the S. cerevisiae cell respiration is discussed.

Aerobiosis↗

PubMed1995

Factors affecting total and "respirable" dose delivered by a salbutamol metered dose inhaler.

BACKGROUND: Many factors contribute to the high variability of doses delivered to the lungs of patients using metered dose inhalers (MDIs). Relatively little attention has been paid to the contribution to this variability of the way in which the MDI is handled before the inhalation manoeuvre. Instruction leaflets often recommend procedures at odds with those used for in vitro testing of the device. The standard protocol for in vitro assessment of salbutamol MDIs involves shaking the MDI vigorously for 30 seconds and wasting the first two actuations. Subsequent actuations are introduced into the testing device at five second intervals. Patient instructions do not include a recommendation to waste the first two actuations and recommend a delay of one minute between actuations. A series of experiments was performed to determine whether such differences might be important. METHODS: The total and "respirable" doses delivered by a salbutamol MDI (Ventolin, Allen & Hanburys) under various conditions were assessed with a multistage liquid impinger. The quantity of drug deposited on each stage was measured by an ultraviolet spectrophotometric method. The effect on the delivered dose of not shaking the canister, not wasting the first two doses, waiting 30 seconds between actuations, and using multiple rapid actuations was assessed by comparing the results with those obtained using the standard in vitro testing protocol. RESULTS: Compared with a standard protocol, it was found that not shaking the MDI before use reduced the total and "respirable" dose by 25.5% and 35.7%, respectively. The dose delivered when actuating the MDI at 30 second intervals was no different from that when intervals was no different from that when intervals of five seconds were used. Two actuations separated by one second had no effect on the total dose but reduced the "respirable" dose by 15.8%, while four rapid actuations reduced the total and "respirable" doses by 8.2% and 18.2%, respectively. Storing the MDI stem down reduced the total and "respirable" dose delivered in the first actuation by 25.0% and 23.3% despite shaking the MDI before use. CONCLUSIONS: MDIs containing drug in suspension must be shaken before use to resuspend the drug contained in the MDI, but shaking does not alter the composition of the suspension in the metering chamber and hence the dose in the first actuation remains low. Very rapid actuations can reduce the dose delivered per actuation, but salbutamol MDIs can be actuated immediately after a 10 second breath holding pause without affecting the dose delivered.

Albuterol↗

PubMed1990

Control of mitochondrial respiration in the heart in vivo.

After reviewing the controversies in the literature surrounding the regulation of oxidative phosphorylation, a unifying theory to integrate the disparate results would be welcome. Following the traditional biochemical approach to identifying sites of control, one searches for the rate-limiting step in a series of reactions (i.e. a biochemical pathway) that, presumably, will not be at equilibrium. This approach has not succeeded in locating a reaction in cardiac respiratory control that is singularly rate-limiting and may actually be contributing to, rather than clarifying, the problem. There are two major criticisms of this approach. First, even if the step is in disequilibrium, it does not prove that it is rate-limiting (26). Second, a reaction near equilibrium can contribute to regulation of a system (37). In a complex, multiple-reaction integrated pathway such as mitochondrial respiration there are many steps that could potentially share the control of the overall system. Thus this pathway easily lends itself to the possibility of multiple sites of control, each of which could contribute by varying degrees to regulation. In Figure 3 we present one possible network (undoubtedly incomplete) for the distributed control of respiration, which incorporates contributions by the cellular redox state (supply), phosphate metabolite concentrations (either kinetic or thermodynamic), and oxygen. The coordination of the dehydrogenases, phosphate metabolites, and myosin ATPase activity (work) may be orchestrated by a second messenger. Calcium is an attractive candidate for this role (15) as it simultaneously can modulate reducing equivalent supply via the dehydrogenases and ATP use by the myofibrils. The theory of shared control along the path of respiration is not new (37), and has been gaining support from a variety of laboratories (3, 9, 26). Applying this concept to the experimental setting, the relative control strengths for various steps in oxidative phosphorylation have been reported for isolated mitochondria (26). The control coefficients for respiration in isolated myocytes or hearts in vivo remain unknown at this time. If control of respiration occurs at multiple sites, it could account for much of the disagreement in the literature. Experimental conditions, whether intentional or inadvertent, that saturate one or more control mechanisms will increase the relative effect of the other regulatory sites on the remaining range of mitochondrial function. If, for example, the medium surrounding isolated myocytes is such that the cytosolic redox state and pO2 are very high, the phosphate metabolite concentrations could logically be expected to be a major factor influencing the observed rate of oxidative phosphorylation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1983

Alpha 1-adrenergic stimulation of hamster brown adipocyte respiration.

Respiration was increased approximately 5-fold with 0.05 microM norepinephrine and to a maximum of 10-fold by 0.30 microM norepinephrine. Prazosin, an alpha-adrenergic blocking agent highly selective for alpha 1-type receptors, partially inhibited the response to norepinephrine (0.05 microM) by 20-25% at a concentration of 0.10-1 microM. In contrast, when the stimulus for respiration was provided by isoproterenol or 3-isobutyl-1-methylxanthine, prazosin was without effect up to a concentration of 10 microM. Yohimbine, an alpha-adrenergic blocking drug preferential for alpha 2-receptors, did not influence norepinephrine-stimulated oxygen uptake. Respiration was increased two- to fourfold by phenylephrine or methoxamine, agents preferential for alpha 1-adrenergic receptors but not at all by clonidine, an agent preferential for alpha 2-adrenergic receptors. The stimulatory effect of phenylephrine on oxygen uptake was fully blocked by prazosin but not propranolol. Removal of extracellular calcium with ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid prevented phenylephrine stimulation of respiration but was without effect when isoproterenol was the stimulus. These results support the participation of alpha 1-adrenergic receptors in control of respiration and are consistent with the possibility that changes in cell calcium are intimately involved in this response.

1-Methyl-3-isobutylxanthine↗

PubMed1998

Mitochondrial respiration after sepsis and prolonged hypoxia.

Recently, marked oxygen dependence of respiration by isolated mitochondria after exposure to prolonged hypoxia has been described. Because mitochondrial oxygen-dependent respiration could significantly influence oxygen consumption during critical illness, we sought to confirm the oxygen-dependent behavior of mitochondria. We hypothesized that mitochondria isolated during sepsis would exhibit increased oxygen dependence. We isolated rat liver mitochondria 16 h after cecal ligation and puncture and found a 30-40% greater oxygen uptake compared with control rats under state 3 conditions. Mitochondria incubated in deoxygenated buffer were studied for oxygen dependence at 10-min intervals for 90 min. Mitochondrial respiration after reoxygenation was stable over a 60-min period of hypoxia for control rats and decreased slightly for septic rats (10-15%). State 3 respiration was 10% lower when mitochondria were reoxygenated at low (15-25 Torr) versus high (90-100 Torr) and low (10-15 Torr) versus intermediate (40-45 Torr) oxygen tension. Oxygen consumption with ascorbate+N, N, N', N'-tetramethyl-p-phenylenediamine was 20% lower at low versus high oxygen tension. No increase in oxygen dependence was observed during 1 h of hypoxic incubation. Our data indicate only a modest oxygen dependence of respiration between 10 and 100 Torr, which is similar for septic and control mitochondria. Additionally, oxygen dependence did not increase significantly during a 1-h hypoxic exposure for well-coupled mitochondrial preparations.

Animals↗