Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “RESPIRATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,657 records · Page 92Linked to original sources
PubMed1969

Control of respiration and metabolism in growing Klebsiella aerogenes. The role of adenine nucleotides.

1. A rapid-sampling technique was used to obtain perchloric acid extracts of cells growing in a chemostat culture, so that meaningful values for ATP content could be obtained in spite of the fact that the turnover time for the total ATP content was about 1sec. 2. For steady-state growth, it was found that, in a glucose-limited chemostat culture, the ATP/ADP concentration ratio was approximately constant with changes in dissolved-oxygen tensions above the critical value, but fell when the culture was grown under oxygen-limited conditions and was at a minimum in anaerobically grown cultures. The steady-state ATP content was lower in cells growing under nitrogen-limited conditions with glucose in excess than in glucose-limited cells. The steady-state ATP content was independent of growth rate at growth rates over 0.1hr.(-1). 3. When the respiration rate of the cells was stimulated by lowering the oxygen tension the ATP content did not increase, indicating either an increased turnover rate of ATP or a fall in the P/O ratio. The sudden addition of extra glucose or succinate to a glucose-limited culture increased the respiration rate of the cells, but the ATP content quickly returned to the steady-state value after initial perturbations. This control over ATP content is explained in terms of regulation by adenine nucleotides of the catabolism and anabolism of glucose. An exception to this control over ATP content was found when the respiration rate was stimulated by addition of an antifoam.

Adenine Nucleotides↗
PubMed1982

Respiration of the rumen ciliate Dasytricha ruminantium Schuberg.

The endogenous respiration of the rumen ciliate Dasytricha ruminantium maintained under an O2 tension of 2kPa (approximately 0.02 atm) was partially inhibited by KCN (40% inhibition) and NaN3 (58% inhibition). The organisms lack cytochromes, and sensitivity of respiration to KCN, NaN3, chloroquine and quercetin suggest that the operation of flavoprotein-iron-sulphur-mediated electron transport. As in Tritrichomonas foetus, hydrogenosomal respiration can be stimulated by the addition of CoA in the presence of 0.025% Triton X-100; stimulation by ADP was not detected. Stimulation of pyruvate-supported O2 uptake by Pi suggests that acetate is produced via acetyl phosphate.

Acetate Kinase↗
PubMed1987

Stimulation of the respiration rate of rat liver mitochondria by sub-micromolar concentrations of extramitochondrial Ca2+.

1. The respiration rate of rat liver mitochondria was stimulated by up to 70% when the extramitochondrial Ca2+ concentration was raised from 103 to 820 nM. This occurred when pyruvate, 2-oxoglutarate, or threo-(Ds)-isocitrate was employed as substrate, but not when succinate was used. 2. Ruthenium Red prevented the stimulation of mitochondrial respiration by extramitochondrial Ca2+, showing that the effect required Ca2+ uptake into the mitochondrial matrix. 3. Starvation of rats for 48 h abolished the stimulation of mitochondrial respiration by extramitochondrial Ca2+ when pyruvate was used as substrate, but did not affect the stimulation of 2-oxoglutarate oxidation by extramitochondrial Ca2+. 4. Our findings are in accord with proposals that oxidative metabolism in liver mitochondria may be stimulated by Ca2+ activation of intramitochondrial dehydrogenases.

Animals↗
PubMed1995

Aberrant mitochondrial respiration in the livers of rats infected with Fasciola hepatica: the role of elevated non-esterified fatty acids and altered phospholipid composition.

The non-esterified fatty acid (NEFA) content and phospholipid composition of mitochondria isolated from the livers of Wistar rats infected with Fasciola hepatica were examined in relation to the aberrant mitochondrial respiration previously reported [Rule, Behm, and Bygrave (1989) Biochem. J. 260, 517-523]. At 2 weeks post-infection, elevated NEFA levels were associated with uncoupling of mitochondrial respiration that was reversible in vitro by the addition of BSA. State IV respiration rates showed a strong correlation with NEFA content. At 3 weeks post-infection, NEFA content had increased further and uncoupled mitochondria no longer showed any response to BSA. 31P-NMR analyses of cholate extracts of mitochondria from infected livers at 3 weeks post-infection revealed a marked loss of several major phospholipid species with a concomitant increase in catabolic products, particularly glycerophosphocholine and glycerophosphoethanolamine. Similar changes were observed in microsomal extracts. The NEFA content and phospholipid composition of mitochondria isolated from infected, athymic nude rats were not significantly different from uninfected, athymic rats. These findings suggest that uncoupling of liver mitochondria during infection with F. hepatica is the result of phospholipase activation mediated by the immune system of the host.

Animals↗
PubMed2002

Fluoride and organic weak acids as respiration inhibitors for oral streptococci in acidified environments.

Oxygen metabolism (respiration) of Streptococcus mutans GS-5 involving NADH oxidases, mainly of the H(2)O-producing type, was found to be acid sensitive, as was NADH oxidase activity of cell extracts. Respiration of intact cells in acidified media was also highly sensitive to fluoride, with a 50% inhibitory concentration of about 0.02 mM at pH 4. In contrast, NADH oxidases in cell extracts were fluoride insensitive. Fluoride inhibition of respiration of intact cells was related to weak-acid effects leading to enhanced proton permeability of cells, cytoplasmic acidification and resultant acid inhibition of NADH oxidases and glycolysis. Organic weak acids, such as indomethacin and benzoate, were also effective inhibitors. H(2)O(2) production by intact cells of Streptococcus sanguis NCTC 10904, a peroxide producer, was similarly inhibited by fluoride or organic weak acids in acidified media. Thus, weak acids act as respiratory inhibitors for oral streptococci indirectly by acidifying the cytoplasm rather than acting as direct inhibitors of NADH oxidases.

Acids↗
PubMed1999

Comparison of resting energy expenditure measurements by ventilated canopy and by respiration chamber.

The study compared measurements of resting energy expenditure (REE) by two methods, namely the commercially available ventilated canopy (Medgraphics CCM system) and the respiration chamber. Thirty-five healthy subjects of both sexes with a wide weight range (BMI 18-33.8 kg m-2) were measured on both systems. The linear regression equation was REEcanopy = 0.66 x REEresp.cham. + 61.1 (kJ h-1), and the corresponding SEE% was 8.6%. The correlation was high (r = 0.89). However, the mean REE measured using the ventilated canopy was 41 kJ h-1 (13%) lower than that using the respiration chamber (P < 0.01). The Medgraphics CCM canopy system seems valid for measurements of REE. However, the REE results measured by the canopy were systematically lower than when measured by the respiration chamber, but can be converted by the equation given with an accuracy error of 9%.

Adult↗
PubMed1998

Changes in the proton potential and the cellular energetics of Escherichia coli during growth by aerobic and anaerobic respiration or by fermentation.

The energetic parameters of Escherichia coli were analyzed for the aerobic/anaerobic transition. The electrochemical proton potential (delta p) across the cytoplasmic membrane was determined in the steady state of respiration with O2, nitrate, fumarate, dimethylsulfoxide (Me2SO), and for fermentation. With O2, a proton potential of -160 mV was obtained. For anaerobic respiration with nitrate, fumarate or Me2SO, delta p decreased only slightly by about 20 mV in contrast to earlier assumptions, whereas delta p dropped by approximately 40 mV during fermentation. Under all conditions, the membrane potential (delta psi) contributed the major portion to delta p. The cellular ATP levels were highest for aerobic growth (about 13 micromol/g dry cells) and decreased to 3-6 micromol/g in anaerobic metabolism. Delta G'Phos, however, was constant due to equivalent changes of the ADP contents. Transition to the stationary growth phase caused a massive drop in the ATP content. It is concluded that, during anaerobic respiration, the energetic situation for the bacteria is very similar to that for aerobic growth with respect to delta G'Phos and delta p whereas, for fermentation, a significant decrease in delta p was observed. The consequences for the cellular energetics and for the regulation of the aerobic/anaerobic transition are discussed.

Adenosine Diphosphate↗
PubMed1996

Effect of dopamine, dimethoxyphenylethylamine, papaverine, and related compounds on mitochondrial respiration and complex I activity.

We report the effect of papaverine, tetrahydro-papaverine, laudanosine, dimethoxyphenylethylamine, dopamine, and its metabolites on mitochondrial respiration and activities of the enzymes in the electron transfer complexes, as mitochondrial toxins may be implicated in the etiology and the pathogenesis of Parkinson's disease. Papaverine was the most potent inhibitor of complex I and NADH-linked mitochondrial respiration among the compounds tested next to rotenone. Tetrahydropapaverine, dimethoxyphenylethylamine, and laudanosine also inhibited NADH-linked mitochondrial respiration and complex I activity in this order. Dopamine and its metabolites showed either no inhibition or only very week inhibition. Compounds with dimethoxy residues in the phenyl ring were associated with more potent inhibition of complex I than those without. Our results warrant further studies on these and some related compounds as candidate neurotoxins causing Parkinson's disease.

Animals↗
PubMed2002

Release of allergens as respirable aerosols: A link between grass pollen and asthma.

BACKGROUND: Asthma incidence has long been linked to pollen, even though pollen grains are too large to penetrate into the airways where asthmatic responses originate. Pollen allergens found in small, respirable particles have been implicated in a number of asthma epidemics, particularly ones following rainfall or thunderstorms. OBJECTIVE: The aim of this study was to determine how pollen allergens form the respirable aerosols necessary for triggering asthma. METHODS: Flowering grasses were humidified and then dried in a controlled-environment chamber connected to a cascade impactor and an aerosol particle counter. Particles shed from the flowers were analyzed with high-resolution microscopy and immunolabeled with rabbit anti-Phl p 1 antibody, which is specific for group 1 pollen allergens. RESULTS: Contrary to what has been reported in other published accounts, most of the pollen in this investigation remained on the open anthers of wind pollinated plants unless disturbed-eg, by wind. Increasing humidity caused anthers to close. After a cycle of wetting and drying followed by wind disturbance, grasses flowering within a chamber produced an aerosol of particles that were collected in a cascade impactor. These particles consisted of fragmented pollen cytoplasm in the size range 0.12 to 4.67 microm; they were loaded with group 1 allergens. CONCLUSION: Here we provide the first direct observations of the release of grass pollen allergens as respirable aerosols. They can emanate directly from the flower after a moisture-drying cycle. This could explain asthmatic responses associated with grass pollination, particularly after moist weather conditions.

Aerosols↗
PubMed1974

Requirement for a functional respiration-coupled D-fructose transport system for induction of phosphoenolypyruvate:D-fructose phosphotransferase activity.

Previous studies have shown that Arthrobacter pyridinolis can transport D-fructose or L-rhamnose using either a phosphoenolpyruvate:hexose phosphotransferase (phosphoenolpyruvate:protein phosphotransferase, EC 2.7.3.9) system or a respiration-coupled transport system which requires the presence of exogenous L-malate. A mutant, AP4374, which is deficient in the D-fructose-specific component of the respiration-coupled system can grow on L-rhamnose using the phosphotransferase system, but cannot grow on D-fructose at all. AP4374 fails to produce the inducible D-fructose-specific phosphotransferase components (enzyme II and factor III) when grown in the presence of D-fructose. These results indicate a requirement for a functional respiration-coupled transport system for induction of the phosphotransferase system. The results further suggest that sufficient free D-fructose (or D-fructose 6-phosphate derived from it) must be present inside the cell in order for induction of the phosphotransferase system to occur. The entry of sufficient fructose to cause induction of the phosphotransferase system cannot occur by facilitated diffusion in the absence of energy coupling.

Arthrobacter↗
PubMed1986

Response of two pea hybrids to CO2 enrichment: a test of the energy overflow hypothesis for alternative respiration.

Two pea (Pisum sativum L.) hybrids differing in the presence or absence of the cyanide-resistant (alternative) pathway of respiration were constructed by reciprocally crossing cv. Alaska and cv. Progress No. 9. The F1 hybrids were grown in greenhouses maintained at either 350 or 650 ppm CO2, and the growth, flowering, and dry matter accumulation were compared. The objective was to assess the significance of the alternative respiratory pathway to whole-plant carbon budgets and further to test the hypothesis that the alternative pathway is important in oxidizing excess carbohydrates such as might accumulate under conditions of CO2 enrichment. More carbohydrates were available in the F1 hybrid lacking the pathway, as evidenced by greater plant height, leaf area, specific leaf weight, and total dry matter compared with the reciprocal hybrid, especially at 650 ppm CO2. Specific leaf weight increased markedly under CO2 enrichment in the hybrid lacking the pathway, while it was the same at 350 and 650 ppm in the reciprocal cross. The hybrid lacking the alternative pathway also outperformed the reciprocal cross in terms of total dry matter and seed production. Increased branching with CO2 enrichment was observed in the hybrid lacking the pathway, while branching in the reciprocal cross was only slightly stimulated. These results suggest that alternative respiration consumes luxury carbohydrate and that respiration via this pathway may be considered energetically wasteful in terms of whole-plant carbon budgets.

Carbohydrate Metabolism↗
PubMed1987

Inhibition of glycolate and D-lactate metabolism in a Chlamydomonas reinhardtii mutant deficient in mitochondrial respiration.

The possibility that glycolate oxidation in unicellular green algae is linked to mitochondrial electron transport, rather than to peroxisomal metabolism as in higher plants and animals, was studied in a mutant of Chlamydomonas reinhardtii (dk97) deficient in cytochrome oxidase. This mutant had normal rates of dark respiration (40 +/- 15 mumol of O(2) uptake per hr per mg of chlorophyll) but had only 11% of wild-type levels of cytochrome oxidase activity. Salicylhydroxamic acid (SHAM) reduced the dark respiration rate of dk97 cells by 71%, but cyanide did not significantly inhibit this rate. During photosynthesis in the presence of SHAM, glycolate oxidation was blocked, resulting in glycolate accumulation and excretion by mutant cells but not by wild-type Chlamydomonas. D-Lactate, which accumulated after brief periods of anaerobiosis in Chlamydomonas, was reoxidized by air-grown cells only aerobically in the light, and reoxidation of D-lactate was blocked by SHAM in the dk97 cells. Thus, glycolate and D-lactate dehydrogenase activities are both linked to mitochondrial electron transport in Chlamydomonas. During photosynthetic (14)CO(2) fixation by dk97 cells in the presence of SHAM, (14)C-labeled tricarboxylic acid cycle intermediates accumulated, indicating that, in Chlamydomonas, mitochondrial respiration functions during photosynthesis.

Journal Article↗
PubMed1998

The ATPase and protease domains of yeast mitochondrial Lon: roles in proteolysis and respiration-dependent growth.

The ATP-dependent Lon protease of Saccharomyces cerevisiae mitochondria is required for selective proteolysis in the matrix, maintenance of mitochondrial DNA, and respiration-dependent growth. Lon may also possess a chaperone-like function that facilitates protein degradation and protein-complex assembly. To understand the influence of Lon's ATPase and protease activities on these functions, we examined several Lon mutants for their ability to complement defects of Lon-deleted yeast cells. We also developed a rapid procedure for purifying yeast Lon to homogeneity to study the enzyme's activities and oligomeric state. A point mutation in either the ATPase or the protease site strongly inhibited the corresponding activity of the pure protein but did not alter the protein's oligomerization; when expressed at normal low levels neither of these mutant enzymes supported respiration-dependent growth of Lon-deleted cells. When the ATPase- or the protease-containing regions of Lon were expressed as separate truncated proteins, neither could support respiration-dependent growth of Lon-deleted cells; however, coexpression of these two separated regions sustained wild-type growth. These results suggest that yeast Lon contains two catalytic domains that can interact with one another even as separate proteins, and that both are essential for the different functions of Lon.

ATP-Dependent Proteases↗
PubMed2001

Mitochondria in eosinophils: functional role in apoptosis but not respiration.

In most eukaryotic cells, mitochondria use the respiratory chain to produce a proton gradient, which is then harnessed for the synthesis of ATP. Recently, mitochondrial roles in regulation of apoptosis have been discovered in many cell types. Eosinophils (Eos) die by apoptosis, but the presence and function of mitochondria in Eos are unknown. This study found that Eos contain mitochondria in small numbers, as shown by labeling with membrane potential-sensitive dyes and in situ PCR for a mitochondrial gene. Eos generate mitochondrial membrane potential from hydrolysis of ATP rather than from respiration, as shown by mitochondrial respiratory inhibitors and mitochondrial uncouplers. The mitochondria provide insignificant respiration but can induce apoptosis, as shown by using the mitochondrial F(1)F(0)-ATPase inhibitor oligomycin and translocation of cytochrome c. Thus during differentiation of Eos, although respiration is lost, the other central role of mitochondria, the induction of apoptosis, is retained.

Apoptosis↗
PubMed2000

Altered mitochondrial sensitivity for ADP and maintenance of creatine-stimulated respiration in oxidative striated muscles from VDAC1-deficient mice.

Voltage-dependent anion channels (VDACs) form the main pathway for metabolites across the mitochondrial outer membrane. The mouse vdac1 gene has been disrupted by gene targeting, and the resulting mutant mice have been examined for defects in muscle physiology. To test the hypothesis that VDAC1 constitutes a pathway for ADP translocation into mitochondria, the apparent mitochondrial sensitivity for ADP (Km(ADP)) and the calculated rate of respiration in the presence of the maximal ADP concentration (Vmax) have been assessed using skinned fibers prepared from two oxidative muscles (ventricle and soleus) and a glycolytic muscle (gastrocnemius) in control and vdac1(-/-) mice. We observed a significant increase in the apparent Km((ADP)) in heart and gastrocnemius, whereas the V(max) remained unchanged in both muscles. In contrast, a significant decrease in both the apparent Km((ADP)) and V(max) was observed in soleus. To test whether VDAC1 is required for creatine stimulation of mitochondrial respiration in oxidative muscles, the apparent Km((ADP)) and Vmax were determined in the presence of 25 mm creatine. The creatine effect on mitochondrial respiration was unchanged in both heart and soleus. These data, together with the significant increase in citrate synthase activity in heart, but not in soleus and gastrocnemius, suggest that distinct metabolic responses to altered mitochondrial outer membrane permeability occur in these different striated muscle types.

Adenosine Diphosphate↗
PubMed2002

Differential sensitivity of guanylyl cyclase and mitochondrial respiration to nitric oxide measured using clamped concentrations.

Nitric oxide (NO) signal transduction may involve at least two targets: the guanylyl cyclase-coupled NO receptor (NO(GC)R), which catalyzes cGMP formation, and cytochrome c oxidase, which is responsible for mitochondrial O(2) consumption and which is inhibited by NO in competition with O(2). Current evidence indicates that the two targets may be similarly sensitive to NO, but quantitative comparison has been difficult because of an inability to administer NO in known, constant concentrations. We addressed this deficiency and found that purified NO(GC)R was about 100-fold more sensitive to NO than reported previously, 50% of maximal activity requiring only 4 nm NO. Conversely, at physiological O(2) concentrations (20-30 microM), mitochondrial respiration was 2-10-fold less sensitive to NO than estimated beforehand. The two concentration-response curves showed minimal overlap. Accordingly, an NO concentration maximally active on the NO(GC)R (20 nm) inhibited respiration only when the O(2) concentration was pathologically low (50% inhibition at 5 microM O(2)). Studies on brain slices under conditions of maximal stimulation of endogenous NO synthesis suggested that the local NO concentration did not rise above 4 nm. It is concluded that under physiological conditions, at least in brain, NO is constrained to target the NO(GC)R without inhibiting mitochondrial respiration.

Animals↗
PubMed2006

Hap4 is not essential for activation of respiration at low specific growth rates in Saccharomyces cerevisiae.

In Saccharomyces cerevisiae, the heme-activated protein complex Hap2/3/4/5 plays a major role in the transcription of genes involved in respiration. Thus, overexpression of HAP4 has been shown to result in a 10% increase in the respiratory capacity. Here the physiology of a HAP4-deleted S. cerevisiae strain was investigated, and we found that the hap4delta S. cerevisiae exhibited poor growth on ethanol, although the growth rate on glucose was indifferent from the wild type in aerobic as well as anaerobic cultures. Moreover, it exhibited a large (75%) reduction in the critical glucose uptake rate at which fermentative metabolism is onset, indicating a substantial reduction in respiratory capacity. We also performed whole genome transcription analysis for the hap4delta and the wild type, grown in carbon-limited chemostat cultures operated at a dilution rate of 0.05 h(-1). Although both strains exhibited respiratory metabolism, there was significant change in expression of many genes in the hap4delta strain. These genes are involved in several different parts of the metabolism, including oxidative stress response, peroxisomal functions, and energy generation. This study strongly indicates that Hap4 activation only occurs at intermediate specific growth rates, below which the transcription of genes responsible for respiration is dependent on the Hap2/3/5 complex and above which the Hap4 protein augments the transcription. Furthermore, statistical analysis of the transcription data and integration of the data with a genome scale metabolic network provided new insight and evidence for the role of Hap4 in transcriptional regulation of mitochondrial respiration.

Biomass↗
PubMed1982

Metabolic effects of a mixed and a high-carbohydrate low-fat diet in man, measured over 24 h in a respiration chamber.

1. The relation between dietary carbohydrate: lipid ratio and the fuel mixture oxidized during 24 h was investigated in eleven healthy volunteers (six females, and five males) in a respiration chamber. Values of the fuel mixture oxidized were estimated by continuous indirect calorimetry and urinary nitrogen measurements. 2. The subjects, were first given a mixed diet for 7 d and spent the last 24 h of the 7 d period in a respiration chamber for continuous gas-exchange measurement. The fuels oxidized during 2.5 h or moderate exercise were also measured in the respiration chamber. After an interval of 2 weeks from the end of the mixed-diet period, the same subjects were given an isoenergetic high-carbohydrate low-fat diet for 7 d, and the same experimental regimen was repeated. 3. Dietary composition markedly influenced the fuel mixture oxidized during 24 h and this effect was still present 12 h after the last meal in the postabsorptive state. However, the diets had no influence on the substrates oxidized above resting levels during exercise. With both diets, the 24 h energy balance was slightly negative and the energy deficit was covered by lipid oxidation. 4. With the high-carbohydrate low-fat diet, the energy expenditure during sleep was found to be higher than that with the mixed diet. 5. It is concluded that: (a) the composition of the diet did not influence the fuel mixture utilized for moderate exercise, (b) the energy deficit calculated for a 24 h period was compensated by lipid oxidation irrespective of the carbohydrate content of the diet, (c) energy expenditure during sleep was found to be higher with the high-carbohydrate low-fat diet than with the mixed diet.

Adult↗