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PubMed1993

A gene, SMP2, involved in plasmid maintenance and respiration in Saccharomyces cerevisiae encodes a highly charged protein.

The smp2 mutant of Saccharomyces cerevisiae shows increased stability of the heterologous plasmid pSR1 and YRp plasmids. A DNA fragment bearing the SMP2 gene was cloned by its ability to complement the slow growth of the smp2 smp3 double mutant (smp3 is another mutation conferring increased stability of plasmid pSR1). The nucleotide sequence of SMP2 indicated that it encodes a highly charged 95 kDa protein. Disruption of the genomic SMP2 gene resulted in a respiration-deficient phenotype, although the cells retained mitochondrial DNA, and showed increased stability of pSR1 like the original smp2 mutant. The fact that the smp2 mutant is not always respiration deficient and shows increased pSR1 stability even in a rho0 strain lacking mitochondrial DNA suggested that the function of the Smp2 protein in plasmid maintenance is independent of respiration. The SMP2 locus was mapped at a site 71 cM from lys7 and 21 cM from ilv2/SMR1 on the right arm of chromosome XIII.

Amino Acid Sequence↗

PubMed1993

The GEF1 gene of Saccharomyces cerevisiae encodes an integral membrane protein; mutations in which have effects on respiration and iron-limited growth.

We have isolated a new class of respiration-defective, i.e petite, mutants of the yeast Saccharomyces cerevisiae. Mutations in the GEF1 gene cause cells to grow slowly on rich media containing carbon sources utilized by respiration. This phenotype is suppressed by adding high concentrations of iron to the growth medium. Gef1- mutants also fail to grow on a fermentable carbon source, glucose, when iron is reduced to low concentrations in the medium, suggesting that the GEF1 gene is required for efficient metabolism of iron during growth on fermentable as well as respired carbon sources. However, activity of the iron uptake system appears to be unaffected in gef1- mutants. Fe(II) transporter activity and regulation is normal in gef1- mutants. Fe(III) reductase induction during iron-limited growth is disrupted, but this appears to be a secondary effect of growth rate alterations. The wild-type GEF1 gene was cloned and sequenced; it encodes a protein of 779 amino acids, 13 possible transmembrane domains, and significant similarity to chloride channel proteins from fish and mammals, suggesting that GEF1 encodes an integral membrane protein. A gef1- deletion mutation generated in vitro and introduced into wild-type haploid strains by gene transplacement was not lethal. Oxygen consumption by intact gef1- cells and by mitochondrial fractions isolated from gef1- mutants was reduced 25-50% relative to wild type, indicating that mitochondrial function is defective in these mutants. We suggest that GEF1 encodes a transport protein that is involved in intracellular iron metabolism.

Amino Acid Sequence↗

PubMed1986

Expression of the SOS system in Escherichia coli growing under nitrate respiration conditions.

Induction of several SOS functions by mitomycin C, bleomycin or thermal treatment of a recA441 mutant growing under nitrate respiration conditions was studied in Escherichia coli. Mitomycin C caused inhibition of cell division, induction of prophages and expression of umuC gene but like in aerobically growing cells, it did not trigger the cessation of cell respiration. On the contrary, both recA+ and recA441 cultures either treated with bleomycin or incubated at 42 degrees C failed to induce any of the different SOS functions cited above. Furthermore, after bleomycin addition or thermal treatment both recA+ and recA441 cultures did not present any variation in the cellular ATP level, contrary to what happens under aerobic growth. The blocking of the expression of some SOS functions under nitrate respiration conditions is not an irreversible process because cells incubated under these anaerobic conditions were able to induce the SOS system when changed to an aerobic medium 30 min after the SOS-inducing treatment had been applied.

Adenosine Triphosphate↗

PubMed1977

Reversion by Fe(III) of the inhibition by hydroxamic acids of the cyanide-insensitive respiration in the yeast Saccharomycopsis lipolytica.

The specific inhibitory effect of benzhydroxamic acid on the cyanide-insensitive respiration could be reversed in whole cells of the yeast Saccharomycopsis lipolytica, by addition of Fe(III), in a way suggesting a competition between the added iron and an enzyme-bound metallic ion, both central atoms for the ligand benzhydroxamic acid. The possibility that added metal ions modify the penetration of BHAM into the cells was ruled out. Co(II), Cu(II) and Al(III) could substitute for Fe(III). A linear relation between the concentration in added Fe(III) and the reversed respiration rate was observed. At a given cell concentration, the reversion by added Fe(III) of the inhibitory effect of benzhydroxamic acid on the alternative respiration appeared more related to the degree of inhibition rather than to the concentration in added inhibitor. Increasing cell concentrations required increasing amounts of Fe(III) to reach the same level of reversion. No reversal occurred at concentrations in added Fe(III) lower than 0.1 mM, whatever the benzhydroxamic concentration, the cell concentration or the yeast batch.

Ascomycota↗

PubMed1985

Antimycin A- and hydroxamate-insensitive respiration in yeasts.

In this paper evidence is presented for the mitochondrial localization of the antimycin A (AA) + salicylhydroxamate (SHAM)-insensitive respiration of the yeasts Kluyveromyces lactis, Endomycopsis capsularis and Hansenula saturnus. Such a respiration, which can be sustained by NADH and NADPH but not by succinate, is inhibited by high concentrations of azide. AA + SHAM-insensitive respiration is not phosphorylating and its postulated physiological role is to oxidize NADH.

Antifungal Agents↗

PubMed1992

Isolation and characterization of respiration-deficient mutants from the pathogenic yeast Candida albicans.

The isolation of several respiration deficient mutants of the pathogenic yeast Candida albicans is described. These show greatly reduced respiration rates, loss of cytochromes aa3 and b, and reduced growth rates. All of the mutants had lost the ability to assimilate a wide range of carbon sources. Ultrastructural studies showed reduced development of mitochondrial cristae in the mutants. The mutants can be divided into three classes depending on their respiration responses to the addition of cyanide.

Antimycin A↗

PubMed1995

A possible mechanism for the cytotoxicity of a polyacetylenic alcohol, panaxytriol: inhibition of mitochondrial respiration.

A polyacetylenic alcohol, panaxytriol, isolated from Panax ginseng C. A. Meyer inhibits both tumor cell growth in vitro and the growth of B16 melanoma transplanted into mice. Our preliminary studies indicated that panaxytriol localizes to the mitochondria in human breast carcinoma cells (Breast M25-SF). This study focused on the effects of panaxytriol on mitochondrial structures and function in Breast M25-SF. The results indicate that panaxytriol rapidly inhibits cellular respiration and disrupts cellular energy balance in Breast M25-SF. At concentrations between 11.3 and 180 microM, panaxytriol causes a dose-dependent inhibition of the conversion of the tetrazolium (MTT assay) by mitochondrial dehydrogenase within 2 h. A 1-h treatment with 180 microM panaxytriol causes a significant loss of rhodamine-123 from cells with mitochondria prestained with rhodamine-123 (by flow cytometry). Specific toxic changes were observed by electron microscopy in the mitochondria of Breast M25-SF within 1 h after treatment with more than 180 microM panaxytriol. These data indicate that 180 microM panxytriol rapidly disrupts cellular energy balance and respiration in Breast M25-SF and suggest that panaxytriol may lower cellular ATP concentrations. After treatment with 180 microM panaxytriol, cellular ATP levels were 40% of those in control cells after 1 h. ATP depletion preceded the loss of cellular viability. Neither ATP depletion nor cytolysis was found in human erythrocytes that have no mitochondria. Thus, ATP depletion resulting from a direct inhibition of mitochondrial respiration is a critical early event in the cytotoxicity of panaxytriol.

Adenosine Diphosphate↗

PubMed1995

Cellular hypertrophy in cardiomyopathic patients is associated with lower creatine-stimulated mitochondrial respiration.

The mitochondrial respiration rate and morphometric indices in endomyocardial biopsy samples were measured in 43 patients with dilated cardiomyopathy selected in accordance to WHO criteria by endomyocardial biopsy studies after excluding of various forms of myocarditis, alcoholic cardiomyopathy and other specific diseases of the heart. A group of 13 patients with unusually high mean myocyte diameter, 30 +/- 4 microns, and nuclear size, 57 +/- 5 microns, was selected. The remainder of patients (n = 30) had significantly lower mean myocyte diameter and nuclear size, 23 +/- 3 and 42 +/- 6 microns, respectively, (p < 0.01). Creatine-stimulated elevation in mitochondrial respiration rate as measured in saponin-skinned fibers was found in the former group to be much lower (36 +/- 4%) as compared with the remainder (90 +/- 12%). Also, the former group of patients had higher left ventricular enddiastolic pressure and volume index with concomitantly decreased ejection fraction. The results indicate that marked nuclear and cellular hypertrophy is associated with lower creatine-stimulated mitochondrial respiration rate and more severe cardiac failure. They suggest that disorders in energy supply to myofibrils may be related to disturbances in cellular genetic apparatus.

Adult↗

PubMed1977

The position of nitrate respiration in evolution.

Egami's hypothesis that oxygen respiration evolved from nitrate respiration, and this from nitrate fermentation, is not accepted. The reasons are: (1) Presumably there was no nitrate before O2 in the biosphere. (2) On mechanistic grounds, respiration (oxidative phosphorylation) is to be derived directly from photosynthesis (photosynthetic phosphorylation) rather than from any form of fermentation.

Biological Evolution↗

PubMed1990

Inhibition of mitochondrial respiration by 1,2,3,4-tetrahydroisoquinoline-like endogenous alkaloids in mouse brain.

Since the discovery of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonism, it has been postulated that (a) MPTP-like toxin(s) such as 1,2,3,4-tetrahydroisoquinoline (TIQ) may induce Parkinson's disease. As the neuronal degeneration in MPTP-induced parkinsonism is thought to be caused by the inhibition of the mitochondrial respiration by 1-methyl-4-phenylpyridinium ion (MPP+), we studied the effects of TIQ-like alkaloids including dopamine-derived ones on the mitochondrial respiration using mouse brains. TIQ, tetrahydropapaveroline (THP), and tetrahydropapaverine (THPV) produced significant inhibition of the state 3 and 4 respiration and respiratory control ratio supported by glutamate + malate, the activity of Complex I and the ATP synthesis. Among those compounds, THPV was most potent. Toxic properties of these compounds on mitochondria were quite similar to that of MPP+. Our results support the hypothesis that (a) MPTP- or MPP(+)-like substance(s) may be responsible for the nigral degeneration in Parkinson's disease.

Adenosine Triphosphate↗

PubMed1991

Antidepressants and brain respiration.

Imipramine and clorgyline, at concentrations of 0.002 M, inhibit the respiration of brain tissue by 82 and 71 per cent respectively, while chloropromazine and tranylcypromine, at concentrations of 0.01 M, inhibit it about 25 per cent. Deprenyl and amphetamine at a concentration of 0.002 M inhibit brain tissue respiration by 12 and 18 per cent respectively. Respiration in brain is least affected by lithium chloride (only 5 per cent inhibition).

Amphetamine↗

PubMedDate not supplied

Metabolic compartmentation and substrate channelling in muscle cells. Role of coupled creatine kinases in in vivo regulation of cellular respiration--a synthesis.

The published experimental data and existing concepts of cellular regulation of respiration are analyzed. Conventional, simplified considerations of regulatory mechanism by cytoplasmic ADP according to Michaelis-Menten kinetics or by derived parameters such as phosphate potential etc. do not explain relationships between oxygen consumption, workload and metabolic state of the cell. On the other hand, there are abundant data in literature showing microheterogeneity of cytoplasmic space in muscle cells, in particular with respect to ATP (and ADP) due to the structural organization of cell interior, existence of multienzyme complexes and structured water phase. Also very recent experimental data show that the intracellular diffusion of ADP is retarded in cardiomyocytes because of very low permeability of the mitochondrial outer membrane for adenine nucleotides in vivo. Most probably, permeability of the outer mitochondrial membrane porin channels is controlled in the cells in vivo by some intracellular factors which may be connected to cytoskeleton and lost during mitochondrial isolation. All these numerous data show convincingly that cellular metabolism cannot be understood if cell interior is considered as homogenous solution, and it is necessary to use the theories of organized metabolic systems and substrate-product channelling in multienzyme systems to understand metabolic regulation of respiration. One of these systems is the creatine kinase system, which channels high energy phosphates from mitochondria to sites of energy utilization. It is proposed that in muscle cells feed-back signal between contraction and mitochondrial respiration may be conducted by metabolic wave (propagation of oscillations of local concentration of ADP and creatine) through cytoplasmic equilibrium creatine and adenylate kinases and is amplified by coupled creatine kinase reaction in mitochondria. Mitochondrial creatine kinase has experimentally been shown to be a powerful amplifier of regulatory action of weak ADP fluxes due to its coupling to adenine nucleotide translocase. This phenomenon is also carefully analyzed.

Adenosine Diphosphate↗

PubMed1976

Oxygen transfer rate, respiration and yields in batch and chemostat cultures of Klebsiella aerogenes.

The effect was studied of oxygen supply on the changes in total and specific rate of oxygen consumption by the cells, oxygen transfer rate, saturation concentrations of dissolved oxygen and the yields of batch and continuous cultivations. Experiments were done on the microorganism Klebsiella aerogenes CCM 2318 growing on synthetic glucose medium. Continuous cultivations were carried out at dilution rates of 0.96 and 0.178 h-1. The rate of oxygen transfer was determined by the sulphite method and the coefficient KLa was assessed using the dynamic method with a correction for changes in the saturations of dissolved oxygen. A lowered oxygen supply in batch cultivations caused deformations in the course of cell respiration. Comparison of results of batch and continuous cultivations showed that the highest yields Y X/S and Y X/O are attained at low dilution rates without oxygen limitation. Batch cultivations, on the other hand, exhibit the lowest yields and the highest cell respiration levels. In both types of cultivations, a respiration peak was ascertained under the conditions of growth limitation by oxygen.

Culture Media↗

PubMed1996

Effect of temperature and yeast extract on microbial respiration of sediments from a shallow coastal subsurface and vadose zone.

As a part of our study on microbial heterogeneity in subsurface environments, we have examined the microbial respiration of sediment samples obtained from a coastal site near Oyster, VA. The sediments at the site are unconsolidated, fine to coarse beach sand and gravel. A Columbus Instruments Micro-Oxymax Respirometer was used to measure the rate of carbon dioxide (CO2) production during the respiration of the sediment samples. The rate of respiration of the sediment samples ranged from 0.035-0.6 microL CO2/h/g of the sediment. The sediment samples showing maximum (0.6 microL CO2/h/g) and minimum (0.035 microL CO2/h/g) production of CO2 were selected to study the effect of micronutrient-yeast extract (0.5 and 1.0 micrograms/g of the sediment) and water (0.5 and 1.0 mL) on the rate of CO2 production. The rate of CO2 production increased with the addition of water, but increased approx 2 orders of magnitude (from 0.26 to an average of 23.5 microL CO2/h/g) when 1.0 g/g yeast extract was added to the sediment samples. In these coastal sediments, temperature, depth, and addition of water influenced microbial activity, but the addition of 1.0 microgram/g yeast extract as a micronutrient rapidly increased the rate of CO2 production 2 orders of magnitude.

Biotechnology↗

PubMed2005

Irradiance regulation of photosynthesis and respiration in modern marine microbialites built by benthic cyanobacteria in a tropical lagoon (New Caledonia).

Microbialites are organosedimentary deposits that have built up as a result of the growth and binding of detrital sediment by a benthic microbial community. This study focuses on microbialites built by monospecific populations of cyanobacteria in the south-west lagoon of New Caledonia, where they have been observed down to 20-25 m depth. The aim was to study their photosynthetic and respiratory responses to various light intensities. The Phormidium sp. TK1 microbialite was collected at 19 m depth and the P. crosbyanum (Tilden) microbialite was collected at 0.5 and 13 m depth. Phormidium sp. TK1 showed all the characteristic features of a low-light adapted species. The initial slope of the Photosynthesis versus Irradiance curve for this microbialite was close to the maximum quantum yield indicating an efficient light absorption and utilization at low light. The photosynthesis maximum was located 0.2-0.4 mm below the surface and did not shift with changing light intensity. Respiration rates were low and not enhanced by light; photoinhibition was observed at higher light intensities. In Phormidium crosbyanum (Tilden) microbialites, the photosynthesis maximum shifted downward to lower depths with increasing light, probably as a result of phototactic migration of cyanobacterial filaments, and light-enhanced respiration was observed at light intensities above light saturation. The photosynthetic para- meters measured in P. crosbyanum indicate that P. crosbyanum is capable of photo-acclimation at high light intensities. The gross productivity of the different microbialites was comparable to values measured in cyanobacterial stromatolites observed in other shallow environments. However, the microbialites studied here were characterized by a lower respiration / production ratio which indicates a higher growth efficiency.

Chromatography, High Pressure Liquid↗

PubMed2005

Respiration artifacts in whole-body (18)F-FDG PET/CT studies with combined PET/CT tomographs employing spiral CT technology with 1 to 16 detector rows.

PURPOSE: Co-registration accuracy in combined whole-body (WB) PET/CT imaging is impaired by respiration-induced mismatches between the CT and the PET. Furthermore, PET/CT misregistration may bias the PET tracer distribution following CT-based attenuation correction (CT-AC). With the introduction of multi-row CT technology of up to 16 detector rows into PET/CT designs, we investigated the incidence of respiration artifacts in WB PET/CT examinations of patients who were unable to follow any breath-hold instructions. METHODS: A total of 80 WB studies from six international sites operating PET/CT tomographs with 1-, 2-, 4-, 6-, 8-, and 16-row spiral CT were included. PET/CT examinations were acquired with the patients breathing normally during both the CT and the PET scan, and CT-AC was performed routinely. All studies were anonymized and reviewed independently by three radiologists and three nuclear medicine specialists. We report the frequency and severity of artifacts on CT and PET for the thorax and the abdomen. RESULTS: In WB PET/CT imaging of normally breathing patients, significant gains in diagnostic image quality can be expected from employing CT technology with six or more detector rows. In our study, fewer PET images appear distorted than corresponding CT images, which is due to the limited propagation of only mild CT image artifacts after the resampling of the CT-based attenuation map during CT-AC. CONCLUSION: In whole-body PET/CT imaging of normally breathing patients, respiration-induced artifacts are reduced in both magnitude and prominence for PET/CT systems employing CT components of six or more detector rows.

Adolescent↗

PubMed2004

Secondary metabolites of the grapevine pathogen Eutypa lata inhibit mitochondrial respiration, based on a model bioassay using the yeast Saccharomyces cerevisiae.

Acetylenic phenols and a chromene isolated from the grapevine fungal pathogen Eutypa lata were examined for mode of toxicity. The compounds included eutypine (4-hydroxy-3-[3-methyl-3-butene-1-ynyl] benzyl aldehyde), eutypinol (4-hydroxy-3-[3-methyl-3-butene-1-ynyl] benzyl alcohol), eulatachromene, 2- isoprenyl-5-formyl-benzofuran, siccayne, and eulatinol. A bioassay using the yeast Saccharomyces cerevisiae showed that all compounds were either lethal or inhibited growth. A respiratory assay using 2,3,5-triphenyltetrazolium (TTC) indicated that eutypinol and eulatachromene inhibited mitochondrial respiration in wild-type yeast. Bioassays also showed that 2- isoprenyl-5-formyl-benzofuran and siccayne inhibited mitochondrial respiration in the S. cerevisiae deletion mutant vph2Delta, lacking a vacuolar type H (+) ATPase (V-ATPase) assembly protein. Cell growth of tsa1Delta, a deletion mutant of S. cerevisiae lacking a thioredoxin peroxidase (cTPx I), was greatly reduced when grown on media containing eutypinol or eulatachromene and exposed to hydrogen peroxide (H(2)O(2)) as an oxidative stress. This reduction in growth establishes the toxic mode of action of these compounds through inhibition of mitochondrial respiration.

Alkynes↗

PubMed1998

The coordination and interaction between respiration and deglutition in young pigs.

The anatomical pathways for inspired air and ingested food cross in the pharynx of mammals, implying that breathing and swallowing must be separated either in space or in time. In this study we investigated the time relationship between swallowing and respiration in young pigs, as a model for suckling mammals. Despite the high morphological position of the larynx in young mammals, allowing liquid to pass in food channels lateral to the larynx, respiration and swallowing are not wholly independent events. Although, when suckling on a veterinary teat, the swallows occurred at various points in the respiratory cycle, there was always a period of apnea associated with the swallow. Finally, an increase in the viscosity of the milk altered this coordination, changing respiratory cycle length and also restricting the relative rate at which swallows occurred in some parts of the respiratory cycle. These results suggest that the subsequent changes in respiratory activity at weaning, associated with passage of a solid bolus over the larynx, is preceded by the ability of the animal to alter coordination between respiration and swallowing for a liquid bolus.

Animals↗