scholarly journals Assays of the metabolic viability of single giant mitochondria. Experiments with intact and impaled mitochondria.

1978 ◽  
Vol 78 (1) ◽  
pp. 214-226 ◽  
Author(s):  
B L Maloff ◽  
S P Scordilis ◽  
H Tedeschi
Keyword(s):  
Calcium Phosphate ◽  
Oxidative Phosphorylation ◽  
Psoas Muscle ◽  
Energy Coupling ◽  
Antimycin A ◽  
Giant Mitochondria ◽  
Close Proximity ◽  
Muscle Contract ◽  
Optically Detected ◽  
Hydrolysis Of

Single giant mitochondria isolated from mice fed cuprizone were assayed for their metabolic viability. Two tests were devised. One test optically detected the accumulation of calcium phosphate within the mitochondria under massive loading conditions (including the presence of succinate and ATP). The accumulation corresponds to a test of energy coupling from either electron transport or the hydrolysis of ATP since it is blocked by either antimycin A or oligomycin. The other assay tested for the production of ATP from ADP and Pi, using myofibrils. Myofibrils prepared from glycerinated rabbit psoas muscle contract only in the presence of ATP and not in the presence of ADP. Myofibrillar contraction is unaffected by the presence of antimycin A or oligomycin. However, myofibrils in the presence of mitochondria that are phosphorylating ADP to ATP do contract. This contraction is blocked by antimycin A and/or oligomycin. Hence, the ATP which causes myofibrillar contraction is produced by oxidative phosphorylation. At low mitochondrial concentration, only the myofibrils in close proximity with mitochondria contract in the presence of ADP. Therefore the assay can be used to test the viability of individual mitochondria. Individual giant mitochondria were found to be viable, using both of these assays. Comparable results were obtained in mitochondria impaled with microelectrodes. The potentials and resistances were unaffected by concomitant calcium phosphate accumulation or oxidative phosphorylation.

Conservation of structure in ATP-depleted proximal tubules: role of calcium, polyphosphoinositides, and glycine

1993 ◽  
Vol 265 (5) ◽  
pp. F605-F623 ◽  
Author(s):  
R. Garza-Quintero ◽  
J. M. Weinberg ◽  
J. Ortega-Lopez ◽  
J. A. Davis ◽  
M. A. Venkatachalam
Keyword(s):  
Amino Acids ◽  
Phospholipase C ◽  
Cell Structure ◽  
Proximal Tubules ◽  
Atp Depletion ◽  
The Other ◽  
Antimycin A ◽  
Phospholipid Hydrolysis ◽  
Hydrolysis Of

Increases of intracellular free Ca2+ (Caf) may mediate phospholipid hydrolysis and disintegration in energy-compromised cells; on the other hand, glycine and related amino acids preserve structure. We have examined the effects of increased Caf on phospholipids and structure in ATP-depleted cells, as well as how these actions may be modified by glycine. Incubation of isolated proximal tubules with antimycin A led to ATP depletion, delayed increases of Caf to micromolar levels, polyphosphoinositide (PPI) hydrolysis by phospholipase C, and generalized disintegration of cell structure. Glycine inhibited PPI hydrolysis and preserved cell structure in entirety but did not apparently modify the Caf increases. When overwhelming increases of Caf were induced by the additional presence of a Ca2+ ionophore, glycine did not inhibit either the hydrolysis of PPI or disruption of mitochondria and microvilli. However, the cells remained integrated and unbroken. Incubation in low-Ca2+ medium prevented Caf increases, inhibited PPI hydrolysis, and preserved the structure of mitochondria and microvilli. Nevertheless, there was lethal damage by disintegration of all other membranes. This damage was prevented specifically and completely by glycine. Thus compartments of cells were shown to be differentially susceptible to injury from increased Caf or lack of glycine. Although damage by either factor occurs by distinct mechanisms, glycine also appears to have effects that suppress the deleterious effects of Ca2+ so long as Caf increases are not overwhelming. Our results also suggest that the PPI have a major structural role, which may be compromised by Caf increase during ATP depletion.

scholarly journals Oxidative phosphorylation during glycollate metabolism in mitochondria from phototrophic Euglena gracilis

1975 ◽  
Vol 150 (3) ◽  
pp. 373-377 ◽  
Author(s):  
N Collins ◽  
R H Brown ◽  
M J Merrett
Keyword(s):  
Cytochrome C ◽  
Oxygen Uptake ◽  
Oxidative Phosphorylation ◽  
Cytochrome C Oxidase ◽  
Electron Acceptor ◽  
Euglena Gracilis ◽  
Gradient Centrifugation ◽  
Antimycin A ◽  
Isolated Mitochondria ◽  
Glycollate Dehydrogenase

Mitochondria were isolated by gradient centrifugation on linear sucrose gradients from broken cell suspensions of phototrophically grown Euglena gracilis. An antimycin A-sensitive but rotenone-insensitive glycollate-dependent oxygen uptake was demonstrated in isolated mitochondria. The partial reactions of glycollate-cytochrome c oxidoreductase and cytochrome c oxidase were demonstrated by using Euglena cytochrome c as exogenous electron acceptor/donor. Isolated mitochondria contain glycollate dehydrogenase and glyoxylate-glutamate aminotransferase and oxidize exogenous glycine. A P:O ratio of 1.7 was obtained for glycollate oxidation, consistent with glycollate electrons entering the Euglena respiratory chain at the flavoprotein level. The significance of these results is discussed in relation to photorespiration in algae.

O2 uptake in periportal and pericentral regions of liver lobule in perfused liver

1986 ◽  
Vol 250 (6) ◽  
pp. G800-G805 ◽  
Author(s):  
T. Matsumura ◽  
F. C. Kauffman ◽  
H. Meren ◽  
R. G. Thurman
Keyword(s):  
Electron Transport ◽  
Oxidative Phosphorylation ◽  
Cytochrome Oxidase ◽  
Redox State ◽  
Antimycin A ◽  
Perfused Liver ◽  
Maximal Rate ◽  
O2 Uptake ◽  
Liver Lobule ◽  
O2 Concentration

O2 uptake by the perfused liver decreased at O2 concentrations considerably higher than levels that caused NADH reduction when the input O2 concentration was varied. The maximal rate of O2 uptake was two- to threefold higher in periportal (137 +/- 8 mumol . g-1 . h-1; O2 concentration = 478 +/- 37 microM) than pericentral regions (59 +/- 5 mumol . g-1 . h-1; O2 concentration = 263 +/- 21 microM); however, the O2 concentration required for half-maximal O2 uptake was similar (approximately 20 microM) in the two areas. The infusion of atractyloside, antimycin A, or KCN inhibited O2 uptake in both zones by 50–85%, indicating that O2 uptake in both regions was largely dependent on mitochondrial electron transport. The content of ATP and ADP and ATP:ADP were similar in microdissected samples from periportal and pericentral areas. In contrast, when livers were perfused in the retrograde direction, O2 uptake was two- to threefold greater in pericentral than in periportal regions. Maximal rates of O2 uptake correlated with the local O2 concentration irrespective of the direction of flow when the electrode was moved across the liver lobule with a micromanipulator. Lower rates of O2 uptake in pericentral areas were not altered appreciably by infusion of agents known to uncouple oxidative phosphorylation (DNP), increase ADP supply (fructose), or increase the NADH redox state (ethanol or octanoate). These data are consistent with the hypothesis that maximal rates of O2 uptake are regulated, in part, in the perfused liver by O2 concentrations far above the Km of cytochrome oxidase for O2.

Role of oxidative phosphorylation and ATP release in mediating birth-related pulmonary vasodilation in fetal lambs

2002 ◽  
Vol 283 (4) ◽  
pp. H1600-H1608 ◽  
Author(s):  
Girija G. Konduri ◽  
Janine Mattei
Keyword(s):  
Blood Flow ◽  
Oxidative Phosphorylation ◽  
Pulmonary Blood Flow ◽  
Atp Release ◽  
Antimycin A ◽  
Pulmonary Vasodilation ◽  
Oxygen Exposure ◽  
Atp Levels ◽  
Pulmonary Vasodilator ◽  
Independent Effects

We investigated the hypothesis that birth-related pulmonary vasodilation is mediated in part by an increase in oxidative phosphorylation and ATP release in response to oxygen exposure at birth. Studies were done in fetal lambs to evaluate the independent effects of oxygen, lung distension alone, or lung distension accompanied by oxygenation and shear stress on fetal pulmonary blood flow and resistance and plasma ATP levels in the pulmonary artery. The effect of each intervention was evaluated in lambs assigned to one of three groups: control or pretreatment with 2,4-dinitrophenol or antimycin-A, inhibitors of oxidative phosphorylation. Exposure to oxygen alone or with lung distension was associated with increases in plasma ATP levels and pulmonary blood flow and a decrease in pulmonary vascular resistance. Plasma ATP levels did not change during lung distension alone. 2,4-Dinitrophenol and antimycin-A attenuated the pulmonary vasodilator response to oxygen but did not attenuate the response to lung distension alone. An increase in oxidative phosphorylation and ATP release during oxygen exposure may contribute to birth-related pulmonary vasodilation in fetal lambs.

Giant mitochondria in shoot meristems of cacti

1984 ◽  
Vol 42 ◽  
pp. 330-331
Author(s):  
E. R. Rivera
Keyword(s):  
Parasitic Plant ◽  
Antimycin A ◽  
Mitochondrial Ultrastructure ◽  
Anaerobic Conditions ◽  
Giant Mitochondria ◽  
Root Cells ◽  
Similar Morphology ◽  
Common Features ◽  
Unicellular Organisms ◽  
Shoot Meristems

Many unicellular organisms have only a few long mitochondria that weave around through the cytoplasm (1). Addition of antimycin A to Euglena or submission of pumpkin root cells to anaerobic conditions causes fusion of all mitochondria into one long organelle (2,4). All of these examples of large mitochondria have some common features. Usually the long mitochondrion has similar structure throughout its length or the mitochondria that fuse into one have similar morphology. A different configuration of mitochondrial ultrastructure is found in the phloem of the parasitic plant Alectra vogelii Berth. These mitochondria are much larger and differ in appearance from those in cells surrounding the phloem (3).

Phosphopeptides interacting with colloidal calcium phosphate isolated by tryptic hydrolysis of bovine casein micelles

1996 ◽  
Vol 63 (3) ◽  
pp. 405-422 ◽  
Author(s):  
Valerie Gagnaire ◽  
Alice Pierre ◽  
Daniel Molle ◽  
Joelle Leonil
Keyword(s):  
Calcium Phosphate ◽  
Reversed Phase ◽  
Ion Source ◽  
Mass Spectrometry Analysis ◽  
Casein Micelles ◽  
Spectrometry Analysis ◽  
Peptide Fraction ◽  
Colloidal Calcium Phosphate ◽  
Hydrolysis Of ◽  
Tryptic Hydrolysis

SummaryAfter extended tryptic hydrolysis of large bovine casein micelles, a mineral-rich peptide fraction was recovered by ultracentrifugation. Its mineral part contained 72% of the colloidal Ca and 49% of the colloidal Pi originally present in the native micelle. Colloidal nitrogenous components were also present, amounting to 27% of the original N content. They contained most of the phosphopeptides and 82% of the micellar phosphoseryl residues. These tryptic peptides were characterized by reversed-phase HPLC on-line electrospray ion source–mass spectrometry analysis. Among the peptides produced 14 phosphopeptides were identified: αs2-CN(l–24), αs2-CN(1–21), αs1-CN(43–79), αs1-CN(35–79)7P, αs1-CN(35–79)8P, αs1-CN(37–79), αs1-CN(104–119), αs1-CN(104–124), β-CN(1–25), β-CN(1–28), β-CN(1–29), β-CN(30–97), β-CN(33–97) and β-CN(29–97). The proportion of the phosphopeptides interacting with colloidal calcium phosphate was correlated with their relative content of phosphoserine residues, since phosphopeptides containing more than four phos-phoserine residues were consistently present within this fraction. It also appeared that other types of peptides, some of them hydrophobic in nature, were also partly or completely present within the colloidal fraction, including αs1-CN(91–100), αs1-CN(152–193), αs1-CN(23–34), αs1-CN(125–193), αs1-CN(125–199), β-CN(177–209), β-CN( 184–209), β-CN(114–169) and β-CN(108–169). Their possible involvement in the micellar backbone is discussed.

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