scholarly journals Cholesterol increase in mitochondria: its effect on inner-membrane functions, submitochondrial localization and ultrastructural morphology

1993 ◽  
Vol 289 (3) ◽  
pp. 703-708 ◽  
Author(s):  
S Echegoyen ◽  
E B Oliva ◽  
J Sepulveda ◽  
J C Díaz-Zagoya ◽  
M T Espinosa-García ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Atpase Activity ◽  
Succinate Dehydrogenase ◽  
Outer Membrane ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Inner Membrane ◽  
Ultrastructural Morphology ◽  
Mitochondrial Inner Membrane

The effect of cholesterol incorporation on some functions of the mitochondrial inner membrane and on the morphology of rat liver mitochondria was studied. Basal ATPase and succinate dehydrogenase activities remained unchanged after cholesterol was incorporated into the mitochondria; however, uncoupled ATPase activity was partially inhibited. The presence of several substrates and inhibitors did not change the amount of cholesterol incorporated, which was localized mostly in the outer membrane. Electron-microscope observations revealed the presence of vesicles between the outer and inner membranes; these vesicles increased in number with the amount of cholesterol incorporated. The data suggest that cholesterol induces the formation of vesicles from the outer membrane, and modifies the activity of stimulated ATPase.

scholarly journals ‘Pore’ formation is not required for the hydroperoxide-induced Ca2+ release from rat liver mitochondria

1992 ◽  
Vol 285 (1) ◽  
pp. 65-69 ◽  
Author(s):  
J Schlegel ◽  
M Schweizer ◽  
C Richter
Keyword(s):  
Rat Liver ◽  
Pore Formation ◽  
Permeability Transition Pore ◽  
Permeability Transition ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Specific Permeability ◽  
Specific Pathway

It has recently been suggested by several investigators that the hydroperoxide- and phosphate-induced Ca2+ release from mitochondria occurs through a non-specific ‘pore’ formed in the mitochondrial inner membrane. The aim of the present study was to investigate whether ‘pore’ formation actually is required for Ca2+ release. We find that the t-butyl hydroperoxide (tbh)-induced release is not accompanied by stimulation of sucrose entry into, K+ release from, and swelling of mitochondria provided re-uptake of the released Ca2+ (‘Ca2+ cycling’) is prevented. We conclude that (i) the tbh-induced Ca2+ release from rat liver mitochondria does not require ‘pore’ formation in the mitochondrial inner membrane, (ii) this release occurs via a specific pathway from intact mitochondria, and (iii) a non-specific permeability transition (‘pore’ formation) is likely to be secondary to Ca2+ cycling by mitochondria.

scholarly journals The action of digitonin on rat liver mitochondria. Electron microscopy

1968 ◽  
Vol 107 (3) ◽  
pp. 377-380 ◽  
Author(s):  
Donald J. Morton ◽  
Charles Hoppel ◽  
Cecil Cooper
Keyword(s):  
Outer Membrane ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Inner Membrane ◽  
Lamellar Structures ◽  
Membrane Complex ◽  
Condensed Form ◽  
Intact Mitochondrion ◽  
Inner Membrane Complex

1. Rat liver mitochondria were examined in the electron microscope by using negative staining in the presence of 0·3m-sucrose. The intact outer membrane does not appear to be freely permeable to the stain. Where the stain penetrated through a tear it was seen that the inner membrane had randomly oriented grooves, many of which contained round structures varying between 200 and 900å in diameter. Laminar structures containing two to five layers of approx. 50å each were found at the periphery. 2. When the outer membrane was removed by treating the mitochondria with digitonin several types of inner-membrane complexes were formed and they showed a general correlation with those observed in sectioned samples of the same preparations. The main types were: (a) a condensed form looking very much like the intact mitochondrion without the outer membrane (this still showed the grooves, some of which contained the round structures, and the laminar whirls at the edges); (b) a more transparent form containing tubules of uniform width and various lengths (some of these appeared to terminate in a hole at the surface of the inner membrane); (c) a large torn sac, probably the inner membrane, containing some tubules and vesicles. 3. When the inner-membrane complex was further treated with digitonin it was disrupted and the resulting material consisted of pieces of membrane, doughnut-shaped units and lamellar structures. Most of these pieces varied in size between 500 and 1000å.

scholarly journals The action of digitonin on rat liver mitochondria. Phospholipid content

1968 ◽  
Vol 107 (3) ◽  
pp. 381-385 ◽  
Author(s):  
H. A. I. Newman ◽  
Stanley E. Gordesky ◽  
Charles Hoppel ◽  
Cecil Cooper
Keyword(s):  
Fatty Acid ◽  
Outer Membrane ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Phospholipid Content ◽  
Rat Liver Mitochondria ◽  
Inner Membrane ◽  
Membrane Complex ◽  
Inner Membrane Complex ◽  
Layer Chromatography

1. The amount and types of phospholipid and the fatty acid composition of the various phospholipids were examined in intact rat liver mitochondria, in mitochondria devoid of their outer membrane (preparation A) and in very small pieces derived from the disruption of the inner-membrane complexes (preparation B). The latter two preparations were obtained by digitonin treatment and carry out oxidative phosphorylation. 2. The ratio μg.atoms of phospholipid P/mg. of protein was 0·163 for intact mitochondria, decreased to 0·118 on removal of the outer membrane and increased markedly to 0·292 on disruption of the inner-membrane complex. 3. Examination of the various types of phospholipid present showed that the molar proportions cardiolipin:phosphatidylcholine:phosphatidylethanolamine were approx. 1:6:6 for intact mitochondria and 1:3:3 for preparations A and B. 4. There was a correlation between the recovery of cardiolipin and adenosine triphosphatase activity in the conversion of intact mitochondria into preparations A and B. 5. The fatty acid contents of the various types of phospholipid purified by thin-layer chromatography were identical in all three preparations. Our results show a considerably higher content of arachidonic acid and lower content of oleic acid for phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol than have previously been reported for mitochondrial phospholipids.

scholarly journals Discrimination of distinct proteinases at the four structural levels of rat liver mitochondria

1986 ◽  
Vol 233 (1) ◽  
pp. 283-286 ◽  
Author(s):  
M C Duque-Magalhães ◽  
P Régnier
Keyword(s):  
Outer Membrane ◽  
Rat Liver ◽  
Degradation Products ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Intermembrane Space ◽  
Peptidase Activity ◽  
Inner Membrane ◽  
Mitochondrial Fractions ◽  
The Matrix

Rat liver mitochondrial fractions corresponding to four morphological structures (matrix, inner membrane, intermembrane space and outer membrane) contain proteinases that cleave casein components at different rates. Proteinases of the intermembrane space preferentially cleave kappa-casein, whereas the proteinases of the outer membrane, inner membrane and matrix fractions degrade alpha S1-casein more rapidly. Electrophoretic separation of the degradation products of alpha S1-casein and kappa-casein in polyacrylamide gels shows that different polypeptides are produced when the substrate is degraded by the matrix, by both membranes and by the intermembrane-space fraction. Some of the degradation products resulting from incubation of the caseins with the mitochondrial fractions are probably the result of digestion by contaminating lysosomal proteinase(s). The matrix has a high peptidase activity, since glucagon, a small peptide, is very rapidly degraded by this fraction. These observations strongly suggest that distinct proteinases, with different specificities, are associated respectively with the intermembrane space and with both membrane fractions.

scholarly journals d-Lactate transport and metabolism in rat liver mitochondria

2002 ◽  
Vol 365 (2) ◽  
pp. 391-403 ◽  
Author(s):  
Lidia de BARI ◽  
Anna ATLANTE ◽  
Nicoletta GUARAGNELLA ◽  
Giovanni PRINCIPATO ◽  
Salvatore PASSARELLA
Keyword(s):  
Lactate Dehydrogenase ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Lactate Metabolism ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
The Matrix ◽  
Inside Out

In the present study we investigated whether isolated rat liver mitochondria can take up and metabolize d-lactate. We found the following: (1) externally added d-lactate causes oxygen uptake by mitochondria [P/O ratio (the ratio of mol of ATP synthesized to mol of oxygen atoms reduced to water during oxidative phosphorylation) = 2] and membrane potential (Δψ) generation in processes that are rotenone-insensitive, but inhibited by antimycin A and cyanide, and proton release from coupled mitochondria inhibited by α-cyanocinnamate, but not by phenylsuccinate; (2) the activity of the putative flavoprotein (d-lactate dehydrogenase) was detected in inside-out submitochondrial particles, but not in mitochondria and mitoplasts, as it is localized in the matrix phase of the mitochondrial inner membrane; (3) three novel separate translocators exist to mediate d-lactate traffic across the mitochondrial inner membrane: the d-lactate/H+ symporter, which was investigated by measuring fluorimetrically the rate of endogenous flavin reduction, the d-lactate/oxoacid antiporter (which mediates both the d-lactate/pyruvate and d-lactate/oxaloacetate exchanges) and d-lactate/malate antiporter studied by monitoring photometrically the appearance of the d-lactate counteranions outside mitochondria. The d-lactate translocators, in the light of their different inhibition profiles separate from the monocarboxylate carrier, were found to differ from each other in the Vmax values and in the inhibition and pH profiles and were shown to regulate mitochondrial d-lactate metabolism in vitro. The d-lactate translocators and the d-lactate dehydrogenase could account for the removal of the toxic methylglyoxal from cytosol, as well as for d-lactate-dependent gluconeogenesis.

scholarly journals THE MORPHOLOGY OF THE SWELLING PROCESS IN RAT LIVER MITOCHONDRIA

1971 ◽  
Vol 48 (2) ◽  
pp. 291-302 ◽  
Author(s):  
D. R. Myron ◽  
J. L. Connelly
Keyword(s):  
Electron Microscope ◽  
Outer Membrane ◽  
Rat Liver ◽  
Conformational Changes ◽  
Large Amplitude ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
The Matrix

Through the use of combined spectrophotometric and electron microscope techniques, large amplitude swelling of rat liver mitochondria has been described as an ordered sequence of ultrastructural transitions. Prior to the actual swelling, mitochondria undergo two major conformational changes: condensed to twisted form and twisted to orthodox form. This sequence is independent of (a) the nature of swelling agents and (b) the time of onset of swelling. Agents that delay the onset of swelling act to increase the duration of the twisted conformation. Agents that prevent extensive swelling hold mitochondria in intermediate conformations. Gross swelling, immediately preceded by a decrease in electron opacity of the matrix, involves the rupture of the outer membrane and expansion of the inner compartment of the mitochondrion.

scholarly journals Biochemical effects of the hypoglycaemic compound diphenyleneiodonium. Catalysis of anion–hydroxyl ion exchange across the inner membrane of rat liver mitochondria and effects on oxygen uptake

1972 ◽  
Vol 129 (1) ◽  
pp. 39-54 ◽  
Author(s):  
P. C. Holland ◽  
H. S. A. Sherratt
Keyword(s):  
Rat Liver ◽  
Indirect Evidence ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Hydroxyl Ion ◽  
Respiration Of Mitochondria ◽  
Free Media ◽  
Stimulation Of

1. The hypoglycaemic compound diphenyleneiodonium causes rapid and extensive swelling of rat liver mitochondria suspended in 150mm-NH4Cl, and in 150mm-KCl in the presence of 2,4-dinitrophenol and valinomycin. This indicates that diphenyleneiodonium catalyses a compulsory exchange of OH-for Cl-across the mitochondrial inner membrane. Br-and SCN-were the only other anions found whose exchange for OH-is catalysed by diphenyleneiodonium. 2. Diphenyleneiodonium inhibited state 3 respiration of mitochondria and slightly stimulated state 4 respiration with succinate or glutamate as substrate in a standard Cl--containing medium. 3. Diphenyleneiodonium did not inhibit state 3 respiration significantly in two Cl--free media (based on glycerol 2-phosphate or sucrose) but caused some stimulation of state 4. 4. In Cl--containing medium diphenyleneiodonium only slightly inhibited the 2,4-dinitrophenol-stimulated adenosine triphosphatase and it had little effect in the absence of Cl-. 5. The inhibition of respiration in the presence of Cl-is dependent on the Cl-–OH-exchange. 2,4-Dichlorodiphenyleneiodonium is ten times as active as diphenyleneiodonium both in causing swelling of mitochondria suspended in 150mm-NH4Cl and in inhibiting state 3 respiration in Cl--containing medium. Indirect evidence suggests that the Cl-–OH-exchange impairs the rate of uptake of substrate anions. 6. It is proposed that stimulation of state 4 respiration in the absence of Cl-depends, at least in part, on an electrogenic uptake of diphenyleneiodonium cations. 7. Tripropyl-lead acetate, methylmercuric iodide and nine substituted diphenyleneiodonium derivatives also catalyse Cl-–OH-exchange across the mitochondrial membrane. 8. Diphenyleneiodonium is compared with the trialkyltin compounds, which are also known to mediate Cl-–OH-exchange and which have in addition strong oligomycin-like effects on respiration. It is concluded that diphenyleneiodonium is specific for catalysing anion–OH-exchange and will be a useful reagent for investigating membrane-dependent systems.

scholarly journals Partial purification and properties of rat liver mitochondrial polynucleotide phosphorylase

1972 ◽  
Vol 130 (2) ◽  
pp. 343-353 ◽  
Author(s):  
Y. P. See ◽  
P. S. Fitt
Keyword(s):  
Rat Liver ◽  
Kinase Activity ◽  
Liver Mitochondria ◽  
Partial Purification ◽  
Rat Liver Mitochondria ◽  
Polynucleotide Phosphorylase ◽  
Inner Membrane ◽  
Mitochondrial Inner Membrane ◽  
Purification And Properties ◽  
Exchange Activity

1. Polynucleotide phosphorylase was partially purified from the inner membrane of rat liver mitochondria. 2. The partially purified particulate enzyme catalyses phosphorolysis of poly(A), poly(C), poly(U) and RNA to nucleoside diphosphates. 3. It is devoid of nucleoside diphosphate-polymerization activity. 4. Variable amounts of ADP/Pi-exchange activity are associated with the polynucleotide phosphorylase and are probably due to a different enzyme. 5. ADP is the preferred substrate for exchange, and little or no reaction occurs with other nucleoside diphosphates, but ATP/Pi-exchange takes place at one-third the rate observed with ADP. 6. The partially purified enzyme is free from the phosphatases found in the crude mitochondrial inner membrane, but is associated with an endonuclease activity and some adenylate kinase activity; no cytidylate kinase activity analogous to the latter was detectable.

Electron Microscopic Tomography of Cellular Organelles: Chemical Fixation Vs. Cryo-Substitution of Rat-Liver Mitochondria

1998 ◽  
Vol 4 (S2) ◽  
pp. 430-431
Author(s):  
C.A. Mannella ◽  
K. Buttle ◽  
K. Tessitore ◽  
B.K. Rath ◽  
C. Hsieh ◽  
...  
Keyword(s):  
Rat Liver ◽  
3D Structure ◽  
Design Feature ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Electron Microscopic ◽  
Inner Membrane ◽  
Low Contrast ◽  
Mitochondrial Inner Membrane ◽  
Cellular Organelles

Electron microscopic tomography is proving to be a valuable tool for investigating the 3D structure and organization of cellular organelles. Important progress is being made in the application of the technique to frozen-hydrated material, but it is likely that success with thick specimens will be limited by the low contrast and beam sensitivity of naked biological material. Thus, optimizing procedures for fixing, embedding, staining, and selectively labelling cells for 3D electron microscopy remains a priority.Tomography of chemically fixed and plastic-embedded rat-liver tissue and isolated mitochondria has shown that the cristae (the invaginations of the mitochondrial inner membrane) are pleiomorphic and connected to each other and to the surface of the inner membrane by tubular regions 30-40 nm in diameter. This basic design feature has important implications for the microcompartmentation of ions and molecules within this organelle.

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