scholarly journals Levels of carbamoyl phosphate synthetase I in livers of young and old rats assessed by activity and immunoassays and by electron microscopic immunogold procedures.

1990 ◽  
Vol 38 (3) ◽  
pp. 371-376 ◽  
Author(s):  
A Martinez-Ramon ◽  
E Knecht ◽  
V Rubio ◽  
S Grisolia
Keyword(s):  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Matrix ◽  
Carbamoyl Phosphate Synthetase ◽  
Enzyme Protein ◽  
Carbamoyl Phosphate ◽  
Electron Microscopic ◽  
Liver Functions ◽  
Old Rats ◽  
Liver Homogenates

Carbamoyl phosphate synthetase I, the most abundant protein of rat liver mitochondria, plays a key role in synthesis of urea. Because aging affects some liver functions, and because there is no information on the levels of carbamoyl phosphate synthetase I during aging, we assayed the activity of this enzyme and determined immunologically the level of carbamoyl phosphate synthetase I in liver homogenates from young (4 months) and old (18 or 26 months) rats. In addition, we used electron microscopic immunogold procedures to locate and measure the amount of the enzyme in the mitochondrial matrix. There is no significant change in enzyme activity or enzyme protein content with age, although there is a higher concentration of the enzyme in the mitochondria (c. 1.5 times greater) from old rats, which is compensated by a decrease in the fractional volume of the mitochondrial compartment during aging.

scholarly journals Properties of carbamoyl-phosphate synthetase (ammonia) in rat-liver mitochondria made permeable with toluene

1983 ◽  
Vol 135 (2) ◽  
pp. 251-258 ◽  
Author(s):  
Cor LOF ◽  
Martine COHEN ◽  
Leo P. VERMEULEN ◽  
Carlo W. T. ROERMUND ◽  
Ron J. A. WANDERS ◽  
...  
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Carbamoyl Phosphate Synthetase ◽  
Carbamoyl Phosphate

scholarly journals Electron microscopic localization of glutamate dehydrogenase in rat liver mitochondria by an immunogold procedure and monoclonal and polyclonal antibodies.

1986 ◽  
Vol 34 (7) ◽  
pp. 913-922 ◽  
Author(s):  
E Knecht ◽  
A Martinez-Ramon ◽  
S Grisolia
Keyword(s):  
Glutamate Dehydrogenase ◽  
Rat Liver ◽  
Polyclonal Antibodies ◽  
Protein A ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Electron Microscopic ◽  
Cross Sectional ◽  
Gold Particles ◽  
Parenchymal Cells

Glutamate dehydrogenase (GDH) was localized in rat liver by indirect electron microscopic immunogold, using different sizes of gold particles and monoclonal and polyclonal antibodies. Using the protein A-gold technique in double immunocytochemical experiments, both antibodies, at their optimal dilutions, gave similar results. A novel assessment of the distribution of GDH was made by measurements of the number of gold particles per square micrometer of cross-sectional images of individual mitochondria. The data indicate intracellular homogeneity among mitochondria in individual parenchymal cells. The enzyme is almost absent in non-parenchymal cells. Finally, GDH was found mainly in association with the mitochondrial inner membrane.

scholarly journals MORPHOLOGY AND ATP-ASE OF ISOLATED MITOCHONDRIA

1955 ◽  
Vol 1 (2) ◽  
pp. 127-138 ◽  
Author(s):  
Robert F. Witter ◽  
Michael L. Watson ◽  
Mary A. Cottone
Keyword(s):  
Electron Microscope ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Substantial Part ◽  
Mitochondrial Matrix ◽  
Isolated Mitochondria ◽  
The Matrix ◽  
First Time ◽  
Methods Of Isolation

Changes in the morphology of rat liver mitochondria brought about by different methods of isolation and the concomitant changes in ATP-ase activity were studied. The morphology was investigated with the electron microscope. It was found that the ATP-ase activity of the isolated mitochondria cannot be readily correlated with the morphology of the mitochondria. The ATP-ase found in these preparations was latent, resembling the enzyme described in mitochondria prepared in 0.25 M sucrose. In confirmation of earlier results the use of 0.88 M sucrose yielded preparations with a higher initial ATP-ase than did other methods. Preparation in 0.25 M sucrose resulted in round, swollen mitochondria of which 30 to 40 per cent appeared to have lost a substantial part of the mitochondrial matrix. Preparations in 0.44 to 0.88 M sucrose contained mainly rod-shaped mitochondria plus a small amount of another type of swollen mitochondria. The matrix of mitochondria isolated in 0.88 M sucrose was highly condensed. By the use of 0.44 M sucrose adjusted to pH 6.2 with citric acid, it was possible to isolate, for the first time, mitochondria closely resembling those in situ and containing latent ATP-ase.

scholarly journals EFFECT OF ACTIVE ACCUMULATION OF CALCIUM AND PHOSPHATE IONS ON THE STRUCTURE OF RAT LIVER MITOCHONDRIA

1964 ◽  
Vol 23 (1) ◽  
pp. 21-38 ◽  
Author(s):  
John W. Greenawalt ◽  
Carlo S. Rossi ◽  
Albert L. Lehninger
Keyword(s):  
Specific Gravity ◽  
Rat Liver ◽  
Cesium Chloride ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Electron Microscopic ◽  
Dense Granules ◽  
Phosphate Ions ◽  
Microscopic Studies

Rat liver mitochondria allowed to accumulate maximal amounts of Ca++ and HPO4= ions from the suspending medium in vitro during respiration have a considerably higher specific gravity than normal mitochondria and may be easily separated from the latter by isopycnic centrifugation in density gradients of sucrose or cesium chloride. When the mitochondria are allowed to accumulate less than maximal amounts of Ca++ and HPO4= from the medium, they have intermediate specific gravities which are roughly proportional to their content of calcium phosphate. Maximally "loaded" mitochondria are relatively homogeneous with respect to specific gravity. Correlated biochemical and electron microscopic studies show that Ca++-loaded mitochondria contain numerous dense granules, of which some 85 per cent are over 500 A in diameter. These granules are electron-opaque not only following fixation and staining with heavy metal reagents, but also following fixation with formaldehyde, demonstrating that the characteristic granules in Ca++-loaded mitochondria have intrinsic electron-opacity. The dense granules are almost always located within the inner compartment of the mitochondria and not in the space between the inner and outer membranes. They are frequently located at or near the cristae and they often show electron-transparent "cores." Such granules appear to be made up of clusters of smaller dense particles, but preliminary x-ray diffraction analysis and electron diffraction studies have revealed no evidence of crystallinity in the deposits. The electron-opaque granules decrease in number when the Ca++-loaded mitochondria are incubated with 2,4-dinitrophenol; simultaneously there is discharge of Ca++ and phosphate from the mitochondria into the medium.

Electron microscopic tomography of rat-liver mitochondria and their interactions with the endoplasmic reticulum

BioFactors ◽  
1998 ◽  
Vol 8 (3-4) ◽  
pp. 225-228 ◽  
Author(s):  
Carmen A. Mannella ◽  
Karolyn Buttle ◽  
Bimal K. Rath ◽  
M. Marko
Keyword(s):  
Endoplasmic Reticulum ◽  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Electron Microscopic

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

1987 ◽  
Vol 245 (1) ◽  
pp. 217-222 ◽  
Author(s):  
J D Johnston ◽  
M D Brand
Keyword(s):  
Respiration Rate ◽  
Rat Liver ◽  
Oxidative Metabolism ◽  
Mitochondrial Respiration ◽  
Liver Mitochondria ◽  
Ruthenium Red ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Matrix ◽  
Stimulation Of

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.

scholarly journals Inhibition in vitro of acyl-CoA dehydrogenases by 2-mercaptoacetate in rat liver mitochondria

1983 ◽  
Vol 215 (3) ◽  
pp. 457-464 ◽  
Author(s):  
F Bauché ◽  
D Sabourault ◽  
Y Giudicelli ◽  
J Nordmann ◽  
R Nordmann
Keyword(s):  
Rat Liver ◽  
Conformational Changes ◽  
Reaction Medium ◽  
Liver Mitochondria ◽  
Fatty Acyl ◽  
Rat Liver Mitochondria ◽  
Mitochondrial Matrix ◽  
Main Effect ◽  
Acyl Coa Dehydrogenases

In rat liver hypo-osmotically treated mitochondria, 2-mercaptoacetate inhibits respiration induced by palmitoyl-CoA, octanoate or butyryl-CoA only when the reaction medium is supplemented with ATP. Under this condition, NADH-stimulated respiration is not affected. In liver mitochondrial matrix, the presence of ATP is also required to observe a 2-mercaptoacetate-induced inhibition of acyl-CoA dehydrogenases tested with palmitoyl-CoA, butyryl-CoA or isovaleryl-CoA as substrate. As the oxidation of these substrates is also inhibited by the incubation medium resulting from the reaction of 2-mercaptoacetate with acetyl-CoA synthase, with conditions under which 2-mercaptoacetate has no effect, 2-mercaptoacetyl-CoA seems to be the likely inhibitory metabolite responsible for the effects of 2-mercaptoacetate. Kinetic experiments show that the main effect of the 2-mercaptoacetate-active metabolite is to decrease the affinities of fatty acyl-CoA dehydrogenases towards palmitoyl-CoA or butyryl-CoA and of isovaleryl-CoA dehydrogenase towards isovaleryl-CoA. Addition of N-ethylmaleimide to mitochondrial matrix pre-exposed to 2-mercaptoacetate results in the immediate reversion of the inhibitions of palmitoyl-CoA and isovaleryl-CoA dehydrogenations and in a delayed reversion of butyryl-CoA dehydrogenation. These results led us to conclude that (i) the ATP-dependent conversion of 2-mercaptoacetate into an inhibitory metabolite takes place in the liver mitochondrial matrix and (ii) the three fatty acyl-CoA dehydrogenases and isovaleryl-CoA dehydrogenase are mainly competitively inhibited by this compound. Finally, the present study also suggests that the inhibitory metabolite of 2-mercaptoacetate may bind non-specifically to, or induce conformational changes at, the acyl-CoA binding sites of these dehydrogenases.

Electron Microscopic Tomography of Whole, Frozen-Hydrated Rat-Liver Mitochondria at 400 kv

1999 ◽  
Vol 5 (S2) ◽  
pp. 416-417
Author(s):  
C.A. Mannella ◽  
C.-E Hsieh ◽  
M. Marko
Keyword(s):  
Rat Liver ◽  
Liver Mitochondria ◽  
Rat Liver Mitochondria ◽  
Peripheral Compartment ◽  
Collection System ◽  
Electron Microscopic ◽  
Automated Data Collection ◽  
Outer Membranes ◽  
Mitochondrial Inner Membrane ◽  
Structural Preservation

Electron microscopic tomography is providing important new insights about the internal structure of the mitochondrion. In particular, the infoldings of the mitochondrial inner membrane (cristae), which are usually rendered as lamelliform baffles, are revealed to have considerable tubular nature. Rather than opening wide to the peripheral compartment (between the inner and outer membranes), the cristae connect to the outside and to each other through narrow (20-30 nm) tubular segments, which can be hundreds of nanometers long. This suggests that diffusion of ions, metabolites and proteins between the intracristal and intermembrane spaces may be restricted.The earlier tomographic reconstructions were done on conventionally prepared, plastic-embedded specimens, which raises the usual concerns about structural preservation. More recently, we have undertaken tomography of isolated rat-liver mitochondria that have been embedded in vitreous ice (by plunge-freezing in iso-osmotic buffer without chemical fixatives or stains). These frozen hydrated specimens are imaged with a JEOL 4000FX equipped with a Gatan cryo-transfer holder and a Tietz automated data collection system, with a Ik × Ik CCD. For 3D reconstructions, images were recorded at a dose of 5 e−Å2 at 2° increments over the range +/− 60°.

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