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PubMed1992

Mechanism of citrinin-induced dysfunction of mitochondria. I. Effects on respiration, enzyme activities and membrane potential of renal cortical mitochondria.

Citrinin depresses the phosphorylation efficiency of rat renal cortical mitochondria, as inferred from the decrease of the respiratory control coefficient (RC) and ADP/O ratios. The transmembrane potential (delta psi) developed by energized mitochondria and the depolarization upon ADP addition are also decreased. Citrinin (1.0 mM) inhibits almost all enzymes linked to the respiratory chain and increases the activity of succinate cytochrome c reductase and succinate oxidase (coupled). Malate and glutamate dehydrogenases are also inhibited. The inhibitory action of citrinin on phosphorylation efficiency could be related to the following findings: the effect on complex I; the action on the ATP synthetase complex; the partial inhibition of the transmembrane potential.

Animals↗

PubMed1977

Investigations on the turnover of adrenocortical mitochondria. IX. A stereological study of the effects of chronic treatment with acth on the size and number of mitochondria from adult human adrenocortical cells cultured in vitro.

The effects of ACTH on the mitochondria of adult human adrenocortical cells cultured in vitro were investigated by electron microscopic and stereological methods. It was found that ACTH induces increase in the volume of the mitochondrial compartment, which is due to both a hypertrophy and an increase in number of the organelles. The hypothesis that ACTH controls the growth and proliferation of human adrenocortical mitochondria is discussed.

Adrenal Glands↗

PubMed1980

Investigations on the turnover of adrenocortical mitochondria. XV. A stereological study of the effect of chronic treatment with angiotensin II on the size and number of the mitochondria in the zona glomerulosa of the rat.

The effects of a chronic treatment with angiotensin II (up to 15 consecutive days) on the mitochondria of the rat zona glomerulosa cells were investigated by electron microscopic and stereological methods. Angiotensin induced a significant increase in the volume of the mitochondrial compartment. Up to the 3rd day of treatment this was due only to the hypertrophy of the organelles, and from the 3rd to the 15th day exclusively to mitochondrial proliferation. The hypothesis that angiotensin controls the growth and proliferation of rat zona glomerulosa mitochondria is discussed.

Adrenal Cortex↗

PubMed1999

Immunocytochemical detection of mitochondria-rich cells in the brood pouch epithelium of the pipefish, Syngnathus schlegeli: structural comparison with mitochondria-rich cells in the gills and larval epidermis.

The brood pouch of the male pipefish (Syngnathus schlegeli) is a ventral organ located on the tail, with the anterior region closely associated with the genital pore. The embryos in the pouch are attached to highly vascularized placenta-like tissue which seals the pouch folds from inside during incubation. The epithelium of the placenta-like tissue consists of mitochondria-rich cells (MRCs) and pavement cells. Differences in MRC morphology in the brood pouch epithelium, the gills and the larval epidermis of the pipefish were examined by light and electron microscopy. Transmission electron microscopy revealed that the MRCs in the brood pouch and the gills shared common characteristics: the presence of numerous mitochondria packed among a well-developed tubular system and the close association of the basal parts with the capillaries running underneath the epithelia. The size of the apical opening of the elongate, flask-shaped brood pouch MRC was about one-tenth that of the apical pit of the gill MRC. The gill and larval epidermal MRCs formed a multicellular complex, in contrast to solitary brood pouch MRCs. The brood pouch MRCs were intensively stained by immunocytochemistry with an antiserum specific for Na+,K+-ATPase. The Na+ concentrations in the brood pouch were maintained near those in the serum rather than seawater during incubation. We conclude that the brood pouch MRCs function as an ion-transporting cell, absorbing ions from the brood pouch lumen, perhaps to protect the embryos from the hyperosmotic environment.

Animals↗

PubMed1984

Dielectric analysis of mitochondria isolated from rat liver. II. Intact mitochondria as simulated by a double-shell model.

The dielectric dispersion of isolated intact mitochondria in suspension has been measured between 10 kHz and 500 MHz. In isotonic KCl media at 4 degrees C, the mitochondria maintained their characteristic 'double membrane' structure as examined by electron microscopy, and the observed dispersion curves were successfully simulated in terms of a superposition of two sub-dispersions having different characteristic frequencies and different permittivity magnitudes. Taking these observations into account we analyzed the dispersion data on the basis of a 'double-shell' model in which two concentric shells are meant to represent the mitochondrial outer and inner membranes. The analyses by a computerized curve-fitting method revealed that: (i) electric capacities for the outer and the inner membrane are 1.7 and 0.5 microF/cm2, respectively, (ii) relative permittivity for the inner compartment (or the equivalent homogeneous matrical space) = 50-60, (iii) outer compartment-to-external conductivity ratio = 0.4-0.6, and (iv) inner compartment-to-external conductivity ratio = 0.14. The implications of these parameter values are discussed with due attention paid to the limitations inherent in our 'double-shell' model approach.

Animals↗

PubMed1991

Characterization of pore-forming activity in liver mitochondria from Anguilla anguilla. Two porins in mitochondria?

A fast purification procedure for the isolation and purification of eukaryotic porin (De Pinto et al., (1987) Biochim. Biophys. Acta 905, 499-502) was applied to liver mitochondria of the fish Anguilla anguilla. A protein preparation was obtained which formed slightly anionically selective pores in reconstitution experiments with lipid bilayer membranes. The distribution of single-channel conductances had two maxima of 2.4 nS and 4.0 nS in 1 M KCl. Sodium dodecylsulfate electrophoretograms of the protein preparation showed the presence of two bands of very similar electrophoretic mobility (32 and 32.5 kDa). Both bands cross-reacted with antibodies raised against purified bovine heart porin and with antibodies raised against the 19 amino acids N-terminal end of human porin. No cross-reactivity was observed with antibodies against yeast porin. The peptide maps of the two bands showed slight differences. The possibility of the presence of two different porins in liver mitochondria of Anguilla anguilla is discussed. An extensive immunological comparison of different mitochondrial porins is presented.

Anguilla↗

PubMed1977

Investigations on the turnover of adrenocortical mitochondria. XI. Effects of dexamethasone on the half-life of mitochondria from the rat zona fasciculata.

The effects of dexamethasone on the half-life of rat adrenocortical mitochondria were investigated by high resolution autoradiography and liquid scintillation spectroscopy. According to the method employed, the half-life averaged 11.27 and 10.46 days. Dexamethasone was found to decrease significantly this parameter (to about 5 days). Since dexamethasone-treated rats can be regarded as pharmacologically hypophysectomized animals, the data indicates that ACTH is involved in the maintenance of the half-life of adrenocortical mitochondria.

Adrenal Cortex↗

PubMed1973

Biogenesis of mitochondria. A requirement for mitochondrial protein synthesis for the formation of a normal adenine nucleotide transporter in yeast mitochondria.

1. Parameters of ATP uptake by fully functional Saccharomyces cerevisiae mitochondria, including kinetic constants, binding constants and sensitivity to atractylate, closely resemble those of mammalian mitochondria. Scatchard plots of atractylate-sensitive adenine nucleotide binding indicate two distinct sites of high affinity (binding constant, K(D)'=1mum), and low affinity (binding constant, K(D)''=20mum) in the ratio 1:3. Uptake has high Arrhenius activation energies (+35 and +57kJ/mol), above and below a transition temperature of 11 degrees C. Atractylate-insensitive ATP uptake is apparently not saturable and has a low Arrhenius activation energy (6kJ/mol), suggesting a non-specific binding process. 2. Kinetic and binding constants for ATP uptake are not significantly changed in catabolite-repressed or anaerobic mitochondrial structures. 3. Inhibition of the mitochondrial protein-synthesizing system by growth of cells in the presence of erythromycin, or loss of mitochondrial DNA by mutation profoundly alters the adenine nucleotide transporter. ATP uptake becomes completely insensitive to atractylate, and the high-affinity binding site is lost. However, the adenine nucleotide transporter does not appear to be totally eliminated, as a moderate amount of saturable low-affinity ATP binding remains. 4. It is concluded that products of the mitochondrial protein-synthesizing system, probably coded by mitochondrial DNA, are required for the normal function of the adenine nucleotide transporter.

Adenine Nucleotides↗

PubMed2005

The anti-psoriatic drug anthralin accumulates in keratinocyte mitochondria, dissipates mitochondrial membrane potential, and induces apoptosis through a pathway dependent on respiratory competent mitochondria.

Anthralin is a potent topical drug, inducing clearance of psoriatic plaques. Anthralin disrupts mitochondrial function and structure, but its mechanism of action remains undefined. This study aimed to determine whether anthralin induced keratinocyte apoptosis as well as to investigate molecular mechanisms and the role of mitochondria. We studied human keratinocytes and human 143B rho(0) cells, which lack mitochondrial DNA and a functional respiratory chain. We show that anthralin disrupts mitochondrial membrane potential (DeltaPsim) and causes endogenous cytochrome c release, resulting in the activation of caspase-3 and characteristic morphological changes of apoptosis. Disruption of DeltaPsim and cytochrome c release were independent of mitochondrial permeability transition or caspase activation. Human 143B rho(0) cells were resistant to anthralin-induced cell death, disruption of DeltaPsim, and cytochrome c release compared with the isogenic 143B rho+ cell line. Using the intrinsic fluorescence of anthralin, rapid accumulation within mitochondria was observed independent of DeltaPsim. Using assays that measure individual respiratory chain complexes, we show that anthralin specifically interacts with ubiquinone pool. These data indicate that anthralin induces apoptosis through a novel mitochondrial pathway dependent on oxidative respiration and involving electron transfer with the ubiquinone pool. These studies identify keratinocyte apoptosis as a potentially important mechanism involved in the clearance of psoriasis.

Anthralin↗

PubMed1969

The respiratory chain of plant mitochondria. I. Electron transport between succinate and oxygen in skunk cabbage mitochondria.

The kinetics of oxidation of ubiquinone, flavoprotein, cytochrome c, and the cytochrome b complex in skunk cabbage (Symplocarpus foetidus) mitochondria made anaerobic with succinate have been measured spectrophotometrically and fluorimetrically in the absence of respiratory inhibitor and in the presence of cyanide or antimycin A. No component identifiable by these means was oxidized rapidly enough in the presence of one or the other inhibitor to qualify for the role of alternate oxidase. Cycles of oxidation and rereduction of flavoprotein and ubiquinone obtained by injecting 12 mum oxygen into the anaerobic mitochondrial suspension were kinetically indistinguishable in the presence of cyanide or antimycin A, implying that these 2 components are part of a respiratory pathway between succinate and oxygen which does not involve the cytochromes and does involve a cyanide-insensitive alternate oxidase. The cytochrome b complex shows biphasic oxidation kinetics with half times of 0.018 sec and 0.4 sec in the absence of inhibitor, which increase to 0.2 sec and 1 sec in the presence of cyanide. In the presence of antimycin A, the oxidation of the cytochrome b complex shows an induction period of 1 sec and a half-time of 3.5 sec. A split respiratory chain with 2 terminal oxidases and a branch point between the cytochromes and flavoprotein and ubiquinone is proposed for these mitochondria.

Electron Transport↗

PubMed1979

Fractionation of human liver mitochondria: enzymic and morphological characterization of the inner and outer membranes as compared to rat liver mitochondria.

The fractionation of human liver mitochondria into inner membrane, outer membrane and matrix material is reported. Compared with rat, human liver mitochondria are more fragile. Fractionation can be achieved in only 2 steps, a digitonin treatment for removal of the outer membrane and centrifugation of the inner membrane plus matrix particles through a linear sucrose gradient resulting in purified inner membranes and matrix.

Animals↗

PubMed1995

Cu-pyruvaldehyde-bis(N4-methylthiosemicarbazone) (Cu-PTSM), a metal complex with selective NADH-dependent reduction by complex I in brain mitochondria: a potential radiopharmaceutical for mitochondria-functional imaging with positron emission tomography (PET).

The reductive retention mechanism of copper(II)-pyruvaldehyde-bis (N4-methylthiosemicarbazone) (Cu-PTSM), a generator-produced positron-emitting 62Cu-labeled radiopharmaceutical, was studied with non-radioactive and radioactive copper. Changes in the chemical form of Cu-PTSM were detected by electron spin resonance spectrometry (ESR) with cold copper. The effects of electron transport chain inhibitors on the reduction of Cu-PTSM were also examined. Rotenone and antimycin A activated the reduction of Cu-PTSM in the brain mitochondria by 1.6- and 1.4-fold, respectively, compared with untreated controls, while thenoyltrifluoroacetone (TTFA) had no effect on the reduction. These results were confirmed with radioactive copper. Furthermore, this reduction of Cu-PTSM was dependent on the protein concentration of mouse brain submitochondrial particle (SMP) with 1 mM NADH (0 mg-protein/ml: 1.8 +/- 2.5%, 8 mg-protein/ml: 69.0 +/- 5.5%, each value was % of reduced Cu). Similarly, this reduction depended on NADH concentration at a fixed concentration of SMP (8 mg-protein/ml). These results indicated that the electron transport chain, especially complex I, participated in the reduction of Cu-PTSM in brain mitochondria, and this suggested that Cu-PTSM has the potential to act as a functional imaging agent for diagnosis of the electron transport chain.

Animals↗

PubMed1982

Import of proteins into mitochondria. Cytochrome b2 and cytochrome c peroxidase are located in the intermembrane space of yeast mitochondria.

Yeast mitochondria were fractionated into inner membrane, outer membrane, matrix, and intermembrane space. Identity and purity of each fraction were monitored by enzyme assays, dodecyl sulfate-polyacrylamide gel electrophoresis, and immunological detection of characteristic mitochondrial polypeptides. Cytochrome b2 and cytochrome c peroxidase were found to be components of the intermembrane space. The most reliable marker of the outer membrane was a major 29,000-dalton polypeptide component. The availability of submitochondrial fractions provides a basis for studying import of precursor polypeptides into isolated yeast mitochondria.

Biological Transport↗

PubMed1983

Investigations of the turnover of adrenocortical mitochondria. XVI. Effects of ethidium bromide on the ACTH-induced elongation of the half-life of rat zona fasciculata mitochondria.

ACTH significantly increases the half-life of rat zona fasciculata mitochondria. Since ethidium bromide inhibits this effect of ACTH, the hypothesis is advanced that the ACTH-induced slowing-down of the degradation rate of adrenocortical mitochondria involves mitochondrial DNA reduplication and transcription.

Adrenal Cortex↗

PubMed1981

Investigations on the turnover of adrenocortical mitochondria. XVII. A correlated stereological and autoradiographic study of the effects of chronic treatment with ethidium bromide on the growth of the rat zona reticularis mitochondria.

The effects of the prolonged administration of ethidium bromide (EB), at a dose provoking a persistent inhibition of the incorporation of 3H-thymidine and 3H-uridine into the mitochondrial fraction, on the zona reticularis of ACTH-treated rats were investigated. Stereologically, it was found that EB induces noticeable decrease in the total amount of the mitochondrial compartment, mainly due to the reduction in the number of organelles per cell. High resolution autoradiography showed that the mechanism underlying this effects of EB probably involves both the inhibition of mitochondria proliferation and the acceleration of their breakdown as "intact units". These findings suggest that the ACTH-induced maintenance of the zona reticularis mitochondria growth involves mitochondrial DNA reduplication and transcription.

Adrenal Cortex↗

PubMed1970

The Respiratory Chain of Plant Mitochondria: VIII. Reduction Kinetics of the Respiratory Chain Carriers of Mung Bean Mitochondria with Reduced Nicotinamide Adenine Dinucleotide.

Addition of 90 micromolar reduced nicotinamide adenine dinucleotide (NADH) in the presence of cyanide to a suspension of aerobic mung bean (Phaseolus aureus) mitochondria depleted with ADP and uncoupler gives a cycle of reduction of electron transport carriers followed by reoxidation, as NADH is oxidized to NAD(+) through the cyanide-insensitive, alternate oxidase by excess oxygen in the reaction medium. Under these conditions, cytochrome b(553) and the nonfluorescent, high potential flavoprotein Fp(ha) of the plant respiratory chain become completely reduced with half-times of 2.5 to 2.8 seconds for both components. Reoxidation of flavoprotein Fp(ha) on exhaustion of NADH is more rapid than that of cytochrome b(553). There is a lag of 1.5 seconds after NADH addition before any reduction of ubiquinone can be observed, whereas there is no lag perceptible in the reduction of flavoprotein Fp(ha) and cytochrome b(553). The half-time for ubiquinone reduction is 4.5 seconds, and the extent of reduction is 90% or greater. About 30% of cytochrome b(557) is reduced under these conditions with a half-time of 10 seconds; both cytochrome b(562) and the fluorescent, high potential flavoprotein Fp(hf) show little, if any, reduction. The two cytochromes c in these mitochondria, c(547) and c(549), are reduced in synchrony with a half-time of 0.8 second. These two components are already 60% reduced in the presence of cyanide but absence of substrate, and they become completely reduced on addition of NADH. These results indicated that reducing equivalents enter the respiratory chain from exogenous NADH at flavoprotein Fp(ha) and are rapidly transported through cytochrome b(553) to the cytochromes c; once the latter are completely reduced, reduction of ubiquinone begins. Ubiquinone appears to act as a storage pool for reducing equivalents entering the respiratory chain on the substrate side of coupling site 2. It is suggested that flavoprotein Fp(ha) and cytochrome b(553) together may act as the branching point in the plant respiratory chain from which forward electron transport can take place to oxygen through the cytochrome chain via cytochrome oxidase, or to oxygen through the alternate, cyanide-insensitive oxidase via the fluorescent, high potential flavoprotein Fp(hf).

Journal Article↗

PubMed1983

Electrochemically driven respiration in mitochondria and Paracoccus denitrificans. The coupling of the electrochemistry of horse heart cytochrome c with respiration in mitochondria and a model thereof, Paracoccus denitrificans.

By exploiting the rapid, direct electrochemistry of horse heart cytochrome c at a modified gold electrode it has been possible to couple the electrode reaction with respiration in rat liver mitochondria and in protoplasts of Paracoccus denitrificans, but not in protoplasts from E. coli. Oxidation of endogenous and exogenous sources of reducing equivalents via cytochrome c is also observed.

Animals↗

PubMed1982

[Reversible changes in the volume of isolated mitochondria in the course of ion flux oscillations between the mitochondria and the medium].

Glutaraldehyde has been used for electron microscopic studies of mitochondrial volume fluctuation during Sr2+--induced oscillation of ion fluxes. It has been shown that the observed ultrastructural and fluctuations of mitochondria is reversible to correlate with light-scattering value as well as to the direction of ion transfer. Determination of the intramitochondrial volume at different stages of oscillatory cycle shows the increase in the volume during the process of swelling up to 2.4-5.6 times compared with the shrihkate state.

Animals↗