G. Solaini - Academia.edu (original) (raw)
Papers by G. Solaini
Bollettino della Società italiana di biologia sperimentale, Jan 15, 1977
Bollettino della Società italiana di biologia sperimentale, Jan 30, 1984
The histochemical and biochemical myofibrillar ATPase activities of red and white muscle of the c... more The histochemical and biochemical myofibrillar ATPase activities of red and white muscle of the catfish and mullet have been investigated. The histochemical reactions confirmed the typical pattern of red and white muscle and the absence of growing fibers in the white muscle of the mullet. Biochemical assay were used to determine the ATPase activity of red and white muscle myofibrils. Ratios of white muscle activity/red muscle activity were found to 2.2 in the mullet and 2.3 in the catfish. The myofibrillar ATPase activity of mullet was less thermostable than that of catfish but is still in the range for fish leaving in warm waters.
Drugs under experimental and clinical research, 1985
Aclacinomycin, 4'-epi-doxorubicin and 4'-epi-tetrahydropyranyl-adriamycin, three novel an... more Aclacinomycin, 4'-epi-doxorubicin and 4'-epi-tetrahydropyranyl-adriamycin, three novel anthraquinone derivatives under investigation for their antitumour activity, showed an inhibitory effect on the in vitro respiration of mitochondria from rat hearts. The inhibition proved to be concentration-dependent in the range 0.05 to 1.40 mM and both the NADH-oxidase and the succinate oxidase systems were affected to different extents. Among the compounds tested, 4'-epi-tetrahydropyranyl-adriamycin appeared to be the least powerful effector, requiring a significantly higher concentration for 50% inhibition of oxidation than doxorubicin and the other analogues examined.
Cardiologia (Rome, Italy), 1992
Isolated hearts were subjected to 30 min of aerobic perfusion followed by 10 min of global normot... more Isolated hearts were subjected to 30 min of aerobic perfusion followed by 10 min of global normothermic ischemia and 40 min of reperfusion. We determined the release of purine catabolites (adenosine, inosine, hypoxanthine, xanthine, uric acid) and the incorporation of exogenous 3H-adenosine and 14C-hypoxanthine into cellular nucleotides. Ischemia-reperfusion produced remarkable reduction in the release of purine catabolites, with no significant variation in the incorporation of adenosine and hypoxanthine.
Bollettino della Società italiana di biologia sperimentale, Jan 30, 1976
Bollettino della Società italiana di biologia sperimentale, Jan 15, 1977
A short period of ischemia followed by reperfusion (ischemic preconditioning) is known to trigger... more A short period of ischemia followed by reperfusion (ischemic preconditioning) is known to trigger mechanisms that contribute to the prevention of ATP depletion. In ischemic conditions, most of the ATP hydrolysis can be attributed to mitochondrial F 1 F 0-ATPase (ATP synthase). The purpose of the present study was to examine the effect of myocardial ischemic preconditioning on the kinetics of ATP hydrolysis by F 1 F 0-ATPase. Preconditioning was accomplished by three 3-min periods of global ischemia separated by 3 min of reperfusion. Steady state ATP hydrolysis rates in both control and preconditioned mitochondria were not significantly different. This suggests that a large influence of the enzyme on the preconditioning mechanism may be excluded. However, the time required by the reaction to reach the steady state rate was increased in the preconditioned group before sustained ischemia, and it was even more enhanced in the first 5 min of reperfusion (101 ± 3.0 sec in preconditioned vs. 83.4 ± 4.4 sec in controls, p < 0.05). These results suggest that this transient increase in activation time may contribute to the cardioprotection by slowing the ATP depletion in the very critical early phase of post-ischemic reperfusion.
European Journal of Biochemistry, 1993
We report the detection of tryptophan phosphorescence emission from the sole residue in the Esubu... more We report the detection of tryptophan phosphorescence emission from the sole residue in the Esubunit of the bovine heart mitochondrial F,-ATPase complex. The phosphorescence spectrum, intensity and decay kinetics have been measured over the temperature range 160-273 K. The fine structure in the phosphorescence spectrum at low temperature, with the 0-0 vibrational band centered at 411 nm, reveals the hydrophobic nature of the chromophore's environment. Both the large width of the 0-0 vibrational band and the heterogeneous decay kinetics in fluid solution emphasize the existence of multiple conformations of the &-subunit, structures which are rather stable as they do not interconvert in the millisecond time scale. Further, from the relatively long triplet lifetime at 273 K, it is possible to infer the existence of a tight, rigid core in the structure of the &-subunit. Under subunit-dissociating conditions (6 M urea), the spectrum at 160 K undergoes a slight blue shift but since the phosphorescence lifetime, at all temperatures, is similar or longer than in the absence of dissociant, we conclude that dissociation does not lead to solvent exposure of the tryptophanyl side-chain. This conclusion is supported by the results obtained at 273 K by dissociating F,
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1987
The circular dichroic spectrum of the mitochondrial cytochrome bc1 complex isolated from bovine h... more The circular dichroic spectrum of the mitochondrial cytochrome bc1 complex isolated from bovine heart has been resolved into the contributions from the prosthetic groups: cytochrome c1, the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;Rieske&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; iron-sulphur centre and the two b cytochromes. It is apparent that firstly, the circular dichroism (CD) properties of cytochrome c1 within the bc1 complex differ from those found in the isolated cytochrome c1 and secondly, both the oxidized and reduced b cytochromes exhibit an intense spectrum of bilobic shape, with the wavelengths of the cross-over points closely corresponding to those of the maxima in the optical absorbance spectra. These latter CD features are discussed in relation to the proposed structure of cytochrome b.
Archives of Biochemistry and Biophysics, 1992
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2010
Many cancer cells are characterized by high rate of glycolysis and reduced rate of aerobic respir... more Many cancer cells are characterized by high rate of glycolysis and reduced rate of aerobic respiration, whose mechanism is still elusive. Here we investigate the down-regulation of oxidative phosphorylation (OXPHOS) in K-ras transformed mouse fibroblasts as compared to a control counterpart. Transcriptional analysis showed different expression levels of several OXPHOS nuclear genes in the two cell lines. In particular, during the exponential growth phase most genes encoding proteins of Complex I were expressed at lower levels in transformed cells. Consistently, a significant decrease of Complex I content was found in transformed cells. Moreover, analysis of NAD-dependent respiration and ATP synthesis indicated a strong decrease of Complex I activity in the mitochondria from neoplastic cells, that was confirmed by direct assay of the enzyme redox activity. At variance, succinate-dependent respiration and ATP synthesis were not significantly affected. Taken together, our results provide the new insight that the reduction of respiration observed in K-ras transformed cells is specifically due to a Complex I activity decrease.
Comparative Biochemistry and Physiology Part B: Comparative Biochemistry, 1992
ATPase from eel liver mitochondria at low concentrations preserves unaltered the enzymatic activi... more ATPase from eel liver mitochondria at low concentrations preserves unaltered the enzymatic activity for more than 20 min over a temperature range of 6-36°C. 2. The Arrbenius plot of ATP hydrolysis at saturating substrate concentration appears biphasic with a break-point at 16°C and activation energies of 14.4 and 56.1 kJ/mol. 3. The ultraviolet, fluorescence and circular dichroism spectra of the enzyme, below and above 16°C, have been recorded; the fluorescence emission spectra of F:ATPase excited at 275 nm, and the circular dichroism spectra, are different at the two temperatures examined. 4. It is concluded that temperature induces two different conformational states of F:ATPase with different catalytic properties. 5. Ultraviolet spectroscopic features and temperature-dependence of eel liver mitochondrial F:A'l'Pase are discussed in relation to mammalian F:ATPases.
Cytochrome Systems, 1987
The circular dichroism (CD) spectrum of the mitochondrial ubiquinol cytochrome c reductase (bc1 c... more The circular dichroism (CD) spectrum of the mitochondrial ubiquinol cytochrome c reductase (bc1 complex) isolated from beef heart has been resolved in the visible region into the contributions from the individual prosthetic groups: cytochrome c1, the “Rieske” iron-sulfur center and cytochrome(s) b.
Biochemical Journal, 1997
Treatment of bovine heart submitochondrial particles with a low concentration of 2-hydroxy-5-nitr... more Treatment of bovine heart submitochondrial particles with a low concentration of 2-hydroxy-5-nitrobenzyl bromide (HNB), a selective reagent for the Trp residue of the ε subunit [Baracca, Barogi, Lenaz and Solaini (1993) Int. J. Biochem. 25, 1269-1275], enhances the ATP hydrolytic activity of the particles exclusively when the natural inhibitor protein IF1 is present. Similarly, isolated F1 [the catalytic sector of the mitochondrial H+-ATPase complex (ATP synthase)] treated with the reagent has the ATPase activity enhanced exclusively if IF1 is bound to it. These experiments suggest that the modification of the ε subunit decreases the inhibitory activity of IF1, eliciting the search for a relationship between the ε subunit and the inhibitory protein. Certainly, a reverse relationship exists because HNB binds covalently to the isolated F1 exclusively when the inhibitory protein is present. This finding is consistent with the existence of the ε subunit in different conformational state...
Drugs under experimental and clinical research, 1991
Isolated rat heart was perfused with 18 microM doxorubicin in the recirculating buffer. This trea... more Isolated rat heart was perfused with 18 microM doxorubicin in the recirculating buffer. This treatment resulted in progressive contractile impairment. Aortic flow and minute work (i.e the product of cardiac output and peak systolic pressure) were reduced up to 20 and 29% of basal values, respectively. These parameters were partially restored in hearts perfused with 400 microM spermine, a naturally occurring polyamine, and 18 microM doxorubicin in the recirculating buffer. The results suggest the need for an investigation of the possible antagonistic role of polyamines against anthracycline cardiotoxicity.
Drugs under experimental and clinical research, 1985
A set of three novel anthracyclines, active as antitumour agents, has been examined for their pos... more A set of three novel anthracyclines, active as antitumour agents, has been examined for their possible effects on rat heart mitochondrial respiration. The in vitro inhibiting effects of the compounds have been compared with that of the older doxorubicin. Aclacinomycin was generally more inhibitory than doxorubicin, 4'-epi-doxorubicin and 4'-epi-tetrahydropyranyl-adriamycin, with both succinate and NAD+-linked substrates. Attempts to prevent anthracycline from inhibiting the succinate oxidase activity by means of adding exogenous coenzyme Q10 gave encouraging results, the inhibiting effect being in fact reduced.
Cell Biology International Reports, 1986
Human Molecular Genetics, 2008
Autosomal dominant optic atrophy (ADOA), the commonest cause of inherited optic atrophy, is cause... more Autosomal dominant optic atrophy (ADOA), the commonest cause of inherited optic atrophy, is caused by mutations in the ubiquitously expressed gene optic atrophy 1 (OPA1), involved in fusion and biogenesis of the inner membrane of mitochondria. Bioenergetic failure, mitochondrial network abnormalities and increased apoptosis have all been proposed as possible causal factors. However, their relative contribution to pathogenesis as well as the prominent susceptibility of the retinal ganglion cell (RGC) in this disease remains uncertain. Here we identify a novel deletion of OPA1 gene in the GTPase domain in three patients affected by ADOA. Muscle biopsy of the patients showed neurogenic atrophy and abnormal morphology and distribution of mitochondria. Confocal microscopy revealed increased mitochondrial fragmentation in fibroblasts as well as in myotubes, where mitochondria were also unevenly distributed, with clustered organelles alternating with areas where mitochondria were sparse. These abnormalities were not associated with altered bioenergetics or increased susceptibility to pro-apoptotic stimuli. Therefore, changes in mitochondrial shape and distribution can be independent of other reported effects of OPA1 mutations, and therefore may be the primary cause of the disease. The arrangement of mitochondria in RGCs, which degenerate in ADOA, may be exquisitely sensitive to disturbance, and this may lead to bioenergetic crisis and/or induction of apoptosis. Our results highlight the importance of mitochondrial dynamics in the disease per se, and point to the loss of the fine positioning of mitochondria in the axons of RGCs as a possible explanation for their predominant degeneration in ADOA.
Biochemical Journal, 2004
We analysed key biochemical features that reflect the balance between glycolysis and glucose oxid... more We analysed key biochemical features that reflect the balance between glycolysis and glucose oxidation in cybrids (cytoplasmic hybrids) harbouring a representative sample of mitochondrial DNA point mutations and deletions. The cybrids analysed had the same 143B cell nuclear background and were isogenic for the mitochondrial background. The 143B cell line and its ρ0 counterpart were used as controls. All cells analysed were in a dynamic state, and cell number, time of plating, culture medium, extracellular volume and time of harvest and assay were strictly controlled. Intra- and extra-cellular lactate and pyruvate levels were measured in homoplasmic wild-type and mutant cells, and correlated with rates of ATP synthesis and O2 consumption. In all mutant cell lines, except those with the T8993C mutation in the ATPase 6 gene, glycolysis was increased even under conditions of low glucose, as demonstrated by increased levels of extracellular lactate and pyruvate. Extracellular lactate lev...
Bollettino della Società italiana di biologia sperimentale, Jan 15, 1977
Bollettino della Società italiana di biologia sperimentale, Jan 30, 1984
The histochemical and biochemical myofibrillar ATPase activities of red and white muscle of the c... more The histochemical and biochemical myofibrillar ATPase activities of red and white muscle of the catfish and mullet have been investigated. The histochemical reactions confirmed the typical pattern of red and white muscle and the absence of growing fibers in the white muscle of the mullet. Biochemical assay were used to determine the ATPase activity of red and white muscle myofibrils. Ratios of white muscle activity/red muscle activity were found to 2.2 in the mullet and 2.3 in the catfish. The myofibrillar ATPase activity of mullet was less thermostable than that of catfish but is still in the range for fish leaving in warm waters.
Drugs under experimental and clinical research, 1985
Aclacinomycin, 4'-epi-doxorubicin and 4'-epi-tetrahydropyranyl-adriamycin, three novel an... more Aclacinomycin, 4'-epi-doxorubicin and 4'-epi-tetrahydropyranyl-adriamycin, three novel anthraquinone derivatives under investigation for their antitumour activity, showed an inhibitory effect on the in vitro respiration of mitochondria from rat hearts. The inhibition proved to be concentration-dependent in the range 0.05 to 1.40 mM and both the NADH-oxidase and the succinate oxidase systems were affected to different extents. Among the compounds tested, 4'-epi-tetrahydropyranyl-adriamycin appeared to be the least powerful effector, requiring a significantly higher concentration for 50% inhibition of oxidation than doxorubicin and the other analogues examined.
Cardiologia (Rome, Italy), 1992
Isolated hearts were subjected to 30 min of aerobic perfusion followed by 10 min of global normot... more Isolated hearts were subjected to 30 min of aerobic perfusion followed by 10 min of global normothermic ischemia and 40 min of reperfusion. We determined the release of purine catabolites (adenosine, inosine, hypoxanthine, xanthine, uric acid) and the incorporation of exogenous 3H-adenosine and 14C-hypoxanthine into cellular nucleotides. Ischemia-reperfusion produced remarkable reduction in the release of purine catabolites, with no significant variation in the incorporation of adenosine and hypoxanthine.
Bollettino della Società italiana di biologia sperimentale, Jan 30, 1976
Bollettino della Società italiana di biologia sperimentale, Jan 15, 1977
A short period of ischemia followed by reperfusion (ischemic preconditioning) is known to trigger... more A short period of ischemia followed by reperfusion (ischemic preconditioning) is known to trigger mechanisms that contribute to the prevention of ATP depletion. In ischemic conditions, most of the ATP hydrolysis can be attributed to mitochondrial F 1 F 0-ATPase (ATP synthase). The purpose of the present study was to examine the effect of myocardial ischemic preconditioning on the kinetics of ATP hydrolysis by F 1 F 0-ATPase. Preconditioning was accomplished by three 3-min periods of global ischemia separated by 3 min of reperfusion. Steady state ATP hydrolysis rates in both control and preconditioned mitochondria were not significantly different. This suggests that a large influence of the enzyme on the preconditioning mechanism may be excluded. However, the time required by the reaction to reach the steady state rate was increased in the preconditioned group before sustained ischemia, and it was even more enhanced in the first 5 min of reperfusion (101 ± 3.0 sec in preconditioned vs. 83.4 ± 4.4 sec in controls, p < 0.05). These results suggest that this transient increase in activation time may contribute to the cardioprotection by slowing the ATP depletion in the very critical early phase of post-ischemic reperfusion.
European Journal of Biochemistry, 1993
We report the detection of tryptophan phosphorescence emission from the sole residue in the Esubu... more We report the detection of tryptophan phosphorescence emission from the sole residue in the Esubunit of the bovine heart mitochondrial F,-ATPase complex. The phosphorescence spectrum, intensity and decay kinetics have been measured over the temperature range 160-273 K. The fine structure in the phosphorescence spectrum at low temperature, with the 0-0 vibrational band centered at 411 nm, reveals the hydrophobic nature of the chromophore's environment. Both the large width of the 0-0 vibrational band and the heterogeneous decay kinetics in fluid solution emphasize the existence of multiple conformations of the &-subunit, structures which are rather stable as they do not interconvert in the millisecond time scale. Further, from the relatively long triplet lifetime at 273 K, it is possible to infer the existence of a tight, rigid core in the structure of the &-subunit. Under subunit-dissociating conditions (6 M urea), the spectrum at 160 K undergoes a slight blue shift but since the phosphorescence lifetime, at all temperatures, is similar or longer than in the absence of dissociant, we conclude that dissociation does not lead to solvent exposure of the tryptophanyl side-chain. This conclusion is supported by the results obtained at 273 K by dissociating F,
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1987
The circular dichroic spectrum of the mitochondrial cytochrome bc1 complex isolated from bovine h... more The circular dichroic spectrum of the mitochondrial cytochrome bc1 complex isolated from bovine heart has been resolved into the contributions from the prosthetic groups: cytochrome c1, the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;Rieske&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; iron-sulphur centre and the two b cytochromes. It is apparent that firstly, the circular dichroism (CD) properties of cytochrome c1 within the bc1 complex differ from those found in the isolated cytochrome c1 and secondly, both the oxidized and reduced b cytochromes exhibit an intense spectrum of bilobic shape, with the wavelengths of the cross-over points closely corresponding to those of the maxima in the optical absorbance spectra. These latter CD features are discussed in relation to the proposed structure of cytochrome b.
Archives of Biochemistry and Biophysics, 1992
Biochimica et Biophysica Acta (BBA) - Bioenergetics, 2010
Many cancer cells are characterized by high rate of glycolysis and reduced rate of aerobic respir... more Many cancer cells are characterized by high rate of glycolysis and reduced rate of aerobic respiration, whose mechanism is still elusive. Here we investigate the down-regulation of oxidative phosphorylation (OXPHOS) in K-ras transformed mouse fibroblasts as compared to a control counterpart. Transcriptional analysis showed different expression levels of several OXPHOS nuclear genes in the two cell lines. In particular, during the exponential growth phase most genes encoding proteins of Complex I were expressed at lower levels in transformed cells. Consistently, a significant decrease of Complex I content was found in transformed cells. Moreover, analysis of NAD-dependent respiration and ATP synthesis indicated a strong decrease of Complex I activity in the mitochondria from neoplastic cells, that was confirmed by direct assay of the enzyme redox activity. At variance, succinate-dependent respiration and ATP synthesis were not significantly affected. Taken together, our results provide the new insight that the reduction of respiration observed in K-ras transformed cells is specifically due to a Complex I activity decrease.
Comparative Biochemistry and Physiology Part B: Comparative Biochemistry, 1992
ATPase from eel liver mitochondria at low concentrations preserves unaltered the enzymatic activi... more ATPase from eel liver mitochondria at low concentrations preserves unaltered the enzymatic activity for more than 20 min over a temperature range of 6-36°C. 2. The Arrbenius plot of ATP hydrolysis at saturating substrate concentration appears biphasic with a break-point at 16°C and activation energies of 14.4 and 56.1 kJ/mol. 3. The ultraviolet, fluorescence and circular dichroism spectra of the enzyme, below and above 16°C, have been recorded; the fluorescence emission spectra of F:ATPase excited at 275 nm, and the circular dichroism spectra, are different at the two temperatures examined. 4. It is concluded that temperature induces two different conformational states of F:ATPase with different catalytic properties. 5. Ultraviolet spectroscopic features and temperature-dependence of eel liver mitochondrial F:A'l'Pase are discussed in relation to mammalian F:ATPases.
Cytochrome Systems, 1987
The circular dichroism (CD) spectrum of the mitochondrial ubiquinol cytochrome c reductase (bc1 c... more The circular dichroism (CD) spectrum of the mitochondrial ubiquinol cytochrome c reductase (bc1 complex) isolated from beef heart has been resolved in the visible region into the contributions from the individual prosthetic groups: cytochrome c1, the “Rieske” iron-sulfur center and cytochrome(s) b.
Biochemical Journal, 1997
Treatment of bovine heart submitochondrial particles with a low concentration of 2-hydroxy-5-nitr... more Treatment of bovine heart submitochondrial particles with a low concentration of 2-hydroxy-5-nitrobenzyl bromide (HNB), a selective reagent for the Trp residue of the ε subunit [Baracca, Barogi, Lenaz and Solaini (1993) Int. J. Biochem. 25, 1269-1275], enhances the ATP hydrolytic activity of the particles exclusively when the natural inhibitor protein IF1 is present. Similarly, isolated F1 [the catalytic sector of the mitochondrial H+-ATPase complex (ATP synthase)] treated with the reagent has the ATPase activity enhanced exclusively if IF1 is bound to it. These experiments suggest that the modification of the ε subunit decreases the inhibitory activity of IF1, eliciting the search for a relationship between the ε subunit and the inhibitory protein. Certainly, a reverse relationship exists because HNB binds covalently to the isolated F1 exclusively when the inhibitory protein is present. This finding is consistent with the existence of the ε subunit in different conformational state...
Drugs under experimental and clinical research, 1991
Isolated rat heart was perfused with 18 microM doxorubicin in the recirculating buffer. This trea... more Isolated rat heart was perfused with 18 microM doxorubicin in the recirculating buffer. This treatment resulted in progressive contractile impairment. Aortic flow and minute work (i.e the product of cardiac output and peak systolic pressure) were reduced up to 20 and 29% of basal values, respectively. These parameters were partially restored in hearts perfused with 400 microM spermine, a naturally occurring polyamine, and 18 microM doxorubicin in the recirculating buffer. The results suggest the need for an investigation of the possible antagonistic role of polyamines against anthracycline cardiotoxicity.
Drugs under experimental and clinical research, 1985
A set of three novel anthracyclines, active as antitumour agents, has been examined for their pos... more A set of three novel anthracyclines, active as antitumour agents, has been examined for their possible effects on rat heart mitochondrial respiration. The in vitro inhibiting effects of the compounds have been compared with that of the older doxorubicin. Aclacinomycin was generally more inhibitory than doxorubicin, 4'-epi-doxorubicin and 4'-epi-tetrahydropyranyl-adriamycin, with both succinate and NAD+-linked substrates. Attempts to prevent anthracycline from inhibiting the succinate oxidase activity by means of adding exogenous coenzyme Q10 gave encouraging results, the inhibiting effect being in fact reduced.
Cell Biology International Reports, 1986
Human Molecular Genetics, 2008
Autosomal dominant optic atrophy (ADOA), the commonest cause of inherited optic atrophy, is cause... more Autosomal dominant optic atrophy (ADOA), the commonest cause of inherited optic atrophy, is caused by mutations in the ubiquitously expressed gene optic atrophy 1 (OPA1), involved in fusion and biogenesis of the inner membrane of mitochondria. Bioenergetic failure, mitochondrial network abnormalities and increased apoptosis have all been proposed as possible causal factors. However, their relative contribution to pathogenesis as well as the prominent susceptibility of the retinal ganglion cell (RGC) in this disease remains uncertain. Here we identify a novel deletion of OPA1 gene in the GTPase domain in three patients affected by ADOA. Muscle biopsy of the patients showed neurogenic atrophy and abnormal morphology and distribution of mitochondria. Confocal microscopy revealed increased mitochondrial fragmentation in fibroblasts as well as in myotubes, where mitochondria were also unevenly distributed, with clustered organelles alternating with areas where mitochondria were sparse. These abnormalities were not associated with altered bioenergetics or increased susceptibility to pro-apoptotic stimuli. Therefore, changes in mitochondrial shape and distribution can be independent of other reported effects of OPA1 mutations, and therefore may be the primary cause of the disease. The arrangement of mitochondria in RGCs, which degenerate in ADOA, may be exquisitely sensitive to disturbance, and this may lead to bioenergetic crisis and/or induction of apoptosis. Our results highlight the importance of mitochondrial dynamics in the disease per se, and point to the loss of the fine positioning of mitochondria in the axons of RGCs as a possible explanation for their predominant degeneration in ADOA.
Biochemical Journal, 2004
We analysed key biochemical features that reflect the balance between glycolysis and glucose oxid... more We analysed key biochemical features that reflect the balance between glycolysis and glucose oxidation in cybrids (cytoplasmic hybrids) harbouring a representative sample of mitochondrial DNA point mutations and deletions. The cybrids analysed had the same 143B cell nuclear background and were isogenic for the mitochondrial background. The 143B cell line and its ρ0 counterpart were used as controls. All cells analysed were in a dynamic state, and cell number, time of plating, culture medium, extracellular volume and time of harvest and assay were strictly controlled. Intra- and extra-cellular lactate and pyruvate levels were measured in homoplasmic wild-type and mutant cells, and correlated with rates of ATP synthesis and O2 consumption. In all mutant cell lines, except those with the T8993C mutation in the ATPase 6 gene, glycolysis was increased even under conditions of low glucose, as demonstrated by increased levels of extracellular lactate and pyruvate. Extracellular lactate lev...