Stefano Massari - Academia.edu (original) (raw)

Papers by Stefano Massari

The Journal of Membrane Biology, Dec 1, 1972

A procedure is described for the calculation of solute fltL~es in mitochondria from absorbance me... more A procedure is described for the calculation of solute fltL~es in mitochondria from absorbance measurements. The procedure assumes that mitochondria behave as osmometers and that they are always at osmotic equilibrium. The rates and amounts of K + translocation have been calculated simultaneously, with the photometric procedure and electrometrically, during passive K + efflux coupled to Ca ++ uptake and during active K + uptake and passive K + release coupled with anion translocation. Good agreement has been found between the two sets of measurements. The data are compatible with the concept that the energy-linked, ion translocation-coupled, mitochondrial swelling is osmotic in nature. It is concluded that the changes of absorbance are quantitatively related to changes in the inner volume and therefore the photometric procedure can be used to calculate ion fluxes of osmotically active species under various circumstances.

Biochemistry, Feb 1, 1974

Atebrin is bound with high affinity to energized submitochondrial particles: number of sites, 43 ... more Atebrin is bound with high affinity to energized submitochondrial particles: number of sites, 43 Hmol/g of protein ; KD = 8 p~. At low protein :dye ratios the binding is accompanied by a quenching of fluorescence. During quenching the absorbance spectra indicate dye aggregation rather than acid-base transition. At increasing protein : dye ratios there is first a decrease of the fluorescence quenching and then a fluorescence enhancement. The latter is accompanied by an increase of fluorescence polarization. Kinetically, particle energization at a high protein :dye ratio results first in an enhancement and then in a quenching phase, both of them

Biofactors, 1998

This review summarizes recent work on the regulation of the permeability transition pore, a cyclo... more This review summarizes recent work on the regulation of the permeability transition pore, a cyclosporin A‐sensitive mitochondrial channel that may play a role in intracellular calcium homeostasis and in a variety of forms of cell death. The basic bioenergetics aspects of pore modulation are discussed, with some emphasis on the links between oxidative stress and pore dysregulation as a potential cause of mitochondrial dysfunction that may be relevant to cell injury.

Annals of the New York Academy of Sciences, Feb 1, 1974

... EC Slater, Z. Kaniuga & L. Wojtczak, Eds. : 75. Academic Press Inc. Lon-don, England. 27.... more ... EC Slater, Z. Kaniuga & L. Wojtczak, Eds. : 75. Academic Press Inc. Lon-don, England. 27. CHANCE, B.& L. MELA. 1966. ... 30. AZZONE, G. F. & S. MASSARI. 1972. FEBS Letters 28: 31. COLONNA, R., P. DELL'ANTONE & GF AZZONE. 1970. FEBS Letters 10: 13. 32. ...

Cellular and Molecular Life Sciences, Jul 1, 1976

Weak and strong organic bases behave in an opposite manner in respect to several mitochondrial fu... more Weak and strong organic bases behave in an opposite manner in respect to several mitochondrial functions. The former induce a catalytic exchange with K + in valinomycon-treated, respiratory-inhibited mitochondria, and act as uncouplers in respiring mitochondria. The latter induce a stoicheometric exchange with K+ and are actively taken up by respiring mitochondria.

Arch Biochem Biophys, 1976

Developments in Biophysical Research, 1980

In recent times fatty acids were used not only as probes for the phospholipid bilayer structure, ... more In recent times fatty acids were used not only as probes for the phospholipid bilayer structure, but also as inducers of important biological processes such as membrane fusion (1), membrane permeability changes (2), phospholipid exchange (3,4) and phospholipid vesicle size enlargement (3–7). These observations point out that fatty acids, having a higher concentration in heart and brain than in other tissues, may play an important role in regulating many biological functions. In the present work the role of fatty acids in phospholipid exchange and in vesicle size enlargement is investigated.

Advances in Experimental Medicine and Biology, 1971

About 30 years ago it was understood thai the cell membrane had the capacity of translocating Na ... more About 30 years ago it was understood thai the cell membrane had the capacity of translocating Na and K. More recently this property has been related to the utilization of ATP (for a review cf Ref. 1). The conversion of the energy of a chemical compound such as ATP into anion concentration gradient may be defined as a chemiosmotic transduction. It is immediately clear that this is a foundamental property of the plasma membrne. Very recently it has been reported (2) that the Na pump of the red cell could be reversed, i.e. that ATP could be synthsized t the expense of concentration gradients of Na+ and K+. Unfortunately however the experiments gave only a qualitative indication of this reaction since no net synthesis of ATP could be detected.

Journal of Applied Physics, 1953

Reflection and transmission coefficients are important parameters of a wave-guide junction. It is... more Reflection and transmission coefficients are important parameters of a wave-guide junction. It is shown that these parameters in phase as well as in magnitude may be read directly from a graph. A short-circuit is moved in one of two wave guides that are connected by the junction, and the corresponding reflection coefficient is measured in the other wave guide as in a standard method. The positions of the short-circuit, however, are taken equally spaced every ⅛th of a wavelength. When plotted in the complex plane, the corresponding reflection coefficients fall on a circle and the chords joining opposite points intersect at a point that is simply related to the desired parameters. When very accurate measurements are desired, 8 or even 16 short-circuit positions spaced at116th or132th wavelength can be used. The quality of the chord intersection then gives a control of the experiment by showing systematic or random errors. When the intersection is not perfect, because of random errors,...

Experientia, 1976

Weak and strong organic bases behave in an opposite manner in respect to several mitochondrial fu... more Weak and strong organic bases behave in an opposite manner in respect to several mitochondrial functions. The former induce a catalytic exchange with K + in valinomycon-treated, respiratory-inhibited mitochondria, and act as uncouplers in respiring mitochondria. The latter induce a stoicheometric exchange with K+ and are actively taken up by respiring mitochondria.

BioFactors, 1998

This review summarizes recent work on the regulation of the permeability transition pore, a cyclo... more This review summarizes recent work on the regulation of the permeability transition pore, a cyclosporin A‐sensitive mitochondrial channel that may play a role in intracellular calcium homeostasis and in a variety of forms of cell death. The basic bioenergetics aspects of pore modulation are discussed, with some emphasis on the links between oxidative stress and pore dysregulation as a potential cause of mitochondrial dysfunction that may be relevant to cell injury.

Biochimica et Biophysica Acta (BBA) - Biomembranes, 1980

Dipalmitoyl phosphatidylcJ~oline vesicles incubated in the presence of increasing amounts of myri... more Dipalmitoyl phosphatidylcJ~oline vesicles incubated in the presence of increasing amounts of myristic acid showed a progressive translocation of phospholipid molecules across a dialysis membrane. The rate of phospholipid translocation increased abruptly at a 'critical' value of myristic acid concentration. The translocation rate of mixed dipalmitoyl phosphatidylcholine/myristic acid vesicles obtained by cosonicating the two components was also dependent on a 'critical' fatty acid concentration. A marked release of K ÷ and different responses of fluorescent probes to the fatty acid addition were observed at this concentration.

Biochimica et Biophysica Acta (BBA) - Biomembranes, 1980

Size enlargement of dipalmitoyl phosphatidylcholine vesicles was greatly accelerated in the range... more Size enlargement of dipalmitoyl phosphatidylcholine vesicles was greatly accelerated in the range of the phase-transition temperatures, when fatty acid concentration was above a threshold level ('critical' concentration). This 'critical' concentration varied with the length of the fatty acid chain. The size enlargement process had second~rder kinetics dependent on the vesicle concentration. Alkaline pH and low ionic strength inhibited the rate of size enlargement. Phospholipid exchange between dimyristoyl and dipalmitoyl phosphatidylcholine vesicles increased abruptly above a 'critical' fatty acid concentration. The donor vesicles were those vesicles in which fatty acids reached the 'critical' concentration. The phospholipid exchange occurred both in fluid-and in solidstate vesicles. The 'critical' fatty acid concentration accelerating the phospholipid exchange process was lower than that accelerating the size enlargement process. The phospholipid exchange process explained in terms of a diminished hydrophobic attraction among the phospholipid molecules of the bilayer occurs via a free phospholipid molecule transfer through the aqueous phase. The size enlargement process is interpreted in terms of high fatty acid concentration in the membrane fluid domains. The membrane structure is locally perturbed inducing vesicle sticking after collision.

Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1977

Cation translocation across the membrane of cytochrome oxidase reconstituted vesicles may be foll... more Cation translocation across the membrane of cytochrome oxidase reconstituted vesicles may be followed with a simple spectrophotometric method. Cytochrome oxidase reconstituted vesicles, supplemented with ascorbate and cytochrome c, induce large spectral changes of the positive dye safranine, reversed by uncouplers and inhibitors of respiration. The dye is probably accumulated in the inner space of the vesicles, where it reaches high concentrations and aggregates. The spectral shifts and the absorbance changes, due to aggregation, are proportional to the amount of the dye taken up and depend on the respiratory control. In the presence of potassium, valinomycin causes an inhibition, whereas nigericin stimulates the dye uptake. The data are discussed in terms of electrical potential dependent fluxes.

Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1978

The correlation between A~H, the proton electrochemical potential difference, and the rate of con... more The correlation between A~H, the proton electrochemical potential difference, and the rate of controlled respiration is analyzed. ApH (the proton concentration gradient) is measured on the distribution of [3H]acetate, and A~ (the membrane potential) on the distribution of 86Rb +, 4SCa2+ and [3H]triphenylmethylphosphonium used either alone or simultaneously. The effects of the addition of ADP + hexokinase (state-3 ADP) and of carbonylcyanide trifluoromethoxyphenylhydrazone (state-3 uncoupler) on respiration and A~H are not equivalent: the uncoupler depresses A/~H more than ADP at equivalent respiratory rates. The effects of the additions of nigericin-valinomycin and of ionophore A23187 (state-3 cation transport) and of carbonylcyanide trifluoromethoxyphenylhydrazone (state 3-uncoupler) on respiration and A~H are also not equivalent: the uncoupler depresses A~H more than A23187 and nigericin + valinomycin at equivalent respiratory rate. A23187 is very efficient in stimulating respiration with negligible Ap H changes.

American Journal of Physiology-Renal Physiology, 2009

Development of the mitochondrial permeability transition (MPT) can importantly contribute to leth... more Development of the mitochondrial permeability transition (MPT) can importantly contribute to lethal cell injury from both necrosis and apoptosis, but its role varies considerably with both the type of cell and type of injury, and it can be strongly opposed by the normally abundant endogenous metabolites ADP and Mg2+. To better characterize the MPT in kidney proximal tubule cells and assess its contribution to injury to them, we have refined and validated approaches to follow the process in whole kidney proximal tubules and studied its regulation in normoxic tubules and after hypoxia-reoxygenation (H/R). Physiological levels of ADP and Mg2+greatly decreased sensitivity to the MPT. Inhibition of cyclophilin D by cyclosporine A (CsA) effectively opposed the MPT only in the presence of ADP and/or Mg2+. Nonesterified fatty acids (NEFA) had a large role in the decreased resistance to the MPT seen after H/R irrespective of the available substrate or the presence of ADP, Mg2+, or CsA, but r...

The Journal of Membrane Biology, Dec 1, 1972

A procedure is described for the calculation of solute fltL~es in mitochondria from absorbance me... more A procedure is described for the calculation of solute fltL~es in mitochondria from absorbance measurements. The procedure assumes that mitochondria behave as osmometers and that they are always at osmotic equilibrium. The rates and amounts of K + translocation have been calculated simultaneously, with the photometric procedure and electrometrically, during passive K + efflux coupled to Ca ++ uptake and during active K + uptake and passive K + release coupled with anion translocation. Good agreement has been found between the two sets of measurements. The data are compatible with the concept that the energy-linked, ion translocation-coupled, mitochondrial swelling is osmotic in nature. It is concluded that the changes of absorbance are quantitatively related to changes in the inner volume and therefore the photometric procedure can be used to calculate ion fluxes of osmotically active species under various circumstances.

Biochemistry, Feb 1, 1974

Atebrin is bound with high affinity to energized submitochondrial particles: number of sites, 43 ... more Atebrin is bound with high affinity to energized submitochondrial particles: number of sites, 43 Hmol/g of protein ; KD = 8 p~. At low protein :dye ratios the binding is accompanied by a quenching of fluorescence. During quenching the absorbance spectra indicate dye aggregation rather than acid-base transition. At increasing protein : dye ratios there is first a decrease of the fluorescence quenching and then a fluorescence enhancement. The latter is accompanied by an increase of fluorescence polarization. Kinetically, particle energization at a high protein :dye ratio results first in an enhancement and then in a quenching phase, both of them

Biofactors, 1998

This review summarizes recent work on the regulation of the permeability transition pore, a cyclo... more This review summarizes recent work on the regulation of the permeability transition pore, a cyclosporin A‐sensitive mitochondrial channel that may play a role in intracellular calcium homeostasis and in a variety of forms of cell death. The basic bioenergetics aspects of pore modulation are discussed, with some emphasis on the links between oxidative stress and pore dysregulation as a potential cause of mitochondrial dysfunction that may be relevant to cell injury.

Annals of the New York Academy of Sciences, Feb 1, 1974

... EC Slater, Z. Kaniuga & L. Wojtczak, Eds. : 75. Academic Press Inc. Lon-don, England. 27.... more ... EC Slater, Z. Kaniuga & L. Wojtczak, Eds. : 75. Academic Press Inc. Lon-don, England. 27. CHANCE, B.& L. MELA. 1966. ... 30. AZZONE, G. F. & S. MASSARI. 1972. FEBS Letters 28: 31. COLONNA, R., P. DELL'ANTONE & GF AZZONE. 1970. FEBS Letters 10: 13. 32. ...

Cellular and Molecular Life Sciences, Jul 1, 1976

Weak and strong organic bases behave in an opposite manner in respect to several mitochondrial fu... more Weak and strong organic bases behave in an opposite manner in respect to several mitochondrial functions. The former induce a catalytic exchange with K + in valinomycon-treated, respiratory-inhibited mitochondria, and act as uncouplers in respiring mitochondria. The latter induce a stoicheometric exchange with K+ and are actively taken up by respiring mitochondria.

Arch Biochem Biophys, 1976

Developments in Biophysical Research, 1980

In recent times fatty acids were used not only as probes for the phospholipid bilayer structure, ... more In recent times fatty acids were used not only as probes for the phospholipid bilayer structure, but also as inducers of important biological processes such as membrane fusion (1), membrane permeability changes (2), phospholipid exchange (3,4) and phospholipid vesicle size enlargement (3–7). These observations point out that fatty acids, having a higher concentration in heart and brain than in other tissues, may play an important role in regulating many biological functions. In the present work the role of fatty acids in phospholipid exchange and in vesicle size enlargement is investigated.

Advances in Experimental Medicine and Biology, 1971

About 30 years ago it was understood thai the cell membrane had the capacity of translocating Na ... more About 30 years ago it was understood thai the cell membrane had the capacity of translocating Na and K. More recently this property has been related to the utilization of ATP (for a review cf Ref. 1). The conversion of the energy of a chemical compound such as ATP into anion concentration gradient may be defined as a chemiosmotic transduction. It is immediately clear that this is a foundamental property of the plasma membrne. Very recently it has been reported (2) that the Na pump of the red cell could be reversed, i.e. that ATP could be synthsized t the expense of concentration gradients of Na+ and K+. Unfortunately however the experiments gave only a qualitative indication of this reaction since no net synthesis of ATP could be detected.

Journal of Applied Physics, 1953

Reflection and transmission coefficients are important parameters of a wave-guide junction. It is... more Reflection and transmission coefficients are important parameters of a wave-guide junction. It is shown that these parameters in phase as well as in magnitude may be read directly from a graph. A short-circuit is moved in one of two wave guides that are connected by the junction, and the corresponding reflection coefficient is measured in the other wave guide as in a standard method. The positions of the short-circuit, however, are taken equally spaced every ⅛th of a wavelength. When plotted in the complex plane, the corresponding reflection coefficients fall on a circle and the chords joining opposite points intersect at a point that is simply related to the desired parameters. When very accurate measurements are desired, 8 or even 16 short-circuit positions spaced at116th or132th wavelength can be used. The quality of the chord intersection then gives a control of the experiment by showing systematic or random errors. When the intersection is not perfect, because of random errors,...

Experientia, 1976

Weak and strong organic bases behave in an opposite manner in respect to several mitochondrial fu... more Weak and strong organic bases behave in an opposite manner in respect to several mitochondrial functions. The former induce a catalytic exchange with K + in valinomycon-treated, respiratory-inhibited mitochondria, and act as uncouplers in respiring mitochondria. The latter induce a stoicheometric exchange with K+ and are actively taken up by respiring mitochondria.

BioFactors, 1998

This review summarizes recent work on the regulation of the permeability transition pore, a cyclo... more This review summarizes recent work on the regulation of the permeability transition pore, a cyclosporin A‐sensitive mitochondrial channel that may play a role in intracellular calcium homeostasis and in a variety of forms of cell death. The basic bioenergetics aspects of pore modulation are discussed, with some emphasis on the links between oxidative stress and pore dysregulation as a potential cause of mitochondrial dysfunction that may be relevant to cell injury.

Biochimica et Biophysica Acta (BBA) - Biomembranes, 1980

Dipalmitoyl phosphatidylcJ~oline vesicles incubated in the presence of increasing amounts of myri... more Dipalmitoyl phosphatidylcJ~oline vesicles incubated in the presence of increasing amounts of myristic acid showed a progressive translocation of phospholipid molecules across a dialysis membrane. The rate of phospholipid translocation increased abruptly at a 'critical' value of myristic acid concentration. The translocation rate of mixed dipalmitoyl phosphatidylcholine/myristic acid vesicles obtained by cosonicating the two components was also dependent on a 'critical' fatty acid concentration. A marked release of K ÷ and different responses of fluorescent probes to the fatty acid addition were observed at this concentration.

Biochimica et Biophysica Acta (BBA) - Biomembranes, 1980

Size enlargement of dipalmitoyl phosphatidylcholine vesicles was greatly accelerated in the range... more Size enlargement of dipalmitoyl phosphatidylcholine vesicles was greatly accelerated in the range of the phase-transition temperatures, when fatty acid concentration was above a threshold level ('critical' concentration). This 'critical' concentration varied with the length of the fatty acid chain. The size enlargement process had second~rder kinetics dependent on the vesicle concentration. Alkaline pH and low ionic strength inhibited the rate of size enlargement. Phospholipid exchange between dimyristoyl and dipalmitoyl phosphatidylcholine vesicles increased abruptly above a 'critical' fatty acid concentration. The donor vesicles were those vesicles in which fatty acids reached the 'critical' concentration. The phospholipid exchange occurred both in fluid-and in solidstate vesicles. The 'critical' fatty acid concentration accelerating the phospholipid exchange process was lower than that accelerating the size enlargement process. The phospholipid exchange process explained in terms of a diminished hydrophobic attraction among the phospholipid molecules of the bilayer occurs via a free phospholipid molecule transfer through the aqueous phase. The size enlargement process is interpreted in terms of high fatty acid concentration in the membrane fluid domains. The membrane structure is locally perturbed inducing vesicle sticking after collision.

Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1977

Cation translocation across the membrane of cytochrome oxidase reconstituted vesicles may be foll... more Cation translocation across the membrane of cytochrome oxidase reconstituted vesicles may be followed with a simple spectrophotometric method. Cytochrome oxidase reconstituted vesicles, supplemented with ascorbate and cytochrome c, induce large spectral changes of the positive dye safranine, reversed by uncouplers and inhibitors of respiration. The dye is probably accumulated in the inner space of the vesicles, where it reaches high concentrations and aggregates. The spectral shifts and the absorbance changes, due to aggregation, are proportional to the amount of the dye taken up and depend on the respiratory control. In the presence of potassium, valinomycin causes an inhibition, whereas nigericin stimulates the dye uptake. The data are discussed in terms of electrical potential dependent fluxes.

Biochimica et Biophysica Acta (BBA) - Bioenergetics, 1978

The correlation between A~H, the proton electrochemical potential difference, and the rate of con... more The correlation between A~H, the proton electrochemical potential difference, and the rate of controlled respiration is analyzed. ApH (the proton concentration gradient) is measured on the distribution of [3H]acetate, and A~ (the membrane potential) on the distribution of 86Rb +, 4SCa2+ and [3H]triphenylmethylphosphonium used either alone or simultaneously. The effects of the addition of ADP + hexokinase (state-3 ADP) and of carbonylcyanide trifluoromethoxyphenylhydrazone (state-3 uncoupler) on respiration and A~H are not equivalent: the uncoupler depresses A/~H more than ADP at equivalent respiratory rates. The effects of the additions of nigericin-valinomycin and of ionophore A23187 (state-3 cation transport) and of carbonylcyanide trifluoromethoxyphenylhydrazone (state 3-uncoupler) on respiration and A~H are also not equivalent: the uncoupler depresses A~H more than A23187 and nigericin + valinomycin at equivalent respiratory rate. A23187 is very efficient in stimulating respiration with negligible Ap H changes.

American Journal of Physiology-Renal Physiology, 2009

Development of the mitochondrial permeability transition (MPT) can importantly contribute to leth... more Development of the mitochondrial permeability transition (MPT) can importantly contribute to lethal cell injury from both necrosis and apoptosis, but its role varies considerably with both the type of cell and type of injury, and it can be strongly opposed by the normally abundant endogenous metabolites ADP and Mg2+. To better characterize the MPT in kidney proximal tubule cells and assess its contribution to injury to them, we have refined and validated approaches to follow the process in whole kidney proximal tubules and studied its regulation in normoxic tubules and after hypoxia-reoxygenation (H/R). Physiological levels of ADP and Mg2+greatly decreased sensitivity to the MPT. Inhibition of cyclophilin D by cyclosporine A (CsA) effectively opposed the MPT only in the presence of ADP and/or Mg2+. Nonesterified fatty acids (NEFA) had a large role in the decreased resistance to the MPT seen after H/R irrespective of the available substrate or the presence of ADP, Mg2+, or CsA, but r...