Biomedical subjects

N Corona

Publications and source records attributed to N Corona.

9 recordsLinked to original sources

PubMed1995

Modulation of 2-oxoglutarate dehydrogenase and oxidative phosphorylation by Ca2+ in pancreas and adrenal cortex mitochondria.

The effect of external free Ca2+ ([Ca2+]ex) on the 2-oxoglutarate dehydrogenase (2-OGDH) activity and the rate of state 3 respiration was studied in dog pancreas and adrenal cortex mitochondria. A method for the preparation of mitochondria from pancreas, free of zymogen granules, was developed. The mitochondria showed high respiratory control values and maintained adequate ADP/O ratios in the course of several hours. Half-maximal stimulation (K0.5) of 2-OGDH activity and state 3 respiration by Ca2+ was decreased twofold by spermine, in both pancreas and adrenal cortex mitochondria incubated with Mg2+; Na+ increased the K0.5 value for Ca2+ in both kinds of mitochondria. The matrix Ca2+ content was enhanced by spermine at different [Ca2+]ex. The Ca2+ gradient ([Ca2+]m/[Ca2+]ex) determined in Fluo 3-loaded pancreas mitochondria was found to be below 1, either in the presence of Na+ or in the absence of spermine. The protonmotive force was increased by 1 microM Ca2+, in state 3 conditions, by 6-8 mV; lower Ca2+ concentrations kept the H+ gradient rather constant. An increase in the spermine/Mg2+ ratio at constant external Ca2+ resulted in stimulation of the 2-OGDH activity and state 3 respiration. The data indicate that matrix Ca2+ may regulate the rate of ATP synthesis in pancreas and adrenal cortex mitochondria, through the modulation of 2-OGDH and the maintenance of a high H+ gradient. In addition to changes in external Ca2+, the variation in the spermine/Mg2+ ratio may also exert control of oxidative phosphorylation.

Adrenal Cortex↗

PubMed1994

Triphenyltin as inductor of mitochondrial membrane permeability transition.

The effect of triphenyltin on mitochondrial Ca2+ content was studied. It was found that this trialkyltin compound induces an increase in membrane permeability that leads to Ca2+ release, drop of the transmembrane potential, and efflux of matrix proteins. Interestingly, cyclosporin A was unable to inhibit triphenyltin-induced Ca2+ release. Based on these results it is proposed that the hyperpermeable state is produced by modification of 2.25 nmol of membrane thiol groups.

Animals↗

PubMed1994

The effect of cyclosporin A on Hg(2+)-poisoning mitochondria. In vivo and in vitro studies.

The protective effect of cyclosporin A on the damage induced by Hg2+ in kidney mitochondria was studied. Cyclosporin, added in vitro at a concentration of 0.5 microM, reversed the deleterious effects of Hg2+ on transmembrane potential and Ca2+ accumulation. However, when injected in rats, together with Hg2+, cyclosporin failed to protect against Hg2+ poisoning. Due to the low activity of cyclophilin found in kidney mitchondria, it is proposed that the protection of cyclosporin in vitro must be exerted through an independent mechanism different from its binding to cyclophilin.

Amino Acid Isomerases↗

PubMed1994

On the role of ADP to increase the inhibitory effect of cyclosporin on mitochondrial membrane permeability transition.

This work reports an investigation which demonstrate that the addition of ADP is necessary to attain the protective effect of cyclosporin on the carboxyatractyloside-induced mitochondrial Ca2+ release. Evidence are presented which indicate that the effect of ADP is exerted by increasing the inhibitory action of cyclosporin on the enzyme cyclophilin.

Adenosine Diphosphate↗

PubMed1993

Subunit structures of purified beef mitochondrial cytochrome bc1 complex from liver and heart.

The existence of tissue-specific isozymes of cytochrome c oxidase has been widely documented. We have now studied if there are differences between subunits of mitochondrial bc1 complexes isolated from liver and heart. For this purpose, we have developed a method for the purification of an active ubiquinol-cytochrome c oxidoreductase from adult bovine liver that includes solubilization of submitochondrial particles with deoxycholate, ammonium acetate fractionation, resolubilization with dodecyl maltoside, and ion exchange chromatography. The electrophoretic pattern of the liver preparation showed the presence of 11 subunits, with apparent molecular weights identical to the ones reported for the heart complex. Western blot analysis and isoelectric focusing followed by two-dimensional gels of bc1 complexes from liver and heart were compared, and no qualitative differences were observed. In addition, the high-molecular-weight subunits of the purified complexes from both tissues, subunits I, II, V, and VI, were isolated by PAGE in the presence of Coomasie Blue and subjected to limited proteolysis and to chemical digestion with cyanogen bromide and BNPS-skatol, and the peptide patterns were compared. Finally, two of the small-molecular-weight subunits from the liver complex were isolated (subunits VII and X), partially analyzed by amino terminal sequencing, and found to be identical with the reported sequence of their heart counterparts. The data suggest that, in contrast to the case of cytochrome c oxidase, bc1 complexes from liver and heart do not exhibit tissue-specific differences.

Amino Acid Sequence↗

PubMed1993

Ionophoretic-like properties of ketorolac for calcium.

Ketorolac is an analgesic drug known to induce its therapeutic effect by inhibiting prostaglandin synthesis. In this work we introduce the nonsteroidal antialgesic drug as a compound with ionophoretic properties for calcium ions, showing that ketorolac induces mitochondrial Ca++ release. This reaction did not depend on an uncoupler-like action, because the drug does not collapse the internal negative membrane potential nor does it affect oxidative phosphorylation. In addition, it is shown that ketorolac ferries calcium ions into energized liposomes and has a hydrophobic phase with an affinity constant of 4 x 10(-3). The therapeutic action of ketorolac is related to its ionophoretic properties in addition to its well known inhibitory effect on the cyclooxygenase enzyme.

Animals↗

PubMed1992

Fluorescamine-induced membrane permeability in mitochondria.

1. Addition of fluorescamine (75 microM) to mitochondria induced an increase in membrane permeability. 2. The leakiness of the inner mitochondrial membrane is characterized by extensive release of accumulated Ca2+, collapse of the transmembrane potential, mitochondrial swelling and efflux of matrix proteins, among them, malate dehydrogenase. 3. These effects were diminished by supplementing the media with 1 mM phosphate, and partially prevented by Mg2+. 4. These results indicate that the primary amino groups of membrane components contribute, partially, to the maintenance of the permeability barrier in mitochondria.

Animals↗

PubMed1991

Distribution of control of oxidative phosphorylation in mitochondria oxidizing NAD-linked substrates.

The flux control distribution of the net rate of state 3 respiration was determined in heart and kidney mitochondria incubated with low concentrations of pyruvate (0.5 mM) or 2-oxoglutarate (1 mM), and in conditions that led to activation of NAD-linked dehydrogenases, i.e., high substrate or Ca2+ concentrations. Control of flux was exerted by the ATP/ADP carrier (flux control coefficient, ci = 0.37) and Site 1 of the respiratory chain (ci = 0.28) when dehydrogenase activity was low. Control of the process shifted to the ATP synthase (ci = 0.32) and the Pi carrier (Ci = 0.27) when dehydrogenases were activated by high pyruvate and high Ca2+. The changes in the control exerted by the ATP/ADP carrier and the ATP synthase were not due to changes in the transmembrane potential, nor to a modification of intramitochondrial ATP/ADP ratios. Applying the summation theorem of the control analysis, it was found that at low Ca2+ and pyruvate concentrations the dehydrogenases shared the control of state 3 respiration with other steps. The NAD-linked dehydrogenases did not exert any significant control at high Ca2+ or high pyruvate concentrations.

Animals↗

PubMed1990

[Preparation and analysis of dehydrated mixtures of vegetables and underutilized fish species flours: I. Dehydrated mixtures of cereal-fish].

For the purpose of providing possible solutions to the malnutrition problems affecting those populations where cereals and tubers form an important portion of their daily intake, products were prepared from dehydrated mixtures of cereals and under-utilized fish, but which contain high-quality protein. Two cereals were selected for our experiments: rice and corn, and a marine under-utilized fish species (Macrodon ancyclodon). The minced fish muscle recovered by mechanical deboning was mixed with the cereal, obtaining mixtures with 5%, 10% and 15% fish on a dry basis. Feeding experiments using Wistar weaning rats were then carried out to evaluate the most important characteristics. An amino acid profile which reflected high-quality protein was obtained, as evidenced by the excellent PER, NPU, NPR and digestibility values determined. The dehydrated mixtures of fish/cereal flour prepared with 5% and up to 10% fish (dry basis), did not present any odour, but as of the 15% level, fish odour was perceived. Therefore, the use of dehydrated mixtures of fish/cereal flours with up to 10% fish in preparing food products, is recommended, since these would be of great help in solving the scarcity of good-quality protein, particularly in the developing countries.

Amino Acids, Essential↗