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1.
Indian J Biochem Biophys ; 1995 Feb; 32(1): 1-10
Artículo en Inglés | IMSEAR | ID: sea-27198

RESUMEN

The high osmotic potential inhibition of photosynthetic electron transport was determined to be related to membrane compaction rather than to an effect of primary thylakoid volume changes. Osmotic inhibition of proton fluxes and phosphorylation were entirely due to osmotic inhibition of electron transport. The ATPase activity, the nature of coupling and the rate constant of proton efflux were not influenced by osmotic pressure, while the rate constant and the extent of proton influx were inhibited by osmotic pressure.


Asunto(s)
Medios de Cultivo , Transporte de Electrón , Orgánulos , Concentración Osmolar , Pisum sativum/metabolismo , Fotofosforilación , Fotosíntesis , Protones
2.
Indian J Biochem Biophys ; 1992 Apr; 29(2): 103-14
Artículo en Inglés | IMSEAR | ID: sea-28883

RESUMEN

Metabolically-induced (spontaneous) high amplitude swelling of mitochondria has been shown to be due to a serial disruption of the mitochondrial membranes [D. Sambasivarao & V. Sitaramam (1985), Biochim Biophys Acta, 806, 195-209]. Phosphate- and arsenate-induced swelling was investigated in mitochondria to evaluate the role of phosphate transport in the instability created in the mitochondrial membranes. Phosphate-induced swelling in respiring mitochondria was similar to spontaneous swelling. Both represent essentially colloidal swelling due to the variable porosity induced in the inner membrane to polyols by respiration. Swelling of non-respiring mitochondria at high ammonium phosphate concentrations was, on the other hand, primarily due to high permeability to phosphate. This membrane instability created by phosphate transport in the surrounding lipid involves neither the endogenous nor the exogenous Ca2+.


Asunto(s)
Animales , Membranas Intracelulares/efectos de los fármacos , Manitol/farmacología , Mitocondrias Hepáticas/fisiología , Dilatación Mitocondrial/efectos de los fármacos , Consumo de Oxígeno , Fosfatos/metabolismo , Ratas , Sacarosa/farmacología
3.
Indian J Biochem Biophys ; 1991 Oct-Dec; 28(5-6): 401-7
Artículo en Inglés | IMSEAR | ID: sea-28898

RESUMEN

Effects of pH, temperature, ionic strength and osmotic pressure on various respiratory states and indices of oxidative phosphorylation in well coupled rat liver mitochondria have been studied. It appears that temperature and osmotic pressure are the most important physical variables, whereas ionic strength and pH were devoid of any significant influence on oxidative phosphorylation. Thus any model for oxidative phosphorylation must critically account for the differential osmotic sensitivity of respiration as well as the curious fact that ADP/O ratio increases as temperature decreases.


Asunto(s)
Animales , Mitocondrias Hepáticas/metabolismo , Presión Osmótica , Fosforilación Oxidativa , Ratas , Temperatura
4.
Artículo en Inglés | IMSEAR | ID: sea-28348

RESUMEN

Rotenone-sensitive, uncoupler-insensitive, NADH-dependent respiration was demonstrated in osmotically inactive fragments of the mitochondrial inner-membrane obtained following high amplitude (spontaneous) swelling. This NADH-dependent respiration as well as mitochondrial ATPase activity was stimulated by ligands which are known to be transported by specific transporters/mechanisms. The ligands capable of this anomalous respiratory control included several intermediates of the citric acid cycle, besides non-metabolizable ligands including lactate, cations such as K+ and Ca2+. The interaction between NADH-dependent respiration and these ligands, as manifested by stimulation of respiration, was strongly ionic strength-dependent. The thermodynamic relationship between respiratory control and stimulation of transport ATPase by the relevant transportable ligands could also be demonstrated in the conventional (rat liver) microsomes. These experimental results offer a novel experimental base for search into an intra-membranous mechanism of energy transduction.


Asunto(s)
Animales , Transporte Biológico Activo , Mitocondrias Hepáticas/metabolismo , Dilatación Mitocondrial , NAD/metabolismo , Ósmosis , Consumo de Oxígeno , Fosforilación , Ratas , Ratas Endogámicas
5.
Indian J Biochem Biophys ; 1991 Aug; 28(4): 280-90
Artículo en Inglés | IMSEAR | ID: sea-28126

RESUMEN

Metabolically induced high amplitude swelling of rat liver mitochondria has been found to result in the formation of a heterogeneous population of mitochondrial membranes consisting of right side-out particles with occluded fumarase activity and inside-out particles/fragments capable of NADH-dependent respiration. This rotenone-sensitive, uncoupler-insensitive, NADH-dependent respiration was specifically and instantaneously stimulated by several ligands such as glutamate and malate (which can be metabolized) and, interestingly, even lactate (which could not be metabolized by the swollen mitochondria). These observations suggest that high amplitude swelling results in a novel type of control of respiration in these fragments.


Asunto(s)
Animales , Ácidos Carboxílicos/farmacología , Membranas Intracelulares/metabolismo , Mitocondrias Hepáticas/efectos de los fármacos , Dilatación Mitocondrial , NAD/metabolismo , Consumo de Oxígeno/efectos de los fármacos , Ratas , Ratas Endogámicas
6.
J Biosci ; 1990 Sep; 15(3): 135-141
Artículo en Inglés | IMSEAR | ID: sea-160786

RESUMEN

Lysis of erythrocytes offers an unique opportunity to probe the fine structure of the bilayer as a function of its state of energization. Critical monitoring of the volumes, ion fluxes and related measures in erythrocytes exposed to a variety of milieu and treatments showed that one can critically distinguish the nature of the prelytic perturbations and the proximate forces actually responsible for the disruption of the membranes among surface charge density, elastic energy etc.

9.
J Biosci ; 1987 Mar; 11(1-4): 89-105
Artículo en Inglés | IMSEAR | ID: sea-160508

RESUMEN

Isotonic requirements for synaptosomes were shown to vary with the concentration of sucrose or mannitol in the isolation medium, as well as with their differential permeability to polyols and ions. The technique of enzyme osmometry, which permits quantitation of the osmotic integrity in a heterogeneous population, was used to defined the osmotic requirements for synaptosomes and myelosomes in a variety of ionic and nonelectrolyte media. Important differences, observed in the rank order of permeability of synaptosomal and myelosomal membranes to electrolyte media, were consistent with the known channel density/electrical activity of the corresponding plasma membranes.

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