Mitochondrial resistance to massive irradiation in vivo

Romani, Roger J.; Fisher, L.K.

doi:10.1016/0003-9861(66)90106-8

Cited by 10 publications

(3 citation statements)

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“…Early postulates were premised on the notion that mitochondrial respiration increased during the climacteric in compensation for declining mitochondrial efficiency, with the latter attributed to either phosphorylative uncoupling (20) or the interposition of the energy-inefficient alternative electron transport pathway (37). These postulates gave way to subsequent evidence that mitochondria remain energy-efficient throughout the respiratory climacteric (16), and that the alternative pathway, though present, remains unengaged (39).Based on the growing perception that mitochondria are quasi-autonomous and on evidence (34,35) of mitochondrial repair in situ, it has been proposed (29) that the respiratory climacteric may represent the mitochondria's own maintenance metabolism. The postulate calls for mitochondria that have a capacity for self-maintenance and self-restoration.…”

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Metabolically Driven Self-Restoration of Energy-Linked Functions by Avocado Mitochondria

Huang¹,

Romani²

1991

Plant Physiol.

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To assess the restorative capacity of isolated avocado (Persea americana) fruit mitochondria, the organelles were first aged in the absence of an energy source at 250C for several hours until respiratory control and oxidative phosphorylation were greatly diminished or totally lost. Energy-linked functions were then gradually restored over a period of several hours after the addition of substrate. Restoration of respiratory control resulted from both an increase in state 3 and a decrease in state 4 respiratory rates. Either a-ketoglutarate or succinate served as restorants, each with distinctive rates of recovery in state 3 and state 4 respiration. ATP also served as a restorative agent but not as effectively as metabolizable substrate. ATP synthase activity was modulated by stress and restoration but neither the extent nor the rate of change was sufficient to constrain state 3 rates. Orthophosphate was released from the mitochondria during substrate-deprived stress. Restoration of phosphorylation preceded that of RC with phosphate uptake and phosphorylation being evident immediately upon the addition of substrate. During restoration [32P]orthophosphate was incorporated into several organic fractions: phospholipid, ATP, a trichloroacetic acid-precipitable mitochondrial fraction, and an organophosphate that accumulated in the medium in relatively large amounts. The organophosphate was tentatively identified as a hexosephosphate. Incorporation into ATP and the putative hexosephosphate continued unabated beyond the point of maximum restoration. Phosphate metabolism thus appears to be a necessary but not sufficient precondition for mitochondrial restoration and maintenance. Based on the recovery kinetics of the various phosphorylated components, the mitochondrial-bound fraction appears to be most directly linked with restoration. Results are discussed with reference to specific characteristics and components of selfrestoration and to possible underlying mechanisms. We suggest that a degree of self-restoration is consistent with the quasiautonomous nature of mitochondria and that this intrinsic capacity may be pivotal to the respiratory climacteric in senescent fruit cells and to cellular homeostasis in general.of mitochondria in the climacteric respiratory rise that accompanies the senescence of many fruit and other plant organs. Decades later it is still generally held that the respiratory climacteric has mitochondrial origins but causal relationships remain unresolved. Early postulates were premised on the notion that mitochondrial respiration increased during the climacteric in compensation for declining mitochondrial efficiency, with the latter attributed to either phosphorylative uncoupling (20) or the interposition of the energy-inefficient alternative electron transport pathway (37). These postulates gave way to subsequent evidence that mitochondria remain energy-efficient throughout the respiratory climacteric (16), and that the alternative pathway, though present, remains unengaged (39).Based on the ...

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confidence: 99%

“…Based on the growing perception that mitochondria are quasi-autonomous and on evidence (34,35) of mitochondrial repair in situ, it has been proposed (29) that the respiratory climacteric may represent the mitochondria's own maintenance metabolism. The postulate calls for mitochondria that have a capacity for self-maintenance and self-restoration.…”

mentioning

confidence: 99%

Metabolically Driven Self-Restoration of Energy-Linked Functions by Avocado Mitochondria

Huang¹,

Romani²

1991

Plant Physiol.

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“…The impact of increased senescence on the mitochondrial yield is illustrated in figure 2. In contrast to preclimacteric pears (fig 2A), only minor changes in mitochondrial yield were noted following irradiation at or near the climacteric peak ( fig 2B) (36). The basic assumption in "split-dose" experiments is that repair, or reconstitution, must have occurred in the interval between dose increments when the overall radiation tolerance is increased (4 (.)…”

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Cellular Senescence, Radiation Damage to Mitochondria, and the Compensatory Response in Ripening Pear Fruits

Romani¹,

Yu²,

Ku³

et al. 1968

Plant Physiol.

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It is generally accepted that the climacteric phase of ripening fruits is well suited for the study of cellular senescence (1). Since a surge in respiratory activity is the dominant, readily measurable phenomenon, mitochondria are implicated as the sites of causal events. This view was embodied in the early work of Millerd et al. (19) with the resulting postulate that uncoupling of oxidative phosphorylation permitted an increased respiratory rate. Along similar lines, Hulme (7) and Pearson and Robertson (21) attributed the rise in respiration to the availability of phosphate acceptor (ADP) resulting from increased protein synthesis and accelerated demands for energy. However, with specific reference to mitochondrial protein, data on the yield of particulate protein (27) and on the incorporation of amino acids into mitochondrial protein (28) indicate a decline in synthetic activities as fruit reach the climacteric peak.Richmond and Biale (23), Sacher (37), and especially Young and Biale (44) have questioned the prevalence of "uncoupling" or "ADP control" in ripening fruit cells. Moreover, the work of Lance et al. (10), Hulme et al. (8,9) and the experiments reported below, reveal that mitochondria remain functionally sound and "cotipled" throughout the climacteric phase.

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