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Title: Living at a snail's pace : the cellular basis of metabolic depression
Author: Bishop, T.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2002
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The garden snail Helix aspersa depresses its metabolic rate in response to desiccation (termed aestivation), as well as in response to reduced oxygen tension (termed oxygen conformation). This depression persists in cells isolated from the hepatopancreas of snails, thereby providing a good model system for analysing the cellular basis of metabolic depression. Isolated hepatopancreas cells were used to assess the contributions of various cellular processes (non-mitochondrial and mitochondrial respiration, and, within mitochondrial respiration, substrate oxidation and respiration to drive proton leak and ATP turnover) to metabolic depression seen during oxygen conformation and aestivation. Non-mitochondrial respiration accounts for a large proportion (~50%) of metabolic rate at physiological oxygen tensions, and it is solely responsible for the oxygen conforming behaviour of the cells. Both non-mitochondrial and mitochondrial respiration, however, decrease in aestivation. This decrease in mitochondrial respiration is not caused by differences in mitochondrial volume or inner membrane surface density but is associated with other intrinsic changes in the mitochondria (decrease in the activities of the mitochondrial enzymes citrate synthase and cytochrome c oxidase). Within mitochondrial respiration, the activity of substrate oxidation and probably ATP turnover, but not the activity of proton leak, decrease during aestivation. At least 75% of the total response of mitochondrial respiration to aestivation is due to primary changes in the kinetics of substrate oxidation, with only 25% or less of the response occurring through primary effects on ATP turnover. The primary change in the activity of substrate oxidation resulted in a lower mitochondrial membrane potential in hepatopancreas cells from aestivating compared to active snails, leading to secondary decreases in respiration to drive ATP turnover and proton leak.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available