Arrhenius parameters of mitochondrial membrane respiratory enzymes in relation to thermoregulation in endotherms

Geiser, Fritz; McMurchie, Edward J.

doi:10.1007/bf00694585

“…Instead of the positive link between metabolism and ROS production, the decrease in body temperature might itself explain the differences in oxidative damage levels between the age groups, since enzyme functioning and the relative antioxidant activity are highly affected by temperature (Hove and Hove, 1944;Geiser and McMurchie, 1985;Elias et al, 2014). Enzyme functioning and the antioxidant activity may be different between the age classes as old birds showed the most pronounced drop in body temperature during rest-phase hypothermia compared to more moderate responses of young and middle-aged birds.…”

Section: Mean Night-time Body Temperature Indicative For Continuous Dmentioning

confidence: 99%

Rest-Phase Hypothermia Reveals a Link Between Aging and Oxidative Stress: A Novel Hypothesis

Zagkle

¹

,

Grosiak

²

,

Bauchinger

³

et al. 2020

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In endotherms, growth, reproduction, and survival are highly depended on energy metabolism. Maintenance of constant body temperature can be challenging for endotherms under continuously changing environmental conditions, such as low or high ambient temperatures or limited food. Thus, many birds may drop body temperature below normothermic values during the night, known as rest-phase hypothermia, presumably to decrease energy metabolism. Under the assumption of the positive link between aerobic metabolism and reactive oxygen species, it is reasonable to suggest that low body temperature, a proxy of energy metabolism, will affect oxidative stress of the birds. Aging may considerably affect behavior, performance and physiology in birds and still requires further investigation to understand age-specific changes along the lifespan of the organism. Until today, age-specific rest-phase hypothermic responses and their effect on oxidant-antioxidant status have never been investigated. We exposed 25 zebra finches (Taeniopygia guttata) of three age classes, 12 young birds (1.1–1.3 years old), 8 middle-aged (2.4–2.8 years old), and 5 old birds (4.2–7.5 years old) to day-long food deprivation or provided them normal access to food under thermoneutral conditions. We compared night-time body temperature, measured through implanted data loggers, and quantified plasma oxidative status (uric acid, antioxidant capacity, and d-ROM assay) the following morning. We found age-related differences in night-time body temperature following a day-long food deprivation while all three age groups remained normothermic in the night following a day with access to food. The lowest minimum body temperature (LSM ± SE: 36.6 ± 0.2°C) was observed in old individuals during rest-phase hypothermia. Surprisingly, these old birds also revealed the highest levels of plasma oxidative damage, while young and middle-aged birds maintained higher night-time body temperature and showed lower values of oxidative damage. These results lead us to propose a novel hypothesis on how aging may lead to an accumulation of oxidative damage; the impaired physiological capacity to thermoregulate with advancing age does increase the risk of oxidative stress under challenging conditions. When energy is limited, the risk to encounter oxidative stress is increasing via a compensation to defend normothermic body temperatures.

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“…The plot is a curvature in reality and depends on the spatial-temporal heterogeneity of the process. Thus, the extrapolated straight line is incorrect in the vicinity of the transition, e.g., the binding of adenosine triphosphate (ATP) to myosin subfragment-1 (46,51) or measuring the cytochrome c reductase activity of liver mitochondrial succinate for the heterothermic brown antechinus (57,58).…”

Section: The Thermal Effectmentioning

confidence: 99%

Oncological hyperthermia: The correct dosing in clinical applications

Lee

¹

,

Szigeti

²

,

Szász

³

2018

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The problem with the application of conventional hyperthermia in oncology is firmly connected to the dose definition, which conventionally uses the concept of the homogeneous (isothermal) temperature of the target. Its imprecise control and complex evaluation is the primary barrier to the extensive clinical applications. The aim of this study was to show the basis of the problems of the misleading dose concept. A clear clarification of the proper dose concept must begin with the description of the limitations of the present doses in conventional hyperthermia applications. The surmounting of the limits the dose of oncologic hyperthermia has to be based on the applicability of the Eyring transition state theory on thermal effects. In order to avoid the countereffects of thermal homeostasis, the use of precise heating on the nanoscale with highly efficient energy delivery is recommended. The nano-scale heating allows for an energy-based dose to control the process. The main aspects of the method are the following: i) It is not isothermal (no homogeneous heating); ii) malignant cells are heated selectively; and iii) it employs high heating efficacy, with less energy loss. The applied rigorous thermodynamical considerations show the proper terminology and dose concept of hyperthermia, which is based on the energy-absorption (such as in the case of ionizing radiation) instead of the temperature-based ideas. On the whole, according to the present study, the appropriate dose in oncological hyperthermia must use an energy-based concept, as it is well-known in all the ionizing radiation therapies. We propose the use of Gy (J/kg) in cases of non-ionizing radiation (hyperthermia) as well.

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Temperature Relationships: From Molecules to Biogeography

Somero¹

1997

Comprehensive Physiology

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The sections in this article are: Temperature Effects on Physiological, Biochemical, and Molecular Systems: Basic Considerations Temperature Effects on Proteins Determinants of Thermal Sensitivities of Protein Structure and Function Protein Structural Stability and Adaptation Temperature Adaptations in Enzyme Kinetic Properties Lead to Conservation of Metabolic Regulation and Rate of Function Rate Compensation to Temperature Through Alterations in Enzyme Concentration The Heat Shock Response Molecular Chaperones: Assistants in Protein Folding, Compartmentation, and Renaturation The Heat Shock Response and Induced Thermal Tolerance Acclimatization‐Induced Differences in the Heat Shock Response Interindividual and Intertissue Differences in the Heat Shock Response Evolutionary, Interspecific Differences in the Heat Shock Response Cellular Thermometers and Regulation of HSP Synthesis Cold Shock May Induce Stress Proteins Temperature Effects on Lipids and Membrane‐Localized Functions Temperature Effects on Membrane Lipids: Changes in Phase and Fluidity Membrane Fluidity and Compositional Changes Correlate With Effects on Membrane Functions Homeoviscous Adaptation: Occurrence and Efficacy Adaptation of Membrane Lipids: Regulation and Biophysical Effects Adaptive Regulation of Depot and Membrane Lipid Fluidity in Hibernators Membrane Lipids of Thermophilic Archaebacteria Membrane Adaptations Involving Extrinsic Factors: pH and Solutes Cuticular Waxes: Regulation of Body Temperature and Control of Water Loss Evaporative Cooling in Insects Temperature–pH Interactions Temperature Dependence of Body Fluid pH Values The Imidazole Alphastat Hypothesis Functional Manifestations of the Advantages of Alphastat Regulation Deviations from Alphastat Regulation in Small Mammalian Hibernators Variation in Alpha Imidazole among Species, Tissues, Histidyl Residues, and Methodologies Biogeographical Implications of Temperature Adaptation

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Arrhenius parameters of mitochondrial membrane respiratory enzymes in relation to thermoregulation in endotherms

Cited by 9 publications

References 30 publications

Rest-Phase Hypothermia Reveals a Link Between Aging and Oxidative Stress: A Novel Hypothesis

Rest-Phase Hypothermia Reveals a Link Between Aging and Oxidative Stress: A Novel Hypothesis

Oncological hyperthermia: The correct dosing in clinical applications

Temperature Relationships: From Molecules to Biogeography

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