Bioenergetic Balance Research Articles

Thermodynamics constrains allometric scaling of optimal development time in insects.

Development time is a critical life-history trait that has profound effects on organism fitness and on population growth rates. For ectotherms, development time is strongly influenced by temperature and is predicted to scale with body mass to the quarter power based on 1) the ontogenetic growth model of the metabolic theory of ecology which describes a bioenergetic balance between tissue maintenance and growth given the scaling relationship between metabolism and body size, and 2) numerous studies, primarily of vertebrate endotherms, that largely support this prediction. However, few studies have investigated the allometry of development time among invertebrates, including insects. Abundant data on development of diverse insects provides an ideal opportunity to better understand the scaling of development time in this ecologically and economically important group. Insects develop more quickly at warmer temperatures until reaching a minimum development time at some optimal temperature, after which development slows. We evaluated the allometry of insect development time by compiling estimates of minimum development time and optimal developmental temperature for 361 insect species from 16 orders with body mass varying over nearly 6 orders of magnitude. Allometric scaling exponents varied with the statistical approach: standardized major axis regression supported the predicted quarter-power scaling relationship, but ordinary and phylogenetic generalized least squares did not. Regardless of the statistical approach, body size alone explained less than 28% of the variation in development time. Models that also included optimal temperature explained over 50% of the variation in development time. Warm-adapted insects developed more quickly, regardless of body size, supporting the “hotter is better” hypothesis that posits that ectotherms have a limited ability to evolutionarily compensate for the depressing effects of low temperatures on rates of biological processes. The remaining unexplained variation in development time likely reflects additional ecological and evolutionary differences among insect species.

Pulsing of Membrane Potential in Individual Mitochondria: A Stress-Induced Mechanism to Regulate Respiratory Bioenergetics in Arabidopsis

Mitochondrial ATP synthesis is driven by a membrane potential across the inner mitochondrial membrane; this potential is generated by the proton-pumping electron transport chain. A balance between proton pumping and dissipation of the proton gradient by ATP-synthase is critical to avoid formation of excessive reactive oxygen species due to overreduction of the electron transport chain. Here, we report a mechanism that regulates bioenergetic balance in individual mitochondria: a transient partial depolarization of the inner membrane. Single mitochondria in living Arabidopsis thaliana root cells undergo sporadic rapid cycles of partial dissipation and restoration of membrane potential, as observed by real-time monitoring of the fluorescence of the lipophilic cationic dye tetramethyl rhodamine methyl ester. Pulsing is induced in tissues challenged by high temperature, H(2)O(2), or cadmium. Pulses were coincident with a pronounced transient alkalinization of the matrix and are therefore not caused by uncoupling protein or by the opening of a nonspecific channel, which would lead to matrix acidification. Instead, a pulse is the result of Ca(2+) influx, which was observed coincident with pulsing; moreover, inhibitors of calcium transport reduced pulsing. We propose a role for pulsing as a transient uncoupling mechanism to counteract mitochondrial dysfunction and reactive oxygen species production.

Creatine Protects against Excitoxicity in an In Vitro Model of Neurodegeneration

Creatine has been shown to be neuroprotective in aging, neurodegenerative conditions and brain injury. As a common molecular background, oxidative stress and disturbed cellular energy homeostasis are key aspects in these conditions. Moreover, in a recent report we could demonstrate a life-enhancing and health-promoting potential of creatine in rodents, mainly due to its neuroprotective action. In order to investigate the underlying pharmacology mediating these mainly neuroprotective properties of creatine, cultured primary embryonal hippocampal and cortical cells were challenged with glutamate or H2O2. In good agreement with our in vivo data, creatine mediated a direct effect on the bioenergetic balance, leading to an enhanced cellular energy charge, thereby acting as a neuroprotectant. Moreover, creatine effectively antagonized the H2O2-induced ATP depletion and the excitotoxic response towards glutamate, while not directly acting as an antioxidant. Additionally, creatine mediated a direct inhibitory action on the NMDA receptor-mediated calcium response, which initiates the excitotoxic cascade. Even excessive concentrations of creatine had no neurotoxic effects, so that high-dose creatine supplementation as a health-promoting agent in specific pathological situations or as a primary prophylactic compound in risk populations seems feasible. In conclusion, we were able to demonstrate that the protective potential of creatine was primarily mediated by its impact on cellular energy metabolism and NMDA receptor function, along with reduced glutamate spillover, oxidative stress and subsequent excitotoxicity.

Delayed Preconditioning by Sevoflurane Elicits Changes in the Mitochondrial Proteome in Ischemia-Reperfused Rat Hearts

Delayed myocardial preconditioning by volatile anesthetics involves changes in DNA transcription and translation. Mitochondria play a central role in myocardial ischemia/reperfusion (I/R) injury and in ischemic or pharmacologic preconditioning. In this study, we investigated whether there are alterations in myocardial mitochondrial protein expression after volatile anesthetic preconditioning (APC) to examine the underlying mechanisms of delayed cardioprotection. Thirty-six Sprague-Dawley rats were randomly assigned to 1 of 3 groups (n = 12 for each group). Rats in the delayed APC group were exposed to sevoflurane (2.5% for 60 minutes) 24 hours before myocardial ischemia was induced. Myocardial ischemia in the I/R and APC groups was induced by left coronary artery occlusion for 30 minutes, followed by 120 minutes of reperfusion. The control group received no treatment. The mitochondria fractions were prepared by differential centrifugation with density gradient isolation for proteomic analysis. Two-dimensional gel electrophoresis and matrix-assisted laser desorption/ionization with time-of-flight mass spectrometry was used to identify differences in the protein expression from mitochondria of the rat hearts. Fifteen differentially expressed mitochondrial proteins between the APC group and I/R group were identified and the expression patterns of 2 of the proteins were confirmed by Western blot analysis. These proteins were associated with mitochondrial substrate metabolism, respiration, and adenosine triphosphate (ATP)/adenosine diphosphate transport. The modifications of the mitochondrial proteome suggest an enhanced capacity of mitochondria to maintain myocardial ATP levels after I/R injury. Delayed sevoflurane myocardial preconditioning induces mitochondrial proteome remodeling, which mainly involves proteins that are related to ATP generation and transport. Therefore, proteomic changes related to bioenergetic balance may be the mechanistic basis of delayed anesthetic myocardial preconditioning.

Age-associated changes in synaptic lipid raft proteins revealed by two-dimensional fluorescence difference gel electrophoresis

Brain aging is associated with a progressive decline in cognitive function though the molecular mechanisms remain unknown. Functional changes in brain neurons could be due to age-related alterations in levels of specific proteins critical for information processing. Specialized membrane microdomains known as 'lipid rafts' contain protein complexes involved in many signal transduction processes. This study was undertaken to determine if two-dimensional fluorescence difference gel electrophoresis (2D DIGE) analysis of proteins in synaptic membrane lipid rafts revealed age-dependent alterations in levels of raft proteins. Five pairs of young and aged rat synaptic membrane rafts were subjected to DIGE separation, followed by image analysis and identification of significantly altered proteins. Of 1046 matched spots on DIGE gels, 94 showed statistically significant differences in levels between old and young rafts, and 87 of these were decreased in aged rafts. The 41 most significantly altered (p<0.03) proteins included several synaptic proteins involved in energy metabolism, redox homeostasis, and cytoskeletal structure. This may indicate a disruption in bioenergetic balance and redox homeostasis in synaptic rafts with brain aging. Differential levels of representative identified proteins were confirmed by immunoblot analysis. Our findings provide novel pathways in investigations of mechanisms that may contribute to altered neuronal function in aging brain.

Hepatitis C virus protein expression causes calcium-mediated mitochondrial bioenergetic dysfunction and nitro-oxidative stress

Hepatitis C virus (HCV) infection induces a state of oxidative stress that is more pronounced than that in many other inflammatory diseases. In this study we used well-characterized cell lines inducibly expressing the entire HCV open-reading frame to investigate the impact of viral protein expression on cell bioenergetics. It was shown that HCV protein expression has a profound effect on cell oxidative metabolism, with specific inhibition of complex I activity, depression of mitochondrial membrane potential and oxidative phosphorylation coupling efficiency, increased production of reactive oxygen and nitrogen species, as well as loss of the Pasteur effect. Importantly, all these effects were causally related to mitochondrial calcium overload, as inhibition of mitochondrial calcium uptake completely reversed the observed bioenergetic alterations. Expression of HCV proteins causes deregulation of mitochondrial calcium homeostasis. This event occurs upstream of further mitochondrial dysfunction, leading to alterations in the bioenergetic balance and nitro-oxidative stress. These observations provide new insights into the pathogenesis of hepatitis C and may offer new opportunities for therapeutic intervention.

Scio: Bioenergetische Hightech ermöglicht breit angelegte Diagnostik und darauf basierende Frequenztherapien

Die Scio-Therapie gehört ebenso wie die Homöopathie, die Akupunktur, die Bioresonanztherapie und andere Naturheilverfahren in den Bereich der Erfahrungsheilkunde. Als bioenergetisches Resonanzverfahren genießt es unter Ärzten und Heilpraktikern im deutschsprachigen Raum immer mehr Anerkennung. Scio misst die elektromagnetischen Schwingungen der einzelnen organischen Bestandteile des Körpers und stellt fest, inwieweit diese Schwingungen von Normwerten abweichen und damit die Ursachen für funktionelle Störungen im Körper sind. Da im Scio-System die elektromagnetischen Muster von rund 10 500 homöopathischen Substanzen gespeichert sind, kann es mit entsprechenden Frequenzen, die an dem Patienten appliziert werden, elektromagnetische Störungen ausgleichen und den Organismus in ein bioenergetisches Gleichgewicht bringen.

Changes in energy allocation by the predator Nephelopsis obscura exposed to differences in prey availability

Acquisition of energy and its allocation to components of bioenergetic balance were measured throughout the life cycle in three groups of Nephelopsis obscura fed one (low frequency), two (medium frequency), or three (high frequency) ad libitum meals each week at 15 and 20 °C. As feeding frequency increased, the total amounts of energy ingested, faeces plus mucus produced, somatic and reproductive growth, energy storage (total lipids), and respiration all increased. The proportion of ingested energy allocated to somatic and reproductive growth was highest for the medium-frequency and lowest for the low-frequency feeding treatment. Temperature had no effect on ingestion or faeces plus mucus production, but the respiration rate was higher and the growth rate lower at 20 than at 15 °C. The proportions of ingested energy allocated to growth and storage were the same in the high- and medium-frequency feeding treatments at both temperatures. In the low-frequency feeding treatment, the proportion of energy allocated to storage was higher at 15 °C, but proportionally more energy was allocated to somatic growth and less to reproductive growth or lipid storage at 20 °C. In the high- and medium-frequency feeding treatments, the relative amount of energy allocated to storage was constant, i.e., the ratio of reserves to structural tissues was the same, at both temperatures.

Maintenance of bioenergetic balance in sperm and prevention of lipid peroxidation: a review of the effect on design of storage preservation systems.

Effective use of encapsulated sperm requires careful review of: (a) the conditions under which the procedure can be effectively used; (b) assessment of the effect of storage conditions on sperm survival; (c) description of the environment of the female tract before, during and after capsule deposition; and (d) economic evaluation of impact and costs of the putative technology. Sperm survival depends on successful sustenance over two periods of storage (at subambient temperatures after collection and extension, then at body temperature when placed in the female tract) and one period of action (after release and until fertilization). The bioenergetic requirements of cauda epididymal and ejaculated bull and ram sperm are reviewed in terms of absolute ATP needs and are discussed in terms of storage needs. In addition, sperm inactivation by lipid peroxidation is discussed and suggestions are provided to minimize the process. Two general types of containers are possible. An open porous form allows free passage of nutrients and metabolic products; the entrapped sperm are thus subjected to the changing environment in the female tract. The other form is a sealed capsule that opens to release sperm before ovulation; it provides a sperm storage environment independent of female tract chemistry but introduces problems of nutrient supply and metabolite release. Potential experimental approaches to evaluate each type of system are discussed.

Cryopreservation of poultry sperm: The enigma of glycerol

This review summarizes recent data for cryopreservation of poultry sperm and data establishing the contraceptive effect of glycerol. Successful cryopreservation protocols for bovine sperm are compared to the requirements for rooster sperm, with emphasis on glycerol-induced alterations in avian reproductive systems. It has been shown that molar concentrations of glycerol can affect (a) physical features of the cytoplasm (cytoplasmic organization and viscosity), (b) permeability and stability of the membrane bilayer(s), and (c) noncovalent attachment of proteins to the sperm surface. Perturbing effects of glycerol on sperm metabolism and the essentiality of maintaining bioenergetic balance during the temperature changes associated with any cryopreservation protocol are discussed. Emphasis is placed on the processes in avian reproduction that may be altered by interactions with glycerol. Finally, we discuss the potential value of using available genetic models (lines of roosters differing in the capacity of their sperm to survive a freeze-thaw cycle) to clarify and overcome damage to poultry sperm induced by cryopreservation.