Impact on energy metabolism of quantitative and functional cyclosporine-induced damage of kidney mitochondria

In this study we have measured, under experimental conditions which maintained efficient coupling, respiratory intensity, respiratory control, oxidative phosphorylation capacity and protonmotive force. Succinate cytochrome-c reductase and cytochrome-c oxidase activities were also studied. These investigations were carried out using kidney mitochondria from cyclosporine-treated rats (in vivo studies) and from untreated rats in the presence of cyclosporine (in vitro studies). Inhibition of respiratory intensity by cyclosporine did not exceed 21.1% in vitro and 15.9% in vivo. Since there was no in vitro inhibition of succinate cytochrome-c reductase and cytochrome-c oxidase activities, the slowing of electron flow observed can be interpreted as a consequence of an effect produced by cyclosporine between cytochromes b and c₁. Cyclosporine had no effect on respiratory control either in vitro or in vivo. Statistically significant inhibition of the oxidative phosphorylation was observed both in vitro (6.6%) and in vivo (12.1%). Moreover, cyclosporine did not induce any change of membrane potential either in vivo or in vitro. Our findings show that cyclosporine is neither a protonophore, nor a potassium ionophore. In cyclosporine-treated rats we noticed a decrease of protein in subcellular fraction, including the mitochondrial fraction. The role of the inhibition respiratory characteristics by cyclosporine in nephrotoxicity in vivo must take account of these two parameters: inhibition of the respiratory characteristics measured in vitro and diminution of mitochondrial protein in cyclosporine-treated rats.     

Roles of Subunit NuoK (ND4L) in the Energy-transducing Mechanism of Escherichia coli NDH-1 (NADH:Quinone Oxidoreductase)

The bacterial H⁺-translocating NADH:quinone oxidoreductase (NDH-1) catalyzes electron transfer from NADH to quinone coupled with proton pumping across the cytoplasmic membrane. The NuoK subunit (counterpart of the mitochondrial ND4L subunit) is one of the seven hydrophobic subunits in the membrane domain and bears three transmembrane segments (TM1–3). Two glutamic residues located in the adjacent transmembrane helices of NuoK are important for the energy coupled activity of NDH-1. In particular, mutation of the highly conserved carboxyl residue (_KGlu-36 in TM2) to Ala led to a complete loss of the NDH-1 activities. Mutation of the second conserved carboxyl residue (_KGlu-72 in TM3) moderately reduced the activities. To clarify the contribution of NuoK to the mechanism of proton translocation, we relocated these two conserved residues. When we shifted _KGlu-36 along TM2 to positions 32, 38, 39, and 40, the mutants largely retained energy transducing NDH-1 activities. According to the recent structural information, these positions are located in the vicinity of _KGlu-36, present in the same helix phase, in an immediately before and after helix turn. In an earlier study, a double mutation of two arginine residues located in a short cytoplasmic loop between TM1 and TM2 (loop-1) showed a drastic effect on energy transducing activities. Therefore, the importance of this cytosolic loop of NuoK (_KArg-25, _KArg-26, and _KAsn-27) for the energy transducing activities was extensively studied. The probable roles of subunit NuoK in the energy transducing mechanism of NDH-1 are discussed.     

Growth and reproduction of the mosquitofish,Gambusia affinis,in relation to temperature and ration level: consequences for life history

The allocation of energy to growth and reproduction, in relation to temperature and food availability, was investigated in laboratory experiments with the mosquitofish,Gambusia affinis. At constant temperature of 20, 25 and 30°C and ad libitum feeding, specific growth rates increased with increasing temperature at 1.7, 3.1 and 3.4% dry mass day⁻¹, respectively. Growth rates in a cycling temperature regime (20–30°C, ) were faster than in a 25°C constant temperature. As temperature increased from 20 to 30°C, mean age at first reproduction decreased from 191 to 56 days and brood size and mass of offspring increased significantly. Interbrood interval was also temperature dependent; estimates at 25 and 30°C for females >1000 mg were 22.6 and 18.6 days, respectively. Interbrood interval could not be calculated at 20°C. Although fitness was highest at 30°C, females at 25°C invested a greater proportion of surplus energy (growth and reproduction) to reproduction (38%) than at 20 (17%) or 30°C (36%) during the 32-week study. Fish at cooler temperatures began reproduction at a smaller size. Where rations were controlled at low, medium, and ad libitum levels, somatic and gonadal growth increased with increasing temperatures and food availability. The proportion of energy invested in reproduction was highest at 25°C for each comparable ration level. Calculated energy budgets indicated that over the 10-week study, 17–22% of the food energy was invested in growth, 0–7% in reproduction, and 75–83% in respiration and excretory losses, depending on feeding and temperature conditions.     

Structure,development and function of the branchial sieve of the common bream,Abramis brama,white bream,Blicca bjoerkna and roach,Rutilus rutilus

Synopsis The filter feeding organ of cyprinid fishes is the branchial sieve, which consists of a mesh formed by gill rakers and tiny channels on the gill arches. In order to establish its possible role during growth we measured the following morphological gill raker parameters over a range of sizes in three cyprinid fishes, bream, white bream and roach: inter raker distance, bony raker length, raker width, cushion length and channel width. At any given standard length common bream has the largest inter raker distance, roach the lowest and white bream is intermediate. In the comb model of filter feeding the inter raker distance is considered to be a direct measure of the mesh size and retention ability (= minimal size of prey that can be retained) of a filter. For the three species under study there is a conflict between the comb model and experimental data on particle retention. Lammens et al. (1987) found that common bream has a large retention ability whereas roach and white bream have a much smaller one. A new model, the channel model (Hoogenboezem et al. 1991) has been developed for common bream; in this model the lateral gill rakers can regulate the mesh size of the medial channels on the other side of the gill slit. The present data indicate that this model is not appropriate for white bream and roach. At any given standard length white bream and roach only reach 70% of the raker length of common bream, which means that in this model the gill slits should to be very narrow during filter feeding. The gill rakers consist of a bony raker and a fleshy cushion. The bony rakers have a rather long needle-like part outside the cushion in bream, but not in white bream and roach which have blunt gill rakers. Blunt gill rakers are not suited to reduce the diameter of the medial channels. The comb model seems more appropriate for white bream and roach, but doubts about the validity of this simple model remain. The sum of the areas of the medial channels is an approximation of the area through which water flows in the filter. This channel area therefore gives an impression of the capacity or flow rate of the filter. With this capacity estimation and an estimation of energy consumption we calculated an energy ratio of filter feeding. The energy ratio decreases with increasing standard length with an exponent close to the expected exponent of -0.40. The energy ratio is highest in bream, intermediate in white bream and lowest in roach.     

Thermogenic effect of adrenaline: interaction with insulin

The contribution of insulin (3.6 pmol.kg body mass-1.min-1) to adrenaline-induced (0.164 nmol.kg fat free mass-1.min-1) thermogenesis was studied in ten postabsorptive healthy volunteers using two sequential protocols. Variables considered were oxygen consumption as well as carbon dioxide production, heart rate, blood pressure, plasma concentrations of glucose, insulin, glycerol, free fatty acids, beta-HO-butyrate and lactate. Adrenaline increased plasma concentrations of glucose, glycerol, free fatty acids, and beta-HO-butyrate, and heart rate and metabolic rate during normo-insulinaemia [61.3 (SEM 6.6) pmol.l-1]. Similar effects were observed during hyperinsulinaemia [167.9 (SEM 18.7) pmol.l-1], but the effect of adrenaline on oxygen consumption was reduced. On average, metabolic rate increased by 12.9% during normo-insulinaemia and by 8.9% during hyperinsulinaemia. We concluded that relative hyperinsulinaemia resulted in decreased adrenaline-induced thermogenesis and therefore increased whole body anabolism.     

Analysis of the energy metabolism after incubation of Saccharomyces cerevisiae with sulfite or nitrite

After addition of 5 mM sulfite or nitrite to glucose-metabolizing cells of Saccharomyces cerevisiae a rapid decrease of the ATP content and an inversely proportional increase in the level of inorganic phosphate was observed. The concentration of ADP shows only small and transient changes. Cells of the yeast mutant pet 936, lacking mitochondrial F₁ATPase, after addition of 5 mM sulfite or nitrite exhibit changes in ATP, ADP and inorganic phosphate very similar to those observed in wild type cells. They key enzyme of glucose degradation, glyceraldehyde-3-phosphate dehydrogenase was previously shown to be the most sulfiteor nitrite-sensitive enzyme of the glycolytic pathway. This enzyme shows the same sensitivity to sulfite or nitrite in cells of the mutant pet 936 as in wild type cells. It is concluded that the effects of sulfite or nitrite on ATP, ADP and inorganic phosphate are the result of inhibition of glyceraldehyde-3-phosphate dehydrogenase and not of inhibition of phosphorylation processes in the mitochondria. Levels of GTP, UTP and CTP show parallel changes to ATP. This is explained by the presence of very active nucleoside monophosphate kinases which cause a rapid exchange between the nucleoside phosphates. The effects of the sudden inhibition of glucose degradation by sulfite or nitrite on levels of ATP, ADP and inorganic phosphate are discussed in terms of the theory of Lynen (1942) on compensating phosphorylation and dephosphorylation in steady state glucose metabolizing yeast.Abbreviations ATP adenosine triphosphate - ADP adenosine diphosphate - AMP adenosine monophosphate - P_i inorganic orthophosphate Dedicated to Prof. Dr. Hans Grisebach on the occasion of his sixtieth birthday     

Effect of Dichloroacetate on Regional Energy Metabolites and Pyruvate Dehydrogenase Activity During Ischemia and Reperfusion in Gerbil Brain

The objective of this study was to determine whether administration of dichloroacetate (DCA), an activator of pyruvate dehydrogenase (PDH), improves recovery of energy metabolites following transient cerebral ischemia. Gerbils were pretreated with DCA, and cerebral ischemia was produced using bilateral carotid artery occlusion for 20 min, followed by reperfusion up to 4 h. DCA had no effect on the accumulation of lactic acid and the decrease in ATP and phosphocreatine (PCr) during the 20-min insult, nor on the recovery of these metabolites measured at 20 and 60 min reperfusion. However, at 4 h reperfusion, levels of ATP and PCr were significantly higher in DCA-treated animals than in controls, as PCr exhibited a secondary decrease in caudate nucleus of control animals. PDH was markedly inhibited at 20 min reperfusion in both groups, but was reactivated to a greater extent in DCA-treated animals at 60 min and 4 h reperfusion. These results demonstrate that DCA had no effect on the initial recovery of metabolites following transient ischemia. However, later in reperfusion, DCA enhanced the postischemic reactivation of PDH and prevented the secondary failure of energy metabolism in caudate nucleus. Thus, inhibition of PDH may limit the recovery of energy metabolism following cerebral ischemia.     

Differences between observed and predicted energy costs at rest and during exercise in three subsistence-level populations

Estimates of daily energy expenditure are important for many areas of research in human ecology and adaptability. The most common technique for estimating human energy expenditure under field conditions, the factorial method, generally relies on activity-specific energy costs derived from published sources, based largely on North American and European subjects. There is concern that such data may not be appropriate for non-Western populations because of differences in metabolic costs. The present study addresses this concern by comparing measured vs. predicted energy costs at rest and during sub-maximal exercise in 83 subjects (52 males, 31 females) from three subsistence-level populations (Siberian herders and high-land and coastal Ecuadorian farmers). Energy costs at rest (i.e., lying, sitting and standing) and while performing a standard stepping exercise did not significantly differ among the three groups. However, resting energy costs were significantly elevated over predicted levels (+16% in men, +11% in women), whereas exercising costs were comparable to predicted values (?6% in men, +3% in women). Elevations in resting energy needs appear to reflect responses to thermal stress. These results indicate that temperature adjustments of resting energy costs are critical for accurately predicting daily energy needs among traditionally living populations. o 1996 Wiley-Liss, Inc.     

Is there an energy conservation “system” in brain that protects against the consequences of energy depletion?

A poorly understood marked decrease (circa 50% of control) in local cerebral glucose utilization is caused by sublethal doses of NaCN. The decrease is global, occurring in essentially all brain regions and is entirely reversible within hours, leaving no obvious pathology. This event is not unique to NaCN in so far as a strikingly similar pattern of decreased glucose utilization occus with some other toxins. Nor can it be attributed to a direct action of NaCN since local application by microdialysis to the striatum produces a global depression. These results imply that some widely distributed system or substance is involved. We speculate the existence of a system possibly related to the reticular activating system that senses a fall in energy production and acts globally to make cells quiescent and thus would give some protection from excitotoxic driven damage.Special issue dedicated to Dr. Sidney Ochs.     

Importance of fungi in the diet of Gammarus pulex and Asellus aquaticus

An important component of the interaction between macroinvertebrates and leaf litter in streams in the extent to which consumers can differentiate between undecomposed and decomposing leaves. The detritivores Gammarus pulex and Asellus aquaticus fed preferentially on conditioned rather on unconditioned leaf material. Growth in A. aquaticus was significantly reduced when unconditioned leaves were provided, but in G. pulex no significant effect of conditioning on growth was observed. The capacity of G. pulex to tolerate reductions in food quality seems to be a consequence of a compensatory system in which respiration rates change to compensate for reductions in food quality. In this way a constant growth rate is maintained. Increases in ingestion rates to compensate for low quality food were not observed.