Adaptation to short photoperiods augments circadian food anticipatory activity in Siberian hamsters

This article is part of a Special Issue “Energy Balance”.     

Comparison of energy evaluation systems and a mechanistic model for milk production by dairy cattle offered fresh grass-based diets

Grass-based diets are of increasing social-economic importance in dairy cattle farming, but their low supply of glucogenic nutrients may limit the production of milk. Current evaluation systems that assess the energy supply and requirements are based on metabolisable energy (ME) or net energy (NE). These systems do not consider the characteristics of the energy delivering nutrients. In contrast, mechanistic models take into account the site of digestion, the type of nutrient absorbed and the type of nutrient required for production of milk constituents, and may therefore give a better prediction of supply and requirement of nutrients. The objective of the present study is to compare the ability of three energy evaluation systems, viz. the Dutch NE system, the agricultural and food research council (AFRC) ME system, and the feed into milk (FIM) ME system, and of a mechanistic model based on Dijkstra et al. [Simulation of digestion in cattle fed sugar cane: prediction of nutrient supply for milk production with locally available supplements. J. Agric. Sci., Cambridge 127, 247–60] and Mills et al. [A mechanistic model of whole-tract digestion and methanogenesis in the lactating dairy cow: model development, evaluation and application. J. Anim. Sci. 79, 1584–97] to predict the feed value of grass-based diets for milk production. The dataset for evaluation consists of 41 treatments of grass-based diets (at least 0.75 g ryegrass/g diet on DM basis). For each model, the predicted energy or nutrient supply, based on observed intake, was compared with predicted requirement based on observed performance. Assessment of the error of energy or nutrient supply relative to requirement is made by calculation of mean square prediction error (MSPE) and by concordance correlation coefficient (CCC). All energy evaluation systems predicted energy requirement to be lower (6–11%) than energy supply. The root MSPE (expressed as a proportion of the supply) was lowest for the mechanistic model (0.061), followed by the Dutch NE system (0.082), FIM ME system (0.097) and AFRC ME system (0.118). For the energy evaluation systems, the error due to overall bias of prediction dominated the MSPE, whereas for the mechanistic model, proportionally 0.76 of MSPE was due to random variation. CCC analysis confirmed the higher accuracy and precision of the mechanistic model compared with energy evaluation systems. The error of prediction was positively related to grass protein content for the Dutch NE system, and was also positively related to grass DMI level for all models. In conclusion, current energy evaluation systems overestimate energy supply relative to energy requirement on grass-based diets for dairy cattle. The mechanistic model predicted glucogenic nutrients to limit performance of dairy cattle on grass-based diets, and proved to be more accurate and precise than the energy systems. The mechanistic model could be improved by allowing glucose maintenance and utilization requirements parameters to be variable.     

Comparative study of the metabolic responses during food shortage and subsequent recovery at different temperatures in the adult lesser mealworm, Alphitobius diaperinus (Coleoptera: Tenebrionidae)

Metabolic responses to prolonged food shortage (35 days) and subsequent re‐feeding (14 days) were investigated in adults of an introduced beetle, Alphitobius diaperinus Panzer, as a function of temperature (12, 16, 20 and 24 °C). Various qualitative and quantitative changes that greatly vary according to the temperature experienced occurred in metabolite levels during prolonged starvation. Whereas levels of protein and ATP did not change significantly, triglycerides decreased markedly and glycogen changed little. Metabolite levels were differently affected by temperature, with triglycerides being less rapidly degraded at 20 than at 24 °C and almost completely depleted at 12 and 16 °C; in contrast to higher temperatures, glycerol is accumulated at 12 °C. Physiological adaptation to starvation and low temperatures are highly linked and energy allocation for starvation vs. temperature acclimation must be strictly regulated, both being essential for insect survival. Re‐synthesis rates during recovery are probably highly temperature‐dependent for all metabolites. The proteins retained during starvation and the preferential degradation of lipids allowed a rapid recovery. Above 16 °C, adult A. diaperinus regained locomotory activity rapidly and the triglyceride, glycerol and glycogen reserves were restored. This tropical species may be able to colonize other environments such as natural and/or artificial biotopes where conditions are close to those of its natural habitat.     

Daily torpor in relation to photoperiod in a subtropical blossom-bat, Syconycteris australis (Megachiroptera)

Daily torpor in many temperate-zone mammals is affected by photoperiod. As little is known about the effects of photoperiod on torpor in subtropical species, we investigated whether, and if so how, torpor use, duration, and depth are affected by acclimation to three photoperiods (short, intermediate, long) in the blossom-bat Syconycteris australis. In contrast to many other studies, torpor occurrence, duration, and depth did not significantly respond to photoperiod acclimation in S. australis. Interestingly, the trend of a decline in torpor use under long photoperiod was the opposite of that observed previously in S. australis, which had been captured from the wild in summer and winter. Our study suggests that some species living in low latitude areas with unpredictable weather like S. australis may not use photoperiod for seasonal adjustments in physiology because it is not a reliable cue for food availability.     

Thiamine Deficiency in Cultured Neuroblastoma Cells: Effect on Mitochondrial Function and Peripheral Benzodiazepine Receptors

Abstract: When neuroblastoma cells were transferred to a medium of low (6 n M ) thiamine concentration, a 16-fold decrease in total intracellular thiamine content occurred within 8 days. Respiration and ATP levels were only slightly affected, but addition of a thiamine transport inhibitor (amprolium) decreased ATP content and increased lactate production. Oxygen consumption became low and insensitive to oligomycin and uncouplers. At least 25% of mitochondria were swollen and electron translucent. Cell mortality increased to 75% within 5 days. [³H]PK 11195, a specific ligand of peripheral benzodiazepine receptors (located in the outer mitochondrial membrane) binds to the cells with high affinity ( K _D = 1.4 ± 0.2 n M ). Thiamine deficiency leads to an increase in both B _max and K _D. Changes in binding parameters for peripheral benzodiazepine receptors may be related to structural or permeability changes in mitochondrial outer membranes. In addition to the high-affinity (nanomolar range) binding site for peripheral benzodiazepine ligands, there is a low-affinity (micromolar range) saturable binding for PK 11195. At micromolar concentrations, peripheral benzodiazepines inhibit thiamine uptake by the cells. Altogether, our results suggest that impairment of oxidative metabolism, followed by mitochondrial swelling and disorganization of cristae, is the main cause of cell mortality in severely thiamine-deficient neuroblastoma cells.     

Metabolic rate does not decrease with starvation in Gryllus bimaculatus when changing fuel use is taken into account

Many behavioural traits are considered to be condition‐dependent, reflecting the differential allocation of resources to fitness‐related traits and maintenance, although the physiological underpinnings of condition dependence are not well understood. In the present study, the hypothesis that condition dependence in male Gryllus bimaculatus De Geer is mediated by a decrease in metabolic rate with declining condition is tested. CO₂ production is measured by flow‐through respirometry, with insect condition manipulated through starvation. Crickets starved for 7 days have lower CO₂ emission rates than individuals starved for only 24 h. However, carbohydrate reserves are depleted in the first 3 days, suggesting that the initial metabolism is primarily fuelled by carbohydrate, with a shift to lipid stores after 3 days. If the metabolic rate is estimated using respiratory quotients reflecting this shift in fuels, there is no difference in metabolic rate between crickets starved for 24 h and 7 days, suggesting that metabolic rate does not decrease with declining condition. This implies that a decrease in metabolic rate during starvation may not be a general pattern in insects, and emphasizes the need to consider fuel use during metabolic rate estimation in starvation studies.     

Does choice of estimators influence conclusions from true metabolizable energy feeding trials?

True metabolizable energy (TME) is a measure of avian dietary quality that accounts for metabolic fecal and endogenous urinary energy losses (EL) of non-dietary origin. The TME is calculated using a bird fed the test diet and an estimate of EL derived from another bird (Paired Bird Correction), the same bird (Self Correction), or several other birds (Group Mean Correction). We evaluated precision of these estimators by using each to calculate TME of three seed diets in blue-winged teal (Anas discors). The TME varied by <2% among estimators for all three diets, and Self Correction produced the least variable TMEs for each. The TME did not differ between estimators in nine paired comparisons within diets, but variation between estimators within individual birds was sufficient to be of practical consequence. Although differences in precision among methods were slight, Self Correction required the lowest sample size to achieve a given precision. Feeding trial methods that minimize variation among individuals have several desirable properties, including higher precision of TME estimates and more rigorous experimental control. Consequently, we believe that Self Correction is most likely to accurately represent nutritional value of food items and should be considered the standard method for TME feeding trials.     

The impact of trade openness on global carbon dioxide emissions: Evidence from the top ten emitters among developing countries

This study aims to analyze the relationship between carbon dioxide (CO₂) emissions, trade openness, real income and energy consumption in the top ten CO₂ emitters among the developing countries; namely China, India, South Korea, Brazil, Mexico, Indonesia, South Africa, Turkey, Thailand and Malaysia over the period of 1971–2011. In addition, the possible presence of the EKC hypothesis is investigated for the analyzed countries. The Zivot–Andrews unit root test with structural break, the bounds testing for cointegration in the presence of structural break and the VECM Granger causality method are employed. The empirical results indicate that (i) the analyzed variables are co-integrated for Thailand, Turkey, India, Brazil, China, Indonesia and Korea, (ii) real income, energy consumption and trade openness are the main determinants of carbon emissions in the long run, (iii) there exists a number of causal relations between the analyzed variables, (iv) the EKC hypothesis is validated for Turkey, India, China and Korea. Robust policy implications can be derived from this study since the estimated models pass several diagnostic and stability tests.     

Identification of the Citrate-binding Site of Human ATP-Citrate Lyase Using X-ray Crystallography

ATP-citrate lyase (ACLY) catalyzes the conversion of citrate and CoA into acetyl-CoA and oxaloacetate, coupled with the hydrolysis of ATP. In humans, ACLY is the cytoplasmic enzyme linking energy metabolism from carbohydrates to the production of fatty acids. In situ proteolysis of full-length human ACLY gave crystals of a truncated form, revealing the conformations of residues 2–425, 487–750, and 767–820 of the 1101-amino acid protein. Residues 2–425 form three domains homologous to the β-subunit of succinyl-CoA synthetase (SCS), while residues 487–820 form two domains homologous to the α-subunit of SCS. The crystals were grown in the presence of tartrate or the substrate, citrate, and the structure revealed the citrate-binding site. A loop formed by residues 343–348 interacts via specific hydrogen bonds with the hydroxyl and carboxyl groups on the prochiral center of citrate. Arg-379 forms a salt bridge with the pro-R carboxylate of citrate. The pro-S carboxylate is free to react, providing insight into the stereospecificity of ACLY. Because this is the first structure of any member of the acyl-CoA synthetase (NDP-forming) superfamily in complex with its organic acid substrate, locating the citrate-binding site is significant for understanding the catalytic mechanism of each member, including the prototype SCS. Comparison of the CoA-binding site of SCSs with the similar structure in ACLY showed that ACLY possesses a different CoA-binding site. Comparisons of the nucleotide-binding site of SCSs with the similar structure in ACLY indicates that this is the ATP-binding site of ACLY.     

Evaluation of energy deposition and secondary particle production in proton therapy of brain using a slab head phantom

AimEvaluation of energy deposition of protons in human brain and calculation of the secondary neutrons and photons produced by protons in proton therapy.BackgroundRadiation therapy is one of the main methods of treating localized cancer tumors. The use of high energy proton beam in radiotherapy was proposed almost 60 years ago. In recent years, there has been a revival of interest in this subject in the context of radiation therapy. High energy protons suffer little angular deflection and have a well-defined penetration range, with a sharp increase in the energy loss at the end of their trajectories, namely the Bragg peak.Materials and methodsA slab head phantom was used for the purpose of simulating proton therapy in brain tissue. In this study simulation was carried out using the Monte Carlo MCNPX code.ResultsBy using mono energetic proton pencil beams, energy depositions in tissues, especially inside the brain, as well as estimating the neutron and photon production as a result of proton interactions in the body, together with their energy spectra, were calculated or obtained. The amount of energy escaped from the head by secondary neutrons and photons was determined.ConclusionsIt was found that for high energy proton beams the amount of escaped energy by neutrons is almost 10 times larger than that by photons. We estimated that at 110 MeV beam energy, the overall proton energy “leaked” from the head by secondary photons and neutrons to be around 1%.