Cardiac metabolism in high performance fish

In aerobic tissues, such as cardiac and skeletal muscle, short term increases in energy demand are met primarily by acute regulation of mitochondrial pathways. Chronic increases in time-average metabolic rate of an individual or tissue can lead to modest “physiological adaptations” that may result in increased metabolic capacities and more efficient energy production and utilization. These physiological adaptations differ fundamentally from those which alter metabolic rate acutely. Analysis of the metabolic strategies used by an individual to chronically elevate cardiac metabolic rates may help identify the components of cardiac metabolism which may be constrained or malleable over evolutionary time. While pronounced physiological differences in cardiac energy transduction are apparent across species, the evolutionary origins of such differences are difficult to assess. However, the functional consequences of such differences in homologous tissues across species can be discussed with more certainty. Both chronic hypermetabolic challenges and interspecies comparisons suggest highly oxidative tissues such as heart are restricted to strategies which a) elevate the functional mass b) make more efficient use of intracellular space devoted to mitochondria and c) shift toward more efficient metabolic fuels, primarily fatty acids if oxygen delivery is not a factor.     

Engineering metabolic systems for production of advanced fuels

The depleting petroleum storage and increasing environmental deterioration are threatening the sustainable development of human societies. As such, biofuels and chemical feedstocks generated from renewable sources are becoming increasingly important. Although previous efforts led to great success in bio-ethanol production, higher alcohols, fatty acid derivatives including biodiesels, alkanes, and alkenes offer additional advantages because of their compatibility with existing infrastructure. In addition, some of these compounds are useful chemical feedstocks. Since native organisms do not naturally produce these compounds in high quantities, metabolic engineering becomes essential in constructing producing organisms. In this article, we briefly review the four major metabolic systems, the coenzyme-A mediated pathways, the keto acid pathways, the fatty acid pathway, and the isoprenoid pathways, that allow production of these fuel-grade chemicals.     

Size-related effects and the influence of metabolic traits and morphology on swimming performance in fish

Energy metabolism fuels swimming and other biological processes. We compared the swimming performance and energy metabolism within and across eight freshwater fish species. Using swim tunnel respirometers, we measured the standard metabolic rate (SMR) and maximum metabolic rate (MMR) and calculated the critical swimming speed (U_crit). We accounted for body size, metabolic traits, and some morphometric ratios in an effort to understand the extent and underlying causes of variation. Body mass was largely the best predictor of swimming capacity and metabolic traits within species. Moreover, we found that predictive models using total length or SMR, in addition to body mass, significantly increased the explained variation of U_crit and MMR in certain fish species. These predictive models also underlined that, once body mass has been accounted for, U_crit can be independently affected by total length or MMR. This study exemplifies the utility of multiple regression models to assess within-species variability. At interspecific level, our results showed that variation in U_crit can partly be explained by the variation in the interrelated traits of MMR, fineness, and muscle ratios. Among the species studied, bleak Alburnus alburnus performed best in terms of swimming performance and efficiency. By contrast, pumpkinseed Lepomis gibbosus showed very poor swimming performance, but attained lower mass-specific cost of transport (MCOT) than some rheophilic species, possibly reflecting a cost reduction strategy to compensate for hydrodynamic disadvantages. In conclusion, this study provides insight into the key factors influencing the swimming performance of fish at both intra- and interspecific levels.     

Diet-induced metabolic acidosis and the performance of high intensity exercise in man

The influence of four isolated periods of dietary manipulation upon high intensity exercise capacity was investigated in six healthy male subjects. Subjects consumed their 'normal' (N) diet (45 +/- 2% carbohydrate (CHO), 41 +/- 3% fat, 14 +/- 3% protein) for four days after which they exercised to voluntary exhaustion at a workload equivalent to 100% VO2max. Three further four-day periods of dietary manipulation took place; these were assigned in a randomised manner and each was followed by a high intensity exercise test. The dietary treatments were: a low CHO (3 +/- 1%), high fat (71 +/- 5%), high protein (26 +/- 3%) diet (HFHP); a high CHO (73 +/- 2%), low fat (12 +/- 2%), normal protein (15 +/- 1%) diet (HCLF); and a normal CHO (47 +/- 3%), low fat (27 +/- 2%), high protein (26 +/- 2%) diet (LFHP). Acid-base status and blood lactate concentration were measured on arterialised-venous blood at rest prior to dietary manipulation on each day of the different diets, immediately prior to exercise and at 2, 4, 6, 10 and 15 min post-exercise. Other metabolite concentrations were measured in the blood samples obtained prior to dietary manipulation and immediately prior to exercise. Exercise time to exhaustion after the HFHP diet (179 +/- 63 s) was shorter when compared with the N (210 +/- 65 s; p less than 0.01) and HCLF (219 +/- 69 s; p less than 0.05) diets.(ABSTRACT TRUNCATED AT 250 WORDS)     

Development and validation of a high performance liquid chromatography assay for 17alpha-methyltestosterone in fish feed

17alpha-Methyltestosterone (MT) is used to manipulate the gender of a variety of fish species. A high performance liquid chromatography (HPLC) internal standard method for the determination of 17alpha-methyltestosterone in fish feed using 3beta-methoxy-17beta-hydroxyandrost-5-en-7-one as internal standard (IS) has been developed. The method has been validated for the quantitation of MT in fish feed using 245 nm UV absorbance as the parent wavelength and 255 nm as a qualifier wavelength. The method was validated in the concentration range of 15.0-120 mg/kg of 17alpha-methyltestosterone in fish feed. Method was also found to be suitable for other feeds.     

Dissolved oxygen and fish behavior

Synopsis This essay reviews the behavioral responses of fish to reduced levels of dissolved oxygen from the perspective of optimization theory as used in contemporary behavioral ecology. A consideration of oxygen as a resource suggests that net oxygen gain per unit of energy expenditure will be the most useful currency for ecological models of breathing. In the process of oxygen uptake, fish always expend energy on perfusion, usually on ventilation and often on locomotion. These costs, and the risk of predation, will vary with oxygen availability and the type of behavioral response shown. The principal categories of behavioral response to reduced external availability of dissolved oxygen are (1) changes in activity, (2) increased use of air breathing, (3) increased use of aquatic surface respiration, and (4) vertical or horizontal habitat changes. Fish should choose whichever combination of responses minimizes the costs of meeting their oxygen demands. A small number of studies provides qualitative support for this prediction.     

Mating behavior is controlled by acute changes in metabolic fuels

Mild food restriction for 48 h inhibits mating behavior in female musk shrews (Suncus murinus). However, mating behavior is restored after a 90-min feeding bout. In this series of experiments, we examined the role of metabolic fuels in this behavioral restoration. First, drugs reported to block glycolysis or fatty acid oxidation were given 2 h before mating. Both treatments inhibited mating in food-restricted females that were refed after treatment. Blood glucose levels were assessed in females that were fed ad libitum, food restricted, or food restricted and refed for 90 min. Food restriction significantly lowered blood glucose compared with ad libitum feeding or food restriction in combination with 90 min of refeeding. However, neither glucose nor fat alone could substitute for food and promote mating behavior in food-restricted females. In addition, analysis of ketone bodies and body composition in females demonstrated low or undetectable levels of these energy substrates. Our data suggest that musk shrews have relatively little stored energy. Therefore, female musk shrews rely on continuous food intake and monitor multiple cues acutely, including glucose availability and fatty acid oxidation. This ensures that mating does not occur when adequate energy is unavailable.     

Regulation of leucine catabolism by metabolic fuels in mammary epithelial cells

Lactation is associated with elevated catabolism of branched-chain amino acids (BCAA) in mammary glands to produce glutamate, glutamine, alanine, aspartate, and asparagine. This study determined effects of metabolic fuels on the catabolism of leucine (a representative BCAA) in bovine mammary epithelial cells. Cells were incubated at 37 °C for 2 h in Krebs buffer containing 0.5 mM l-leucine and either l-[1-¹⁴C]leucine or l-[U-¹⁴C]leucine. The medium also contained 0–5 mM d-glucose, 0–2 mM l-glutamine, 0–4 mM dl-β-hydroxybutyrate, or 0–2 mM oleic acid. Rates of leucine decarboxylation were 60 % lower, but rates of α-ketoisocaproate production were 34 % higher, in the presence of 2 mM glucose than in its absence. All variables of leucine catabolism did not differ between 2 and 5 mM glucose or between 0 and 4 mM dl-β-hydroxybutyrate. Compared with 0–0.25 mM glutamine, 0.5 and 2 mM l-glutamine reduced leucine transport, transamination, and decarboxylation. In contrast, increasing the concentration of oleic acid from 0 to 2 mM dose-dependently stimulated leucine transamination, decarboxylation, and oxidation of carbons 2–6. Oleic acid also enhanced the abundance of cytosolic BCAA transaminase, while reducing the phosphorylated level (inactive state) of the E1α subunit of the mitochondrial branched-chain α-ketoacid dehydrogenase complex. Thus, hypoglycemia or ketosis in early lactation does not likely affect BCAA metabolism in mammary epithelial cells. Increasing circulating levels of BCAA and oleic acid may have great potential to increase the syntheses of glutamate, glutamine, aspartate, alanine, and asparagine by lactating mammary glands, thereby leading to enhanced production of milk for suckling neonates.     

Protein synthesis and oxygen consumption in fish cells

Oxygen consumption and protein synthesis were measured concurently in four fish cell types: BF-2 and TRG-2 cell lines, rainbow trout macrophages and scale cells. The fractional rates of protein synthesis (percentage of the protein mass synthesised per day) were ranked: BF-2 cells > macrophages > RTG-2 cells > scale cells. Oxygen consumption rates were ranked BF-2 cells = macrophages = RTG-2 cells > scale cells. Within three of the cell types (BF-2, RTG-2 and scale cells) oxygen consumption and protein synthesis were linearly correlated, whereas comparison between the four cell types gave rise to an exponential relationship between fractional rates of protein synthesis and oxygen consumption. Inhibition of protein synthesis with cycloheximide by 41–65% resulted in a 62–89% reduction in oxygen consumption depending on cell type. Calculations of the aerobic cost of protein synthesis using the cycloheximide-sensitive protein synthesis and oxygen consumption rates resulted in estimates ranging from 11 to 217 mol O₂·mg protein^-1 synthesised depending on the cell type. The lowest net protein synthesis costs, which are close to theoretical values for peptide bond formation, were associated with the most rapid rates of protein synthesis.Abbreviations ANOV A analysis of variance - BDH British Drug Housing - BOC British Oxygen Company - ADT A ethylenediaminetetra-acetic acid - FCS foetal calf serum - HEPES N-[2-hydroxyethyl] piperazine-N-[2-ethane-sulphonic acid] - LCD least square differnece - MEM munimum essential media - PBS phosphate-buffered saline - PCA perchloric acid - SIS spectral index of the sample - tSIE transformed spectral index of the external standard spectrum     

高氧条件下灵芝子实体活性氧含量及其代谢相关酶活性

灵芝Ganoderma lingzhi是最著名的药用真菌之一。本文研究了60%高氧条件下灵芝子实体呼吸速率、灵芝酸（ganoderic acid,GA）含量、总酚含量、活性氧（reactive oxygen species,ROS）含量、丙二醛（malondialdehyde,MDA）含量、抗氧化酶活性、黄嘌呤氧化酶（xanthineoxidase,XOD）活性、琥珀酸脱氢酶（succinic dehydrogenase,SDH）活性、H ⁺-ATP酶活性、Ca ²⁺-ATP酶活性的变化。结果显示,高氧抑制灵芝子实体的呼吸速率;处理前期（第1天）,灵芝子实体内过氧化氢（H₂O₂）和超氧阴离子自由基（O₂ ^-?）含量高于对照组,但随着处理的进行,ROS含量显著减少,MDA积累减少,超氧化物歧化酶（superoxide dismutase,SOD）、过氧化氢酶（catalase,CAT）和SDH活性提高,GA和总酚含量增加。表明一定的环境胁迫压力可以激发灵芝启动自身的抗氧化系统,保护机体免受氧化损伤,并促进相关次生代谢产物的合成。     

Pathways of unauthorized fish introductions and types of management responses

The study of the relationships among environmental factors, primary production, zooplankton community, and feeding behavior of fish species represents a key aspect to obtain a deeper knowledge of biological processes acting at ecosystem level. In this context, oceanographic data and biological samples were collected in two different surveys, carried out during late June 2011 and early July 2015 in the Strait of Sicily (Central Mediterranean Sea). Differences in abundance, biomass, and assemblage structure of zooplankton and anchovy (Engraulis encrasicolus Linnaeus, 1758) population were observed between the two surveys. Still, zooplankton biomass was significantly correlated to longitude, chlorophyll a recorded during the surveys (as a proxy of primary production), and oxygen concentrations. Such differences affected the isotopic composition of anchovy, which showed changes in δ¹⁵N and δ¹³C values between the two surveys. Mixing models identified different contributions of food sources in the two sampling periods, i.e., major consumption on large copepods and euphausiids in 2015 with respect to 2011, which was consistent with a greater availability of these preys in the environment in 2015. The obtained results evidenced that E. encrasicolus may be affected by any environmental change that influences the plankton community, which is the basis of the diet of these fishes. Such findings highlighted the importance to further investigate the trophic relationships among different compartments of the food web, as well as the possible environmental influences, in order to obtain a more complete picture of ecosystem functioning and also in the light of an ecosystem-based approach to fisheries management.     

Separation of phospholipid molecular species by high performance liquid chromatography: potentials for use in metabolic studies

Different molecular species of phospholipids exhibit distinctly different patterns of biologic behavior. In this minireview, the utility of HPLC for analysis of molecular species of phospholipids is illustrated in studies in which it has been demonstrated that molecular species are selectively synthesized, selectively transported, and selectively participate in enzymatic reactions. HPLC appears to be more adaptable for routine use than older procedures used to separate phospholipid molecular species. Since the metabolism of intact molecules can be characterized with HPLC, this procedure promises to provide particularly novel information with respect to changes in composition brought about by remodelling reactions during the biologic life of specific phospholipids.     

Effects of oxygen on biodegradation of fuels in a corroding environment

The relationship between corrosion and biodegradation of bio- and petroleum-based fuels was evaluated using aerobic seawater, fuel and unprotected carbon steel coupons under stagnant conditions to simulate a potential fuel storage condition. Aerobic respiration and corrosion reactions consumed oxygen in the incubations in a short time. The transient oxygen influenced the microbial biodegradation of all fuels and resulted in a suite of characteristic metabolites, including catechols. The corrosion was believed to be the result of biogenic sulfide production and in all cases, the black corrosion products contained chlorine and sulfur (presumed chloride and sulfide) in addition to iron. There were few differences in electrochemically measured corrosion rates in incubations amended with any of the fuels or their blends. Clone library analysis demonstrated higher proportions of Firmicutes, Deltaproteobacteria (primarily sulfate-reducing bacteria), Chloroflexi, and Lentisphaerae in incubations exposed to fuels than the original seawater. Relative proportions of sequences affiliated with these bacterial groups varied with fuel. Methanogen sequences similar to those of Methanolobus were also found in multiple incubations. Despite the dominance of characteristically anaerobic taxa, sequences coding for an alkane monooxygenase from marine hydrocarbon-degrading genera and aerobically produced intermediates were observed, indicative that organisms with this metabolic potential were active at some point during the incubation. Aerobic oxidation of fuel components resulted in the formation of a series of intermediates that could be used by anaerobic seawater microbial communities to support metabolism, sulfide production, and carbon steel corrosion.     

A bypass of sucrose synthase leads to low internal oxygen and impaired metabolic performance in growing potato tubers

Plants possess two alternative biochemical pathways for sucrose (Suc) degradation. One involves hydrolysis by invertase followed by phosphorylation via hexokinase and fructokinase, and the other route-which is unique to plants-involves a UDP-dependent cleavage of Suc that is catalyzed by Suc synthase (SuSy). In the present work, we tested directly whether a bypass of the endogenous SuSy route by ectopic overexpression of invertase or Suc phosphorylase affects internal oxygen levels in growing tubers and whether this is responsible for their decreased starch content. (a) Oxygen tensions were lower within transgenic tubers than in wild-type tubers. Oxygen tensions decreased within the first 10 mm of tuber tissue, and this gradient was steeper in transgenic tubers. (b) Invertase-overexpressing tubers had higher activities of glyceraldehyde-3-phosphate dehydrogenase, lactate dehydrogenase, and alcohol dehydrogenase, and (c) higher levels of lactate. (d) Expression of a low-oxygen-sensitive Adh1-beta-glucuronidase reporter gene construct was more strongly induced in the invertase-overexpressing background compared with wild-type background. (e) Intact transgenic tubers had lower ATP to ADP ratios than the wild type. ATP to ADP ratio was restored to wild type, when discs of transgenic tubers were incubated at 21% (v/v) oxygen. (f) Starch decreased from the periphery to the center of the tuber. This decrease was much steeper in the transgenic lines, leading to lower starch content especially near the center of the tuber. (g) Metabolic fluxes (based on redistribution of (14)C-glucose) and ATP to ADP ratios were analyzed in more detail, comparing discs incubated at various external oxygen tensions (0%, 1%, 4%, 8%, 12%, and 21% [v/v]) with intact tubers. Discs of Suc phosphorylase-expressing lines had similar ATP to ADP ratios and made starch as fast as wild type in high oxygen but had lower ATP to ADP ratios and lower rates of starch synthesis than wild type at low-oxygen tensions typical to those found inside an intact tuber. (h) In discs of wild-type tubers, subambient oxygen concentrations led to a selective increase in the mRNA levels of specific SuSy genes, whereas the mRNA levels of genes encoding vacuolar and apoplastic invertases decreased. (i) These results imply that repression of invertase and mobilization of Suc via the energetically less costly route provided by SuSy is important in growing tubers because it conserves oxygen and allows higher internal oxygen tensions to be maintained than would otherwise be possible.     

The biology of cancer: metabolic reprogramming fuels cell growth and proliferation

Cell proliferation requires nutrients, energy, and biosynthetic activity to duplicate all macromolecular components during each passage through the cell cycle. It is therefore not surprising that metabolic activities in proliferating cells are fundamentally different from those in nonproliferating cells. This review examines the idea that several core fluxes, including aerobic glycolysis, de novo lipid biosynthesis, and glutamine-dependent anaplerosis, form a stereotyped platform supporting proliferation of diverse cell types. We also consider regulation of these fluxes by cellular mediators of signal transduction and gene expression, including the phosphatidylinositol 3-kinase (PI3K)/Akt/mTOR system, hypoxia-inducible factor 1 (HIF-1), and Myc, during physiologic cell proliferation and tumorigenesis.     

Dissolved oxygen and fish distribution in a Florida spring

This study examined the distribution and relative abundance of fishes along a dissolved oxygen gradient in Singing Springs, Florida. Over the 1-year study, dissolved oxygen concentration in the spring exhibited a strong gradient ranging from an average of 0.20 mg l^–2AM¹ at the boil to 1.81 mg l^–2AM¹ 110 meters downstream. Seasonal variation in dissolved oxygen was very low relative to the spatial variation along the spring gradient. Fish community composition was evaluated monthly at the boil of the spring, 45 m downstream just after the confluence of the spring and the main river, and 110 m downstream. The fish community in the spring was characterized by species generally considered to be tolerant of low oxygen. Gambusia holbrooki was the most abundant species at all sites comprising an average of 88.1% of the fish captured at the boil, 63.2% of the fish captured at 45 m, and 74.8% of the fish captured at 110 m downstream. The diversity of fishes (G. holbrooki, Heterandria formosa, Notropis harperi, Lucania goodei, and Poecilia latipinna) increased with distance from the boil. Although there were some seasonal differences in patterns of diversity and community structure, the inter-site differences were much more apparent throughout the study. It is likely that the pattern of variation in dissolved oxygen interacts with the respiratory abilities of the fishes to affect the distribution pattern and community composition along the gradient.