Seasonal changes in energy and the energy cost of spawning in Gulf of Alaska Pacific cod

In the Gulf of Alaska, adult Pacific cod exhibited an annual cycle of condition, gonad index and liver index in which maximum values occurred in ripe fish in March and minima in July. About 30–31 % of prespawning stored energy was expended during the spawning effort. The energy associated with spawning derived from liver (24% and 18%), somatic tissue (22% and 33%) and gonad (53% and 48%) for females and males, respectively. Liver index and gonad index at the time of sampling were directly related in females, but in males gonad index was best related to liver index 1–3 months earlier.
The Pacific cod is very similar to the Atlantic cod in terms of energy cycling, maximum gonad sizes, energy expended during spawning and gonadal contribution to energy expenditure. However, in Pacific cod, somatic tissue contributes markedly to energy expended during reproduction. The Pacific cod cod differs from the walleye pollock with respect to gonad index (13% and 20%ν. 20% and 8% for females and males, respectively), spawning weight loss (25%ν. 38%), liver energy loss during spawning (71%ν. 55%) and energy cost of spawning.     

Size-dependent energy reserves, energy utilization and longevity in the yellow dung fly

Abstract.  Teneral reserve components (soluble sugars, glycogen, lipids), as well as proteins, of laboratory-reared yellow dung flies ( Scathophaga stercoraria ) are shown to increase hypo-allometrically (slope < 1) with body size. This is also true for sugars and glycogen of field-caught reproductive flies, the lipid content of which however, increases hyper-allometrically (slope > 1), probably related to foraging or reproductive activity. The longevity, or starvation resistance, of adults subsisting exclusively on their teneral reserves equally increases with body size, and this positive relationship remains when flies have access to sugar, pollen or prey for 24 h after emergence. Energy use, by contrast, is generally not body size dependent, except for lipid (and possibly glycogen) utilization when flies were completely starved. All the results obtained are independent of sex after controlling for sexual size dimorphism. These net results clearly support the greater energy efficiency of larger flies (Kleiber's law), whereas only weak evidence is obtained in support of the contrasting hypothesis of greater absolute energy demands of larger individuals, possibly because such effects are likely masked by stronger size-dependent anabolic effects.     

A protonmotive force as the source of energy for galactoside transport in energy depletedEscherichia Coli

Summary Uracil transport inSaccharomyces cerevisiae is mediated by a specific permease which does not recognize other pyrimidines such as uridine, cytosine, thymine, 2-hydroxypyrimidine or 5-amino-uracil; hypoxanthine and 6-amino-uracil slightly inhibit the uptake of uracil in a strain lacking cytosine permease activity. Wild type cells concentrate extracellular uracil before its transformation into UMP and subsequent incorporation into nucleic acids. A strain lacking UMP pyrophosphorylase and uridine ribohydrolase (strainfur 1–8 rh, in which the endogenous production as well as the utilization of uracil are lacking) is able to concentrate¹⁴C-2 uracil from the medium. At the same time no other¹⁴C-2 labelled compound could be detected in this strain, thus suggesting that the uptake of uracil in yeast occurs by active transport which is not coupled to the UMP pyrophosphorylase. The optimal pH of uracil uptake in standard growth conditions was 4.3. It was deduced from experiments performed on strainfur 1–8 rh with³H-5 and¹⁴C-2 uracil that the intracellular pool of uracil is recycled once the steady-state has been reached. First order kinetics with similar rate constants were observed for uracil efflux in strainfur 1–8 rh (k min^–1=0.75±0.08) as well as in the strain lacking uracil permease,fur 1–8 rh fur 4–6 (k min^–1=0.60±0.08). The intracellular pool of¹⁴C-2 uracil can be chased in strainfur 1–8 rh by addition of³H uracil without inducing a large initial acceleration of the exit rate (the rate constant remained at 0.60). 2-4-dinitrophenol inhibits the uptake of uracil but also reduces the efflux of uracil in strainfur 1–8 rh fur 4–6. These data and the comparison with cytosine transport in the same organism support the hypothesis that, whereas uracil uptake is a permease mediated active transport, the efflux of uracil does not involve the uracil uptake permease. A coefficient of permeability of 7.4×10^–7 cm sec^–1 was calculated for uracil.     

Genetic variations in the regulation of energy balance

Single nucleotide polymorphism (SNP) near certain genes revealed association of FAT (fat mass and obesity-associated gene), MC4R (melanocortin 4 receptor gene), and other genes with obesity. However, involvement of the FAT expression products in the regulation of energy balance remains to be clarified. The function of MC4R encoding melanocortin 4 receptor (MC4R) is somewhat better understood. α-, β-, and γ- MSH encoded by the POMC gene bind to MC4R, reduce food intake, and slow down fat accumulation. Expression of POMC encoding MSH is enhanced by leptin binding to its receptor (LepRb) in hypothalamic neurons. Mutations in human and animal MC4R, POMC, and LEP genes are associated with obesity. More than 60 mutations in MC4R, more than 20 mutations in POMC and fewer LEP mutations have been reported. Nonsense mutations and reading frame shifts block gene expression and thereby disrupt protein synthesis. Missense mutations frequently affect protein folding in endoplasmic reticulum; unfolded or misfolded proteins remain in the cytoplasm and undergo degradation. Certain missence mutations do not interfere with gene expression and folding of proteins but impair their functioning at the periphery. p.S127L mutation in MC4R, p.E206X and p.F144L mutations in POMC as well as other mutations in homozygous and heterozygous forms account for impaired energy balance in humans. The following mutations have been identified in the LEP gene: G133fsX15, p.R105X, p.R105W, and p.S141C mutations. In homozygous form they are associated with obesity and other pathological conditions.     

Determinants of energy utilization in the activated myocardium

This is a review of work dealing with the effect of pressure overload and thryotoxic hypertrophy of rabbit hearts on the production of total activity related (TA) and initial (I) heats during isometric contraction. Pressure overload hypertrophy is produced by constricting the pulmonary artery with a spiral monel metal clip. Thyrotoxic hypertrophy is produced by 14 daily i.m. injections of 0.2 mg L-thyroxine per kilogram. Heat output is measured with Hill-type planar vacuum deposited bismuth and antimony thermopiles, and force is measured with a capacitance strain gauge. The pressure overload results in a depressed velocity of unloaded shortening, a depressed rate of isometric force development, and an increased time-to-peak tension. These changes are associated with a decreased myosin ATPase, a heart with no V1 myosin isoenzyme, and an increase in the economy of isometric force development (integral of Pdt/TA, integral of Pdt/I). The thyrotoxic hearts exhibit an increased velocity of shortening and rate of force development, and a decrease in time-to-peak tension. These changes are associated with an increase in myosin ATPase activity, a heart with increase in the V1 isoenzyme composition (88% V1), and a decrease in the economy of isometric force development (integral of Pdt/TA, integral of Pdt/I). The changes in the two types of hypertrophied hearts are interpreted in terms of altered cross-bridge cycling rates and changes in cross-bridge tension time integral as well as excitation contraction coupling phenomena. In the thyrotoxic hearts there is an increase in the economy of the recovery processes. Both types of hypertrophy are considered to be adaptive and involve the coordinated restructuring of the excitation-contraction, contractile, and recovery systems.     

Reproducibility of energy parameters in the pole vault

The purpose of this study was to analyze the reproducibility of kinematic, dynamometric and derived mechanical energy parameters in the pole vault as a main precondition for the practical applicability of the concept of energy exchange in the pole vault. A total of 46 vaults of six experienced vaulters were analyzed. On the basis of 3D kinematic data of the athlete and the pole and ground reaction forces measured at the end of the pole in the planting box the reproducibility of parameters that describe the energy transfer into the pole and the energy exchange between the athlete and the pole during the vault was proofed. Intraclass correlation, mean root mean square and the coefficient of variance were determined, additionally the Wilcoxon Test was applied. Parameters of the athlete's 3D total mechanical energy, e.g. initial energy and final energy, and the pole energy (maximum pole energy, energy of the pole due to compressive force and bending moment) were highly reproducible. The distribution of the energy transferred into the pole due to compressive force and bending moment, the same as the energy gain of the vaulter-pole system during the vault, which indicates the strategy of interacting with the pole, were also reproducible. With this the concept of energy exchange in the pole vault can be used to analyze the impact of training interventions, changes in movement pattern respectively, on the vaulters performance during different phases of the vault. The analysis of one trial of an athlete should be sufficient to identify changes in the athlete's interaction with the elastic pole.     

Reception of the energy level in bacterial taxis

In order to shed light upon the relationship between structure and function in biological systems, we investigate two simple hierarchically organized systems; namely, a two-level Ising-like system and a multi-level system introduced by Dyson in another context. Using equilibrium statistical mechanics we examine quantitatively the conditions for the functional decoupling of the levels in these model hierarchies.     

The surface energy of water: the largest but forgotten source of energy in biological systems

Many functional proteins perform mechanical, structural or chemical work. Such proteins often use the energy from the hydrolysis of adenosine triphosphate (ATP). The role of ATP as an energy source and its production by metabolism was established in the middle of the twentieth century and replaced glycolysis as the focus of study. Before this time the surface energy of water, quantified in the middle of the nineteenth century, had been visualized as an important source of biological energy. Experimental and theoretical work has shown that the internal work done by this energy source may greatly exceed the energy derived from metabolism. Although the energy from ATP usually does the work external to the body, even this may be supplemented by the surface energy of water to give greater efficiency. The consideration of the principles by which proteins might employ this larger source of energy to do work is germane at this time.     

Gender differences in the control of energy homeostasis

The world is experiencing an epidemic of obesity and its concomitant health problems. One implication is that the normally robust negative feedback system that controls energy homeostasis must be responding to different inputs than in the past. In this review we discuss the influence of gender on the efficacy of adiposity hormones as they interact with food intake control systems in the brain. Specifically, the levels of insulin and leptin in the blood are correlated with body fat, insulin being related mainly to visceral fat and leptin to subcutaneous fat. Since females carry more fat subcutaneously and males carry more fat viscerally, leptin correlates better with total body fat in females and insulin correlates better in males. High visceral fat and plasma insulin are also risk factors for the complications of obesity, including type-2 diabetes, cardiovascular problems, and certain cancers, and these are more prevalent in males. Consistent with these systemic differences, the brains of females are more sensitive to the catabolic actions of low doses of leptin whereas the brains of males are more sensitive to the catabolic action of low doses of insulin. The implications of this are discussed.     

Variations in the energy content of freshwater fish

The calorific value of the three-spined stickleback, Gasterosteus aculeatus , varied with its size, sex and the season. Fish of 16 mg dry weight had a value of 1950 cal/g while for fish of 313 mg the value was 470 cal/g. The califoric value of gravid females was 23% above that of males of comparable size. The califoric value of a tropical cichlid, Tilapia nilotica , with a dry weight of 11 g was 4300 cal/g, the calorific values of the tissues ranged from 2500 cal/g for bone to 5190 cal/g for muscle.     

Conversion of the energy of a high-current REB into electromagnetic wave energy

Results are presented from a theoretical investigation and quantitative analysis of the physical processes that govern the efficiency of a coaxial device aimed at converting the energy of a relativistic electron beam into the energy of a TEM wave (a wave in a circular cylindrical coaxial waveguide). The key diffractional problem is solved exactly using a simplified theoretical model, which makes it possible to understand the mechanisms for the formation of a TEM wave and determine how the beam parameters and the design parameters of the converter affect the relative fractions of the kinetic energy of a relativistic electron beam and the energy of its own magnetic and electric fields that are transferred into the energy of the TEM wave field. The results obtained are analyzed quantitatively, and prospects for further theoretical and experimental research in this area are outlined.     

Constraints on energy intake in fish: the link between diet composition, energy metabolism, and energy intake in rainbow trout

The hypothesis was tested that fish fed to satiation with iso-energetic diets differing in macronutrient composition will have different digestible energy intakes (DEI) but similar total heat production. Four iso-energetic diets (2 × 2 factorial design) were formulated having a contrast in i) the ratio of protein to energy (P/E): high (H(P/E)) vs. low (L(P/E)) and ii) the type of non-protein energy (NPE) source: fat vs. carbohydrate which were iso-energetically exchanged. Triplicate groups (35 fish/tank) of rainbow trout were hand-fed each diet twice daily to satiation for 6 weeks under non-limiting water oxygen conditions. Feed intake (FI), DEI (kJ kg(-0.8) d(-1)) and growth (g kg(-0.8) d(-1)) of trout were affected by the interaction between P/E ratio and NPE source of the diet (P<0.05). Regardless of dietary P/E ratio, the inclusion of carbohydrate compared to fat as main NPE source reduced DEI and growth of trout by ~20%. The diet-induced differences in FI and DEI show that trout did not compensate for the dietary differences in digestible energy or digestible protein contents. Further, changes in body fat store and plasma glucose did not seem to exert a homeostatic feedback control on DEI. Independent of the diet composition, heat production of trout did not differ (P>0.05). Our data suggest that the control of DEI in trout might be a function of heat production, which in turn might reflect a physiological limit related with oxidative metabolism.