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Degree-days (DD) are a useful metric for describing the thermal scope for fish growth and other physiological processes, but there is a lack of advice about how to calculate DD for a given fish species. In particular, appropriate values for the base temperature for growth ([T.sub.0]) are unknown for most fish species. Previous work showed that inappropriate [T.sub.0] values can bias growth rate estimates and lead to erroneous conclusions when comparing growth among populations. It is therefore critical to use biologically relevant [T.sub.0] values when calculating DD. We used two approaches that leverage empirical growth data and bioenergetics models to estimate [T.sub.0] for 82 fish species. We found that [T.sub.0] varied among species and across thermal guilds, with coldwater species having relatively low [T.sub.0] values and warmwater species having higher [T.sub.0] values. In addition, [T.sub.0] varied across life stages and depended on whether one selected air or water temperature data to calculate DD. We provide guidance for calculating DD in fish science for many species and scenarios. Key words: thermal time, standardization, bioenergetics, Introduction Ambient temperature drives ectotherm growth and other physiological processes (Hazel and Prosser 1974; Atkinson 1994; Diana 2003). More specifically, ectotherm metabolic processes and phenologies are tightly linked to the [...]

Objective: To investigate if dietary energy density is associated with measures of dietary quality (food group, micronutrient and macronutrient intakes) in children and adolescents. Subjects/Methods: In all, 551 children (mean age 9.6 years, 52% girls) and 569 adolescents (15.5 years, 55% girls), sampled from schools in Sweden, completed a single 24-h dietary recall. Dietary energy density (kJ/g) was calculated as the energy from all food consumed divided by the weight of all food consumed. Beverages were excluded from the calculation. Food and micronutrient intakes were adjusted for energy intake. A one-way analysis of variance (ANOVA) was used to test for differences in food group and nutrient intakes across age- and gender-specific tertiles of energy density. Discriminant analysis was used to confirm the groupings formed by tertiles. Results: Subjects with low-energy-density diets were significantly more likely to consume fruits, vegetables, pasta, rice, potatoes and cereals and less likely to consume sweetened drinks, sweets and chocolate. After energy adjustment, their intakes of many foods recommended in the Swedish food-based dietary guidelines were higher and intakes of nutrient-poor foods were lower. The macronutrient energy profile (% energy) of low-energy-density diets was closest to the recommended level. Low-energy-density diets contained greater amounts of most micronutrients. Discriminant analysis confirmed the existence of heterogeneous dietary patterns and the likelihood of correct classification by energy density in 65% of cases. Conclusions: Lower dietary energy density is associated with better dietary quality in children and adolescents. Energy density has advantages over other whole diet analysis methods and may be suitable as a simple proxy of diet quality. European Journal of Clinical Nutrition (2010) 64, 356-363; doi: 10.1038/ejcn.2009.160; published online 13 January 2010 Keywords: 24-h recall; dietary patterns; epidemiology; foods; nutrients, Introduction No simple, well-accepted criteria exist that allow diets to be classified as healthy or unhealthy. Attempts to assess overall diet quality have often relied on scores or indexes (Kant, [...]

J Strength Cond Res 24(1): 48-59, 2010--The purpose of the present study was to investigate the aerobic capacity characteristics of an isocaloric carbohydrate (CHO) plus protein (PRO) drink and a low-calorie CHO plus PRO drink against a traditional 6% CHO sports beverage. Twelve male and female trained cyclists exercised on 4 separate occasions at intensities that varied between 55 and 75% [Vo.sub.2]max for 2.5 hours and then at 80% [Vo.sub.2]max until fatigued. Supplements (255.4 [+ or -] 9.1 mL) were provided every 20 minutes and consisted of a 4.5% carbohydrate plus 1.15% protein complex (CHO/PRO H), a 3% carbohydrate plus 0.75% protein complex (CHO/PRO L), a 6% carbohydrate supplement (CHO), or a placebo (PLA). Time to fatigue at 80% [Vo.sub.2]max was significantly longer (p < 0.05) during the CHO (26.9 [+ or -] 6.1 minutes, mean [+ or -] SE), the CHO/PRO H (30.5 [+ or -] 5.9 minutes), and the CHO/PRO L (28.9 [+ or -] 6.5 minutes) trials compared with the PLA trial (14.7 [+ or -] 3.4 minutes), with no significant differences among the CHO, CHO/PRO H, and CHO/PRO L treatments. In general, blood glucose, plasma insulin, and carbohydrate oxidation were elevated above PLA during the CHO, CHO/ PRO H, and CHO/PRO L trials, whereas plasma free fatty acids, rating of perceived exertion, and fat oxidation values were lower during the CHO, CHO/PRO H, and CHO/PRO L trials compared with the PLA trial. Only minor differences in blood parameters occurred among the CHO, CHO/PRO H, and CHO/PRO L treatments. In summary, partially substituting PRO for CHO in a sports drink did not enhance aerobic capacity, but substitution was able to occur without loss of efficacy. Thus, adding PRO to a low-calorie CHO sports drink may be an effective strategy to enhance aerobic capacity while limiting carbohydrate and caloric consumption. KEY WORDS aerobic capacity, endurance, exercise metabolism, fatigue

Abstract Sport stacking is an activity taught in many physical education programs. The activity, although very popular, has been studied minimally, and the energy expenditure for sport stacking is unknown. [...]

The leptin regulation of bone remodeling, which has been documented through studies of loss-of-function mutations of this hormone or of its receptor in mice and humans, still raised several unanswered questions. For instance, it has been assumed but not formally demonstrated that this regulation occurs through neuronal means. Likewise, it has not been possible until now to dissociate the influence leptin exerts on appetite and energy expenditure from this function. We show here through mouse genetic studies that a deletion of the leptin receptor in neurons results in an increase in bone formation and bone resorption, resulting in a high bone mass as seen in leptin-deficient mice. In contrast, the same deletion in osteoblasts only does not influence bone remodeling. Furthermore, through the use of l/l mice, a model of gain of function in leptin signaling harboring a Y985L substitution in the leptin receptor, we show that leptin signaling inhibits bone mass accrual by up-regulating sympathetic activity independently of any change in appetite or energy expenditure. This work establishes that in vivo leptin regulates bone mass accrual by acting through neuronal means and provides a direct demonstration that this function of leptin can occur independently of its regulation of energy metabolism. bone remodeling | energy expenditure | osteoblasts | osteoclasts

The energy production of mitochondria in heart increases during exercise. Several works have suggested that calcium acts at multiple control points to activate net ATP production in what is termed 'parallel activation'. To study this, a computational model of mitochondrial energy metabolism in the heart has been developed that integrates the Dudycha-Jafri model for the tricarboxylic acid cycle with the Magnus-Keizer model for mitochondrial energy metabolism and calcium dynamics. The model improves upon the previous formulation by including an updated formulation for calcium dynamics, and new descriptions of sodium, hydrogen, phosphate, and ATP balance. To this end, it incorporates new formulations for the calcium uniporter, sodium-calcium exchange, sodium-hydrogen exchange, the [F.sub.1][F.sub.0]-ATPase, and potassium-hydrogen exchange. The model simulates a wide range of experimental data, including steady-state and simulated pacing protocols. The model suggests that calcium is a potent activator of net ATP production and that as pacing increases energy production due to calcium goes up almost linearly. Furthermore, it suggests that during an extramitochondrial calcium transient, calcium entry and extrusion cause a transient depolarization that serve to increase NADH production by the tricarboxylic acid cycle and NADH consumption by the respiration driven proton pumps. The model suggests that activation of the [F.sub.1][F.sub.0]-ATPase by calcium is essential to increase ATP production. In mitochondria very close to the release sites, the depolarization is more severe causing a temporary loss of ATP production. However, due to the short duration of the depolarization the net ATP production is also increased. oxidative phosphorylation; tricarboxylic acid cycle; pH; computer model doi: 10.1152/ajpcell.00271.2006

Mitochondria have been a central focus of several theories of aging as a result of their critical role in bioenergetics, oxidant production, and regulation of cell death. A decline in cardiac mitochondrial function coupled with the accumulation of oxidative damage to macromolecules may be causal to the decline in cardiac performance with age. In contrast, regular physical activity and lifelong caloric restriction can prevent oxidative stress, delay the onset of morbidity, increase life span, and reduce the risk of developing several pathological conditions. The health benefits of life long exercise and caloric restriction may be, at least partially, due to a reduction in the chronic amount of mitochondrial oxidant production. In addition, the available data suggest that chronic exercise may serve to enhance antioxidant enzyme activities, and augment certain repair/removal pathways, thereby reducing the amount of oxidative tissue damage. However, the characterization of age-related changes to cardiac mitochondria has been complicated by the fact that two distinct populations of mitochondria exist in the myocardium: subsar-colemmal mitochondria and interfibrillar mitochondria. Several studies now suggest the importance of studying both mitochondrial populations when attempting to elucidate the contribution of mitochondrial dysfunction to myocardial aging. The role that mitochondrial dysfunction and oxidative stress play in contributing to cardiac aging will be discussed along with the use of lifelong exercise and calorie restriction as countermeasures to aging. superoxide anion; longevity; postmitotic; calorie restriction; subsarcolemmal, interfibrillar, exercise doi:10.1152/ajpcell.00285.2006

Chronic constant hypoxia (CCH) and chronic intermittent hypoxia (CIH) are known to have deleterious effects on the central nervous system. Because of the difference in the pattern of hypoxic exposure, it is possible that the pathological outcome would vary. The N-acetyl aspartate/creatine (NAA/Cr) ratio is a reliable marker of neuronal integrity, and this can be noninvasively measured by proton nuclear magnetic resonance spectroscopy. P2 CD1 mouse pups with their dams were exposed to either CCH, where the [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII.] was maintained at 11% continuously or to CIH, where the [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII.], was varied between 21 and 11% every 4 min. P30 mice exposed to intermittent hypoxia for 4 wk demonstrated a significant decrease in the NAA/Cr ratio in the hippocampus and thalamus, which was reversed by a subsequent exposure to 4 wk of normoxia. Meanwhile, mice exposed to 4 wk of constant hypoxia did not demonstrate any differences in their NAA/Cr ratios from controls in these brain regions. These results indicate that an intermittent pattern of hypoxic exposure may have a more adverse effect on neuronal function and integrity than a continuous one. The reversal of NAA/Cr levels to baseline during the return to normoxia indicates that therapeutic strategies targeted at alleviating the intermittent hypoxic stress in diseases, such as obstructive sleep apnea, have the potential for inducing significant neurocognitive recovery in these patients. magnetic resonance imaging; energy metabolism; oxygen deprivation

The adult brain relies on glucose for its energy needs and stores it in the form of glycogen, primarily in astrocytes. Animal and culture studies indicate that brain glycogen may support neuronal function when the glucose supply from the blood is inadequate and/or during neuronal activation. However, the concentration of glycogen and rates of its metabolism in the human brain are unknown. We used in vivo localized [sup.13]C-NMR spectroscopy to measure glycogen content and turnover in the human brain. Nine healthy volunteers received intravenous infusions of [1-[sup.13]C]glucose for durations ranging from 6 to 50 h, and brain glycogen labeling and washout were measured in the occipital lobe for up to 84 h. The labeling kinetics suggest that turnover is the main mechanism of label incorporation into brain glycogen. Upon fitting a model of glycogen metabolism to the time courses of newly synthesized glycogen, human brain glycogen content was estimated at ~3.5 [micro]mol/g, i.e., three- to fourfold higher than free glucose at euglycemia. Turnover of bulk brain glycogen occurred at a rate of 0.16/[micro]mol*[g.sup.1-]*[h.sup.-1], implying that complete turnover requires 3-5 days. Twenty minutes of visual stimulation (n = 5) did not result in detectable glycogen utilization in the visual cortex, as judged from similar [[sup.13]C]glycogen levels before and after stimulation. We conclude that the brain stores a substantial amount of glycogen relative to free glucose and metabolizes this store very slowly under normal physiology. glucose; [sup.13]C nuclear magnetic resonance spectroscopy; visual stimulation

Brain cells are highly energy dependent for maintaining ion homeostasis during high metabolic activity. During active periods, full mitochondrial function is essential to generate ATP from electrons that originate with the oxidation of NADH. Decreasing brain metabolism is a significant cause of cognitive abnormalities of Alzheimer disease (AD), but it remains uncertain whether this is the cause of further pathology or whether synaptic loss results in a lower energy demand. Synapses are the first to show pathological symptoms in AD before the onset of clinical symptoms. Because synaptic function has high energy demands, interruption in mitochondrial energy supply could be the major factor in synaptic failure in AD. A newly discovered age-related decline in neuronal NADH and redox ratio may jeopardize this function. Mitochondrial dehydrogenases and several mutations affecting energy transfer are frequently altered in aging and AD. Thus, with the accumulation of genetic defects in mitochondria at the level of energy transfer, the issue of neuronal susceptibility to damage as a function of age and age-related disease becomes important. In an aging rat neuron model, mitochondria are both chronically depolarized and produce more reactive oxygen species with age. These concepts suggest that multiple treatment targets may be needed to reverse this multifactorial disease. This review summarizes new insights based on the interaction of mitoenergetic failure, glutamate excitotoxicity, and amyloid toxicity in the exacerbation of AD. bioenergetics; synaptic dysfunction; neurodegeneration; nicotinamide adenine dinucleotide; free radicals; mitochondrial membrane potential

Abstract: The concentration of mercury in fish generally increases with age and size. Although a number of hypotheses have been invoked to explain this pattern, our understanding of the processes [...]

Deficient bioenergetic signaling contributes to myocardial dysfunction and electrical instability in both atrial and ventricular cardiac chambers. Yet, approaches capable to prevent metabolic distress are only partially established. Here, in a canine model of tachycardia-induced congestive heart failure, we compared atrial and ventricular bioenergetics and tested the efficacy of metabolic rescue with the vasopeptidase inhibitor omapatrilat. Despite intrinsic differences in energy metabolism, failing atria and ventricles demonstrated profound bioenergetic deficiency with reduced ATP and creatine phosphate levels and compromised adenylate kinase and creatine kinase catalysis. Depressed phosphotransfer enzyme activities correlated with reduced tissue ATP levels, whereas creatine phosphate inversely related with atrial and ventricular load. Chronic treatment with omapatrilat maintained myocardial ATP, the high-energy currency, and protected adenylate and creatine kinase phosphotransfer capacity. Omapatrilat-induced bioenergetic protection was associated with maintained atrial and ventricular structural integrity, albeit without full recovery of the creatine phosphate pool. Thus therapy with omapatrilat demonstrates the benefit in protecting phosphotransfer enzyme activities and in preventing impairment of atrial and ventricular bioenergetics in heart failure. atria; ventricle; adenylate kinase; creatine kinase; energy metabolism; heart failure

Crystallization is a major bottleneck to obtaining x-ray structures of membrane proteins. By applying an established crystallization protocol for the lactose permease (LacY) of Escherichia coli, a systematic study of the effect of phospholipids (PL) on crystallization of Lacy was undertaken. We observe three different crystal forms that diffract to increasingly better resolution in a manner that correlates with the concentration of copurified PL. Consistently, progressive addition of E. coli PL to delipidated LacY leads to different crystal forms. Tetragonal crystals are obtained with improved diffraction quality for a stable mutant by carefully adjusting PL content. Furthermore, crystals of good quality from wild-type LacY, a particularly difficult protein, were also obtained by using same approach. Thus, it is likely that manipulation of PL is a good strategy for predominantly hydrophobic membrane proteins like LacY. lactose permease | membrane protein | structure | bioenergetics | membranes

NO reversibly inhibits mitochondrial respiration via binding to cytochrome c oxidase (CCO). This inhibition has been proposed to be a physiological control mechanism and/or to contribute to pathophysiology. Oxygen reacts with CCO at a heme iron:copper binuclear center ([a.sub.3]/[Cu.sub.B]). Reports have variously suggested that during inhibition NO can interact with the binuclear center containing zero (fully oxidized), one (singly reduced), and two (fully reduced) additional electrons. It has also been suggested that two NO molecules can interact with the enzyme simultaneously. We used steady-state and kinetic modeling techniques to reevaluate NO inhibition of CCO. At high flux and low oxygen tensions NO interacts predominantly with the fully reduced (ferrous/cuprous) center in competition with oxygen. However, as the oxygen tension is raised (or the consumption rate is decreased) the reaction with the oxidized enzyme becomes increasingly important. There is no requirement for NO to bind to the singly reduced binuclear center. NO interacts with either ferrous heme iron or oxidized copper, but not both simultaneously. The affinity ([K.sub.D]) of NO for the oxygen-binding ferrous heme site is 0.2 nM. The noncompetitive interaction with oxidized copper results in oxidation of NO to nitrite and behaves kinetically as if it had an apparent affinity of 28 nM; at low levels of NO, significant binding to copper can occur without appreciable enzyme inhibition. The combination of competitive (heme) and noncompetitive (copper) modes of binding enables NO to interact with mitochondria across the full in vivo dynamic range of oxygen tension and consumption rates. bioenergetics | mitochondria | signaling

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jada.2005.04.005 Byline: Jeb Orr, Brenda Davy Abstract: The significant burden of overweight and obesity on our society necessitates the development of lifestyle strategies that facilitate successful long-term body weight management. Recently, the discovery of novel cellular modulators of the brain-gut axis have generated much interest in possible therapeutic manipulation of these and other hormones that regulate energy intake. These modulators include the enterohormones ghrelin, peptide YY 3-36, and cholecystokinin, and the adipocyte-derived hormone leptin. There is some evidence that dietary macronutrient composition can influence concentrations of these hormones, which could impact sensations of hunger, satiety, and ultimately energy intake. The purpose of this review is to provide background information on these four peripheral hormones involved in energy intake regulation, to discuss what is currently known about their mechanism of action, and to present research findings related to the effect of macronutrient composition on concentrations and efficacy of these hormones. Potential applications of this information are also discussed. Article Note: (footnote) Continuing Education Questionnaire, page 1126 Display Omitted Meets Learning Need Codes 2000, 2070, 5000, and 5370

Measuring the numerical abundance and average body size of individuals of each species in an ecological community's food web reveals new patterns and illuminates old ones. This approach is illustrated using data from the pelagic community of a small lake: Tuesday Lake, Michigan, United States. Body mass varies almost 12 orders of magnitude. Numerical abundance varies almost 10 orders of magnitude. Biomass abundance (average body mass times numerical abundance) varies only 5 orders of magnitude. A new food web graph, which plots species and trophic links in the plane spanned by body mass and numerical abundance, illustrates the nearly inverse relationship between body mass and numerical abundance, as well as the pattern of energy flow in the community. Species with small average body mass occur low in the food web of Tuesday Lake and are numerically abundant. Larger-bodied species occur higher in the food web and are numerically rarer. Average body size explains more of the variation in numerical abundance than does trophic height. The trivariate description of an ecological community by using the food web, average body sizes, and numerical abundance includes many well studied bivariate and univariate relationships based on subsets of these three variables. We are not aware of any single community for which all of these relationships have been analyzed simultaneously. Our approach demonstrates the connectedness of ecological patterns traditionally treated as independent. Moreover, knowing the food web gives new insight into the disputed form of the allometric relationship between body mass and abundance. allometry | biomass spectrum | body mass | energetics | pelagic zone

In aquatic invertebrates that form exoskeletons, the partitioning of energy between skeletal and tissue growth is an important tradeoff, especially under resource limitation or physiological stress. Here, we provide the first comparative analysis of energy investment into tissue and skeleton in corals. We develop a mathematical growth model based on colony geometry, tissue mass and quality (enthalpy), and predicted cost of calcification. For hemispherical colonies, the model predicts greater investment in tissue at small sizes, but a shift to skeletal-dominated growth at colony sizes greater than 5-14 cm radius, depending on tissue mass and quality. A similar transition occurs in branches, but is a function of radius and length. An experimental study to assess the impact of resource (light) limitation and physiological stress (sediment load) on energy partitioning in small hemispherical colonies (Goniastrea retiformis Lamarck) and branches (Porites cylindrica Dana) showed that tissue mass and quality varies greatly over small increments in colony or branch size. In particular, allocations to tissue growth varied tenfold (from positive to negative) more across sediment treatments than did allocations to skeletal growth. A model of energy acquisition versus loss (scope for growth) indicated that tissue growth is more responsive to resource variation and physiological stress than skeletal growth. These results suggest that (1) skeletal and tissue growth rates are weakly correlated across environmental conditions, and that (2) variation in tissue properties is a better proxy for coral health or stress than skeletal growth.

The relationship among Pseudo-nitzschia distributions, particulate toxin levels in seawater, and the energetic and highly variable water masses of an upwelling-dominated region are explored using data collected during summer cruises off the Washington coast in 1997 and 1998. In the early summer of both years, an area of maximum domoic acid (DA) accumulation was located approximately 50 km off the coast within a counterclockwise, cold feature known as the Juan de Fuca eddy. The stations in the eddy with the highest domoic acid concentrations coincided with high numbers of Pseudo-nitzschia pseudodelicatissima (Hasle) Hasle (2.7 [micro]g DA equivalents [L.sup.-1], up to 0.6 x [10.sup.6] cells [L.sup.-1] in 1997 and 0.2 [micro]g DA equivalents [L.sup.-1], up to 0.2 x [10.sup.6] cells [L.sup.-1] in 1998), a species known to produce toxin in this region. Other known toxin-producing species were sometimes present, but at 0.1 [micro]g DA equivalents [L.sup.-1] were measured. In 1998, large-scale surveys indicated that high levels of particulate DA in seawater persisted at least until 1 October, covering a maximum area of 100 [km.sup.2] off the Washington coast in midsummer. The appearance of high levels of DA (up to 2.7 [micro]g DA equivalents [L.sup.-1]), coincident with high numbers of P. pseudodelicatissima (up to 15.4 x [10.sup.6] cells [L.sup.-1]) at Kalaloch beach on the central coast in late September, was followed by the accumulation of record levels of toxin in razor clams. This toxic episode was preceded by a downwelling-favorable wind event, with associated onshore transport in near-surface layers. We suggest that the Juan de Fuca eddy may be one source of DA to the Washington coast. The duration of upwelling and the exact timing of fall storms likely play an influential role in the intensity of the bloom and the movement of toxic cells from the eddy to the coast.

Results indicate that the hydrophobic effect does not contribute much to the energetics of sequence-specific association of the DNA-binding domain of the murine PU.1 transcription factor to the gamma B site of the murine immunoglobulingamma 2-4 enhancer.

Research discusses the mechanism of nitric oxide reduction by nitric oxide reductase in bacteria. Data indicate a trans mechanism and involves the binuclear active site Fe(sub)B. Alternatively, nitric oxide reductase can also use a P-450-type mechanism with heme b(sub03 functioning as nitric oxide binding site.

Reaction centres are complexes of pigment and protein that convert the electromagnetic energy of sunlight into chemical potential energy. They are found in plants, algae and a variety of bacterial species, and vary greatly in their composition and complexity. New structural information has highlighted features that are common to the different types of reaction centre and has provided insights into some of the key differences between reaction centres from different sources. New ideas have also emerged on how contemporary reaction centres might have evolved and on the possible origin of the first chlorophyll-protein complexes to harness the power of sunlight.

Natural respiration rates of suspension feeders in temperate ecosystems are still poorly known. This lack of information constrains our understanding of the functioning and dynamics of benthic marine ecosystems in temperate areas. We examined the in situ seasonal variation in respiration rate of three benthic suspension feeders (a sponge, an ascidian, and a gorgonian) in northwestern Mediterranean sublittoral communities using a recirculating flow respirometry system. The in situ technique is shown to be highly applicable to seasonal studies of the physiological energetics of benthic suspension feeders. Respiration rates of the three species varied two- to threefold through the annual cycle, exhibiting a marked seasonal pattern but showing no daily cycle or significant day-to-day variability within months. The respiration rate of the sponge and ascidian, active suspension feeders, increased with temperature. The respiration rate of the gorgonian, a passive suspension feeder, did not correlate with temperature. We estimated a [Q.sub.10] of 1.1, which indicates that respiration rate in this species is not highly dependent on temperature. Synthesis of new tissue of some Mediterranean benthic suspension feeders, such as gorgonians, does not correlate with temperature, which allowed us to isolate the effects of temperature and synthesis of new tissue on respiration rate. Synthesis of new tissue increased respiration rate of the gorgonian by ~40%. The low rate of synthesis of new tissue during summer, together with the contraction of polyps and the low [Q.sub.10], explains the low respiration rates of the gorgonian observed during the period of highest temperature. These low respiration rates support the hypothesis that energy limitations may underlie summer dormancy in some benthic suspension-feeding taxa in the Mediterranean.

Research has been conducted on the two sibling zooplankton copepod organisms. The differences in the life cycle timing among these species have been investigated with regard to foraging strategies, generation numbers, bioenergetics and predator avoidance.

Results show that Clostridium beijerinckii flavodoxin exhibits a sequence specificity of its reverse turn in association with flavin mononucleotide cofactor during modulation of its reduction potentials. Site-directed mutagenesis experiments demonstrate that there is a direct correlation between redox potentials and the conformational stability of the four-residue reverse turn.

Objective: (1) To evaluate inter-individual variations, regional and sex differences in the basal metabolic rate (BMR) and related variables; (2) to compare measured BMR with estimated BMR using predictive equations; and (3) to examine the net mechanical efficiency (NME) in step tests. Design: BMR and energy costs at rest and during step tests were measured by the Douglas bag technique of indirect calorimetry. NME was calculated from BMR and energy costs of step tests. Setting: Rural villages under subsistence agriculture and urban settlements under cash economy. Subjects: Adult males and females (n=33) including 16 rural villagers and 17 urban migrants. Interventions: Step exercise test. Results: There were significant regional differences in BMR (per body weight) in both sexes. The BMR predicted by Schofield equation correlated with the measured BMR (- 1 to + 3%), while the BMR predicted by Henry and Rees equations under-estimated the measured BMR by 6-11%. NME was higher in urban subjects with larger body size than in rural subjects for both sexes, albeit insignificantly. NME tended to be higher with increased stepping level in both sexes. Conclusions: Urban migrants had lower BMR than rural dwellers, and the BMR predicted by Schofield equation correlated with the measured BMR in both sub-groups. Sponsorship: The United Nations University Project on People, Land Management and Environmental Change. Descriptors: basal metabolic rate; resting metabolic rate; step test; net mechanical efficiency; Papua New Guinea; rural and urban comparison, Introduction The FAO/WHO/UNU Expert Consultation (1985) adopted the principle of relying on estimates of energy expenditure to assess the energy requirements of adults. Basal metabolic rate (BMR) constitutes between 60 [...]

Thirty-six primiparous heifers were used to determine the effect of dietary energy on postpartum interval, milk production, serum concentrations of insulin, insulin-like growth factor I (IGF-I), growth hormone, and cerebrospinal fluid (CSF) concentrations of neuropeptide-Y (NPY). Low-quality hay was fed during the last trimester of pregnancy to achieve suboptimal calving weight (370 +/- 5 kg) and condition score (4.0 +/- .1). After calving, cows were allotted to one of four dietary treatments that differed in metabolizable energy. Experimental diets were fed at 2.5% of shrunk body weight and formulated to provide 1.8 (low), 2.1 (maintenance), 2.4 (maintenance high), or 2.7 (high) Mcal of ME/kg DM. Daily milk production was estimated at approximately 30, 60, and 90 d postpartum. Condition score change and weight change were defined as change from calving to d 90 postpartum. As energy intake increased, condition score change (P < .001), IGFI (P < .001) and insulin (P < .01) increased and postpartum interval decreased (P = .04). No relationship existed between postpartum interval and CSF concentration of NPY (P > .1). Condition score change was positively associated with IGF-I and insulin (r = .71, P < .001; r = .38, P = .02, respectively) and negatively associated with GH (r = -.67, P < .001). Weight change and serum concentrations of GH did not differ (P > .10) among treatments. Increasing dietary energy intake was associated with a curvilinear increase in milk yield (P = .04) and percentage milk fat (P = .03) and a linear increase (P = .04) in energy available for milk production. Greater milk yield at d 30 was associated with a longer postpartum interval (r = .34, P < .05). In conclusion, a greater proportion of net energy is partitioned to maternal tissue realimentation when cows receive high compared to low-, maintenance-, or moderate-energy diets. Key Words: Beef Cows, Energy Balance, Milk Production, Postpartum Interval

According to the simplest model of the earth's radiative balance, global warming will occur with certainty as humankind increases its production and consumption of nonsolar energy. This prediction is revisited, using a broader model that allows the greenhouse effect to be considered. The new model predicts a global warming of (mathematical expression not reproducible in ASCII) = (114 K)(sub epsilon), where (epsilon) is the rate of surface energy release in units of the average incident solar radiation, 342 W m(super -2), and (mathematical expression not reproducible in ASCII) is the average temperature rise at the earth's surface. Present values of these quantities, excluding geothermal sources, are (epsilon) = 0.69 x 10(super -4) and (mathematical expression not reproducible in ASCII) = 7.9mK. The model assigns a small number of optical parameters to the atmosphere and surface and qualifies the simple warming prediction: It is rigorous only if parameters other than (epsilon) are unchanged. The model is not complex and should serve as an aid to an elementary understanding of global warming.

Research was conducted to evaluate the action of carvacrol, a food additive, on food-borne pathogenic bacterial cells. Results show that the hydrophobic compound changes the permeability of cells, abolishing ion gradient, and causing cell death.

The purpose of this paper is to put forward a new estimate, in the context of previous assessments, of the annual global mean energy budget. A description is provided of the source of each component to this budget. The top-of-atmosphere shortwave and longwave flux of energy is constrained by satellite observations. Partitioning of the radiative energy throughout the atmosphere is achieved through the use of detailed radiation models for both the longwave and shortwave spectral regions. Spectral features of shortwave and longwave fluxes at both the top and surface of the earth's system are presented. The longwave radiative forcing of the climate system for both clear (125 [W m.sup.-2]) and cloudy (155 W [m.sup.-2]) conditions are discussed. The authors find that for the clear sky case the contribution due to water vapor to the total longwave radiative forcing is 75 [W m.sup-2], while for carbon dioxide it is 32 W [m.sup.-2]. Clouds alter these values, and the effects of clouds on both the longwave and shortwave budget are addressed. In particular, the shielding effect by clouds on absorption and emission by water vapor is as large as the direct cloud forcing. Because the net surface heat budget must balance, the radiative fluxes constrain the sum of the sensible and latent heat fluxes, which can also be estimated independently.

Energy expenditure analysis in adults of 18-64 years of age in affluent societies confirms the substantial and progressive increase of habitual energy expenditure in obesity. Physical activity patterns in less-than-massive obesity appear to be similar at various levels of body mass index. The claims that obese persons retain their weight despite very low energy intake conflict with the results of this analysis. An inactive lifestyle can, however, have a significant general risk aspect for the development of obesity.

Intracellular PO2 of less than four mmHg is the critical level of O2 in the myocardium, below which a series of physiological and metabolic changes occur in the cells. At four mmHg of PO2, the formation of lactate increases while the rate pressure product decreases and at two mmHg there is a change in the myocardial O2 consumption and PCr. These changes are a result of the effect of low concentration of oxygen on NADP. If the intracellular PO2 is more than four mmHg the cell does not show any signs of oxygen starvation.

A study of the feeding habits of the two most abundant bioeroding parrotfish species on the Great Barrier Reef, Australia, Chlorurus gibbus and C. sordidus, reveals that both species have similar feeding patterns, which are initiated and terminated in an abrupt manner. While C. gibbus displayed limited time of day or seasonal variations in feeding rates, C. sordidus underwent major variations in feeding rates as a result of seasonal effects.

A study of separated cardiomyocytes from rats fed with ethanol pellets for six months revealed that average levels of ethanol intake in protein-regulated conditions induced subclinical variations of cardiomyocyte ultrastructure and cell morphology changes in the rats. Variations in the myocytes' energy homeostasis and constrained sacrolemmal adenosine transport were precursors to histological alterations in the sample.

Estimates of metabolizability of organic matter, gross energy, nitrogen and cell wall parts of pelleted alfalfa by Lesser Snow Geese suggested correlations between body size of these birds and patterns of energy processing. These species and most other herbivorous birds, despite having good rates of energy-retention, seem to lose energy in the form of heat generated while eating.

A study of clutch size and removal indeterminacy of House Sparrows revealed the indeterminate pattern of laying eggs and the influence of endogenous energy reserves on the clutch size of these birds. Egg production in the species was directly influenced by the levels of exogenous and nutrient energy resources and only to a marginal degree by the female's endogenous reserves. The quantity of lipid reserves determine the clutch size in the females.

A study of the foraging strategies employed by 269 Wood Storks revealed their preference for straight flying paths in travelling to foraging sites in the vicinity of their colonies. Energy consumption in these birds remained stable, despite their usage of energetically conservative soaring flight in covering longer foraging distances at the end of their breeding season.