Increased tricarboxylic acid cycle flux in rat brain during forepaw stimulation detected with 1H[13C]NMR.

NMR spectroscopy was used to test recent proposals that the additional energy required for brain activation is provided through nonoxidative glycolysis. Using localized NMR spectroscopic methods, the rate of C4-glutamate isotopic turnover from infused [1-(13)C]glucose was measured in the somatosensory cortex of rat brain both at rest and during forepaw stimulation. Analysis of the glutamate turnover data using a mathematical model of cerebral glucose metabolism showed that the tricarboxylic acid cycle flux [(V(TCA)] increased from 0.49 +/- 0.03 at rest to 1.48 +/- 0.82 micromol/g/min during stimulation (P < 0.01). The minimum fraction of C4-glutamate derived from C1-glucose was approximately 75%, and this fraction was found in both the resting and stimulated rats. Hence, the percentage increase in oxidative cerebral metabolic rate of glucose use (CMRglc) equals the percentage increases in V(TCA) and cerebral metabolic rate of oxygen consumption (CMRO2). Comparison with previous work for the same rat model, which measured total CMRglc [Ueki, M., Linn, F. & Hossman, K. A. (1988) J. Cereb. Blood Flow Metab. 8, 486-4941, indicates that oxidative CMRglc supplies the majority of energy during sustained brain activation.

Amygdala activity at encoding correlated with long-term, free recall of emotional information.

Positron emission tomography of cerebral glucose metabolism in adult human subjects was used to investigate amygdaloid complex (AC) activity associated with the storage of long-term memory for emotionally arousing events. Subjects viewed two videos (one in each of two separate positron emission tomography sessions, separated by 3-7 days) consisting either of 12 emotionally arousing film clips ("E" film session) or of 12 relatively emotionally neutral film clips ("N" film session), and rated their emotional reaction to each film clip immediately after viewing it. Three weeks after the second session, memory for the videos was assessed in a free recall test. As expected, the subjects' average emotional reaction to the E films was higher than that for the N films. In addition, the subjects recalled significantly more E films than N films. Glucose metabolic rate of the right AC while viewing the E films was highly correlated with the number of E films recalled. AC activity was not significantly correlated with the number of N films recalled. The findings support the view derived from both animal and human investigations that the AC is selectively involved with the formation of enhanced long-term memory associated with emotionally arousing events.

Antidiabetic thiazolidinediones inhibit leptin (ob) gene expression in 3T3-L1 adipocytes.

Lack of leptin (ob) protein causes obesity in mice. The leptin gene product is important for normal regulation of appetite and metabolic rate and is produced exclusively by adipocytes. Leptin mRNA was induced during the adipose conversion of 3T3-L1 cells, which are useful for studying adipocyte differentiation and function under controlled conditions. We studied leptin regulation by antidiabetic thiazolidinedione compounds, which are ligands for the adipocyte-specific nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) that regulates the transcription of other adipocyte-specific genes. Remarkably, leptin gene expression was dramatically repressed within a few hours after thiazolidinedione treatment. The ED50 for inhibition of leptin expression by the thiazolidinedione BRL49653 was between 5 and 50 nM, similar to its Kd for binding to PPARgamma. The relatively weak, nonthiazolidinedione PPAR activator WY 14,643 also inhibited leptin expression, but was approximately 1000 times less potent than BRL49653. These results indicate that antidiabetic thiazolidinediones down-regulate leptin gene expression with potencies that correlate with their abilities to bind and activate PPARgamma.

Shell size, body mass and average pO2 in mantle cavity water of different marine mollusc species

Marine invertebrates with open circulatory system establish low and constant oxygen partial pressure (Po2) around their tissues. We hypothesized that as a first step towards maintenance of low haemolymph and tissue oxygenation, the Po2 in molluscan mantle cavity water should be lowered against normoxic (21 kPa) seawater Po2, but balanced high enough to meet the energetic requirements in a given species. We recorded Po2 in mantle cavity water of five molluscan species with different lifestyles, two pectinids (Aequipecten opercularis, Pecten maximus), two mud clams (Arctica islandica, Mya arenaria), and a limpet (Patella vulgata). All species maintain mantle cavity water oxygenation below normoxic Po2. Average mantle cavity water Po2 correlates positively with standard metabolic rate (SMR): highest in scallops and lowest in mud clams. Scallops show typical Po2 frequency distribution, with peaks between 3 and 10 kPa, whereas mud clams and limpets maintain mantle water Po2 mostly <5 kPa. Only A. islandica and P. vulgata display distinguishable temporal patterns in Po2 time series. Adjustment of mantle cavity Po2 to lower than ambient levels through controlled pumping prevents high oxygen gradients between bivalve tissues and surrounding fluid, limiting oxygen flux across the body surface. The patterns of Po2 in mantle cavity water correspond to molluscan ecotypes.

Heat stress, heat strain, and productivity in Washington State tree fruit harvesters

Thesis (Master's)--University of Washington, 2016-06

Reducing the time period of steady state does not affect the accuracy of energy expenditure measurements by indirect calorimetry

Achievement of steady state during indirect calorimetry measurements of resting energy expenditure (REE) is necessary to reduce error and ensure accuracy in the measurement. Steady state is often defined as 5 consecutive min (5-min SS) during which oxygen consumption and carbon dioxide production vary by +/-10%. These criteria, however, are stringent and often difficult to satisfy. This study aimed to assess whether reducing the time period for steady state (4-min SS or 3-min SS) produced measurements of REE that were significantly different from 5-min SS. REE was measured with the use of open-circuit indirect calorimetry in 39 subjects, of whom only 21 (54%) met the 5-min SS criteria. In these 21 subjects, median biases in REE between 5-min SS and 4-min SS and between 5-min SS and 3-min SS were 0.1 and 0.01%, respectively. For individuals, 4-min SS measured REE within a clinically acceptable range of +/-2% of 5-min SS, whereas 3-min SS measured REE within a range of -2-3% of 5-min SS. Harris-Benedict prediction equations estimated REE for individuals within +/-20-30% of 5-min SS. Reducing the time period of steady state to 4 min produced measurements of REE for individuals that were within clinically acceptable, predetermined limits. The limits of agreement for 3-min SS fell outside the predefined limits of +/-2%; however, both 4-min SS and 3-min SS criteria greatly increased the proportion of subjects who satisfied steady state within smaller limits than would be achieved if relying on prediction equations.

Costs increase as ritualized fighting progresses within and between phases in the sierra dome spider, Neriene litigiosa

Magnitudes and patterns of energy expenditure in animal contests are seldom measured, but can be critical for predicting contest dynamics and understanding the evolution of ritualized fighting behaviour. In the sierra dome spider, males compete for sexual access to females and their webs. They show three distinct phases of fighting behaviour, escalating from ritualized noncontact display (phase 1) to cooperative wrestling (phase 2), and finally to unritualized, potentially fatal fighting (phase 3). Using CO2 respirometry, we estimated energetic costs of male-male combat in terms of mean and maximum metabolic rates and the rate of increase in energy expenditure. We also investigated the energetic consequences of age and body mass, and compared fighting metabolism to metabolism during courtship. All three phases involved mean energy expenditures well above resting metabolic rate (3.5 X, 7.4 X and 11.5 X). Both mean and maximum energy expenditure became substantially greater as fights escalated through successive phases. The rates of increase in energy use during phases 2 and 3 were much higher than in phase 1. In addition, age and body mass affected contest energetics. These results are consistent with a basic prediction of evolutionarily stable strategy contest models, that sequences of agonistic behaviours should be organized into phases of escalating energetic costs. Finally, higher energetic costs of escalated fighting compared to courtship provide a rationale for first-male sperm precedence in this spider species. (C) 2004 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

Measurement and prediction of energy expenditure in males during household and garden tasks

Participation in at least 30 min of moderate intensity activity on most days is assumed to confer health benefits. This study accordingly determined whether the more vigorous household and garden tasks (sweeping, window cleaning, vacuuming and lawn mowing) are performed by middle-aged men at a moderate intensity of 3-6 metabolic equivalents (METs) in the laboratory and at home. Measured energy expenditure during self-perceived moderate-paced walking was used as a marker of exercise intensity. Energy expenditure was also predicted via indirect methods. Thirty-six males [Xmacr (SD): 40.0 (3.3) years; 179.5 (6.9) cm; 83.4 (14.0) kg] were measured for resting metabolic rate (RMR) and oxygen consumption (V.O-2) during the five activities using the Douglas bag method. Heart rate , respiratory frequency, CSA (Computer Science Applications) movement counts, Borg scale ratings of perceived exertion and Quetelet's index were also recorded as potential predictors of exercise intensity. Except for vacuuming in the laboratory, which was not significantly different from 3.0 METs (P=0.98), the MET means in the laboratory and home were all significantly greater than 3.0 (Pless than or equal to0.006). The sweeping and vacuuming MET means were significantly higher (P

Anabolic responses to resistance training in older men and women: A brief review

Resistance training has been shown to be the most effective exercise mode to induce anabolic adaptations in older men and women. Advances in imaging techniques and histochemistry have increased the ability to detect such changes, confirming the high level of adaptability that remains in aging skeletal muscle. This brief review presents a summary of the resistance-training studies that directly compare chronic anabolic responses to training in older (> 60 years) men and women. Sixteen studies are summarized, most of which indicate similar relative anabolic responses between older men and women after resistance training. Relatively small sample sizes in most of the interventions limited their ability to detect significant sex differences and should be considered when interpreting these studies. Future research should incorporate larger sample sizes with multiple measurement time points for anabolic responses.

Effects of electrical muscle stimulation on oxygen consumption

Electrical muscle stimulation (EMS) devices are being marketed as weight/ fat loss devices throughout the world. Commercially available stimulators have the ability to evoke muscle contractions that may affect caloric expenditure while the device is being used. The aim of this study was to test the effects of two different EMS devices (Abtronic and Feminique) on oxygen consumption at rest. Subjects arrived for testing after an overnight fast, had the devices fitted, and then positioned supine with expired air measured to determine oxygen consumption. After a 10-minute acclimation period, oxygen consumption was measured for 20 minutes with the device switched off (resting) then 20 minutes with the device switched on (stimulated). There were no significant differences (P > 0.05) in oxygen consumption between the resting and stimulated periods with either the Abtronic (mean SD; resting, 3.40 +/- 0.44; stimulated, 3.45 +/- 0.53 ml of O-2.kg(-1).min(-1)) or the Feminique (resting, 3.73 +/- 0.45; stimulated, 3.75 +/- 0.46 ml of O-2.kg(-1).min(-1)). In summary, the EMS devices tested had no effect on oxygen consumption during muscle stimulation.

Subthalamic nucleus neurones in slices from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned mice show irregular, dopamine-reversible firing pattern changes, but without synchronous activity

The loss of dopamine in idiopathic or animal models of Parkinson's disease induces synchronized low-frequency oscillatory burst-firing in subthalamic nucleus neurones. We sought to establish whether these firing patterns observed in vivo were preserved in slices taken from dopamine-depleted animals, thus establishing a role for the isolated subthalamic-globus pallidus complex in generating the pathological activity. Mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) showed significant reductions of over 90% in levels of dopamine as measured in striatum by high pressure liquid chromatography. Likewise, significant reductions in tyrosine hydroxylase immunostaining within the striatum (>90%) and tyrosine hydroxylase positive cell numbers (65%) in substantia nigra were observed. Compared with slices from intact mice, neurones in slices from MPTP-lesioned mice fired significantly more slowly (mean rate of 4.2 Hz, cf. 7.2 Hz in control) and more irregularly (mean coefficient of variation of inter-spike interval of 94.4%, cf. 37.9% in control). Application of ionotropic glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 2-amino-5-phosphonopentanoic acid (AP5) and the GABAA receptor antagonist picrotoxin caused no change in firing pattern. Bath application of dopamine significantly increased cell firing rate and regularized the pattern of activity in cells from slices from both MPTP-treated and control animals. Although the absolute change was more modest in control slices, the maximum dopamine effect in the two groups was comparable. Indeed, when taking into account the basal firing rate, no differences in the sensitivity to dopamine were observed between these two cohorts. Furthermore, pairs of subthalamic nucleus cells showed no correlated activity in slices from either control (21 pairs) or MPTP-treated animals (20 pairs). These results indicate that the isolated but interconnected subthalamic-globus pallidus network is not itself sufficient to generate the aberrant firing patterns in dopamine-depleted animals. More likely, inputs from other regions, such as the cortex, are needed to generate pathological oscillatory activity. © 2006 IBRO.

Effect of a tumour-derived lipid-mobilising factor on glucose and lipid metabolism in vivo

Treatment of ex-breeder male NMRI mice with lipid mobilising factor isolated from the urine of cachectic cancer patients, caused a significant increase in glucose oxidation to CO2, compared with control mice receiving phosphate buffered saline. Glucose utilisation by various tissues was determined by the 2-deoxyglucose tracer technique and shown to be elevated in brain, heart, brown adipose tissue and gastrocnemius muscle. The tissue glucose metabolic rate was increased almost three-fold in brain, accounting for the ability of lipid mobilising factor to decrease blood glucose levels. Lipid mobilising factor also increased overall lipid oxidation, as determined by the production of 14CO2 from [14C carboxy] triolein, being 67% greater than phosphate buffered saline controls over a 24 h period. There was a significant increase in [14C] lipid accumulation in plasma, liver and white and brown adipose tissue after administration of lipid mobilising factor. These results suggest that changes in carbohydrate metabolism and loss of adipose tissue, together with an increased whole body fatty acid oxidation in cachectic cancer patients, may arise from tumour production of lipid mobilising factor. © 2002 Cancer Research UK.

Effects of ocean acidification on embryonic respiration and development of a temperate wrasse living along a natural CO2 gradient

Volcanic CO2 seeps provide opportunities to investigate the effects of ocean acidification on organisms in the wild. To understand the influence of increasing CO2 concentrations on the metabolic rate (oxygen consumption) and the development of ocellated wrasse early life stages, we ran two field experiments, collecting embryos from nesting sites with different partial pressures of CO2 [pCO2; ambient (400 µatm) and high (800-1000 µatm)] and reciprocally transplanting embryos from ambient- to high-CO2 sites for 30 h. Ocellated wrasse offspring brooded in different CO2 conditions had similar responses, but after transplanting portions of nests to the high-CO2 site, embryos from parents that spawned in ambient conditions had higher metabolic rates. Although metabolic phenotypic plasticity may show a positive response to high CO2, it often comes at a cost, in this case as a smaller size at hatching. This can have adverse effects because smaller larvae often exhibit a lower survival in the wild. However, the adverse effects of increased CO2 on metabolism and development did not occur when embryos from the high-CO2 nesting site were exposed to ambient conditions, suggesting that offspring from the high-CO2 nesting site could be resilient to a wider range of pCO2 values than those belonging to the site with present-day pCO2 levels. Our study identifies a crucial need to increase the number of studies dealing with these processes under global change trajectories and to expand these to naturally high-CO2 environments, in order to assess further the adaptive plasticity mechanism that encompasses non-genetic inheritance (epigenetics) through parental exposure and other downstream consequences, such as survival of larvae.

Investigations on the Chilean kelp crab Taliepus dentatus

Physiological responses of larval stages can differ from those of the adults, affecting key ecological processes. Therefore, developing a mechanistic understanding of larval responses to environmental conditions is essential vis-à-vis climate change. We studied the thermal tolerance windows, defined by lower and upper pejus (Tp) and critical temperatures (Tc), of zoea I, II, and megalopa stages of the Chilean kelp crab Taliepus dentatus. Tp limits determine the temperature range where aerobic scope is maximal and functioning of the organism is unrestrained and were estimated from direct observations of larval activity. Tc limits define the transition from aerobic to anaerobic metabolism, and were estimated from the relationship between standard metabolic rate and temperature. Zoea I showed the broadest, Zoea II an intermediate, and megalopae the narrowest tolerance window (Tp). Optimum performance in megalopae was limited to Tp between 11 and 15°C, while their Tc ranged between 7 and 19°C. Although Tc may be seldom encountered by larvae, the narrower Tp temperatures can frequently expose larvae to unfavorable conditions that can drastically constrain their performance. Temperatures beyond the Tp range of megalopae have been observed in most spring and summer months in central Chile, and can have important consequences for larval swimming performance and impair their ability to avoid predators or settle successfully. Besides the well-documented effects of temperature on development time, variability in field temperatures beyond Tp can affect performance of particular larval stages, which could drive large-scale variability in recruitment and population dynamics of T. dentatus and possibly other invertebrate species.

Chlorofluorocarbons, helium, and neon measured on water bottle samples during POLARSTERN cruise ANT-XXII/2 (ISPOL)

During Ice Station POLarstern (ISPOL; R.V. Polarstern cruise ANT XXII/2, November 2004-January 2005), hydrographic and tracer observations were obtained in the western Weddell Sea while drifting closely in front of the Larsen Ice Shelf. These observations indicate recently formed Weddell Sea Bottom Water, which contains significant contributions of glacial melt water in its upper part, and High-Salinity Shelf Water in its lower layer. The formation of this bottom water cannot be related to the known sources in the south, the Filchner-Ronne Ice Shelf. We show that this bottom water is formed in the western Weddell Sea, most likely in interaction with the Larsen C Ice Shelf. By applying an Optimum Multiparameter Analysis (OMP) using temperature, salinity, and noble gas observations (helium isotopes and neon), we obtained mean glacial melt-water fractions of about 0.1% in the bottom water. On sections across the Weddell Gyre farther north, melt-water fractions are still on the order of 0.04%. Using chlorofluorocarbons (CFCs) as age tracers, we deduced a mean transit time between the western source and the bottom water found on the slope toward the north (9±3 years). This transit time is larger and the inferred transport rate is small in comparison to previous findings. But accounting for a loss of the initially formed bottom water volume due to mixing and renewal of Weddell Sea Deep Water, a formation rate of 1.1±0.5 Sv in the western Weddell Sea is plausible. This implies a basal melt rate of 35±19 Gt/year or 0.35±0.19 m/year at the Larsen Ice Shelf. This bottom water is shallow enough that it could leave the Weddell Basin through the gaps in the South Scotia Ridge to supply Antarctic Bottom Water. These findings emphasize the role of the western Weddell Sea in deep- and bottom-water formation, particularly in view of changing environmental conditions due to climate variability, which might induce enhanced melting or even decay of ice shelves.