Moderate Ambient Temperatures Research Articles

Hepatic gene expression profiling of 5'-AMP-induced hypometabolism in mice.

There is currently much interest in clinical applications of therapeutic hypothermia. Hypothermia can be a consequence of hypometabolism. We have recently established a procedure for the induction of a reversible deep hypometabolic state in mice using 5'-adenosine monophosphate (5'-AMP) in conjunction with moderate ambient temperature. The current study aims at investigating the impact of this technology at the gene expression level in a major metabolic organ, the liver. Our findings reveal that expression levels of the majority of genes in liver are not significantly altered by deep hypometabolism. However, among those affected by hypometabolism, more genes are differentially upregulated than downregulated both in a deep hypometabolic state and in the early arousal state. These altered gene expression levels during 5'-AMP induced hypometabolism are largely restored to normal levels within 2 days of the treatment. Our data also suggest that temporal control of circadian genes is largely stalled during deep hypometabolism.

Development of an Inundative, Aerial Release Technique for the Arundo Wasp1, Biological Control Agent of the InvasiveArundo donaxL.

A box aerial-release system has been developed for the mass release of the arundo wasp, Tetramesa romana Walker, a biological control agent of giant reed, Arundo donax L., an invasive weed of waterways and riparian areas in the southwestern U.S. and Mexico. Because A. donax infests lengthy stretches of remote areas inaccessible by vehicle, an aerial release system may be the best way to disseminate biological control agents. The release system involves a paper box that can be easily loaded with chilled, immobile insects. The box opens upon contact with blades installed on a chute in the floor of an airplane. Preliminary tests in the field demonstrated the effectiveness of this system. All boxes recovered after test releases were successfully opened by the release chutes. Post-release emergence rates of insects were great and insect mortality rates were low, especially at moderate ambient temperatures (20–25°C). The box aerial-release system proves to be an appropriate method for release, especially at the early stages of an inundative biological control program for A. donax.

The effect of high ambient temperature on Ca, P and Mg balance and bone turnover in high‐yielding dairy cows

We investigated the effect of heat stress on Ca, P and Mg balance and bone turnover in lactating cows. In a 2 x 2 crossover design, four multiparous lactating Holstein cows were kept in a chamber and subjected to a constant moderate (18 degrees C) ambient temperature (MT) or high (28 degrees C) ambient temperature (HT). The cows were fed total mixed ration (Ca, 0.7%; P, 0.4%; Mg, 0.2%) ad libitum. The milk yield under HT (35.4 kg/day) tended to be lower (P < 0.10) than that under MT (43.2 kg/day). The concentrations of milk P (P < 0.05) and Mg (P < 0.01) were significantly lower under HT than MT. The Ca, P and Mg intake (P < 0.10); Ca (P < 0.10), P, and Mg (P < 0.05) secretion into milk; and Ca (P < 0.05), P (P < 0.01), and Mg (P < 0.05) absorption in the intestine were lower under HT than MT. The plasma osteocalcin, a marker of bone turnover, was significantly lower (P < 0.05) under HT than MT. Heat stress did not affect plasma C-telopeptide of collagen type I, a bone resorption marker, and plasma parathyroid hormone concentration.

Effect of Ambient Temperature and Light Intensity on Growth Performance and Carcass Characteristics of Heavy Broiler Chickens at 56 Days of Age

The effects of ambient temperature, light intensity and their interaction on growth performance and carcass characteristics of broilers were investigated in 2 trials. The experiment was consisted of a factorial arrangement of treatments in a randomized complete block design. The 9 treatments consisted of 3 levels (Low = 15.6, Moderate = 21.1, High = 26.7 C) of temperatures from d 21-56 d of age and 3 levels (0.5, 3.0, o 20 lx) of light intensities from 8-56 d of age at 50% RH. Five hundred and forty Ross 708 chicks were randomly distributed into 9 environmentally controlled chambers (30 males and 30 females chicks/chamber) at 1 d of age. Feed and water were provided ad libitum. Birds were provided a four phase-feeding program (starter: 1 to 14 d, grower: 15-28 d, finisher: 29-42 d and withdrawal: 43-56 d). At 56 d of age, both feed intake and birds' weight were recorded for the growth performance. Also, 20 (10 males and 10 females) birds from each chamber were processed to determine weights and yields. Broilers subjected to high ambient temperature of 26.7 C had significantly (P<0.05) lower BW, BWG, FI, carcass weight and pectoralis major o and minor weights along with a significant (P<0.05) increased in FCR when compared with low and moderate ambient temperatures broilers. Plasma corticosterone concentrations were not statistically affected by temperature, light intensity or their interaction, suggesting an absence of stress. These results indicate that exposure of modern heavy weight broilers to high ambient temperature of 26.7 C in comparison o with low and moderate ambient temperatures has a negative effect on growth performance and carcass characteristics, suggesting that they need to be grown under lower ambient temperature than previously reported.

Metabolic, ventilatory and hygric physiology of the chuditch ( Dasyurus geoffroii; Marsupialia, Dasyuridae)

The chuditch is a large carnivorous dasyurid marsupial. Historically it had one of the widest geographical distributions of all marsupials, encompassing much of arid Australia, but it is now restricted to the mesic south-west of Western Australia. It is therefore of interest to determine if its physiology better reflects adaptation to its historically arid or present mesic habitat. The basic physiological parameters of the chuditch conform to other marsupials. Body mass of males (1385 g) was > 400% of that predicted by phylogeny and this may be related to its carnivorous diet. Body temperature was 33.9 °C at ambient temperatures ≤ thermoneutrality, with hyperthermia occurring above thermoneutrality. Basal metabolic rate was 0.361 mL O 2 g − 1 h − 1 at an ambient temperature of 31 °C. Metabolic rate increased below the thermoneutral zone by 0.038 mL O 2 g − 1 h − 1 °C − 1 , and above the thermoneutral zone to 0.444 ± 0.059 mL O 2 g − 1 h − 1 at 33.3 °C. Standard evaporative water loss was 0.498 ± 0.071 mg g − 1 h − 1 at an ambient temperature of 26.0 °C, and increased at higher ambient temperatures due to panting and licking. Changes in wet thermal conductance largely reflected changes in evaporative heat loss, and dry thermal conductance increased at high ambient temperature due in part to posture change. Ventilatory parameters were consistent with metabolic demands in and below thermoneutrality, and suggested augmented evaporative heat loss above the thermoneutral zone. Chuditch had a high point of relative water economy of 22.6 °C, indicating favourable water economy at even moderate ambient temperatures, due to its low evaporative water loss rather than high metabolic water production. Chuditch were physiologically more similar to marsupials from arid rather than mesic habitats, better reflecting their historical distribution than their current geographical range.

Thermal insulation capability of PEG-containing polyurethane foams

Polyethylene glycol (PEG) compounds and mixtures have many properties that make them suitable for thermal applications in buildings, such as having high heat of fusion, phase change repeatability, chemical stability, non-corrosive behavior, and low-cost. In this study, we developed a number of PU rigid foams incorporated with three types of PEGs, as new insulation materials provided with an enhanced thermal capacity, and sought their suitability for various applications such as layer of floor and ceiling coverings in constructions, insulations in controlled temperature transportation packaging, inner coverings of automobile seats, etc. In order to investigate the thermal properties of PEG-containing PU foams, differential scanning calorimeter (DSC) tests were conducted first. Then, a two-layer concrete–PU foam system was designed in the laboratory conditions to examine the insulation performances via using a computer-aided thermal measurement setup which was sensitive to the simulated environmental temperature changes. The PU-PEG composites produced here can be helpful for the design of thermal insulators. PUI, including 44% PEG 600, exhibited fairly efficient thermal regulation under moderate ambient temperature conditions, whereas PUII (49% PEG 1000) is suitable for temperature control in both mild and hot surroundings. PUIII, containing 53% PEG 1500, showed suitable heat storage and thermal stability characteristics. PUIV, containing 38% PEG 600/PEG 1000/PEG 1500, also confirmed good thermal and durability characteristics. The blend of three PEGs is suitable for preventing discontinuous thermal regulation when the external temperature increases or decreases. PU foams containing PEGs can be assumed to be leak-resistant, which is promising for their industrial applications.

The Reliability of a 90-minute Preloaded Treadmill Time-Trial in Hot and Moderate Ambient Temperatures

Exercise tests to exhaustion have been shown to have poor test-retest reliability and high levels of within-subject variation (Jeukendrup et al., 1996) as well as lacking direct comparison to sporting events (Hopkins et al., 2001). This has lead to interest in alternative methods of endurance performance assessment such as time-trials (TT) and, for longer protocols, preloaded time-trials (TTpre). Both have been shown to be reproducible methods of endurance assessment in ambient conditions for cycling and running (Doyle and Martinez, 1998; Jeukendrup et al., 1996) however the reliability of such performance tests is unknown in elevated temperatures. PURPOSE: To investigate the reliability of a 90-min treadmill-based TTpre in elevated and moderate temperatures. METHODS: Seven well-trained males (31 ± 8 yrs; 73.5 ± 5.6 kg; 57.68 ± 6.29 ml.kg-1.min-1) completed six 90-min TTpre, three in hot (H) ambient conditions (30.5 ± 0.1°C, 53 ± 2% relative humidity (RH)) and three in moderate (M) ambient conditions (14.4 ± 0.1°C, 59 ± 4% RH). Trials were separated by 7–14 days and conducted on a motorised treadmill. The order of the environmental conditions was randomised. The TTpre consisted of 75-min at ∼60% VO2max immediately followed by a self-paced 15-min TT. During the TT section subjects were instructed to run as far as possible within the 15-min and were given visual feedback of the time remaining. Reliability was assessed via coefficient of variation (CV). The distances covered were compared using paired t-tests. Trial 1 in each condition was considered a familiarisation. Results are presented as percentages for CV and mean ± standard deviation for distances. RESULTS: Subjects ran further in the M than the H trials (90-min TTpre: 16,072 ± 1,366 km vs 15,753 ± 1,307 km, P<0.01; 15-minTT: 3,519 ± 460 km vs 3,213 ± 516 km, P<0.001). The CV for the 90-min protocol was 0.69% (M) and 0.58% (H) which increased to 2.53% (M) and 2.32% (H) when calculated for the 15-min TT section alone. CONCLUSIONS: The 90-min TTpre is a reliable test for the assessment of endurance performance in prolonged treadmill running in males in H and M conditions. Reliability is enhanced in H compared to M conditions.

Investigation of heat and mass transfer between the two phases of an evaporating droplet stream using laser-induced fluorescence techniques: Comparison with modeling

Heat and mass exchanges between the two phases of a spray is a key point for the understanding of physical phenomena occurring during spray evaporation in a combustion chamber. Development and validation of physical models and computational tools dealing with spray evaporation requires experimental databases on both liquid and gas phases. This paper reports an experimental study of evaporating acetone droplets streaming linearly at moderate ambient temperatures up to 75 °C. Two-color laser-induced fluorescence is used to characterize the temporal evolution of droplet mean temperature. Simultaneously, fuel vapor distribution in the gas phase surrounding the droplet stream is investigated using acetone planar laser-induced fluorescence. Temperature measurements are compared to simplified heat and mass transfer model taking into account variable physical properties, droplet-to-droplet interactions and internal fluid circulation within the droplets. The droplet surface temperature, calculated with the model, is used to initiate the numerical simulation of fuel vapor diffusion and transport in the gas phase, assuming thermodynamic equilibrium at the droplet surface. Influence of droplet diameter and droplet spacing on the fuel vapor concentration field is investigated and numerical results are compared with experiments.

Acute Heat Stress Induces Oxidative Stress and Decreases Adaptation in Young White Leghorn Cockerels by Downregulation of Avian Uncoupling Protein

Reactive oxygen species-induced damage of cells and molecules is one of the mechanisms responsible for the decline in an animal's performance due to heat stress. Mitochondria are the main producers of cellular superoxide, a process that is sensitive to proton motive force, and this superoxide production can be decreased by mild uncoupling. We studied the effects of heat stress on the production of mitochondrial superoxide as well as heat stress effects on the expression of avian uncoupling protein (avUCP) and avian A nucleotide translocator (avANT) in skeletal muscles of chicks and young cockerels. Male White Leghorn (Julia) chicks at 16 d and cockerels at 87 d of age were exposed to acute heat stress, 34 degrees C for 18 h, or kept at moderate ambient temperature (25 and 21 degrees C, respectively). There was no difference in mitochondrial superoxide production between heat-exposed and control chicks, whereas significant differences were observed in the case of young cockerels. Greater substrate-independent superoxide production was found in muscle mitochondria from heat-stressed young cockerels. In chicks, neither avUCP nor avANT transcript expression was changed by heat exposure, whereas in young cockerels avUCP transcript was decreased, but avANT transcript level was not changed. Thus, in heat-stressed young cockerels, increased mitochondrial superoxide production was accompanied by downregulation of avUCP. Taken together, these results suggest that exposure of young cockerels to heat stress stimulates mitochondrial superoxide production, possibly via downregulation of avUCP. Chicks with persistent avUCP expression, on the other hand, are relatively better adapted to high temperature. It can be assumed that appropriate expression of avUCP may alleviate overproduction of mitochondrial superoxide and could help birds adapt to oxidative stress resulting from acute heat stress.

Growth Performance, Meat Yield, and Economic Responses of Broilers Fed Diets Varying in Metabolizable Energy from Thirty to Fifty-Nine Days of Age

Two studies examined responses of broilers to diets varying in AME from 30 to 59 d of age. A 59-d termination allows for evaluation of energy needs applicable to “big bird” programs, because research on nutritional needs for such programs is warranted. Two experiments were conducted: experiment (exp.) 1 having low temperatures whereas exp. 2 used moderate temperatures. The treatments in exp. 1 and 2 were AME concentrations ranging from 3,175 to 3,310 kcal/kg with CP, TSAA, and Lys being identical across all treatments. In exp. 2, an additional treatment consisted of a diet containing 3,310 kcal of AME/kg with CP, TSAA, and Lys being increased by 4% of those specifications used in the other treatments so as to minimize differences in energy:CP ratio.In both experiments, feed consumption and conversion decreased linearly as dietary AME increased, but breast meat yield was reduced with the high AME diet and only increasing amino acids in exp. 2 ameliorated the negative effect. Live production costs and gross feeding margin (bird return over feed costs) were optimized in exp. 1 with 3,220 kcal of AME/kg of diet, but 3,310 kcal of AME/kg of diet and increased amino acids were needed in exp. 2 for improved monetary returns. In both experiments, broilers had similar caloric consumption indicating that these broilers can compensate to varying dietary AME concentrations within practical limits. These results demonstrated that the response to dietary AME was more pronounced under moderate ambient temperatures.

Milk Protein Production and Plasma 3-Methylhistidine Concentration in Lactating Holstein Cows Exposed to High Ambient Temperatures

This experiment was performed to examine the influences of high ambient temperature on milk production, nutrient digestibility, energy and protein sufficiency ratio, and plasma metabolites concentration in lactating cows. In a 2×2 crossover design, four multiparous lactating Holstein cows were maintained in a chamber under treatment of constant moderate (18°C) ambient temperature (MT) or high (28°C) ambient temperatures (HT). The DMI and milk protein yield were significantly lower in HT (p<0.05). The milk yield, milk lactose yield, and milk SNF yield tended to be lower in HT (p<0.10). No statistical differences for 4% fat-corrected milk and milk fat yield were observed. Rectal temperatures were significantly higher in HT than MT (p<0.05). The apparent DM, OM, ether extract, CF, and ash digestibility did not differ between treatments. On the other hand, the apparent CP digestibility was increased significantly (p<0.05) and nitrogen free extract tended to increase (p<0.10) in HT. The sufficiency ratio of ME and DCP intake for each requirement tended to be lower in HT than in MT (p<0.10). Concentrations of total protein (TP), albumin, and urea nitrogen in plasma did not differ between treatments. Plasma 3-methylhistidine (3MH) concentration as a marker of myofibrillar protein degradation tended to be higher in HT (p<0.15). In conclusion, high ambient temperature was associated with a lower energy and protein sufficiency ratio,

Effect of ettringite on thaumasite formation

Deterioration of cementitious building materials is often caused by sulphate attack where ettringite and gypsum play the most destructive role at moderate ambient temperatures. In contrast, thaumasite [Ca 3Si(OH) 6·12H 2O](SO 4)(CO 3) is mostly observed at comparatively low temperatures of less then 15 °C. This mineral forms from calcium, sulphate, carbonate and silicon. The latter originates from the decomposition of C–S–H which results in deterioration of the hardened cement paste structure. To investigate the effect of ettringite on thaumasite formation, pastes were mixed using synthetic clinker phases, fly ash and nanosilica. Aqueous suspensions were prepared with the ground-hydrated pastes mixed with calcite and either gypsum or sodium sulphate. Following different storage periods, the solid phase was separated by filtration, dried and analysed by XRD using the Rietveld method as well as ESEM and TEM. The liquid phase was analysed by ICP-OES. The results indicate that thaumasite formation occurs through the heterogeneous nucleation of thaumasite on the surface of ettringite, due to the structural similarities of these minerals. This reaction is followed by further epitaxial growth of thaumasite from its components present in solution.

Heat Stress From Enclosed Vehicles: Moderate Ambient Temperatures Cause Significant Temperature Rise in Enclosed Vehicles

Each year, children die from heat stroke after being left unattended in motor vehicles. In 2003, the total was 42, up from a national average of 29 for the past 5 years. Previous studies found that on days when ambient temperatures exceeded 86 degrees F, the internal temperatures of the vehicle quickly reached 134 to 154 degrees F. We were interested to know whether similarly high temperatures occurred on clear sunny days with more moderate temperatures. The objective of this study was to evaluate the degree of temperature rise and rate of rise in similar and lower ambient temperatures. In addition, we evaluated the effect of having windows "cracked" open. In this observational study, temperature rise was measured continuously over a 60-minute period in a dark sedan on 16 different clear sunny days with ambient temperatures ranging from 72 to 96 degrees F. On 2 of these days, additional measurements were made with the windows opened 1.5 inches. Analysis of variance was used to compare how quickly the internal vehicle temperature rose and to compare temperature rise when windows were cracked open 1.5 inches. Regardless of the outside ambient temperature, the rate of temperature rise inside the vehicle was not significantly different. The average mean increase was 3.2 degrees F per 5-minute interval, with 80% of the temperature rise occurring during the first 30 minutes. The final temperature of the vehicle depended on the starting ambient temperature, but even at the coolest ambient temperature, internal temperatures reached 117 degrees F. On average, there was an approximately 40 degrees F increase in internal temperature for ambient temperatures spanning 72 to 96 degrees F. Cracking windows open did not decrease the rate of temperature rise in the vehicle (closed: 3.4 degrees F per 5 minutes; opened: 3.1 degrees F per 5 minutes or the final maximum internal temperature. Even at relatively cool ambient temperatures, the temperature rise in vehicles is significant on clear, sunny days and puts infants at risk for hyperthermia. Vehicles heat up rapidly, with the majority of the temperature rise occurring within the first 15 to 30 minutes. Leaving the windows opened slightly does not significantly slow the heating process or decrease the maximum temperature attained. Increased public awareness and parental education of heat rise in motor vehicles may reduce the incidence of hyperthermia death and improve child passenger safety.

Factors affecting the biodegradation of PCP by Pseudomonas mendocina NSYSU

A pentachlorophenol (PCP) degrading bacterium was isolated from PCP-contaminated soils and identified as Pseudomonas mendocina NSYSU ( P. mendocina NSYSU). The main objectives of this study were to (1) clarify the factors affecting the ability and efficiency of PCP biodegradation by P. mendocina NSYSU, and (2) optimize the use of this bacterium in bioremediation of PCP. Microcosm experiments were conducted to fulfill the objectives. In batch cultures, P. mendocina NSYSU used PCP as its sole source of carbon and energy and was capable of completely degrading this compound. This was confirmed by the stoichiometric release of chloride ion. Moreover, P. mendocina NSYSU was able to mineralize a high concentration of PCP (150 mg/L). Results from the oxygen concentration experiment reveal that the growth of P. mendocina NSYSU was inhibited under low oxygen and anaerobic conditions. Results indicate that the optimal growth conditions for P. mendocina NSYSU include the following: slightly acidic (6 < pH < 7), aerobic, and relatively moderate ambient temperature (20 °C < temperature < 30 °C) conditions. Addition of extra carbon sources (sodium acetate and glucose) could not enhance the PCP biodegradation. No PCP byproducts were detected after eight days of incubation in this study. This suggests that P. mendocina NSYSU is able to effectively biodegrade PCP and its biodegradation byproducts without the accumulation of inhibitory toxic compounds. Results from this study could be used to assist the optimization of its use in bioremediation of PCP.

Effects of high ambient temperature and restricted feed intake on nitrogen utilization for milk production in lactating Holstein cows

ABSTRACTThree experiments were performed to examine the effects of high ambient temperature and feed restriction on nitrogen (N) utilization in lactating cows. Experiment 1 investigated N utilization in four cows fed ad libitum in a 2 × 2 crossover design under constant moderate (18°C) or high (28°C) ambient temperatures. The milk N secretion (P &lt; 0.01) and protein concentration (P &lt; 0.05) decreased under high ambient temperature. Experiment 2 investigated N utilization in four cows under constant moderate ambient temperature in a 2 × 2 crossover design with ad libitum or 70% ad libitum feed intake. The milk N secretion and protein concentration both decreased with feed restriction (P &lt; 0.05). Experiment 3 investigated N utilization in four cows fed 70% ad libitum in a 2 × 2 crossover design under constant moderate or high ambient temperatures. The milk protein concentration decreased under high ambient temperature (P &lt; 0.01). The milk N secretion tended to decrease under high ambient temperature (P &lt; 0.10). Therefore, decreased N utilization for milk production at high ambient temperature is mainly caused by a reduced feed intake and the high ambient temperature itself.

Semen characteristics after overnight shipping: preservation of sperm concentrations, HspA2 ratios, CK activity, cytoplasmic retention, chromatin maturity, DNA integrity, and sperm shape.

We tested several approaches that can be used to preserve sperm attributes and the objective biochemical markers of sperm maturity and function for assessment in a remote centralized laboratory after overnight shipping of semen samples. Addition of phenyl-methyl-sulfonyl-fluoride (PMSF) to a final concentration of 20 microg/mL semen at 4 degrees C has preserved sperm concentrations and HspA2 isoform ratios, even at room temperature, simulating a shipping delay in moderate ambient temperatures. Regarding the attributes of individual spermatozoa, the patterns of CK-immunocytochemistry (demonstrates cytoplasmic retention in diminished-maturity spermatozoa); aniline blue staining pattern (tests chromatin maturity); sperm shape assessed by both Kruger strict morphology and computer assisted morphometry; and sperm DNA integrity, as tested by DNA nick translation, all remained unchanged. Thus, the PMSF-4 degrees C conditions preserved sperm concentrations and the cytoplasmic and nuclear biomarkers of sperm cellular maturity and function for next-day analysis. This shipping method will facilitate the early detection of subtle changes in semen quality that can affect sperm function, even when there has been no decline in sperm concentrations to signal possible toxic effects. Furthermore, sample preservation will enable investigators to evaluate semen for toxicology studies and for diagnosis of male infertility from remote locations. Home collection of semen should enhance study participation, and semen assessment in centralized laboratories will address concerns regarding interlaboratory variations and quality control.

The influence of upper-body pre-cooling on repeated sprint performance in moderate ambient temperatures

In this study, we examined the effects of upper-body pre-cooling before intermittent sprinting exercise in a moderate environment. Seven male and three female trained cyclists (age 26.8±5.5 years, body mass 68.5±9.5 kg, height 1.76±0.13 m, [Vdot]O2peak 59.0±11.4 mL · kg−1 · min−1; mean±s) performed 30 min of cycling at 50% [Vdot]O2peak interspersed with a 10-s Wingate cycling sprint test at 5 min intervals. The exercise was performed in a room controlled at 22oC and 40% relative humidity. In the control session, the participants rested for 30 min before exercise. In the pre-cooling session, the participants wore the upper segment of a liquid conditioning garment circulating 5oC coolant until rectal temperature decreased by 0.5oC. Rectal temperature at the start of exercise was significantly lower in the pre-cooling (36.5±0.3oC) than in the control condition (37.0±0.5oC), but this difference was reduced to a non-significant 0.4oC throughout exercise. Mean skin temperature was significantly lower in the pre-cooling (30.7±2.3oC) than in the control condition (32.5±1.6oC) throughout exercise. Heart rate during submaximal exercise was similar between the two conditions, although peak heart rate after the Wingate sprints was significantly lower in the pre-cooling condition. With pre-cooling, mean peak power (909±161 W) and mean overall power output (797±154 W) were similar to those in the control condition (peak 921±163 W, mean 806±156 W), with no differences in the subjective ratings of perceived exertion. These results suggest that upper-body pre-cooling does not provide any benefit to intermittent sprinting exercise in a moderate environment.

Effects of Peripheral Cooling on Substrate Selection During Exercise

0161 Purpose: To examine the effects of peripheral cooling via the rapid thermal exchange (RTX) cooling device (Avacore Technologies inc.) on whole body substrate oxidation during exercise at a moderate ambient temperature (28°C). Methods: Subjects (N = 16) completed two 45-minute cycle ergometer trials at 90% of ventilatory threshold (VT) with RTX peripheral cooling and without (CON). Rectal temperature was continuously recorded throughout both trials. VO2 and VCO2 were monitored to compute whole body substrate oxidation. significance was set at p < 0.05. Results: Despite no differences in rectal temperature between trials, mean CHO oxidation was lower during RTX (1453 ± 299 kJ) versus CON (1546 ± 291 kJ). Conversely, mean fat oxidation was higher during RTX (719 ± 248 kJ) versus CON (610 ± 197 kJ). HR and RPE were similar between trials. Conclusion: These data indicate the RTX device promotes a decrease in whole body carbohydrate (CHO) reliance despite no difference in rectal temperature. Supported by AVAcore Technologies, Inc

Effects of a whole-body spandex garment on rectal temperature and oxygen consumption in healthy dogs.

To determine whether a full-body spandex garment would alter rectal temperatures of healthy dogs at rest in cool and warm environments. Prospective study. 10 healthy dogs. Each dog was evaluated at a low (20 degrees to 25 degrees C [68 degrees to 77 degrees F]) or high (30 degrees to 35 degrees C [86 degrees to 95 degrees F]) ambient temperature while wearing or not wearing a commercially available whole-body spandex garment designed for dogs. Oxygen consumption was measured by placing dogs in a flow-through indirect calorimeter for 90 to 120 minutes. Rectal temperature was measured before dogs were placed in the calorimeter and after they were removed. Rectal temperature increased significantly more at the higher ambient temperature than at the lower temperature and when dogs were not wearing the garment than when they were wearing it. The specific rate of oxygen consumption was significantly higher at the lower ambient temperature than at the higher temperature. Results suggest that wearing a snug spandex body garment does not increase the possibility that dogs will overheat while in moderate ambient temperatures. Instead, wearing such a garment may enable dogs to better maintain body temperature during moderate heat loading. These results suggest that such garments might be used for purposes such as wound or suture protection without causing dogs to overheat.

Supercritical vaporization: distinguishable fluid regions.

The vaporization of a cold fluid pocket suddenly set into a hot, otherwise quiescent, atmosphere at supercritical pressures is analyzed. It is shown that at supercritical but moderate pressures and high ambient temperatures, the position where the thermal expansion coefficient reaches its maximum defines a relatively thin transition region that separates two distinguishable fluid regions: A cold liquidlike region where the heat transport is dominated by conduction, and a hot gaslike region where the heat transport is convective and conductive owed to the thermal expansion induced Stefan flow.