Effects of metabolic rate on thermal responses at different air velocities in -10 degrees C

The effects of exercise intensity on thermoregulatory responses in cold (-10 degrees C) in a 0.2 (still air, NoWi), 1.0 (Wi1), and 5.0 (Wi5) m x s(-1) wind were studied. Eight young and healthy men, preconditioned in thermoneutral (+20 degrees C) environment for 60 min, walked for 60 min on the treadmill at 2.8 km/h with different combinations of wind and exercise intensity. Exercise level was adjusted by changing the inclination of the treadmill between 0 degrees (lower exercise intensity, metabolic rate 124 W x m(-2), LE) and 6 degrees (higher exercise intensity, metabolic rate 195 W x m(-2), HE). Due to exercise increased heat production and circulatory adjustments, the rectal temperature (T(re)), mean skin temperature (Tsk) and mean body temperature (Tb) were significantly higher at the end of HE in comparison to LE in NoWi and Wi1, and T(re) and Tb also in Wi5. Tsk and Tb were significantly decreased by 5.0 m x s(-1) wind in comparison to NoWi and Wi1. The higher exercise intensity was intense enough to diminish peripheral vasoconstriction and consequently the finger skin temperature was significantly higher at the end of HE in comparison to LE in NoWi and Wi1. Mean heat flux from the skin was unaffected by the exercise intensity. At LE oxygen consumption (VO2) was significantly higher in Wi5 than NoWi and Wi1. Heart rate was unaffected by the wind speed. The results suggest that, with studied exercise intensities, produced without changes in walking speed, the metabolic rate is not so important that it should be taken into consideration in the calculation of wind chill index.     

Finger temperatures during military field training at 0 to −29 °C

1. Skin and rectal temperatures were recorded continuously in 70 measurements during typical tasks of infantry and artillery training at 0 to −29 °C. The duration of the measurements varied from 55 min to 9.5 h.

2. The distribution of finger skin temperatures was quite similar at ambient temperature ranges 0 to −10 °C and −10 to −20 °C, while at −20 to −30 °C the finger temperatures were clearly lower.

3. At different ambient temperature ranges, 20–69% of finger temperatures were low enough to cause cold thermal sensations.

4. Sensation of cold was experienced at a finger temperature of 11.6±3.7 °C (mean±SD).     

Thermal responses during and after whole-body cryotherapy (−110°C)

The effect of whole-body cryotherapy (WBC) on rectal and skin temperatures was measured in healthy subjects before, during and after WBC exposure. WBC did not cause any significant change in rectal temperature. The lowest local skin temperatures were recorded in the forearm, 5.2 (2.8)°C, and in the calf, 5.3 (3.0)°C. WBC involves no risk for frostbites. After WBC, all skin temperatures recovered rapidly, indicating that the analgetic effects of WBC only occur during a limited period after the exposure.     

Validation of an individualised model of human thermoregulation for predicting responses to cold air

Most computer models of human thermoregulation are population based. Here, we individualised the Fiala model [Fiala et al. (2001) Int J Biometeorol 45:143–159] with respect to anthropometrics, body fat, and metabolic rate. The predictions of the adapted multisegmental thermoregulatory model were compared with measured skin temperatures of individuals. Data from two experiments, in which reclining subjects were suddenly exposed to mild to moderate cold environmental conditions, were used to study the effect on dynamic skin temperature responses. Body fat was measured by the three-compartment method combining underwater weighing and deuterium dilution. Metabolic rate was determined by indirect calorimetry. In experiment 1, the bias (mean difference) between predicted and measured mean skin temperature decreased from 1.8°C to −0.15°C during cold exposure. The standard deviation of the mean difference remained of the same magnitude (from 0.7°C to 0.9°C). In experiment 2 the bias of the skin temperature changed from 2.0±1.09°C using the standard model to 1.3±0.93°C using individual characteristics in the model. The inclusion of individual characteristics thus improved the predictions for an individual and led to a significantly smaller systematic error. However, a large part of the discrepancies in individual response to cold remained unexplained. Possible further improvements to the model accomplished by inclusion of more subject characteristics (i.e. body fat distribution, body shape) and model refinements on the level of (skin) blood perfusion, and control functions, are discussed.     

Effect of nanoparticles of silver and gold on metabolic rate and development of broiler and layer embryos

This investigation evaluated the effects of nanoparticles of silver (AgNano) and gold (AuNano) on metabolic rate (O₂ consumption, CO₂ production and heat production-HP) and the development of embryos from different breeds of broiler and layer chicken. Gaseous exchange was measured in an open-air-circuit respiration unit, and HP was calculated for 10, 13, 16 and 19-day-old embryos. Relative chick and muscle weights were used as a measure of growth rate and development. AgNano but not AuNano increased the rates of O₂ consumption and HP of the layer embryos. The metabolic rate of broiler embryos was not affected by either of the treatments, but it was significantly higher compared to the layer embryos. Neither of the nanoparticles promoted nor depressed growth and development of the embryos, irrespective of breed. Although the metabolic rate of AgNano-injected layer embryos was significantly increased, their BW and muscle weights at hatching were similar to those of the control group, which suggests that the concentration of AgNano used was adequate for increasing the metabolic rate but not enough to affect growth and development. The results show that AgNano could be a potential metabolic modifier for layer embryos; however, the exact mechanism of action should be elucidated in future research.     

Mechanical properties of the human red blood cell membrane at −15 °C

The most common method for measuring the mechanical behavior of the human red blood cell (RBC) membrane is micropipette aspiration, because it can be used to apply both a low uniaxial stress at a small part of the membrane or high two-axial stresses to the whole membrane [E.A. Evans, R.E. Waugh, Mechano-chemical study of red cell membrane structure in situ, in: Kroc Foundation Series, vol. 13, Erythrocyte Mechanics and Blood Flow, Alan R. Liss. Inc., New York, 1980, pp. 31–56 (Chapter 3); H.J. Meiselman, Measures of blood rheology and erythrocyte mechanics, in: Kroc Foundation Series, vol. 13, Erythrocyte Mechanics and Blood Flow, Alan R. Liss. Inc., New York, 1980, pp. 75–117 (Chapter 5)]. The elastic shear moduli and area changes of the human RBC published to date were calculated by means of this technique. However, a main drawback of the method is its impracticability at subzero temperatures. Experiments at below 0 °C are of interest because it is at these temperatures that RBC lysis occurs during freezing and thawing after cryopreservation, via a mechanism that may be mechanical.A method for circumventing this limitation is deforming the cell membranes by applying an electric ac field to a supercooled suspension. In a previous study, we applied this technique to human RBCs down to −15 °C [M. Krueger, F. Thom, Deformability and stability of erythrocytes in high-frequency electric fields down to subzero temperatures, Biophys. J. 73 (1997) 2653–2666]. In this technique, the electrical dimensions must be translated into those of mechanics. We provided a formula for these calculations, which demonstrated excellent concordance with known mechanical measurements at room temperature [F. Thom, H. Gollek, Calculation of mechanical properties of human red cells based on electrically induced deformation experiments, J. Electrostat. 64 (2006) 53–61]. Using this formula, we have now calculated the shear moduli and stress–strain diagram for our deformation experiments at −15 °C and present the results below.     

Light-induced changes of fluorescence and absorbance in spinach chloroplasts at −40 °C

1. 1. Spinach chloroplasts were stored in the dark for at least 1 h, rapidly cooled to −40 °C, and illuminated with continuous light or short saturating flashes. In agreement with the measurements of Joliot and Joliot, chloroplasts that had been preilluminated with one or two flashes just before cooling showed a less efficient increase in the yield of chlorophyll a fluorescence upon illumination at −40 °C than dark-adapted chloroplasts. The effect disappeared below −150 °C, but reappeared again upon warming to −40 °C. Little effect was seen at room temperature in the presence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), added after the preillumination.

2. 2. Light-induced absorbance difference spectra at −40 °C in the region 500–560 nm indicated the participation of two components, the socalled 518-nm change (P518) and C-550. After preillumination with two flashes the absorbance change at 518 nm was smaller, and almost no C-550 was observed. After four flashes, the bands of C-550 were clearly visible again.

3. 3. The fluorescence increase and the absorbance change at 518 nm showed the same type of flash pattern with a minimum after the second and a maximum at the fourth flash. In the presence of 100 μM hydroxylamine, the fluorescence response was low after the fourth and high again after the sixth flash, which confirmed the hypothesis that the flash effect was related to the so-called S-state of the electron transport pathway from water to Photosystem 2.

4. 4. The kinetics of the light-induced absorbance changes were the same at each wavelength, and, apart from the size of the deflection, they were independent of preillumination. Flash experiments indicated that the absorbance changes were a one-quantum reaction. This was also true for the fluorescence increase in dark-adapted chloroplasts, but with preilluminated chloroplasts several flashes were needed to approximately saturate the fluorescence yield.

5. 5. The results are discussed in terms of a mechanism involving two electron donors and two electron acceptors for System 2 of photosynthesis.

Comparison in men of physiological responses to exercise of increasing intensity at low and moderate ambient temperatures

In six male subjects the sweating thresholds, heart rate (fc), as well as the metabolic responses to exercise of different intensities [40%, 60% and 80% maximal oxygen uptake (VO2max)], were compared at ambient temperatures (Ta) of 5 degrees C (LT) and 24 degrees C (MT). Each period of exercise was preceded by a rest period at the same temperature. In LT experiments, the subjects rested until shivering occurred and in MT experiments the rest period was made to be of exactly equivalent length. Oxygen uptake (VO2) at the end of each rest period was higher in LT than MT (P less than 0.05). During 20-min exercise at 40% VO2max performed in the cold no sweating was recorded, while at higher exercise intensities sweating occurred at similar rectal temperatures (Tre) but at lower mean skin (Tsk) and mean body temperatures (Tb) in LT than MT experiments (P less than 0.001). The exercise induced VO2 increase was greater only at the end of the light (40% VO2max) exercise in the cold in comparison with MT (P less than 0.001). Both fc and blood lactate concentration [1a]b were lower at the end of LT than MT for moderate (60% VO2max) and heavy (80% VO2max) exercises. It was concluded that the sweating threshold during exercise in the cold environment had shifted towards lower Tb and Tsk. It was also found that subjects exposed to cold possessed a potentially greater ability to exercise at moderate and high intensities than those at 24 degrees C since the increases in Tre, fc and [1a]b were lower at the lower Ta.     

Effect of dietary supplementation of l-tryptophan on thermal tolerance and oxygen consumption rate in Cirrhinus mrigala fingerlings under varied stocking density

A 60 day feeding trial was conducted to study the effect of dietary l-tryptophan on thermal tolerance and oxygen consumption rate of freshwater fish, mrigala, Cirrhinus mrigala reared under ambient temperature at low and high stocking density. Four hundred eighty fingerlings were distributed into eight experimental groups. Four groups each of low density group (10 fishes/75 L water) and higher density group (30 fishes/75 L water) were fed a diet containing 0, 0.68, 1.36 or 2.72% l-tryptophan in the diet, thus forming eight experimental groups namely, Low density control (LC) (basal feed +0% l-tryptophan); LT₁ (basal feed+0.68% l-tryptophan); LT₂ (basal feed+1.36% l-tryptophan); LT₃ (basal feed+2.72% l-tryptophan); high density control (HC) (basal feed+0% l-tryptophan); HT₁ (basal feed+0.68% l-tryptophan); HT₂ (basal feed+1.36% l-tryptophan); and HT₃ (basal feed+2.72% l-tryptophan) were fed at 3% of the body weight. The test diets having crude protein 34.33±0.23 to 35.81±0.18% and lipid 423.49±1.76 to 425.85±0.31 K Cal/100 g were prepared using purified ingredients. The possible role of dietary l-tryptophan on thermal tolerance and oxygen consumption rate was assessed in terms of critical thermal maxima (CT_Max), critical thermal minima (CT_Min), lethal thermal maxima (LT_Max) and lethal thermal minima (LT_Min). The CT_Max, CT_Min, LT_Max and LT_Min values were found to be significantly higher (p<0.05) in the treatment groups with CT_Max 42.94±0.037 (LT₂); LT _Max 43.18±0.070 (LT₂); CT_Min 10.47±0.088 (LT₂) and LT_Min 9.42±0.062 (LT₃), whereas the control group showed a lower tolerance level. The same trend was observed in the high density group (CT_Max 42.09±0.066 (LT₃); LT_Max 4₃ 23±0.067 (HT₃); CT_Min 10.98±0.040 (HT₃) and LT_Min 9.74±0.037 (HT₃). However, gradual supplementation of dietary l-tryptophan in the diet significantly reduced the oxygen consumption rate in both the low density group (Y=−26.74x+222.4, r²=0.915) and the high density group (Y=−32.96x+296.5, r²=0.8923). Dietary supplementation of l-tryptophan at a level of 1.36% improved the thermal tolerance level and reduced the oxygen consumption rate in C. mrigala fingerlings.     

Fundamentals and Challenges of Lithium Ion Batteries at Temperatures between −40 and 60 °C

Lithium ion batteries (LIBs) continuously prove themselves to be the main power source in consumer electronics and electric vehicles. To ensure environmental sustainability, LIBs must be capable of performing well at extreme temperatures, that is, between ?40 and 60 °C. In this review, the recent important progress and advances in the subzero and elevated temperature operations of LIBs is comprehensively summarized from a materials perspective. In the scenario of subzero temperatures, limitations, electrolytes, anodes, and solid electrolyte interphase (SEI); cathodes and cathode electrolyte interphase (CEI); and binders are thoroughly discussed to explore the fundamentals and basics that underlie the decay in electrochemical performance and how the chemistry, physics, and electrochemistry are correlated with the materials and components that interact with each other. In the case of high temperatures limitations, the thermal stability of the key materials and components are reviewed, and then the reaction thermodynamics and kinetics of the anodes, cathodes, electrolytes, and their interactions are described using the highest occupied molecular orbit (HOMO)/lowest unoccupied molecular orbit (LUMO), and are extensively discussed. The prospect of combining the extreme temperature poles in a single cell by introducing appropriate electrolytes and additives is discussed.     

Effects of wearing two different types of clothing on body temperatures during and after exercise

The experiment was conducted to investigate the human thermoregulatory responses during rest, exercise and recovery atT _a 20°C and 60% R.H. under the conditions of wearing two different types of clothing. Six healthy men wore two types of clothing: one covering the whole body area except the head (Type A, weight 1656 g), and the other covering only the trunk, upper arms and thighs (Type B, weight 996 g). The level of rectal temperature was kept significantly higher in Type B than in Type A during rest and recovery. The increased and decreased rates of rectal temperature during exercise and recovery were significantly greater in Type A than in Type B, respectively. These findings are discussed from the viewpoint of the differences of skin temperatures of the extremities between Type A and Type B.     

Effects of body lipid content on the resting metabolic rate and postprandial metabolic response in the southern catfish Silurus meridionalis

We assessed the effects of body lipid content on the resting metabolic rate and specific dynamic action (SDA) of the southern catfish Silurus meridionalis. Obese and lean fish were obtained by feeding the fish with two different feeds at 27.5 °C for 4 weeks prior to the experiment. The fish were fed with experimental diets with a meal size of 4% by body mass. A continuous-flow respirometer was used to determine the oxygen consumption rate at 2-h intervals until the postprandial oxygen consumption rate had returned to the preprandial level. The body lipid content of the obese fish was significantly greater than that of the lean fish. The metabolic parameters evaluated (resting metabolic rate, peak metabolic rate (R_peak), factorial ratio, time to peak, duration, energy expended on SDA (SDA_E), or SDA coefficient) were not significantly affected by body fat content in terms of the whole-body or mass-specific values. Increased body fat content did not decrease the resting metabolic rate in the southern catfish, which might be due to the higher levels of highly unsaturated fatty acids in these fish. The results also suggest that the body composition does not appear to affect the SDA response.     

不同流速下红鳍银鲫趋流行为与耗氧率的变化

在28℃水温下,使用特制的鱼类游泳行为和活动代谢同步测定装置对红鳍银鲫(Barbodes schwanenfeldi)幼鱼在0 m/s、0.1 m/s、0.3 m/s、0.5 m/s 4种流速条件下的趋流行为和耗氧率进行了同步测定和统计分析.结果表明: 红鳍银鲫在静水下的游泳活动表现出随机而无特定的方向性,当流速达到0.3 m/s以上时则呈现很强的趋流性.和静水对照组相比,三个流速实验组在各个时间段的趋流率、摆尾频率和耗氧率均显著上升,其中多数时间段以0.3 m/s流速组最大,0.5 m/s流速组次之.低流速组(0,0.1 m/s)三个指标在90 min内随时间变化不显著,而高流速组(0.3,0.5 m/s)随时间变化明显.红鳍银鲫在90 min各个时间段摆尾频率(Tail beat frequency)与趋流率(Rheotaxis frequency)均呈显著的线性相关,其回归关系式为:RF=a bTBF,a值在41.13-55.02、b值在8.0 7-11.42、R在0.69-0.95之间;摆尾频率和耗氧率(Oxygen consumption rate)同样呈 显著的线性相关,其回归关系式为:OCR=a bTBF,a值在77.38-137.42, b值在10.85-59.36,R在0.87-0.96之间.0.3 m/s流速下红鳍银鲫趋流率、摆尾频率和耗氧率24 h的变化规律为:实验开始时三个指标均随时间延长而逐渐增大,在3 h达到最大值,然后开始下降并长时间维持在一定水平上,其中耗氧率在最初3 h的增幅显著大于趋流率和摆尾频率,而随后回落的幅度却小于前两者.在较高流速下,红鳍银鲫幼鱼不能长期保持趋流状态和维持较高的代谢水平     

The effect of cryopreservation at −196°C on the viability of fowl and Turkey spermatozoa assessed in vitro

The effect of storing fowl and turkey spermatozoa at −196°C in a glycerol-based diluent on post-thawing levels of motility, ATP content, morphology and leakage of lactate dehydrogenase was investigated. Compared to those of freshly-diluted spermatozoa, these parameters were reduced to 24, 26, 55 and 61% respectively, for fowl spermatozoa and to 22, 26, 34 and 60%, respectively, for turkey spermatozoa, immediately after thawing and the removal of glycerol. On subsequent incubation for 3 h at 40°C, the ATP content and morphological integrity of frozen/thawed spermatozoa of both species fell to less than 5% of the levels of similarly-incubated non-frozen spermatozoa. Only after prolonged incubation of fowl and turkey spermatozoa could these parameters be shown to reflect, and, therefore, be of use as monitors of the reduction of fertilizing ability caused by freezing.     

The effect of muscularity on thermal responses,muscle performance,and dexterity during whole body exposure to 10 °C

1.

The study evaluated the effects of exposure to cold air (10 °C) on thermal responses, muscle performance and dexterity of muscular subjects and their matched lean counterparts.     

The influence of cold stress and a 36- h fast on the physiological responses to prolonged intermittent walking in man

In a previous study, rectal temperature (T _re) was found to be lower, and oxygen consumption (V˙O₂) and the respiratory exchange ratio (R) were higher in a cold (+5°C), wet and windy environment (COLD), compared with a thermoneutral environment during intermittent walking at ≈30% of peak V˙O₂ (Weller AS, Millard CE, Stroud MA et al. Am J Physiol 272:R226–R233, 1997). The aim of the present study was to establish whether these cold-induced responses are influenced by prior fasting, as impaired thermoregulation has been demonstrated in cold-exposed, resting men following a 48-h fast. To address this question, eight men attempted a 360-min intermittent (15 min rest, 45 min exercise) walking protocol under COLD conditions on two occasions. In one condition, the subjects started the exercise protocol ≈120 min after a standard meal (FED/COLD), whereas in the other the subjects had fasted for 36 h (FASTED/COLD). The first two exercise periods were conducted at a higher intensity (HIGHER, 6 km · h⁻¹ and 10% incline), than the four subsequent exercise periods (LOW, 5 km · h⁻¹ and 0% incline). There was no difference in the time endured in FED/COLD and FASTED/COLD. In FASTED/COLD com pared with FED/COLD, R was lower during HIGHER and LOW, and T _re was lower during LOW, whereas there was no difference in V˙O₂, mean skin temperature and heart rate. Therefore, although the 36-h fast impaired temperature regulation during intermittent low-intensity exercise in the cold, wet and windy environment, it was unlikely to have been the principal factor limiting exercise performance under these experimental conditions. Accepted: 26 August 1997     

The effects of acclimation on thermal tolerance, desiccation resistance and metabolic rate in Chirodica chalcoptera (Coleoptera: Chrysomelidae)

Despite much focus on species responses to environmental variation through space and time, many higher taxa and geographic areas remain poorly studied. We report the effects of temperature acclimation on thermal tolerance, desiccation rate and metabolic rate for adult Chirodica chalcoptera (Coleoptera: Chrysomelidae) collected from Protea nerifolia inflorescences in the Fynbos Biome in South Africa. After 7 days of acclimation at 12, 19 and 25 degrees C, critical thermal maxima (mean+/-s.e.: 41.8+/-0.2 degrees C in field-fresh beetles) showed less response (<1 degrees C change) to temperature acclimation than did the onset of the critical thermal minima (0.1+/-0.2, 1.0+/-0.2 and 2.3+/-0.2 degrees C, respectively). Freezing was lethal in C. chalcoptera (field-fresh SCP -14.6 degrees C) and these beetles also showed pre-freeze mortality. Survival of 2 h at -10.1 degrees C increased from 20% to 76% after a 2 h pre-exposure to -2 degrees C, indicating rapid cold hardening. Metabolic rate, measured at 25 degrees C and adjusted by ANCOVA for mass variation, did not differ between males and females (2.772+/-0.471 and 2.517+/-0.560 ml CO2 h(-1), respectively), but was higher in 25 degrees C-acclimated beetles relative to the field-fresh and 12 degrees C-acclimated beetles. Body water content and desiccation rate did not differ between males and females and did not respond significantly to acclimation. We place these data in the context of measured inflorescence and ambient temperatures, and predict that climate change for the region could have effects on this species, in turn possibly affecting local ecosystem functioning.