Effects of cold stress and exercise on fat loss in females

A Latin Square design has been used to test the responses of 24 relatively fit young women to 200 minute bouts of exercise performed over 5 day trials under each of three different ambient conditions: 15 degrees C (warm-warm; (WW)); -20 degrees C while inhaling, from a facemask, air heated to 18 degrees C (cold-warm; (CW)); and -20 degrees C (cold-cold; (CC)). In both of the cold environments, special clothing and boots were provided (insulation 0.47 degree C X watt-1 X m-2 and 0.62 degree C X watt-1 X m-2; (4 and 3 CLO units)). All three trials led to a small (0.6-0.7 degree C) rise of rectal temperature, but in the two cold environments mean body temperatures fell by over 1.0 degree C. A large increase of serum ketones occurred under all conditions, and the exercise respiratory quotient suggested some increase of fat utilization, WW (0.85) through CW (0.84) to CC (0.83). A fat loss of about 0.5 kg over the five days was confirmed by hydrostatic weighing and measurement of skinfold thicknesses. This was much less than the change previously observed in men, and moreover, it seemed to be independent of ambient conditions. Possible reasons why cold did not increase fat loss in these women include: a lower relative intensity of exercise; a greater stability of fat stores in women; avoidance of caffeine; a possible translocation of subcutaneous fat to deep fat depots; and a greater desire to "lose weight" irrespective of environmental conditions.     

Thermoregulatory and subjective responses of clothed men in the cold during continuous and intermittent exercise

Thermoregulatory and thermal subjective responses were studied in ten male, clothed subjects during continuous (C) and intermittent (I) exercise at the same average level of oxygen consumption. The subjects performed both I and C twice, dressed in two different three-layer cold-protective clothing ensembles of two thermal insulation levels [total clothing insulation = 2.59 clo (L) and 3.20 clo (H)]. Experiments were carried out at an ambient temperature of -10 degrees C. Rectal temperatures increased similarly in both types of exercise. Mean skin temperature (Tsk) was lower in I compared to C with both levels of clothing insulation. Over the last 0.5 h of the experiment Tsk was approximately 1.3 degrees C lower in I than in C for clothing L. The skin evaporation rate was higher in clothing H than L but did not differ between I and C. Subjective ratings for thermal sensations of the whole body (BTS) and hands were close to neutral in I and around slightly warm in C. The BTS was lower in I than in C and was lower in L compared to H. It was concluded that, at equal average energy expenditure, thermal responses to intermittent and continuous exercise in the cold differ in clothed subjects, principally as a result of different patterns of heat exchange.     

Thermoregulatory responses to intermittent exercise are influenced by knit structure of underwear

The purpose of this study was to evaluate the role of knit structure in underwear on thermoregulatory responses. Underwear manufactured from 100% polypropylene fibres in five different knit structures (1-by-1 rib, fleece, fishnet, interlock, double-layer rib) was evaluated. All five underwear prototypes were tested as part of a prototype clothing system. Measured on a thermal manikin these clothing systems had total thermal resistances of 0.243, 0.268, 0.256, 0.248 and 0.250 m2.K.W-1, respectively (including a value for the thermal resistance of the ambient environment of 0.104 m2.K.W-1). Human testing was done on eight male subjects and took place at ambient temperature (Ta) = 5 degrees C, dew point temperature (Tdp) = -3.5 degrees C and air velocity (Va) = 0.32 m.s-1. The test comprised a repeated bout of 40-min cycle exercise (315 W.m-2; 52%, SD 4.9% maximal oxygen uptake) followed by 20 min of rest (62 W.m-2). The oxygen uptake, heart rate, oesophageal temperature, skin temperature, Ta, Tdp at the skin and in the ambient air, onset of sweating, evaporation rate, non-evaporated sweat accumulated in the clothing and total evaporative loss of mass were measured. Skin wettedness was calculated. The differences in knit structure of the underwear in the clothing systems resulted in significant differences in mean skin temperature, local and average skin wettedness, non-evaporated and evaporated sweat during the course of the intermittent exercise test. No differences were observed over this period in the core temperature measurements.     

嗜卷书虱实验种群生命表的研究

在不同温度和湿度条件下对嗜卷书虱进行饲养,分别组建春实验种群特定年龄和特定时间生命表,并应用Morris模式及SWeibull频数分布以探讨温、湿度与嗜卷书虱种群数量变动的关系。结果表明,温、湿度对存活率的作用是影响该实验种群趋势指数（I）值最重要的因子,在适宜温、湿度条件下,种群存活曲线属DeeveyⅠ型,而在不太适宜条件下则属DeeveyⅢ型,理论上30.63℃时周限增长率（λ）最大,达1.0628倍／天,该虫发育和繁殖的最适温区为28-30℃,最适相对湿度在80％左右。     

Thermoregulatory and nonthermoregulatory heat production in burned rat

Severely burned patients are hypermetabolic within their thermoneutral zone (TNZ), where there are no thermoregulatory demands on heat production. The rat has been used as a model of postburn hypermetabolism without clear evidence that it behaves in a similar way. Male rats (400-500 g; n = 34-39) were placed as a group in a respiration chamber and metabolic rates for the average rat were determined over 3-6 h at ambient temperatures between 9 and 36 degrees C. Colonic temperatures (Tco) and body weights were measured after each run. Animals were studied sequentially as normals (N), after clipping (C) and following 50% total body surface scald burns. Clipping increased the lower critical temperature (LCT) from 27.7 to 29.1 degrees C without affecting resting heat production (N = 42.6 +/- 0.5; C = 42.0 +/- 0.8 W/m2; mean +/- S.E.) or Tco (N = 36.6 +/- 0.1; C = 36.6 +/- 0.1 degrees C) in the TNZ. Injury increased LCT to 32.8 degrees C and the burned animals were hypermetabolic (47.2 +/- 0.6 W/m2; P less than 0.05 vs. N) and febrile (36.9 +/- 0.1 degrees C; P less than 0.05 vs. N) in the elevated TNZ. These metabolic and temperature responses of burned rats are limited in magnitude but are qualitatively similar to those of patients. The extra heat production in the TNZ reflects the basic metabolic cost of injury.     

Development, survivorship, and reproduction of Helicoverpa armigera (Lepidoptera: Noctuidae) under constant and alternating temperatures

Laboratory studies were conducted to assess the effect of temperature on the survival, development, fecundity, and longevity of Helicoverpa armigera (Hübner) at 11 constant temperatures ranging from 12.5 to 40 degrees C, as well as at five alternating temperature regimes (25-10, 30-15, 32.5-17.5, 35-20, and 35-27.5 degrees C) and under a photoperiod of 16:8 (L:D) h. H. armigera reared at constant temperatures did not develop from egg to adult (emergence) outside the temperature range of 17.5-32.5 degrees C. The alternating conditions expanded this range from 10 to 35 degrees C. The lowest developmental thresholds of the immature stages were estimated by a linear model and ranged from 10.17 (pupal stage) to 11.95 degrees C (egg stage) at constant temperature regimes and from 1.1 to 5.5 degrees C, respectively at alternating temperatures. The values of developmental thresholds estimated using the nonlinear (Lactin-2) model were lower than those estimated by the linear model for constant and alternating temperature regimes except for larval and pupal stages at constant temperatures. Mean adult longevity fluctuated from 34.4 d at 15 degrees C to 7.6 d at 35 degrees C. Females reared under all alternating temperature regimes laid more eggs than females reared at any, except the 25 degrees C, constant temperature treatment. The intrinsic rate of increase was highest at 27.5 degrees C, at both the constant and the corresponding alternating temperature regimes (0.147 and 0.139, respectively). Extreme temperatures had a negative effect on life table parameters.     

Noninvasive measurement of temperature and fractional dissociation of imidazole in human lower leg muscles using 1H-nuclear magnetic resonance spectroscopy.

The temperature change of the fractional dissociation of imidazole (alpha-imidazole) in resting human lower leg muscles was measured noninvasively using (1)H-nuclear magnetic resonance spectroscopy at 3.0 and 1.5 T on five normal male volunteers aged 30.6 +/- 10.4 yr (mean +/- SD). Using (1)H-nuclear magnetic resonance spectroscopy, water, carnosine, and creatine in the muscles could be simultaneously analyzed. Carnosine contains imidazole protons. The chemical shifts of water and carnosine imidazole protons relative to creatine could be used for estimating temperatures and alpha-imidazole, respectively. Using the chemical shift, the values of temperature in gastrocnemius (Gast) and soleus muscles at ambient temperature (21-25 degrees C) were estimated to be 35.5 +/- 0.5 and 37.4 +/- 0.6 degrees C (means +/- SE), respectively (significantly different; P < 0.01). The estimated values of alpha-imidazole in these muscles were 0.620 +/- 0.007 and 0.630 +/- 0.013 (means +/- SE), respectively (not significant). Alternation of the surface temperature of the lower leg from 40 to 10 degrees C significantly changed the temperature in Gast (P < 0.0001) from 38.1 +/- 0.5 to 28.0 +/- 1.2 degrees C, and the alpha-imidazole in Gast decreased from 0.631 +/- 0.003 to 0.580 +/- 0.011 (P < 0.05). However, the values of alpha-imidazole and the temperature in soleus muscles were not significantly affected by this maneuver. These results indicate that the alpha-imidazole in Gast changed significantly with alternation in muscle temperature (r = 0.877, P < 0.00001), and its change was estimated to be 0.0058/ degrees C.     

The effects of fabric air permeability and moisture absorption on clothing microclimate and subjective sensation in sedentary women at cyclic changes of ambient temperatures from 27 degrees C to 33 degrees C

The present paper aimed at learning the effects of two different levels of air permeability and moisture absorption on clothing microclimate and subjective sensation in sedentary women. Three kinds of clothing ensemble were investigated: 1) polyester clothing with low moisture absorption and low air permeability (A clothing); 2) polyester clothing with low moisture absorption and high air permeability (B clothing); and 3) cotton clothing with high moisture absorption and high air permeability (C clothing). After 20 min of dressing time, the room temperature and humidity began to rise from 27 degrees C and 50% rh to 33 degrees C and 70% rh over 20 min, and it was maintained for 30 min (Section I); it then began to fall to 27 degrees C and 50% rh over 20 min, and it was maintained there for 20 min (Section II). The subject sat quietly on a chair for 110 min. The main findings are summarized as follows: 1) The clothing surface temperature was significantly higher in C clothing than in B clothing during section I, but it was significantly higher in B clothing than in C clothing during section II. 2) Although the positive relationship between the microclimate humidity and forearm sweat rate was significantly confirmed in all three kinds of clothing, the microclimate humidity at the chest for the same sweat rate was lower in C clothing than in A and B clothing. These results were discussed in terms of thermal physiology.     

温度对谷胱甘肽分批发酵的影响及动力学模型

研究了24～32℃范围内产朊假丝酵母生产谷胱甘肽的分批发酵过程,发现较高温度对细胞生长有促进作用,而较低温度则更有利于谷胱甘肽产量的提高。应用改进的Logistic和LuedekingPiret方程分别对细胞生长动力学和谷胱甘肽合成动力学进行了模拟,得到不同温度下各种动力学参数。在此基础上,进一步研究了温度同细胞生长动力学参数之间的内在联系,得到谷胱甘肽分批发酵过程中细胞浓度的变化同温度以及底物浓度之间的一般关系式：dX-dt＝［0.0224(T+1.7)］2X(1-X/X_max)1+S｛8.26×10.6×exp［-31477/R/(T+273)］｝。验证实验结果表明,该模型具有很好的适用性。     

Experimental epizootiology of Zoophthora anhuiensis (Entomophthorales) against Myzus persicae (Homoptera: Aphididae) with a description of a modified Gompertz model for aphid epizootics

Epizootiological features of Zoophthora anhuiensis, a fungal pathogen specific to aphids in southern China, were studied in six aptera colonies of Myzus persicae at 16 regimes of temperature (T = 10, 15, 20 and 25 degrees C) and relative humidity (H = 90%, 95%, 98% and 100% RH) with initially infected proportion (Ip) of 0.5 in experiment (Expt) 1 or at a fixed regime of 15 degrees C and 100% RH with a variable Ip of 0.17-1.00 in Expt 2. Mycosis-caused mortalities (Mp) varied with aphid densities (D) over time after colony initiation (t) were well fitted to a Gompertz growth model modified to include the variables T, H, Ip and D in the form of Mp = 91.72exp[-5.282exp[-(0.0095T + 0.0128H/T-0.5407D2/H)t]] for Expt 1 (r2 = 0.94) or Mp = 95.49exp[-4.314exp[-(0.1479Ip + 0.1636/D)t]] for Expt 2 (r2 = 0.97). These variables were effective in determining the rate of epizootic development in the M. persicae colonies. Based on the observed and fitted results, Z. anhuiensis was most adaptive to cool climate or season and epizootiologically was subject to a minimal effect of RH at an optimum of approximately 15 degrees C. However, the humidity became determinant for epizootic progress at higher temperatures. Interactive effects of the variables and application of the fitted models for predicting epizootic development in field situations are discussed.     

Partial-body exposure of human volunteers to 2450 MHz pulsed or CW fields provokes similar thermoregulatory responses

Many reports describe data showing that continuous wave (CW) and pulsed (PW) radiofrequency (RF) fields, at the same frequency and average power density (PD), yield similar response changes in the exposed organism. During whole-body exposure of squirrel monkeys at 2450 MHz CW and PW fields, heat production and heat loss responses were nearly identical. To explore this question in humans, we exposed two different groups of volunteers to 2450 MHz CW (two females, five males) and PW (65 micros pulse width, 10(4) pps; three females, three males) RF fields. We measured thermophysiological responses of heat production and heat loss (esophageal and six skin temperatures, metabolic heat production, local skin blood flow, and local sweat rate) under a standardized protocol (30 min baseline, 45 min RF or sham exposure, 10 min baseline), conducted in three ambient temperatures (T(a) = 24, 28, and 31 degrees C). At each T(a), average PDs studied were 0, 27, and 35 mW/cm2 (Specific absorption rate (SAR) = 0, 5.94, and 7.7 W/kg). Mean data for each group showed minimal changes in core temperature and metabolic heat production for all test conditions and no reliable differences between CW and PW exposure. Local skin temperatures showed similar trends for CW and PW exposure that were PD-dependent; only the skin temperature of the upper back (facing the antenna) showed a reliably greater increase (P =.005) during PW exposure than during CW exposure. Local sweat rate and skin blood flow were both T(a)- and PD-dependent and showed greater variability than other measures between CW and PW exposures; this variability was attributable primarily to the characteristics of the two subject groups. With one noted exception, no clear evidence for a differential response to CW and PW fields was found.     

Size frequency distribution and growth of the crabs Callinectes arcuatus and C. bellicosus (Decapoda: Portunidae) in Las Guásimas coastal lagoon, Mexico

Information on size frequency distribution, the width-weight relation and growth parameters of the crabs Callinectes arcuatus and C. bellicosus is presented. The data comes from samples taken with a trawl net both day and night on a monthly basis from March 1998 to February 2000 in a coastal lagoon from Gulf of California. C. bellicosus (n=878) was more abundant than C. arcuatus (n=357) and its size frequency distribution presented carapace width CW ranges of 8.4-166 mm and 9-130 mm respectively. Both populations were mainly represented by juveniles (75 mm in CW) ranging from 37 to 75 mm in CW, and adults (>75 mm in CW) between 76 and 90 mm in CW. In both species the width-weight relation showed that males grow more than females, with an isometric growth tendency being observed. The growth parameters for C. arcuatus estimated using the von Bertalanffy Model, were: K = 0.84 year(-1), L infinity = 140 mm to = -0.12 for C. arcuatus, and K= 0.9 year(-1), L infinity = 169 mm to = -0.11 for C. bellicosus. These results showed that the relative age at which maximum growth is attained is between three and four years for both species.     

Mean skin temperature in warm humid climates

Mean skin temperature (Tsk) was measured in 24 subjects during experiments in a climatic chamber. Three conditions of ambient temperature (Ta = 25.6 degrees, 28.9 degrees and 32.2 degrees C), and three of humidity (relative humidity = 50%, 70% and 90%) were studied. A relationship was established by a linear regression technique. It is valid in the 24 degree-34 degree C range, for air velocity = 0.2 m.s-1, clothing insulation = 0.077 degrees C.m2.w-1 (0.5 clo), metabolic rate = 64 w.m-2 (1.1 met) and radiant temperature = air temperature. In these conditions Tsk = 28.125 + 0.021 Pw + 0.210 Ta (Pw: ambient water vapour pressure in mb). It shows a small humidity influence. The influences of sex, transition from one condition to the next, and air velocity were also studied. Measurements in Africa confirmed the small influence of humidity. Ethnic life-style differences indicated that a high precision in Tsk determination is difficult to achieve.     

Ventilatory effect of acute pulmonary hypothermia

The isolated effect of cooling the pulmonary circulation on ventilation was quantified in nine anesthetized dogs. The right pulmonary artery (RPA) was cannulated within the pericardium, and systemic blood was pumped from the left atrium to the RPA between, but not during, periods of cooling. Cooled blood boluses were injected into the RPA under conditions in which either bolus temperature (5-35 degrees C) or volume (0-1.5 ml/kg body wt) varied. Inspiratory time (TI), expiratory time (TE), breath duration (TT), and peak integrated activity (PEAK) were determined from diaphragm EMG. Results for five postinjection breaths were converted to a percent of the values from five preinjection breaths. There was a linear relationship between bolus temperature and TI [r = 0.61, slope (x) = 0.59%/degrees C, P less than 0.001), TE (r = 0.73, x = 1.43%/degrees C, P less than 0.001] as well as TT (r = 0.74, x = 1.10%/degrees C, P less than 0.001), whereas PEAK was unaffected (n = 9). When injection temperature was 5 degrees C, an inverse linear relationship existed between bolus volume and TI (r = 0.75, x = -15.2%.ml-1.kg-1, P less than 0.001) and TE (r = 0.78, x = -23.4%.ml-1.kg-1, P less than 0.001) (n = 4). In two dogs tested the effect of bolus injection was minimal at residual volume and progressively increased with lung volume. The effect of cold bolus injection was eliminated after right vagotomy in three dogs. Results indicate that cooling of some vagal receptor in the lung increases breathing frequency primarily by shortening TE.     

Measurement of torso skin temperature under clothing

The influence of clothing on skin temperature distributions of the torso was investigated during and after cold exposure. Volunteers were cooled for one hour at 5 degrees C while wearing clothing designed to have insulation which was intended to be relatively uniformly distributed. Three different thicknesses of clothing were used. Following thermistor measurements of skin temperatures during the cold exposures, clothing was quickly removed from the upper parts of the body to enable thermographic investigations of the temperature distributions of the front of the bare torso. The evolution of temperature distributions were then studied at different ambient temperatures (5 degrees C and 20 degrees C) as a function of the thickness of the insulation which had previously been worn. The patterns of the temperature distributions, and the range and standard deviation of torso temperatures were all found to be relatively constant in spite of the different thicknesses of clothing worn or in the time-variant mean torso temperatures which resulted. The front torso sites normally used for the determination of mean skin temperatures were found to be on portions of the torso which were cooler than the surrounding regions. It was concluded that a site midway between the umbilicus and a nipple yields a more accurate estimate of mean torso temperature in the conditions of the present study.     

Ontogeny of homeothermy in the immature rat: metabolic and thermal responses

Steady-state thermoregulatory responses were measured in the immature rat at 5, 7, 9, 11, 13, 15, 17, and 19 days of age. Tests were conducted at controlled ambient temperatures (Ta) ranging from 22.5 to 37.0 degrees C. Colonic (Tco) and skin (tail, interscapular, abdominal) temperatures were measured, as was O2 consumption from which metabolic rate (M) was calculated. Significant improvements in homeothermic ability occurred from 5 to 19 days of age. Although the resting level of M (RMR) increased by 6.9 W/m2 and the lower Ta limit for RMR (LCT) decreased by 2.5 degrees C as age advanced from 5 to 19 days, Tco at LCT was 36.8-37.1 degrees C at all ages studied. Below LCT the elevation of M to a given decrease in Tco was greater the older the animal. A comparable response to a change in skin temperature was not age dependent. Improvement in thermal insulation was the primary factor responsible for increases in homeothermic ability between 5 and 19 days of age.     

温度对椰心叶甲实验种群生长的影响

在不同温度(16、20、2、28和32 ℃)条件下观察椰心叶甲的发育、存活及繁殖情况.结果表明,椰心叶甲在32 ℃恒温下不能存活,在16～28 ℃世代发育起点温度为11.08 ℃,有效积温为966.22日·度,在海南省儋州市1年可发生4～5代.椰心叶甲世代存活率在28 ℃时最高,达92.5%.净增殖率、内禀增长率及周限增长率均在28 ℃时最高,分别为54.1、0.0260和1.0263.平均世代历期和种群加倍时间分别以20 ℃和28 ℃时最短,前者为123.1 d,后者为26.7 d.种群趋势指数以28 ℃时最高,为50.8,表明24～28 ℃为椰心叶甲种群生长的适合温度.     

Hypercapnia increases core temperature cooling rate during snow burial.

Previous retrospective studies report a core body temperature cooling rate of 3 degrees C/h during avalanche burial. Hypercapnia occurs during avalanche burial secondary to rebreathing expired air, and the effect of hypercapnia on hypothermia during avalanche burial is unknown. The objective of this study was to determine the core temperature cooling rate during snow burial under normocapnic and hypercapnic conditions. We measured rectal core body temperature (T(re)) in 12 subjects buried in compacted snow dressed in a lightweight clothing insulation system during two different study burials. In one burial, subjects breathed with a device (AvaLung 2, Black Diamond Equipment) that resulted in hypercapnia over 30-60 min. In a control burial, subjects were buried under identical conditions with a modified breathing device that maintained normocapnia. Mean snow temperature was -2.5 +/- 2.0 degrees C. Burial time was 49 +/- 14 min in the hypercapnic study and 60 min in the normocapnic study (P = 0.02). Rate of decrease in T(re) was greater with hypercapnia (1.2 degrees C/h by multiple regression analysis, 95% confidence limits of 1.1-1.3 degrees C/h) than with normocapnia (0.7 degrees C/h, 95% confidence limit of 0.6-0.8 degrees C/h). In the hypercapnic study, the fraction of inspired carbon dioxide increased from 1.4 +/- 1.0 to 7.0 +/- 1.4%, minute ventilation increased from 15 +/- 7 to 40 +/- 12 l/min, and oxygen saturation decreased from 97 +/- 1 to 90 +/- 6% (P < 0.01). During the normocapnic study, these parameters remained unchanged. In this study, T(re) cooling rate during snow burial was less than previously reported and was increased by hypercapnia. This may have important implications for prehospital treatment of avalanche burial victims.     

Delignification kinetics of corn stover in lime pretreatment

Corn stover was pretreated with excess calcium hydroxide (0.5 g Ca(OH)(2)/g raw biomass) in non-oxidative and oxidative conditions at 25, 35, 45, and 55 degrees C. The delignification kinetic model of corn stover used three first-order reactions with following forms: W(L) = 0.09 x exp(-infinity x t) + 0.28 x exp(-k(2) x t) + 0.63 x exp(-k(3) x t) in non-oxidative pretreatment; W(L) = 0.16 x exp(-infinity x t) + 0.27 x exp(-k(2) x t) + 0.57 x exp(-k(3) x t) in oxidative pretreatment. The first term corresponds to the initial phase, which is essentially infinite at the time scale of the reaction (weeks). The second and third terms correspond to the bulk and residual phases of delignification. The activation energies for delignification in the oxidative lime pretreatment reactions were estimated as 50.15 and 54.21 kJ/mol in the bulk and residual phases, respectively, which are similar to the Kraft delignification of bagasse, but much less than in Kraft delignification of wood.