冷驯化条件下大绒鼠的产热和能量代谢特征

本文主要研究了冷驯化(5℃±1℃)条件下,大绒鼠(Eothenomys miletus)的能量收支、基础代谢率(BMR)、非颤抖性产热(NST)和肝脏线粒体呼吸.结果表明:随着冷驯化的进行,大绒鼠的体重、体温降低;摄入能、消化能、可代谢能增加;BMR和NST增加;肝脏线粒体呼吸状态Ⅲ呼吸先增加,28天后趋于平稳;线粒体状态Ⅳ呼吸先增加,28天后下降.说明在冷驯化条件下,大绒鼠采取适当降低体重和体温、增加能量摄入、增加BMR和NST产热的对策来维持能量平衡     

高原鼠兔冷驯化和脱冷驯化中的产热变化

本文探讨了冷驯化和脱冷驯化对高原鼠兔代谢产热的影响。在冷驯化中，鼠兔的静止代谢率逐渐增加，血清Ｔ３‘／Ｔ４比率上升，肝线粒体状态３呼吸明显增加，线粒体细胞色素Ｃ氧化酶激活，而肝脏线粒体蛋白含量没有明显变化。     

长期强迫运动对大绒鼠体重、能量代谢和血清瘦素的影响

动物稳定体重的维持需要能量摄入和消耗之间的平衡。运动是影响动物能量平衡的重要因素之一。为了解运动对大绒鼠(Eothenomys miletus)的生理学效应,在室内条件下,测定了强迫运动训练(运用小鼠封闭跑台)8周后大绒鼠的体重、代谢率、摄入能、血清瘦素和身体组成的变化。结果显示,强迫运动训练8周对大绒鼠的体重无显著影响;大绒鼠的代谢率和摄入能均显著增加,训练8周后静止代谢率较对照组增加了29.9%,运动最大代谢率较对照组增加了10.7%;强迫运动训练8周组的身体脂肪重量比对照组降低了28.9%,血清瘦素水平比对照组下降了27.4%,对照组的瘦素与体脂含量具有明显的相关性,但运动组则不具有相关性;运动组的肝重量和消化道重量较对照组均显著增加;而体水重量则显著降低。这些结果表明,在强迫运动训练期间大绒鼠主要通过动员储存的脂肪、增加代谢率和食物摄入的方式来维持自身的体重及能量平衡。瘦素在长期强迫运动过程中对身体脂肪含量的变化具有调节作用。     

食物限制对雄性大绒鼠能量代谢特征的影响

为探讨横断山区大绒鼠适应食物匮乏的适应对策,将成年雄性大绒鼠随机分为自由取食组和饲喂正常摄食量的80% 限食组。测定了自由取食组和限食组雄性大绒鼠的体重、静止代谢率、非颤抖性产热以及体脂含量、血清瘦素含量、肝脏鲜重、褐色脂肪组织重量和消化道形态。结果显示:限食使雄性大绒鼠的体重、体脂含量、静止代谢率、非颤抖性产热、褐色脂肪组织重量和大肠、小肠长度显著降低,使盲肠内容物重量显著增加。血清瘦素含量与体重、体脂含量呈极显著正相关。在限食条件下,大绒鼠主要通过降低体重、基础代谢和产热的能量支出以及动用体内脂肪以应对食物资源短缺的环境条件,瘦素可能参与了能量代谢和体重的适应性调节。     

大绒鼠在不同驯化温度下产热和能量代谢的变化

为研究不同温度驯化条件下大绒鼠体重、体温和能量代谢水平的可塑性变化,本实验测定了热驯化(30℃ ;12L∶ 12D)转脱热驯化(5℃ ;12L∶ 12D)和冷驯化(5℃ ;12L∶ 2D) 转脱冷驯化(30℃ ;12L∶ 12D)条件下,大绒鼠体重、体温、能量收支、静止代谢率和非颤抖性产热的变化。结果表明:大绒鼠在热驯化转脱热驯化过程中,随着热驯化时间的延长,大绒鼠体重和体温增加,摄入能、静止代谢率和非颤抖性产热逐渐降低,在28 d 时降到最低;转到脱热驯化条件下,表现出相反的趋势。冷驯化转入脱冷驯化过程中,随着冷驯化时间的延长,大绒鼠的体重和体温降低,摄入能、静止代谢率和非颤抖性产热逐渐升高,28 d 时达到最高;转移到脱冷驯化条件时,表现出相反的趋势。以上结果说明大绒鼠在不同温度驯化条件下,其体重、能量代谢和产热具有可塑性变化,即通过调节体重、体温和能量代谢来适应不同温度变化。     

季节性模拟对大绒鼠能量代谢的影响

本实验主要阐明大绒鼠Eothenomys miletus在季节性模拟过程中体质量调节和能量代谢的变化。实验组大绒鼠在模拟夏季环境中(25℃,16L∶8D)驯化14 d后转入模拟冬季环境中(5℃,8L∶16D)驯化8 d,实验中每隔1 d测定大绒鼠的体质量、摄食量,每隔7 d测定其静止代谢率,实验结束后测定体脂含量和血清瘦素浓度。结果表明:季节性模拟条件下大绒鼠的体质量变化差异具有统计学意义(F=1.911,P0.05),22 d后实验组体质量比对照组下降12.54%;摄食量变化差异具有高度统计学意义(F=8.850,P0.01),22 d后实验组摄食量比对照组显著增加58.23%;静止代谢率变化差异具有高度统计学意义(F=9.969,P0.01),22 d后实验组比对照组显著增加82.22%;体脂含量和血清瘦素浓度呈显著正相关。以上实验结果表明:大绒鼠在模拟夏季转冬季的过程中主要通过降低体质量、增加摄食量和产热等来适应冷环境的胁迫。此外,瘦素有可能参与了大绒鼠在该环境下的体质量调节。     

限食程度对大绒鼠体重和产热特征的影响

为阐明动物应对食物短缺的能量学对策,将成年大绒鼠按自由取食量的90%、80%和70%限食4周。测定了不同限食程度下大绒鼠的存活率、体重、体脂含量、血清瘦素浓度、基础代谢率和非颤抖性产热。结果发现,90%限食驯化4周后,动物没有死亡,80%限食驯化4周后,存活率为90%,而70%限食驯化4周后,存活率仅为60%。限食使大绒鼠体重、体脂含量、血清瘦素浓度、基础代谢率和非颤抖性产热降低。血清瘦素浓度与体重、基础代谢率和非颤抖性产热呈显著正相关。结果表明,在限食条件下,大绒鼠主要通过降低体重、基础代谢率和产热的能量支出以及动用体内脂肪以应对食物资源短缺的环境条件,符合"代谢率转换"假说。瘦素作为饥饿信号可能参与了限食条件下大绒鼠能量代谢和体重的适应性调节。     

大绒鼠体温调节和产热特征

大绒鼠为横断山脉地区小型哺乳动物的典型代表; 其体温仅能在15～30℃范围内维持稳定; 在热中性区内, 最低静止代谢率为2.71±0.13 ml O₂/g.h, 为其体重预期值的203.2±10.13%; F-值 {(RMR/Me)/(Cm/ C'} 为0.99±0.05; 在 25℃的NSTmax为 5.18±0.19)ml O₂/g.h; BAT 重量为0.33±0.05 g, 为体重的0.84%, BAT细胞线粒体的产热活性较高;肝脏也具有较强的产热活性。大绒鼠的产热特征和体温调节模式很可能反映了横断山地区小型啮齿动物的特征。     

冷驯化对大绒鼠和高山姬鼠肝脏线粒体呼吸的影响

大绒鼠Eothenomys miletus和高山姬鼠Apodemus chevrieri为横断山地区小型哺乳动物的代表.分别测定大绒鼠和高山姬鼠冷驯化组(7 d、14 d、21 d、28 d)与对照组(0 d)中肝脏线粒体蛋白含量、呼吸状态Ⅲ和状态Ⅳ、呼吸磷氧比的变化以及较大绒鼠和高山姬鼠的相应项,探讨大绒鼠和高山姬鼠对不同冷环境的适应情况以及肝脏产热的机理.结果 表明:在冷驯化条件下,大绒鼠和高山姬鼠的产热显著增加,无论是大绒鼠还是高山姬鼠实验组比对照组肝脏线粒体蛋白含量、呼吸状态Ⅲ和状态Ⅳ、呼吸磷氧比有着显著的提高,在两者的比较中,在同等冷驯化条件下高山姬鼠增加的程度高于大绒鼠.     

温度和增加胎仔数对大绒鼠哺乳期能量代谢的影响

为了阐明温度和增加胎仔数对大绒鼠Eothenomys miletus哺乳期能量代谢的影响,本研究测定了在不同温度条件下增加胎仔数(比正常胎仔数多),大绒鼠的摄食量、胎仔数、胎仔质量、静止代谢率、非颤抖性产热和乳腺质量。结果表明:不同胎仔数对大绒鼠的摄食量、胎仔质量和产热能力没有影响。低温增加了母体的摄食量和产热能力,断奶时低温组的胎仔质量显著低于常温组。低温组和常温组大绒鼠的乳腺质量差异无统计学意义。研究结果说明低温可以增加大绒鼠摄食量,但是对乳腺质量没有影响,表明大绒鼠哺乳期的持续能量摄入上限可能受到乳腺分泌乳汁的限制,支持外周限制假说。     

Effects of cold acclimation on body mass,serum leptin level,energy metabolism and thermognesis in Eothenomys miletus in Hengduan Mountains region

Eothenomys miletus is an important species inhabiting Hengduan mountains region. In order to study adaptive strategy and the role of serum leptin level in response to a 49 d cold exposure, body mass, energy intake, basal metabolic rate (BMR), nonshivering thermogenesis (NST) in E. miletus were measured. During cold exposure (5±1 ^oC), body mass decreased; serum leptin levels decreased significantly and were positively correlated with body mass and fat mass; energy intake, BMR and NST were higher at 5 °C than that of controls. These results suggest that E. miletus enhanced thermogenic capacity and increased maintenance cost during cold acclimation, resulting in increased energy intake. Serum leptin participated in the regulation of energy balance and body mass in E. miletus.     

Adaptive character of metabolism in Eothenomys miletus in Hengduan Mountains region during cold acclimation

Environmental factors play an important role in the seasonal adaptation of body mass and thermogenesis in small, wild mammals. The purpose of the present study was to test the hypothesis that ambient temperature was a cue to trigger the seasonal adjustments in body mass, energy intake, uncoupling protein 1 (UCP1) in brown adipose tissue (BAT), and other biochemical characteristics of Eothenomys miletus during 49 days of cold exposure. Our data demonstrated that cold acclimation induced a remarkable decrease in body mass, a significant increase in energy intake and metabolic rate, and high expression of UCP1 in BAT of E. miletus. Biochemical characteristics of BAT and liver respiration were also increased following cold acclimation. These data suggest that E. miletus reduced the body mass and increased energy intake and expenditure under cold acclimation. Increased expression of UCP1 was potentially involved in the regulation of energy metabolism and thermogenic capacity following cold acclimation.     

Evaporative water loss and energy metabolic in two small mammals,voles (Eothenomys miletus) and mice (Apodemus chevrieri), in Hengduan mountains region

Evaporative water loss (EWL) and energy metabolism were measured at different temperatures in Eothenomys miletus and Apodemus chevrieri in dry air. The thermal neutral zone (TNZ) of E. miletus was 22.5–30 °C and that of A. chevrieri was 20–27.5 °C. Mean body temperatures of the two species were 35.75±0.5 and 36.54±0.61 °C. Basal metabolic rates (BMR) were 1.92±0.17 and 2.7±0.5 ml O₂/g h, respectively. Average minimum thermal conductance (C_m) were 0.23±0.08 and 0.25±0.06 ml O₂/g h °C. EWL in E. miletus and A. chevrieri increased with the increase in temperature; the maximal EWL at 35 °C was 4.78±0.6 mg H₂O/g h in E. miletus, and 5.92±0.43 mg H₂O/g h in A. chevrieri. Percentage of evaporative heat loss to total heat production (EHL/HP) increased with the increase in temperature; the maximal EHL/HP was 22.45% at 30 °C in E. miletus, and in A. chevrieri it was 19.96% at 27.5 °C. The results may reflect features of small rodents in the Hengduan mountains region: both E. miletus and A. chevrieri have high levels of BMR and high levels of total thermal conductance, compared with the predicted values based on their body masses, while their body temperatures are relatively low. EWL plays an important role in temperature regulation.     

Effects of photoperiod on energy intake, thermogenesis and body mass in Eothenomys miletus in Hengduan Mountain region

The present study was designed to examine whether photoperiod alone was effective to induce seasonal changes in physiology in voles (Eothenomys.) from the Hengduan Mountain region. Eothenomys miletus were randomly assigned into either long photoperiod (LD; 16L: 8D) or short photoperiod (SD; 8L: 16D) for 4 weeks at constant temperature (25 °C). At the end of acclimation, SD voles showed lower body mass and body fat coupled with higher energy intake than LD voles. SD greatly enhanced the thermogenic capacity of E. miletus, as indicated by an elevated nonshivering thermogenesis (NST), mitochondrial protein in brown adipose tissue (BAT); basal metabolic rate (BMR) was also raised. Although no variations in serum leptin levels were found between SD and LD voles, serum leptin levels were positively correlated with body mass and body fat mass, and negatively correlated with energy intake and UCP1 content in BAT, respectively. To summarize, SD alone is effective in inducing higher thermogenic capacities and energy intake coupled with lower body mass and body fat mass in root voles. Leptin is potentially involved in the photoperiod induced body mass regulation and thermogenesis in E. miletus. Our study shows that SD alone is effective.     

Metabolism,thermoregulation and evaporative water loss in the Chaotung Vole (Eothenomys olitor) in Yunnan-Kweichow Plateau in summer

Proper adjustment of thermoregulatory mechanisms ensures the survival of mammals when they are subjected to seasonal changes in their natural environment. To understand the physiological and ecological adaptations of Eothenomys olitor, we measured their metabolic rate, thermal conductance, body temperature (T_b) and evaporative water loss at a temperature range of 5–30 °C in summer. The thermal neutral zone (TNZ) of E. olitor was 20–27.5 °C, and the mean body temperature was 35.81±0.15 °C. Basal metabolic rate (BMR) was 2.81±0.11 ml O₂/g h and mean minimum thermal conductance (C_m) was 0.18±0.01 ml O₂/g h °C. Evaporative water loss (EWL) in E. olitor increased when the ambient temperature increased. The maximal evaporative water loss was 6.74±0.19 mg H₂O/g h at 30 °C. These results indicated that E. olitor have relatively high BMR, low body temperature, low lower critical temperature, and normal thermal conductance. EWL plays an inportant role in temperature regulation. These characteristics are closely related to the living habitat of the species, and represent its adaptive strategy to the climate of the Yunnan-Kweichow Plateau, a low-latitude, high-altitude region where annual temperature fluctuations are small, but daily temperature fluctuations are greater.     

禁食和重喂食对大绒鼠消化道长度与重量的影响

为探讨禁食和重喂食对栖息于横断山地区大绒鼠(Eothenomys miletus)消化道形态的影响,对禁食和重喂食条件下大绒鼠消化道各项指标进行了测定.实验分别测定了大绒鼠禁食12h、24 h、36 h和重喂食12 h、48 h、7d后的总消化道、胃、小肠、大肠、盲肠的长度及其含内容物重、去内容物重、干重.结果表明:禁食后,总消化道含内容物重、胃含内容物重和胃去内容物重增加,重喂食7d后均恢复到对照组水平.小肠含内容物重在禁食12h时最大,在重喂食12h时最小,重喂食48 h后恢复到对照组水平.禁食和重喂食条件下,大绒鼠的大肠和盲肠各指标均没有显著变化.以上结果表明,大绒鼠在食物受到限制、饥饿等胁迫因子作用下,可能通过调节消化道形态来满足部分能量需求,维持正常的生理机能.大绒鼠的消化道在禁食和重喂食中表现出的变化模式,可能与其食物资源时常波动的野外生存环境有关,从一方面反映了该物种在食物胁迫下的生存机制和适应对策.     

Thermogenesis, energy intake and serum leptin in Apodemus chevrieri in Hengduan Mountains region during cold acclimation

Environmental factors play an important role in the seasonal adaptation of body mass and thermogenesis in small, wild mammals. The purpose of the present study was to test the hypothesis that ambient temperature was a cue to trigger the adjustments in body mass, energy intake, and serum leptin level in Apodemus chevrieri during 42 days of cold exposure. Our data demonstrated that cold acclimation induced a decrease in body mass and a significant increase in energy intake in A. chevrieri. Serum leptin levels were positively correlated with body mass and fat mass. These data suggest that A. chevrieri reduced the body mass and increased energy intake and thermogenic capacity under cold acclimation. Further, serum leptin appears to be involved in the energy intake regulation and thermoregulation.     

Acclimation of entomopathogenic nematodes to novel temperatures: trehalose accumulation and the acquisition of thermotolerance

The effect of thermal acclimation on trehalose accumulation and the acquisition of thermotolerance was studied in three species of entomopathogenic nematodes adapted to either cold or warm temperatures. All three Steinernema species accumulated trehalose when acclimated at either 5 or 35 degrees C, but the amount of trehalose accumulation differed by species and temperature. The trehalose content of the cold adapted Steinernema feltiae increased by 350 and 182%, of intermediate Steinernema carpocapsae by 146 and 122% and of warm adapted Steinernema riobrave by 30 and 87% over the initial level (18.25, 27.24 and 23.97 microg trehalose/mg dry weight, respectively) during acclimation at 5 and 35 degrees C, respectively. Warm and cold acclimation enhanced heat (40 degrees C for 8h) and freezing (-20 degrees C for 4h) tolerance of S. carpocapsae and the enhanced tolerance was positively correlated with the increased trehalose levels. Warm and cold acclimation also enhanced heat but not freezing tolerance of S. feltiae and the enhanced heat tolerance was positively correlated with the increased trehalose levels. In contrast, warm and cold acclimation enhanced the freezing but not heat tolerance of S. riobrave, and increased freezing tolerance of only warm acclimated S. riobrave was positively correlated with the increased trehalose levels. The effect of acclimation on maintenance of original virulence by either heat or freeze stressed nematodes against the wax moth Galleria mellonella larvae was temperature dependent and differed among species. During freezing stress, both cold and warm acclimated S. carpocapsae (84%) and during heat stress, only warm acclimated S. carpocapsae (95%) maintained significantly higher original virulence than the non-acclimated (36 and 47%, respectively) nematodes. Both cold and warm acclimated S. feltiae maintained significantly higher original virulence (69%) than the non-acclimated S. feltiae (0%) during heat but not freezing stress. In contrast, both warm and cold acclimated S. riobrave maintained significantly higher virulence (41%) than the non-acclimated (14%) nematodes during freezing, but not during heat stress. Our data indicate that trehalose accumulation is not only a cold associated phenomenon but is a general response of nematodes to thermal stress. However, the extent of enhanced thermal stress tolerance conferred by the accumulated trehalose differs with nematode species.