The role of leptin in striped hamsters subjected to food restriction and refeeding

Food restriction （FR） and refeeding （Re） have been suggested to impair body mass regulation and thereby making it easier to regain the lost weight and develop over-weight when FR ends. However, it is unclear if this is the case in small mammals showing seasonal forging behaviors. In the present study, energy budget, body fat and serum leptin level were measured in striped hamsters that were exposed to FR-Re. The effects of leptin on food intake, body fat and genes expressions of several hypothalamus neuropeptides were determined. Body mass, fat content and serum leptin level decreased during FR and then increased during Re. Leptin supplement significantly attenuated the increase in food intake during Re, decreased genes expressions of neuropepetide Y （NPY） and agouti-related protein （AgRP） of hypothalamus and leptin of white adipose tissue （WAT）. Hormone-sensitive lipase （HSL） gene expression of WAT increased in leptin-treated hamsters that were fed ad libitum, but decreased in FR-Re hamsters. This indicates that the adaptive regulation of WAT HSL gene expression may be involved in the mobilization of fat storage during Re, which partly contributes to the resistance to FR-Re-induced overweight. Leptin may be involved in the down regulations of hypothalamus orexigenic peptides gene expression and consequently plays a crucial role in controlling food intake when FR ends.

Seasonal differential expression of KiSS-1/GPR54 in the striped hamsters(Cricetulus barabensis)among different tissues

Kisspeptins and G protein coupled receptor(GPR54)play significant roles in regulating reproductive activity among seasonally reproductive animals;however,the mechanisms of KiSS-1 and GPR54 gene affecting the seasonal reproduction in striped hamster are still unknown.In this study,real-time quantitative polymerase chain reaction was employed to examine the expression profiles of KiSS-1 and GPR54 in the hypothalamus,ovaries,testes,uterus and epididymis of striped hamsters across 4 different seasons.Our results showed that,across different seasons,the KiSS-1 expression mode of male striped hamsters and the GPR54 expression mode of female striped hamsters were consistent with the seasonal photoperiod in the hypothalamus.Meanwhile,across different seasons,the expression profile of KiSS-1 in the testes and the GPR54 expression profile of male striped hamsters in the hypothalamus were consistent with the intensity of their seasonal reproductive activity.Among different tissues,the expression trend for GPR54 is consistent across 4 seasons,while that for KiSS-1 is tissue-dependent.The expression trend for GPR54 across 4 seasons is the same regardless of gender,while that for KiSS-1 is dramatically different and sex-dependent across different seasons.These results suggest that the expressions of KiSS-1 and GPR54 in the striped hamsters were regulated by complicated mechanisms,and the regulatory mechanisms in the striped hamsters are seasonal-dependent and sex-dependent.This research will provide a theoretical basis for studying how KiSS-1 and GPR54 affect seasonal reproduction and the mechanisms behind their influence.

Strategies of behavior,energetic and thermogenesis of striped hamsters in response to food deprivation

The life history of many animals includes periods of food shortage.Two behavioral strategies are involved in small mammals in response to food shortage:an increase in activity behavior,representing the increased foraging or migratory behavior,and a decrease in activity level,serving as a mechanism for conserving energy.However,it is uncertain whether animals adopt both strategies in response to food shortage,and whether hormone and neuroendocrine mechanisms are involved in both strategies.In the present study,changes in behavior and metabolic rate were examined in food-deprived striped hamsters(Cricetulus barabensis).The effects of leptin supplement on activity behavior,metabolic rate and hypothalamic neuropeptide gene expression were also examined.The behavior of food-deprived hamsters significantly changed with photoperiod phases:with increasing activity during the dark phase compared to those fed ad libitum,whereas decreasing activity and simultaneously increasing resting behavior during the light phase.Resting metabolic rate,body mass,and masses of fat depots and digestive tracts significantly decreased in food-deprived hamsters compared with ad libitum controls.Leptin supplement tended to attenuate the increased activity in the dark phase.Gene expression of hypothalamic neuropeptide Y(NPY)was significantly upregulated in food-deprived hamsters,while was significantly attenuated by exogenous leptin.These findings suggest that both behavior strategies are important behavioral adjustments in free-living animals to cope with food shortage.Leptin and hypothalamic NPY gene expression may be involved in the adjustments of physiology and behavior in animals demonstrating a hyperactivity strategy in response to food shortage.

高纤维食物对黑线仓鼠哺乳期能量收支的影响

繁殖期是小型哺乳动物最重要的生活史阶段之一,哺乳期是母体能量需求最高的时期。为满足后代的能量需求,母体通常显著增加能量摄入,达到最大持续能量摄入(maximal sustained energy intake,mSusEI)。动物消化道形态和消化机能具有可塑性,然而消化系统是否限制了哺乳期mSusEI,尚不确定。本文以高纤维食物饲喂哺乳期黑线仓鼠(Cricetulus barabensis),通过测定体重、摄食量、摄入能和消化率、代谢率、泌乳能量输出,以及消化系统重量和消化酶活性等,分析哺育不同胎仔数的母体能量摄入与繁殖输出,比较在不同能量需求的条件下,消化酶活性的变化。结果发现,黑线仓鼠哺乳期的能量收支与其哺育后代的数量有关,哺乳期mSusEI未受高纤维食物的显著影响。饲喂高纤维食物未影响摄入能,但显著降低了消化能和消化率,母乳能量输出也显著减少,不能满足后代幼体的能量需求,导致幼体发育变缓。高纤维食物使胃、小肠、大肠和盲肠重量显著增加,小肠淀粉酶、麦芽糖酶和氨基肽酶活性显著增强,但未受胎仔数的显著影响。结果表明,哺乳期mSusEI的瓶颈可能来自消化系统,支持中心限制假说。由于“中心限制”的存在,食物中纤维素含量升高可能会降低动物繁殖价值。

Temperature determines the shift of thermal neutral zone and influences thermogenic capacity in striped hamsters

The thermoneutral zone(TNZ)reflects the adaptation of mammals to their natural habitat.However,it remains unclear how TNZ shifts in response to variations in ambient temperature.To test the hypothesis that ambient temperature plays a key role in determining TNZ variations between seasons,we measured metabolic rate,body temperature,and cytochrome c oxidase(COX)activity of several visceral organs in striped hamsters(Cricetulus barabensis)either acclimated to semi-natural conditions over a year,or subjected to a gradual decrease in mean temperature from 30±1°C to-15±1°C.The TNZ range in striped hamsters differed seasonally,with a wider TNZ and a lower lower-critical temperature in winter compared to summer.The hamsters showed a consider-able leftward shift of lower-critical temperature from 30°C to 20°C after the ambient temperature of acclimation from 30°C down to-15°C,whereas the upper-critical temperature of TNZ remainedfixed at 32.5°C.The rest-ing metabolic rate in thermoneutral zone(RMRt),nonshivering thermogenesis(NST),and COX activity of brown adipose tissue,liver,skeletal muscle,brain,and kidneys,increased significantly in hamsters acclimated at lower ambient temperatures.Following acute exposure to 5°C and-15°C,hamsters acclimated to 32.5°C had signifi-cantly lower maximal NST and lower serum thyroid tri-iodothyronine(T3)levels compared to those kept at 23°C.Thesefindings suggest that acclimation to the upper-critical temperature of TNZ impairs the hamsters’thermo-genic capacity to cope with extreme cold temperature.Reduced ambient temperature was mainly responsible for the leftward shift of TNZ in striped hamsters,which reflects the adaptation to cold environments.

黑线仓鼠种群数量动态预测研究

1984—1991年3—10月,每月中旬在中国农科院草原研究所试验场的不同牧草和作物地进行调查,1984—1991年共捕获鼠4093只,其中黑线仓鼠2920只(♂♂1675,♀♀1245)占71.34％。黑线仓鼠种群数量季节和年度变化明显。利用电子计算机对黑线仓鼠种群数量进行分析,提出种群数量繁殖指数和动态模型以及短、中、长期预测公式,预测准确率为90.0％。并对影响种群数量的因素进行了初步分析。

黑线仓鼠的食物与食量

作者从1983年至1989年,在河北省三个不同的气候区,对农田中的黑线仓鼠(Cricetulus,bara-bensis)的食物与食量进行了调查。结果表明,黑线仓鼠主要取食农作物种子。同时取食草籽和根、茎、叶、花、果实及动物性食物。不同地区、不同作物地、不同季节和年度、不同性别鼠的食物差异显著。食物差异与鼠的种群繁值及数量动态有关。月夹捕率与颊囊中食物的总检出率和种子检出率正相关非常显著。直线回归方程式分别为y=38.388+2.866x n=60 r=0.343>r_(0.01)=0.325和y=29.734+2.669x r=0.394>r_(0.01360)=0.325。黑线仓鼠对食物的选择,主要受到食物质量的影响,同时也受到食物频度、作物的物候变化、动物的群落结构、种群密度、种内与种间竞争等多种因素的综合影响。在不同的时间和栖息地影响它食物选择的主要因素不同。日食量4-5g。

山东阳谷县黑线仓鼠种群数量预测预报

作者于１９８２—１９９２年对山东省阳谷县黑线仓鼠的种群数量作了调查，并应用逐步回归分析法预报了阳谷、薛城１９９３年３月份、５月份、８月份和１１月份黑线仓鼠的鼠害发生程度，预报值与实测值基本相符。

冷驯化和复温过程中黑线仓鼠产热的变化

为进一步阐明小型哺乳动物对环境低温的适应对策,测定了黑线仓鼠在冷驯化(5℃)和复温(23℃)过程中的基础代谢产热(基础代谢率,basal metabolic rate,BMR)和非颤抖性产热(non-shivering thermogenesis,NST)的变化。结果显示,在暖温环境下饲养的黑线仓鼠基础代谢率为1.23±0.10 mL O2.g-1.h-1,非颤抖性产热为4.69±0.34 mL O2.g-1.h-1均低于其体重异速生长方程计算的期望值;在冷驯化过程中,BMR增加,第3周达到最高值,比常温条件下增加了85.4%;NST随冷驯化时间的延长也有显著增加,第5周达最大值,比常温条件下增加了52.5%。在复温过程中,BMR和NST都降低,NST第1周即可降到初始水平。表明,在暖温条件下,黑线仓鼠具有较低的BMR和NST;在冷驯化过程中,通过增加BMR和NST,弥补低温下热量散失,维持恒定的体温,其中NST在冷适应增加产热中起主要作用。这些冷适应特征兼有北方物种和干旱沙漠物种的特点。

东北地区黑线仓鼠的代谢产热特征及其体温调节

为探讨寒冷地区黑线仓鼠 (Cricetulusbarabensis)的代谢产热特征及体温调节 ,本文采用封闭式流体压力呼吸仪对其代谢率、热传导和体温等热生物学指标进行了测定。结果显示 :在环境温度为 5～ 35℃的范围内 ,黑线仓鼠的体温基本维持恒定 ,平均体温为 36 33± 0 2 3℃ ;热中性区为 2 5～ 32 5℃ ;基础代谢率为 3 4 9±0 36mlO2 / (g·h) ;环境温度 (Ta)在 5～ 2 5℃范围内 ,代谢率 (MR)与Ta 呈负相关 ,回归方程为 :MR [mlO2 / (g·h) ]=9 6 0 - 0 2 2Ta (℃ ) ,在此范围内 ,黑线仓鼠的热传导率 (C)最低 ,平均为 0 2 8± 0 0 1mlO2 /(g·h·℃ ) ;代谢预期比和热传导预期比 (F值 )为 1 6 8。黑线仓鼠的基本热生物学特征为 :较高的BMR和热传导率 ,相对较低的体温和较宽的热中性区。这些特征可能限制了其在极端寒冷和干旱环境中的分布和生存.

黑线仓鼠肥满度的研究

1984—1989年,作者在呼和浩特地区野外捕获3008号黑线仓鼠标本进行了肥满度研究。结果表明,该鼠肥满度与栖息地和年龄无关,而有性别、季节和年度差异;肥满度年度变化与种群数量年度消长以及月均肥满度与月均捕获率的相关程度均未达到显著水平,说明该鼠的肥满度不能作为预测其种群数量的主要指标。

内蒙古库布齐沙地和呼和浩特平原黑线仓鼠种群繁殖特征的比较

为了解不同地理种群在适应当地栖息环境过程中的差异 ,于 1 996年利用直线夹日法对内蒙古呼和浩特平原和库布齐沙地环境 ,两个种群基因交流严重受阻的黑线仓鼠种群生殖特征进行了比较研究。结果表明 ,雌雄性比在平原环境较大 ,且秋季雌性明显增多 ,沙地环境全年维持稳定。平原环境雄性睾丸下降率在各季高于沙地环境近 2 0 %。平原环境雌性在夏季性成熟率较高 ,沙地环境为春季最高。平原环境中雌性怀孕率为春、夏季较高 ,沙地环境仅在春季最高 ,且小胎仔数 (窝仔数少于 4 )所占比例较高 ( 1 9 5% ) ,两个种群平均胎仔数分别为 6 0 (平原 )和 5 9(沙地 )。这一结果说明不同地理种群生殖特征的差异受环境条件限制明显。

黑线仓鼠体重和能量代谢的季节性变化

为阐明小型哺乳动物体重和能量代谢的季节性变化以及生理调节机制,将黑线仓鼠驯化于自然环境下12个月,测定其体重、能量收支、身体组织器官和血清瘦素水平的季节性变化。黑线仓鼠能量摄入和支出的季节性变化显著,冬季摄入能、基础代谢率(BMR)、非颤抖性产热(NST)显著高于夏季。体重季节性变化不显著,但身体组织器官重量呈现显著的季节性变化,冬季肝脏、心脏、肾脏以及消化道重量显著高于夏季。体脂含量夏季最高,冬季最低,冬季显著低于夏、秋和春季(P<0.01)。血清瘦素水平的季节性变化显著,夏季瘦素水平比秋、冬季分别高88.2%和52.4%(P<0.05)。结果表明,黑线仓鼠体重维持季节性稳定,与"调定点假说"的预测不同;但脂肪含量和血清瘦素季节性变化显著,符合该假说。夏季血清瘦素升高具有抑制能量摄入的作用,冬季血清瘦素可能是促进代谢产热的重要因子,瘦素对能量代谢和体重的调节作用与气候的季节性变化有关。

内蒙古库布齐沙地黑线仓鼠食物构成的季节变化

This study was carried out to reveal the seasonal dietary variation of striped hamster (Cricetulus barabensis ) in Kubuqi desert of Ordos semi-arid environment in 1996.The food composition was determined by checking stomach and pouch contents.The results showed that striped hamster ate more insects and seeds than other foods in spring.The food habit changed to plant leaves and seeds in summer.In autumn the food content was mainly seeds.The animal chose perennial and annual seeds alternatively between summer and autumn.This indicated that the food habit was modified by the availability of food resources and animals’need for water and energy in this arid environment.

呼和浩特地区黑线仓鼠种群动态研究

1984—1989年,每年3—11月中旬在呼和浩特郊区定点调查,共捕获黑线仓鼠2920只,本文分析了该鼠每年的种群数量变动和年龄结构,用臼齿咀嚼面磨损程度划分年龄组,研究种群年龄结构。种群数量年际变化较大,季节变化也较明显,一般年有两个繁殖高峰和数量高峰(后峰8—10月,前峰5—6月)。每年3—10月为繁殖期,平均每胎产仔6.2±0.1只,各年间繁殖有一定差异。

不同繁殖状态雌性黑线仓鼠对植物血凝素的反应模式

由植物血凝素(Phytohemagglutinin,PHA)诱导产生的肿胀反应是生态免疫学中被广泛使用的免疫学参数,通过注射部位的肿胀程度大体上可反映细胞介导的免疫和天然免疫的综合变化情况。为探讨小型哺乳动物不同繁殖状态对PHA的反应模式,以非繁殖期、妊娠期、哺乳期和断乳期的雌性黑线仓鼠为研究对象,测定了注射PHA和生理盐水前(0 h)及注射后6 h、12 h和24 h注射部位皮肤组织的增厚程度。结果显示:(1)黑线仓鼠对PHA的反应有两种模式:非繁殖期、妊娠期和断乳期对PHA的反应模式相似,都在注射后6 h最高,12 h和24 h后逐渐下降;哺乳期对PHA的反应在注射后6 h、12 h和24 h接近,彼此间的差异均不显著。(2)哺乳期黑线仓鼠的PHA反应高峰值有下降趋势,但与非繁殖期、妊娠期和断乳期高峰值之间的差异不显著。结果表明,黑线仓鼠在哺乳期对PHA的反应模式不同于其他繁殖阶段,且反应的高峰值被延迟,这对其存活可能有害,但有助于繁殖进程的延续和后代的生长发育。

库布其沙地黑线仓鼠种群数量动态的研究

１９９１～１９９６年４～１０月，每月中旬在中国农科院草原研究所鄂尔多斯高原沙地草场改良试验站不同生境类型上进行啮齿类调查，共捕获黑线仓鼠９８９只，占总捕获数的１３．１４％．利用ＰＣＡ分析、季节性指标、移动平均等方法对其数量动态的定量分析表明，季节动态呈单峰型，季节性比较明显，年间动态亦成明显的上升趋势，并对造成如此种群数量动态的影响因素作了初步分析，在数量动态分析的基础上，提出了一个用当年４，５，６三个月的捕获率预测次年７个月中最高捕获率月份的捕获率的预测模型。

鄂尔多斯沙地草场黑线仓鼠种群特征研究

目的 研究黑线仓鼠种群特征为预测和防制提供依据。方法 1991～ 1998年 4～ 10月每月中旬利用直线夹日法在中国农业科学院草原研究所鄂尔多斯沙地草场改良试验站进行调查 ,捕获鼠按常规测量称重后解剖 ,详细记录繁殖情况。结果 用胴体重划分成 5个年龄组 ,黑线仓鼠种群数量季节变动明显 ,年均捕获率差别不大 ,波动在0 .36 %～ 1.49%之间。 8年中黑线仓鼠总的性比为 5 8.2 9% ,只有 1998年雌性多于雄性 ,其余各年均是雄性多于雌性 ,黑线仓鼠在调查区繁殖期为 3～ 10月 ,8年间春季繁殖开始期无差别 ,结束期差别较大。雌性年平均怀孕率为 2 5 .93 % ,平均胎仔数 ( 5 .77± 0 .16 )个 ,怀孕率和胎仔数有年间差异。

低温对黑线仓鼠能量代谢、抗氧化能力和氧化应激的影响

为探讨低温对机体能量代谢、器官/组织抗氧化能力和过氧化自由基水平的影响及其内在联系,本研究测定了不同时间低温和梯度低温处理的黑线仓鼠的摄食量、体重、主要内脏器官/组织的过氧化物歧化酶(SOD)、过氧化氢酶(CAT)、H2O2和丙二醛(MDA)水平。低温使摄食量显著增加,但未影响体重。低温暴露42 d使心脏和骨骼肌MDA水平、骨骼肌SOD活性显著升高;梯度低温使脑和肾脏H2O2水平、肝脏和骨骼肌SOD活性显著降低,使脑、肝脏、肺、肾脏MDA水平,脑和小肠SOD活性显著升高。抗氧化能力和过氧化自由基水平在不同器官之间相关性存在差异,同一器官内二者的相关性在肾脏为100%,肝脏66.7%,骨骼肌50.0%。结果表明:(1)过氧化自由基的产生与低温暴露的时间和程度有关;(2)不同器官/组织过氧化自由基水平不同;(3)部分器官/组织抗氧化酶活性的变化与过氧化自由基水平的变化密切相关,可能是防止过氧化损伤的主要防御系统。

黑线仓鼠室内饲养与繁殖的研究

就黑线仓鼠的室内饲养及其繁殖习性的研究结果表明 :黑线仓鼠胆小怕惊 ,野鼠约 2 5 d方能适应关禁 ;对植物种籽的喜食性远大于植物营养枝 ;喜潮湿怕干燥 ;繁殖温度以 1 9℃左右为宜 ;性活动一般发生于夜间 ,性交持续时间 3～ 5 s,性周期 4 .38± 0 .2 9d,孕期 2 1 .2 d,每胎仔数平均 4 .70只 ,较野外鼠的 6 .0 7只低 ,哺乳期 1 7d,离乳率 89.36 % ,育幼任务完全由雌鼠承担 ;室内饲养条件比自然条件下繁殖周期延迟 1个月 .