Effect of temperature on antioxidant defense and innate immunity in Brandt’s voles

Ambient temperature is an importa nt factor in flue ncing many physiological processes, in eluding antioxidant defense and immunity. In the present study, we tested the hypothesis that antioxidant defense and immunity are suppressed by high and low temperature treatme nt in Bran dt's voles (Lasiopodomys brandtii). Thirty male voles were randomly assigned into different temperature groups (4, 23, and 32℃, n=10 for each group), with the treatment course lasting for 27 d. Results showed that low temperature in creased gross en ergy in take (GEI) and liver, heart, and kidney mass, but decreased body fat mass and dry carcass mass. With the decline in temperature, hydrogen peroxide (H2O2) concentration, which is indicative of reactive oxyge n species (ROS) levels, in creased in the liver, decreased in the heart, and was unchanged in the kidney, testis, and small intestine. Lipid peroxidation indicated by malonaldehyde (MDA) content in the liver, heart, kidney, testis, and small intestine did not differ among groups, implying that high and low temperature did not cause oxidative damage. Similarly, superoxide dismutase (SOD) and catalase (CAT) activities and total antioxidant capacity (TAOC) in the five tissues did not respond to low or high temperature, except for elevation of CAT activity in the testis upon cold exposure. Bacteria killing capacity, which is indicative of innate immunity, was nearly suppressed in the 4℃ group in contrast to the 23℃ group, whereas spleen mass and white blood cells were un affected by temperature treatment. The levels of testosterone, but not corticostero ne, were in flue need by temperature treatment, though neither were correlated with innate immunity, H2O2 and MDA levels, or SOD, CAT, and TAOC activity in any detected tissues. Overall, these results showed that temperature had different in flue nces on oxidative stress, an tioxida nt en zymes, and immunity, which depended on the tissues and parameters tested. Up-regulation or maintenance of an tioxida nt defe nse might be an importa nt mechanism for voles to survive highly variable environmental temperatures.

布氏田鼠(Microtus brandti)的食性

通过胃内容物显微组织学分析法,研究了内蒙古克什克腾旗阿其乌拉地区布氏田鼠春季和夏季的自然食性。该鼠于春季和夏季都最嗜食羊草,但食性有明显的季节变化,对食物有强烈的选择性特征,专化现象较为明显。植被的物候变化和植物体的蛋白质含量以及硅等矿质元素的含量是影响布氏田鼠进行选食的主要因素。文中还讨论了布氏田鼠的最优觅食行为。

越冬前布氏田鼠(Microtus brandti)储草行为与储草种类选择的研究

对典型草原布氏田鼠的储草行为和储草种类的选择性研究结果表明：（1）储草期间各洞系鼠群具有比较稳定的采集“领域”，其范围约400～1200m2；（2）平均每个洞系储草16．8±1．53kg（10．25～19．6kg），即每只鼠平均储草792．5±32．7g，储草仅可供其存活58．7天。由于该鼠在越冬期间的自然死亡率在80％以上（试验期间为83．5％）。故而仍有1／3～1／4的储草残留至翌年春季，在地下霉烂后进入土壤。（3）该地区被传的牧草种类仅3～4种。其中冷蒿的重量占总储量94％以上，选择性指数（PI）达5．67。（4）在低温条件下，饲喂冷蒿的鼠，其死亡；率明显低于饲喂禾草组。田鼠的储草对畜牧业生产，尤其是对绵羊抓膘将造成一定危害。

SARS-CoV对幼年和成年布氏田鼠的感染研究

采用鼻腔喷雾法(CCID50=105.7)研究了SARS冠状病毒(SARS-CoV)对成年和幼年布氏田鼠的感染效果.成年动物攻毒后出现死亡,表现为口鼻有出血,肠道出血;肺组织呈出血性间质性肺炎改变,肝、脾、肾、胰腺组织均呈淤血性改变;存活动物肺组织呈间质性肺炎,局灶出血及肺气肿改变,其他脏器未见明显病变.幼年动物攻毒后未见死亡但行动较为迟缓,主要脏器未见明显异常;早期肺组织有局限性肺炎改变,且病毒分离为阳性;同居对照组的一只动物有肺组织局灶性肺炎.结果表明,SARS-CoV可以很强地感染布氏田鼠;成年布氏田鼠比幼年动物对SARS-CoV更敏感;布氏田鼠有望成为一种比较理想的小型SARS动物模型。

Anti-fertility effect of levonorgestrel and quinestrol in Brandt’s voles(Lasiopodomys brandtii)

The combination of levonorgestrel and quinestrol(EP-1)has been shown to have anti-fertility effects on several wild rodents,but the mechanism underlying these effects is poorly understood.We investigated the effects of EP-1 and each of its components,levonorgestrel(P)and quinestrol(E),on the fertility of Brandt’s voles(Lasiopodomys brandtii)by using a gastric gavage method.The doses for EP-1,E and P were 1,0.34 and 0.66 mg/kg body weight,respectively.Male voles(n=98)were treated daily for 5 or 14 days,then the testes and epididymides were collected,weighed and examined histologically at 30(D30),60(D60)or 90(D90)days after the end of treatment.Four males were allowed to mate with normal females at D90.Female voles(n=75)were treated for 3 days and a further 3 days after a 7-day interval.The uteri and ovaries were weighed and examined histologically at 15(D15),30(D30)or 75(D75)days after the end of treatment.Each of three females were mated with fertile males at D30 and D75,respectively.Our results indicated that quinestrol(E)significantly decreased the sperm numbers in the testes as well as the weight of the testes and epididymides,with both of these tissues showing obvious structural abnormalities,and significantly reduced the litter size and the pup weight for females mated with males of the E treatment group.For female voles,treatment with E,P or EP-1 resulted in no marked influence on the fertility status.These data indicate that quinestrol(E)alone has a significant anti-fertility effect on male Brandt’s voles,but is ineffective in combination with levonorgestrel(P).

Kinship analysis reveals reproductive success skewed toward overwintered Brandt’s voles in semi-natural enclosures

Age structure and seasonality influence the population fluctuations of small rodents.Age determines body weight and social experience,while seasonality regulates the duration of the breeding season and onset of sex­ual maturity in newborn offspring.Therefore,reproductive success and skew usually occur in different age groups.Brandt’s vole(Lasiopodomys brandtii)is a social,short-lived and seasonal breeding small rodent with a dramatic seasonal population fluctuation,but reproductive skew is not fully understood in this species.In the present study,we determined kinship in semi-natural enclosure populations using microsatellite markers based on genotyping,analyzed the reproductive skew between sexes and between overwintered and newborn voles,and monitored variation in male reproductive activity by testing fecal testosterone levels throughout the year.Overwintered voles had the most reproductive success along with a striking increase in the population size in the enclosures,with all biological fathers and 77.8%of biological mothers,which had 100%and 87%of the to­tal offspring,respectively.Compared to overwintered voles,reproductive skews were significantly higher in po­tential overwintered and newborn parents,implying the possible reproductive suppression of newborn voles by dominant overwintered voles.Moreover,both heavier body weight and higher testosterone levels in overwin­tered males supported their potential social status in the population.Our study provided new evidence for repro­ductive skew and differentiation of postnatal gonadal development patterns of different age groups in Brandt’s vole.

不同雄雌配比对SPF级布氏田鼠繁殖性能的影响

目的探讨不同雄雌配比对SPF级布氏田鼠产仔数、成活率等繁殖性能的影响。方法设置4种配对繁殖方式:1♂:1♀、1♂:2♀、2♂:2♀和3♂:2♀,经过2年的试验,期间记录各组SPF级布氏田鼠的产仔数和成活率等繁殖性能指标。结果 4种配比方式雌鼠产仔率分别为97.69%、62.47%、59.24%和28.3%,成活率为96.98%、96.14%、94.57%和91.22%,平均产仔数为6.48、7.87、6.16和6.14。结论在屏障环境中饲养的布氏田鼠封闭群采用1♂:2♀的配比方式,其繁殖性能和经济效益最理想。

捕食风险应激对雄性布氏田鼠及子代繁殖性能的影响

本研究旨在探讨雄性布氏田鼠暴露于捕食风险应激对自身及后代繁殖性能的影响,以及这种效应的阶段性。青春期是动物生长发育和对外界环境敏感的重要阶段,推测青春期所经历的捕食风险应激对雄鼠和后代繁殖性能的影响更为显著。实验选取90日龄成年期和28日龄青春期雄性布氏田鼠作为亲代,每天分别暴露于蒸馏水、兔尿和猫尿1 h,连续18 d。随后每组随机选取一半田鼠取样检测性腺器官指数、精子质量和数量等参数,另一半与正常雌鼠交配,待后代成年后检测繁殖性能。结果显示,与对照相比,成年期和青春期暴露于猫气味的雄性布氏田鼠精子正常率显著下降,精子畸形率和死亡率显著升高,而暴露于兔气味的雄鼠仅降低了正常精子比例;成年期雄性田鼠暴露于猫气味没有影响繁殖输出,而青春期暴露的雄鼠的后代在出生时雌性比例显著增加;成年期暴露于猫气味和兔气味都没有影响后代的繁殖性能,青春期暴露于猫气味的雄鼠的后代成年后性腺指数、精子密度和精子正常率降低,精子畸形率和死亡率显著升高,而暴露于兔气味仅降低了雄性后代的精子密度和精子正常率。以上结果验证了本研究假设,即捕食风险应激对布氏田鼠亲代和后代的繁殖性能均有一定的抑制作用,且青春期应激的效应更强更持久,存在明显的效应阶段依赖性。

Effects of maternal stress induced by predator odors during gestation on behavioral and physiological responses of offspring in Brandt’s vole(Lasiopodomys brandtii)

Maternal effects play a crucial role in regulating populations of small mammals and anti-predator behaviors of offspring.The present study investigated the effects of maternal stress induced by exposure to predator odors during gestation on the behavioral and physiological responses of offspring in Brandt’s vole(Lasiopodomys brandtii).Effects included changes in growth,behaviors,hormone levels in serum,and fosB/ΔfosB mRNA and FosB/ΔFosB protein expression in the hypothalamus.Our results showed that when pregnant voles were exposed to cat and rabbit urine odors for 18 days(1 h/day),the weight of the female offspring decreased;however,the thymus and ovary indices increased,compared with the control group.Male offspring of voles exposed to cat odor spent more time exploring and foraging,and showed a decrease in corticosterone(CORT)compared with voles in the control group.Both fosB/ΔfosB mRNA and FosB/ΔFosB protein expressions were downregulated in the hypothalamus of male offspring in the cat odor-exposed group compared to that in offspring in the control group.However,the mRNA levels of fosB/ΔfosB in the hypothalamus of female offspring did not decrease in response to cat urine odor.Our findings suggested that maternal stress induced by predator odors during gestation restrained the growth of female offspring and increased the duration of exploring and foraging behaviors of male offspring by regulating the HPA axis,which,in turn,reduced the sensitivity of offspring to unfamiliar environments and increased their probability of becoming prey.

Infection of SARS-CoV on juvenile and adult Brandt＇s vole Microtus brandtii

We studied the infectious effect of SARS-CoV virus on juvenile and adult Brandt’s Vole (Microtus brandtii) by nasal cavity spraying method (CCID50 is 105.7). SARS virus caused serious deaths in adults. The death adults demonstrated hemorrhage from mouth, nasal cavity and intestine, hemorrhageious interstitial pneumonia and gore in liver, spleen and kidney. The survival adults demonstrated local hemorrhagic spot in lung and emphysema, but the other organs showed no pathological abnormality. SARS virus caused no deaths in juveniles, but locomotion of infected juveniles became slower. In the early stage, there was local pneumonia in lung and SARS viruses were isolated from the pathological tissue. Only one control juvenile lived and the infected juvenile showed local pneumonia in lung. The results demonstrated that SARS-CoV infected Brandt’s vole seriously and adults were more susceptive to SARS-CoV than juveniles. The Brandt’s vole may be a potential animal model for SARS research.

布氏田鼠标志种群的繁殖参数

采用标志重捕和染色观测法跟踪了内蒙古典型草原区布氏田鼠野外种群 ,按绝对时间年龄研究其种群繁殖参数。结果表明 :4～ 5月份出生的雄鼠能在当年达到性成熟 ,性成熟发育历期约为 1 5个月 ,6月后出生的雄鼠当年达不到性成熟。在达到性成熟的当年雄鼠中 ,多数个体再度转入性休止期 ,其平均繁殖结束时间要比越冬雄鼠早 1个月 ,而越冬雄鼠则在整个繁殖期保持性活动状态。雌鼠性成熟发育历期约为 1个月 ,首次产仔时间约为2月龄。雌鼠在一年中的产仔窝数与其年龄有关 :越冬鼠能产 3～ 4窝 ,4月份出生的雌鼠能产 2～ 3窝 ,5月份出生的雌鼠当年能产 1～ 2窝 ,6月份出生的雌鼠能产 0～ 1窝 ,7月份之后出生雌鼠当年不参加繁殖。在自然条件下 ,布氏田鼠一生中最多能产

典型草原区布氏田鼠的活动节律及其季节变化

采用标志重捕、染色标记和野外观测法研究典型草原区布氏田鼠野外实验种群，采用4种活动模式指数（日活动差异指数θ，昼行性指数λ，峰型指数φ；活动强度指数η）分析田鼠昼夜活动节律及其季节变化。结果表明，布氏田鼠全年12个月的昼行性指数A均高于0．542，为典型的昼行性种类。其活动节律的季节变化主要与环境温度有关：1、2、3、4、11、12月，气温较低，布氏田鼠的活动模式呈典型的单峰型；5、6、7月气温较高，为典型的双峰型；而8、9、10月则属于单双峰过渡类型。田鼠的峰型指数西在冬季最低，夏季最高，与月均气温呈显著的正相关关系（r=0．89，n=12，P〈0．05）。活动强度指数研与气温也存在显著的正相关（r=0．94，n=12，P〈0．05）。5～9月，布氏田鼠的活动强度最高，每日活动时问在6h以上；冬季布氏田鼠的日活动量骤降，很少外出活动，尤其在1～2月，布氏田鼠日均地面活动时间不足1min。另外，室内实验表明，布氏田鼠具有在黑暗环境中活动能力，但在野外条件下，夜间活动极少发生。

灭鼠后布氏田鼠种群特征的研究

1987和1988年4—5月,笔者在内蒙古正镶白旗布氏田鼠危害严重的草场上,连续两年用药物灭鼠。调查结果表明,在布氏田鼠种群数量上升或下降的年份,春季灭鼠均能控制当年的鼠害。鼠密度高时,灭鼠后鼠种群年龄结构、性比、怀孕率和睾丸下降率均发生改变。鼠密度低时,灭鼠对种群特征影响不显著。

渐变的光周期和温度对布氏田鼠能量代谢和身体成分的影响

为探讨在同时逐渐缩短光照时间和降低温度的过程中,动物能量代谢水平和身体成分的适应性变化,我们以成年雄性布氏田鼠为对象,测定了温度为20℃和光周期为12L∶12D (对照组),以及从温度为20℃和长光照条件(16L∶8D)逐渐转换到温度为4℃和短光照条件(8L∶16D)的过程中(实验组),其体重、静止代谢率和能量摄入的变化,以及经过8周驯化后身体器官和组织重量的变化。结果发现:实验组动物的体重增长率低于对照组。在驯化期间,静止代谢率无组内和组间差异。实验组动物的干物质摄入、能量摄入和消化能等组内差异不明显,但对照组动物在驯化的第8周显著降低。实验组动物的能量摄入水平在驯化后显著升高;小肠和胃的干重,以及小肠和心脏等器官的湿重也都显著高于对照组。结果表明,布氏田鼠能够采取降低体重、增加能量摄入和调整体内某些器官和组织重量的方式来适应变化的环境条件。

粪便激素水平反映不同出生时期雄性布氏田鼠的繁殖策略

布氏田鼠是我国内蒙古草原的主要害鼠之一,具有明显的季节繁殖特征,不同季节出生个体可能具有不同的繁殖发育策略,但尚缺乏内分泌证据支持。本研究采用标志重捕法,连续监测大型自然围栏中不同年龄雄性布氏田鼠的繁殖状态和应激水平的季节变化,分析各年龄组雄鼠的繁殖发育策略。结果表明,越冬雄鼠可保持较高的睾丸下降率和睾酮水平至8月初;而部分5月生雄鼠的繁殖期睾酮水平较接近越冬鼠,8月初降至年内最低水平,而6月及以后出生雄鼠睾酮始终处于较低水平;这说明越冬鼠的繁殖状态可贯穿繁殖期始终,只有部分5月生雄鼠可能参与当年繁殖,而6月及以后出生雄鼠则不能在当年繁殖。越冬鼠皮质醇水平高于当年鼠,繁殖期高于非繁殖期,这可能是越冬鼠由于繁殖需要而保持较高应激状态,从而造成繁殖盛期后死亡率升高。这些结果说明,不同时期出生的雄性布氏田鼠具有不同的出生后性腺发育模式和繁殖策略,反映出生存与繁殖之间的权衡。

布氏田鼠嗅觉通讯的行为发育─幼体对群体气味的辨别

对15～30日龄的布氏田鼠幼体对不同群体气味的行为反应进行了研究,探讨了幼体的嗅觉通讯行为发育过程及其对群体气味的识别能力。幼体对自身群体气味的探究行为明显多于对陌生群体的探究,但这种差异仅在24日龄以后才表现出显著性;幼体通常避开陌生群体的巢垫物而更多地从自身群体巢垫物上跨过;对陌生群体气味的嗅闻频次上雄性幼体明显高于雌体,而雌体的挖掘行为显著多于雄体。随着日龄的增加,幼体对群体气味的嗅闻行为无明显变化,而对巢垫物的挖掘行为显著增多;在实验过程中的逃逸行为—跳跃,随日龄的增加而显著增多。说明布氏田鼠幼体具有对群体气味的辨别能力;对陌生群体气味的回避可能是幼体在断乳后出巢期间防御危险的行为适应。

雷公藤制剂对雄性布氏田鼠的不育作用

采用强制给药和自由取食2种方式,研究了雷公藤制剂对发育期成体雄性布氏田鼠不育作用,给药剂量分别为80mg/kg、120mg/kg和160mg/kg。结果表明,120mg/kg和160mg/kg剂量使睾丸脏器系数下降,但剂量组间差异不明显(F(3,21)=2.197,F0.05=3.07,P>0.05)。不同剂量能够对附睾中精子数量和活力产生显著影响(F(3,21)=17.305,F0.05=3.07,P<0.05),且随药物剂量的升高精子密度与精子活力均呈下降趋势。精子畸形率亦随药物剂量的增加而增加。80mg/kg及其更高的剂量使附睾出现萎缩并造成睾丸组织损伤。120mg/kg剂量可减少布氏田鼠平均胎仔数及降低繁殖率。给药后的繁殖后代未发现畸形幼仔。雷公藤制剂的最佳使用剂量介于120～160mg/kg。自由取食与连续强制给药两种方式对雄性布氏田鼠的作用差异不显著。

繁殖季节和非繁殖季节布氏田鼠种群参数和生理特点的差异

在繁殖季节(6月份)和非繁殖季节(10月份),采集了内蒙古自治区阿尔善宝力格地区的布氏田鼠样本,比较其种群参数与生理指标,探讨了布氏田鼠社群结构和生理特征的季节性差异,并分析了原因。结果表明,布氏田鼠的年龄组成和性比存在明显的季节差异:繁殖季节洞口系数小,种群性比接近1,主要由当年新生鼠和越冬鼠组成;非繁殖季节洞口系数大,种群性比偏雄,主要由当年新生鼠组成。繁殖器官在繁殖季节显著大于非繁殖季节,保持了更高活性。非繁殖季节个体的胴重比更高,且雄鼠高于雌鼠,表明非繁殖季节个体和雄鼠具有更好的营养状态;同时,非繁殖季节个体具有更小的肾上腺和更大的脾脏,说明非繁殖季节中的布氏田鼠表现出更低的应激状态和更强的免疫能力。这些研究结果表明,布氏田鼠的种群参数和生理特点具有明显的季节性特点,这与不同季节中布氏田鼠采取的生存策略有着紧密联系。

密度因素在布氏田鼠种群调节中的作用

对布氏田鼠栖息密度不同的种群同时进行取样,研究密度因素对布氏田鼠种群发展的调节作用。结果表明,在高密度区布氏田鼠种群繁殖强度受到抑制,雌鼠怀孕率、雄鼠睾丸下降率、贮精囊肥大率和睾丸长度都小于低密度种群。高密度种群繁殖季节结束时间早于低密度种群,幼鼠肥满度较小,性成熟速度较慢,种群年龄结构中,幼年鼠所占比例小于低密度种群。这些都是导致高密度种群增长速度减慢的因素。

布氏田鼠栖息地特征的研究

依据2008-2010年在中蒙2国的实地调查,研究了布氏田鼠(Lasiopodomys brandtii)对栖息地的选择特点,以期为该鼠的综合防治提供依据。选择316个样点,记录每个样点的布氏田鼠密度,并随机调查5～10个1m×1m的样方,记录海拔、植被盖度、植被高度、枯草盖度、植被优势种、郁闭指数和退化级别。利用相关性分析及因子分析选取布氏田鼠栖息地选择影响较大的因子。结果表明:布氏田鼠密度与植被盖度、枯草盖度、退化等级及郁闭指数相关;冷蒿(Artemisia frigida)、羊草(Leymus chinensis)和多根葱(Allium polyrhizum)3种植物多度、枯草盖度、植被盖度、草场退化程度和植被郁闭指数5个因子对该鼠选择栖息地影响显著,即布氏田鼠倾向于选择以冷蒿、羊草、多根葱为优势种,放牧利用程度高、植被低矮的退化草场。