Chromosomal polymorphism of mandarin vole,Microtus mandarinus (Rodentia)

The mitotic and meiotic chromosomes of mandarin vole, Microtus mandarinus Milne-Edwards, from Shandong Province of China were analyzed by conventional, G- and C-banding and Silver-staining techniques. We detected chromosomal polymorphism in the vole, exhibiting diploid chromosome numbers 2n = 48-50 and variable morphology of the 1st pair, one medium sized telocentric pair and the X chromosomes. Four types of karyotypes were revealed in the population. According to banding analysis, there were pericentric inversion, Robertsonian fusion and translocation in M. mandarinus karyotype evolution. The X displayed two different morphologies, which could be explained by prericentric inversion and a telocentric autosome translocation.     

棕色田鼠XO雌体的减数分裂

采用诱导卵泡发育、卵母细胞培养、制备减数分裂染色体标本等技术 ,对棕色田鼠两种雌体 (XO、XX)的减数分裂进行了比较研究。研究结果表明 :棕色田鼠XO和XX雌体在表型和内外生殖器结构上无差异 ;在用孕马血清促性腺激素刺激XO雌体和XX雌体后 ,两者卵巢上的有腔卵泡数目相近 ;两者产生的卵母细胞数目、生发泡破裂数目以及第一极体排放数目 ,统计学分析差异都不显著。同时表明XO雌体的减数分裂过程正常 ,能得到卵母细胞中期Ⅱ分裂相。据此我们认为 :雌体 (XO)与雌体 (XX)的卵巢功能都正常 ,两者的卵母细胞均具有较强的成熟能力且无差异。因此 ,棕色田鼠XO个体是核型异常、育性正常的雌体。另外 ,具有三种遗传性别的棕色田鼠可能是处于XX/XY与XO/XY性别决定系统进化途径的中间类型 ,其性别决定系统仍处于变化之中     

棕色田鼠与沼泽田鼠犁鼻器和副嗅球的组织结构

用组织学方法研究了棕色田鼠(Microtus mandarinus)、沼泽田鼠(M．fastis)副嗅球和犁鼻器的结构及其在两种鼠间的差异，以此探讨两种田鼠的进化机制与适应功能。两种田鼠的犁鼻器位于鼻腔前端鼻中隔基部的两侧，呈管状结构；沿着犁鼻器的长轴犁鼻管呈现不同的形态学特征，犁鼻管直接开口于鼻腔，从前向后沿着长轴旋转，中间管壁(犁鼻粘膜)变成底部，侧面管壁(假覆层上皮)变成犁鼻管顶壁，最终犁鼻管变小成为一个腺体的分支，不同部位具有不同的组织学特征。通过选取中间相似部位对两种田鼠进行比较研究，发现棕色田鼠犁鼻粘膜比沼泽田鼠厚，而其长度却短于沼泽田鼠。棕色田鼠副嗅球颗粒细胞带宽和僧帽细胞带宽均大于沼泽田鼠，而带长却小于沼泽田鼠。相关分析发现，犁鼻器和副嗅球形态有一定的对应关系，这可能和两个结构之间存在着神经投射有关。棕色田鼠幼体的犁鼻粘膜、神经细胞核、假覆层上皮、血管面积均小于成体[动物学报49(2)：248—255，2003]。     

Achiasmatic giant sex chromosomes in the vole Microtus cabrerae (Rodentia, Microtidae).

Conventional and microspread preparations of Microtus cabrerae spermatocytes were made to investigate the chromosomes of this species. Three different types of Y chromosomes, varying in size of the heterochromatic block, were observed; they were alike, however, in regard to synapsis, which was consistently absent. Our results suggest that the heterochromatic blocks are not involved in the lack of synapsis and that asynapsis is a cytological feature common to all species of the family Microtidae. In addition, the co-aligned configuration of the ends of the sex-chromosome axes of this species and the lack of silver-stainable threads or filaments connecting them suggest the existence of two mechanisms for association of the sex chromosomes during prophase I and metaphase I: attachment of the ends of both sex chromosome axes to the nuclear envelope and heterochromatin "stickiness."     

用C-带和涂染技术检测棕色田鼠Y染色体

采用染色体C 带技术和小鼠整条Y染色体特异探针检测棕色田鼠的Y染色体 ,结果如下 :棕色田鼠雄性个体C 带中期分裂相中 ,X性染色体是亚中部着丝粒染色体 ,在着丝粒处存在着强烈的C阳性带 ,而且在短臂的中间也有一条C阳性带 ,但是没有发现深染的Y染色体。用小鼠整条Y染色体特异探针涂染棕色田鼠的骨髓细胞中期分裂相和间期核 ,以小鼠骨髓细胞中期分裂相和间期核作为对照。涂染结果表明 :棕色田鼠骨髓细胞中期分裂相和间期核涂染信号检出率分别为 0 - 2 %和 3% - 5 % ,两者均呈阴性反应 ,而对照都呈阳性反应。根据实验结果 ,作者认为在棕色田鼠的Y染色体上及整个基因组DNA中不存在小鼠整条Y染色体特异DNA的同源序列 ,其Y染色体上可能没有决定雄性性别的重要基因     

口服莪术油抑制雌性棕色田鼠性行为和雌二醇受体在大脑核团中的表达

植物不育剂是由具有抗生育作用的天然植物中的提取物配制而成,用不育剂配制的混合饵料,不仅对雌雄鼠生殖机能均有一定的破坏性,起到了阻断生殖的作用,而且又不污染环境和破坏生态平衡(张春美等,2001),所以这类混合饵料称为绿色环保型抗生育鼠药(简称环保型鼠药).     

Metabolism and thermoregulation in the Cabrera vole (Rodentia: Microtus cabrerae)

Metabolism and thermoregulation were studied for the first time in the Cabrera vole (Microtus cabrerae), an endemic and threatened rodent of the Iberian Peninsula. Low values of resting metabolic rate (RMR) were registered (1.13 mlO(2) g(-1) h(-1)) at the lower limit of the thermoneutral zone (TNZ) (around 33.5 degrees C). Body temperature increased near the TNZ up to 37.3 degrees C but remained stable, around 36 degrees C, at ambient temperatures below 25 degrees C. Values of thermal conductance remained quite stable at ambient temperatures of 10-25 degrees C (0.144-0.160 mlO(2) g(-1) h(-1) degrees C) and increased to 0.301 mlO(2) g(-1) h(-1) degrees C at 33.5 degrees C. Data revealed that M. cabrerae developed a highly adaptive ability of conserving energy and lowering the metabolic cost of thermoregulation at high ambient temperatures, allowing the body temperature to approximate that of the environment and exhibiting low resting metabolic rate and high conductance.     

棕色田鼠消化道形态变化与能量需求的关系

为研究能量代谢与消化道形态结构变化及其某些生活史特征之间的关系，采用食物平衡法、耗氧量测定、形态测量和组织学方法，分别测定了雄性、非繁殖雌性及哺乳雌性棕色田鼠(Mirotus mandarinus)的摄食量、每日消化能、静止代谢率和胃肠器官长度、重量以及肠道各段管径和黏膜厚度。结果表明：哺乳雌鼠摄食量、每日消化能、静止代谢率高于非繁殖雌鼠和雄鼠，且消化道各器官有最大的重量、管径和黏膜厚度。由此可见，哺乳雌鼠能量需求增加，促使消化道形态结构进行一些有益的调节。棕色田鼠在哺乳期代谢率增加时，仅有消化道器官重量、黏膜厚度及小肠管径的明显变化，这可能与其哺乳期较长，胎仔数较少，生后生长缓慢等生活史特征有关。同时也说明在未受到十分严峻的能量胁迫的情况下，动物并不需付出昂贵的代价去增加消化器官的长度。     

Exclusion of Sall 4 as the sex-determining gene in the Mandarin vole Microtus mandarinus mandarinus

In previous studies, we have shown that the Sry HMG-box is absent in Microtus mandarinus mandarinus (M. m. mandarinus), suggesting that sex determination of M. m. mandarinus is independent of the Sry gene. We amplified a 312 bp fragment within exon 2 of the Sall4 gene in the mouse and M. m. mandarinus using polymerase chain reaction (PCR) and detected Sall4 using fluorescence in situ hybridization (FISH) technique. The probes for the Sall4 gene were labeled with digoxigenin using PCR and hybridized to chromosomes and interphase nuclei of the mouse and M. m. mandarinus. Our results suggested that Sall4 exists in the genome of male and female M. m. mandarinus, and the sequence within exon 2 of the gene is the same in the mouse and M. m. mandarinus. The results also showed that Sall4 is localized on chromosome 6 in M. m. mandarinus. As they are the sex chromosomes in M. m. mandarinus, the results excluded the Sall4 gene from being the testis-determining factor in this species. We propose that in M. m. mandarinus, sex determination is controlled by another yet unknown gene on the sex chromosomes.     

不同能量需求的棕色田鼠胃肠道一氧化氮合酶和血管活性肠肽的分布

为研究在能量需求变化的情况下生理功能调节在消化道适应性变化中的地位,并探讨生理调节与消化道形态结构适应性变化的关系,采用NADPH-黄递酶（NDP）组织化学法、VIP免疫组织化学法和整装铺片技术对哺乳和非哺乳雌性棕色田鼠及雄性棕色田鼠胃肠道管壁肌间神经丛和黏膜下神经丛一氧化氮合酶（Nitricoxidesynthase,NOS）和血管活性肠肽（Vasoactive intestinal peptide,VIP）阳性神经元的分布进行观察。结果显示：哺乳和非哺乳雌性棕色田鼠及雄性棕色田鼠NOs阳性神经元分布于肌间神经丛,VIP分布于黏膜下神经丛,未观察到共染现象。NOS和VIP阳性神经元在哺乳雌性棕色田鼠胃及小肠前段的肌间神经丛和黏膜下神经丛的分布显著高于非哺乳雌鼠和雄鼠,而在回肠、盲肠和结肠差异不显著。由此说明,不同繁殖状态下,能量需求的不同促使消化道发生适应性变化,首先是生理功能及其调节机制的变化。同时提示消化道适应策略与消化道各段生理功能及能量胁迫程度有关[动物学报51（5）：830—839,2005]。     

棕色田鼠对熟悉和陌生异性尿液的识别

本文通过直接接触和非直接接触尿液的方式,探讨了棕色田鼠尿液中挥发性和非挥发性成分在气味识别中的作用。结果表明:在直接接触的情况下,棕色田鼠对熟悉异性鼠的尿液表现出明显的选择倾向;在非接触情况下这种倾向不明显;雌雄棕色田鼠在非接触情况下共处后,在直接接触尿液时,雌雄鼠都对异性熟悉鼠的尿液表现出明显的选择倾向。通过实验发现:棕色田鼠不但能够在直接接触的情况下识别熟悉和陌生异性鼠尿液,而且能够通过感知个体产生的挥发性化学物质而对陌生的异性个体形成记忆,在以后通过其尿液对其进行识别,而在此过程中尿液中非挥发性成分可能也起着一定作用。     

The Iranian vole Microtus irani occurs in Lebanon (Mammalia: Rodentia)

We studied 1140 bp cytochrome b sequences of social voles from three localities in Lebanon. The results were compared with published sequences representing seven species of social voles. New sequences from Lebanon clustered with reference samples of two species: M. guentheri and M. irani. While M. guentheri was already reported for Lebanon, M. irani is a new addition to the fauna of Lebanon, and the third known record for the species. Animals were collected in two localities above Tripolis at 855 m and 1430 m a.s.l., respectively.     

Morphological variation in root vole Microtus oeconomus pallas (Rodentia, Arvicolidae) in the Baikal region

Morphological variation in root vole was studied in 10 samples from the Baikal islands and shore regions. The island samples differed from the continental ones by a set of cranial characters as well as by a higher complexity and asymmetry of morphotypes of the third upper molar. A possible role of biotopic and microclimatic conditions in the formation of a specific morphological pattern of island micropopulations of this species is discussed.     

Parental responsiveness negatively correlates with fecal testosterone concentration in male mandarin voles (Microtus mandarinus)

The tradeoff between parental effort and mating effort in male animals may be mediated by testosterone (T). The pattern of association between T and paternal care in birds is consistent with this hypothesis, while it is poorly studied and not universal for mammals. We used the correlation approach to test two predictions of T-mediated tradeoff hypothesis for a biparental vole, Microtus mandarinus: (1) that T levels in males decrease from before pair formation to after birth of the first litter and (2) that paternal responsiveness of males negatively correlates with their T levels. T concentrations were measured in fecal samples collected before pairing and then immediately before behavioral testing on day 5 after birth of the first litter. Both nonpaternal and low paternal males had high initial T that decreased after birth of pups, though the decrease was only significant in low paternal males. In highly paternal males, the initial T was low and did not change after birth. Our results support the predictions of T-mediated tradeoff hypothesis and reveal individual variation in hormone–behavior relationship.     

Mating behavior induces changes of expression of Fos protein,plasma testosterone and androgen receptors in the accessory olfactory bulb (AOB) of the male mandarin vole Microtus mandarinus

In order to investigate the neuroendocrine mechanism of the mating behavior in the adult male mandarin voles Microtus mandarinus,the radioimmunoassay(RIA)and immunohistochemistry methods were used to investigate the differences in plasma testosterone(T)concentrations and distribution of T immunoreactive neurons(T-IRs),androgen receptor immunoreactive neurons(AR-IRs)and Fos protein immunoreactive neurons(Fos-IRs)in the accessory olfactory bulb(AOB)and the main olfactory bulb(MOB)following exposure to clean h...     

Simple GA C T A repeats characterize the X chromosomal heterochromatin of Microtus agrestis,European field vole (Rodentia,Cricetidae)

The sex chromosomes of Microtus agrestis are extremely large due to the accumulation of constitutive heterochromatin. We have identified two prominent satellite bands of 2.0 and 2.8 kb in length after HaeIII and HinfI restriction enzyme digestion of genomic DNA, respectively. These satellites are located on the heterochromatic long arm of the X chromosome as shown using Microtus x mouse somatic cell hybrids. By in-gel hybridization with oligonucleotide probes, the organization of the two satellites was studied: among the many copies of the simple tandem tetranucleotide repeat GATA are interspersed rare single GACA tetramers. One of the satellites also harbours related GGAT simple tandem repeats. In situ hybridizations with plasmid-carried or oligonucleotide GA _C ^T A probes show clustered silver grains on the long and short arm of the X chromosome. Interspersion of differently organized (GATA)_n elements is also demonstrable in the autosomal complement and on the Y chromosome. These results are discussed in the context of the evolution of vertebrate sex chromosomes in relation to heterochromatin and simple repetitive DNA sequences.