Genes for the SMC Family Proteins in a Common Vole Microtus arvalis

Genes for four subfamilies of SMC (structural maintenance of chromosomes) proteins have been isolated from the genome of a common vole Microtus arvalis. The high degree of homology between representatives of each SMC protein subfamily of different classes of organisms has been demonstrated. The full-sized copy of a mammalian gene encoding SMC4 protein has been isolated and analyzed for the first time. The SMC proteins enter into the composition of complexes responsible for cohesion of sister chromatids, formation of mitotic chromosomes, recombination, DNA repair, and regulation of gene expression. We discuss the possible participation of the SMC proteins in inactivation of the X chromosome in mammalian females. Common voles of genus Microtusgroup arvalis serve a unique model for the study of the inactivation process.     

Behavioral Responses to Combinations of Timed Light,Food Availability,and Ultradian Rhythms in the Common Vole (Microtus arvalis)

Light is the main entraining signal of the central circadian clock, which drives circadian organization of activity. When food is made available during only certain parts of the day, it can entrain the clock in the liver without changing the phase of the central circadian clock. Although a hallmark of food entrainment is a behavioral anticipation of food availability, the extent of behavioral alterations in response to food availability has not been fully characterized. The authors have investigated interactions between light and temporal food availability in the timing of activity in the common vole. Temporally restricted food availability enhanced or attenuated re-entrainment to a phase advance in light entrainment when it was shifted together with the light or remained at the same time of day, respectively. When light-entrained behavior was challenged with temporal food availability cycles with a different period, two distinct activity components were observed. More so, the present data indicate that in the presence of cycles of different period length of food and light, an activity component emerged that appeared to be driven by a free-running (light-entrainable) clock. Because the authors have previously shown that in the common vole altering activity through running-wheel availability can alter the effectiveness of food availability to entrain the clock in the liver, the authors included running-wheel availability as a parameter that alters the circadian/ultradian balance in activity. In the current protocols, running-wheel availability enhanced the entraining potential of both light and food availability in a differential way. The data presented here show that in the vole activity is a complex of individually driven components and that this activity is, itself, an important modulator of the effectiveness of entraining signals such as light and food. (Author correspondence: vanderveen@nd.edu)     

Characteristics of tear proteins in the vole, Microtus arvalis

Tear proteins were detected by polyacrylamide gel electrophoresis in the vole, Microtus arvalis. The tear proteins were separated to 6 to 8 bands and the bands were divided to three regions on the anodic side. In the adult male vole, a male specific band (Vtp-1) was detected in the first region. The first region of adult female and immature voles contained two specific bands (Vtp-2, 3). In the castrated adult males or adult males injected with estrogen, the male specific hand, Vtp-1, disappeared and Vtp-2 and 3 bands appeared. In all castrated voles, the Vtp-1 band appeared and Vtp-2 and 3 bands disappeared after the administration of testosterone. Thus, sex hormone-dependent proteins are present in vole tears.     

Islands and the evolution of Microtus arvalis (Microtinae)

The widespread European vole species Microtus arvalis (Pallas) occurs in the British Isles only on Guernsey and various of the Orkney islands. The traditional explanation for this peculiar distribution has been that the island races are the sole relicts of a previously cosmopolitan form. This idea is not supported by the present study, in which population samples are compared with voles from a number of localities from Continental Europe. Using the frequencies of non-metrical skull variants as genetical markers, it emerged that although the Guernsey population ( Microtus arvalis sarnius ) was virtually indistinguishable from typical German specimens, and therefore likely to be a relict from the time when Guernsey was connected to France, the Orkney populations ( Microtus arvalis orcadensis ) formed a distinct group with affinities more to south Europe than elsewhere. It seems probable that arvalis was brought to Orkney by some of the earliest human colonizers about 4000 years ago, and then radiated to the different islands. It is argued that this manner of peripheral differentiation may be an important method of evolutionary change.     

Effect of Deficiency of Dietary Nitrogen on Cellulose Digestibility and Nitrogen-Fixing Flora Activity in Sibling Vole Microtus rossiaemeridionalis

The effect of feed composition on nitrogen-fixing activity of the symbionts living in the digestive tract of sibling vole Microtus rossiaemeridionalis was experimentally studied. In the control, the rodents were allowed to select any of three feeds: protein-rich, protein-free with low cellulose content, and protein-free with high cellulose content. The voles consumed the food in a proportion corresponding to 16% of protein and about 6% of cellulose. Exclusion of the protein-rich food considerably increased cellulose consumption (up to 12%) and digestibility (from 35 to 64%). The changes in the consumed feed composition were reflected in localization of nitrogenase activity in the digestive tract: the control level of nitrogen-fixing activity in the cecum was three times that in the proventriculus, while an inverse proportion was observed in the experimental groups. In all cases, the colon was the major locus of nitrogen fixation.     

湖南等三地区东方田鼠遗传特性的分析比较

用染色体G带核型分析、生化位点、随机扩增多态性DNA(RAPD)标记等方法,对湖南洞庭湖湖滨、宁夏青铜峡市农田和黑龙江伊春市金山屯草甸3个地区的东方田鼠遗传特性进行了分析。结果表明,湖南和宁夏地区东方田鼠染色体数均为2N＝52,黑龙江东方田鼠染色体数则为2N＝42;生化位点结果显示3个地区的东方田鼠均呈遗传非均一性;湖南、宁夏和黑龙江鼠的个体间RAPD遗传距离分别为0．244（0．143—0．353)、0．226(0．161—0．294)、0．541(0.357—0．692)。湖南和宁夏两地区鼠种群间的遗传距离为0．367,湖南和宁夏鼠杂交一代与其亲代的RAPD遗传距离在0．310以下;但黑龙江鼠与湖南和宁夏鼠种群问的遗传距离分别为0．619和0．633。总的表明,3个地区的东方田鼠均呈遗传非均一性,但湖南与宁夏鼠在染色体、生化位点和RAPD标记等方面都具有相似性,并可杂交,而黑龙江鼠与其它两地的鼠不能杂交,且黑龙江鼠在遗传特性方面与前二地鼠有很大差异,因而后的“种”级分类地位值得进一步研究。     

Seasonal variation in the activity patterns of the Orkney vole Microtus arvalis orcadensis

In captivity, Orkney voles Microtus uruulis orcudensis show an activity pattern that consists of regularly alternating periods of rest and activity with a periodicity of about 2.8 hours. Captive voles kept under ambient conditions are equally active day and night at all times of the year. Free-living voles also show a regular short-term rhythm of activity but in addition the partition of activity between day and night varies seasonally. At two sites on Orkney Mainland cyclic variation in diurnality with a period of 12 months were recorded. Although surface activity occurred during both the day and night throughout the year, day activity predominated, particularly during the winter months. The cycle appeared to be synchronous at the two study sites.
Seasonal variation in diurnality appeared to be associated with population density and due largely to the proportion of juveniles in the population. Given the 12-month cycle of diurnality found in the Orkney vole, phase relationships with photoperiod are likely to be consistent between years. This may explain why populations of this subspecies do not appear to undergo multi-annual population cycles.
Despite intense levels of predation by raptors, including the short-eared owl which switches between nocturnal and diurnal hunting, Orkney voles exhibit a relatively simple and highly predictable cycle of diurnality. This cycle is unlikely therefore to have evolved as a means of preventing predator specialization with respect to time of day, season or year.     

Intrapopulation autosomal polymorphism in the common vole Microtus arvalis from the Transcaucasian region

The broad autosomal polymorphism in form obscurus of common voles Microtus arvalis from the Transcaucasian region that is associated with the variation of subtelocentric chromosome pair 5, as well as the mechanism and evolutionary significance of this polymorphism, are discussed. Based on the morphological analysis of heterozygotes for chromosome pair 5 after differential G-, C-, and Ag-NOR-banding and on the measurements of homologues, the following conclusion has been made. The occurrence of the acrocentric chromosome 5 is the result of a double chromosomal rearrangement: a pericentric inversion and a duplication of the chromosomal material. The mutation has been found throughout the entire territory of Armenia. In spite of such a wide distribution, the mutation frequency in populations is extremely low. Neither a definite pattern of geographic distribution nor a clinal variation was found for this mutation. This mutation is likely to occur independently in different M. arvalis populations and is apparently neutral. Homozygotes for chromosome pair 5 are described for the first time.     

Functional morphology of the ear in fossorial rodents, Microtus arvalis and Arvicola terrestris

Functionally relevant features and parameters of the outer, middle, and inner ear were studied morphologically and morphometrically in two species of voles, smaller Microtus arvalis and larger Arvicola terrestris. The findings in these fossorial (i.e., burrowing) rodents with components of surface activity were compared with respective findings reported for taxonomically related muroid rodents representing the same size classes but different eco-morphotypes: obligate subterranean rodents (Ellobius talpinus and Spalax ehrenbergi superspecies) and generalized rodents (Mus domesticus and Rattus norvegicus). The ear in voles was characterized by traits reported for subterranean rodents. The eardrum was round, without a distinct pars flaccida, and had an area of 5.4 mm2 in M. arvalis and 9 mm2 in A. terrestris. The middle ear exhibited reduced goniale, enlarged incus nearly parallel to the manubrium of the malleus. The malleus-incus lever ratio amounted to 2.1 (M. arvalis) and 2.0 (A. terrestris). The malleus-incus complex weighed about 0.8 mg in both vole species. The stapedial footplate had an area of 0.3 mm2 in M. arvalis and 0.4 mm2 in A. terrestris. The cochlea had 2.3 coils in both vole species; the basilar membrane was 8.5 mm and 10.5 mm long in M. arvalis and A. terrestris, respectively. There were on average 1,030 (M. arvalis) and 1,220 (A. terrestris) inner hair cells, and 3,760 (M. arvalis) and 4,250 (A. terrestris) outer hair cells in the organ of Corti. In quantitative terms, all these (as well as some further) traits and parameters were intermediate (related to body size) between those reported for generalized rodents on the one hand and subterranean ones on the other. The sound transmission system of the ear seems to be best tuned to frequencies of about 8-16 kHz with a high-frequency cut-off at about 50-60 kHz. The ear of A. terrestris seems to be tuned to somewhat lower frequencies than that in M. arvalis. In this aspect as well as regarding hearing sensitivity (as judged from the mechanical transmission parameters), voles can be considered intermediate not only in their lifestyle but also in their hearing abilities between the subterranean rodents (mole-vole and blind mole-rat) and the surface dwellers (house mouse and Norway rat).     

Polymorphic microsatellite loci and PCR multiplexing in the common vole,Microtus arvalis

We isolated and characterized 14 dinucleotide microsatellite loci in the common vole Microtus arvalis (Palas). Two multiplex panels both comprising seven loci were developed. Application to a set of 21 individuals allowed clear and easy characterization of allele sizes except for two loci which were then withdrawn from further analyses. The number of alleles ranged from four to 19 per locus with the observed heterozygosity ranging from 0.55 to 0.95. These sets of microsatellite loci provide high throughput capacity for population genetic studies at a minimum cost.     

Mating System and Population Fluctuations of the Prairie Vole, Microtus ochrogaster

The basic mating system of the prairie vole, Microtus ochrogaster,consists of monogamous breeding units comprised of one reproductivefemale and male and their offspring. Most surviving young remainat the natal nest; those that do so normally remain non-reproductive.Of 281 total breeding units monitored in free-living populations50.2% were monogamous. Twenty-seven percent consisted of a singlereproductive female that apparently has lost her mate. Theremaining22.8% of the breeding units included two or more unrelated adultsmales and/or females (=‘complex’ breeding units).In general, monogamy was the predominant type of breeding unitat the highest (>100 adults/ha) as well as at low (>20adults/ha) population densities. There was no consistent relationshipbetween the number of residents of a breeding unit and populationdensity. Significantly more young females remaining at the natalnest became reproductive at high rather than at low populationdensities (77.1 and 17.6%, respectively). Monogamy was prevalentduring the winter as well as during the other seasons; however,there were significantly more complex breeding units duringthe winter than during other seasons. Breeding unit size wassignificantly larger during the winter than at other seasons.There was no difference in the proportions of breeding unittypes or the number of residents of a breeding unit during breedingand nonbreeding seasons. Increased breeding unit size appearsrelated to low temperatures and associated physiological stressesduring the winter rather than to population density.     

根田鼠身体大小的性二型

在雌雄异体的有性生物中 ,反映身体结构和功能特征的某些变量在两性之间常常出现固有的和明显的差别 ,使得人们能够以此为根据判断一个个体的性别 ,这种现象被称为性二型 (ｓｅｘｕａｌｄｉｍｏｒ ｐｈｉｓｍ)。国外大量研究表明 ,哺乳动物性二型现象十分普遍 ,并且 ,在大多数情况下 ,雄性个体大于雌性个体[1] ;国内同类研究还不多 ,仅见周立等[2 ] 、盛和林[3] 、陈国芳[4 ] 、杜铭章[5] 分别对高原鼠兔(Ｏｃｈｏｔｏｎａｃｕｒｚｏｎｉａｅ)、黄鼬 (Ｍｕｓｔｅｌａｓｉｂｉｒｉｃａ)、摇蚊和海蛇的性二型现象作过报道 ,但均未分析其产生原…     

Gene for structural proteins of the SMC family in the common vole Microtus arvalis]

Genes for four subfamilies of SMC (structural maintenance of chromosomes) proteins have been isolated from the genome of a common vole Microtus arvalis. The high degree of homology between representatives of each SMC protein subfamily of different classes of organisms has been demonstrated. The full-sized copy of a mammalian gene encoding SMC4 protein has been isolated and analyzed for the first time. The SMC proteins enter into the composition of complexes responsible for cohesion of sister chromatids, formation of mitotic chromosomes, recombination, DNA repair, and regulation of gene expression. We discuss the possible participation of the SMC proteins in inactivation of the X chromosome in mammalian females. Common voles of genus Microtus group "arvalis" serve a unique model for the study of the inactivation process.     

Unusual heteromorphic bivalents in the common vole (Microtus arvalis) from Belorussia.

Electron microscopic analysis was carried out on the synaptonemal complexes of 10 male common voles (Microtus arvalis) caught in 1990 in Belorussia. In the early pachytene stage of spermatocytes of four males, a heteromorphic bivalent has been found in one of five large autosomes. In the central region of the bivalent one of the lateral elements is in the form of a D-loop, characteristic of insertion/deletion heterozygotes. However, high-resolution G-band staining of mitotic chromosomes from fibroblasts shows no significant differences in the G-band pattern between homologs.