Long-term persistence of Anaplasma phagocytophilum and Ehrlichia muris in wild rodents

Wild animals are reservoir hosts for a number of tick-transmitted agents, and long-term persistence of the agents is a key factor for their effective transmission from animal hosts to ticks. To study the persistence of Anaplasmataceae in rodents, 59 adult Myodes spp. voles (M. rutilus, M. rufocanus, and M. glareolus) were captured in Omsk Province, Asian Russia, freed from all ectoparasites, and kept in individual cages. Their blood samples were regularly analyzed for the presence of DNA of Anaplasma phagocytophilum, Ehrlichia muris, and “Candidatus Neoehrlichia mikurensis”. Anaplasma phagocytophilum, E. muris, and mixed infections were found in 29 (49 %), 17 (29 %), and 14 (24 %) voles, respectively. DNA of “Candidatus N. mikurensis” was not identified. Long-term persistence of A. phagocytophilum and E. muris in naturally infected Myodes spp. was shown for the first time. Thus, 12 animals with A. phagocytophilum were found infected for more than three months and four of them carried the bacterium throughout 22–55 weeks of observation. Four voles were infected with E. muris for 26–40 weeks. Fragments of groESL operon were sequenced for genotyping A. phagocytophilum and E. muris. In voles with A. phagocytophilum, the determined sequences belonged to two phylogenetic clusters. Most sequences were identical or closely related to those found in small mammals and Ixodes trianguliceps ticks from Western Siberia and European countries; one sequence was previously identified in rodents and Ixodes persulcatus and Ixodes pavlovskyi ticks from Asian Russia. Sequences of groESL fragments from E. muris were close to those determined previously in small mammals and I. persulcatus ticks from Siberia. In addition, a new groESL sequence of E. muris was identified in one vole and the sequence substantially differed from all known corresponding E. muris sequences (≥ 14 mismatches).     

Dose- and photoperiod-dependent effects of 17beta-estradiol and the anti-estrogen ICI 182,780 on testicular structure, acceleration of spermatogenesis, and aromatase immunoexpression in immature bank voles

It has been known that administration of estrogens or deficiency of estrogens can affect development and/or maintenance of male gonadal functions. These hormones are able to control germ cell development, and especially spermatid production and epididymis sperm maturation. The aim of the present study was to show the effects of 17beta-estradiol and a pure anti-estrogen, ICI 182,780, on the bank vole testis. Immature bank voles reared under either short or long light cycles were injected intraperitoneally with two doses of either 17beta-estradiol (0.1 and 10 microg/g body weight, respectively) or pure anti-estrogen ICI 182,780 (10 and 100 microg/g body weight, respectively) both dissolved in 20 microl sesame oil. Control groups (from both photoperiods) received 20 microl sesame oil only. The injections were performed twice a week during 2 weeks. Exposure to the low dose of estradiol induced acceleration of the onset of spermatogenesis. This was particularly apparent in voles kept under short light cycle conditions. On the other hand, when males were treated with a high dose of estradiol or ICI 182,780, disruption of testicular structure and tubular atrophy were observed. Increased apoptosis of germ cells was evident. It is concluded that bank voles as seasonally breeding animals are a useful model for studying the role of estrogens in structure and function of the testis.     

Histopathological changes in the liver, kidneys, and testes of bank voles environmentally exposed to heavy metal emissions from the steelworks and zinc smelter in Poland

Bank voles were trapped in the neighborhood of the Sendzimir steelworks in Krakow and the ZGH Boleslaw zinc smelter in Bukowno. The Borecka forest in the north of Poland served as a control area. Lead, cadmium, zinc, and iron concentrations were analyzed in the liver, kidneys, testes, and femur bones of the bank voles. Typically, high levels of lead and cadmium were found in the bones and kidneys, respectively. In the femurs of the rodents from Bukowno, 109.26 microg g(-1) dry weight of lead was detected. The kidneys of these animals had accumulated 32.98 microg g(-1) cadmium. Concentrations of zinc and iron in the tissues were at physiological levels. No damage was found in the tissues of the bank voles from the Borecka forest or in the testes of animals from other areas. Histopathological changes in the kidneys of the rodents from Krakow as well as changes to the liver and kidneys of the animals from Bukowno were demonstrated.     

两个不同地区东方田鼠杂交子代RAPD标记分析

目的研究不同地区东方田鼠杂交后产下的子代的遗传特性.方法筛选4条10bp随机引物对宁夏和洞庭湖地区东方田鼠杂交子代的基因组进行随机扩增多态DNA(RAPD)分析,并对不同地区亲代以及子代相互之间的基因组DNA进行相似性分析.结果①所有东方田鼠均有相同的扩增片段出现;②两个不同地区的亲代分别有特异性片般;③亲代的DNA带型均能在子代中找到;④同一胎次东方田鼠之间基因共享度大约在72%～96%之间.结论RAPD分析能在一定程度上反映出东方田鼠种的特性以及亚种的特异性,而且同一胎次之间基因共享度较高.     

Immunoreactivity of central vasopressin and oxytocin pathways in microtine rodents: A quantitative comparative study

The genus Microtus includes several closely related species of voles with diverse patterns of social organization. Comparative studies of these species have previously tested hypotheses related to the evolution of monogamy and affiliation. In earlier studies, monogamous voles have been reported to differ from closely related nonmonogamous voles in the neural distribution of oxytocin and vasopressin receptors. These receptors have also been implicated in the behavioral differences relevant to monogamy, as oxytocin and vasopressin influence pair-bond formation in the monogamous species. In the current study, two monogamous and two nonmonogamous vole species were compared for the distribution of oxytocin and vasopressin immunoreactivity. Contrary to our predictions, gender dimorphisms in vasopressin immunoreactivity were as evident in the monogamous as in the nonmonogamous species. Also, species differences in oxytocin and vasopressin staining were subtle relative to the profound species differences previously reported for receptor binding. These results are consistent with the hypothesis that neuroendocrine systems may evolve by changes in receptor distribution rather than by restructuring the presynaptic pathway. © 1996 Wiley-Liss, Inc.     

Neuroendocrine and behavioural responses to exposure to an infant in male prairie voles

Paternal behaviour and pair‐bond formation are defining characteristics of social monogamy. However, in comparison to pair‐bonding, the endocrine factors associated with the male care of young are not well studied. In the present study, plasma concentrations of oxytocin, vasopressin and corticosterone (CORT) were measured in reproductively naïve male prairie voles as a function of exposure to an infant or control manipulations (i.e. handling or exposure to a wooden dowel). Plasma oxytocin concentrations were transiently elevated within 10 min of pup exposure. Although plasma CORT concentration typically increases after handling, after 10 min of pup exposure, the concentration of plasma CORT was not increased, suggesting an attenuation of CORT release by pup exposure. Group differences in the concentrations of plasma hormones were no longer detected at 20 or 60 min after treatment. These patterns of rapid change in the concentrations of plasma oxytocin and CORT were observed in both juvenile and adult males but not detected after control procedures. Plasma vasopressin, assessed only in adult males, did not vary as a function of pup exposure or other manipulations. In the paraventricular nucleus of the hypothalamus, pup exposure also increased activation (as assessed by the measurement of c‐Fos) of neurones that stained for either oxytocin or vasopressin, whereas it decreased c‐Fos expression in neurones stained for corticotrophin‐releasing hormone. In addition, brief pup exposure (20 min) facilitated subsequent partner preference formation when alloparental males and pup attackers were considered as a group. In the context of other studies, these data support the hypothesis that neuroendocrine changes associated with male alloparental behaviour are related to those implicated in pair‐bonding.     

The neurobiology of social recognition, approach, and avoidance.

Rodent models of social behavior provide powerful experimental tools for elucidating the molecular, cellular, and neurobiological mechanisms regulating social behavior. Here I discuss several rodent models that have been particularly useful in understanding the neurobiology of the discrimination of social verses nonsocial stimuli, affiliative behavior, and social avoidance. The oxytocin knockout mouse model has been useful for understanding how, in the context of social recognition, the brain may process social stimuli differently from nonsocial stimuli. Vole species that are either highly social and monogamous or solitary and promiscuous have provided a model for investigating the brain mechanisms involved in promoting social interactions. Comparative studies in these species strongly implicate the neuropeptides oxytocin and vasopressin in the regulation of affiliative behavior as well as social attachment. A conditioned defeat model in hamsters may provide a useful model to understand how adverse social experiences may facilitate social avoidance. These models have yielded valuable insights into the regulation of social behaviors, and the findings of these studies may prove useful in understanding the neural mechanisms that underlie individual differences in human personality traits.     

Androgenic and Oestrogenic Influences on Tyrosine Hydroxylase‐Immunoreactive Cells of the Prairie Vole Medial Amygdala and Bed Nucleus of the Stria Terminalis

The posterodorsal medial amygdala (MeApd) and principal nucleus of the bed nucleus of the stria terminalis (pBST) are densely interconnected sites integrating steroid hormone and olfactory information necessary for sociosexual behaviours in many rodents. Our laboratory recently reported sexually dimorphic populations of cells containing tyrosine hydroxylase (TH) located in the MeApd and pBST of prairie voles (Microtus ochrogaster), with males having many more TH‐immunoreactive (‐ir) cells in these sites than do females. Gonadal hormones circulating during adulthood were showm to regulate this sex difference because it was eliminated by castrating adult males or implanting females with testosterone‐filled capsules. In the present study, we demonstrate that many (25–65%) TH‐ir cells in the MeApd and pBST of adult virgin male and female prairie voles also contain immunoreactivity for either the androgen receptor or oestrogen receptor α. Subcutaneous implants of oestradiol benzoate mimicked the effects of testosterone and maintained high numbers of TH‐ir cells in these sites in castrated males. However, implants of dihydrotestosterone (DHT) did not, and these males had low numbers of TH‐ir cells similar to castrated males given empty capsules. A similar effect was found in females, where testosterone or oestradiol benzoate greatly increased the number of TH‐ir cells in these sites compared to intact or ovariectomised controls, but DHT did not. DHT implants did, however, maintain high seminal vesicle weights in males. Thus, many of the TH‐ir cells in the prairie vole MeApd and pBST are potentially sensitive to androgens and oestrogens, although maintaining immunocytochemically detectable levels of TH in these cells may depend more on an oestrogen‐mediated mechanism in both sexes. These data have implications for understanding how gonadal hormone release across the reproductive cycle modulates these species‐specific groups of catecholaminergic cells and socially monogamous behaviours in prairie voles.