Aspiculuris tetraptera in wild Mus musculus. Age resistance and acquired immunity.

Wild house mice, naturally infected with Aspiculuris tetraptera were segregated according to their weight into six age groups. The prevalence of infection and the mean worm burden of these mice were studied in the different age groups. The overall prevalence of infection was high (57% or more) in all the groups except the youngest. Mice acquired larvae soon after weaning; the highest larval burdens were reached in juvenile mice and the highest mature worm burdens, a group later, in mature mice. Older mice had fewer larvae and fewer mature worms. The mature worm burdens decreased but relatively slower than the larval burdens. It is suggested that eigher innate or acquired resistance could account for these observations.     

Suppression of expulsion of Aspiculuris tetraptera in hydrocortisone and methotrexate treated mice.

Hydrocortisone treated male and female mice, given a primary infection with Aspiculuris tetraptera, did not reject the worms during the third week of infection. Mice given hydrocortisone during the first week of infection had elevated worm burdens on day 10, suggesting that some worm loss was encountered during the anterior migration in control mice. Furthermore, this temporary period of treatment was sufficient totally to suppress rejection and to allow the parasite to persist until day 28. Methotrexate also significantly delayed rejection, but larval growth was retarded in treated mice. These results, it is suggested, add strength to the hypothesis that the loss of A. tetraptera in a primary infection in mice, is an immunological phenomenon.     

Measures of immune function of wild mice, Mus musculus

The immune function of wild animals has been rather little studied. Wild animals' immune function may differ from that of laboratory bred animals because of their different environments. This idea follows from the concept of resource partitioning in which animals distribute scarce resources to all aspects of life, including to costly immune responses. A logical extension of this idea is that there may be substantial interindividual variation in the immune function of wild animals. To begin to investigate this, we compared the immune function of a laboratory bred mouse strain (C57BL/6, a widely used mouse strain that makes potent immune responses) and wild caught Mus musculus. We found that by most measures of immune function, the wild caught mice had greater immune function. Specifically, wild mice had greater concentrations and more avid antigen-specific IgG responses, as well as higher concentrations of total IgG and IgE, compared with those laboratory bred mice. Moreover, flow cytometric analysis showed a comparatively greater overall level of activation of the cells of the immune system in wild mice. Lastly, we observed that immune function was substantially more variable among wild caught mice than among the laboratory bred mice. The next research challenge is to understand which aspects of an individual animal's life determine its immune function.     

Patterns of infection with the nematodes Syphacia obvelata and Aspiculuris tetraptera in conventionally maintained laboratory mice

Data on the frequency, distribution and mean intensity of the helminth fauna recovered from outbred and inbred mice conventionally maintained in Brazilian animal houses, are reported. The oxyurid nematodes Syphacia obvelata and Aspiculuris tetraptera presented overall frequencies of 91.5% and 8.5%, respectively. The frequency of S. obvelata in animals of three groups out of the four investigated ranged from 9% to 74% and A. tetraptera from 17% to 83%, since animals of one of the groups were negative for helminths. Infections due to a single species were observed in 62% of the animals, compared to 16% related to associations. The frequency of single infections in each group varied from 58.6% to 100% whereas associations varied from 24.1% to 41.4%. The analysis of specific mean intensities showed that S. obvelata was represented by 13.35 to 66.58 specimens/host and A. tetraptera by 5.85 to 16.75 specimens/host.     

Effects of cold on nest-building by wild and domestic mice, Mus musculus L.

Nest-building by male and virgin female wild and laboratory mice kept at a temperature of 2^o C was compared with that of controls kept at 23^o C. The amount of cotton wool pulled into the cage was recorded over 24 hours. Nest quality was also assessed. The tests of nest-building were conducted in both cold and warm environments. Cotton pulling was usually at a lower rate in the cold environment, but there was no corresponding decrement in final nest quality. Previous experience in the cold, compared with absence of such experience, resulted in higher scores by wild mice tested in either environment, and by laboratory mice tested in the cold environment. Wild mice that built high quality nests used less cotton wool in the cold than in the warm environment. The tendency for wild mice to pull more cotton wool and build better nests than laboratory mice was more pronounced among cold-treated animals. Differences in body weight did not account for the differences between wild and laboratory mice.
In further experiments nest-building was observed over 16 days. In the cold environment there was an initial depression of nest-building by both wild and laboratory mice, followed by a steady improvement over 6 days.
Both males and virgin females sometimes made well constructed nests even in the warm environment. In the cold environment the effect of previous cold-exposure on wild mice was the rapid construction of a good nest.     

Cryptosporidium tyzzeri and Cryptosporidium muris originated from wild West-European house mice (Mus musculus domesticus) and East-European house mice (Mus musculus musculus) are non-infectious for pigs

Three and 8 week old pigs were inoculated with Cryptosporidium muris HZ206 (Mus musculus musculus isolate), Cryptosporidium tyzerri CR2090 (M. m. musculus isolate) or C. tyzzeri CR4293 (isolate from a hybrid between Mus musculus domesticus and M. m. musculus) at a dose of 1 × 10(7) oocysts per animal. Inoculated pigs showed no detectable infection and no clinical symptoms of cryptosporidiosis during 30 days post infection (DPI), and no macroscopic changes were detected in the digestive tract following necropsy. Developmental stages were not detected in gastrointestinal tract tissue by histology or PCR throughout the duration of the experiment. The infectivity of isolates was verified on SCID mice, in which oocysts shedding started from 4 to 8 DPI. Based on our findings, it can be concluded that pigs are not susceptible to C. muris or C. tyzzeri infection.     

Testosterone rapidly reduces anxiety in male house mice (Mus musculus)

Eight experiments supported the hypotheses that reflexive testosterone release by male mice during sexual encounters reduces male anxiety (operationally defined in terms of behavior on an elevated plus-maze) and that this anxiolysis is mediated by the conversion of testosterone to neurosteroids that interact with GABA(A) receptors. In Experiment 1, a 10-min exposure to opposite-sex conspecifics significantly reduced both male and female anxiety 20 min later (as indexed by increased open-arm time on an elevated plus-maze) compared to control mice not receiving this exposure. In contrast, locomotor activity (as indexed by enclosed-arm entries on the elevated plus-maze) was not significantly affected. The remaining experiments examined only male behavior. In Experiment 2, exposure to female urine alone was anxiolytic while locomotor activity was not significantly affected. Thus, urinary pheromones of female mice likely initiated the events leading to the male anxiolysis. In phase 1 of Experiment 3, sc injections of 500 microg of testosterone significantly reduced anxiety 30 min later while locomotor activity was not significantly affected. Thus, testosterone elevations were associated with reduced male anxiety and the time course consistent with a nongenomic, or very rapid genomic, mechanism of testosterone action. In phase 2 of Experiment 3, the anxiolytic effect of testosterone was dose dependent with a 250 microg sc injection required. Thus, testosterone levels likely must be well above baseline levels (i.e., in the range induced by pulsatile release) in order to induce anxiolysis. In Experiment 4, a high dosage of 5alpha-dihydrotestosterone was more anxiolytic than a high dosage of estradiol benzoate, suggesting that testosterone action may require 5alpha-reduction. In Experiments 5 and 6, 3alpha,5alpha-reduced neurosteroid metabolites of testosterone (androsterone and 3alpha-androstandione) were both anxiolytic at a lower dosage (100 microg/sc injection) than testosterone, supporting the notion that testosterone is converted into neurosteroid metabolites for anxiolytic activity. Experiments 7 and 8 found that either picrotoxin or bicucculine, noncompetitive and competitive antagonists of the GABA(A) receptor, respectively, blocked the anxiolytic effects of testosterone. However, conclusions from these 2 experiments must be tempered by the reduction in locomotor activity that was also seen. The possible brain locations of testosterone action as well as the possible adaptive significance of this anxiolytic response are discussed.     

Social domination and reproductive success in male laboratory mice (Mus musculus)

The task of the present study was to evaluate effect of social status and of genotype on success of reproduction of male laboratory mice with use of ethological model of social hierarchy of “minimal socium”. The model represents the paired maintenance of two male mice of different genotypes (PT and CBA/Lac). The mice resided for 30 days in one experimental cage and established between them the dominant-subordinant relations. After this, each pair of males was supplemented by two DD/He females. Regardless of their genotype, the dominants became fathers more often than the subordinants and left more offspring. It has been established that the complete suppression of fertility did not occur. It is suggested that this allows them to make genetic contribution to the next generation and to remain in the genetic pool of population.     

Aggressive behaviour in related and unrelated wild house mice (Mus musculus L.)

Aggressive behaviour was observed to be rare in small family groups of confined wild house mice, Mus musculus L. Unrelated mice were attacked when they were introduced to a family group and in their presence intra-family aggressive behaviour increased. When two family groups of mice were allowed to meet there were frequent aggressive encounters between unrelated animals and the two groups remained separate. Resident mice were found to be aggressive towards males and females individually isolated and returned to their own family after 2 or 3 weeks absence but not after 1 week. The possibility is discussed that in wild mice odour discrimination influences the dispersal and build-up of free-living populations.     

雄性小鼠的社会优势地位、性吸引和信息素通讯

以前对小鼠的研究表明,优势雄鼠的尿液对雌性的吸引力比从属雄鼠大;同时,包皮腺分泌到尿液中的两个雄性信息素E-β-法尼烯和E, E- α-法尼烯含量相应升高,而尿液本身产生的两个雄性信息素成分--脱氢小蠹素和S-2-仲丁基- 二氢噻唑没有出现有效差异.为研究我们最近从小鼠(Mus musculus)包皮腺发现的两个雄性信息素16碳醇和16碳乙酸酯与雄性小鼠社会等级的关系, 我们将雄性小鼠两两配对饲养30天,让它们经历足够的社会争斗,建立起稳定的优势和从属关系.双项选择测试表明, 优势雄鼠的尿液对雌鼠的吸引比配对(组内)的从属鼠的强,优势雄鼠和来自另一配对组( 组间)的从属鼠尿液对雌鼠的吸引无差异.这说明优势和从属关系是相对于同一社群内的个体存在的.我们进一步用二氯甲烷分别萃取包皮腺分泌物和尿液,然后用气质联用(GC-MS )来定性和定量地分析组内优势和从属个体气味的化学组成的差异.结果表明:只有优势雄鼠的包皮腺产生的E-β-法尼烯和E, E-α-法尼烯含量一致高于从属雄鼠,而1 6碳醇和16碳乙酸酯以及尿液本身的脱氢小蠹素和丁基-二氢噻唑两个雄性信息素都无差异 .说明小鼠只利用包皮腺产生的两个分子量较小的雄性信息素浓度的相对升高传递社会优势地位的信息[动物学报 54(3):399-406,2008].     

Immune expulsion of the nematode Aspiculuris tetraptera from mice given primary and challenge infections.

The distribution of larval Aspiculuris tetraptera was studied in 4-week-old male and female CFLP mice. Whereas on days 10–12 the larvae were entirely confined to the anterior third of the colon, by day 14 larvae could be found throughout the colon. After day 17 the larvae were again restricted to the anterior colon. This change in distribution was co-incident with a loss of a large proportion of the worm burden, which occurred more consistently in female than in male mice.The degree of acquired immunity stimulated by various immunizing regimens was assessed by the survival of a challenge infection in experimental and control mice. It was found that a high level of immunity was achieved by exposure to a 19-day primary infection, a 36-day low-level infection and also by three 6-day infections, in each of which the larvae were removed by piperazine treatment immediately after the crypt phase.     

Long-term effects of accelerated or delayed sexual maturation on reproductive output in wild female house mice (Mus musculus)

The effects of acceleration and delay of puberty in female house mice on survival and reproduction were tested using 6 experimental groups: (1) control females mated at the time of first oestrus, (2) females mated at weaning, (3) females treated with male urine starting at weaning and mated at first oestrus, (4) females housed in groups and mated at first oestrus, (5) females housed alone, treated with urine from grouped females and mated at first oestrus, and (6) females housed alone and mated at 68 days of age. Females caged with males at weaning or treated with male urine and mated at puberty had lower rates of survival to 180 days of age, but did not differ in rates of fertility from mice in the other four treatments. Those females that were housed with males from weaning or treated with male urine also had smaller total numbers of litters, fewer total young, and smaller average litter sizes than did females for which the age of mating was delayed, by grouping or treatment with urine from grouped females, or by being held until age 68 days before mating. Control females mated at first oestrus generally were intermediate or did not differ from the male treatments on these dependent variables. There were no differences in the average number of female young/litter across the 6 treatments. However, females that were delayed in age of first mating had significantly more male young/litter than did females that were accelerated in their sexual development or control females.(ABSTRACT TRUNCATED AT 250 WORDS)     

Differential response to the odor of familiar intruder mice in male mice (Mus musculus)

Responses to the odor of familiar intruder male mice according to their dominance were investigated. Responses were classified into 2 aspects: the investigation of the odor and the decision-making regarding avoiding it or not. The results varied according to the dominance of the respondents and the odor donor, and also according to the context of previous encounter situations. The dominants that had attacked an intruder dominant mouse responded randomly to its odor, whereas the dominants that had fought with it tended to avoid the odor. The subordinates that had observed an intruder dominant mouse being attacked by its dominant cagemate preferred the passage with the intruder's odor. The odor of a subordinate mouse was neither avoided nor preferred by either the dominants or subordinates. It was suggested that mice distinguished the dominance of the odor donor regardless of the context of the previous encounter situation, but they responded differently according to it and also according to their own dominance status.