X-Chromosome inactivation in cloned mouse embryos. (65/548)

To study whether cloning resets the epigenetic differences between the two X chromosomes of a somatic female nucleus, we monitored X inactivation in cloned mouse embryos. Both X chromosomes were active during cleavage of cloned embryos, followed by random X inactivation in the embryo proper. In the trophectoderm (TE), X inactivation was nonrandom with the inactivated X of the somatic donor being chosen for inactivation. When female embryonic stem cells with two active X chromosomes were used as donors, random X inactivation was seen in the TE and embryo. These results demonstrate that epigenetic marks can be removed and reestablished on either X chromosome during cloning. Our results also suggest that the epigenetic marks imposed on the X chromosomes during gametogenesis, responsible for normal imprinted X inactivation in the TE, are functionally equivalent to the marks imposed on the chromosomes during somatic X inactivation.  (+info)

Genetic diversity of hantaviruses isolated in china and characterization of novel hantaviruses isolated from Niviventer confucianus and Rattus rattus. (66/548)

The antigenic and genetic properties of 46 hantaviruses from China, 13 from patients, 23 from rodents, and 10 from unknown hosts, were compared with those of other hantaviruses. The viruses were classified as either Hantaan (HTN) or Seoul (SEO) viruses. A phylogenetic analysis of the partial M (300 bp) and S (around 485 bp) genomes of HTN viruses identified nine distinct genetic subtypes, one consisting of isolates from Korea. The SEO viruses were divided into five genetic subtypes, although they had less variability than the HTN subtypes. There was a correlation between the subtype and province of origin for four subtypes of HTN viruses, confirming geographical clustering. Hantaan virus NC167 isolated from Niviventer confucianus and SEO virus Gou3 isolated from Rattus rattus were the basal clades in each virus. The phylogenetic trees constructed from the entire S and M segments suggested that NC167 was introduced to N. confucianus in a host-switching event. The reactivity of a panel of 35 monoclonal antibodies was almost exactly the same in NC167 and a representative HTN virus and in Gou3 and a representative SEO virus. However, there was a one-way cross-neutralization between them. These results confirm the varied nature of Murinae-associated hantaviruses in China.  (+info)

Genetic and developmental analysis of X-inactivation in interspecific hybrid mice suggests a role for the Y chromosome in placental dysplasia. (67/548)

It has been shown previously that abnormal placental growth, i.e., hyper- and hypoplasia, occurs in crosses and backcrosses between different mouse (Mus) species. A locus that contributes to this abnormal development has been mapped to the X chromosome. Unexpectedly, an influence of fetal sex on placental development has been observed, in that placentas attached to male fetuses tended to exhibit a more pronounced phenotype than placentas attached to females. Here, we have analyzed this sex dependence in more detail. Our results show that differences between male and female placental weights are characteristic of interspecific matings and are not observed in intraspecific Mus musculus matings. The effect is retained in congenic lines that contain differing lengths of M. spretus-derived X chromosome. Expression of the X-linked gene Pgk1 from the maternal allele only and lack of overall activity of two paternally inherited X-linked transgenes indicate that reactivation or lack of inactivation of the paternal X chromosome in trophoblasts of interspecific hybrids is not a frequent occurrence. Thus, the difference between male and female placentas seems not to be caused by faulty preferential X-inactivation. Therefore, these data suggest that the sex difference of placental weights in interspecific hybrids is caused by interactions with the Y chromosome.  (+info)

Prevalence of IgG antibodies response to Borrelia burgdorferi s.l. in populations of wild rodents from Mazury lakes district region of Poland. (68/548)

Three rodent species: Clethrionomys glareolus, Apodemus flavicollis and Microtus arvalis from Mazury Lakes District of Poland were examined for antibodies to Borrelia burgdorferi by enzyme-labelled protein G assay (ELGA). C. glareolus had an exceptionally high prevalence of B. burgdorferi antibodies - 58%, but A. flavicollis and M. arvalis also showed significant prevalence of 16.6% and 10.5%, respectively. The ELGA method is highly specific with good reproducibility. Nevertheless, some differences of sensitivity of assessed samples were season dependent. However, high seroprevalence did not coincide with infestation rates of examined rodents by I. ricinus ticks. The results indicated that in Mazury Lakes District, naturally infected rodents play an important role as an animal reservoir host for B. burgdorferi, and these animals may increase the risk of human infections in some habitats used as recreation areas. Also, this study shows that ELGA method based on the affinity of protein G for IgG of wild animals may be widely used to determine the competent zoonotic reservoir of B. burgdorferi.  (+info)

Bartonella birtlesii sp. nov., isolated from small mammals (Apodemus spp.). (69/548)

Three strains isolated from Apodemus spp. were similar to Bartonella species on the basis of phenotypic characteristics. Futhermore, genotypic analysis based on sequence analysis of the 16S rRNA and gltA genes and on DNA-DNA hybridization showed that the three isolates represented a distinct and new species of Bartonella. The name Bartonella birtlesii is proposed for the new species. The type strain of B. birtlesii sp. nov. is IBS 325T (= CIP 106294T = CCUG 44360T).  (+info)

Effect of gonadotrophins on the ovarian interstitial tissue of the wood mouse, Apodemus sylvaticus. (70/548)

The ovarian interstitial tissue of the wood mouse (Apodemus sylvaticus) is extensively developed. The effect of equine chorionic gonadotrophin (eCG) and human chorionic gonadotrophin (hCG) on ovarian interstitial tissue was investigated in wood mice from a laboratory stock. The tissue was assessed by measuring the relative size of the cells, cell nucleus diameter and (in adults) nuclear shape. Hormone-treated wood mice had larger interstitial cells and larger cell nuclei than untreated animals. In addition, the cell nuclei of adult hormone-treated wood mice had a smooth round or oval outline, whereas those of untreated animals had an irregular outline with spiky projections. Electron microscopy showed that the irregular spiky outline of the cell nuclei in untreated wood mice was caused by distortions of the nuclear membrane by a large number of intracellular lipid droplets; the droplets were less abundant in the hormone-treated animals. These experiments indicate that the cells of the interstitial tissue of the wood mouse are under the control of gonadotrophins, and that these cells are likely to be a site of the synthesis and release of steroid hormones. The methods used in this study to assess the state of the cells could be applied to animals from the field to investigate the role of interstitial tissue in the reproductive biology of wood mice.  (+info)

Mus cervicolor murine leukemia virus isolate M813 belongs to a unique receptor interference group. (71/548)

Murine leukemia virus (MuLV) M813 was originally isolated from the Southeast Asian rodent Mus cervicolor. As with the ecotropic MuLVs derived from Mus musculus, its host range is limited to rodent cells. Earlier studies have mapped its receptor to chromosome 2, but it has not been established whether M813 shares a common receptor with any other MuLVs. In this study, we have performed interference assays with M813 and viruses from four interference groups of MuLV. The infection efficiency of M813 was not compromised in cells expressing any one of the other MuLVs, demonstrating that M813 must use a distinct receptor for cell entry. The entire M813 env coding region was molecularly cloned. Sequence analysis revealed high similarity with other MuLVs but with a unique receptor-binding domain. Substitution of M813 env sequences in Moloney MuLV resulted in a replication-competent virus with a host range and interference profile similar to those of the biological clone M813. M813 thus defines a novel receptor interference group of type C MuLVs.  (+info)

Analysis of a novel strain of murine gammaherpesvirus reveals a genomic locus important for acute pathogenesis. (72/548)

Infection of mice by murine gammaherpesvirus 68 (MHV-68) is an excellent small-animal model of gammaherpesvirus pathogenesis in a natural host. We have carried out comparative studies of another herpesvirus, murine herpesvirus 76 (MHV-76), which was isolated at the same time as MHV-68 but from a different murid host, the yellow-necked mouse (Apodemus flavicollis). Molecular analyses revealed that the MHV-76 genome is essentially identical to that of MHV-68, except for deletion of 9,538 bp at the left end of the unique region. MHV-76 is therefore a deletion mutant that lacks four genes unique to MHV-68 (M1, M2, M3, and M4) as well as the eight viral tRNA-like genes. Replication of MHV-76 in cell culture was identical to that of MHV-68. However, following infection of mice, MHV-76 was cleared more rapidly from the lungs. In line with this, there was an increased inflammatory response in lungs with MHV-76. Splenomegaly was also significantly reduced following MHV-76 infection, and much less latent MHV-76 was detected in the spleen. Nevertheless, MHV-76 maintained long-term latency in the lungs and spleen. We utilized a cosmid containing the left end of the MHV-68 genome to reinsert the deleted sequence into MHV-76 by recombination in infected cells, and we isolated a rescuant virus designated MHV-76(cA8+)4 which was ostensibly genetically identical to MHV-68. The growth properties of the rescuant in infected mice were identical to those of MHV-68. These results demonstrate that genetic elements at the left end of the unique region of the MHV-68 genome play vital roles in host evasion and are critical to the development of splenic pathology.  (+info)