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71.
Gunnar Hasle Gunnar A Bjune Dan Christensson Knut H Røed Anne C Whist Hans P Leinaas 《Acta veterinaria Scandinavica》2010,52(1):55
Background
The incidence of bovine babesiosis, caused by Babesia divergens (Apicomplexa: Piroplasmida) has decreased markedly since the 1930 s, but may re-emerge as a consequence of climate change and changes in legislation and pasturing practices. This is a potentially serious disease, with both economical and animal welfare consequences. Therefore, there is a need to survey the distribution of B. divergens. 相似文献72.
Rudi K Zimonja M Kvenshagen B Rugtveit J Midtvedt T Eggesbø M 《Applied and environmental microbiology》2007,73(8):2727-2734
We present a novel approach for comparing 16S rRNA gene clone libraries that is independent of both DNA sequence alignment and definition of bacterial phylogroups. These steps are the major bottlenecks in current microbial comparative analyses. We used direct comparisons of taxon density distributions in an absolute evolutionary coordinate space. The coordinate space was generated by using alignment-independent bilinear multivariate modeling. Statistical analyses for clone library comparisons were based on multivariate analysis of variance, partial least-squares regression, and permutations. Clone libraries from both adult and infant gastrointestinal tract microbial communities were used as biological models. We reanalyzed a library consisting of 11,831 clones covering complete colons from three healthy adults in addition to a smaller 390-clone library from infant feces. We show that it is possible to extract detailed information about microbial community structures using our alignment-independent method. Our density distribution analysis is also very efficient with respect to computer operation time, meeting the future requirements of large-scale screenings to understand the diversity and dynamics of microbial communities. 相似文献
73.
Bertolini LR Bertolini M Anderson GB Maga EA Madden KR Murray JD 《Journal of biotechnology》2007,128(2):246-257
Non-homologous end joining (NHEJ) is the major DNA double-strand break (DSB) repair pathway in mammalian cells and is likely responsible for the non-homologous integration of transgenes. In higher eukaryotes, this pathway predominates over the homologous recombination (HR) pathway and therefore may account for the low level of HR events that occur in mammalian cells. We evaluated the effects of transient RNAi-induced down-regulation of key components of the NHEJ pathway in human HCT116 cells. Treatment with siRNA targeting Ku70 and Xrcc4 reduced corresponding protein levels by 80-90% 48h after transfection, with a return to normal levels by 96h. Additionally, down-regulation of Ku70 and Xrcc4 resulted in a concomitant depletion of both Ku70 and Ku86 proteins. Biological consequences of transient RNAi-mediated depletion of Ku70 and Xrcc4 included sensitization to gamma radiation and a significant decrease in the expression of a linear GFP reporter gene. The results highlight the possibility of a successful means to manipulate the NHEJ pathway by RNAi. 相似文献
74.
Escaping parasitism in the selfish herd: age, size and density-dependent warble fly infestation in reindeer 总被引:2,自引:0,他引:2
Per Fauchald Rolf Rødven Bård-Jørgen Bårdsen Knut Langeland Torkild Tveraa Nigel G. Yoccoz Rolf A. Ims 《Oikos》2007,116(3):491-499
It has been suggested that animals may escape attack from mobile parasites by aggregating in selfish herds. A selfish herd disperses the risk of being attacked among its members and the per individual risk of parasite infection should therefore decrease with increasing animal density through the encounter–dilution effect. Moreover, in a selfish herd, dominant and agile animals should occupy the best positions and thereby receive fewer attacks compared to lower ranked animals at the periphery. We tested these predictions on reindeer ( Rangifer tarandus tarandus ) parasitized by warble flies ( Hypoderma tarandi ). Warble flies oviposit their eggs on reindeer during summer and induce strong anti-parasitic behavioural responses in the herds. In this period, reindeer are sexually segregated; females and calves form large and dense herds while males are more solitary. After hatching, the warble fly larvae migrate under the skin of their host where they encyst. In the present study encysted larvae were counted on newly slaughtered hides of male calves and 1.5 year old males from 18 different reindeer herds in Finnmark, northern Norway with large contrasts in reindeer density. In reindeer, body mass is correlated with fitness and social status and we hypothesized that individual carcass mass reflected the animal's ability to occupy the best positions within the herd. Larval abundance was higher among the 1.5 year old males than among the calves. For calves we found in accordance with the selfish herd hypothesis a negative relationship between larval abundance and animal density and between larval abundance and body mass. These relationships were absent for the 1.5 year old males. We suggest that these differences were due to different grouping behaviour where calves and females, but not males, aggregated in selfish herds where they escaped parasitism. 相似文献
75.
Bovine viral diarrhea virus: prevention of persistent fetal infection by a combination of two mutations affecting Erns RNase and Npro protease 下载免费PDF全文
Meyers G Ege A Fetzer C von Freyburg M Elbers K Carr V Prentice H Charleston B Schürmann EM 《Journal of virology》2007,81(7):3327-3338
Different genetically engineered mutants of bovine viral diarrhea virus (BVDV) were analyzed for the ability to establish infection in the fetuses of pregnant heifers. The virus mutants exhibited either a deletion of the overwhelming part of the genomic region coding for the N-terminal protease N(pro), a deletion of codon 349, which abrogates the RNase activity of the structural glycoprotein E(rns), or a combination of both mutations. Two months after infection of pregnant cattle with wild-type virus or either of the single mutants, the majority of the fetuses contained virus or were aborted or found dead in the uterus. In contrast, the double mutant was not recovered from fetal tissues after a similar challenge, and no dead fetuses were found. This result was verified with a nonrelated BVDV containing similar mutations. After intrauterine challenge with wild-type virus, mutated viruses, and cytopathogenic BVDV, all viruses could be detected in fetal tissue after 5, 7, and 14 days. Type 1 interferon (IFN) could be detected in fetal serum after challenge, except with wild-type noncytopathogenic BVDV. On days 7 and 14 after challenge, the largest quantities of IFN in fetal serum were induced by the N(pro) and RNase-negative double mutant virus. The longer duration of fetal infection with the double mutant resulted in abortion. Therefore, for the first time, we have demonstrated the essential role of both N(pro) and E(rns) RNase in blocking interferon induction and establishing persistent infection by a pestivirus in the natural host. 相似文献
76.
The intentional introduction of red king crab, Paralithodes camtschatica (Tilesius, 1815) in the Barents Sea represent one of a few successful cases and one that now supports a commercial fishery.
Introductions of alien species into new environments are often associated with genetic bottlenecks, which cause a reduction
in the genetic variation, and this could be important for the spreading potential of the species in the Atlantic Ocean. Red
king crab samples collected in the Varangerfjord located on the Barents Sea (northern Norway) were compared with reference
crab samples collected from the Bering Sea and Kamchatka regions in the Pacific Ocean. All samples were screened for eleven
microsatellite loci, based on the development of species-specific primers. The observed number of alleles per locus was similar,
and no reduction in genetic variation, including gene diversity and allelic richness, was detected between the Varangerfjord
sample and the reference sample from Okhotsk Sea near Kamchatka, indicating no genetic bottlenecking at least for the microsatellite
loci investigated. The same results were found in comparison with the sample from Bering Sea. The level of genetic differentiation
among the samples, measured as overall F
ST
across all loci, was relatively low (0.0238) with a range of 0.0035–0.1000 for the various loci investigated. The largest
pairwise F
ST
values were found between the Bering Sea and Varangerfjord/Barents Sea samples, with a value of 0.0194 across all loci tested.
The lowest value (0.0101) was found between the Varangerfjord and Kamchatka samples. Genetic differentiation based on exact
tests on allele frequencies revealed highly significant differences between all pairwise comparisons. The high level of genetic
variation found in the Varangerfjord/Barents Sea sample could be of significance with respect to further spreading of the
species to other regions in the North Atlantic Ocean. 相似文献
77.
Knut E. Jørstad P. A. Prodohl A.-L. Agnalt M. Hughes E. Farestveit A. F. Ferguson 《Hydrobiologia》2007,590(1):103-114
American lobsters (Homarus americanus H. Milne Edwards, 1837) are imported live to Europe and should according regulations be kept in land-based tanks until sold. In spite of the strict regulations aimed specifically at preventing the introduction of this species into the NE Atlantic, several specimens of H. americanus have been captured in the wild, especially in Oslofjord, Norway since 1999. One of the great concerns is interbreeding between the introduced American species and the local European lobster, H. gammarus (Linnaeus, 1758). For this reason an awareness campaign was launched in 2000 focusing on morphologically “unusual” lobsters caught in local waters. Morphological characters have been based on colour and sub-ventral spines on the rostrum. Two samples of H. americanus were used for comparisons, as well as samples of European lobster from Oslofjord collected in 1992. Previous genetic analyses (allozymes, mtDNA and microsatellite DNA) have demonstrated that the American lobster is distinct from its European counterpart, with several additional alleles at many loci in addition to different allelic frequency distribution of alleles of “shared” alleles. During the present study, thirteen microsatellite loci were tested in the initial screening, and the three most discriminating loci (Hgam98, Hgam197b and Hgam47b) were used in a detailed comparison between the two species. A total of 45 unusual lobsters were reported captured from Ålesund (west) to Oslofjord (southeast) from 2001 to 2005 and these were analysed for the three microsatellite loci. Nine specimens were identified as American lobsters. Comparisons between morphological and genetic characteristics revealed that morphological differences are not reliable in discrimination the two species, or to identify hybrids. Further, some loci display almost no overlapping in allele frequency distribution for the reference samples analysed, thus providing a reliable tool to identify hybrids. 相似文献
78.
79.
Pimentel-Schmitt EF Thomae AW Amon J Klieber MA Roth HM Muller YA Jahreis K Burkovski A Titgemeyer F 《Journal of molecular microbiology and biotechnology》2007,12(1-2):75-81
Carbon metabolism and regulation is poorly understood in mycobacteria, a genus that includes some major pathogenic species like Mycobacterium tuberculosis and Mycobacterium leprae. Here, we report the identification of a glucose kinase from Mycobacterium smegmatis. This enzyme serves in glucose metabolism and global carbon catabolite repression in the related actinomycete Streptomyces coelicolor. The gene, msmeg1356 (glkA), was found by means of in silico screening. It was shown that it occurs in the same genetic context in all so far sequenced mycobacterial species, where it is located in a putative tricistronic operon together with a glycosyl hydrolase and a putative malonyl-CoA transacylase. Heterologous expression of glkA in an Escherichia coli glucose kinase mutant led to the restoration of glucose growth, which provided in vivo evidence for glucose kinase function. GlkA(Msm) was subsequently overproduced in order to study its enzymatic features. We found that it can form a dimer and that it efficiently phosphorylates glucose at the expense of ATP. The affinity constant for glucose was with 9 mM about eight times higher and the velocity was about tenfold slower when compared to the parallel measured glucose kinase of S. coelicolor. Both enzymes showed similar substrate specificity, which consists in an ATP-dependent phosphorylation of glucose and no, or very inefficient, phosphorylation of the glucose analogues 2-deoxyglucose and methyl alpha-glucoside. Hence, our data provide a basis for studying the role of mycobacterial glucose kinase in vivo to unravel possible catalytic and regulatory functions. 相似文献
80.