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Many Strains (many + strain)
Selected AbstractsIdentification of novel genes regulated by ,-melanocyte-stimulating hormone in murine bone marrow-derived dendritic cellsEXPERIMENTAL DERMATOLOGY, Issue 9 2004T. Brzoska Many strains of evidence indicate that ,-melanocyte-stimulating hormone (,-MSH) elicits its immunomodulatory activity via binding to melanocortin receptors (MC-Rs) expressed on monocytes and dendritic cells. In order to identify novel target genes regulated by ,-MSH in these cells, we prepared bone marrow-derived dendritic cell precursors from BALB/c mice and treated them with GM-CSF and IL-4 for 6 days. The MC-R profile on these immature dendritic cells was first determined by quantitative RT-PCR. Both transcripts for MC-1R and MC-5R were detected in these cells. Cells were subsequently stimulated with dinitrobenzene sulfonic acid (DNBS), ,-MSH or both substances for 2 or 16 h. After RNA preparation, cDNA synthesis and in vitro transcripton hybridization of biotinylated cRNA samples was performed on MG U74A Affymetrix gene chips. Data evaluation, cleansing, extraction and analysis of the more than 12 000 cloned genes and expressed sequence tags were performed using the GENE DATA ANALYST vs. 1 Expressionist software. Filter criteria included a minimum threshold of 100, normalization by the logarithmic mean and a quality setting of P < 0.04. Changes with a change factor of >2 were regarded as significant. As expected, stimulation with DNBS resulted in induction or upregulation of genes encoding proinflammatory cytokines, growth factors, signal transduction intermediates and transcription factors. Treatment with ,-MSH blocked the DNBS-driven upregulation of several known genes such as IL-1 or CD86. On the other hand, ,-MSH modulated the expression of several novel genes implicated in immunomodulation, e.g. IL-1, converting enzyme, IFN-, receptor, FK506-binding proteins or several neuropeptides and their receptors. These data indicate novel molecular targets by which ,-MSH exerts its immunomodulatory activities in immunocompetent cells. [source] Pyrethroid and DDT cross-resistance in Aedes aegypti is correlated with novel mutations in the voltage-gated sodium channel geneMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2003C. Brengues Abstract. Samples of the dengue vector mosquito Aedes aegypti (L.) (Diptera: Culicidae) were collected from 13 localities between 1995 and 1998. Two laboratory strains, Bora (French Polynesia) and AEAE, were both susceptible to DDT and permethrin; all other strains, except Larentuka (Indonesia) and Bouaké (Ivory Coast), contained individual fourth-instar larvae resistant to permethrin. Ten strains were subjected to a range of biochemical assays. Many strains had elevated carboxylesterase activity compared to the Bora strain; this was particularly high in the Indonesian strains Salatiga and Semarang, and in the Guyane strain (Cayenne). Monooxygenase levels were increased in the Salatiga and Paea (Polynesia) strains, and reduced in the two Thai strains (Mae Kaza, Mae Kud) and the Larentuka strain. Glutathione S-transferase activity was elevated in the Guyane strain. All other enzyme profiles were similar to the susceptible strain. The presence of both DDT and pyrethroid resistance in the Semarang, Belem (Brazil) and Long Hoa (Vietnam) strains suggested the presence of a knock-down resistant (kdr)-type resistance mechanism. Part of the S6 hydrophobic segment of domain II of the voltage-gated sodium channel gene was obtained by RT-PCR and sequenced from several insects from all 13 field strains. Four novel mutations were identified. Three strains contained identical amino acid substitutions at two positions, two strains shared a different substitution, and one strain was homozygous for a fourth alteration. The leucine to phenylalanine substitution that confers nerve insensitivity to pyrethroids in a range of other resistant insects was absent. Direct neurophysiological assays on individual larvae from three strains with these mutations demonstrated reduced nerve sensitivity to permethrin or lambda cyhalothrin inhibition compared to the susceptible strains. [source] Outbreak of gastroenteritis caused by the pandemic Vibrio parahaemolyticus O3 : K6 in MexicoFEMS MICROBIOLOGY LETTERS, Issue 1 2006Héctor Cabanillas-Beltrán Abstract During 2003 and during late September of 2004, more than 1230 cases of gastroenteritis were reported in the south of Sinaloa State, north-western Mexico. All cases were attributed to the consumption of raw or undercooked shrimp collected at the Huizache-Caimanero lagunary system. Vibrio parahaemolyticus was identified by standard biochemical methods, and many strains were positive for PCR amplifications of the tlh and tdh genes and negative for the trh gene. A representative strain belonged to the O3 : K6 serogroup. This is the first outbreak of gastroenteritis caused by the pandemic strains of O3 : K6 V. parahaemolyticus in México. [source] Overcoming the restriction barrier to plasmid transformation of Helicobacter pyloriMOLECULAR MICROBIOLOGY, Issue 5 2000John P. Donahue Helicobacter pylori strains demonstrate substantial variability in the efficiency of transformation by plasmids from Escherichia coli, and many strains are completely resistant to transformation. Among the barriers to transformation are numerous strain-specific restriction-modification systems in H. pylori. We have developed a method to protect plasmid DNA from restriction by in vitro site-specific methylation using cell-free extracts of H. pylori before transformation. In two cases, plasmid DNA treated with cell-free extracts in vitro acquired the restriction pattern characteristic of genomic DNA from the source strain. Among three strains examined in detail, the transformation frequency by treated plasmid shuttle and suicide vectors was significantly increased compared with mock-treated plasmid DNA. The results indicate that the restriction barrier in H. pylori can be largely overcome by specific DNA methylation in vitro. The approach described should significantly enhance the ability to manipulate gene function in H. pylori and other organisms that have substantial restriction barriers to transformation. [source] Rust of flax and linseed caused by Melampsora liniMOLECULAR PLANT PATHOLOGY, Issue 4 2007GREGORY J. LAWRENCE SUMMARY Melampsora lini, while of economic importance as the causal agent of rust disease of flax and linseed, has for several decades been the ,model' rust species with respect to genetic studies of avirulence/virulence. Studies by Harold Flor demonstrated that single pairs of allelic genes determine the avirulence/virulence phenotype on host lines with particular resistance genes and led him to propose his famous ,gene-for-gene' hypothesis. Flor's inheritance studies, together with those subsequently carried out by others, also revealed that, in some cases, an inhibitor gene pair and an avirulence/virulence gene pair interact to determine the infection outcome on host lines with particular resistance genes. Recently, avirulence/virulence genes at four loci, AvrL567, AvrM, AvrP4 and AvrP/AvrP123, have been cloned. All encode novel, small, secreted proteins that are recognized inside plant cells. Yeast two-hybrid studies have shown that the AvrL567 proteins interact directly with the resistance gene protein. The molecular basis of Flor's gene-for-gene relationship has now been elucidated for six interacting gene pairs: those involving resistance genes L5, L6, L7, M, P and P2, where both the resistance gene and the corresponding avirulence gene have been cloned. In other inheritance studies it has been shown that M. lini does not possess a (+) and (,) mating system, but may possess a two factor system. Double-stranded (ds) RNA molecules occur in many strains of M. lini: examination of the progeny of one strain that possesses 11 dsRNA molecules revealed that they fall into three transmission units, designated L, A and B. The L unit consists of a single large dsRNA of 5.2 kbp while the A and B units each consist of five dsRNAs in the size range 1.1,2.8 kbp. The three units have different sexual and asexual transmission characteristics. The L unit is encapsidated in a virus-like particle, whereas the other units are not encapsidated. The population and coevolutionary aspects of M. lini on a wild, native Australian host species, Linum marginale, have been extensively investigated. A recent molecular analysis revealed that the M. lini isolates from L. marginale fall into two distinct lineages, one of which is apparently hybrid between two diverse genomes. Isolates in this lineage are largely fixed for heterozygosity, which suggests that sexual recombination does not occur in this lineage. [source] Recent developments in the molecular discrimination of formae speciales of Fusarium oxysporumPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 8 2008Bart Lievens Abstract Rapid and reliable detection and identification of potential plant pathogens is required for taking appropriate and timely disease management measures. For many microbial species of which all strains generally are plant pathogens on a known host range, this has become quite straightforward. However, for some fungal species this is quite a challenge. One of these is Fusarium oxysporum Schlechtend:Fr., which, as a species, has a very broad host range, while individual strains are usually highly host-specific. Moreover, many strains of this fungus are non-pathogenic soil inhabitants. Thus, with regard to effective disease management, identification below the species level is highly desirable. So far, the genetic basis of host specificity in F. oxysporum is poorly understood. Furthermore, strains that infect a particular plant species are not necessarily more closely related to each other than to strains that infect other hosts. Despite these difficulties, recently an increasing number of studies have reported the successful development of molecular markers to discriminate F. oxysporum strains below the species level. Copyright © 2008 Society of Chemical Industry [source] There are High Levels of Functional and Genetic Diversity in Oxyrrhis marinaTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 3 2005CHRIS D. LOWE Abstract. Oxyrrhis marina, a widely distributed marine protist, is used to model heterotrophic flagellate responses in microbial food webs. Although clonal variability occurs in protists, assessments of intraspecific diversity are rare; such assessments are critical, particularly where species are used as models in ecological studies. To address the extent of intraspecific variation within O. marina, we assessed diversity among 11 strains using 5.8S rDNA and ITS sequences. The 5.8S rDNA and ITS regions revealed high divergence between strains: 63.1% between the most diverse. To compare O. marina diversity relative to other alveolates, 18S rDNA sequences for five strains were analysed with sequences from representatives of the major alveolate groups. 18S rDNA also revealed high divergence in O. marina. Additionally, consistent with phylogenies based on protein coding genes, maximum likelihood analysis indicated that O. marina was monophyletic and ancestral to the dinoflagellates. To assess ecophysiological differences, growth rates of seven O. marina strains were measured at 10 salinities (10,55,). Two salinity responses occurred: one group achieved highest growth rates at high salinities; the other grew best at low salinities. There was no clear correlation between molecular, ecophysiological, or geographical differences. However, salinity tolerance was associated with habitat type: intertidal strains grew best at high salinities; open-water strains grew best at low salinities. These data indicate the need to examine many strains of a species in both phylogenetic and ecological studies, especially where key-species are used to model ecological processes. [source] | ||||||||||