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201.
Jörg Barke Ryan F Seipke Sabine Grüschow Darren Heavens Nizar Drou Mervyn J Bibb Rebecca JM Goss Douglas W Yu Matthew I Hutchings 《BMC biology》2010,8(1):109
Background
Attine ants live in an intensely studied tripartite mutualism with the fungus Leucoagaricus gongylophorus, which provides food to the ants, and with antibiotic-producing actinomycete bacteria. One hypothesis suggests that bacteria from the genus Pseudonocardia are the sole, co-evolved mutualists of attine ants and are transmitted vertically by the queens. A recent study identified a Pseudonocardia-produced antifungal, named dentigerumycin, associated with the lower attine Apterostigma dentigerum consistent with the idea that co-evolved Pseudonocardia make novel antibiotics. An alternative possibility is that attine ants sample actinomycete bacteria from the soil, selecting and maintaining those species that make useful antibiotics. Consistent with this idea, a Streptomyces species associated with the higher attine Acromyrmex octospinosus was recently shown to produce the well-known antifungal candicidin. Candicidin production is widespread in environmental isolates of Streptomyces, so this could either be an environmental contaminant or evidence of recruitment of useful actinomycetes from the environment. It should be noted that the two possibilities for actinomycete acquisition are not necessarily mutually exclusive. 相似文献202.
203.
204.
Dimitrios Makrygiannakis Shankar Revu Marianne Engström Erik af Klint Anthony P Nicholas Ger JM Pruijn Anca I Catrina 《Arthritis research & therapy》2012,14(1):R20-9
Introduction
Protein citrullination is present in the rheumatoid synovium, presumably contributing to the perpetuation of chronic inflammation, in the presence of specific autoimmunity. As a result, the present study examined the possibility that effective antirheumatic treatment will decrease the level of synovial citrullination.Methods
Synovial biopsies were obtained from 11 rheumatoid arthritis (RA) patients before and after 8 weeks of treatment with 20 mg methotrexate weekly, 15 RA patients before and 2 weeks after an intraarticular glucocorticoid injection, and eight healthy volunteers. Synovial inflammation was assessed with double-blind semiquantitative analysis of lining thickness, cell infiltration, and vascularity by using a 4-point scale. Expression of citrullinated proteins (CPs) with the monoclonal antibody F95 and peptidylarginine deiminase (PAD) 2 and 4 was assessed immunohistochemically with double-blind semiquantitative analysis. In vitro synovial fluid (SF), peripheral blood (PB), mononuclear cells (MCs), and synovial explants obtained from RA patients were incubated with dexamethasone and analyzed with immunohistochemistry for expression of CP as well as PAD2 and PAD4 enzymes.Results
The presence of synovial CP was almost exclusive in RA compared with healthy synovium and correlated with the degree of local inflammation. Treatment with glucocorticoids but not methotrexate alters expression of synovial CP and PAD enzymes, in parallel with a decrease of synovial inflammation. Ex vivo and in vitro studies suggest also a direct effect of glucocorticoids on citrullination, as demonstrated by the decrease in the level of citrullination and PAD expression after incubation of SFMC and synovial explants with dexamethasone.Conclusion
Synovial citrullination and PAD expression are dependent on local inflammation and targeted by glucocorticoids. 相似文献205.
Jayne E Rattray Marc Strous Huub JM Op den Camp Stefan Schouten Mike SM Jetten Jaap S Sinninghe Damsté 《Biology direct》2009,4(1):8-16
Background
The fatty acids of anaerobic ammonium oxidizing (anammox) bacteria contain linearly concatenated cyclobutane moieties, so far unique to biology. These moieties are under high ring strain and are synthesised by a presently unknown biosynthetic pathway. 相似文献206.
Size homoplasy and mutational processes of interrupted microsatellites in two bee species, Apis mellifera and Bombus terrestris (Apidae) 总被引:6,自引:0,他引:6
Similar microsatellite electromorphs (PCR products of the same size) can
arise from independent mutational events. Such alleles are not identical by
descent. This phenomenon, termed size homoplasy, was studied by sequencing
electromorphs of two microsatellite loci in which the stretch of basic
repeats is interrupted by different short (1-2 bp) DNA motifs. The number
and position of these interruptions were established for electromorphs from
closely and distantly related populations of honeybees and bumblebees. No
sequence difference was found when electromorphs came from the same
subspecies or from closely related subspecies, suggesting that they were
probably identical by descent. In contrast, sequence differences were often
detected in distantly related subspecies, showing that size homoplasy
frequently occurs at this level of population differentiation. Size
homoplasy is increased by limits to free length variation of alleles, a
phenomenon that seems to act on interrupted microsatellites when comparing
distantly related taxa, that is, honeybee subspecies from different
evolutionary lineages. Electromorph sequences suggest that, within the
scope of these limits, large mutation events have occurred frequently at
both interrupted loci studied. In good agreement with the molecular data,
computations based on the observed heterozygosity and number of
electromorphs and simulation studies showed that neither locus fits the
one-step stepwise mutant model (SMM). We speculate that interrupted
microsatellites in general could be characterized by a higher variance in
repeat number and consequently a lower homoplasy rate than pure ones.
Hence, interrupted microsatellites should be most appropriate for
investigating population differentiation and evolutionary relationship
between relatively distant populations.
相似文献
207.
Hoorelbeke B Van Damme EJ Rougé P Schols D Van Laethem K Fouquaert E Balzarini J 《Retrovirology》2011,8(1):10-16
Background
In a recent report, the carbohydrate-binding specificities of the plant lectins Galanthus nivalis (GNA) and the closely related lectin from Zea mays (GNAmaize) were determined by glycan array analysis and indicated that GNAmaize recognizes complex-type N-glycans whereas GNA has specificity towards high-mannose-type glycans. Both lectins are tetrameric proteins sharing 64% sequence similarity.Results
GNAmaize appeared to be ~20- to 100-fold less inhibitory than GNA against HIV infection, syncytia formation between persistently HIV-1-infected HuT-78 cells and uninfected CD4+ T-lymphocyte SupT1 cells, HIV-1 capture by DC-SIGN and subsequent transmission of DC-SIGN-captured virions to uninfected CD4+ T-lymphocyte cells. In contrast to GNA, which preferentially selects for virus strains with deleted high-mannose-type glycans on gp120, prolonged exposure of HIV-1 to dose-escalating concentrations of GNAmaize selected for mutant virus strains in which one complex-type glycan of gp120 was deleted. Surface Plasmon Resonance (SPR) analysis revealed that GNA and GNAmaize interact with HIV IIIB gp120 with affinity constants (KD) of 0.33 nM and 34 nM, respectively. Whereas immobilized GNA specifically binds mannose oligomers, GNAmaize selectively binds complex-type GlcNAcβ1,2Man oligomers. Also, epitope mapping experiments revealed that GNA and the mannose-specific mAb 2G12 can independently bind from GNAmaize to gp120, whereas GNAmaize cannot efficiently bind to gp120 that contained prebound PHA-E (GlcNAcβ1,2man specific) or SNA (NeuAcα2,6X specific).Conclusion
The markedly reduced anti-HIV activity of GNAmaize compared to GNA can be explained by the profound shift in glycan recognition and the disappearance of carbohydrate-binding sites in GNAmaize that have high affinity for mannose oligomers. These findings underscore the need for mannose oligomer recognition of therapeutics to be endowed with anti-HIV activity and that mannose, but not complex-type glycan binding of chemotherapeutics to gp120, may result in a pronounced neutralizing activity against the virus. 相似文献208.
209.
210.