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21.
Identification of a novel gene involved in pilin glycosylation in Neisseria meningitidis 总被引:8,自引:8,他引:0
Michael P. Jennings Mumtaz Virji Debbie Evans Virginia Foster Yogitha N. Srikhanta Liana Steeghs Peter van der Ley & E. Richard Moxon 《Molecular microbiology》1998,29(4):975-984
The pili of Neisseria meningitidis are a key virulence factor, being major adhesins of this capsulate organism that contribute to specificity for the human host. Recently it has been reported that meningococcal pili are post-translationally modified by the addition of an O-linked trisaccharide, Gal (β1–4) Gal (α1–3) 2,4-diacetimido-2,4,6-trideoxyhexose. Using a set of random genomic sequences from N. meningitidis strain MC58, we have identified a novel gene homologous to a family of glycosyltransferases. A plasmid clone containing the gene was isolated from a genomic library of N. meningitidis strain MC58 and its nucleotide sequence determined. The clone contained a complete copy of the gene, here designated pglA (pilin glycosylation). Insertional mutations were constructed in pglA in a range of meningococcal strains with well-defined lipopolysaccharide (LPS) or pilin-linked glycan structures to determine whether pglA had a role in the biosynthesis of these molecules. There was no alteration in the phenotype of LPS from pglA mutant strains as judged by gel migration and the binding of monoclonal antibodies. In contrast, decreased gel migration of the pilin subunit molecules of pglA mutants was observed, which was similar to the migration of pilins of galE mutants of same strains, supporting the notion that pglA is a glycosyltransferase involved in the biosynthesis of the pilin-linked trisaccharide structure. The pglA mutation, like the galE mutation reported previously, had no effect on pilus-mediated adhesion to human epithelial or endothelial cells. Pilin from pglA mutants were unable to bind to monospecific antisera recognizing the Gal (β1–4) Gal structure, suggesting that PglA is a glycosyltransferase involved in the addition of galactose of the trisaccharide substituent of pilin. 相似文献
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23.
While recent imaging techniques provide insights into biological processes from the molecular to the cellular scale, phenotypes at larger scales remain poorly amenable to quantitative analyses. For example, investigations of the biophysical mechanisms generating skin morphological complexity and diversity would greatly benefit from 3D geometry and colour-texture reconstructions. Here, we report on R2OBBIE-3D, an integrated system that combines a robotic arm, a high-resolution digital colour camera, an illumination basket of high-intensity light-emitting diodes and state-of-the-art 3D-reconstruction approaches. We demonstrate that R2OBBIE generates accurate 3D models of biological objects between 1 and 100 cm, makes multiview photometric stereo scanning possible in practical processing times, and enables the capture of colour-texture and geometric resolutions better than 15 μm without the use of magnifying lenses. R2OBBIE has the potential to greatly improve quantitative analyses of phenotypes in addition to providing multiple new applications in, e.g., biomedical science. 相似文献
24.
Eliso Kvavadze Goderdzi Narimanishvili Liana Bitadze 《Vegetation History and Archaeobotany》2010,19(5-6):479-494
Pollen analyses were performed on sediment samples from ten different Saphar-Kharaba burials dating to the 15th–14th centuries b.c. Along with pollen and spores, a large amount of micro-remains of textile fibres was found near skeleton bones and especially under big bones. It was established that in all the studied samples 95% of the remains of the clothing and shroud of the deceased was made of Linum (flax) and Gossypium (cotton). Wool fibres were found in very small quantities. Based on pollen spectra and the number of the fibres found in the samples taken from under the skull it became possible to identify the sex of the deceased and especially that of children, which is rather difficult to do using palaeoanthropological methods alone. The discovery of cotton fibres in the burials of the early late Bronze Age is new not only for the Georgian region under consideration, but also for the whole Caucasus. This might indicate trade relations of the peoples of the southern Caucasus with India, where at that time cotton textiles were manufactured. 相似文献
25.
26.
Cudnoch-Jedrzejewska A Dobruch J Puchalska L Szczepańska-Sadowska E 《Regulatory peptides》2007,142(3):86-94
Experimental objectives. Because myocardial infarct is associated with overactivation of brain angiotensin II (ANG II) and vasopressin (AVP) V1a receptors we decided to determine whether AT1 and V1a receptors-mediated effects of ANG II and AVP interact in central cardiovascular control during the post-infarct state. Four groups of infarcted and four groups of sham-operated conscious rats entered the study. Results. In the infarcted rats cerebroventricular infusion of AT1 (AT1ANT, losartan) and V1a antagonist {V1aANT,d(CH(2))(5)[Tyr(Me)(2)Ala-NH(2)(9)]VP} and combined infusion of both these compounds performed 4 weeks after induction of the infarct significantly and comparably reduced mean arterial blood pressure (MABP) in comparison to control experiments (artificial cerebrospinal fluid infusion). In the sham rats MABP was not affected by any of the infusions. In control experiments MABP and HR responses to an alarming air jet stress were significantly higher in the infarcted than in the sham rats. Both responses were normalized with the same effectiveness by administration of AT1ANT, V1aANT and AT1ANT+V1aANT. In the sham rats administration of these compounds did not affect MABP and HR responses to stress. Conclusion: The results provide evidence for interaction of AT1 and V1a receptors-mediated effects of ANG II and AVP in the central cardiovascular control during the post-infarct state. 相似文献
27.
Regional ecosystem structure and function: ecological insights from remote sensing of tropical forests 总被引:7,自引:1,他引:6
Chambers JQ Asner GP Morton DC Anderson LO Saatchi SS Espírito-Santo FD Palace M Souza C 《Trends in ecology & evolution》2007,22(8):414-423
Ecological studies in tropical forests have long been plagued by difficulties associated with sampling the crowns of large canopy trees and large inaccessible regions, such as the Amazon basin. Recent advances in remote sensing have overcome some of these obstacles, enabling progress towards tackling difficult ecological problems. Breakthroughs have helped transform the dialog between ecology and remote sensing, generating new regional perspectives on key environmental gradients and species assemblages with ecologically relevant measures such as canopy nutrient and moisture content, crown area, leaf-level drought responses, woody tissue and surface litter abundance, phenological patterns, and land-cover transitions. Issues that we address here include forest response to altered precipitation regimes, regional disturbance and land-use patterns, invasive species and landscape carbon balance. 相似文献
28.
Elizabeth A. MacDougall-Shackleton Michael Clinchy Liana Zanette Bryan D. Neff 《Conservation Genetics》2011,12(5):1195-1203
Natural habitats, and the populations they sustain, are becoming increasingly fragmented by human activities. Parallels between
‘true’ islands and ‘habitat’ islands suggest that standing levels of individual genetic diversity in naturally fragmented
populations may predict the genetic fate of their anthropogenically fragmented counterparts, but this hypothesis remains largely
untested. We compared neutral-locus genetic diversity of individual song sparrows (Melospiza melodia) breeding in a naturally fragmented landscape (small coastal islands) to that of song sparrows in similar-sized ‘urban islands’
separated by roads and housing developments rather than by water. Individuals on coastal islands were more heterozygous and
less inbred than those in urban islands. Estimates of population genetic structuring (assessed by pairwise genetic differentiation
and Bayesian clustering methods) and contemporary dispersal (based on assignment tests) revealed little structure within either
landscape, suggesting that lack of connectivity at the geographic scale we investigated cannot explain the reduced heterozygosity
of urban birds. However, within-site genetic similarity was higher in the urban than the coastal landscape. Assuming that
historic genetic diversity was similar in these two environments, our findings suggest that anthropogenically fragmented populations
may lose genetic diversity faster than their naturally fragmented counterparts. 相似文献
29.
Fumonisin production by <Emphasis Type="Italic">Fusarium</Emphasis> species isolated from freshly harvested corn in Iran 总被引:1,自引:0,他引:1
Ghiasian SA Rezayat SM Kord-Bacheh P Maghsood AH Yazdanpanah H Shephard GS van der Westhuizen L Vismer HF Marasas WF 《Mycopathologia》2005,159(1):31-40
Fifty-one strains of Fusarium verticillioides and F. proliferatum isolated from corn collected from four different geographic areas in Iran, namely Fars, Khuzestan, Kermanshah and Mazandaran (an endemic oesophageal cancer (OC) area) were evaluated for their ability to produce fumonisins B1 (FB1), B2 (FB2) and B3 (FB3) in corn culture. Fumonisin levels were determined by high-performance liquid chromatography. All tested strains of F. verticillioides and F. proliferatumproduced fumonisins within a wide range of concentrations, 197–9661 g/g, 18–1974 g/g, and 21–1725 g/g for FB1, FB2, and FB3, respectively. The highest mean concentrations of FB1, FB2, and FB3 were 3897, 806 and 827 g/g, respectively. Overall, 61% of the F. verticillioides and F. proliferatum strains produced higher levels of FB3 than FB2. The mean ratios of FB1:FB2, FB1:FB3 and FB1:total fumonisins were 8, 7 and 0.7 for F. verticillioides and 5.7, 10.7 and 0.7 for F. proliferatum, respectively. Significant differences in some of the meteorological data (rainfall, relative humidity and minimum temperature) from the four provinces were observed. Fumonisin levels produced by F. verticillioides strains isolated from Khuzestan province (tropical zone) were significantly (P < 0.01) higher than the other three provinces. This is the first report of the fumonisin-producing ability of F.verticillioides and F. proliferatum strains isolated from corn harvested from different geographic areas in Iran. 相似文献
30.
Tommasini I Cerioni L Guidarelli A Cantoni O 《Biochemical and biophysical research communications》2005,329(4):1282-1287
A short-term growth of U937 cells in serum-free medium causes a prompt, mitochondrial permeability transition (MPT)-dependent necrotic response after exposure to an otherwise non-toxic concentration of peroxynitrite. This event is mediated by inhibition of extracellular signal-regulated kinase 1 and 2 (ERK1/2) phosphorylation, essential for the cytosolic phospholipase A(2)-dependent arachidonic acid (AA) release evoked by peroxynitrite. Reduced availability of the lipid messenger would therefore limit the efficiency of the AA-dependent survival signalling and cause an MPT-based necrosis. Since peroxynitrite further reduces the extent of ERK1/2 phosphorylation, regardless of whether cells had been grown in serum-free or -containing medium, it appears that basal ERK1/2 phosphorylation is a critical determinant for the survival response of U937 cells to a non-toxic, but nevertheless MPT-committing, concentration of peroxynitrite. 相似文献