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151.
A study of bacterial surface oligosaccharides were investigated among
different strains of Neisseria gonorrhoeae to correlate structural features
essential for binding to the MAb 2C7. This epitope is widely expressed and
conserved in gonococcal isolates, characteristics essential to an effective
candidate vaccine antigen. Sample lipooligosaccharides (LOS), was prepared
by a modification of the hot phenol-water method from which de-O-acetylated
LOS and oligosaccharide (OS) components were analyzed by ES-MS-CID-MS and
ES-MSnin a triple quadrupole and an ion trap mass spectrometer,
respectively. Previously documented natural heterogeneity was apparent from
both LOS and OS preparations which was admixed with fragments induced by
hydrazine and mild acid treatment. Natural heterogeneity was limited to
phosphorylation and antenni extensions to the alpha-chain. Mild acid
hydrolysis to release OS also hydrolyzed the beta(1-->6) glycosidic
linkage of lipid A. OS structures were determined by collisional and
resonance excitation combined with MS and multistep MSn which provided
sequence information from both neutral loss, and nonreducing terminal
fragments. A comparison of OS structures, with earlier knowledge of MAb
binding, enzyme treatment, and partial acid hydrolysis indicates a generic
overlapping domain for 2C7 binding. Reoccurring structural features include
a Hepalpha(1-->3)Hepbeta(1-->5)KDO trisaccharide core branched on the
nonreducing terminus (Hep-2) with an alpha(1-->2) linked GlcNAc
(gamma-chain), and an alpha-linked lactose (beta-chain) residue. From the
central heptose (Hep-1), a beta(1-->4) linked lactose (alpha-chain),
moiety is required although extensions to this residue appear unnecessary.
相似文献
152.
Catherine E Garner Stephen Smith Nicola C Elviss Tom J Humphrey Paul White Norman M Ratcliffe Christopher S Probert 《Biomarkers》2008,13(4):413-421
Volatile organic compounds from chicken faeces were investigated as biomarkers for Campylobacter infection. Campylobacter are major poultry-borne zoonotic pathogens, colonizing the avian intestinal tract. Chicken faeces are the principal source of contamination of carcasses. Fresh faeces were collected on farm sites, and Campylobacter status established microbiologically. Volatile organic compounds were pre-concentrated from the headspace above 71 separate faecal samples using solid-phase microextraction and separated and identified by gas chromatography/mass spectrometry. A Campylobacter-specific profile was identified using six of the extracted volatile organic compounds. The model developed reliably identified the presence or absence of Campylobacter in >95% of chickens. The volatile biomarker identification approach for assessing avian infection is a novel approach to enhancing biosecurity in the poultry industry and should reduce the risk of disease transmission to humans. 相似文献
153.
K.A.G. Karatzas P.M. Hocking F. Jørgensen K. Mattick S. Leach T.J. Humphrey 《Journal of applied microbiology》2008,105(5):1640-1648
Aims: The aim of the study was to investigate how stresses like low pH, which may be encountered in farms or food preparation premises, shape populations of Salmonella enterica by the selection of stress-resistant variants. Methods and Results: Stationary-phase cultures of S. enterica serovar Enteritidis and serovar Typhimurium (one strain of each) were exposed to pH 2·5 for up to 4 h, followed by growth at pH 7 for 48 h. This process was repeated 15 times in two separate experiments, which increased the acid resistance of the three out of four populations we obtained, by three- to fourfold. Sustainable variants derived from the populations showed changes in colony morphology, expression of SEF17 fimbriae, growth, increased heat resistance and reduced virulence. Conclusions: The study demonstrates that low pH environments can select for populations of S. enterica with persistent phenotypic changes such as increased acid resistance and occasionally increased SEF17 expression and lower virulence. Significance and Impact of the Study: There is a common belief that increased acid resistance coincides with increased virulence. This study demonstrates for the first time that increased acid resistance often impairs virulence and affects the general phenotype of S. enterica. 相似文献
154.
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156.
David Priddel Nicholas Carlile Margaret Humphrey Stephen Fellenberg Dean Hiscox 《Biodiversity and Conservation》2003,12(7):1391-1403
The Lord Howe Island Stick-insect (Dryococelus australis) was formerly abundant on Lord Howe Island, Australia, but was extirpated by Black Rats (Rattus rattus) in the 1920s. The species was thought to be extinct, until freshly dead remains were found by climbers on Balls Pyramid during the 1960s. In February 2001, a survey of Balls Pyramid led to the discovery of a small population of D. australis on a precipitous terrace 65 m above sea level. Two adults and one nymph (all females) were located feeding on an endemic tea-tree (Melaleuca howeana). An accumulation of plant debris at the base of the shrub, kept moist by water seepage, provided the insects with damp hollows suitable for use as daytime refugia. All evidence indicated that the species was confined to this single small terrace. A second survey, in March 2002, located a total of 24 D. australis. Twelve individuals were in the same shrub as that occupied the previous year, and 12 were dispersed among five nearby, smaller shrubs. Ten individuals were able to be sexed – eight females and two males. A number of threats to the population of D. australis on Balls Pyramid are identified and several management actions are proposed to ensure the conservation of the species. 相似文献
157.
Proper cell fate determination in mammalian gonads is critical for the establishment of sexual identity. The Hedgehog (Hh) pathway has been implicated in cell fate decision for various organs, including gonads. Desert Hedgehog (Dhh), one of the three mammalian Hh genes, has been implicated with other genes in the establishment of mouse fetal Leydig cells. To investigate whether Hh alone is sufficient to induce fetal Leydig cell differentiation, we ectopically activated the Hh pathway in Steroidogenic factor 1 (SF1)-positive somatic cell precursors of fetal ovaries. Hh activation transformed SF1-positive somatic ovarian cells into functional fetal Leydig cells. These ectopic fetal Leydig cells produced androgens and insulin-like growth factor 3 (INLS3) that cause virilization of female embryos and ovarian descent. However, the female reproductive system remained intact, indicating a typical example of female pseudohermaphroditism. The appearance of fetal Leydig cells was a direct consequence of Hh activation as evident by the absence of other testicular components in the affected ovary. This study provides not only insights into mechanisms of cell lineage specification in gonads, but also a model to understand defects in sexual differentiation. 相似文献
158.
159.
Various investigators suggest that intracranial saccular aneurysms are dynamically unstable, that they resonate in response to pulsatile blood flow. This hypothesis is based on linearized analyses or experiments on rubber "models", however, and there is a need for a more critical examination. Toward this end, we (a) derive a new nonlinear equation of motion for a pulsating spherical aneurysm that is surrounded by cerebral spinal fluid and whose behavior is described by a Fung-type pseudostrain-energy function that fits data on human lesions, and (b) use methods of nonlinear dynamics to examine the stability of such lesions against perturbations to both in vivo and in vitro conditions. The numerical results suggest that this sub-class of lesions is dynamically stable. Moreover, with the exception of transients associated with initial perturbations, inertial effects appear to be insignificant for fundamental forcing frequencies less than 10 Hz and hence for typical physiologic and laboratory conditions. We submit, therefore, that further study of the mechanics of saccular aneurysms should be focused on quasi-static stress analyses that investigate the roles of lesion geometry and material properties, including growth and remodeling. 相似文献
160.