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101.
Aims: To determine the effect of pH, temperature, desiccation, ethylenediaminetetraacetic acid (EDTA) and desferrioxamine B (DFO) on Panton‐Valentine leukocidin‐positive community acquired methicillin‐susceptible Staphylococcus aureus (PVL +ve CA‐MSSA) biofilm formation. Methods and Results: Biofilms from PVL +ve CA‐MSSA (clinical isolate) were subjected to pH, temperature, desiccation, EDTA and DFO. PVL +ve CA‐MSSA were more resistant to pH and heat than their planktonic equivalents. Desiccation studies demonstrated that PVL +ve CA‐MSSA biofilms were more refractory to the treatment than planktonic cells. Significant inhibition of PVL +ve CA‐MSSA biofilm formation was observed in the presence of 1 mmol l?1 EDTA. Low concentrations (2·5 μmol l?1) of DFO enhanced the growth of PVL +ve CA‐MSSA biofilms. At higher concentrations (1 mmol l?1), DFO did inhibit the growth but not as much as EDTA. A combination of EDTA and DFO inhibited PVL +ve CA‐MSSA biofilm formation at lower concentrations than either alone. Conclusions: This study demonstrates that PVL +ve CA‐MSSA biofilms are resistant to environmental stress but their growth can inhibited effectively by a mixture of EDTA and DFO. Significance and Impact of the Study: The inhibition of biofilm formation by PVL +ve CA‐MSSA using chelating agents has not been previously reported and provides a practical approach to achieve the disruption of these potentially important biofilms formed by an emerging pathogen. 相似文献
102.
103.
Two novel gene orders and the role of light-strand replication in rearrangement of the vertebrate mitochondrial genome 总被引:22,自引:8,他引:14
Macey JR; Larson A; Ananjeva NB; Fang Z; Papenfuss TJ 《Molecular biology and evolution》1997,14(1):91-104
Two novel mitochondrial gene arrangements are identified in an agamid
lizard and a ranid frog. Statistical tests incorporating phylogeny indicate
a link between novel vertebrate mitochondrial gene orders and movement of
the origin of light-strand replication. A mechanism involving errors in
light-strand replication and tandem duplication of genes is proposed for
rearrangement of vertebrate mitochondrial genes. A second mechanism
involving small direct repeats also is identified. These mechanisms
implicate gene order as a reliable phylogenetic character. Shifts in gene
order define major lineages without evidence of parallelism or reversal.
The loss of the origin of light-strand replication from its typical
vertebrate position evolves in parallel and, therefore, is a less reliable
phylogenetic character. Gene junctions also evolve in parallel. Sequencing
across multigenic regions, in particular transfer RNA genes, should be a
major focus of future systematic studies to locate novel gene orders and to
provide a better understanding of the evolution of the vertebrate
mitochondrial genome.
相似文献
104.
105.
We and others have observed that the response of serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) to chronic gonadotropin-releasing hormone-agonist (GnRH-A) treatment is substantially different in normal compared to hypogonadal males. These data suggested that products of the testes determine the gonadotropin response to GnRH-A. The present studies were designed to determine whether this effect is mediated by products of the interstitial (steroids) or the tubular compartment. To create experimental states with selective impairment of interstitial, tubular, or both compartments, 100 male sexually mature Wistar rats were divided into five groups: I, intact; II, castrated; III, castrated with 20-mm testosterone (T) implants; IV, bilaterally cryptorchid; and V, ketoconazole-treated animals. Cryptorchid animals have been shown to have impairment of tubular function while ketoconazole inhibits T biosynthesis. Each of the 5 groups was divided into 2 subgroups to receive daily injections of either saline or 1 microgram of a potent GnRH agonist, D-leu6 des-Gly10 GnRH N-ethylamide, for 4 wk. Unlike the intact animals, which showed an elevation of basal serum LH concentration after 4 wk of GnRH-A treatment, the castrated animals showed significant suppression below baseline. Animals with preferential impairment of tubular function (cryptorchid and castrated + T) also showed significant suppression of LH after GnRH-A treatment. However, the ketoconazole-treated animals (with inhibition of T biosynthesis and intact tubular function), behaved similarly to intact animals and demonstrated an elevation of LH after GnRH-A treatment.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
106.
Evolutionary relationships among the male and female mitochondrial DNA lineages in the Mytilus edulis species complex 总被引:1,自引:0,他引:1
A novel form of mitochondrial DNA (mtDNA) inheritance has previously been
documented for the blue mussel (Mytilus edulis). Female mussels inherit
their mtDNA solely from their mother while males inherit mtDNA from both
their mother and their father. In males, the paternal mtDNA is
preferentially amplified so that the male gonad is highly enriched for the
paternal mtDNA that is then transmitted from fathers to sons. We
demonstrate that this mode of mtDNA inheritance also operates in the
closely related species M. galloprovincialis and M. trossulus. The
evolutionary relationship between the male and female mtDNA lineages is
estimated by phylogenetic analysis of 455 nucleotides from the large
subunit ribosomal RNA gene. We have found that the male and female lineages
are highly divergent; the divergence of these lineages began prior to the
speciation of the three species of blue mussels. Further, the separation
between the male and female lineages is estimated to have occurred between
5.3 and 5.7 MYA.
相似文献
107.
108.
The specific type VII pneumococcal polysaccharide was isolated from the crude capsular material by precipitative and chromatographic methods. It contained D-galactose, D-glucose, L-rhamnose, 2-acetamido-2-deoxy-D-glucose, and 2-acetamido-2-deoxy-D-galactose in the molar ratio of 3.5:2.3:3.0:2.1:1.0. Some of its structural features were revealed by methylation studies, time-lapse hydrolysis, periodate oxidation, and enzymic hydrolysis. The polysaccharide is branched at residues of D-galactose and 2-acetamido-2-deoxy-D-galactose. Non-reducing end groups consisted of D-galactopyranose and 2-acetamido-2-deoxy-D-glucopyranose residues, with the former predominating. Major components of the linear chains were (1→3)-linked L-rhamnose and (1→4)-linked D-glucose; the minor ones were (1→2)-linked L-rhamnose, (1→6)-linked D-galactose, and (1→6)-linked 2-acetamido-2-deoxy-D-glucopyranose. The (1→4)-linked D-glucose components may be present as cellobiose residues. The results are in accord with structural features deduced from the serological cross-reactivity of this polysaccharide. 相似文献
109.
A H Fielder M J Walport J R Batchelor R I Rynes C M Black I A Dodi G R Hughes 《BMJ (Clinical research ed.)》1983,286(6363):425-428
The families of 29 patients with systemic lupus erythematosus and 42 normal subjects were studied to determine the inheritance of the HLA-A, B, C, and DR antigens and also the complement polymorphisms for C2, C4A, C4B, and Bf, which are encoded in the same region of the sixth chromosome. Null (silent) alleles for C4A, C4B, or C2 were found in 24 of the 29 (83%) patients compared with 18 of the 42 (43%) normal controls. HLA-DR3 was present in 20 (69%) of the patients and seven out of 39 (18%) of the normal controls. There was strong linkage disequilibrium between DR3 and the null alleles for C4A and C4B. The data did not permit the relative contributions of DR3 and null factors of C4A and C4B as genetic risk factors to be distinguished. The known association of systemic lupus erythematosus with uncommon inherited and acquired deficiencies of complement components suggests, however, that the presence of null alleles for C4A and C4B, as well as C2, found in most of the patients, is relevant to their genetic susceptibility to this disease. 相似文献
110.