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351.
Gerlach D. Schalén C. Tigyi Z. Nilsson B. Forsgren A. Naidu A. S. 《Current microbiology》1994,28(6):331-338
During investigation of the interaction of human lactoferrin (HLf) with variou bacteria, it was found that inStreptococcus pyogenes, HLf binding occurred to agar-rather than broth-grown cells irrespective of the nutrients used. Furthermore, binding of HLf to broth-grown, heat-killed bacteria was induced by overnight incubation on agar media or short-time exposure of the cells to water-soluble agar extract. The binding pattern was revealed in most of 92S. pyogenes strains representing various M-or T-types with no apparent type variation. The component thus bridging the attachment of HLf to the streptococcal cell surface was recovered in extracts of agar-grown cells and isolated by affinity chromatography on HLf-sepharose. By gel filtration in the presence of radiolabeled HLf, this component exhibited similar elution position as crude water-soluble agar extract. Chemical analysis identified the active HLf-binding agar component to be a galactose-rich polysaccharide (GRP). Further binding tests showed that the interaction between streptococci and GRP was stable in the presence of high molar NaCl, KSCN, or urea and was unaffected by various serum or matrix proteins or by streptococcal lipoteichoic acid; however, a moderate inhibition by heparin or bovine mucin was observed. Studies on isogenic mutants ofS. pyogenes did not support the involvement of M-protein or the hyaluronate capsule in the binding of GRP. SDS-PAGE and Western blot analyses revealed a GRP-binding protein of approximately 70 kDa in the cell-wall extracts of two strains ofS. pyogenes, types M19 and M55. Finally, the adherence of (broth-grown)3H-thymidine-labeledS. pyogenes, type M19, to the pharyngeal epithelial cell line DT-562 or to normal tonsillar epithelial cells was inhibited by GRP in a dose-related manner. We thus propose that the streptococcal GRP-binding component may represent a novel surface lectin acting as a mucosal adhesin forS. pyogenes, in accordance with previous data indicating that galactosecontaining sugar moieties may serve as ligands for the adherence of streptococci to pharyngeal cells. Our results also indicate that GRP-like components such as mucin or heparin might act to block epithelial adherence ofS. pyogenes at the mucosal level. 相似文献
352.
Two teak (Tectona grandis L.f.) phenotypes differing in their leaf length/breadth ratios were subjected to water stress by withholding water supply
for three weeks. Growth rates of whole plants, developing leaves (1st and 2nd from shoot apices), and 2nd and 3rd internodes were higher in broad leaved (BL) phenotype than in narrow leaved (NL) phenotype before and after imposing water
stress treatment. However, the effect of water stress on these parameters was higher in the BL phenotype than in the NL one.
Diurnal course of net photosynthetic rate (P
N) of 3rd or 4th leaves from shoot apices measured under well-watered conditions was higher for the NL than BL phenotype. P
N, stomatal conductance (g
s), and transpiration rate (E) in both phenotypes were negatively affected by water stress and their decline under water stress was significantly higher
in the BL than NL plants.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
353.
354.
J M Naidu H W Mohrenweiser 《Comparative biochemistry and physiology. B, Comparative biochemistry》1985,81(3):615-619
The previous studies of the interaction of purine analogs and human erythrocyte acid phosphatase isozymes were extended to include erythrocyte acid phosphatase from seven other species. Consistent responses, similar to the observations with the several genotypically different human isozymes, were observed. The isozyme from chimpanzee erythrocytes was similar to the human B-type isozyme while the baboon and cow isozymes were at the other extreme in responsiveness and were more divergent from the B-isozyme than was the human A-type isozyme. The ACP from rabbit, dog, sheep and rhesus erythrocytes exhibited intermediate levels of responsiveness but did differ from the human A-type isozyme. Additional studies indicated some differences between the responsiveness of the partially purified erythrocyte enzyme and the low molecular weight ACP from liver. 相似文献
355.
356.
A serious disease of groundnut (Arachis hypogaea L.) characterized by stunting of plants, downward rolling, mottling, general chlorosis and reduced size of the leaflets was observed in the Sudan. Surveys conducted from 1992 to 1994 showed that this disease was restricted to irrigated groundnut crops grown between the two Niles. The virus had slightly flexuous filamentous particles (626 nm long) and was transmitted by whiteflies. It was identified serologically as cowpea mild mottle virus (CPMMV). This appears to be the first record of natural occurrence of CPMMV on groundnut in the Sudan and the first evidence that it causes a disease of major economic importance. 相似文献