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111.
One of the functions associated with the oral streptococcal surface protein I/II is to bind to human extracellular matrix molecules or blood components, which could act as opportunistic ligands in pathological circumstances. In order to understand the relative specificity of the binding repertoire of this bacterial adhesin, we examined by infrared measurements the mode of binding of the protein I/II from Streptococcus mutans OMZ175 (I/IIf) to fibronectin and fibrinogen. This approach revealed the beta-structure forming capacity of I/IIf upon interaction with both proteins. The forming of intermolecular beta-structures may provide a non-selective way of interaction between I/IIf and its possible targets. 相似文献
112.
Destabilization of tetraplex structures of the fragile X repeat sequence (CGG)n is mediated by homolog-conserved domains in three members of the hnRNP family 总被引:3,自引:1,他引:2
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Hairpin or tetrahelical structures formed by a d(CGG)n sequence in the FMR1 gene are thought to promote expansion of the repeat tract. Subsequent to this expansion FMR1 is silenced and fragile X syndrome ensues. The injurious effects of d(CGG)n secondary structures may potentially be countered by agents that act to decrease their stability. We showed previously that the hnRNP-related protein CBF-A destabilized G′2 bimolecular tetraplex structures of d(CGG)n. Analysis of mutant proteins revealed that the CBF-A-conserved domains RNP11 and ATP/GTP binding box were sufficient and necessary for G′2 d(CGG)n disruption while the RNP21 motif inhibited the destabilization activity. Here, we report that a C-terminal fragment of CBF-A whose only remaining conserved domain was the ATP/GTP binding motif, disrupted G′2 d(CGG)n more selectively than wild-type CBF-A. Further, two additional members of the hnRNP family, hnRNP A2 and mutant hnRNP A1 effectively destabilized G′2 d(CGG)n. Examination of mutant hnRNP A2 proteins revealed that, similar to CBF-A, their RNP11 element and ATP/GTP binding motif mediated G′2 d(CGG)n disruption, while the RNP21 element blocked their action. Similarly, the RNP11 and RNP21 domains of hnRNP A1 were, respectively, positive and negative mediators of G′2 d(CGG)n destabilization. Last, employing the same conserved motifs that mediated disruption of the DNA tetraplex G′2 d(CGG)n, hnRNP A2 destabilized r(CGG)n RNA tetraplex. 相似文献
113.
The hexosamine pathway (HP) is a biochemical hypothesis recently proposed explaining cellular alterations occurring during diabetic microvascular complications. Diabetic retinopathy is a common microvascular complication of diabetes, and it is known that cell proliferation is severely affected during the development of the disease. Particularly, early stages are characterized by death of the retinal microvascular cells, pericytes. Gangliosides have often been described to regulate cell growth; however, very few studies focused on the potential role of gangliosides in diabetic microvascular alterations. The aim of this article was to investigate the effect of the HP activation on pericyte proliferation and determine the potential implication of gangliosides in this process. Results indicate first that HP activation, mimicked by glucosamine treatment, decreased pericyte proliferation. Second, glucosamine treatment induced a modification of gangliosides pattern, particularly GM1 and GD3 were significantly increased. Next, results showed that exogenous addition of a-series gangliosides (GM3, GM2, GM1, GD1a) and b-series ganglioside (GD3) caused a decrease of pericyte proliferation, whereas nonsialylated precursors glucosylceramide and lactosylceramide were without effect. Furthermore, when ganglioside biosynthesis was blocked using PPMP, a glucosylceramide synthase inhibitor, the effects of glucosamine on pericyte proliferation were partially reversed. Our results suggest that in retinal pericytes, gangliosides and particularly GM1 and GD3 that are increased in response to glucosamine, are involved in the antiproliferative effect of glucosamine. These observations also underlie the potential involvement of gangliosides in a pathological context, such as diabetic microvascular complications. 相似文献
114.
Abnormal mesoderm patterning in mouse embryos mutant for the SH2 tyrosine phosphatase Shp-2. 总被引:29,自引:0,他引:29
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T M Saxton M Henkemeyer S Gasca R Shen D J Rossi F Shalaby G S Feng T Pawson 《The EMBO journal》1997,16(9):2352-2364
Shp-1, Shp-2 and corkscrew comprise a small family of cytoplasmic tyrosine phosphatases that possess two tandem SH2 domains. To investigate the biological functions of Shp-2, a targeted mutation has been introduced into the murine Shp-2 gene, which results in an internal deletion of residues 46-110 in the N-terminal SH2 domain. Shp-2 is required for embryonic development, as mice homozygous for the mutant allele die in utero at mid-gestation. The Shp-2 mutant embryos fail to gastrulate properly as evidenced by defects in the node, notochord and posterior elongation. Biochemical analysis of mutant cells indicates that Shp-2 can function as either a positive or negative regulator of MAP kinase activation, depending on the specific receptor pathway stimulated. In particular, Shp-2 is required for full and sustained activation of the MAP kinase pathway following stimulation with fibroblast growth factor (FGF), raising the possibility that the phenotype of Shp-2 mutant embryos results from a defect in FGF-receptor signalling. Thus, Shp-2 modulates tyrosine kinase signalling in vivo and is crucial for gastrulation during mammalian development. 相似文献
115.
Nodules of faba bean (Vicia faba L. cv. Giza 3) plants grown in pots containing clay-loam soil for 90 d have an active nitrate reductase (NR), while the leaves
did not show detectable activity. Spraying the plant with increasing concentrations of Al3+ or Cd2+ (0–1000 μM) significantly inhibited the nodules NR activity, the decline being more pronounced in Cd2+ treatment. The specific activity of glutamate-oxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT) were
more prominent in the 60- than in 90-d-old plants; GOT was always higher than GPT. Furthermore, GOT was more sensitive to
Al3+ and Cd2+ treatments and its activity was significantly decreased when the metal concentration increased. Also, Cd2+ proved to be more effective than Al3+ in suppressing the GOT activity in the nodules, with less significant effect observed in the leaves. In contrast, GPT was
hardly affected by the various metal treatments, particulary in the leaves. 相似文献
116.
Haploid plantlets derived by anther culture of Cucurbita pepo 总被引:5,自引:0,他引:5
Metwally E.I. Moustafa S.A. El-Sawy B.I. Shalaby T.A. 《Plant Cell, Tissue and Organ Culture》1998,52(3):171-176
This work was conducted to study the effect of sucrose and 2,4-D combinations on induction of haploid plants of a summer squash
cultivar through anther culture; therefore, sucrose was used at 30, 60, 90, 120 and 150 g l−1and 2, 4-D was used at 0.1, 1.0, 2.5 and 5.0 mg l−1on solid MS anther culture medium. Anthers at the mid or late uninucleate microspore stage without filament were excised from
sterilized buds and plated on 20 different induction media. The most plantlets resulted from the induction medium supplemented
with 150 g l−1sucrose and 5 mg l−12, 4-D. Root tips from 20 plantlets were cytologically examined under a light microscope. The results revealed ten diploid
(2n>= 2x= 40) and ten haploid (2n= x= 20) plants.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
117.
Production of haploid plants from in vitro culture of unpollinated ovules of Cucurbita pepo 总被引:9,自引:0,他引:9
Metwally E.I. Moustafa S.A. El-Sawy B.I. Haroun S.A. Shalaby T.A. 《Plant Cell, Tissue and Organ Culture》1998,52(3):117-121
Ovaries from squash plants (cv. Eskandarani) were picked one day before anthesis, and exposed to cold temperature (4 °C) for
0, 2, 4 and 8 days. The ovules were cultured on MS medium with 30 g l−1sucrose, 8 g l−1agar and supplemented with four concentrations of 2,4-D, i.e., 0.1, 1.0, 5 and 10 mg l−1. Then the dishes were incubated at 25 ± 1 °C under 16-h photoperiod for 4 weeks. After that ovules were transferred to growth
regulator free MS medium for 4 weeks. Data indicated that the most plantlets per 100 cultured ovules resulted from the ovule
of ovaries without cold treatment, when cultured in MS medium supplemented with 1 or 5 mg l−12,4-D. The cytological study revealed that one third of examined plants were haploid (2n = x = 20) and the others were double
haploid (2n = 2x = 40).
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
118.
Enhanced Chemotherapeutic Behavior of Open‐Caged DNA@Doxorubicin Nanostructures for Cancer Cells
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119.
120.