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排序方式: 共有470条查询结果,搜索用时 15 毫秒
1.
Partial purification of the maturation-promoting factor MPF from unfertilized eggs of Xenopus laevis 总被引:5,自引:0,他引:5
P Nguyen-Gia M Bomsel J P Labrousse C L Gallien H Weintraub 《European journal of biochemistry》1986,161(3):771-777
A 200-fold purification of the maturation-promoting factor or MPF from unfertilized eggs of Xenopus laevis is reported for the first time. Purification was achieved by three successive column chromatographies on hydroxyapatite, trisacryl blue and L-arginine-agarose. The presence of MPF was assessed by the usual maturation criteria after injections of test material into immature stage VI unstimulated X. laevis oocytes: the precocious appearance of the maturation spot (within 45-120 min), the germinal vesicle breakdown, the presence of the first polar body and the second metaphase spindle. Purification was monitored by the decrease of the minimal amount of protein injected in a constant volume (50 nl) required to induce 50% frequency of germinal vesicle breakdown. This amount decreased from 500 ng in the crude extract to 2.5 ng in the 200-fold purified material. Analysis by SDS-PAGE of the crude extract showed about 40 Coomassie-blue-stained polypeptides with molecular masses ranging from 300 kDa to 20 kDa, whereas in the 200-fold purified MPF only 5 stained polypeptides were revealed, with molecular masses of 62, 53, 49, 39 and 37 kDa. In vitro phosphorylations for the detection of kinase activities for endogenous and exogenous substrates were monitored by analysis of autoradiograms of SDS-PAGE, after treatment of fractions with [gamma-32P]ATP. Only inactive fractions eluted from columns ahead of MPF, and fractions containing MPF activity were tested. Phosphorylation of numerous stained polypeptides was demonstrated in the crude MPF extract and exogenous substrates such as phosvitin, casein and histone type II-AS were also strongly phosphorylated. In the MPF fraction, purified on hydroxyapatite, a polypeptide of 53 kDa was more highly and specifically phosphorylated and the presence of kinase activities was observed for the above three exogenous substrates. In the 100-fold and 200-fold purified MPF, phosphorylation of endogenous substrates could not be shown and kinase activities for the above three substrates were drastically decreased as compared with the crude and purified MPF obtained after hydroxyapatite column chromatography. However, neither endogenous phosphorylations nor kinase activities with the above exogenous substrates could be shown in inactive fractions eluted ahead of MPF at the different purification steps. Some characteristics of the purified material are also described in this paper. 相似文献
2.
Jeff A Johnson Heather RL Lerner Pamela C Rasmussen David P Mindell 《BMC evolutionary biology》2006,6(1):65-12
Background
Populations of the Oriental White-backed Vulture (Gyps bengalensis) have declined by over 95% within the past decade. This decline is largely due to incidental consumption of the non-steroidal anti-inflammatory veterinary pharmaceutical diclofenac, commonly used to treat domestic livestock. The conservation status of other Gyps vultures in southern Asia is also of immediate concern, given the lack of knowledge regarding status of their populations and the continuing existence of taxonomic uncertainties. In this study, we assess phylogenetic relationships for all recognized species and the majority of subspecies within the genus Gyps. The continuing veterinary use of diclofenac is an unknown but potential risk to related species with similar feeding habits to Gyps bengalensis. Therefore, an accurate assessment of the phylogenetic relationships among Gyps vultures should aid in their conservation by clarifying taxonomic uncertainties, and enabling inference of their respective relatedness to susceptible G. bengalensis. 相似文献3.
4.
The O-antigen polysaccharide of the lipopolysaccharide from the enteroaggregative Escherichia coli strain 62D1 has been determined. Sugar and methylation analysis together with 1H and 13C NMR spectroscopy revealed the components of the repeating unit. Two-dimensional NOESY and heteronuclear multiple-bond correlation experiments were used to deduce the sequence. 1H and 13C NMR spectra indicate heterogeneity in the polysaccharide. Methylation analysis and 1H NMR spectra of native and Smith-degraded material show that the majority (65%) of the repeating units has the following structure: Minor resonances in the NMR spectra are consistent with the presence of repeating units which lack the alpha-d-Galp terminal residue (35%). 相似文献
5.
6.
Alterations in the sialylation and sulfation of secreted mouse thyrotropin in primary hypothyroidism 总被引:1,自引:0,他引:1
G S DeCherney N Gesundheit P W Gyves C R Showalter B D Weintraub 《Biochemical and biophysical research communications》1989,159(2):755-762
We investigated the effect of in vivo hypothyroidism on the sialylation and sulfation of thyroid-stimulating hormone (TSH) secreted by mouse pituitary explants. Oligosaccharides from secreted thyroid-stimulating hormone from hypothyroid animals contained greater sialic acid relative to sulfate in both alpha and beta subunits. Aging per se had little effect on thyroid-stimulating hormone sialylation or sulfation. Variable sialylation and sulfation demonstrates a mechanism for charge microheterogeneity of thyroid-stimulating hormone, and the increasing sialylation observed with hypothyroidism may functionally mediate the prolonged metabolic clearance that has been noted previously. 相似文献
7.
8.
X H Huang M Bomsel C de Paillerets H Weintraub A Alfsen 《Comptes rendus de l'Académie des sciences. Série III, Sciences de la vie》1987,304(18):465-468
Coated vesicles, essential organelles of intracellular membrane traffic, have been extensively studied in animal and higher plant cells. In the algae, cytological studies only have been performed which demonstrate the presence of such coated vesicles with their surrounding clathrin lattice. The present work has been carried out on coated vesicles isolated for the first time from the brown algae Laminaria digitata. For comparison of the antigenic characteristics of clathrin prepared from the Bovine brain or adrenocortical cells and the clathrin prepared from algae, polyclonal antibodies have been raised to a purified Bovine brain clathrin in Goat and to Bovine adrenocortical clathrin in Rabbit. The positive immunological responses of the coated vesicles and the clathrin from Algae to these antibodies, evidence an homology between antigenic determinants of clathrin from animal and vegetal cells. 相似文献
9.
Zenon Steplewski K. Ann Jeglum Carlos Rosales Nancy Weintraub 《Cancer immunology, immunotherapy : CII》1987,24(3):197-201
Summary Lymphoma in dogs resembles human non-Hodgkin's lymphoma in pathological presentation, immunophenotype, and response to therapy, thus representing a good model for comparative studies with human disease. Monoclonal antibodies (MAbs) were derived from mice immunized with a dog lymphoma cell line. Three MAbs were selected for further application in immunophenotyping and immunotherapy. The binding specificities, antigen characterization, and isotypes for these MAbs are described.Supported by NCI grant CA-10815 相似文献
10.