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排序方式: 共有113条查询结果,搜索用时 31 毫秒
1.
Changes in the distribution of a spectrin-like protein during development of the preimplantation mouse embryo 总被引:4,自引:4,他引:0
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The mouse blastocyst expresses a 240,000-mol-wt polypeptide that cross-reacts with antibody to avian erythrocyte alpha-spectrin. Immunofluorescence localization showed striking changes in the distribution of the putative embryonic spectrin during preimplantation and early postimplantation development. There was no detectable spectrin in either the unfertilized or fertilized egg. The first positive reaction was observed in the early 2-cell stage when a bright band of fluorescence delimited the region of cell-cell contact. The blastomeres subsequently developed continuous cortical layers of spectrin and this distribution was maintained throughout the cleavage stages. A significant reduction in fluorescence intensity occurred before implantation in the apical region of the mural trophoblast and the trophoblast outgrowths developed linear arrays of spectrin spots that were oriented in the direction of spreading. In contrast to the alterations that take place in the periphery of the embryo, spectrin was consistently present in the cortical cytoplasm underlying regions of contact between the blastomeres and between cells of the inner cell mass. The results suggest a possible role for spectrin in cell-cell interactions during early development. 相似文献
2.
On the ultrastructure of hyalin, a cell adhesion protein of the sea urchin embryo extracellular matrix
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Hyalin is a large (ca. 350 x 10(3) kD by gel electrophoresis) molecule that contributes to the hyalin layer surrounding the sea urchin embryo. In previous work a mAb (McA Tg-HYL), specific for hyalin, was found to inhibit cell-hyalin adhesion and block morphogenesis of whole embryos (Adelson, D. L., and T. D. Humphreys. 1988. Development. 104:391-402). In this report, hyalin ultrastructure was examined via rotary shadowing. Hyalin appeared to be a filamentous molecule approximately 75-nm long with a globular "head" about 12 nm in diameter that tended to form aggregates by associating head to head. Hyalin molecules tended to associate with a distinct high molecular weight globular particle ("core"). In fractions containing the core particle often more than one hyalin molecule were seen to be associated with the core. The core particle maintained a tenacious association with hyalin throughout purification procedures. The site(s) of McA Tg-HYL binding to the hyalin molecule were visualized by decorating purified hyalin with the antibody and then rotary shadowing the complex. In these experiments, McA Tg-HYL attached to the hyalin filament near the head region in a pattern suggesting that more than one antibody binding site exists on the hyalin filament. From the ultrastructural data and from the cell adhesion data presented earlier we conclude that hyalin is a filamentous molecule that binds to other hyalin molecules and contains multiple cell binding sites. Attempts were made to demonstrate the existence of lower molecular weight hyalin precursors. Whilst no such precursors could be identified by immunoprecipitation of in vivo labeled embryo lysates, immunoprecipitation of in vitro translation products suggested such precursors (ca 40 x 10(3) kD) might exist. 相似文献
3.
Patterns of Root Colonization in Epacridaceous Plants Collected from Different Sites 总被引:2,自引:0,他引:2
Root colonization was studied in ten species of the Epacridaceaeat three sites in Victoria by morphological and cross-inoculationexperiments. The sites and genera chosen were Cranbourne [Epacrisimpressa Labill. andLeucopogon ericoides(Smith) R. Br.] andRye [L. parviflorus(Andrews) Lindley] on the Mornington Peninsula,and the Grampians[Astroloma conostephioides(Sond.) Benth.,A.humifusum(Cav.) R. Br.,A pinifolium(R. Br.) Benth,Brachylomadaphnoides(Smith) Benth.,E. impressa, E. impressavar.grandifloraBenth.andStyphelia adscendensR. Br.] in western Victoria. For morphologicalstudies, samples of roots from each species at each site werecleared and stained and examined microscopically. For cross-inoculationstudies, cuttings from each site were struck in potting mediuminoculated with soil from the same and other sites. The ericoidmycorrhizae in the roots of plants found at or grown in Cranbourneand Rye soils were similar. Both were significantly differentfrom the internal hyphae found in the roots of plants foundat or grown in Grampians soils, which were three times largerin diameter and formed dense coils which filled the host celland invaded adjacent epidermal cells. This suggests that morethan one fungus is involved in the relationships, that the MorningtonPeninsula sites had a different fungus from the Grampians siteand that host specificity is low. Vesicular structures werealso found commonly on plants at the Grampians site, in contrastwith other sites. Epacridaceae; root; fungus; mycorrhiza; morphology; inoculation 相似文献
4.
Endothelial cell proliferation is required for angiogenesis in both embryonic and adult tissues. In rat brain tumors, it has recently been shown that the nuclear protein pigpen is expressed selectively in endothelial cells of developing microvasculature but not in the established peritumoral vessels (Blank, M., Weinschenk, T., Priemer, M., and Schluesener, H. (2001) J. Biol. Chem. 276, 16464-16468). This finding suggests that pigpen may be important for promoting the undifferentiated, or "angiogenic" endothelial cell phenotype. Our studies show that pigpen protein and mRNA are expressed in actively dividing endothelial cells and down-regulated as they become confluent. Protein distribution is regulated in a cell cycle-dependent manner. We conclude that this expression pattern is important for and not simply ancillary to proliferation because nuclear microinjection of anti-pigpen Fab fragments inhibited endothelial cell division. Moreover, expression of the proliferating cell marker Ki67 was inhibited in antibody-injected cells. The absence of Ki67 suggests exit from rather than arrest within (for example, at the G(1)/S interface) the cell cycle. Together with earlier observations on the structure and expression of this molecule, our data support the hypothesis that pigpen helps regulate endothelial cell differentiation state. 相似文献
5.
Andréia S Lessa Bruno D Paredes Juliana V Dias Adriana B Carvalho Luiz Fernando Quintanilha Christina M Takiya Bernardo R Tura Guilherme FM Rezende Antonio C Campos de Carvalho Célia MC Resende Regina CS Goldenberg 《BMC veterinary research》2010,6(1):1-10
Background
Atypical scrapie was first identified in Norwegian sheep in 1998 and has subsequently been identified in many countries. Retrospective studies have identified cases predating the initial identification of this form of scrapie, and epidemiological studies have indicated that it does not conform to the behaviour of an infectious disease, giving rise to the hypothesis that it represents spontaneous disease. However, atypical scrapie isolates have been shown to be infectious experimentally, through intracerebral inoculation in transgenic mice and sheep. The first successful challenge of a sheep with 'field' atypical scrapie from an homologous donor sheep was reported in 2007.Results
This study demonstrates that atypical scrapie has distinct clinical, pathological and biochemical characteristics which are maintained on transmission and sub-passage, and which are distinct from other strains of transmissible spongiform encephalopathies in the same host genotype.Conclusions
Atypical scrapie is consistently transmissible within AHQ homozygous sheep, and the disease phenotype is preserved on sub-passage. 相似文献6.
van Beers JJ Raijmakers R Alexander LE Stammen-Vogelzangs J Lokate AM Heck AJ Schasfoort RB Pruijn GJ 《Arthritis research & therapy》2010,12(6):R219
Introduction
Rheumatoid arthritis (RA) frequently involves the loss of tolerance to citrullinated antigens, which may play a role in pathogenicity. Citrullinated fibrinogen is commonly found in inflamed synovial tissue and is a frequent target of autoantibodies in RA patients. To obtain insight into the B-cell response to citrullinated fibrinogen in RA, its autoepitopes were systematically mapped using a new methodology. 相似文献7.
8.
Sidders B Withers M Kendall SL Bacon J Waddell SJ Hinds J Golby P Movahedzadeh F Cox RA Frita R Ten Bokum AM Wernisch L Stoker NG 《Genome biology》2007,8(12):R265-13
We describe an analysis, applicable to any spotted microarray dataset produced using genomic DNA as a reference, that quantifies prokaryotic levels of mRNA on a genome-wide scale. Applying this to Mycobacterium tuberculosis, we validate the technique, show a correlation between level of expression and biological importance, define the complement of invariant genes and analyze absolute levels of expression by functional class to develop ways of understanding an organism's biology without comparison to another growth condition. 相似文献
9.
José MC Ribeiro Bruno Arcà Fabrizio Lombardo Eric Calvo My Van Phan Prafulla K Chandra Stephen K Wikel 《BMC genomics》2007,8(1):1-27
Background
The number of completely sequenced plastid genomes available is growing rapidly. This array of sequences presents new opportunities to perform comParative analyses. In comParative studies, it is often useful to compare across wide phylogenetic spans and, within angiosperms, to include representatives from basally diverging lineages such as the genomes reported here: Nuphar advena (from a basal-most lineage) and Ranunculus macranthus (a basal eudicot). We report these two new plastid genome sequences and make comparisons (within angiosperms, seed plants, or all photosynthetic lineages) to evaluate features such as the status of ycf15 and ycf68 as protein coding genes, the distribution of simple sequence repeats (SSRs) and longer dispersed repeats (SDR), and patterns of nucleotide composition.Results
The Nuphar [GenBank:NC_008788] and Ranunculus [GenBank:NC_008796] plastid genomes share characteristics of gene content and organization with many other chloroplast genomes. Like other plastid genomes, these genomes are A+T-rich, except for rRNA and tRNA genes. Detailed comparisons of Nuphar with Nymphaea, another Nymphaeaceae, show that more than two-thirds of these genomes exhibit at least 95% sequence identity and that most SSRs are shared. In broader comparisons, SSRs vary among genomes in s of abundance and length and most contain repeat motifs based on A and T nucleotides.Conclusion
SSR and SDR abundance varies by genome and, for SSRs, is proportional to genome size. Long SDRs are rare in the genomes assessed. SSRs occur less frequently than predicted and, although the majority of the repeat motifs do include A and T nucleotides, the A+T bias in SSRs is less than that predicted from the underlying genomic nucleotide composition. In codon usage third positions show an A+T bias, however variation in codon usage does not correlate with differences in A+T-richness. Thus, although plastome nucleotide composition shows "A+T richness", an A+T bias is not apparent upon more in-depth analysis, at least in these aspects. The pattern of evolution in the sequences identified as ycf15 and ycf68 is not consistent with them being protein-coding genes. In fact, these regions show no evidence of sequence conservation beyond what is normal for non-coding regions of the IR. 相似文献10.