Millipore Sigma Vibrant Logo
 

select


4745 Results Búsqueda avanzada  
Mostrar
Productos (169)
Documentos (4,236)
Páginas (340)

Acote sus resultados Utilice los filtros siguientes para refinar su búsqueda

Tipo de documento

  • (3,644)
  • (347)
  • (99)
  • (58)
  • (36)
  • Mostrar más
¿No encuentra lo que está buscando?
Póngase en contacto con
el Servicio de Atención
al Cliente

 
¿Necesita ayuda para encontrar un documento?

  • Expression of TGFβ superfamily components and other markers of oocyte quality in oocytes selected by brilliant cresyl blue staining: relevance to early embryonic developm ... 25704641

    Brilliant cresyl blue (BCB) is a super-vital stain that has been used to select competent oocytes in different species. One objective of the present study was to assess the relationship between BCB staining, which correlates with an oocyte's developmental potential, and the transcript abundance for select TGFβ-superfamily components, SMAD2/3 and SMAD1/5 phosphorylation levels, and oocyte (JY1) and cumulus-cell (CTSB, CTSK, CTSS, and CTSZ) transcript markers in bovine oocytes and/or adjacent cumulus cells. The capacity of exogenous follistatin or JY1 supplementation or cathepsin inhibitor treatment to enhance development of embryos derived from low-quality oocytes, based on BCB staining, was also determined. Cumulus-oocyte complexes (COCs) from abattoir-derived ovaries were subjected to BCB staining, and germinal-vesicle-stage oocytes and cumulus cells were harvested from control, BCB+, and BCB- (low-quality oocyte) groups for real-time PCR or Western-blot analysis. Remaining COCs underwent in vitro maturation, in vitro fertilization, and embryo culture in the presence or absence of the above exogenous supplements. Levels of FST, JY1, BMP15, and SMAD1, 2, 3, and 5 transcripts were higher in BCB+ oocytes whereas CTSB, CTSK, CTSS, and CTSZ mRNA abundance was higher in cumulus cells surrounding BCB- oocytes. Western-blot analysis revealed higher SMAD1/5 and SMAD2/3 phosphorylation in BCB+ than BCB- oocytes. Embryo-culture studies demonstrated that follistatin and cathepsin inhibitor treatment, but not JY-1 treatment, improve the developmental competence of BCB- oocytes. These results contribute to a better understanding of molecular indices of oocyte competence.
    Tipo de documento:
    Referencia
    Referencia del producto:
    MAB1501
    Nombre del producto:
    Anti-Actin Antibody, clone C4

  • Initiation of translation in prokaryotes and eukaryotes. 10395892

    The mechanisms whereby ribosomes engage a messenger RNA and select the start site for translation differ between prokaryotes and eukaryotes. Initiation sites in polycistronic prokaryotic mRNAs are usually selected via base pairing with ribosomal RNA. That straightforward mechanism is made complicated and interesting by cis- and trans-acting elements employed to regulate translation. Initiation sites in eukaryotic mRNAs are reached via a scanning mechanism which predicts that translation should start at the AUG codon nearest the 5' end of the mRNA. Interest has focused on mechanisms that occasionally allow escape from this first-AUG rule. With natural mRNAs, three escape mechanisms - context-dependent leaky scanning, reinitiation, and possibly direct internal initiation - allow access to AUG codons which, although not first, are still close to the 5' end of the mRNA. This constraint on the initiation step of translation in eukaryotes dictates the location of transcriptional promoters and may have contributed to the evolution of splicing.The binding of Met-tRNA to ribosomes is mediated by a GTP-binding protein in both prokaryotes and eukaryotes, but the more complex structure of the eukaryotic factor (eIF-2) and its association with other proteins underlie some aspects of initiation unique to eukaryotes. Modulation of GTP hydrolysis by eIF-2 is important during the scanning phase of initiation, while modulating the release of GDP from eIF-2 is a key mechanism for regulating translation in eukaryotes. Our understanding of how some other protein factors participate in the initiation phase of translation is in flux. Genetic tests suggest that some proteins conventionally counted as eukaryotic initiation factors may not be required for translation, while other tests have uncovered interesting new candidates. Some popular ideas about the initiation pathway are predicated on static interactions between isolated factors and mRNA. The need for functional testing of these complexes is discussed.Interspersed with these theoretical topics are some practical points concerning the interpretation of cDNA sequences and the use of in vitro translation systems. Some human diseases resulting from defects in the initiation step of translation are also discussed.
    Tipo de documento:
    Referencia
    Referencia del producto:
    07-760
    Nombre del producto:

  • FGF stimulation of the Erk1/2 signalling cascade triggers transition of pluripotent embryonic stem cells from self-renewal to lineage commitment. 17660198

    Pluripotent embryonic stem (ES) cells must select between alternative fates of self-replication and lineage commitment during continuous proliferation. Here, we delineate the role of autocrine production of fibroblast growth factor 4 (Fgf4) and associated activation of the Erk1/2 (Mapk3/1) signalling cascade. Fgf4 is the major stimulus activating Erk in mouse ES cells. Interference with FGF or Erk activity using chemical inhibitors or genetic ablations does not impede propagation of undifferentiated ES cells. Instead, such manipulations restrict the ability of ES cells to commit to differentiation. ES cells lacking Fgf4 or treated with FGF receptor inhibitors resist neural and mesodermal induction, and are refractory to BMP-induced non-neural differentiation. Lineage commitment potential of Fgf4-null cells is restored by provision of FGF protein. Thus, FGF enables rather than antagonises the differentiation activity of BMP. The key downstream role of Erk signalling is revealed by examination of Erk2-null ES cells, which fail to undergo either neural or mesodermal differentiation in adherent culture, and retain expression of pluripotency markers Oct4, Nanog and Rex1. These findings establish that Fgf4 stimulation of Erk1/2 is an autoinductive stimulus for naïve ES cells to exit the self-renewal programme. We propose that the Erk cascade directs transition to a state that is responsive to inductive cues for germ layer segregation. Consideration of Erk signalling as a primary trigger that potentiates lineage commitment provides a context for reconciling disparate views on the contribution of FGF and BMP pathways during germ layer specification in vertebrate embryos.
    Tipo de documento:
    Referencia
    Referencia del producto:
    AB5603
    Nombre del producto:
    Anti-Sox2 Antibody