In fertilized eggs of Xenopus laevis a marked flattening of the pigmented animal hemisphere has been observed. The flattening begins 15-20 minutes before the appearance of the cleavage furrow. As the furrow develops, the pigmented surface relaxes and rounds up. The initial appearance of the furrow is thus shown to be a combination of furrow deepening and rounding up of adjacent pigmented surfac...

I-SceI is a homing endonuclease that specifically cleaves an 18-bp double-stranded DNA. I-SceI exhibits a strong preference for cleaving the bottom strand DNA. The published structure of I-SceI bound to an uncleaved DNA substrate provided a mechanism for bottom strand cleavage but not for top strand cleavage. To more fully elucidate the I-SceI catalytic mechanism, we determined the X-ray struct...

We developed several novel tools to genome wide screen for CNVs and SNPs in single cells. When applied to cleavage stage embryos from young fertile couples we discovered, unexpectedly, an extremely high incidence of chromosomal instability, a hallmark of tumorigenesis (Vanneste et al., Nature Medicine, 2009; Vanneste et al., Hum.Reprod., 2011). Not only mosaicisms for whole chromosome aneuploid...

Background: Parthenogenetic activation is a possible way to produce homogeneous embryos with the some ploidy. Probably such embryos could be used in other areas of biotechnology. Calcium signals are known as important regulators of oocyte activation. Extracellular calcium is required for initiation of meiotic resumption and development. Calcium ionophore A23187 is known to elevate intracellular...

a study was conducted to investigate the effect of follicular size (small,

the zinc(ii) complex [zn2(dmdtc)2(μ-dmdtc)2] has been synthesized directly from thiram ligand, containing a disulfide bond {dmdtc = n,n-dimethyldithiocarbamate; thiram = n,n-tetramethylthiuram disulfide}, and characterized by elemental analysis and spectroscopic methods. surprisingly thiram, undergoes a reductive disulfide bond scission upon reaction with zn2+ in methanolic media to give the [z...

Cytokinesis is the essential process that partitions cellular contents into daughter cells. To identify and characterize cytokinesis proteins rapidly, we used a functional proteomic and comparative genomic strategy. Midbodies were isolated from mammalian cells, proteins were identified by multidimensional protein identification technology (MudPIT), and protein function was assessed in Caenorhab...

We recently used in vitro selection to identify many deoxyribozymes that catalyze DNA phosphodiester bond hydrolysis and create 5'-phosphate and 3'-hydroxyl termini. Alternatively, numerous deoxyribozymes have been identified for catalysis of RNA cleavage by 2'-hydroxyl transesterification, forming 2',3'-cyclic phosphate and 5'-hydroxyl termini. In this study, we investigated the ability of DNA...

The value of k(cat)/K(M) for catalysis of RNA cleavage by ribonuclease (RNase) A can exceed 10(9) M(-1) s(-1) in a solution of low salt concentration. This value approaches that expected for the diffusional encounter of the enzyme and its substrate. To reveal the physicochemical constraints upon catalysis by RNase A, the effects of salt concentration, pH, solvent isotope, and solvent viscosity ...

In metazoans, cleavage by the endoribonuclease SMG6 is often the first degradative event in non-sense-mediated mRNA decay (NMD). However, the exact sites of SMG6 cleavage have yet to be determined for any endogenous targets, and most evidence as to the identity of SMG6 substrates is indirect. Here, we use Parallel Analysis of RNA Ends to specifically identify the 5' termini of decay intermediat...