نتایج جستجو برای: early cleavage
تعداد نتایج: 729833 فیلتر نتایج به سال:
The ascidian embryo is an ideal system to investigate how cell position is determined during embryogenesis. Using 3D timelapse imaging and computational methods we analyzed the planar cell divisions in ascidian early embryos and found that spindles in every cell tend to align at metaphase in the long length of the apical surface except in cells undergoing unequal cleavage. Furthermore, the inva...
Only 25 to 30% of conceptions result in a live birth. There is mounting evidence that the cause for this low fecundity is an extremely high incidence of chromosomal rearrangements occurring in the cleavage stage embryo. In this review, we gather all recent evidence for an extraordinary degree of mosaicisms in early embryogenesis. The presence of the rearrangements seen in the cleavage stage emb...
Sex determination in mammals has been defined as those events that fix the nature of the germ cell and the gonad, while other processes influencing sexual form and function such as hormone action constitute sex differentiation (Austin et al., 1981). Such determination involves the separation of germline and soma, controlled initially by maternal genes and then by the zygotic genome after fertil...
Telomerase RNA (TER) is an essential component of the telomerase ribonucleoprotein complex. The mechanism for TER 3'-end processing is highly divergent among different organisms. Here we report a unique spliceosome-mediated TER 3'-end cleavage mechanism in Neurospora crassa that is distinct from that found specifically in the fission yeast Schizosaccharomyces pombe. While the S. pombe TER intro...
‘l’l~e SWYW EcoKI restriction endonuclease cleavage sites in bacteriophage P%d DNA have been mapped. The cleavage site map of circularly permut.ed P22 linear DNA is a circle. The positions of EcoRI sites in the early region of the P22 genomc were determined by comparing products of EcoRI digestion of maturtx liaear P22 chromosomes with the EcoRI cleavage fragments of DNA of three XimmP22 hybrid...
Inverted amphibian embryos were employed for an analysis of pattern formation in early embryogenesis. Axolotl (Ambystoma) and Xenopus eggs were inverted prior to the first cleavage division and permitted to develop upside down to the early gastrulation stage. In both cases the cleavage patterns of the animal and vegetal hemispheres were reversed. By gastrulation, however, developmental arrest b...
a simple, efficient and clean procedure has been developed for the cleavage of imines c=n bond. deprotection of imines to their parent carbonyl and amine compounds was achieved using p-toluenesulfonic acid in the solid state condition at 25-45 ˚c. the salient features of this methodology are shorter reaction times, cheap processing, high yields of product and easy availability of the catalyst. ...
few novel cobalt(ii) and copper(ii) complexes [m(fmp)3]cl2, [m(fmp)(bpy)2]cl2,[m(fmp)(phen)2]cl2 and [m(fmp)(phen)(bpy)]cl2 (fmp = 3-furan-2-ylmethylene-pentane-2,4-dione, phen = 1,10-phenanthroline, bpy = 2,2'-bipyridine) have been synthesized andcharacterized by elemental analyses, molar conductance, magnetic susceptibility measurements,ir, electronic, epr, mass spectra and cyclic voltam...
BACKGROUND Orientation and positioning of the cell division plane are essential for generation of invariant cleavage patterns and for unequal cell divisions during development. Precise control of the division plane is important for appropriate partitioning of localized factors, spatial arrangement of cells for proper intercellular interactions, and size control of daughter cells. Ascidian embry...
Posttranscriptional maturation of the 3' end of eukaryotic pre-mRNAs occurs as a three-step pathway involving site-specific cleavage, polymerization of a poly(A) tail, and trimming of the newly synthesized tail to its mature length. While most of the factors essential for catalyzing these reactions have been identified, those that regulate them remain to be characterized. Previously, we demonst...
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