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  • 1
    Publication Date: 2003-10-18
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Evsikov, Alexei V -- Solter, Davor -- New York, N.Y. -- Science. 2003 Oct 17;302(5644):393; author reply 393.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/14563991" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Embryo, Mammalian/*cytology ; Expressed Sequence Tags ; *Gene Expression ; Gene Expression Profiling ; Genes ; Hematopoietic Stem Cells/*physiology ; Mice ; Neurons/*cytology ; Oligonucleotide Array Sequence Analysis ; Stem Cells/*physiology ; *Transcription, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2003-08-29
    Description: The elaboration of a physiologically integrated organism from a fertilized egg depends on processes of cellular growth and diversification that require very precise coordination in both space and time. The extent to which the final outcome is presaged in the egg is an issue that has engaged those seeking to explain embryonic development since antiquity. According to the concept of preformation espoused by Charles Bonnet, the new organism was already present in its final form in the egg, so that development simply entailed enlargement without any accompanying increase in complexity (Oppenheimer 1967). This extreme view was shown to be untenable by Caspar Friedrich Wolff, whose relevant studies included careful documentation of the emergence of increasingly complex organization during the course of embryogenesis in the chick. As a result, the opposing concept of epigenesis, namely that order and form emerge de novo during the course of development, rapidly gained dominance (Oppenheimer 1967). However, by the latter half of the nineteenth century, preformation was revived in a subtler guise to explain the development of various marine invertebrates in which both patterns of cleavage and differentiation of the resulting blastomeres were essentially invariant. Here, cellular diversification was attributed to the localization within the cytoplasm of the egg of factors, or ‘determinants’, which dictated the fate of the cells that inherited them. The stereotypical pattern of cleavage exhibited by such organisms was referred to as ‘mosaic’, in contrast to the variable or ‘regulative’ pattern shown by many others. Mosaic soon came to be equated with a determinant–based or neo–preformationist, and regulative with an epigenetic, view of development. We now know that this distinction is not valid because cellular interactions play a vital part in the development even of organisms with invariant lineage like Caenorhabditis elegans, whereas ‘determinants’ such as those for the germline occur in species whose lineage is variable.
    Print ISSN: 0962-8436
    Electronic ISSN: 1471-2970
    Topics: Biology
    Published by The Royal Society
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