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  • 1
    ISSN: 1432-041X
    Keywords: Key words Cell potency ; Lineage differentiation ; Genomic imprinting ; Parthenogenetic embryos ; Chimaeras
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The developmental potential of parthenogenetic embryonic stem (P-ES) cells was studied in teratomas and mouse chimaeras. Teratomas derived from P-ES cells contained a mixture of tissue types with variable proportions of specific tissues. Three of the eight P-ES cell lines analysed showed high proportions of striated muscle in teratomas, similar to teratomas from normal embryos or ES cell lines derived from fertilised embryos (F-ES cells). Our study also revealed that one P-ES cell line showed little lineage restriction in injection chimaeras. Descendants of the P-ES cells contributed to most tissues of chimaeric fetuses in patterns similar to F-ES cells. Normal colonisation of muscle, liver and pancreas was found in adult chimaeras. P-ES cells also showed similar haematopoietic differentiation and maturation as F-ES cells. However, extensive P-ES cell contribution was associated with a reduction in body size. These findings suggest that, while P-ES cells display more extensive developmental potential than the cells of parthenogenetic embryos from which they were derived, they only retained properties related to the presence of the maternal genome. To elucidate the molecular basis for the lack of lineage restriction during in vivo differentiation, the expression of four imprinted genes, H19, Igf2r, Igf2 and Snrpn was compared among five P-ES and two F-ES cell lines. Expression levels of these genes varied among the different ES cell lines, both in undifferentiated ES cells and in embryoid bodies.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 417 (2002), S. 605-606 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] For more than a decade, the interneurons found in the neocortex of the human brain have been disturbing the peace of developmental neurobiologists. Interneurons represent roughly 20% of cortical neurons and are responsible for modulating the firing of the principal neurons known as projection ...
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Previously we have shown that leukaemia inhibitory factor (LIF) potentiates the development of murine spinal cord neurons in vitro, suggesting that it, or related factors, may play an important regulatory role in neuronal development. We have further investigated this role and show here that the generation of neurons in cultures of embryonic day 10 spinal cord cells is inhibited by antibodies to the β subunit of the LIF receptor. Since there are more undifferentiated precursors in antibody-treated cultures than in control and LIF-treated cultures, it is concluded that the primary action of LIF, or related molecules, is to promote neuronal differentiation, not precursor survival. In addition, the failure of LIF to support neuronal survival in the period immediately following differentiation suggests that the increased numbers of neurons generated with LIF are not attributable to its neurotrophic action. By selecting neuronal precursors on the basis of their inability to express class I major histocompatibility complex molecules, it was shown that LIF acted directly upon these cells and not via an intermediary cell. LIF also appears to be involved in regulating the differentiation of astrocytes, since it increases the number of glial fibrillary protein (GFAP)-positive cells present in the cultures and since the spontaneous production of GFAP-positive cells is blocked by antibodies to the LIF β receptor. These findings suggest that LIF or related factors promote the differentiation of neural precursors in the spinal cord, but that they are not involved in preferentially promoting precursors down a specific differentiation pathway.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Tissue-type plasminogen activator (t-PA) participates in the control of synaptic plasticity and memory formation in the central nervous system (CNS). Transgenic mice harbouring either 9.5, 3.0 or 1.4 kb of the human t-PA promoter fused to the LacZ reporter gene were used to assess t-PA promoter-directed expression in vivo. The 9.5 kb t-PA promoter directed expression to the brain, most notably to the dentate gyrus, superior colliculus, hippocampus, thalamus and piriform cortex. Staining was also observed in the retrosplenial and somatosensory cortex. The 3.0 kb t-PA promoter directed generalized and poorly defined expression to the cortex and hippocampus, while the 1.4 kb t-PA promoter directed expression selectively to the medial habenula. Intravenous administration of lipopolysaccharide into mice habouring the 9.5 kb t-PA promoter resulted in an increase in reporter gene activity in the lateral orbital cortex and thalamus. Results of in vitro transfection experiments of NT2 cells with a series of t-PA promoter deletion constructs confirmed the presence of regulatory elements throughout the 9.5 kb promoter region. Finally, we describe a cis-acting element related to the NFAT recognition site that provides a protein-binding site and which may play a role in the selective expression of the 1.4 t-PA promoter in the medial habenula. These results indicate that elements between −3.0 and −9.5 kb of the t-PA promoter confer constitutive and inducible expression to specific regions of the CNS.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 11 (1999), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The granular layer of the developing and adult cerebellum is marked by the presence of several transverse boundaries, revealed in gene expression patterns or as a consequence of genetic mutations. It is unclear whether these boundaries represent fundamental differences between granule cell populations or if they are a secondary response to regional differences in the underlying Purkinje cells. One possibility is that boundaries mark different spatial domains of granule cells in a lineage-dependent fashion. To test this hypothesis, we have analysed a series of murine embryonic stem cell chimeras marked by the constitutive expression of β-galactosidase in donor granule cells. The chimeras show a consistent spatial restriction boundary, located in the granular layer of lobule VI in the vermis and extending laterally into crus I of the hemispheres. A second boundary was found separating lobules IX and X in the vermis. No correlation was found between the genotypes of molecular layer interneurons and the underlying granule cells, suggesting that they arise independently. No transverse boundaries were observed for the molecular layer interneurons, consistent with the hypothesis that they are not generated from precursors in the external granular layer. These results indicate that the granular layer of the cerebellum comprises cellular domains with different histories separated by consistent spatial restriction boundaries.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    European journal of neuroscience 10 (1998), S. 0 
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The cerebellar cortex is subdivided into an elaborate, stereotyped array of transverse zones and parasagittal stripes. It has been speculated that (i) all Purkinje cells derive from 10 to 20 precursors allocated early in embryogenesis and (ii) that pattern formation is based on cell lineage restriction in the founder pool. These hypotheses have been tested by clonal analysis of embryonic stem cell chimeras. Neither speculation is supported: the analysis suggests that Purkinje cells derive from a founder population of 〉 102 precursors, and that neither cerebellar transverse developmental boundaries nor parasagittal stripes have a clonal origin. We conclude that early lineage restriction plays no role in cerebellar pattern formation.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature genetics 3 (1993), S. 170-174 
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] During mammalian development, one of the two X chromosomes in female embryos is randomly inactivated in the somatic cell in order to achieve gene dosage compensation. But is X inactivation established simultaneously or is it accomplished over time in a lineage–dependent fashion? We have ...
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 362 (1993), S. 638-640 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We used transgenic mice for marking progenitor cells with /acZ-encoded /3-galactosidase, and a genetic mechanism (X-chromosome inactivation) for switching off the gene in half of these cells, generating a functional genetic mosaicism11 (Fig. 1). X inactivation is fully completed by day 12.5 of ...
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 240 (1985), S. 403-416 
    ISSN: 1432-0878
    Keywords: Cranial neural crest ; Emigration ; Rat embryo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The head region of rat embryos was investigated by scanning electron microscopy after removal of the surface ectoderm with adhesive tape. Observations were made in embryos from 6-somite to 11-somite stages of development, in order to determine: (1) the sequence of emigration of neural crest cells from the different regions of the future brain; (2) the appearance of crest cells before, during, and after their conversion from an epithelial to a mesenchymal form; (3) the migration pathways. Emigration occurs first from the midbrain, and next from the rostral hindbrain; crest cells from these two regions migrate into the first visceral arch. Subsequently cells emigrate from the caudal hindbrain, but not in a rostrocaudal sequence. At the time of crest cell emigration, the neural fold morphology varies from a slightly convex, widely open plate (midbrain) to a closed tube (caudal hindbrain). Thus the timing of emigration is related neither to age (as reflected in rostrocaudal levels) nor to morphology of the neural epithelium.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 0192-253X
    Keywords: X chromosome ; X inactivation ; lacZ transgene ; cell lineage ; mouse embryo ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: X-chromosome activity in female mouse embryos was studied at the cellular level using an X-linked lacZ transgene which encodes β-galactosidase (β-Gal). Translation of maternal RNA in oocytes is seen as β-Gal activity that persists into early cleavage-stages. Zygotic transcription of the transgene from the maternal X chromosome (Xm) is first found at about the 8-cell stage. By contrast, expression of the lacZ transgene on the paternal X chromosome (Xp) is not seen until later at the 16-32-cell stage. Preferential inactivation of Xp occurs in the mural trophectoderm, the primitive endoderm, and derivatives of the polar trophectoderm, but a small number of cells in these lineages may still retain an active paternal X chromosome. X inactivation begins at 3.5 days in the inner cell mass but contrary to previous findings the process is not completed in the embryonic ectoderm by 5.5 to 6.0 days. Regional variation in β-Gal activity is also observed in the embryonic ectoderm during gastrulation which may be related to the specification of cell fates. Random inactivation of Xp and Xm ensues in all somatic tissues but the process is completed at different times in different tissues. The slower progression of X inactivation in tissues such as the notochord, the heart, and the embryonic gut is primarily due to the persistent maintenance of two active X chromosomes in a significant fraction of cells in these tissues. Recent findings on the methylation of endogenous X-linked genes suggest that the prolonged expression of β-Gal might also be due to the different rate of spreading of inactivation along the X chromosome to the lacZ transgene locus in different tissues. © 1994 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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