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  • 1
    Electronic Resource
    Electronic Resource
    Induction of Myofibrillogenesis in Cardiac Mutant Axolotls by RNA from Normal Embryonic Endoderm (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 588 (1990), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1990.tb13247.x
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  • 2
    Electronic Resource
    Electronic Resource
    Abnormalities in Myofibril Organization and Cell Shape in Developing Cardiomyopathic Hamster Heart Cells in Culture (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 588 (1990), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1990.tb13248.x
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  • 3
    Electronic Resource
    Electronic Resource
    Immunohistochemical Localization of Gap Junction Protein Channels in Hamster Sinoatrial Node in Correlation with Electrophysiologic Mapping of the Pacemaker Region (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 5 (1994), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Gap Junction Proteins in the Sinoatrial Node. Introduction: Gap junction proteins are thought to form the low resistance pathways that connect neighboring cells within the sinoatrial node, and to mediate pacemaker synchronization. Methods and Results: We have carried out microelectrode mapping experiments of the hamster sinoatrial region to localize the primary pacemaker area for subsequent light, electron, and immunofluorescence microscopic studies aimed at testing the hypothesis that the major cardiac gap junction protein (connexin43) is present in such an area. The site of earliest activation is unifocal and the pattern of activation, obtained In multiple sequential microelectrode recordings of the Sinoatrial region, is qualitatively similar to that previously described for other species. However, quantitatively, the impulse transmission time from the primary pacemaker area to the crista (sulcus) terminal's in the hamster sinoatrial node is about 50% briefer than that of the guinea pig and five times faster than that of the rabbit. Immunolocalization studies in the hamster sinoatrial node using anti-connexin43 antisera demonstrated specific staining at the areas of cell-to-cell apposition and suggested that the apparently high degree of electrical coupling in this tissue is the result of abundant connexin43 expression. The immunofluorescence data were supported by light microscopic studies, which demonstrated the typical morphologic characteristics of sinus nodal cells in the pacemaker area. In addition, an electron microscopic study of the sinoatrial region revealed the presence of gap junctions in the junctional complex at areas of cell-to-cell contact. Conclusion: Our results demonstrate that cells in the sinoatrial region of the hamster heart are electrically well coupled and strongly suggest that such coupling is mediated by gap junctional channels formed by connexin43.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1994.tb01152.x
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  • 4
    Electronic Resource
    Electronic Resource
    Expression of axolotl RNA-binding protein during development of the Mexican axolotl (1999)
    Springer
    Cell & tissue research 297 (1999), S. 283-290 
    Details
    ISSN: 1432-0878
    Keywords: Key words RNA-binding domain ; Reverse transcriptase-polymerase chain reaction ; Northern blot analysis ; In situ hybridization ; Amphibian development ; Ambystoma mexicanum (Urodela)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Amphibians occupy a central position in phylogeny between aquatic and terrestrial vertebrates and are widely used as model systems for studying vertebrate development. We have undertaken a comprehensive molecular approach to understand the early events related to embryonic development in the Mexican axolotl, Ambystoma mexicanum, which is an exquisite animal model for such explorations. Axolotl RBP is a RNA-binding protein which was isolated from the embryonic Mexican axolotl by subtraction hybridization and was found to show highest similarity with human, mouse, and Xenopus cold-inducible RNA-binding protein (CIRP). The reverse transcriptase polymerase chain reaction (RT-PCR) analysis suggests that it is expressed in most of the axolotl tissues except liver; the expression level appears to be highest in adult brain. We have also determined the temporal and spatial pattern of its expression at various stages of development. RT-PCR and in situ hybridization analyses indicate that expression of the AxRBP gene starts at stage 10–12 (gastrula), reaches a maxima around stage 15–20 (early tailbud), and then gradually declines through stage 40 (hatching). In situ hybridization suggests that the expression is at a maximum in neural plate and neural fold at stage 15 (neurula) of embryonic development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051356
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  • 5
    Electronic Resource
    Electronic Resource
    Immunofluorescent studies on Z-line-associated protein in cultured cardiomyocytes from neonatal hamsters (1993)
    Springer
    Cell & tissue research 271 (1993), S. 59-67 
    Details
    ISSN: 1432-0878
    Keywords: Alpha-actinin ; Desmin ; Vinculin ; Protein redistribution ; Cardiomyocytes ; Tissue culture ; Syrian hamster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The organization of the cytoskeletal proteins, alpha-actinin, vinculin and desmin, was studied in new-born hamster cardiomyocytes in vitro by immunofluorescent microscopy. Since there have been indications that the in vitro organization of certain cytoskeletal elements of cardiomyocytes is not the same as in vivo, the studies were designed to examine the reorganization of these proteins in cultured cells. The observations concentrated on three proteins that are known to be associated in vivo with myofibrillar Z-lines. Beginning at 2 days in culture, and during subsequent days, the proteins examined underwent substantial redistributions before they reorganized back to their associations with the myofibrillar Z-lines. The pattern and time course for these redistributions were characteristic for each protein. Alpha-actinin was the first to return to its typical location at the level of the Z-lines during the second day in culture, followed by desmin at 4 days. Vinculin usually did not become associated with the Z-lines until 6 days in vitro. In the present study, analyses of the distributions and redistributions of particular proteins in the cultured cardiomyocytes have been useful for helping to identify changes in the myocyte as a result of isolation and culture conditions. In addition, a better understanding of the temporal and spatial relationships between cytoskeletal proteins assembling into the Z-line area has been gained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00297541
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  • 6
    Electronic Resource
    Electronic Resource
    Activin A and transforming growth factor-β stimulate heart formation in axolotls but do not rescue cardiac lethal mutants (1995)
    Springer
    Cell & tissue research 282 (1995), S. 227-236 
    Details
    ISSN: 1432-0878
    Keywords: Key words: Growth factors ; Cardiogenesis ; Cardiac mutant ; Myocardium ; Axolotl ; Ambystoma mexicanum (Urodela)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. In the Mexican axolotl (salamander), Ambystoma mexicanum, a recessive cardiac lethal mutation causes an incomplete differentiation of the myocardium. Mutant hearts lack organized sarcomeric myofibrils and do not contract throughout their lengths. We have previously shown that RNA purified from normal anterior endoderm or from juvenile heart tissue is able to rescue mutant embryonic hearts in an in vitro organ culture system. Under these conditions as many as 55% of formerly quiescent mutant hearts initiate regular contractions within 48 hours. After earlier reports that transforming growth factor-β1 and, to a lesser extent, platelet-derived growth factor-BB could substitute for anterior endoderm as a promoter of cardiac mesodermal differentiation in normal axolotl embryos, we decided to examine the effect of growth factors in the cardiac mutant axolotl system. In one type of experiment, stage 35 mutant hearts were incubated in activin A, transforming growth factors-β1 or β2, platelet-derived growth factor, or epidermal growth factor, but no rescue of mutant hearts was achieved. Considering the possibility that growth factors would only be effective at earlier stages of development, we tested transforming growth factors-β1 and β5, and activin A on normal and mutant precardiac mesoderm explanted in the absence of endoderm at neurula stage 14. We found that, although these growth factors stimulated heart tube formation in both normal and mutant mesodermal explants, only normal explants contained contractile myocardial tissue. We hypothesize that transforming growth factor-β superfamily peptides initiate a cascade of responses in mesoderm that result in both changes in cell shape (the basis for heart morphogenesis) and terminal myocardial cytodifferentiation. The cardiac lethal mutation appears to be deficient only in the latter process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050475
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  • 7
    Electronic Resource
    Electronic Resource
    Activin A and transforming growth factor-β stimulate heart formation in axolotls but do not rescue cardiac lethal mutants (1995)
    Springer
    Cell & tissue research 282 (1995), S. 227-236 
    Details
    ISSN: 1432-0878
    Keywords: Growth factors ; Cardiogenesis ; Cardiac mutant ; Myocardium ; Axolotl, Ambystoma mexicanum (Urodela)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In the Mexican axolotl (salamander), Ambystoma mexicanum, a recessive cardiac lethal mutation causes an incomplete differentiation of the myocardium. Mutant hearts lack organized sarcomeric myofibrils and do not contract throughout their lengths. We have previously shown that RNA purified from normal anterior endoderm or from juvenile heart tissue is able to rescue mutant embryonic hearts in an in vitro organ culture system. Under these conditions as many as 55% of formerly quiescent mutant hearts initiate regular contractions within 48 hours. After earlier reports that transforming growth factor-β1 and, to a lesser extent, platelet-derived growth factor-BB could substitute for anterior endoderm as a promoter of cardiac mesodermal differentiation in normal axolotl embryos, we decided to examine the effect of growth factors in the cardiac mutant axolotl system. In one type of experiment, stage 35 mutant hearts were incubated in activin A, transforming growth factors-β1 or β2, platelet-derived growth factor, or epidermal growth factor, but no rescue of mutant hearts was achieved. Considering the possibility that growth factors would only be effective at earlier stages of development, we tested transforming growth factors-β1 and β5, and activin A on normal and mutant precardiac mesoderm explanted in the absence of endoderm at neurula stage 14. We found that, although these growth factors stimulated heart tube formation in both normal and mutant mesodermal explants, only normal explants contained contractile myocardial tissue. We hypothesize that transforming growth factor-β superfamily peptides initiate a cascade of responses in mesoderm that result in both changes in cell shape (the basis for heart morphogenesis) and terminal myocardial cytodifferentiation. The cardiac lethal mutation appears to be deficient only in the latter process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319114
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  • 8
    Electronic Resource
    Electronic Resource
    Immunohistochemical analysis of C-protein isoforms in cardiac and skeletal muscle of the axolotl, Ambystoma mexicanum (1995)
    Springer
    Cell & tissue research 282 (1995), S. 399-406 
    Details
    ISSN: 1432-0878
    Keywords: Key words: C-protein ; Isoforms ; Cardiac muscle ; Skeletal muscle ; Western blots ; Immunofluorescent microscopy ; Axolotl ; Ambystoma mexicanum (Urodela)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Of the several proteins located within sarco-meric A-bands, C-protein, a myosin binding protein (MyBP) is thought to regulate and stabilize thick filaments during assembly. This paper reports the characterization of C-protein isoforms in juvenile and adult axolotls, Ambystoma mexicanum, by means of immunofluorescent microscopy and Western blot analyses. C-protein and myosin are found specifically within the A-bands, whereas tropomyosin and α-actin are detected in the I-bands of axolotl myofibrils. The MF1 antibody prepared against the fast skeletal muscle isoform of chicken C-protein specifically recognizes a cardiac isoform (Axcard1) in juvenile and adult axolotls but does not label axolotl skeletal muscle. The ALD66 antibody, which reacts with the C-protein slow isoform in chicken, local- izes only in skeletal muscle of the axolotl. This slow axolotl isoform (Axslow) displays a heterogeneous distribution in fibers of dorsalis trunci skeletal muscle. The C315 antibody against the chicken C-protein cardiac isoform identifies a second axolotl cardiac isoform (Axcard2), which is present also in axolotl skeletal muscle. No C-protein was detected in smooth muscle of the juvenile and adult axolotl with these antibodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410050491
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  • 9
    Electronic Resource
    Electronic Resource
    Immunohistochemical analysis of C-protein isoforms in cardiac and skeletal muscle of the axolotl, Ambystoma mexicanum (1995)
    Springer
    Cell & tissue research 282 (1995), S. 399-406 
    Details
    ISSN: 1432-0878
    Keywords: C-protein ; Isoforms ; Cardiac muscle ; Skeletal muscle ; Western blots ; Immunofluorescent microscopy ; Axolotl, Ambystoma mexicanum (Urodela)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Of the several proteins located within sarcomeric A-bands, C-protein, a myosin binding protein (MyBP) is thought to regulate and stabilize thick filaments during assembly. This paper reports the characterization of C-protein isoforms in juvenile and adult axolotls, Ambystoma mexicanum, by means of immunofluorescent microscopy and Western blot analyses. C-protein and myosin are found specifically within the A-bands, whereas tropomyosin and α-actin are detected in the I-bands of axolotl myofibrils. The MF1 antibody prepared against the fast skeletal muscle isoform of chicken C-protein specifically recognizes a cardiac isoform (Axcard1) in juvenile and adult axolotls but does not label axolotl skeletal muscle. The ALD66 antibody, which reacts with the C-protein slow isoform in chicken, localizes only in skeletal muscle of the axolotl. This slow axolotl isoform (Axslow) displays a heterogeneous distribution in fibers of dorsalis trunci skeletal muscle. The C315 antibody against the chicken C-protein cardiac isoform identifies a second axolotl cardiac isoform (Axcard2), which is present also in axolotl skeletal muscle. No C-protein was detected in smooth muscle of the juvenile and adult axolotl with these antibodies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00318872
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  • 10
    Electronic Resource
    Electronic Resource
    Quantification of tropomyosin by radioimmunoassay in developing hearts of cardiac mutant axolotls,Ambystoma mexicanum (1982)
    Springer
    Journal of muscle research and cell motility 3 (1982), S. 161-167 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Recessive mutant genec in axolotls results in a failure of embryonic heart function. Earlier morphological studies showed that the mutant myocardial cells lack organized sarcomeric myofibrils. Electrophoresis and immunofluorescent studies suggested that the mutant heart cells contain substantial amounts of actin, myosin and α-actinin; however, tropomyosin appeared deficient. In the present study, we employed a newly developed extremely sensitive solid-phase radioimmunoassay method to quantitate very accurately the tropomyosin levels in normal and mutant sibling hearts at early (stage 35), intermediate (stage 39) and late (stage 41) developmental stages. Our results demonstrate that cardiac mutant hearts contain significantly lower than normal quantities of antigenically detectable tropomyosin at all of the developmental stages examined. This insufficiency of tropomyosin in mutant hearts may be a primary cause at the cell level for their failure to form organized myofibrils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00711940
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