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  • 1
    Electronic Resource
    Electronic Resource
    ROLE OF CARDIAC NEURAL CREST CELLS IN CARDIOVASCULAR DEVELOPMENT (1998)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physiology 60 (1998), S. 267-286 
    Details
    ISSN: 0066-4278
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Medicine , Biology
    Notes: Abstract The discovery in the chick embryo that a specific region of the neural crest, termed the cardiac neural crest, is essential for septation of the cardiac outflow tract and for aortic arch artery development has led to the classification of a whole series of human cardiac defects as neural crest-associated. Recently, several mouse genetic models have been effectively employed to yield new insights into the relationship between cardiac neural crest and structural heart development. In all the animal models of neural crest-related heart defects, prenatal mortality is too high to be attributed to structural defects of the heart alone, and there are obvious signs of severe cardiac dysfunction. The evidence indicates that poor viability is from impaired cardiac excitation-contraction coupling and contractile function at the myocyte level. The continued study of experimental and genetically defined models with neural crest-associated heart defects will prove useful in identifying the common pathways by which the neural crest contributes to normal heart development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.physiol.60.1.267
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  • 2
    Electronic Resource
    Electronic Resource
    Drosophila oocyte localization is mediated by differential cadherin-based adhesion (1998)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 395 (1998), S. 387-391 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In a Drosophila follicle the oocyte always occupies a posterior position among a group of sixteen germline cells. Although the importance of this cell arrangement for the subsequent formation of the anterior–posterior axis of the embryo is well documented, the molecular mechanism ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/26493
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  • 3
    Electronic Resource
    Electronic Resource
    The effect of 2,3-butanedione 2-monoxime (BDM) on ventricular trabeculae from the avian heart (1995)
    Springer
    Journal of muscle research and cell motility 16 (1995), S. 1-10 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary 2,3-butanedione 2-monoxime (BDM, 3–30 mm) decreased twitch force of intact ventricular trabeculae isolated from 19-day embryonic chick hearts in a dose-dependent manner. The responses to BDM were rapid and reversible. In an attempt to determine the cellular basis for the inhibitory effect of BDM, experiments were carried out on skinned muscle fibres and isolated myocytes. In trabeculae skinned with Triton X-100, BDM depressed maximum calcium activated force (Fmax) with an IC50 of 14 mm. At 3 mm BDM, the proportional decrease in twitch force in intact tissue was similar to that of Fmax in skinned tissue. At higher BDM concentrations (10 and 30 mm), however, the proportional decrease in twitch force was greater than that of Fmax. BDM (up to 10 mm) had no effect on the normalized force-pCa relationship. In saponin-skinned preparations, BDM (3 and 30 mm) released calcium from the fully loaded sarcoplasmic reticulum to a slightly greater extent in the absence of calcium (pCa 8.5) than in the presence of a fixed level of free calcium (pCa 5.5). Whole cell patch clamping of freshly isolated chick myocytes demonstrated that BDM caused a dose-dependent decrease in the T-and L-type calcium current. Therefore, at low BDM concentrations (3 mm), the decrease in twitch force can be ascribed predominantly to depression of the contractile apparatus while, at higher concentrations of BDM, there is an additional inhibitory effect of BDM on excitation-contraction coupling.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00125305
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  • 4
    Electronic Resource
    Electronic Resource
    Parvalbumin concentration and diffusion coefficient in frog myoplasm (1999)
    Springer
    Journal of muscle research and cell motility 20 (1999), S. 199-209 
    Details
    ISSN: 1573-2657
    Keywords: concentration ; diffusion coefficient ; frog ; muscle ; parvalbumin ; water
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The concentrations and diffusivity of two isoforms of parvalbumin, IVa and IVb, were measured using quantitative SDS PAGE in single fibers from semitendinosus muscles of the frog Rana temporaria. The concentrations of IVa and IVb were 2.9 ± 0.3 (SEM) and 4.5 ± 0.5 gl−1 total fiber volume, respectively. The total concentration of parvalbumin (7.4 ± 0.8 gl−1 total fiber) corresponds to a cytosolic concentration of 0.9 ± 0.1 mmoll−1 myoplasmic water. Estimates for the transverse and longitudinal diffusion coefficients for parvalbumin at 4°C were obtained in two ways: (1) by diffusion of parvalbumin out of skinned fibers into droplets of relaxing solution, and (2) by diffusion of parvalbumin between two juxtaposed skinned fibers under oil. The transverse diffusion coefficient obtained using the droplet method was significantly lower than that obtained using juxtaposed fibers, but the longitudinal diffusion coefficients obtained from both methods were similar. The juxtaposed fiber method more accurately approximates parvalbumin diffusion in undisturbed myoplasm because no artificial solutions were used and, upon fiber-to-fiber contact, a potentially confounding oil barrier at the interface rapidly disperses. The juxtaposed fiber method yielded values for transverse (4.27 ± 0.87 × 10−7 cm2 s−1) and longitudinal (3.20 ± 0.74 × 10−7 cm2 s−1) diffusion coefficients that were not significantly different, suggesting that diffusion of parvalbumin in myoplasm is essentially isotropic. The average diffusion coefficient of frog parvalbumin in myoplasm (3.74 ± 0.81 × 10−7 cm2 s−1; 4°C) is approximately a third of that estimated for frog parvalbumin diffusing in bulk water into and out of 3% agarose cylinders (10.6 × 10−7 cm2 s−1; 4°C). The reduced translational mobility of parvalbumin in myoplasm reflects an elevated effective viscosity due to tortuosity and viscous drag imposed by the fixed proteins of the cytomatrix and the numerous diffusible particles of the cytosol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005477002220
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  • 5
    Electronic Resource
    Electronic Resource
    Genetic diversity and morphological differentiation in Liatris helleri (Asteraceae), a threatened plant species (1996)
    Springer
    Biodiversity and conservation 5 (1996), S. 461-471 
    Details
    ISSN: 1572-9710
    Keywords: Liatris helleri ; genetic diversity ; allozymes ; endangered
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Liatris helleri (Asteraceae) is an insect-pollinated herbaceous perennial endemic to several high-elevation sites in the Blue Ridge Mountains of North Carolina. Allozymes were used to describe the genetic diversity and population structure in nine populations of this rare, federally listed species. Differences in leaf morphology were also examined for greenhouse-grown plants representing several populations. The proportion of the total genetic diversity found among populations, as indicated by the allozyme data, was 16%. Higher levels of population differentiation were found for differences in leaf shape; population of origin accounted for 37% of the variation in maximum leaf width, while families within populations accounted for 7%. In contrast to many endemic species, L. helleri maintains fairly high levels of genetic diversity. For the species, the percent polymorphic loci was 87.5, the average number of alleles at variable loci was 3.00 and the gene diversity was 0.276. Mean population values were percent polymorphic loci =58.4, mean number of alleles per polymorphic locus =2.59 and gene diversity =0.219. The estimated gene flow was low (Nm=0.85–1.32) and a relatively high correlation (r=0.55; p〈0.005) was found between linear geographic and genetic distance. This suggests that the populations are partially isolated by distance, despite the limited range (〈60 km) of the species. We recommend that population distinetiveness be maintained in restoration efforts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00056391
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  • 6
    Electronic Resource
    Electronic Resource
    Low levels of allozyme differentiation betweenPyxidanthera (pyxie-moss) taxa (Diapensiaceae) (1995)
    Springer
    Plant systematics and evolution 195 (1995), S. 159-168 
    Details
    ISSN: 1615-6110
    Keywords: Diapensiaceae ; Pyxidanthera barbulata ; Pyxidanthera brevifolia ; pyxiemoss ; Allozymes ; conservation ; genetic diversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract TwoPyxidanthera morphs of questionable taxonomic rank are described in the eastern United States. We analyzed leaf samples from ninePyxidanthera populations (four of each morph and one with intermediate morphology) for 13 allozyme loci. Our results do not support differentiation of the two morphs at the species level. Mean genetic identity among populations was high (Ī = 0.97), and typical of that found for conspecific populations. The proportion of total genetic diversity found among populations was low (GST = 0.079). Several low frequency alleles were confined to each of the morphs, being found in some of the populations of each morph, but not all.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00989292
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis of Monodisperse Oligo(para-phenyleneethynylene)s Using Orthogonal Protecting Groups with Different Polarity for Terminal Acetylene Units (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 277-286 
    Details
    ISSN: 1434-193X
    Keywords: Phenyleneethynylene ; Oligomers ; Alkynes ; Protective groups ; Repetitive synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Monodisperse oligo(para-phenyleneethynylene)s (oligoPPEs) were synthesized by a divergent-convergent synthesis starting from 1,4-dihexyl-2-(3-hydroxyprop-1-ynyl)-5-[2-(triisopropylsilyl)ethynyl]benzene and using the Pd/Cu-catalyzed alkyne-aryl coupling. The groups hydroxymethyl (HOM) and triisopropylsilyl (TIPS) function as orthogonal protective groups for the acetylene moieties. The polar HOM group shows a strong impact on the chromatographic behaviour of the products and makes the isolation of pure compounds very easy. The synthesis was pursued up to the nonamer. The oligoPPEs were fully characterised, including absorption and emission spectral data.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Design, characterization and processing of cellulose-S-acetyl: a precursor to an electroactive cellulose (1998)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 2777-2783 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The synthesis and characterization of Cell-SAc 3, a cellulose isopentyl (IP) ether with additional pendant S-acetyl (SAc) moieties (degree of substitution DSIP = 2.5, DSSAc = 0.4) are reported. Cell-SAc forms stable monolayers at the air-water interface once spread from dilute chloroform solution. The pressure-area isotherm of Cell-SAc is nearly identical to the parent Cell-IP 1, both exhibiting an expanded liquid phase at surface areas of 70 and 67 Å, respectively. The similarity of the two isotherms shows that the presence of the S-acetyl substituent does not result in an increase in the molecular area, at which the liquid-crystal analogous phase occurs. This observation suggests that the side-chains with the pendant S-acetyl group are oriented away from the water surface. Monolayers of Cell-SAc can be efficiently transferred onto silicon and hydrophobized glass or quartz substrates by a downstroke and upstroke technique. Resulting multilayers were characterized using X-ray reflection, FTIR, and UV-vis spectroscopy. The presence of S-acetyl moieties was found to increase the monolayer thickness relative to the parent Cell-IP. The cleavage of the S-acetyl group within the LB film is reported.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Photopolymers for non-linear optics: Design and synthesis of a polymer containing styrene-terminated tolane chromophores and its stabilization in an oriented configuration by photocrosslinking (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 196 (1995), S. 133-147 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new photocrosslinkable polymer designed for application in second harmonic generation has been prepared and tested for frequency doubling of IR lasers. The polymer is based on a colorless polyurethane with pendant tolane nonlinear optical chromophores that carry a polymerizable styrene moiety at their extremities. Photocrosslinking is achieved by irradiation of films containing a small amount of a bleachable radical photoinitiator. The effect of photoinduced radical crosslinking on the mobility of the chromophores has been studied by recording the intensity of the frequency doubled light, generated by a poled sample, with increasing temperature. As expected, photocrosslinking leads to NLO materials with highly stable chromophore orientation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1995.021960108
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  • 10
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    Rod−Coil and Coil−Rod−Coil Block Copolymers with Oligo(p-phenyleneethynylene) as the Rod Block (1998)
    American Chemical Society
    Details
    Publication Date: 1998-07-01
    Print ISSN: 0024-9297
    Electronic ISSN: 1520-5835
    Topics: Chemistry and Pharmacology , Physics
    Published by American Chemical Society
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