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  • Artikel: DFG Deutsche Nationallizenzen  (89)
  • General Chemistry  (51)
  • Cell & Developmental Biology  (38)
  • 1
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 25 (1993), S. 87-104 
    ISSN: 0886-1544
    Schlagwort(e): polymerization ; solation ; gelation ; α-actinin ; gelsolin ; calcium ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: We describe a cellular automaton model of the actin cytoskeleton. The model incorporates spatial and temporal behavior at the macomolecular level and is relevant to the viscous nonequilibrium conditions suspected to occur in vivo. The model include cation and nucleotide binding to actin monomers, actin nucleation and polymerization into filaments, coss-linking with α-actinin, monomer sequestration with pfilin, filament severing, capping and nucleation with gelsolin, binding of profilin and gelsolin to membrane-bound phosphatidylinositide biphosphate (PIP2), and regulation of coss-linking and severing by changing calcium levels. We derive (1) equations for the molecular trnslation and rotation probabilities required for the cellular automaton simulation in terms of molecular size, shape, cytoplasmic viscosity, and temperature; and (2) equations for the binding probabilities of adjacent molecules in terms of experimentally determined reaction rate constants. The model accurately captures the known characteristics of actin polymerization and subsequent ATP hydrolysis under different cation and nucleotide conditions. An examination of gelation and sol-gel transitions resulting from calcium regulation of α-actinin and gelsolin predicts an inhomogeneous distribution of bound α-actinin and F-actin. The double-bound α-actinin (both ends bound to F-actin) is tightly bunched, while single-bound α-actinin is moderately bunched and unbound α-actinin is homogeneously distributed. The spatial organization of the α-actinin is quantified using estimates of fractal dimension. The simulation results also suggest that actin/α-actinin gels may shift from an isotropic to an amorphous phase after shortening of filaments. The gel-sol transition of the model shows excellent agreement with the present theory of polymer gels. The close correspondence of the model's predictions with previous experimental and theoretical results suggests that the model may be pertinent to better understanding the spatial and temporal properties of complex cytoskeletal processes. © 1993 Wiley-Liss, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 26 (1990), S. 248-252 
    ISSN: 1040-452X
    Schlagwort(e): Microfilaments ; Pinocytosis ; Amino acids ; Defolliculation ; Pigment ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Defolliculated fully grown oocytes of Xenopus laevis were treated with cytochalasin D (10 μg/ml) and their protein synthesis was studied by labelling with S-35 methionine. This treatment brought about an alteration in pigment pattern as well as a reduction in amino acid uptake by the oocytes. However, the radioactive amino acid taken by cytochalasin-treated oocytes was incorporated into protein in the same proportion as in untreated oocytes. These results suggested that subcortical pigment distribution and amino acid uptake in fully grown oocytes were microfilament-dependent processes, whereas protein synthesis in the oocyte was not.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 36 (1993), S. 7-15 
    ISSN: 1040-452X
    Schlagwort(e): Intercellular coupling ; Connexin32 ; Connexin43 ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: The connexins constitute a family of proteins that make up the intercellular membrane channels of gap junctions. We had previously reported the presence of two members of this protein family, connexins 32 and 43, in mouse one-cell zygotes (Barron et al., Dev Genet 10:318-323, 1989; Valdimarsson et al., Mol Reprod Dev 30:18-26, 1991), implying that both must be present in the mature oocyte and could be involved in mediating the intercellular coupling that occurs between the oocyte and cumulus granulosa during oogenesis. In the present report we provide evidence for this, based on an analysis of the cumulus-oocyte complex (COC) using reverse transcription-polymerase chain reaction (RT-PCR) and immunocytochemistry with a confocal microscope. Transcripts of both connexin32 (Cx32) and connexin43 (Cx43) were detected by RT-PCR in both components of the COC. Cx32 mRNA in the oocyte declined precipitously following human chorionic gonadotropin (hCG) stimulation of pregnant mare serum gonadotropin (PMSG)-primed ovaries, whereas there was no obvious change in Cx43 mRNA. Peptide-specific antibodies against both connexins provided diffuse cytoplasmic staining of oocytes as well as some punctate staining near the oocyte surface, which could not be unequivocally resolved as cumulus-oocyte gap junctions. However, the two antibodies did provide clear evidence of Cx32 and Cx43 in gap junction-like structures between cumulus cells. We could find no evidence of the incorporation of the oocyte's store of Cx32 into gap junctions during postfertilization development. These findings make it very likely that intercellular coupling within the COC involves at least three types of gap junction channels (32-32, 32-43, 43-43), only one of which (43-43) is retained by the preimplantation embryo. © 1993 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 30 (1991), S. 18-26 
    ISSN: 1040-452X
    Schlagwort(e): Gap junction protein ; Gene expression ; Compaction ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: De novo assembly of gap junctions begins during compaction in the eight-cell stage of mouse development, and intercellular coupling mediated by gap junctions appears to be required for maintenance of the compacted state. We have begun to explore the expression of the family of genes encoding the connexins, the proteins that form the gap junction channels. We recently reported that a protein with antigenic and size similarity with connexin32, the rat liver gap junction protein, is inherited as an oogenetic product by the mouse zygote, but its gene appears not to be transcribed prior to implantation (Barron et al., Dev Genet 10:318-323, 1989). Here we report that another member of this gene family, connexin43, is transcribed by the embryonic genome from shortly after the time of genomic activation. As revealed by Northern blotting, connexin43 mRNA is absent from ovulated oocytes, becomes detectable in the 4-cell stage, and accumulates steadily thereafter to reach a maximum in blastocysts. In contrast, no transcripts of connexin26 could be detected in any preimplantation stage. A protein with antigenic and size similarity with connexin43 from rat heart was found by Western blotting to accumulate from the four-cell stage onward. Immunofluorescence analysis with embryo whole mounts was used to demonstrate that this protein is incorporated into punctate interblastomeric foci during compaction, consistent with its assembly into gap junction plaques. We conclude that connexin43 is one member of the connexin gene family whose zygotic expression is critical for preimplantation morphogenesis.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Morphology 89 (1951), S. 135-149 
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Moccasin venom injected intradermally into mouse skin induces an almost immediate clasmatosis of mast cells, followed by dissolution or loss of staining reaction of the released granules, a condition from which there is no observable recovery for at least 25 days. The possible significance of this reaction is discussed.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Journal of Morphology 97 (1955), S. 55-75 
    ISSN: 0362-2525
    Schlagwort(e): Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Materialart: Digitale Medien
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  • 7
    ISSN: 1434-193X
    Schlagwort(e): Indiumallyl compounds ; Vinylcyclopropanes ; α,β-Unsaturated carbonyl compounds ; Diastereoselectivity ; Dibenzylideneacetone ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Allylindium reagents, prepared from excess allylic halide (Br or I) and indium metal, react with α,β-unsaturated ketones and aldehydes to give, after aerobic acidic workup, homoallyl-substituted vinylcyclopropanes. This process was explored and developed after a chance discovery arising from a side reaction in an attempted Pd-catalysed process. The structure of the cyclopropane arising from the reaction of bis(p-chlorobenzylidine)acetone was confirmed by X-ray crystallography. Whilst bis-α,β-unsaturated ketones give rise to a single homoallylcyclopropane species, α,β-unsaturated ketones and aldehydes give diastereomeric mixtures whose relative stereochemistry were assigned by NOE experiments. Crotylindium reagents react with good to perfect regioselectivity to afford tetrasubstituted cyclopropanes but prenylindium reagents fail to generate the analogous pentasubstituted rings.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1434-193X
    Schlagwort(e): Indium ; Vinylcyclopropanes ; Ring closing metathesis ; Norcarenes ; Kinetic diastereoselection ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Homoallyl-substituted vinyl cyclopropanes 1a-c, which are readily prepared by reaction of allylindium reagents with α,β-unsaturated ketones and aldehydes, undergo Ru-catalysed RCM reactions with Grubbs catalyst to give [4.1.0]bicyclooct-2-ene (norcarene) type bicyclic products. Noncyclisable ‘trans’ homoallyl-substituted vinyl cyclopropanes 1b and 1c are separated from their ‘cis’ diastereomers by RCM to 5b and 5c - but only with moderate efficiency due to a competing homo-cross metathesis (‘dimerisation’) to give 7b and 7c, respectively. However, the four diastereomers of the (homoallyl)distyrylcyclopropane 14a obtained from indium-mediated reaction of dibenzylideneacetone and crotyl bromide undergo remarkable kinetic diastereoselection in their RCM reactions to give a 4,7-dimethyl[4.1.0]bicyclohept-2-ene-type product 15a. This process allows recovery of a single diastereomer (〉 95%) of 14a without dimerisation being a significant side reaction. Furthermore, the RCM product 15a is obtained rich in one diastereomer (ca. 90%). The kinetic diastereoselection and lack of dimerisation can be rationalised by considering developing transannular interactions and a pseudo-A1,3 strain model.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1434-1948
    Schlagwort(e): Chirality ; Ruthenium ; Chiral resolution ; Nitrogen heterocycles ; Carbonyl complexes ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A range of chiral building blocks of the type Δ- or Λ-[Ru(pp)2(CO)2]2+ {pp = bidentate ligands bpy (2,2′-bipyridine), phen (1,10-phenanthroline) and Me2bpy (4,4′-dimethyl-2,2′-bipyridine)} have been synthesized, and their enantiomeric purity and absolute configurations determined by CD and NMR studies. Decarbonylation using trimethylamine oxide in the presence of the respective pp ligand at room temperature produced the corresponding tris(bidentate) species [Ru(pp)3]2+ with retention of configuration at the ruthenium(II) centre. A general chromatographic technique for resolution of tris-homoleptic complexes of the type [Ru(pp)3]2+ was investigated, with the absolute configurations of the resolved complexes confirmed by CD studies, and the X-ray structural analyses of Δ-(-)-[Ru(Me2bpy)3]{(-)-O,O′-dibenzoyl-L-tartrate} and Λ-(+)-[Ru(phen)3]{(+)-O,O′-di-4-toluoyl-D-tartrate}. Resolution is also reported for the analogous species containing three potential bridging ligands, [Ru(bpm)3]2+ and [Ru(HAT)3]2+ (bpm = 2,2′-bipyrimidine; HAT = 1,4,5,8,9,12-hexaazatriphenylene). The versatility of the chromatographic procedure was demonstrated by the resolution of a series of bis-heteroleptic complexes [Ru(pp)2(pp′)]2+ {pp′ = dpq (dipyrido[3,2-d:2,3′-f]quinoxaline), dpqc (dipyrido[3,2-a:2,3-d]-6,7,8,9-tetrahydrophenazine), and dppz {dipyrido[3,2-a:2,3′-d]phenazine)}.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 10
    ISSN: 1434-1948
    Schlagwort(e): Coordination modes ; Cyclophanes ; Macrocycles ; Sandwich complexes ; Solid-state structures ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A novel mode of containment for metal ions which participate in longer-range interactions with aryl rings (≥ 2.5 Å) is demonstrated in the preorganized cylindrical host 1. Three equatorial sulfur atoms in 1 hold metals in a trigonal planar ligand field between two apical benzene centroids at an M-Ar distance of about 3 Å. Evidence of an interaction between the π electrons and the metals is gained by 1H NMR spectroscopy of the complexes, and support for the general description of metal-arene contacts in the 2.5-3.5 Å range as ‘‘bonds’’ is derived from a statistical study of η6-coordination in the solid state. Crystal structures of [Ag(1)]BF4 and [Cu(1)]BF4 confirm the first examples of arene AgI and CuI sandwich complexation and indeed the only structurally characterized CuI-aryl centroid interaction. The two isomeric tris-sulfoxides derived from 1 show less tendency to interact with metals ions.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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