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  • Life and Medical Sciences  (107)
  • General Chemistry  (42)
  • Physics  (21)
  • 1
    Digitale Medien
    Digitale Medien
    Reorganization of cytoskeletal and junctional proteins during cochlear hair cell degeneration (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 215-227 
    Details
    ISSN: 0886-1544
    Schlagwort(e): guinea pig ; organ of Corti ; cytokeratins ; actin ; cingulin ; phalangeal scar ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: Experiments were carried out to elucidate changes in cytoskeletal elements and intercellular junctions in the organ of Corti, when hair cells degenerate and phalangeal scars form. Hair cell damage was induced by exposing guinea pigs to high intensity noise. The spatial and temporal changes in the organization of micro-filaments, intermediate filaments, and tight junction-specific proteins were investigated using scanning and transmission electron microscopy and histochemistry. The results show that microfilaments, cytokeratins, adherens junctions, and tight junctions rearrange their distribution in damaged areas. From the temporal sequence of these changes it appears that phalangeal scars develop simultaneous with hair cell degeneration, and that the integrity of the luminal membranes in the organ of Corti is not interrupted. Each scar is formed by two supporting cells which expand and invade the sub-apical region of the dying hair cell. This region becomes cytokeratin-positive. The two supporting cells meet at the mid-line of the scar, where a new junctional complex is formed. The junctional complex consists of tight junction and adherens-type junction, but desmosomes are absent.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cm.970180307
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  • 2
    Digitale Medien
    Digitale Medien
    Metabolic regulation in mammalian sperm: Mitochondrial volume determines sperm length and flagellar beat frequency (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 19 (1991), S. 180-188 
    Details
    ISSN: 0886-1544
    Schlagwort(e): spermatozoa ; cilia and flagella ; mechanochemical transduction ; dynein ; cell motility ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Medizin
    Notizen: In the absence of glycolytic support, mammalian sperm derive their energy for motility from a densely packed array of mitochondria at the base of the flagellum known as the midpiece. Using data on the morphometric dimensions of over 200 mammalian species, we found that an allometric relationship exists between midpiece length (Lm) and flagellum length (Lf). Specifically, the length of the midpiece varies approximately as the 3/2 power of the flagellar length although the proportionality constant is different for eutherian and marsupial sperm. In contrast, when we corrected for the fraction of the midpiece that was taken up by mitochondria, a single linear correlation between mitochondrial volume and flagellar length for all mammals was found. These allometric relationships were used along with basic flagellar hydrodynamic theories to establish a unifying equation that predicted flagellar frequencies for any mammalian sperm between 40 μm and 200 μm in length. These findings imply that, at least in mammals, the mechanisms for energy production and dissipation in sperm flagella are highly conserved.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cm.970190306
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  • 3
    Digitale Medien
    Digitale Medien
    A multiplanar anatomic study of the cervical proximal nerve roots and spinal nerves (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Clinical Anatomy 5 (1992), S. 433-440 
    Details
    ISSN: 0897-3806
    Schlagwort(e): anatomy ; spine ; sheath ; Life and Medical Sciences ; Miscellaneous Medical
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: An anatomic study focused on the proximal cervical spinal nerves has not been reported. Therefore, we dissected the cervical spinal nerves of three cadavers and examined stained sections in parasagittal and axial planes through the proximal cervical spinal nerves and root sheaths. These studies documented distinct segments of the spinal nerve which had not been completely described in the previous anatomic studies. The sheath originates from the dural sac as a common sleeve, divides into two sleeves, one containing the ventral root and one the dorsal root, and then distal to the dorsal root ganglion fuses again into one sleeve. A space, the interradicular cleft, separates the dorsal and ventral portions of the sleeve. The proximal segment of the spinal nerve proper distal to the dorsal root ganglion is composed of multiple small fascicles surrounded by a dense epineurium. The presence of an interradicular cleft in the cervical nerve root sheath and of fascicles in the cervical spinal nerve has significance for imaging of the cervical spinal nerves and for the pathogenesis of symptoms in cases of partial compression. © 1992 Wiley-Liss, Inc.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/ca.980050603
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  • 4
    Digitale Medien
    Digitale Medien
    Evidence for the presence of an integrin cell adhesion receptor on the oolemma of unfertilized human oocytes (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 31 (1992), S. 215-222 
    Details
    ISSN: 1040-452X
    Schlagwort(e): RGD ; α5 ; Immunobeads ; Integrins ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: The Arg-Gly-Asp peptide (RGD), contained in several extracellular matrix proteins such as fibronectin, laminin, vitronectin, and collagen, is a tripeptide that plays a role as a recognition sequence in many cell-to-cell and cell-to-matrix adhesion mechanisms, through its interaction with several receptors of the integrin family. We previously described the ability of the oolemma of hamster oocytes to bind GRGDTP coupled to the surface of activated immunobeads and demonstrated that RGD-containing oligopeptides inhibit the adhesion of human and hamster spermatozoa to zona-free hamster oocytes and their subsequent penetration. In the present experiments, we show, utilizing immunobeads coated with an RGD-containing peptide (PepTiteTM 2000), that the oolemma of unfertilized human eggs is also able to recognize this adhesion sequence. The binding of PepTiteTM 2000-coated immunobeads to the oolemma was inhibited by the oligopeptide GRGDTP as well as by fibronectin and laminin. When immunobeads were prepared with a PepTiteTM concentration of 10 μg/ml, GRGDTP 150 μg/ml, laminin 80 μg/ml, and fibronectin 60 μg/ml inhibited bead rosetting on the egg surface. These data suggest that a specific binding moiety for RGD is present on the human egg surface. The binding of fibronectin to the oolemma was also demonstrated by the rosetting of immunobeads coupled with antifibronectin antibody to human oocytes after their exposure to 1 mg/ml free fibronectin. Such binding of fibronectin to the oolemma could be inhibited by coincubation with a monoclonal antibody directed against the cell adhesion fragment of fibronectin. In addition, oolemmal rosetting of immunobeads coupled with a monoclonal antibody directed against the α5 subunit, usually part of the fibronectin receptor VLA 5 (α5β1), provided additional evidence that a putative fibronectin receptor is present on the oolemma of human eggs.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrd.1080310309
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  • 5
    Digitale Medien
    Digitale Medien
    Estimates of mRNA abundance in the mouse blastocyst based on cDNA library analysis (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 1 (1989), S. 233-241 
    Details
    ISSN: 1040-452X
    Schlagwort(e): Preimplantation ; Gene expression ; RNA quantity ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: Studies of gene expression during blastocyst formation in mouse preimplantation development have been limited by the amount of RNA available per embryo. Our present approach to this problem has been to construct a large, representative, blastocyst cDNA library in λgtll. Random hexadeoxynucleotides were used as primers with total blastocyst RNA serving as template. RNA collected from 4,100 32-64 cell embryos was used to generate a library with an initial size of 30 × 106 recombinants. By using clone frequency as a measure of relative mRNA abundance, our data support previous work on the relative and absolute amounts of actin, histone H2a, and intracisternal A particle. Furthermore, we provide estimates for the abundance of cytokeratin endo A, cytokeratin endo B, and β-tubulin from clone frequency data. Insert sizes for isolated clones range from 200 bp to 3.6 kb with full-length or near-full-length insert sizes for selected clones, indicating that random primer methods generate cDNAs which can represent a significant portion of the mRNA. We have so far characterized products whose abundance is equal to or greater than 0.002% of total RNA. This library offers the potential for the analyses of presumptive regulatory gene products in the mouse preimplantation embryo which are represented as low abundance (〈1% of mRNA) RNAs.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrd.1080010403
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  • 6
    Digitale Medien
    Digitale Medien
    Rat RIβ isoform of type I regulatory subunit of cyclic adenosine monophosphate-dependent protein kinase: cDNA sequence analysis, mRNA tissue specificity, and rat/mouse difference in expression in testis (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 26 (1990), S. 129-133 
    Details
    ISSN: 1040-452X
    Schlagwort(e): Kinase isoforms ; Protein kinase A ; cAMP ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: A rat complementary DNA (cDNA) for the RIβ isoform of type I cyclic adenosine monophosphate (cAMP)-dependent protein kinase regulatory subunit was cloned and sequenced and was found to contain the entire protein coding and 3′-untranslated regions, with a single (ATTAAA) poly-adenylation site. The largest open reading frame was preceded by a short outof-phase open reading frame, which is not seen in the corresponding mouse RIβ cDNA due to a single base substitution. The rat RIβ cDNA clone was 2,374 bases long and detected a rat mRNA of approximately 2.8 kilobases. Rat RIβ mRNA was abundant in adult rat brain and testis but was undetectable in other rat tissues. The rat RIβ cDNA also detected RIβ mRNA in mouse brain, but not mouse testis, from 10-week-old BALB/c or 10- and 6-week-old Swiss Webster mice. Thus, despite a 96% nucleotide identity in the coding region of RIβ in rat vs. mouse, there are at least two differences in these closely related species. First, there is a short open reading frame, which precedes the coding region in the rat but not the mouse. Second, unlike the mouse testis, the rat testis contains abundant levels of RIβ mRNA.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrd.1080260206
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  • 7
    Digitale Medien
    Digitale Medien
    Induction of neuronal differentiation by planar signals in Xenopus embryos (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Developmental Dynamics 197 (1993), S. 268-280 
    Details
    ISSN: 1058-8388
    Schlagwort(e): Planar signals ; Neural induction ; Xenopus ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The induction of the central nervous system in amphibian embryos is mediated both by early planar signals produced by mesoderm at the dorsal lip and later vertical signals emanating from the dorsal mesoderm after involution. We have examined the role and spatial extent of planar signals in the induction of neuronal differentiation. Planar explants that included only the deep layer of the dorsal marginal zone, comprising both the dorsal mesoderm and the contiguous dorsal ectoderm, were isolated at the beginning of gastrulation. After removal of the epithelial layer, explants were maintained in modified Danilchik's medium until mid-neurula stages, when they were transferred to modified Danilchik's medium + 0.1% bovine serum albumin and cultured on laminin. Neurite outgrowth occurred in 90% of these planar explants. In contrast, little or no neuronal differentiation occurred in either ventral planar explants or explants of ectoderm alone. Video analysis of cell movements shows that large-scale cell mixing does not occur between mesoderm cells and ectoderm cells in planar explants. Retrograde labelling of neuronal cell bodies indicates that cells throughout the ectoderm undergo neuronal differentiation; neurons also differentiate in cultures of distal ectoderm isolated at early neurula stages from planar explants prepared at the beginning of gastrulation. These observations indicate that planar signals act over an extended range to induce neuronal differentiation. The inductive capacity of vertical signals was examined by recombining animal caps from ultra-violet (UV) irradiated embryos with involuted mesoderm from normal midgastrula embryos. Differentiation of either neurons or anterior neural structures occurred in 73% of vertical recombinates. Our results demonstrate that planar signals from the dorsal lip of the blastopore are capable of inducing neuronal differentiation over a considerable distance in the absence of epithelial confinement, convergence and extension, and mixing between the mesoderm and ectoderm. © 1993 Wiley-Liss, Inc.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aja.1001970405
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  • 8
    Digitale Medien
    Digitale Medien
    Increased mesenchymal cell density accompanies induction of tropoelastin expression in developing elastic tissue (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Developmental Dynamics 200 (1994), S. 53-67 
    Details
    ISSN: 1058-8388
    Schlagwort(e): Elastin ; Tropoelastin ; Cartilage ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: We studied the differentiation of elastin-producing fetal bovine chondrocytes to understand the regulatory processes associated with induction of elastin expression. Analysis of auricular elastic cartilage development in vivo indicated that differentiation of the prechondrogenic blastema to an elastogenic phenotype was preceded and accompanied by condensation of the mesenchymal cells. In addition, induction of elastin production was temporally and spatially linked to expression of type II collagen and proteoglycans. We assessed the influence of cell density on the induction of tropoelastin expression in pre-elastogenic cells from developing ear buds. Tropoelastin expression was induced in prechondrogenic mesenchymal cells only if the cells were maintained at a high cellular density. In addition, high density culture upregulated tropoelastin expression in fully differentiated chondrocytes. Together these data suggest that high cell density facilitates cell:cell interactions that affect cell proliferation and influence tropoelastin expression. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 10 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/aja.1002000106
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  • 9
    Digitale Medien
    Digitale Medien
    Galactosyltransferase activity is restricted to the plasma membranes of equine and bovine sperm (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 28 (1991), S. 74-78 
    Details
    ISSN: 1040-452X
    Schlagwort(e): Galactosyltransferase ; Sperm-egg binding ; Fertilization ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie
    Notizen: β1, 4-Galactosyltransferase (GalTase) is localized to the plasma membrane of mouse sperm, in which it mediates the binding of sperm to glycoconjugate residues in the egg zona pellucida. In this study, the presence and subcellular distribution of sperm GalTase were determined in two other mammalian species that yield sufficient sperm for subecellular fractionation. Equine and bovine semen were collected, and the plasma membranes (PM), outer acrosomal membranes (OAM), and inner acrosomal membranes (IAM) were sequentially removed. The purities of the isolated membrane preparations were determined by transmission electron microscopy and found to be ≥90%, 96%, and 98% for equine PM, OAM, and IAM, respectively, and ≥80%, 94%, and 97% for bovine PM, OAM, and IAM, respectively. GalTase activity was assayed under optimal conditions in all membrane preparations and was preferentially localized to the isolated PM both in equine and in bovine spermatozoa. The selective localization of GalTase to the sperm PM in two other species suggest that it may serve as a generalized gamete receptor during initial sperm-egg binding in mammals.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mrd.1080280112
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  • 10
    Digitale Medien
    Digitale Medien
    Toward Controllable Molecular Shuttles“Molecular Meccano”, Part 10: For part 9 see P. R. Ashton, R. Ballardini, V. Balzani, M. Belohradsky, M. T. Gandolfi, D. Philp, L. Prodi, F. M. Raymo, M. V. Reddington, N. Spencer, J. F. Stoddart, M. Venturi, D. J. Williams, J. Am. Chem. Soc. 1996, 118, 4931-4951. (1997)
    Weinheim : Wiley-Blackwell
    Chemistry - A European Journal 3 (1997), S. 1113-1135 
    Details
    ISSN: 0947-6539
    Schlagwort(e): molecular devices ; nanostructures ; rotaxanes ; self-assembly ; translational isomerism ; Chemistry ; General Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A number of nanometer-scale molecular assemblies, based on rotaxane-type structures, have been synthesized by means of a template-directed strategy from simple building blocks that, on account of the molecular recognition arising from the noncovalent interactions between them, are able to self-assemble into potential molecular abacuses. In all the cases investigated, the π-electron-deficient tetracationic cyclophane cyclobis(paraquat-p-phenylene) is constrained mechanically around a dumbbell-shaped component consisting of a linear polyether chain intercepted by at least two, if not three, π-electron-rich units and terminated at each end by blocking groups or stoppers. The development of an approach toward constructing these molecular abacuses, in which the tetracationic cyclophane is able to shuttle back and forth with respect to the dumbbell-shaped component, begins with the self-assembly of a [2]rotaxane consisting of two hydroquinone rings symmetrically positioned within a polyether chain terminated by triisopropylsilyl ether blocking groups. In this first so-called molecular shuttle, the tetracationic cyclophane oscillates in a degenerate fashion between the two π-electron-rich hydroquinone rings. Replacement of one of the hydroquinone rings - or the insertion of another π-electron-rich ring system between the two hydroquinine rings - introduces the possibility of translational isomerism, a phenomenon that arises because of the different relative positions and populations of the tetracationic cyclophane with respect to the π-donor sites on the dumbbell-shaped component. In two subsequent [2]rotaxanes, one of the hydroquinone rings in the dumbbell-shaped component is replaced, first by a p-xylyl and then by an indole unit. Finally, a tetrathiafulvalene (TTF) unit is positioned between two hydroquinone rings in the dumbbell-shaped component. Spectroscopic and electrochemical investigations carried out on these first-generation molecular shuttles show that they could be developed as molecular switches.
    Zusätzliches Material: 19 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/chem.19970030719
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