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  • Life and Medical Sciences  (3,916)
  • 1995-1999  (3,916)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 162 (1995), S. 36-43 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Insulin-like growth factor II (IGF II) regulated tissue-specific gene expression in hepatoma cell lines, but had no effect on expression of tissue-specific genes in primary cultures of E14 and newborn rat liver cells depleted of erythroid cells. No change was observed in these primary cultures with respect to α-fetoprotein (α-FP), albumin, cytokeratin 19 (CK 19), γ-glutamyltranspeptidase (GGT), and IGF II receptors. Two well-differentiated hepatomas, HepG2 and FTO-2B, and a poorly differentiated hepatoma, H4AzC2, did not show increased proliferation in the presence of IGF II, yet showed gene expression changes in response to IGF II. In HepG2 cells, IGF II increased albumin mRNA levels and resulted in a shift from clusters of cells positive to 100% of the cells expressing immunohistochemically detectable albumin. The transcription factor HNF-3β mRNA and protein levels of the bile duct markers, CK19 and GGT, were also increased in the presence of IGF II. Other genes tested were not affected, including α 1-antitrypsin, and two liver specific transcription factors, HNF-4 and HNF-3α. In FTO-2B cells, IGF II increased the expression of albumin, CK19, and GGT, without accompanying changes in albumin and GGT mRNAs. In H4AzC2 cells, IGF II reduced CK19 and OC.3 protein levels and GGT, transferrin, and HNF-3β mRNAs. The effects of IGF II on H4AzC2 cells were not blocked in the presence of an anti-rat IGF II receptor antibody. We conclude that IGF II affects tissue-specific gene expression of hepatomas and qualitative and quantitative aspects of its influence on the hepatomas is dependent on their degree of differentiation. © 1995 Wiley-Liss, Inc.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 25 (1995), S. 29-36 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Obwohl die Neurobiologie in den letzten Jahren einen enormen Aufschwung erfahren hat, ist noch immer sehr wenig über die zentralnervösen Grundlagen für die Steuerung von Verhaltensweisen bekannt. Voraussetzung für die Erforschung dieses Phänomens ist ein geeignetes Modellsystem: Das zu untersuchende Verhalten muß klar definiert und leicht zu messen sein; die wesentlichen Elemente des zentralnervösen Schaltkreises, der diese Verhaltensweise kontrolliert, sollten bekannt sein; und schließlich muß es möglich sein, die Häufigkeit, mit der diese Verhaltensweise auftritt, im Experiment zu verändern. Alle drei Forderungen sind in besonderer Weise bei schwachelektrischen Messerfischen erfüllt. Diese unscheinbaren Aquarienbewohner eröffnen damit die Möglichkeit, einen Einblick in die Komplexität der Steuerung von Verhalten durch das Gehirn zu erhalten.
    Additional Material: 11 Ill.
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  • 3
    ISSN: 0749-503X
    Keywords: Saccharomyces cerevisiae ; chromosome XV sequencing ; expressed sequence tags ; ADH1 ; COQ3 ; MSH2 and RCF4 ; transmembrane proteins ; organelle targeting ; ARS ; GCN4 ; Arabidopsis thaliana ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The nucleotide sequence of a 29·425 kb fragment localized on the left arm of chromosome XV from Saccharomyces cerevisiae has been determined. The sequence contains 13 open reading frames (ORFs) of which four encode the known genes ADH1, COQ3, MSH2 and RCF4. Predictions are made concerning the functions of the unknown ORFs. Some of the ORFs contain sequences similar to expressed sequences tags (EST) found in the database made available by TIGR. In particular, the highly expressed ADH1 gene is represented in this database by no less than 20 EST sequences. Two ARS sequences and a putative functional GCN4 motif have also been detected. One ORF (O0953) containing nine putative transmembrane segments is similar to a hypothetical membrane protein of Arabidopsis thaliana. Characteristic features of the other ORFs include ATP/GTP binding sites, a fungal Zn(2)-Cys(6) binuclear centre, an endoplasmic reticulum targeting sequence, a β-transducin repeat signature and in two instances, good similarity to the prokaryotic lipoprotein signal peptide motif. The sequence has been deposited in the EMBL data library under Accession Number X83121.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 28 (1998), S. 64-71 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Viele Erkenntnisse über das Geschehen in einer Zelle vermitteln uns das Bild eines Fließgleichgewichts, das es der Zelle erlaubt, sich flexibel auf änderungen der Umwelt einzustellen. Während dieses Prinzip für Stoffwechselprozesse schon lange akzeptiertes Lehrbuchwissen darstellt, haben Untersuchungen zum Proteinabbau dieses Dogma nun auch auf proteolytische Prozesse erweitert. Die meisten zelluläen Proteine werden ständig neu gebildet und ebenso auch wieder abgebaut. Hierbei können sich ihre individuellen Halbwertszeiten je nach Funktion der Proteine stark voneinander unterscheiden. So besitzen Enzyme, die wichtige metabolische Kontrollfunktionen in der Zelle ausüben, Halbwertszeiten im Bereich von Minuten, während andere Proteine über Monate stabil vorliegen können. Der gezielte Proteinabbau stellt für die Zelle ein wirkungsvolles Kontrollinstrument dar, um die Konzentrationen wichtiger regulatorischer Proteine schnell und irreversibel zu senken. Auf diese Weise kann sich die Zelle zudem von abnormalen, wie zum Beispiel falsch gefalteten oder mutierten, und damit funktionsunfähigen Proteinen befreien, deren Ansammlung sie auf längere Sicht hin schäadigen würde. überdies werden wertvolle Aminosäurebausteine im Sinne eines effektiven Recyclings wieder zur Synthese neuer Proteine eingesetzt. Da die Proteinbiosynthese ein energieaufwendiger Prozeß ist, muß der regulierend eingesetzte Proteinabbau einer strikten Kontrolle unterliegen. Wir beginnen gerade zu verstehen, wie die Zelle das Kunststück fertigbringt, aus der großen Vielzahl aller zelluläen Proteine mit hoher Präzision diejenigen auszuwählen, die zu einem bestimmten Zeitpunkt abgebaut werden sollen.
    Additional Material: 7 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 42 (1995), S. 200-209 
    ISSN: 1040-452X
    Keywords: Embryo ; Pronucleus ; Microtubules ; Chromosome analysis ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Peri-fertilization exposure to Carbendazim (MBC; a microtubule poison) induces infertility and early pregnancy loss in hamsters. Presently, both in vivo and in vitro techniques were employed to characterize the effects of MBC on cellular aspects of fertilization in hamsters. Exposure to MBC during either in vivo or in vitro fertilization (IVF) induced identical morphological abnormalities in the maternal chromatin of zygotes and embryos. These abnormalities included either multiple second polar bodies (PB2), and/or multiple small female pronuclei (PN), or meiotic arrest. Multiple PB2, multiple female PN, multiple PB2 with multiple female PN, or meiotic arrest were exhibited by approximately 31%, 15%, 12%, and 2% of the in vivo zygotes; and 3%, 16%, 36%, and 20% of IVF zygotes, respectively. The effects of MBC persisted to day 2 of pregnancy as indicated by decreased (P ≤ 0.05) embryo development to the two-cell stage and the presence of micronuclei in 6% of two-cell embryos from MBC-treated females. Immunofluorescence analysis of microtubules (MTs) confirmed that MBC disrupted spindle MTs during IVF. Numerical chromosome analysis revealed that a single dose of MBC administered during in vivo fertilization induced aneuploidy in the resulting pronuclear-stage zygotes. The present data point to two mechanisms by which peri-fertilization MBC exposure may induce early pregnancy loss: 1) arrested meiosis with no zygotic cleavage; or 2) induction of zygotic aneuploidy with subsequent developmental arrest. © 1995 wiley-Liss, Inc.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 41 (1995), S. 479-485 
    ISSN: 1040-452X
    Keywords: Oogenesis ; Folliculogenesis ; Meiosis ; Chromatin structure ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We investigated the changes in the organization of oocyte nuclear chromatin and nucleolar-associated chromatin throughout folliculogenesis. Zona-free oocytes were isolated from ovaries, grouped into seven classes according to size and chromatin organization, and analyzed after staining with Hoechst 33342. We show that oocyte differentiation from the dictyate stage to the conclusion of maturation is associated with either of two chromatin configurations. Initially, all oocytes are in the NSN configuration (nonsurrounded nucleolus oocytes; characterized by a Hoechst positive-chromatin pattern of small clumps forming a network on the nuclear surface, with a nucleolus nonsurrounded by chromatin). While growing, some of these NSN oocytes continue their development in the NSN configuration, whereas others shift (from class IV on) into the SN configuration (surrounded nucleolus oocytes; characterized by a threadlike chromatin organization that may partially surround the nucleolus or project towards the nuclear periphery). The percentage of SN oocytes increases both with increasing size of the oocyte (class I-III, 10-40 μm in diameter: 100% NSN vs. 0% SN; class VII 70-80 μm in diameter: 47.3% NSN vs. 52.3 SN, in 4-6-week-old females), and with aging (class VII: 94.1% NSN vs. 5.9% SN in 2-week-old females; 11.8% NSN vs. 8.2% SN in 56-week-old females). Further, we suggest as a working hypothesis that those oocytes that switch to the SN chromatin organization early in maturation may not be ovulated, even though this particular chromatin structure normally occurs just prior to ovulation. © 1995 Wiley-Liss, Inc.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 30 (1995), S. 26-37 
    ISSN: 0886-1544
    Keywords: myosin ; myosin-I ; unconventional myosin ; brush border ; epithelia ; membrane ; phospholipid ; fluorescence microscopy ; actin ; calmodulin ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Brush border myosin-I (BBMI) is associated with the membrane of intestinal epithelial cells where it probably plays a structural role. BBMI also has been identified on Golgi-derived vesicles in intestinal epithelial cells where it may translocate vesicles into the brush border. However, the mechanochemical activity of BBMI bound to a phospholipid membrane has not been described. This study reports that phospholipid membrane-associated BBMI displays ATPase activity when bound to phospholipids, but does not move actin filaments when associated with a phospholipid bilayer. BBMI does not bind significantly to brush border membrane lipids, which contain about 16% phosphatidylserine (PS), in either a pelleting or planar membrane assay. Similarly, planar membranes containing 20% PS do not bind a significant amount of BBMI. Increasing the concentration of PS to 40% does result in the binding of BBMI to both vesicles and planar membranes. This binding is enhanced with increased Ca2+ concentrations. BBMI retains its ATPase activity when bound to phospholipid vesicles containing 40% PS. However, BBMI attached to a phospholipid bilayer surface does not move actin filaments, even though the amount of BBMI bound to the lipid surface, as reflected by the number of actin filaments associated with bilayer-bound BBMI, is sufficient to observe motility in control experiments. When membrane fluidity is reduced by adding cholesterol to the membrane lipids containing 40% PS, BBMI still binds to the membrane, but again no actin filament motility is observed. The lack of binding by BBMI to brush border membrane lipids and the absence of membrane-associated BBMI mechanical activity suggest that factors in addition to membrane lipids are necessary for membrane-associated myosin-I motility. © 1995 Wiley-Liss, Inc.
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  • 8
    ISSN: 0749-503X
    Keywords: red ade mutations ; Kluyveromyces lactis ; ADE1 ; ADE2 ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Seventy-six red adenine mutants of Kluyveromyces lactis were isolated. By complementation they could be assigned to two groups with 31 and 45 mutants. Transformation of several strains from each group with plasmids containing the Saccharomyces cerevisiae ADE1 or ADE2 gene showed that the largest group was ade2 and the other group was ade1. Several previously isolated ‘ade1’ mutants were classified to either group and given new gene and allele numbers. ADE1 was localized at chromosome III, closely linked to the mating type gene, making it a convenient marker for mating type. ADE2 was localized at chromosome V.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 11 (1995), S. 493-536 
    ISSN: 0749-503X
    Keywords: Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Additional Material: 10 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Biologie in unserer Zeit 28 (1998), S. 294-303 
    ISSN: 0045-205X
    Keywords: Life and Medical Sciences
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Die Affen Madagaskars sind die Lemuren. Sie haben den Namen der römischen Totengeister von französischen Forschungsreisenden des 17. Jahrhunderts wohl deshalb erhalten, weil viele von ihnen im Dunkeln der Nacht durch die Wälder streifen und dabei oft laut und furchteinflößlig;end rufen, und weil ihre Augen beim Anleuchten wegen des rötlich reflektierenden Tapetum lucidum regelrecht aufgühen. Erst in den letzten Jahren gelang es, durch Langzeitprojekte auf Madagaskar und begleitende Untersuchungen bei der Haltung in menschlicher Obhut etwas Licht in die Artendiversität, Verbreitung und Lebensweise der noch wenig bekannten nachtaktiven Vertreter dieser einzigartigen, von der Ausrottung bedrohten Halbaffengruppe zu bringen.
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