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  • Articles  (60)
  • Elsevier  (40)
  • Springer  (20)
  • American Geophysical Union (AGU)
  • 2000-2004  (39)
  • 1975-1979  (21)
  • 1905-1909
  • Biology  (60)
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  • Articles  (60)
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  • 1
    ISSN: 1432-1939
    Keywords: Seed dispersal Seed shadow Hornbills Telemetry Tropical frugivory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. We studied two species of Ceratogymna hornbills, the black-casqued hornbill, C. atrata, and the white-thighed hornbill, C. cylindricus, in the tropical forests of Cameroon, to understand their movement patterns and evaluate their effectiveness as seed dispersers. To estimate hornbill contribution to a particular tree species' seed shadow we combined data from movements, determined by radio-tracking, with data from seed passage trials. For 13 individuals tracked over 12 months, home range varied between 925 and 4,472 ha, a much larger area than reported for other African avian frugivores. Seed passage times ranged from 51 to 765 min, with C. atrata showing longer passage times than C. cylindricus, and larger seeds having longer gut retention times than smaller seeds. Combining these data, we estimated that seed shadows were extensive for the eight tree species examined, with approximately 80% of seeds moved more than 500 m from the parent plant. Maximum estimated dispersal distances for larger seeds were 6,919 and 3,558 m for C. atrata and C. cylindricus, respectively. The extent of hornbill seed shadows suggests that their influence in determining forest structure will likely increase as other larger mammalian dispersers are exterminated.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied microbiology and biotechnology 54 (2000), S. 681-685 
    ISSN: 1432-0614
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract New methods of determining the structural groups —COOH and —CH2— have been developed. The investigation of carboxyl groups is possible both after derivatization with p-fluorophenacylbromide and by quantitative interpretation of the Fourier transform infrared (FT IR) spectra. There exists a linear relationship between the results of these two methods that is generally valid for the analysis of all brown coal components. The maximum extinction coefficient of the symmetric stretching vibration band of the CH2 groups has been determined using model substances. This allows quantification of this structural group directly from the FT IR spectrum. The results agree with the contents of methylene groups as determined by 13C-cross polarization–magic angle spinning–nuclear magnetic resonance (13C CPMAS NMR) spectroscopy. Using these methods, the COOH and CH2 groups contained in brown coals of the North Rhine region and in their bioconversion products have been quantified.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Cell & tissue research 156 (1975), S. 475-482 
    ISSN: 1432-0878
    Keywords: Annulate lamellae ; Spermatocytes ; Grasshoppers ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Intranuclear and cytoplasmic annulate lamellae were studied in grasshopper spermatocytes (Melanoplus) with the electron microscope. Although cytoplasmic annulate lamellae were observed in all three species examined, intranuclear annulate lamellae were found in only one species. The intranuclear annulate lamellae encompass certain nuclear material adjacent to the nuclear envelope forming a vesicle that is extruded into the spermatocyte cytoplasm. In this same species, cytoplasmic annulate lamellae are seen contiguous with granular masses of varying size. These structures were noted as being morphologically indistinguishable from the “yolk nuclei” of dragonfly oocytes (Kessel and Beams, 1969; Kessel, 1973).
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Somatic cell and molecular genetics 5 (1979), S. 281-301 
    ISSN: 1572-9931
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Using somatic cell hybridization gene mapping methodology, genes coding for human cell-surface proteins have been assigned to specific chromosomes. Lactoperoxidase-catalyzed iodination was employed to label external membrane proteins in cell hybrids between mouse and human cultured cells. Mouse and human external membrane proteins were separated by sodium dodecylsulfate-polyacrylamide gel electrophoresis. After electrophoresis, external membrane proteins were identified by autoradiography. An external membrane protein of 130,000 molecular weight (EMP-130) segregated concordantly with glutamic oxaloacetic transaminases (GOTs, EC 2.6.1.1), an enzyme marker encoded on chromosome 10. External membrane proteins of 195,000 and 175,000 molecular weight (EMP-195 and EMP-175) segregated concordantly with nucleoside phosphorylase (NP, EC 2.4.2.1), an enzyme marker encoded on chromosome 14. Limited proteolysis of the 195,000 and 175,000 molecular weight proteins suggests that these two proteins are modified forms of each other and are encoded by the same locus. These findings demonstrate the mapping of human genes coding for external proteins EMP-130 and EMP-195 to chromosomes 10 and 14, respectively. Chromosome analyses of cell hybrids supported these assignments.
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  • 5
    ISSN: 1572-9931
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The effects of polyethylene glycol (PEG) molecular weight and concentration on mammalian cell hybridization were studied. The peak hybridization-inducing activity with all grades of PEG from 400–6000 was found to occur in the concentration range of 50–55%. However, changes in concentration were seen to have different quantitative effects with different grades of PEG. For monolayer fusions, PEG 1000 at 50% seems to be the optimal combination of PEG molecular weight and concentration, in terms of both efficiency of hybridization and relative insensitivity to dilution effects.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Somatic cell and molecular genetics 5 (1979), S. 11-21 
    ISSN: 1572-9931
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A bioautographic assay was developed for the visualization of aminoacylase-1 (N -acylamino acid aminohydrolase, ACY-1; EC 3.5.1.14) after zone electrophoresis. Bioautography and species differences in electrophoretic mobility of ACY-1 made it possible to investigate the chromosome assignment of the gene for human ACY-1 using human—mouse somatic cell hybrids. Human ACY-1 segregated concordantly with β-galactosidase-A (βGAL A;EC 3.2.1.23) but showed discordant segregation with 32 other markers representing 23 linkage groups. The β GALA gene has been previously assigned to chromosome 3. From this evidence and confirming chromosome analyses, ACY-1has been assigned to chromosome 3. A genetic polymorphism in the electrophoretic mobility of ACY was observed in mouse strains, demonstrating that this enzyme can be mapped in genetic crosses of Mus musculus.
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  • 7
    ISSN: 1572-9931
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The structural gene (βGALA) coding for lysosomal β-galactosidase- A (EC 3.2.1.23) has been assigned to human chromosome 3 using man-mouse somatic cell hybrids. Human β-galactosidase-A was identified in cell hybrids with a species-specific antiserum to human liver β-galactosidase-A. The antiserum precipitates β-galactosidase-A from human tissues, cultured cells, and cell hybrids, and recognizes cross-reacting material from a patient with GM1 gangliosidosis. We have analyzed 90 primary man-mouse hybrids derived from 12 separate fusion experiments utilizing cells from 9 individuals. Enzyme segregation analysis excluded all chromosomes for βGALA assignment except chromosome 3. Concordant segregation of chromosomes and enzymes in 16 cell hybrids demonstrated assignment of βGALA to chromosome 3; all other chromosomes were excluded. The evidence suggests that GM1 gangliosidosis is a consequence of mutation at this βGALA locus on chromosome 3.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Somatic cell and molecular genetics 5 (1979), S. 1013-1029 
    ISSN: 1572-9931
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Methodology is described to enrich for heterokaryons after mammalian cell fusion. A heterogeneous cell mixture can be separated on a Sta-Put apparatus into fractions of uniform size cells by sedimentation through a 1% bovine serum albumin-5% Ficoll gradient. Unfused RAG and LM/TK− cells, differing by 10% in diameter, have been sorted by size; following fusion, larger and faster sedimenting cells were shown to be hybrids. This methodology can be utilized in genetic complementation studies of human genetic diseases where selection procedures for proliferating hybrids do not exist. When fibroblasts from individuals with Tay-Sachs disease [deficient in hexosaminidase A (HEX A−)] and Sandhoff-Jatzkewitz disease (HEX A− and HEX B−) are fused, HEX A is generated, demonstrating complementation of two different mutations. After Sta-Put fractionation, the HEX A complementation product was associated with the faster sedimenting multinuclear cells and not with the mononuclear parental cells. This methodology will facilitate detection of genetic differences in fibroblasts from related inherited disorders.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular neurobiology 20 (2000), S. 497-508 
    ISSN: 1573-6830
    Keywords: tau ; phosphorylation ; signal transduction ; protein kinase C ; Alzheimer's disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract 1. The potential functions of the microtubule-associated protein tau have been expanded by the recent demonstration of its interaction with the plasma membrane. Since the association of tau with microtubules is regulated by phosphorylation, herein we examine whether or not the association of tau with the plasma membrane is also regulated by phosphorylation. 2. A range of tau isoforms migrating from 46 to 64 kDa was associated with crude particulate fractions derived from SH-SY-5Y human neuroblastoma cells, and were retained during the initial stages of plasma membrane purification. During the extensive washing utilized in purification of the plasma membrane, portions of each of these isoforms were depleted from the resultant purified membrane. Immunoblot analysis with phospho-dependent and -independent antibodies revealed selective depletion of phospho isoforms during membrane washing. This effect was more pronounced for the slowest-migrating (64-kDa) tau isoform. 3. This putative influence of phosphorylation on the association of tau with the plasma membrane was further probed by transfection of SH-SY-5Y human neuroblastoma cells with a tau construct that could associate with the plasma membrane but not with microtubules. Treatment with phorbol ester or calcium ionophore, both of which increased phospho-tau levels within the cytosol and plasma membrane, was accompanied by the dissociation of this tau construct from the membrane. 4. These data indicate that phosphorylation regulates the association with the plasma membrane. Dissociation from the membrane by phosphorylation may place tau at risk for hyperphosphorylation and ultimate PHF formation in a manner previously considered for tau dissociated from microtubules.
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  • 10
    ISSN: 1432-1777
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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