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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 151 (1977), S. 213-237 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This ultrastructural study on the localization of Ca+2 in developing skeletal muscle indicates that the formation of calcium-accumulating components begins during embryonic development. Both oxalate and pyroantimonate techniques are used to localize Ca+2 in distinct cellular components of chick pectoral and sartorius muscles. Two major sites for Ca+2 accumulation are present in ultrathin sections of embryonic and post-embryonic muscles: the terminal cisternae of the sarcoplasmic reticulum and specific lines in the I-bands. Calcium oxalate-accumulating vesicles are present in the smallest recognizable myotubes at the twelfth day of incubation, but calcium-accumulating components are not seen at myofibrillar I-band sites until the fourteenth to seventeenth days of incubation. The fact that myofibrils first form and later in development accumulate a Ca+2-binding component suggests that this Ca+2-binding component is not necessary for the formation of myofibrils, but is added to myofibrils before hatching to serve a probable regulatory role in contraction.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 2 (1982), S. 47-71 
    ISSN: 0886-1544
    Keywords: microtubules ; transport ; secretion ; peritrich ciliate ; directional turnover ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The role of microtubules in secretory granule translocation was studied during stalk secretion in the peritrich ciliate, Zoothamnium arbuscula. In each cell, the release of stalk-forming secretory materials is restricted to a specialized region of the cytoplasm, the scopula. Many of the membrane-bound secretory granules that dominate the scopular cytoplasm appear to be aligned along cortical microtubules that converge on the scopular surface. This arrangement is consistent with the hypothesis that microtubules transport granules relative to the sites of exocytosis. To establish the role of microtubules in stalk secretion, telotrochs were exposed to agents with different disruptive effects on microtubule function. Exocytosis itself is not prevented by these drugs, and granules positioned for secretion prior to treatment are released. Maytansine and isopropyl-n-phenyl carbamate (IPC) completely inhibit stalk elongation. In maytansine-treated cells, microtubules are absent from the scopular cytoplasm, and granules are absent from the scopular surface. Microtubules are present in IPC-treated cells, but the granules are misdirected to the cytoplasm lateral to the scopula where no secretory sites exist. Even though the rate of stalk secretion is decreased by deuterium oxide (D2O), a control length stalk is eventually produced. In D2O-treated cells microtubules are present and in their normal orientation. The inhibition of secretion when microtubules are absent (maytansine) or misdirected (IPC) and the retardation of secretion when microtubule turnover is reduced (D2O) supports a mechanism of granule transport based on the directional turnover of microtubule subunits.
    Additional Material: 17 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 2 (1982), S. 83-89 
    ISSN: 0886-1544
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 6 (1986), S. 114-121 
    ISSN: 0886-1544
    Keywords: mitosis ; microtubules ; tubulin incorporation ; assembly polarity ; Chaetopterus ; HeLa cells ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The incorporation of tubulin into mitotic spindles in situ was studied by incubating permeabilized mitotic cells in solutions containing [3H]GTP-labeled or dichlorotriazinylamino fluorescein (DTAF)-labeled tubulin. Metaphase HeLa cells or spindle-containing “minicells” from Chaetopterus oocytes were lysed in a microtubule-assembly buffer plus 0.5% Nonidet P-40, 1 mg/ml 120,000g supernatant mammalian brain tubulin, and [3H]GTP. After different periods of incubation, mitotic spindles were isolated in 2 M-glycerol-containing assembly buffer and separated from unbound counts by centrifugation through a 4 M-glycerol cushion; 3H counts per mg protein increase linearly for 8-12 min and then reach a plateau or steady state in both Chaetopterus oocytes and HeLa cells. Addition of 4 mM CaCl2 blocks or reverses incorporation. Little or no [3H]GTP is incorporated if exogenous tubulin or lysed cells are omitted from the assembly mixture.To measure the loss rate of [3H]GTP-tubulin from mitotic spindles, cells were incubated in tubulin plus [3H]GTP for 30 min, and a 20-fold excess of cold GTP (2 mM) was added. Samples were removed after incubation for different periods, and spindles were isolated as described above and counted for 3H content. [3H]GTP is lost from spindles at a rate of about 16%/min until a new steady state is reached in about 8 min. These results are consistent with an incorporation and turnover of [3H]GTP-tubulin in spindle microtubules of these lysed-cell models.The location of this newly incorporated tubulin in the spindle was investigated by incorporating fluorescent DTAF-tubulin into mitotic spindles of these lysed cell types. A short pulse (2-5 min) appears to label microtubules (MTs) near metaphase chromosomes and longer exposures label the entire spindle.The rates of incorporation and turnover that we see by [3H]GTP and fluorescent tubulin incorporation in situ are faster than those observed with brain MTs at steady state in vitro but are in the range of the rates of spindle fiber formation in prophase, and spindle MT reassembly after cooling.
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  • 5
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 1124-1134 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Two-phase flow in porous media is described based on the extended form of Darcy's law, which ignores momentum transfer at fluid-fluid interfaces. Two forms of corrections to this simple description have been proposed in the literature: one on the relative permeability dependence on viscosity ratio; the other on the velocities assumed to be proportional to both phase pressure gradients and so introducing an additional saturation-dependent cross coefficient.In this article, to identify the correct form of transport equations, a simple cubic network model of 30 × 30 × 30 bonds is used. The cross section of the bonds is that of a four-cusp duct. The fluid interface in each duct is located by capillary equilibrium. The duct hydraulic conductances are then obtained as a function of viscosity ratio and phase volume fraction using a finite element calculation. These individual duct results are used in the network calculations for which a percolation algorithm is applied to simulate nonwetting phase displacing wetting phase, a process also known as initial drainage. Flow calculations show that both the nonwetting-phase relative permeability and the cross coefficient are strong functions of saturation and viscosity ratio. Also, the off-diagonal terms may contribute to a nonnegligible fraction of the flow. The proposed generalization of the Darcy equations is applicable to all problems involving multiphase flow in porous media. The current practices for relative permeability measurements and reservoir simulation may have to be reexamined in the context of the proposed transport equations.
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  • 6
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Methyl α-cyanoacrylate, when suitably inhibited by Lewis acids against anionic polymerization, can be polymerized readily with free-radical initiators to form hard, clear, high molecular weight polymers. The ratio of kp2/kt is approximately 0.021 at 60°C. if 100% efficiency of initiation by azobisisobutyronitrile is assumed. Acceleration occurs at very low conversion to polymer during bulk polymerizations. The homopolymer is thermally unstable at temperatures only slightly above the glass temperature (estimated to be 165-170°C.). Degradation of the polymer under gamma irradiation is pronounced, only 18 e.v. being required per main-chain scission.
    Additional Material: 3 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Bioluminescence and Chemiluminescence 10 (1995), S. 239-245 
    ISSN: 0884-3996
    Keywords: Electrochemiluminescence ; magnetic separation ; DNA probes ; PCR ; quantitation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Amplification and detection of target DNA sequences are made possible in a polymerase chain reaction (PCR) by using a mixture of biotinylated and ruthenium(II) trisbipyridal (Ru(bpy)32+)-end-labelled primers. In this way, biotin for capture and Ru(bpy)32+ for detection are directly incorporated into the PCR product obviating subsequent probe hybridization. PCR of a bacterial DNA template from Alteromonas species strain JD6.5 using a cocktail of biotin- and Ru(bpy)32+-labelled primers amplified a 1 kilobase region. Serial dilution of PCR product followed by magnetic separation with Streptavidin (SA)-coated magnetic beads and an electrochemiluminescence (ECL) assay using the semi-automated QPCR System 5000 demonstrated sensitive (pg range) DNA detection. ECL assay of probe hybridization to a human immunodeficiency virus (HIV) sequence also produced pg level sensitivity. Quantitative DNA determination by ECL assay correlated well with visual detection of DNA in electrophoretic gels. However, DNA detection by ECL assay was 10 to 100 times more sensitive than conventional ethidium bromide staining. The combination of DNA-based magnetic separation with ECL assay provides a very sensitive and rapid method of quantitating DNA which, owing to its rapid and facile nature, may have many applications in the research, environmental monitoring, industrial and clinical fields.
    Additional Material: 5 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal of Morphology 167 (1981), S. 65-90 
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Prenatal development of the eye in a microphthalmic hamster strain (“anophthalmic white”) is compared with established normal developmental periods. The mutant eye primordium is first distinguished at an average of ten gestational days (Period 6) by an incompletely invaginated optic cup, uniformly pseudostratified outer neuroepithelial layer and widely separated margins of the optic fissure. The outer layer of the mutant cup subsequently becomes abnormally thickened, especially posteriorly and midventrally, and, except in a few eyes with localized imperfect fusion, the optic fissure is unfused at twelve days (Period 9), by which time fusion is normally complete. At 13 to 15 days (Periods 10-11) the fissure is unfused or irregularly fused in regions of variable location and extent. The occurrence of fissure fusion with concomitant loss of continuity between inner and outer epithelial layers is generally restricted to expanded anterior regions in 14-16 day (Periods 11-12) eyes. The presence of presumptive neural retina in the outer layer of the cup characterizes the mutant eye; and to varying degrees, in day 13-16 eyes, the presumptive neural retina (1) provides persistent continuity between the two cup layers, (2) forms both fused and unfused margins of the optic fissure, and (3) extends into an outer position of the optic cup. As early as 13 days (Period 10), nerve fibers are present in the outer layer of the cup, and by the last prenatal and first postnatal days (Period 12), ectopic nerve fiber bundles are widely distributed.
    Additional Material: 43 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 142 (1990), S. 480-487 
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Treatment of M5076 tumor cells with the phorbol esters 12-O-tetradecanoyl-phorbol 13-acetate (TPA) and phorbol 12, 13 dibutyrate (PdBu) inhibited cellular proliferation, whereas 1,2-dioctanoyl-glycerol (DiC8) and 1-oleoyl2-acetyl-glycerol (OAG) did not affect cell growth. Inhibition of cellular proliferation in this cell line appears to be a consequence of protein kinase C (PKC) down-regulation since phorbol esters, but not a single application of diacylglycerols (DGs) down-regulated cellular PKC levels. By repeated application of DGs, PKC down-regulation was achieved and correlated with inhibition of proliferation. Phorbol ester-induced PKC down-regulation was reversible, upon removal of the phorbol ester, and the reappearance of PKC was associated with resumption of proliferation. The mitogenic responsiveness of these cells to added serum depended upon cellular PKC levels. Phorbol esters also caused the phosphorylation of two proteins which were not phosphorylated in response to DG treatment. Inhibition of growth of M5076 cells appears to be associated with phosphorylation of two novel proteins and/or PKC down-regulation.
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  • 10
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 47 (1960), S. 75-89 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The polymerization of methyl methacrylate and isopropyl acrylate in toluene with phenyl-H3-magnesium bromide has been studied at 0 and -70°C., respectively. Comparison of number-average molecular weights calculated from measurement of radioactivity and from measurements of appropriate colligative properties has shown that there is one and only one phenyl group per chain. Thus, initiation in this system is by 1,4-addition of the organomagnesium compound to the monomer. Methyl methacrylate, isopropyl acrylate, ethyl acrylate, and methyl acrylate were polymerized in toluene with phenylmagnesium bromide as the initiator. Isolation and identification of all the products have shown that, in addition to polymer, there are formed small amounts of two ketones and a hydrocarbon. Data are presented indicating that the principal mode of termination is via an intramolecular cyclization to give chains having a β-ketoester group on the end (arising from intramolecular reaction). A rationale for the stereospecificity, the termination reaction, and the large ratios of weight-average to number-average molecular weight in these polymerizations is proposed.
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