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  • 1980-1984  (5)
  • 1950-1954
  • 1900-1904
  • Life and Medical Sciences  (3)
  • Polymer and Materials Science  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Kinetics of macromolecules reacting with ligand (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 857-883 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to get an idea of the transient and stationary behavior to be looked for in a biological macromolecular system such as an enzyme or respiratory protein in the presence of its ligands, we have studied the coupled kinetic equations applicable to a simple allosteric model, based on the concerted two-state model of Monod et al. [(1965) J. Mol. Biol. 12, 88-118]. Exact solutions of the equations are given for three special cases, and two complementary methods are developed to generate approximate solutions in the general case, always, however, with the assumption that the equations are linear due to maintenance of ligand activity at a constant level. Subject to this assumption, these approximation methods have applicability to coupled rate equations beyond those considered here. As an illustration of how the results can provide the basis for a detailed analysis of actual kinetic data on working proteins, the formalism is applied to the kinetics of binding of oxygen by hemoglobin. An important result is that although time evolution to the steady state is in principle determined by several relaxation times, the effect of cooperativity for the case considered is to establish the dominance of one of them relative to the others. This suggests that for a macromolecule with a large number of binding sites, only one, or at most a few, of the many possible relaxation times are significant for specification of cooperative kinetics. The methods developed here, which will be applied more extensively elsewhere, provide a systematics for finding these dominant relaxation times.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190411
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A two-parameter model for estimating hydrogen bond enthalpies of reaction (1980)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 25 (1980), S. 2975-2984 
    Details
    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: A two-parameter equation is developed that allows for the estimation of the enthalpies of hydrogen formation between two compounds. The compound acting as a proton donor is assigned a donating parameter, and the compound acting as a proton acceptor is assigned an accepting parameter. The compounds described can be assigned both a donating and an accepting parameter. These parameters are derived either from the observed linear relationship between measured hydrogen bond enthalpies and the shift in the OH stretching frequency of alcohols or from the estimated contribution of hydrogen bonding to the cohesive energy density of liquids. The donating parameters correlate well with observed autoprotolysis constants for the several compounds, and the accepting parameters correlate well with observed equilibrium constants for the protonation reaction in which a compound (base) gains a proton. The ability to estimate enthalpies is important in predicting polymeric resin solubilities in solvents.
    Additional Material: 9 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1980.070251228
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Regulation of production of a platelet-derived growth factor-like protein by cultured bovine aortic endothelial cells (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 121 (1984), S. 298-308 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Platelet-derived growth factor (PDGF) is a potent mitogen for cultured cells of mesenchymal origin. Known sources of PDGF or PDGF-like protein are blood platelets, several transformed cell lines, and cultured endothelial cells (EC). We have examined the regulation of production of a PDGF-like protein in cultures of bovine aortic EC using a specific radioreceptor assay for PDGF. EC constitutively secreted PDGF-like protein into serum-containing or serum-free medium. The rate of production of PDGF-like protein was constant for at least 3 weeks and was not due to release of an internal store, since cell lysis by repeated freeze/thaw cycles did not relase significant amounts of the protein. Synthesis of PDGF-like protein was sensitive to changes in the pH of the media and was maximal at pH 8.5. Production of PDGF-like protein was independent of EC growth rate: rapidly dividing cells and confluent, quiescent cells produced equal amounts per cell. However, sparse, quiescent EC produced more PDGF-like protein per cell than did confluent, quiescent cells. Several phorbol esters stimulated production of PDGF-like protein. At a concentration of 10-6 M, a twofold stimulation was observed upon addition of the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) and nearly a fourfold stimulation upon addition of the nonpromoting analog, methyl TPA. Incubation of EC with endotoxin (10 μ/ml) resulted in a twofold stimulation of PDGF-like protein production. In all experiments with endotoxin and phorbol esters, an increase in the production of PDGF-like protein was accompanied by morphological changes in the EC cultures. The cells appeared elongated and fibroblastic and exhibited low viability. A mathematical model was developed in which PDGF-like protein production was shown to consist of two separate components - production at a constant rate by healthy cells and a large burst of synthesis and secretion by dying cells. These results suggest that injurious agents may be capable of stimulating production of a growth factor by the endothelium.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041210206
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  • 4
    Electronic Resource
    Electronic Resource
    Biochemical properties of the endothelium-derived growth factor: Comparision to other growth factors (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 114 (1983), S. 339-345 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Cultured bovine aortic endothelial cells (BAEC) can be maintained at saturation density for several weeks in the absence of serum. These cells retain viability and normal culture morphology, and continuously produce a growth factor for mesenchymally derived cells-the endothelium-derived growth factor (EDGF). The amount and specific activity of EDGF that is produced by BAEC under serum-free conditions remains constant for weeks. The levels of EDGF produced under these serum-free conditions is equivalent to levels produced in medium containing 5% plasma-derived serum. EDGF has been found to be trypsin sensitive, acetone and ammonium sulfate precipitable, and resistant to heat and sodium dodecyl sulfate treatment. Gel filtration on Sephacryl S-200 in the presence of formic acid (1%) yields two major peaks of activity corresponding to proteins of apparent molecular weights of approximately 24,000 and 14,000 daltons. This chromatographic step affords a ten-to 12-fold purification with a combined recovery of greater than 85%. Unlike brain or pituitary fibroblast growth factor, EDGF activity is destroyed by dithiothreitol or periodic acid. EDGF is not a somatomedin since it exhibits no detectable sulfation activity in a porcine cartilage assay. EDGF is not inhibited by antiserum to epidermal growth factor and is capable of stimulating DNA synthesis in a 3T3 variant cell line that is nonresponsive to and lacks receptors for epidermal growth factor. The majority of EDGF activity does not behave like the platelet-derived growth factor during ion exchange chromatography. Antisera prepared in rabbits and in mice to human platelet-derived growth factor has little effect on bivine or human EDGF activity. These biochemical and immunological properties of EDGF indicate that it is distinct from several other well-characterized polypeptide growth factors.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041140313
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  • 5
    Electronic Resource
    Electronic Resource
    The intracellular ratio of the membrane to the secreted form of immunoglobulin M heavy chain is a measure of the developmental stage of B cell lymphomas (1982)
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 3 (1982), S. 53-68 
    Details
    ISSN: 0192-253X
    Keywords: B cell development ; immunoglobulin M ; B cell tumor ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Tumors of B lymphocyte origin have been used as models for normal B cells “frozen” at particular stages of their development. Surface properties, amount, and intracellular location of immunoglobulin and the synthesis of J chain have all been used as indicators of developmental stages. Each requires special techniques or yields data that are difficult to compare from one experiment to the next. For these reasons, we have developed a metric for B cell development that is simple to perform and allows quick quantitative comparisons of cell lines.It has recently been established that the membrane (μm) and secreted (μs) forms of the IgM heavy chain differ at their extreme carboxy termini. The two proteins differ slightly in size and are easily distinguished when they are compared without their carbohydrate on sodium dodecyl sulfate (SDS) polyacrylamide gels. We have examined four mouse tumors derived from the B lymphocyte lineage whose phenotypes resemble late pre-B cells (internal μ only; uninduced 70Z/3), small B lymphocytes (high levels of surface IgM; LPS-induced 70Z/3, WEHI 231), lymphoblasts (both membrane and secreted IgM; WEHI 279.1), and plasma cells (copious IgM secretion; MOPC 104E). Despite the fact the 70Z/3 and WEHI 231 secrete no detectable IgM, all of the tumors synthesize at least intracellular forms of both μm and μs. The proportion of μm is stable and is characteristic of each tumor. The 70Z/3 cells and WEHI 231 cells synthesize about 75% of their total μ as μm; WEHI 279.1 cells synthesize about 30% and MOPC 104E cells about 5% of their total μ as μm. The population of LPS-stimulated B lymphocytes shows a similar progression during its differentiation. The proportion of μm correlates with other developmentally regulated parameters (Fc receptor, Ia and plasma cell antigen levels, and J chain) and can be used as a simple metric for comparison with developing B lymphocytes and determination of the developmental stage of a B cell tumor.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/dvg.1020030106
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