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  • Life and Medical Sciences  (14)
  • Polymer and Materials Science  (14)
  • 1980-1984  (26)
  • 1950-1954  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Conformation and folding in histones H1 and H5 (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 113-118 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Denatured histones H1 and H5 can be readily refolded on salt addition. Their digestion by trypsin leads to limit peptides of about 80 residues having the same nmr and CD spectra as those of the intact parent histones. Scanning microcalorimetry shows that (1) the folded structures of H1 and H5 are located entirely in their limit peptides; (2) both have values of the specific denaturation enthalpy typical for small globular proteins; and that (3) both exhibit a classic “2-state” transition (ΔHdcal = ΔHdvan't Hoff). The heat-denaturation profiles of H5 measured using intrinsic and extrinsic Cotton effect and side-chain nmr peaks do not coincide at all. Only the intrinsic Cotton effects give a Tm and ΔHdvan't Hoff close to that from microcalorimetry. We conclude that these proteins exhibit large-scale side-chain motions that precede the macroscopic cooperative transition.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360220118
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  • 2
    Electronic Resource
    Electronic Resource
    Pigment cell differentiation in the fire-bellied toad, Bombina orientalis. I. Structural, chemical, and physical aspects of the adult pigment pattern (1984)
    New York, NY : Wiley-Blackwell
    Journal of Morphology 179 (1984), S. 229-242 
    Details
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Wild-collected adults of Bombina orientalis are bright green dorsally and red to red-orange ventrally. As a prelude to an analysis of the differentiation of pigment cells in developing B. orientalis, we describe structural and chemical aspects of the fully differentiated pigment pattern of the “normal” adult.Structurally, differences between dorsal green and ventral red skin are summarized as follows: (1) Dorsal green skin contains a “typical” dermal chromatophore unit comprised of melanophores, iridophores, and xanthophores. Red skin contains predominantly carotenoid-containing xanthophores (erythrophores), and skin from black spot areas contains only melanophores. (2) In ventral red skin, there is also a thin layer of deep-lying iridophores that presumably are not involved in the observed color pattern. (3) Xanthophores of red and green skin are morphologically distinguishable from each other. Dorsal skin xanthophores contain both pterinosomes and carotenoid vesicles; ventral skin xanthophores contain only carotenoid vesicles. Carotenoid vesicles in dorsal xanthophores are much larger but less electron dense than comparable structures in ventral xanthophores.The presence of carotenes in ventral skin accounts for the bright red-orange color of the belly of this frog. Similar pigments are also present in green skin, but in smaller quantities and in conjunction with both colored (yellow) and colorless pteridines. From spectral data obtained for xanthophore pigments and structural data obtained from the size and arrangement of reflecting platelets in the iridophore layer, we attempt to explain the phenomenon of observed green color in B. orientalis.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jmor.1051790303
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  • 3
    Electronic Resource
    Electronic Resource
    Conformational properties of central nervous system myelin basic protein, β-endorphin, and β-lipotropin in water and in the presence of anionic lipids (1981)
    New York : Wiley-Blackwell
    Biopolymers 20 (1981), S. 1421-1434 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformational properties have been examined for three proteins which are disordered when dissolved in water but become partially ordered in the presence of anionic lipids. The three proteins, which play important roles in the central nervous system, are myelin basic protein, β-endorphin, and β-lipotropin. When evaluated using matrix methods, the helical content of each protein is predicted to be vanishingly small in water, in agreement with experiment. Unperturbed root-mean-square radii of gyration are also evaluated for these proteins in water using generator matrices, which have seen wide application to synthetic polymers. Agreement between computed and measured dimensions is found to be excellent. Having successfully described the conformations of myelin basic protein, β-endorphin, and β-lipotropin in water, attention is then directed to the changes induced upon interaction with anionic lipids or detergents. Computations predict an increase in helical content, with numerical results being in quite good agreement with experimental observations using several anionic lipids. Examination of the helix-propagation-probability profiles reveals an interesting feature of regions where this probability is high. When folded into a α-helix, these regions show one surface where the only side chains are hydrophobic. Charged side chains (with positive charges predominating) are found on the other surface of the helical segment. The arrangement of side chains on these helices is thus well suited to promote favorable interactions with a membrane containing anionic lipids. Examples of the occurrence of these helices are provided by amino acid residues 13-25 and 130-157 in myelin basic protein and residues 17-29 in β-endorphin.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1981.360200706
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  • 4
    Electronic Resource
    Electronic Resource
    Lipid-induced conformational changes in glucagon, secretin, and vasoactive intestinal peptide (1982)
    New York : Wiley-Blackwell
    Biopolymers 21 (1982), S. 1217-1228 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The CD of glucagon, secretin, and vasoactive intestinal peptide has been studied as a function of temperature in water and in aqueous solutions of dodecyl sulfate, phosphatidyl glycerol, and L-α-phosphatidic acid (dipalmitoyl). The anionic detergent and lipids induce helix formation in all three peptides, with the amount of induced helical content increasing in the order glucagon 〈 secretin 〈 vasoactive intestinal peptide. These observations are subject to quantitative rationalization using a matrix formulation for the configuration partition function. In this formulation the major conformational consequences of the interaction with anionic lipids or detergents is an increase in the probability for helix formation by arginyl, histidyl, and lysyl residues. The region in which helix formation is maximal is found to be at amino acid residues 13-20 in all three peptides. Other studies have implicated this portion of the polypeptide chain in receptor binding. Thus, the helical segment induced by interaction with anionic lipids may play an important physiological role.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360210615
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  • 5
    Electronic Resource
    Electronic Resource
    Behavior of amphipathic helices on analysis via matrix methods, with application to glucagon, secretin, and vasoactive intestinal peptide (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 1003-1021 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A configuration partition function, which incorporates concepts embodied in the amphipathic helix hypothesis, has been formulated for a polypeptide in the presence of zwitterionic phospholipid. An enhanced probability is assigned to helix formation in any region of the polypeptide chain where side chains bearing charges of opposite sign will be situated on the same side of the α-helix but displaced from one another by one turn. This situation will arise when residues i - 4 (or i - 3) and i bear charges of opposite sign and residue i - 4 (or i - 3) through i are in a helical state. Illustrative calculations are performed for polypeptide chains in which the generalized nonionic amino acid residue serving as host has Zimm-Bragg parameters of σ = 10-4, s = 1. These calculations define conditions under which two interacting charged pairs can cooperate in a synergistic helix augmentation even when the two pairs are separated by significantly more than four generalized nonionic amino acid residues. Furthermore, the two interacting charged pairs, as well as the intervening amino acid residues, may become helical as one unit. Significant augmentation in helicity is observed with plausible values for the enhanced probablity assigned to helix formation for an interacting pair. This model predicts correctly that glucagon and secretin, but not vasoactive intestinal peptide, undergo a coil-to-helix trnsition in the presence of zwitterionic phospholipid. This prediction is made with plausible values for the parameter used to express the helicity enhancement. The experimental observation with zwitterionic phospholipids is the direct opposite of that seen for these three peptides in the presence of anionic lipids and detergents. In anionic lipids the amount of induced helicity is in the following order: glucagon 〈 secretin 〈 vasoactive intestinal peptide. Results obtained with these three peptides demonstrate that the nature of the head group of the lipid is important for lipid-protein interaction and that the resulting conformational changes can be rationalized by matrix methods.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360220317
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  • 6
    Electronic Resource
    Electronic Resource
    The membrane potential of Ehrlich ascites tumor cells: An evaluation of the null point method (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 106 (1981), S. 399-406 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effects of valinomycin (25 pM) on the membrane potential and on initial, passive Na+ and K+ movements have been determined in Ehrlich ascites tumor cells. The membrane potential of steady-state cells in a physiologic environment was - 23.2 mV. Addition of valinomycin induced a small, significant hyperpolarization (Vm = -29.6 mV) when averaged over the population tested. However, analyses of the response of individual cells to valinomycin showed two different potential effects: (1) the majority of cells hyperpolarized after treatment; but (2) a significant fraction depolarized when exposed to valinomycin. The Vm of steady-state cells incubated in saline with K+ at concentrations of 21 mM or 75 mM was - 21.4 mV and -22.0 mV, respectively. Addition of valinomycin to these cells was without effect on Vm, thus establishing the “null point” responses. Only for cells incubated in saline with a K+ of 75 mM was there agreement between Vm and K+ equilibrium potential (Vk). Determinations of cellular Na+ and K+ showed that valinomycin induced net losses of K+ and gains of Na+ by cells incubated in either physiologic saline or saline with a K+ concentration of 21 mM. However, the celular K+ of cells incubated in saline with a K+ concentration of 75 mM was unaltered by valinomycin. There was a two- to threefold increase in K+ permeability of the cell membrane in the presence of valinomycin. These results are consistent with the existence of two null points in the membrane-potential response to valinomycin: One is established when the membrane potential corresponds to Vk; the second occurs when the effects of valinomycin on K+ loss from the cell are exactly offset by its inhibition of active Na+ + K+ transport.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041060309
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  • 7
    Electronic Resource
    Electronic Resource
    Variable coupling of active NA+ + K+ transport in Ehrlich ascites tumor cells: Regulation by external NA+ and K+ (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 106 (1981), S. 407-418 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The effects of altered external sodium and potassium concentrations on steady state, active Na+ + K+ transport in Ehrlich ascites tumor cells have been investigated. Membrane permeability to Na+ and K+, intracellular [Na+] and [K+], and membrane potential were measured. Active cation fluxes were calculated as equal and membrane potential were measured. Active cation fluxes were calculated as equal and opposite to the net, diffusional leak fluxes. Elevation of external K+ (6-60 Mm)by equivalent replacement of Na+ (154-91 mM) inhibits both active Na+ and K+ fluxes, but not proportionally. This results in a decrease of the coupling ratio (rp = -Jkp/JpNa) as external K+ is increased. Elevation of external K+ (3-68 mM) at constant Na+ (92mM) inbibits Jpk, but is without effect on JpNa. The coupling ratio declines from 1.01 ± 0.14 to 0.07 ± 0.05, a 14-fold alteration. Reduction of external Na+ (154-25 mM) at constant K+ (6mM) depresses JpNa, but is without effect on Jpk. The coupling ratio increases from 0.63 ± 0.04 at 154 mM Na+ to 4.5 ± 2.04 at 25 mM Na+. The results of this investigation are consistent with the independent regulation of active cation fluxes by the transported species. Kinetic analysis of the data indicates that elevation of external sodium stimulates active sodium efflux by interacting at “modifier sites” at the outer cell surface. Similarly, external potassium inhibits active potassium influx by interaction at separate modifier sites.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041060310
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  • 8
    Electronic Resource
    Electronic Resource
    Regulation of granulopoiesis and distribution of granulocytes in early phase of bacterial infection (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 109 (1981), S. 17-24 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Studies have been carried out to determine the effect of bacterial infection on CSF production, CFU-C activation, and bacterial clearance by mature granulocytes in mice infected with Escherichia coli. These studies have shown that immediately after bacterial infection (5 minutes), serum colony-stimulating factor (CSF) levels and bone marrow colony-forming units in culture (CFU-C) levels are elevated. This is followed by oscillator rises in both of these parameters and the appearance of granulocytes in the infected site. With clearance of bacteria, CSF and CFU-C levels return to normal. These studies have indicated further that bacterial infection is a major stimulus for granulocyte production through the CSF-CFU-C system and that clearance of bacteria by mature granulocytes may serve as a negative feedback regulatory arm.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041090103
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  • 9
    Electronic Resource
    Electronic Resource
    Decreased epidermal growth factor binding in cells growth arrested in G1 by nutrient deficiency (1981)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 109 (1981), S. 517-524 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Previous studies have shown that the nontransformed AKR-2B mouse embryo derived cell line may growth arrest by two separate mechanisms in the G1 phase of the cell cycle-growth factor deficiency arrest (G0) and low molecular weight nutrient deficiency arrest. An examination of epidermal growth factor (EGF) receptors under the different resting or growth conditions has shown that rapidly growing cells or cells arrested due to growth factor deficiency have the expected amount of 125I-EGF binding with approximately 105 receptors per cell being present in G0 arrested cells. In contrast, cells arrested due to nutrient deficiency show a reduction in 125I-EGF binding to 10--20% of that observed under the other conditions. This effect appears to be due to decreased receptor number and not to a change in the affinity of the receptor. Stimulation of DNA synthesis by nutrient replenishment causes a tenfold increase in EGF binding 20 hours later, with some increase in binding being detectable as early as six hours. The increase in binding is inhibited by cycloheximide and actinomycin D. This suggests that new mRNA synthesis as well as increased protein synthesis is required for the increase in EGF binding.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041090318
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  • 10
    Electronic Resource
    Electronic Resource
    Comparative biochemical and cytochemical studies on superoxide and peroxide in mouse macrophages (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 115 (1983), S. 208-216 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Maximal rates of superoxide (O-2) release, and the cytochemical locales of peroxide staining in resident, elicited, and activated macrophages have been determined. Macrophages elicited into the peritoneum with either casein (1.2% w/v) or proteose-peptone (10.0% w/v) release about twice as much O-2 as macrophages activated by infection of the animals with either Listeria monocytogenes, or Bacille Calmette-Guerin (BCG) followed by immune boosting with Purified Protein Derivative (PPD) (i.e., about 35 vs. 14-18 nmol O-2/min/107 cells). Macrophages elicited with thioglycollate (3.0% w/v) and resident macrophages produce negligible amounts of O-2 upon stimulation with PMA. These data are compared with those reported by other investigators who used different procedures. A cytochemical procedure for localizing peroxide has been modified for use with murine macrophages. No production of H2O2 by macrophages is detected cytochemically in the absence of stimulation. Upon exposure to PMA, resident macrophages are still largely unresponsive. Approximately 20% of the casein elicited macrophages and BCG-PPD activated macrophages exhibit H2O2 staining, which is largely restricted to the cytoplasmic vesicles and channels induced by PMA in these cells. The only exception to this staining pattern is a small population (about 2%) of activated macrophages which exhibits H2O2 staining in the cytoplasmic vesicles and channels and on the plasmalemma as well.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041150216
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