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  • Polymer and Materials Science  (30)
  • Industrial Chemistry and Chemical Engineering  (4)
  • Key words Brood parasitism  (4)
  • Life Sciences
  • 1995-1999  (38)
  • 1970-1974  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Spatial patterns of egg laying and multiple parasitism in a brood parasite: a non-territorial system in the great spotted cuckoo (Clamator glandarius) (1998)
    Springer
    Oecologia 117 (1998), S. 286-294 
    Details
    ISSN: 1432-1939
    Keywords: Key words Brood parasitism ; Clamator glandarius ; Egg laying ; Multiple parasitism ; Territory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We analysed the spatial and temporal pattern of egg laying in great spotted cuckoo females using microsatellite typing to determine parentage of the eggs and nestlings found in host (magpie) nests. The results showed that there were no exclusive laying territories in the study area. Cases of multiparasitism could be due to single females laying two or more eggs in a nest, or to several females using the same nest. In the latter case multiparasitism was due to a shortage of available host nests. We argue that the need for very large laying areas and the likely small cost of sharing parental care for chicks make the costs of defending territories higher than the benefits, which has constrained the evolution of territoriality in this species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050660
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  • 2
    Electronic Resource
    Electronic Resource
    Micro-evolutionary change and population dynamics of a brood parasite and its primary host: the intermittent arms race hypothesis (1998)
    Springer
    Oecologia 117 (1998), S. 381-390 
    Details
    ISSN: 1432-1939
    Keywords: Key words Brood parasitism ; Clamator glandarius ; Coevolution ; Parasite counter-defences ; Pica pica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A long-term study of the interactions between a brood parasite, the great spotted cuckoo Clamator glandarius, and its primary host the magpie Pica pica, demonstrated local changes in the distribution of both magpies and cuckoos and a rapid increase of rejection of both mimetic and non-mimetic model eggs by the host. In rich areas, magpies improved three of their defensive mechanisms: nest density and breeding synchrony increased dramatically and rejection rate of cuckoo eggs increased more slowly. A stepwise multiple regression analysis showed that parasitism rate decreased as host density increased and cuckoo density decreased. A logistic regression analysis indicated that the probability of changes in magpie nest density in the study plots was significantly affected by the density of magpie nests during the previous year (positively) and the rejection rate of mimetic model eggs (negatively). These results are consistent with a hypothesis (the intermittent arms race hypothesis) of spatially structured cyclic changes in parasitism. During periods of parasitism, host defences continuously improve, and as a consequence, the fitness gains for parasites decrease. When host defences against parasites reach a high level, dispersing parasites have a selective advantage if they are able to emigrate to areas of low resistance. Once parasites have left an area hosts will lose their defensive adaptations due to their cost in the absence of parasitism. The scene is then set for re-colonization by great spotted cuckoos.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050671
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  • 3
    Electronic Resource
    Electronic Resource
    Preferential allocation of food by magpies Pica pica to great spotted cuckoo Clamator glandarius chicks (1995)
    Springer
    Behavioral ecology and sociobiology 37 (1995), S. 7-13 
    Details
    ISSN: 1432-0762
    Keywords: Key words Brood parasitism ; Clamator glandarius ; Food allocation ; Pica pica ; Supernormal stimulus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Adult magpies Pica pica provide parasitic great spotted cuckoo Clamator glandarius nestlings with a diet very similar to that fed to their own chicks. In both naturally and experimentally parasitized nests, great spotted cuckoo chicks were fed at a higher rate than magpie chicks in the same nest. This preferential allocation of food by magpie parents to great spotted cuckoo chicks is consistent with the supernormal stimulus hypothesis, because this result implies that cuckoo chicks provide stronger stimuli for parental care than host chicks. Great spotted cuckoo chicks receive most of the food brought to the nest by the foster parents, because they exploit a series of stimuli which jointly (or sometimes individually) operate as a supernormal stimulus. This hypothesis predicts that if any stimulus is masked, the efficiency of the cuckoo in eliciting parental care will decrease. Here, we analyze experimentally the effects of two of these stimuli, preferential feeding of large nestlings and of nestlings with conspicuous palatal papillae. Firstly, when we experimentally introduced one medium-sized (7–9 days) cuckoo chick into an unparasitized magpie nest where the largest magpie chick was 12–15 days old, the cuckoo did not receive significantly more food than the average or the largest magpie chick. Secondly, when unparasitized nests were experimentally parasitized with a cuckoo chick that had its gape painted to mimic that of magpie chicks, the parasitic cuckoo received less food than the average magpie chick.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002650050167
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  • 4
    Electronic Resource
    Electronic Resource
    Chick recognition and acceptance: a weakness in magpies exploited by the parasitic great spotted cuckoo (1995)
    Springer
    Behavioral ecology and sociobiology 37 (1995), S. 243-248 
    Details
    ISSN: 1432-0762
    Keywords: Key words Brood parasitism ; Clamator glandarius ; Chick recognition ; Pica pica ; Supernormal stimulus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hosts of brood parasites have evolved the ability to discriminate nonmimetic and even mimetic eggs, but not nonmimetic chicks. Here we demonstrate that the great spotted cuckoo Clamator glandarius does not provide its magpie Pica pica host with a supernormal stimulus that helps to avoid recognition, because single cuckoo chicks introduced into otherwise unparasitized magpie nests are not fed at a higher frequency than single magpie chicks introduced to parasitized magpie nests. Another series of experiments demonstrated that magpies have the ability to discriminate cuckoo chicks, mainly when these are introduced at the end of the nestling period, and especially when the cuckoo chick together with a magpie chick is presented to adult magpies outside the nest. This supports the idea that cuckoos exploit the obligatory reaction of magpies to feed all young that have been hatched in their nests and whose “signatures” they have learnt. Furthermore, the experimental cuckoo chicks in parasitized magpie nests were more likely to be accepted than they were in nonparasitized nests. This supports the hypothesis that magpies may learn to recognise their own nestlings as those present in the nest and may indicate that a comparison between cuckoo and magpie nestlings is the basis of discrimination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002650050187
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  • 5
    Electronic Resource
    Electronic Resource
    Fracture of DNA in transient extensional flow. A numerical simulation study (1996)
    New York : Wiley-Blackwell
    Biopolymers 39 (1996), S. 435-444 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the Brownian dynamics simulation technique, we studied the fracture process of DNA chains subjected to transient extensional flow, letting the solution with DNA molecules pass through a very small orifice (radius = 0.0065 cm), thus experiencing extensional flow of the convergent (sink) type. The DNA molecules were modeled as FENE bead-spring chains with the springs obeying a modified Warner force law, as proposed by Reese and Zimm. The fracture yield was strongly dependent on flow rate and molecular weight, reaching, in our setup, a level of 100% at a flow rate of around 0.001 cm3/s for DNA with molecular weight 26 × 106 (T7 DNA). There was found to exist a critical flow rate (Qcrit) below which fracture did not occur, in accordance with what was observed in studies on polystyrene in transient extensional flow. We found that for DNA, the critical flow rate depended on the molecular weight as Qcrit ∼ M-14 when the hydrodynamic interaction effect (HI) was not included in the simulations. When HI was accounted for, the relation was found to be Qcrit ∼ M-1.1, close to the theoretical prediction for fracture of partly extended chains in transient extensional flow. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Conformationally readdressed CCK-B/δ-opioid pepitide ligands (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 439-452 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sequence of a cholecystokinin (CCK) related peptide was modified to obtain analogues, which intereact selectively either with CCK-B, or with δ-opioid receptors. Two kinds of peptides were designed, namely, the cyclic peptides of the H-Tyr-cyclo(D-Pen-Gly-Trp-L-/D-3-transmecaptoproline)-Asp-Phe-NH2 sequence (compounds 1a and 1b, respectively), and the linear peptides of the H-Tyr-D-Val-Gly-Trp-L/D-3-trans-methylmercaptoproline-Asp-Phe-NH2 sequence (compounds 2a and 2b, respectively). The only difference between the chemical structures of the linear analogues compared to the cyclic ones is that one covalent bond has been eliminated and a sulfur atom is replaced by a methyl group. Molecular modeling showed that, among low-energy conformers of cyclic compounds 1, there are three-dimensional structures compatible to the model for δ- receptor- bound conformer, suggested earlier[G. V. Nikiforovich. V. J. Hruby. O. Prakash, and C. A. Gehrig (1991) Biopolymers. vol. 31. pp. 941-955]. Results of binding assays fully supported the rationale for the design of compounds 1 and 2. The cyclic analogue 1a has Ki values of 4.5 and 〉 5000 n M at δ- and μ-opioid receptors, respectively; IC50 values of 3000 n M for both CCK-A and CCK-B receptors, whereas its linear counterpart 2a has ki values of 462 and 229 nM at δ- and μ-opioid receptors, respectively; and IC50 values of 1.6 and 〉 10.000 nM for CCK-A and CCK-B receptors, respectively. The results of this study demonstrate a possibility to redirect a peptide sequence that interacts with one type of receptors (CCK-B receptors) toward interaction with another type (δ-opioid receptors) belonging to a different physiological system. This redirection could be performed by changing the conformational properties of the peptide with very minimal changes in its chemical structure. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360360407
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  • 7
    Electronic Resource
    Electronic Resource
    Poly(α-isobutyl-β-D,L-aspartate)s: Polymerization effects on configuration and crystal structure of the stereocopolymers (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 1959-1968 
    Details
    ISSN: 0887-624X
    Keywords: optically active polyamides ; helical nylons ; nylon-3 ; poly(β-amide)s ; poly(β-aspartate)s ; poly(α-isobutyl-β-L-aspartate) ; stereoselective polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Different polymerization methods were used for the preparation of poly(α-isobutyl-β-D,L-aspartate)s containing variable ratios of D- to L-aspartic units and the microstructure of the resulting stereocopolymers was examined by NMR spectroscopy. Anionic ring-opening polymerization in solution of enantiomeric mixtures of α-isobutyl-β-D- and L-aspartalactams was found to proceed stereoselectively rendering block copolymers composed of right- and left-handed helical sequences. Configurationally statistical copolymers were obtained instead when the enantiomeric lactam mixtures were polymerized in the bulk. Random stereocopolymers could be prepared also by polycondensation in solution of mixtures of pentachlorophenyl α-isobutyl-β-D and -L-aspartates. The conformation in solution and the crystal structure of the resulting copolymers were investigated in connection with their stereochemical configuration and these features compared with those displayed by optically pure poly(α-isobutyl-β-L-aspartate). © 1996 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Local chain configuration dependence of the mechanisms of analogous reactions of PVC. I. A conclusive study of the microstructure evolution in SN2 nucleophilic substitution (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2387-2397 
    Details
    ISSN: 0887-624X
    Keywords: poly(vinyl chloride) ; nucleophilic substitution ; stereospecific mechanisms ; solvent influence ; microstructural sensitivity ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nucleophilic substitution in poly(vinyl chloride) (PVC) with sodium benzenethiolate has been studied in two kinds of solvent differing in the molecular structure in the vicinity of the carbonyl group. From the evolution of the content of isotactic (mm), heterotactic (mr), and syndiotactic (rr) triads; and of mmmm, mmmr and rmmr isotactic pentads, in the unmodified parts of the polymer, as followed by 13C-NMR, it is unambiguously inferred that any chlorine but the central one of either the isotactic triad at mmr tetrads or the heterotactic triad at rmrr pentads is unreactive. Only a small fraction of mmr tetrads reacts occasionally by the central chlorine of its mr triad instead of the mm. Of those structures, the mmr, especially when located at the end of long isotactic sequences, proves to be highly reactive compared to the rmrr structure. By comparing quantitatively the microstructural changes with degree of substitution and taking into account that the reaction is of SN2 type, the mechanisms of substitution through the three foregoing reactive chlorines have been stated. They are found to be independent of the type of solvent and to account for all the changes in triad and pentad content as experimentally found. Instead, the solvent dependence of the ratio between the mmr- and rmrr-based processes of substitution is such that the depletion of mmr compared to that of rmrr structure may be controlled. The conformational sensitivity of this behavior is discussed on the basis of side work in our laboratory. As a whole, the results of the present work provide some original concepts as to the role of the tacticity dependent microstructure and the related local conformations in the chemical reactions of PVC. © 1996 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Local chain configuration dependence of the mechanisms of analogous reactions of PVC. II. A further evidence through the changes in conformationally sensitive FTIR bands with degree of nucleophilic substitution (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2563-2574 
    Details
    ISSN: 0887-624X
    Keywords: poly(vinyl chloride) ; stereoselective substitution ; FTIR vibration modes ; local configurational mechanisms ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The evolution of the ν C (SINGLE BOND) Cl bands of the infrared spectrum of a Bernoullian though slightly isotactic poly(vinyl chloride) (PVC), with both the degree of SN2 substitution reaction with sodium benzenethiolate, as studied earlier, and the increase of the nucleophile infrared bands, has been studied by FTIR spectroscopy. In a parallel way, the changes in the same bands, in particular those at 615 and 637 cm-1, presumably induced by SN2 substitution, have been estimated, theoretically, by comparing the sequential order and the number of the distinct conformationally sensitive vibration modes of C(SINGLE BOND)Cl bond, prior and after substitution, for a series of polymer sequences containing the reactive sites, namely the isotactic mmr tetrad and the heterotactic rmrr pentad, according to earlier work.The experimental behaviour of the νC(SINGLE BOND)Cl bands is found to be in close agreement with the theoretical expectations, thereby allowing two main conclusions to be drawn: (i) during the early stage going up to conversions of 10-12%, the reaction proceeds in a nearly exclusive manner, by the mmr and rmrr terminal of long isotactic and syndiotactic sequences, respectively; and (ii) any reaction event throughout the substitution process proves to be highly dependent upon the local environment in which each of the foregoing reactive structures finds itself. In summary, the local configurational nature of the mechanisms of analogous reactions of polymers is strongly suggested on the grounds of the results given herein. © 1996 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis of poly(aryl ether) dendrimers using an aryl carbonate and mixtures of metal carbonates and metal hydroxides (1997)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 35 (1997), S. 1781-1798 
    Details
    ISSN: 0887-624X
    Keywords: poly(aryl ether) dendrimers ; cascade polymers ; polyetherification reaction ; divergent approach ; activation/condensation sequence ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Four generations of poly(aryl ether) dendrimers containing aryl sulfide or aryl sulfone groups, and aryl fluoride terminal functionality, have been synthesized using the divergent initiator core method and bis(4-fluorophenyl) sulfone as the core precursor. The strategy is based on the divergent approach and an activation/condensation sequence that involves oxidation of the aryl sulfide group and the displacement of the activated halide moiety by a phenolate ion. The phenolate is easily generated in situ from an aryl carbonate. No reaction intermediates were detected when the condensation reaction was carried out utilizing a very active metal carbonate, such as cesium carbonate, in conjunction with magnesium hydroxide or calcium carbonate which removes some of the fluoride ions formed. The samples were characterized by HPLC, MALDI-TOF-MS, NMR, and SEC. Imperfections in some of the molecules of the dendrimers, formed by reaction of the core precusors with an impurity present in the phenol, were also identified by MALDI-TOF-MS. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1781-1798, 1997
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