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  • Springer  (27)
  • Springer Nature  (4)
  • 1995-1999  (31)
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  • 1
    Electronic Resource
    Electronic Resource
    Transport of Charged Dipeptides by the Intestinal H+/Peptide Symporter PepT1 Expressed in Xenopus laevis Oocytes (1997)
    Springer
    The journal of membrane biology 155 (1997), S. 247 -256 
    Details
    ISSN: 1432-1424
    Keywords: Key words: Intestinal peptide transporter — Expression — Substrate specificity — Two-electrode voltage-clamp technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. The cloned intestinal peptide transporter is capable of electrogenic H+-coupled cotransport of neutral di- and tripeptides and selected peptide mimetics. Since the mechanism by which PepT1 transports substrates that carry a net negative or positive charge at neutral pH is poorly understood, we determined in Xenopus oocytes expressing PepT1 the characteristics of transport of differently charged glycylpeptides. Transport function of PepT1 was assessed by flux studies employing a radiolabeled dipeptide and by the two-electrode voltage-clamp-technique. Our studies show, that the transporter is capable of translocating all substrates by an electrogenic process that follows Michaelis Menten kinetics. Whereas the apparent K0.5 value of a zwitterionic substrate is only moderately affected by alterations in pH or membrane potential, K0.5 values of charged substrates are strongly dependent on both, pH and membrane potential. Whereas the affinity of the anionic dipeptide increased dramatically by lowering the pH, a cationic substrate shows only a weak affinity for PepT1 at all pH values (5.5–8.0). The driving force for uptake is provided mainly by the inside negative transmembrane electrical potential. In addition, affinity for proton interaction with PepT1 was found to depend on membrane potential and proton binding subsequently affects the substrate affinity. Furthermore, our studies suggest, that uptake of the zwitterionic form of a charged substrate contributes to overall transport and that consequently the stoichiometry of the flux-coupling ratios for peptide: H+/H3O+ cotransport may vary depending on pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002329900177
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of a Homologous Series of Linear Alcohol Ethoxylate Surfactants on Fathead Minnow Early Life Stages (1999)
    Springer
    Archives of environmental contamination and toxicology 37 (1999), S. 536-541 
    Details
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. Effects of a homologous series of three primarily linear alcohol ethoxylate surfactants were studied in laboratory flow-through 28-day early-life-stage tests with fathead minnow (Pimephales promelas Rafinesque). Surfactants were a C9–11, C12–13, and C14–15 with an average of 6, 6.5, and 7 ethylene oxide units per mole of alcohol, respectively. Average measured surfactant recoveries were 103%, 81%, and 79% of nominal concentrations for the C9–11 EO 6, C12–13 EO 6.5, and C14–15 EO 7 studies, respectively. Embryo survival at 48 h was not adversely affected at any of the concentrations tested. Impaired hatching and deformed fry were observed only in the C12–13 EO 6.5 study. The 28-day LC50 values were 4.87, 2.39, and 1.02 mg/L for the C9–11 EO 6, C12–13 EO 6.5, and C14–15 EO 7 surfactants, respectively. The corresponding NOECs for survival were 1.01, 1.76, and 0.74 mg/L. Posthatch fry growth was more sensitive than survival for the C12–13 EO 6.5 and C14–15 EO 7 surfactants. Survival of posthatch fry decreased with increasing surfactant alkyl chain length. Twenty-eight-day laboratory data were compared to 96-h laboratory, 10-day laboratory and 30-day stream mesocosm data for fathead minnow previously determined for these surfactants. Survival endpoints from the different exposures were comparable and only varied within a factor of two. Similarity of results suggests that it is possible to effectively use 96-h, 10-day, or 28-day laboratory data to predict environmental effects concentrations of these surfactants for fish.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002449900549
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  • 3
    Electronic Resource
    Electronic Resource
    SET domain proteins modulate chromatin domains in eu- and heterochromatin (1998)
    Springer
    Cellular and molecular life sciences 54 (1998), S. 80-93 
    Details
    ISSN: 1420-9071
    Keywords: Key words. SET domain; Pc-G and trx-G genes; PEV in Drosophila; telomeric silencing; Su(var) and E(var) genes; chromatin domains.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The SET domain is a 130-amino acid, evolutionarily conserved sequence motif present in chromosomal proteins that function in modulating gene activities from yeast to mammals. Initially identified as members of the Polycomb- and trithorax-group (Pc-G and trx-G) gene families, which are required to maintain expression boundaries of homeotic selector (HOM-C) genes, SET domain proteins are also involved in position-effect-variegation (PEV), telomeric and centromeric gene silencing, and possibly in determining chromosome architecture. These observations implicate SET domain proteins as multifunctional chromatin regulators with activities in both eu- and heterochromatin – a role consistent with their modular structure, which combines the SET domain with additional sequence motifs of either a cysteine-rich region/zinc-finger type or the chromo domain. Multiple functions for chromatin regulators are not restricted to the SET protein family, since many trx-G (but only very few Pc-G) genes are also modifiers of PEV. Together, these data establish a model in which the modulation of chromatin domains is mechanistically linked with the regulation of key developmental loci (e.g. HOM-C).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000180050127
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  • 4
    Electronic Resource
    Electronic Resource
    Anomalous pH dependence of the coexistence pressure of the polymerizable two-chain N-lipid methyl-bis(pentacosadiinoyl-oxyethyl)-amine (1997)
    Springer
    European biophysics journal 26 (1997), S. 271-275 
    Details
    ISSN: 1432-1017
    Keywords: Key words Diacetylenic lipids ; Polymerization ; Microfluorescence ; Filmbalance ; AFM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Molecular films from polymeric materials play an important role in basic research as well as in technology. We have synthesized the double chain diacetylenic ammonium lipid N-bis-(10, 12-pentacosadiinoyl)-oxy-ethyl)-N-methyl-amine (ONCO). We have characterized monomolecular films at the air/water interface by means of microfluorescence filmbalance techniques and by atomic force microscopy (AFM). ONCO forms stable monomolecular films that exhibit a fluid-solid phase transition with a transition enthalpy of 90 kJ/mol at 10 °C and neutral pH. The coexistence pressure was found to decrease with decreasing protonation, which is in contrast to the commonly found Coulomb mechanism. A change in the chain packing due to a different nitrogen bond angle is discussed as a possible mechanism. This model is cor-roborated by the finding that crystals at high and at low pH differ in their polymerization properties as measured by microfluorescence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050080
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  • 5
    Electronic Resource
    Electronic Resource
    Herbivore-induced emissions of maize volatiles repel the corn leaf aphid, shape Rhopalosiphum maidis (1998)
    Springer
    Entomologia experimentalis et applicata 87 (1998), S. 133-142 
    Details
    ISSN: 1570-7458
    Keywords: Rhopalosiphum maidis ; Zea mays ; induced plant volatiles ; repellence ; (E)-β-farnesene ; alarm pheromone ; plant insect interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract When maize plants, Zea mays L., are mechanically damaged and the damaged sites are treated with caterpillar regurgitant, the plants will release a specific blend of volatiles. It is known that these volatiles can be attractive to natural enemies of herbivores. We hypothesise that the plant volatiles constitute part of the induced plant defence and that herbivores will be affected by the odours as well. In laboratory and semi-field studies this hypothesis was tested for the aphid Rhopalosiphum maidis (Fitch) (Rhynchota, Sternorrhyncha, Aphididae). In a Y-tube olfactometer significantly more aphids chose the odour of healthy, undamaged maize seedlings when tested against clean air or plants treated with regurgitant. Clean air was chosen more often when tested next to the odour of treated plants. This apparently repellent effect of the odour of treated plants was significant for winged aphids, but not for the wingless aphids. In field experiments aphids were released in the centre of circles of eight potted maize plants. Four plants in each circle were damaged and treated with caterpillar regurgitant while the other plants were left unharmed. At different intervals after aphid release, the number of aphids was counted on each plant. Significantly fewer winged and wingless aphids were found back on treated plants than on healthy plants. We suggest that herbivores may be repelled by the odours because they could indicate that: 1) the plant has initiated the production of toxic compounds; 2) potential competitors are present on the plant; 3) the plant is attractive to parasitoids and predators. Aphids may be particularly sensitive to induced maize volatiles because one of the major compounds emitted by the plant is (E)-β-farnesene, which is a common alarm pheromone for aphids. Collections and analyses of the odours emitted by crushed R. maidis confirmed that it too emits (E)-β-farnesene when stressed. The results are discussed in context of plant defence strategies and their possible exploitation for the control of pest insects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003200108763
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  • 6
    Electronic Resource
    Electronic Resource
    Instar-dependent hemocyte changes in shape Pieris brassicae after parasitization by shape Cotesia glomerata (1998)
    Springer
    Entomologia experimentalis et applicata 88 (1998), S. 49-58 
    Details
    ISSN: 1570-7458
    Keywords: Pieris brassicae ; Cotesia glomerata ; parasitoid ; hemocytes ; inhibition of encapsulation ; development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cotesia glomerata L. (Hymenoptera: Braconidae) is a parasitoid of early instar larvae of Pieris brassicae L. (Lepidoptera: Pieridae). Late instars of P. brassicae can more often overcome parasitization by hemocytic encapsulation of C. glomerata eggs. Short-term hemocyte responses to parasitization were examined in third and fourth instar larvae of P. brassicae. Total and differential hemocyte counts did not differ between parasitized and unparasitized host larvae. A rapid, but temporary decrease of total hemocyte as well as plasmatocyte numbers was observed immediately after oviposition. Numbers of hemocytes adhering to tissues were shown to be the same in untreated, wounded and parasitized P. brassicae larvae by tracing hemocytes with monoclonal antibodies as markers. The in vitro spreading ability of hemocytes from unparasitized third and fourth instar larvae was lower than that of the last instar's; parasitization, however, had no influence on hemocyte spreading. We therefore suggest that the higher parasitization success of C. glomerata in earlier instars of P. brassicae is mainly due to the low spreading ability of the hemocytes. Abbreviations: ACS – anticoagulant saline; BSA – bovine serum albumin; DABCO – 1,4-diazabicyclo-[2,2,2]-octane; DHC – differential hemocyte count; FITC – fluorescein isothiocyanate; GR – granular cells; LPS – lipopolysaccharide; mAb – monoclonal antibody; OE – oenocytoids; PL – plasmatocytes; PRO – prohemocytes; PS – Pieris saline; PVP – polyvinylpyrrolidone; TBS – tris-buffered saline; THC – total hemocyte count.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003256105692
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  • 7
    Electronic Resource
    Electronic Resource
    Flight behavior of pre- and postdiapause apple blossom weevils in relation to ambient temperature (1998)
    Springer
    Entomologia experimentalis et applicata 88 (1998), S. 97-99 
    Details
    ISSN: 1570-7458
    Keywords: Coleoptera ; Curculionidae ; Anthonomus pomorum ; temperature ; diapause ; flight behavior
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003269621622
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  • 8
    Electronic Resource
    Electronic Resource
    Spring behavioral patterns of the apple blossom weevil (1996)
    Springer
    Entomologia experimentalis et applicata 79 (1996), S. 9-17 
    Details
    ISSN: 1570-7458
    Keywords: Anthonomus pomorum ; temperature ; diel cycle ; Coleoptera ; Curculionidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Individual pairs of overwintered adult apple blossom weevils, Anthonomus pomorum (L.), confined with apple twigs under different ambient temperatures in the laboratory and on apple trees in the field, were observed through day and night for their spring activities. Flight behavior in relation to ambient temperature was also investigated under laboratory conditions using flight stands. Both sexes displayed predominantly nocturnal behavior patterns in both the laboratory and the field. Feeding, crawling, and mating activities increased following sunset in the field or onset of scotophase in the laboratory while resting occurred most frequently during daylight hours. Results of the laboratory experiments showed that temperature affected significantly the activity patterns. The diel pattern of activities became less distinctive at higher temperatures (above 15°C), and total activities in crawling, feeding, and mating were suppressed significantly at lower temperatures (below 5°C). Over 97% of the test weevils initiated take-off response from flight stands at 20°C within the 30 min trial period; however, flight initiation rarely occurred at temperatures 12°C or below. Overall, results of the laboratory and field experiments indicate that A. pomorum is a remarkably cold-adapted insect with ability to crawl, feed, and mate at a few degrees above freezing, a physiological attribute necessary for the exploitation of early stages of apple bud development in the cold early spring.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00333816
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  • 9
    Electronic Resource
    Electronic Resource
    Spring colonisation of orchards by Anthonomus pomorum from adjacent forest borders (1999)
    Springer
    Entomologia experimentalis et applicata 93 (1999), S. 131-139 
    Details
    ISSN: 1570-7458
    Keywords: dispersal ; mark-release-recapture ; Anthonomus pomorum ; apple blossom weevil ; Coleoptera ; Curculionidae ; apple orchard
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The early-season dispersal of the overwintered apple blossom weevil, Anthonomus pomorum (L.) (Coleoptera: Curculionidae), is a crucial stage in the colonisation of dwarf apple orchards adjacent to forests. We have conducted release-recapture studies with 1700 to 4000 marked weevils at two orchard sites in Switzerland over 2 years to characterise the spatial and temporal pattern of the dispersal process. The dispersal and colonisation of orchards in spring by overwintered weevils is dependent upon the prevailing temperature. An orientated dispersal from the forest border to the centre of the orchard was observed consistently, irrespective of the angle of the apple tree rows with respect to the forest border or of climatic conditions. The average dispersal distance of the weevils was 19 m. Approximately one third of the weevil population remained on the first tree encountered, the remainder of the population moved over short distances mainly along the tree rows. This dispersal pattern led to a strong ‘edge effect’ with higher numbers of weevils occurring at the edges adjoining the forests as compared to the centre of orchards. The relevance of these findings to population dynamics and management of the pest is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003844902445
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  • 10
    Electronic Resource
    Electronic Resource
    The influence of temperature on the life table of Hyperaspis notata (1997)
    Springer
    Entomologia experimentalis et applicata 84 (1997), S. 85-92 
    Details
    ISSN: 1570-7458
    Keywords: Coccinellids ; Hyperaspis notata ; life table statistics ; insect development ; intrinsic rates of increase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The coccinellid Hyperaspis notata Mulsant was introduced into Africa for the biological control of the cassava mealybug, Phenacoccus manihoti Matile-Ferrero. Two cohorts of strains, one originating from Southern Brazil and Paraguay feeding on P. manihoti, and one from Colombia feeding on Phenacoccus herreni Cox & Williams were studied at different temperatures between 15 and 34 °C and age-specific life tables were constructed. Although in the areas of origin the climatical conditions and the food sources are different, the survivorship and developmental times at the same temperature differed little among the two strains, the Colombian strain being slightly more tolerant to high temperatures. Jacknife estimates of the intrinsic rates of increase (rm) peaked very close to 30 °C for the two strains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003026314120
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