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  • Blackwell Publishing Ltd  (7)
  • Public Library of Science
  • American Physical Society (APS)
  • 1995-1999  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    The @journal of eukaryotic microbiology 45 (1998), S. 0 
    ISSN: 1550-7408
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Bacterial epibionts were observed on the surface of the marine sediment ciliate Geleia fossata. Rod-shaped bacteria, from 2-10 X103 per ciliate, were universally positioned in ciliated grooves, in apparent spatial association with dikinetids. SEM and TEM examination of the ciliates confirmed that a tight affiliation exists between the epibiotic bacteria and ciliate cortex infrastructures. These observations, as well as the distinct bacterial distribution pattern over ciliate surface, suggest that there is a close epibiont/host physiological integration. Epibiotic bacteria were also observed on the surfaces of other sediment ciliates from the genera Loxophyllum, Tracheloraphis, Geleia, Paraspathidium, and Cyclidium. These findings indicate that the bacterial/protozoa associations are widespread in the marine benthic environment. The potential benefits for both epibionts and their hosts are discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Forest pathology 27 (1997), S. 0 
    ISSN: 1439-0329
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Conidia of Leptographium wageneri var. ponderosum, Leptographium wageneri var. pseudotsugae and Leptographium wageneri var. wageneri germinated on wounded roots of ponderosa pine (Pinus ponderosa), Douglas fir (Pseudotsuga menziesii), and pinyon (Pinus edulis), but not on unwounded roots. On wounds, germination occurred regardless of the combination of pathogen variety and plant species. When wounded roots of ponderosa pine and Douglas fir seedlings were inoculated with conidia of L. w. var. ponderosum and L. w. var. pseudotsugae, respectively, 87-100% of the seedlings became infected. When unwounded roots were inoculated with wooden blocks colonized with L. wageneri, 60-66% of the seedlings became infected.The development of L. w. var. ponderosum and L. w. var. pseudotsugae on agar was compared with their development on agar overlaid with either cellophane or Nucleopore membranes. Undulating hyphae were found commonly in and on the agar, but less frequently on the membranes. On both membranes, mycelia formed mats which were tightly appressed to the surface; mats were not formed on the agar. On both agar and the membranes, two or more hyphae often formed a strand. When L. w. var. ponderosum mycelia were allowed to colonize the surface of an unwounded pine root, strands, undulating hyphae and poorly formed mats were seen.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 768 (1995), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Computational intelligence 12 (1996), S. 0 
    ISSN: 1467-8640
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Computer Science
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Computational intelligence 12 (1996), S. 0 
    ISSN: 1467-8640
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Computer Science
    Notes: As they gain expertise in problem solving, people increasingly rely on patterns and spatially oriented reasoning. This paper describes an associative visual-pattern classifier and the automated acquisition of new, spatially oriented reasoning agents that simulate such behavior. They are incorporated into a multi-agent game-learning program whose architecture robustly combines agents with conflicting perspectives. When tested on three games, the visual-pattern classifier learns meaningful patterns, and the pattern-based, spatially oriented agents generalized from these patterns are generally correct. The accuracy of the contribution of each of the newly created agents to the decision-making process is measured against an expert opponent, and a perceptron-Iike algorithm is used to learn game-specific weights for these agents. Much of the knowledge encapsulated by the new agents was previously inexpressible in the program's representation and in some cases is not readily deducible from the rules.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Auxin conjugates play a role in the regulation of free indole-3-acetic acid (IAA) content in plants. Not much is known about the enzymes involved in either conjugate synthesis or hydrolysis. In this study we have isolated and characterized an auxin conjugate hydrolase from Chinese cabbage seedlings and investigated it during the development of both the Chinese cabbage plants and the clubroot disease. The hydrolase isolated from light- and dark-grown seedlings accepted the amide conjugates indole-3-acetic acid-alanine (IAAla), IAA-phenylalanine (IAPhe), but not IAA-aspartate (IAAsp) as substrates. We also found a substantial amount of hydrolysis of an ester conjugate (IAA-glucose, IAGlu) in our enzyme preparation. The tentative reaction product IAA was identified by HPLC and subsequent GC-MS analysis. The pH optima for the different substrates were not identical, suggesting several hydrolase isoforms. After gel filtration chromatography we found at least two peaks containing different hydrolase isoforms. The isoform, which converted IAGlu to IAA, exhibited a molecular mass of ca 63 kDa, and an isoform of ca 21 kDa converted IAAla and IAPhe. The increased free IAA content in clubroot-diseased roots of Brassicaceae can be due to either de novo synthesis or release of IAA from conjugates. To answer this question free, ester- and amide-bound IAA was measured in 24- and 30-day-old leaves and roots of healthy and Plasmodiophora brassicae-infected Chinese cabbage, and the hydrolase activity with different substrates measured in the same tissues. The amide conjugates were dramatically enhanced in infected roots, whereas free IAA was only slightly enhanced compared to the control tissue. Hydrolase activity was also enhanced in clubbed roots, but the substrate specificity differed from that found in the seedlings. Especially, IAAsp hydrolysis was induced after inoculation with P. brassicae. We conclude that different auxin conjugates can be hydrolyzed at different developmental stages or under stress.
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  • 7
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The function and location of guard cells uniquely subject them to stress. First, stomatal movements require large fluctuations in the concentration of potassium salts. Second, guard cell inner walls are the first surfaces exposed to evaporation and apoplastic solutes may accumulate there as a result. We have therefore investigated whether guard cells exhibit atypical expression of dehydrin genes because dehydrins accumulate in vegetative tissues in response to water stress. We have also assayed for osmotin mRNA, which is up-regulated in leaves in response to various stresses. mRNA probes for several representative genes were used with RNA extracts from control and water-stressed Vicia faba leaflets. Correlatively, these probes were used with RNA extracts from “isolated’ guard cells that had been incubated with combinations of abscisic acid, mannitol and Ca2+. (Isolated guard cells are epidermal strips sonicated to destroy cells other than guard cells.) Hybridization with the probe prepared for a dehydrin from Pisum sativum (Psdhn 1) was detected in leaf extracts only if the leaf had been stressed. Similarly, after 1- and 6-h incubations with abscisic acid, isolated guard cells contained an mRNA that hybridized with the probe for Psdhn 1. Appearance of this abscisic acid-dependent mRNA required neither mannitol nor exogenous Ca2+. Regardless of the conditions or tissue, no hybridization was detected with the probe against osmotin, but our interpretation of this result is qualified. The simplest conclusion is that atypical expression of dehydrin is not the mechanism by which guard cells cope with their peculiar function and location.
    Type of Medium: Electronic Resource
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