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  • Springer  (48)
  • American Chemical Society  (7)
  • American Institute of Physics (AIP)  (5)
  • American Society of Hematology  (2)
  • Wiley-Blackwell
  • 1995-1999  (18)
  • 1990-1994  (38)
  • 1980-1984  (7)
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Year
  • 11
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 53 (1982), S. 347-351 
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We conducted a greenhouse study of the effects of initial seed mass on seedling characteristics in a Panamanian population of Virola surinamensis, a canopy tree in which mean seed mass of different individuals ranges from 1.34 to 4.04g. The system is of particular interest because birds preferentially eat fruits of small-seeded plants, leaving seedlings of large-seeded individuals under conditions of potentially severe sibling competition (Howe and Vande Kerckhove 1980). Effects of differences of mean seed mass between trees are explored using an analysis of variance, while effects of seed-mass variation within crops are demonstrated with a regression analysis. A two-way analysis of variance decisively shows effects of parental source and light condition on seedling height, leaf length, and dry shoot mass (all P〈0.0001). A posteriori tests show that differences in seedling characteristics reflect differences in initial seed mass, with especially strong differences apparent in shoot mass. Regression of seedling characteristics on initial seed mass shows that variation of seed size within a crop is sufficient to influence shoot mass at 15 weeks (P〈0.0001). Effects of size differences of seeds that land adjacent to each other, either under the parent or in monkey droppings, are documented with growth of pairs of seedlings in pots. Differences in shoot height and mass at 15 weeks are evident when seeds of average size differ by only 0.2 g, and dramatic differences are evident when paired seeds differ by an average of 1.5 g. Seedlings grow more when isolated than when planted with conspecifics. These experimental results offer indirect support for the hypothesis that small-seeded Virola parents secure an advantage in reproduction through differential dispersal, while large-seeded plants produce more competitive seedlings under their own crowns — an advantage most likely to be of importance when frugivores are scarce.
    Type of Medium: Electronic Resource
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  • 13
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 180 (1997), S. 701-709 
    ISSN: 1432-1351
    Keywords: Key words Olfaction  ;  Odor discrimination  ; Mixture perception
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The cockroach is known to possess several morphologically distinct types of sensilla on its antenna, each of which contain a couple or a few receptor cells that respond to an array of compounds. We recorded the response of cells exclusively from one type of sensillum to evaluate the variation in the response of the cells in these sensilla to three closely related alcohols and their binary mixtures. Our results indicate that cells within the class of those responsive to aliphatic alcohols are otherwise variable in their response to particular aliphatic alcohols and not easily classifiable into subclasses. They also indicate that patterns of responses among cells are not robust with respect to concentration. Finally, a considerable level of inhibition is indicated in the response of the receptor cells to binary mixtures compared with the response to pure odorants. The data suggest that discrimination of alcohols (and other odorants of general but not special significance) by the cockroach cannot be understood simply in terms of labeled lines or linear filters.
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Springer
    Foundations of physics 29 (1999), S. 133-135 
    ISSN: 1572-9516
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 169 (1991), S. 215-230 
    ISSN: 1432-1351
    Keywords: Differential conditioning ; Proboscis extension reflex ; Learning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Here we present results obtained from 7 different series of experiments, all employing odor conditioning of proboscis extension in worker honeybees and each designed to address a particular question involving olfactory perception. The questions relate to: temporal complexity of odor cues; effects of concentration, suppression, and/or potentiation in mixture perception; acquisition and extinction rates, as well as levels of generalization associated with aliphatic compounds that have the same functional groups or same alkyl radical length; and the effects of continuous exposure to odorants in the first several days of adult life on various learning and discrimination tasks involving olfactory perception. From the data obtained in these experiments we were able to conclude the following: First, worker honeybees have a limited ability to perceive complex temporal odor-quality patterns in olfactory stimuli — they learn to associate the quality of only the last part of the stimulus with a sucrose reward. Second, we confirm that citral is qualitatively different in several perceptual contexts involving odor learning and conditioning and our results help elucidate the nature of these differences as they relate to learning, discrimination, mixture perception, and continuous exposure to particular odorants. Third, we appear to have uncovered some important perceptual differences between functional groups attached to the first as opposed to the second carbon atom of alkyl radicals. Finally, we failed to uncover any significant effects relating to continuous exposure to odorants during the first several days of a worker's adult life, despite evidence that considerable sensory development takes place during this period. Thus ontogenetic changes to the peripheral system due to environmental effects appear to leave basic perceptual systems unaltered.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    Springer
    Climatic change 37 (1997), S. 569-573 
    ISSN: 1573-1480
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Type of Medium: Electronic Resource
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  • 17
    ISSN: 1573-5028
    Keywords: cucumber ; light-regulated gene expression ; NADH-dependent hydroxypyruvate reductase ; organ-specific gene expression ; peroxisome ; photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 5′- and 3′-flanking regions of HPRA, a cucumber gene that encodes hydroxypyruvate reductase, were evaluated for regulatory activity with respect to light responsiveness and organ specificity. To define the functional regions of the 5′-flanking region of HPRA, a series of deletions was generated and the remaining portions fused to the β-glucuronidase (GUS) reporter gene (uidA) containing a minimal 35S promoter truncated at −90. The region from −66 to +39 was found to be necessary for light-regulated expression of the uidA reporter gene, while the region from −382 to −67 was found to be necessary for its leaf-specific expression. Further deletion of the HPRA 5′ flanking region to −590 resulted in high levels of root expression, suggesting the presence of a negative regulatory element responsible for silencing root expression of the HPRA gene between −590 and −383. The 3′-flanking region of the HPRA gene downstream of the polyadenylation site contains several sequence motifs resembling regulatory elements present in the promoters of several light-responsive genes. An 823 bp portion of the HPRA 3′-flanking region containing these putative regulatory elements enhanced GUS expression in leaves when placed downstream of the uidA reporter gene in the forward orientation, but not in the reverse orientation. When placed 5′ of the −90 35S promoter, the 823 bp fragment enhanced slightly, independently of orientation, the root tip-specific expression pattern intrinsic to the −90 35S promoter, indicating that in some cases this region can act as a transcriptional enhancer.
    Type of Medium: Electronic Resource
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  • 18
    Electronic Resource
    Electronic Resource
    Springer
    Plant molecular biology 17 (1991), S. 941-947 
    ISSN: 1573-5028
    Keywords: hydroxypyruvate reductase ; light regulation ; peroxisomal enzymes ; photorespiration ; plant gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several clones corresponding to the gene encoding NADH-dependent hydroxypyruvate reductase have been isolated from a cucumber genomic library. Restriction mapping indicates the presence of two HPR genes, hpr-A and hpr-B, in the cucumber genome. Examination of the DNAs of individual plants suggests that hpr-A and hpr-B are most likely alleles at a single locus. The sequence of a 6.7 kb genomic fragment that includes the entire transcribed region, 2.2 kb of 5′ flanking sequence, and about 0.8 kb of 3′ flanking sequence reveals the presence of 12 introns in hpr-A. These introns are AT-rich relative to the exons. The donor sequence at the 5′ end of the sixth intron contains an unusual dinucleotide, GC, rather than the nearly invariant GT. Primer extension analysis maps the transcription initiation site to 61 nucleotides upstream of the translation initiation codon. An AT-rich stretch is centered at position −31 with respect to the transcription initiation site, and a potential CCAAT box is centered at position −138. Several elements that are homologous to regulatory elements of other plant genes have been identified in the flanking regions of hpr-A.
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Springer
    Journal of mathematical biology 33 (1995), S. 521-556 
    ISSN: 1432-1416
    Keywords: Population dynamics modeling ; Evolutionarily stable strategies ; Polymorphic life histories ; Age-at-maturity ; Harvesting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract We study the evolution of polymorphic life histories in anadromous semelparous salmon and the effects of harvesting. We derive dynamic phenotypic and genetic ESS models for describing the evolutionary dynamics. We show in our deterministic analysis that polymorphisms are not possible in a panmictic random mating population. Instead, genetic or behavioral polymorphisms may be observed in populations with assortative mating systems. Positive assortative mating may be supported and generated by behavioral and phenotypic traits like male mate choice, spawning ground selection by phenotype, or within-river homing-migration-distance by size. In the case of an evolutionarily stable dimorphism, the ESS is characterized by a reproductive ideal free distribution such that at an equilibrium the individuals are indifferent from the fitness point of view between the two life histories of early and late reproduction. Different strategy models - that is, phenotypic and genetic ESS models - yield identical behavioral predictions and, consequently, genetics does not seem to play an important role in the present model. An evolutionary response to increased fishing mortality is obvious and may have resource management implications. High sea fishing mortalities drive the populations toward early spawning. Thus it is possible that unselective harvesting at sea may eliminate, depending on the biological system, behavioral polymorphisms or genetic heterozygozity and drive the population to a monomorphic one. If within-river homing migration distances depend on the size of fish, unselective harvesting at sea, or selective harvesting of spawning runs in rivers, may reduce local population sizes on spawning grounds high up rivers. Finally, harvesting in a population may cause a switch in a dominant life-history strategy in a population so that anticipated sustainable yields cannot be realized in practice.
    Type of Medium: Electronic Resource
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  • 20
    Electronic Resource
    Electronic Resource
    Springer
    Behavioral ecology and sociobiology 10 (1982), S. 265-270 
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Experimental hives obtained from cordovan queens that were instrumentally inseminated with semen from one cordovan and one Italian drone were set up and allowed to swarm. Cordovan provides a resessive genetic marker system (cuticle color) so that the workers from the cordovan and Italian male lines are distinguishable. Our results show that these patrilineal worker groups segregate non-randomly during colony fission and this segregation cannot be explained by observed age structure. Evidence of innate kin recognition in bees has been previously established. We argue that kin recognition could be responsible for the observed non-random grouping of kin during swarming.
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