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  • 1
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The persistence of flock membership through time and space was examined for wintering sanderlings Calidris alba at Bodega Bay, California from October 1978 to March 1981. Observed patterns of association were then compared with those expected from a null model: that the set of birds within a given flock represent a random sample from the local population. Individual membership in flocks fluctuated rapidly through time and space as flocks moved along the beach. Flock composition differed from random in 6 of 10 observations periods, but the magnitude of difference was very small compared with results from other species. Sanderling flocks represent an extreme example of open groups in vertebrate social organization.
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  • 2
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. Evolutionary interpretations of breeding social systems normally focus on ecological factors operating within the breeding season. Yet for most temperate zone and arctic species, this season occupies only a small period within the annual cycle. The migration distances and breeding and wintering distributions of the calidridine sandpipers (Scolopacidae, Calidridinae) were analyzed in relation to their patterns of parental care and mating to test for the importance of cross-seasonal interactions in the evolution of breeding social systems. These species breed in the arctic and migrate to wintering grounds throughout the northern and southern temperate zones and tropics. 2. Two gradients can be identified in sandpiper breeding systems. First, with respect to parental care, they can be ranked from those with biparental care in which both adults remain with the young until fledging to cases of single-parent care where one adult plays no parental role beyond fertilization. Second, in mating systems, they range from strictly monogamous species to promiscuous, i.e., a gradient with increasing probability of reproduction with more than one member of the opposite sex during a given season. 3. These gradients in parental care and mating systems correlate with migration distance. Species in which one adult departs early and species deviating from monogamy are more likely to migrate farther. More promiscuous species also tend to breed farther north. Migration distance and wintering distribution are so tightly correlated that they cannot be separated. 4. These patterns are consistent with a hypothesis that through early departure an individual can decrease the risks of long-distance migration. Thus cross-seasonal effects may interact with intraseasonal parameters such as food and predation to determine the form of calidridine breeding social systems.
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  • 3
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-5060
    Keywords: Pisum sativum ; pea ; genetic male sterility ; genetics ; allelism ; linkage ; meiotic mutants ; microsporogenesis ; outcrossing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Relatively few male sterile (ms) genes have been reported in the pea despite description of numerous qualitative genes for other traits. This study was undertaken to characterize genetic male sterility in the pea. Male sterility may facilitate outcrossing because the pea is cleistogamous. Of fourteen lines carrying male sterility, tests of allelism revealed nine unique ms genes. According to F2 and F3 data, all ms genes segregated as single recessive genes. Linkage relations were determined for all but two. The genes appeared to be distributed randomly across the chromosomes. Two ms genes (ms-3 and ms-10) exhibited reduced female fertility in addition to male sterility. These mutants may have utility in increasing genetic recombination, particularly where hand hybridization is used.
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  • 5
    ISSN: 1573-5044
    Keywords: somatic embryogenesis ; tissue culture ; histology ; Trifolium ; zygotic embryogenesis ; regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The origin and development of zygotic and somatic embryos of Trifolium rubens L. was studied with the aid of paraffin sections and light microscopy. Zygotic embryos were collected, fixed and prepared daily from one to ten days after cross-pollination. Somatic embryos were obtained by plating petiole sections on modified L2 medium with 0.015 mgl-1 picloram and 0.1 mgl-1 6-BAP. Cultured petioles were collected and fixed daily from one to 25 days after plating. Two regions in the vascular bundle sheath of cultured petioles gave rise to callus. The first region was adjacent to the phloem fibers and produced friable callus. The second region gave rise to compact callus that was connected to the fascicular cambium. Somatic embryos originated from single cells in the cortex directly without intervening callus formation and from single cells in the friable callus. In addition, embryos arose from meristematic regions in compact callus. Many early stages of embryogenesis (one, two and four-celled stages) were observed in the cortex and friable callus. Zygotic embryogenesis in Trifolium differs from other legumes in that the suspensor is short and has a broad attachment. This arrangement was observed in zygotic embryos of T. rubens and in many somatic embryos. However, a continuum of somatic embryogenesis was observed where some young embryos had a Trifolium suspensor-like arrangement while others were attached to a long narrow suspensor-like structure more characteristic of Medicago.
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  • 6
    ISSN: 1573-5044
    Keywords: somatic embryogenesis ; plant regeneration ; protoplasts ; Trifolium pratense ; red clover ; protoclonal variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Protoplasts are useful for subcellular studies, in vitro selection, somatic hybridization and transformation. Whole plant regeneration from protoplasts is a prerequisite to producing altered crop plants using these methods. Whole plant regeneration was achieved from leaf- and suspension culture-derived protoplasts of T. pratense. Regeneration was most dependent upon identifying genotypes with genetic capacity to regenerate. Additional factors that were used to select genotypes, but which proved to be less important, were a high rate of cell growth in culture and a high plating efficiency of protoplasts. One genotype was identified which had a regeneration response equivalent to that of T. rubens and which regenerated from both leaf- and suspension culture-derived protoplasts.
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  • 7
    ISSN: 1573-0646
    Keywords: bisantrene ; hypersensitivity ; histamine release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Nine of ninety-three patients receiving Bisantrene on an every three week schedule developed an anaphylactoid reaction with a variety of symptoms. Most reactions occurred in patients who had multiple exposures to Bisantrene. Investigatiors utilizing Bisantrene in ongoing clinical trials should be aware of this life threatening toxicity.
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  • 8
    ISSN: 1573-0646
    Keywords: bisantrene ; CL216,942 ; pharmacokinetics in humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of bisantrene, 9,10-anthracenedicarboxaldehyde bis ((4,5-dihydro-1 H-imidazol-2-yl) hydrazone) dihydrochloride were evaluated during a Phase I clinical investigation. Bisantrene at doses of 20 to 280 mg/m2 was administered by variable infusion rates to nine patients with advanced metastatic cancer. Bisantrene's plasma clearance followed a triexponential pattern with a harmonic mean terminal half-life (t1/2 γ) of 26 h. The steady state volume of distribution (Vd ss ) was large, averaging 627 l/m2. Plasma clearance averaged 42.6±6.7 l/h/m2. The cumulative urinary excretion of bisantrene was 3.6±1.6% at 48 h.
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  • 9
    ISSN: 1437-5613
    Keywords: Key words Population cycles ; Nucleopolyhedrovirus ; NPV ; Insect quality ; Metapopulation ; Island populations ; Forest tent caterpillars ; Sublethal disease
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cyclic populations of western tent caterpillars fluctuate with a periodicity of 6–11 years in southwestern British Columbia, Canada. Typically, larval survival is high in early stages of the population increase, begins to decline midway through the increase phase, and is low through several generations of the population decline. Fecundity is generally high in increasing and in peak populations but is also reduced during the population decline. Poor survival and low fecundity for several generations cause the lag in recovery of populations that is necessary for cyclic dynamics. The dynamics of tent caterpillar populations vary among sites, which suggests a metapopulation structure; island populations in the rainshadow of Vancouver Island have more consistent cyclic dynamics than mainland populations in British Columbia. Sudden outbreaks of populations that last a single year suggest that dispersal from source to sink populations may occur late in the phase of population increase. Wellington earlier discussed qualitative variation among tent caterpillar individuals as an aspect of population fluctuations. The variation in caterpillar activity he observed was largely statistically nonsignificant. Recent observations show that the frequency of elongate tents as described by Wellington to characterize active caterpillars varies among populations but does not change in a consistent pattern with population density. The level of infection from nucleopolyhedrovirus (NPV) was high in some populations at peak density but was not associated with all population declines. Sublethal infection can reduce the fecundity of surviving moths, and there is a weak association between viral infection and egg mass size in field populations. The impact of weather in synchronizing or desynchronizing populations is a factor to be investigated further.
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  • 10
    ISSN: 1432-2242
    Keywords: Wide hybridization ; Tissue culture ; Ovary culture ; Tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In vitro pollination of placenta attached ovules was useful in bypassing unilateral incongruity barriers for several Nicotiana interspecific hybrid combinations (N. tabacum cv. ‘Ky 17’ X N. amplexicaulis, ‘Ky 17’ X N. benthamiana, and ‘Ky 17’ X N. repanda). By measuring the pollen tube growth over time, prefertilization barriers were determined to be the cause of the incongruity. Seedling necrosis was a problem in the development of the N. amplexicaulis hybrid and it prevented maturation of the N. repanda hybrid. Callus produced from cotyledons of the N. amplexicaulis hybrid eventually resulted in plants that survived to maturity. This procedure was not successful for the N. repanda materials. The N. amplexicaulis and N. benthamiana hybrids were sterile but following chromosome doubling by midrib culture, male and female fertile plants were produced. Conventional hybridization, fertilized ovule culture, and in vitro pollination were unsuccessful in obtaining hybrids of ‘Ky 17’ crossed with N. arentsii or N. bonariensis. Apparently, strong postfertilization barriers prevent the production of viable seed of these hybrids. Each of the N. repanda — N. tabacum reciprocal hybrids could not be rescued using callus culture; this adds support to the existence of strong sexual postfertilization barriers. A recent report, however, showed that it was possible to obtain this hybrid using the technique of somatic hybridization. Thus, it appears that it may also be possible to obtain asexual hybrids of N. arentsii and N. bonariensis with N. tabacum.
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