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  • Articles  (62)
  • 2020-2022  (2)
  • 1995-1999  (40)
  • 1985-1989  (20)
  • Biology  (62)
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  • Articles  (62)
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  • 11
    Electronic Resource
    Electronic Resource
    Comparative physiology of burned and unburned Rhus laurina after chaparral wildfire (1986)
    Springer
    Oecologia 71 (1986), S. 63-68 
    Details
    ISSN: 1432-1939
    Keywords: Rhus ; Lignotuber ; Nitrogen ; Water relations ; Fire
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Laurel Sumac (Rhus laurina) is a dominant member of the coastal chaparral community of southern California that survives periodic burning by wildfires by resprouting from a lignotuber (root crown). We investigated the physiological basis for resprouting by comparing shoot elongation, leaf nitrogen content, tissue water status, leaf conductance to water vapor diffusion, and photosynthetic rates of post-fire R. laurina to those of adjacent unburned shrubs. Resprouts had higher rates of shoot elongation, leaf conductance, and photosynthesis than mature, unburned shrubs. Leaf nitrogen contents were elevated in burned shrubs even though their leaves developed interveinal chlorosis. A comparison of soil water potential to predawn water potential indicated that roots of R. laurina remain active below 2 m during the first summer drought after wildfire. Our results support the hypothesis that lignotubers not only contain dormant buds that develop into aerial shoots after wildfire but they also supply nutrient resources that enhance shoot elongation. Because R. laurina is relatively sensitive to drought, yet very successful in its rapid recovery after fire, maintaining an active root system after shoot removal may be the primary function of the massive lignotuber formed by this species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377322
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  • 12
    Electronic Resource
    Electronic Resource
    Water use patterns of four co-occurring chaparral shrubs (1986)
    Springer
    Oecologia 70 (1986), S. 172-177 
    Details
    ISSN: 1432-1939
    Keywords: Water use ; Root distribution ; Water potential predawn ; Leaf conductance ; Quercus durata ; Heteromeles arbutifolia ; Adenostoma fasciculatum ; Rhamnus californica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mixed stands of chaparral in California usually contain several species of shrubs growing close to each other so that aerial branches and subterranean roots overlap. There is some evidence that roots are stratified relative to depth. It may be that root stratification promotes sharing of soil moisture resources. We examined this possibility by comparing seasonal water use patterns in a mixed stand of chaparral dominated by four species of shrubs: Quercus durata, Heteromeles arbutifolia, Adenostoma fasciculatum, and Rhamnus californica. We used a neutron probe and soil phychrometers to follow seasonal depletion and recharging of soil moisture and compared these patterns to seasonal patterns of predawn water potentials, diurnal leaf conductances, and diurnal leaf water potentials. Our results indicated that 1) Quercus was deeply rooted, having high water potentials and high leaf conductances throughout the summer drought period, 2) Heteromeles/Adenostoma were intermediate in rooting depth, water potentials, and leaf conductances, and 3) Rhamnus was shallow rooted, having the lowest water potentials and leaf conductances. During the peak of the drought, predawn water potentials for Quercus corresponded to soil water potentials at or below a depth of 2 m, predawn water potentials of Heteromeles/ Adenostoma corresponded to a depth of 0.75 m, and predawn water potentials of Rhamnus corresponded to a depth of 0.5 m. This study supports the concept that co-occurring shrubs of chaparral in California utilize a different base of soil moisture resources.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379236
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  • 13
    Electronic Resource
    Electronic Resource
    Differential survival of chaparral seedlings during the first summer drought after wildfire (1988)
    Springer
    Oecologia 76 (1988), S. 215-221 
    Details
    ISSN: 1432-1939
    Keywords: Chaparral ; Seedling establishment ; Water stress ; Drought ; Fire
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Big Pod Ceanothus (Ceanothus megacarpus) is an obligate seeder after fire; Laurel Sumac (Rhus laurina) is primarily a resprouter after fire. Both species commonly occur together in mixed stands and are dominant members of the coastal chaparral of southern California. We compared the mean survival of post-fire seedlings of each species during the first summer drought after fire and found C. megacarpus to have a mean survival of 54% while R. laurina had a mean survival of only 0.1%. Rooting dephs were similar between species but predawn water potentials and leaf temperatures were higher for R. laurina seedlings. Leaf temperatures for R. laurina reached a mean value of 46.8° C on hot, summer days, about 5° C higher than seedlings of C. megacarpus. By the end of the first growing season, 92% of all C. megacarpus seedlings had suffered herbivory compared to only 17% of all R. laurina seedlings. Herbivory did not appear to be the immediate cause of seedling mortality. Transect data indicated that full recovery of prefire species composition and density at our study site was likely but the mode of recovery was different for the species examined. R. laurina recovered primarily by sprouting, C. megacarpus totally by seedling establishment and a third species, Adenostoma fasciculatum (chamise), by a combination of sprouting and seedling establishment. We attribute the higher mortality of R. laurina seedlings to the greater sensitivity of its tissue to water stress. It may be that differential survival of shrub seedlings and differential modes of reestablishment after fire play an important role in maintaining species diversity in the chaparral communities of coastal, southern California.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379955
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  • 14
    Electronic Resource
    Electronic Resource
    Characterisation of the low affinity interaction between rat cell adhesion molecules CD2 and CD48 by analytical ultracentrifugation (1997)
    Springer
    European biophysics journal 25 (1997), S. 455-462 
    Details
    ISSN: 1432-1017
    Keywords: Key words T-lymphocytes ; Dissociation constant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract CD2 is a cell adhesion molecule found on the plasma membrane of T-lymphocytes. Its counter-receptor in rat is the structurally related CD48. This interaction is believed to contribute to the adhesion of T-cells to other cells such as cytotoxic targets and antigen presenting cells. Cell-cell adhesion involves the formation of multiple cell adhesion molecule complexes at the cell surface and if cell-cell de-adhesion is to occur, these complexes need to be disrupted. The affinities of cell adhesion molecule interactions are suggested to be relatively weak to allow this de-adhesion of cell-cell interactions. The CD2/CD48 interaction has been studied using recombinant extracellular proteins and the affinity of the interaction of soluble recombinant rat CD2–CD48 has been determined (at 37°C) using surface plasmon resonance (and shown to be weak), with the dissociation constant Kd=60–90 µm. The values determined by surface plasmon resonance results could be affected by the immobilisation of the ligand on the chip and any self-association on the chip. We used three different analytical ultracentrifuge procedures which each allowed the interaction to be studied in free solution without the need for an immobilisation medium. Both sedimentation equilibrium (using direct analysis of the concentration distribution and also modelling of molecular weight versus concentration data) and sedimentation velocity at 5°C yielded dissociation constants in the range of 20– 110 µm, supporting the surface plasmon resonance findings showing that binding between these cell adhesion molecules is relatively weak. These studies also ruled out the presence of any significant self-association of the reactants which could lead to systematic error in the surface plasmon resonance results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002490050060
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  • 15
    Electronic Resource
    Electronic Resource
    Expression of the butyrophilin gene, a milk fat globule membrane protein, is associated with the expression of the αS1casein gene (1995)
    Springer
    Journal of molecular histology 27 (1995), S. 388-394 
    Details
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Previous in situ hybridization studies from our laboratory have shown that expression of certain milk protein genes, e.g. α-lactalbumin, is very high in most parts of the mammary glands of sheep and cattle, while in other areas containing an abundance of fat globules it is virtually zero (Molenaar et al., 1992). One possible explanation is that some areas of the mammary gland are dedicated to protein synthesis and some to fat synthesis. To check this possibility, the cRNA for butyrophilin, a milk-fat globule membrane protein, and hence a putative marker of milk fat synthesis, was used as a probe in in situ hybridization studies. The results show quite clearly that the patterns of expression for this gene are similar, cell type for cell type, as those for milk protein genes such as α-lactalbumin and αs1casein. In addition, we found that butyrophilin gene expression more closely matches that of αS1casein than that of α-lactalbumin. If it is shown in the future that butyrophilin is indeed a marker for milk fat synthesis, then these results support the current assumption that fat and protein synthesis do occur in the same cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00179564
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  • 16
    Electronic Resource
    Electronic Resource
    Expression of the butyrophilin gene, a milk fat globule membrane protein, is associated with the expression of the αS1casein gene (1995)
    Springer
    Journal of molecular histology 27 (1995), S. 388-394 
    Details
    ISSN: 1573-6865
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Previousin situ hybridization studies from our laboratory have shown that expression of certain milk protein genes, e.g. α-lactalbumin, is very high in most parts of the mammary glands of sheep and cattle, while in other areas containing an abundance of fat globules it is virtually zero (Molenaaret al., 1992). One possible explanation is that some areas of the mammary gland are dedicated to protein synthesis and some to fat synthesis. To check this possibility, the cRNA for butyrophilin, a milk-fat globule membrane protein, and hence a putative marker of milk fat synthesis, was used as a probe inin situ hybridization studies. The results show quite clearly that the patterns of expression for this gene are similar, cell type for cell type, as those for milk protein genes such as α-lactalbumin and αs1casein. In addition, we found that butyrophilin gene expression more closely matches that of αS1casein than that of α-lactalbumin. If it is shown in the future that butyrophilin is indeed a marker for milk fat synthesis, then these results support the current assumption that fat and protein synthesis do occur in the same cell.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02389025
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  • 17
    Electronic Resource
    Electronic Resource
    A Karyotypic Analysis of Nilgai, Boselaphus Tragocamelus (Artiodactyla: Bovidae) (1998)
    Springer
    Chromosome research 6 (1998), S. 505-514 
    Details
    ISSN: 1573-6849
    Keywords: Artiodactyla ; Bovidae ; comparative cyto-genetics ; karyotype ; molecular cytogenetics ; nilgai
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A combination of chromosomal banding and fluorescence in situ hybridization (FISH) was used to characterize the karyotype of Boselaphus tragocamelus (nilgai) relative to the domestic cattle standard karyotype. G-, Q- and C-band karyotypes of nilgai are presented, and the chromosomal complement of nilgai is determined to be 2n = 46 (female FN = 60, male FN = 59; NAA = 56), consistent with previous reports for the species. Comparisons with cattle identified extensive monobrachial homologies with some noteworthy exceptions. Chromosome 25 is centrically fused to 24, and chromosome 16 is acrocentric. Both appear to have additional pericentromeric material not seen in the equivalent cattle acrocentrics. This pericentromeric chromatin may be the result of de novo additions or translocation of pericentromeric material from chromosome 6, which is shown to be centrically fused to 13 but is only about two-thirds the length of cattle 6. Comparisons with cattle demonstrated that nilgai chromosome 17 has undergone a paracentric inversion and that chromosome 20 has two blocks of interstitial constitutive heterochromatin. The identities of both chromosomes were confirmed by chromosomal FISH. Furthermore, chromosomal banding and FISH were used to determine that autosome 14 has been fused to the ancestral X and Y of nilgai to form compound neo-X and -Y chromosomes. Additional FISH analyses were conducted to confirm other proposed chromosome homologies and to identify nucleolar organizing regions within the nilgai complement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009268917856
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  • 18
    Electronic Resource
    Electronic Resource
    Dolphin interleukin-8 receptor Map position 18q25–26 (1998)
    Springer
    Chromosome research 6 (1998), S. 661-661 
    Details
    ISSN: 1573-6849
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009278131934
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  • 19
    Electronic Resource
    Electronic Resource
    Functional interpretation of archaeobotanical data: Making hay in the archaeological record (1999)
    Springer
    Vegetation history and archaeobotany 8 (1999), S. 261-271 
    Details
    ISSN: 1617-6278
    Keywords: Hay ; Meadow ; Pasture ; Archaeobotany ; Europe ; Farming history
    Source: Springer Online Journal Archives 1860-2000
    Topics: Archaeology , Biology
    Notes: Abstract Hay malting and hay meadows have long been of fundamental ecological, economic and social importance in temperate Europe. A variety of archaeological sources suggests that hay making may date back to the Iron Age, but direct archaeobotanical evidence for this practice is problematic. Past grassland communities are imperfectly represented and preserved in archaeobotanical assemblages, and ancient meadow and pasture communities may not resemble present-day communities in terms of management practices or botanical composition. This paper explores the potential of ‘FIBS’ (Functional Interpretation of Botanical Surveys) in the archaeobotanical investigation of ancient grassland management. The botanical composition of present-day grassland communities was analysed in terms of functional attributes (e.g. canopy height) relevant to cutting, grazing and habitat productivity. The utility of these attributes for distinguishing between present-day meadow, pasture and unmanaged grassland communities has been evaluated. Similar analyses were performed on archaeobotanical data from Neolithic to post-Medieval northwestern and central Europe. Functional shifts over time, interpreted in the light of the functional analysis of modern grassland, suggest that hay-making was well established by the Iron Age. Avenues are suggested for the refinement and further development of the FIBS methodology in the archaeobotanical investigation of grassland management.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01291778
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  • 20
    Electronic Resource
    Electronic Resource
    Isolation of developmental mutants of the ascidian Ciona savignyi (1999)
    Springer
    Molecular genetics and genomics 262 (1999), S. 199-206 
    Details
    ISSN: 1617-4623
    Keywords: Key words Ascidian ; Mutagenesis ; Development ; Ethylnitrosourea (ENU)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ascidians have been used extensively as model animals for experimental embryology. We report here the results of a pilot study with the aim of developing genetic methods for the ascidian Ciona savignyi. The chemical mutagen N-ethyl-N-nitrosourea (ENU) was used to induce point mutations. F1 animals, produced by using sperm from ENU-treated animals to fertilize untreated eggs, were grown to reproductive age. Sperm and eggs collected from the hermaphrodite F1 adults were used to generate self-fertilized F2 broods, which were then screened for recessive, zygotically acting mutations. Animals carrying potential mutations were outcrossed to wild type to test for the heritability of the phenotypes. We report on a number of mutants isolated using this method, including several with abnormalities in tail and notochord development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380051075
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