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  • Life and Medical Sciences  (5)
  • Chaparral  (3)
  • 2005-2009
  • 1990-1994
  • 1985-1989  (8)
  • 1989  (4)
  • 1986  (4)
  • 1946
  • 1
    Electronic Resource
    Electronic Resource
    Recovery patterns of three chaparral shrub species after wildfire (1989)
    Springer
    Oecologia 80 (1989), S. 309-320 
    Details
    ISSN: 1432-1939
    Keywords: Chaparral ; Seedling survival ; Root depth ; Rhus ; Ceanothus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In a mature, even aged stand of mixed chaparral, Rhus laurina (facultative resprouter) had consistently higher water potentials and deeper roots than Ceanothus spinosus (facultative resprouter) and Ceanothus megacarpus (obligate seeder). For two years following a wildfire, the same stand of chaparral had resprouts with higher survivorships, predawn water potentials, stomatal conductances, photosynthetic rates and shoot elongation rates than seedlings. Supplemental irrigation of seedlings during summer months removed differences between resprouts and seedlings suggesting that the cause of such differences was limited water availability to the shoot tissues of seedlings. After two years of postfire regrowth, mean seedling survivorship for the obligate seeder (C. megacarpus) was 42%, whereas seedling survivorship for facultative resprouters was only 18% (C. spinosus) and 0.01% (R. laurina). Our results are consistent with the hypothesis that lack of resprouting ability among obligate seeders is offset by an enhanced ability to establish seedlings after wildfire, allowing obligate seeders to maintain themselves in mixed populations through many fire cycles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379032
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  • 2
    Electronic Resource
    Electronic Resource
    Tissue water relations of three chaparral shrub species after wildfire (1989)
    Springer
    Oecologia 80 (1989), S. 303-308 
    Details
    ISSN: 1432-1939
    Keywords: Chaparral ; Osmotic potential ; Turgor ; Pressure-volume curve ; Dew-point hygrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We compared the tissue water relations among resprouts and seedlings of three chaparral species during the first summer drought after wildfire. Two of the species, Rhus laurina and Ceanothus spinosus recover after fire by a combination of resprouting and seedling establishment (facultative resprouters), whereas a third species, Ceanothus megacarpus recovers by seedling establishment alone (obligate seeder). Our objectives were to document any differences in tissue water characteristics that might arise between resprouts and seedlings and to test the hypothesis that seedlings of obligate seeders develop more drought tolerant characteristics of their tissues than seedlings of facultative resprouters. We found that resprouts had much higher predawn values of water potential, osmotic potential, and turgor potentials than seedlings. Predawn turgor potentials of resprouts were 1.5 MPa through July and August when turgor potentials for seedlings remained near 0 MPa. During summer months, midday water potentials were 2 to 3 MPa higher for resprouts than seedlings and midday conductances of resprouts were two to five fold greater than those of seedlings. Even though resprouts did not experience severe water stress like seedlings, their tissue water characteristics, as determined by pressure-volume curve analyses, were similar by the peak of the drought in August. Further-more, the tissue water characteristics of seedlings from the obligate seeder, C. megacarpus, were similar to those of facultative resprouters — R. laurina, and C. spinosus. We attribute the observed differences in plant water status between resprouts and seedlings to differences in rooting depths and access to soil moisture reserves during summer drought. We conclude that the higher growth rates, photosynthetic performance, and survivorship of postfire resprouts are primarily a result of higher water availability to resprouting tissues during summer months. It appears that the greater seedling survivorship during summer drought observed for the obligate seeder, C. megacarpus, is not associated with more favorable tissue water characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379031
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  • 3
    Electronic Resource
    Electronic Resource
    Tissue water relations of four co-occurring chaparral shrubs (1986)
    Springer
    Oecologia 70 (1986), S. 527-535 
    Details
    ISSN: 1432-1939
    Keywords: Chaparral ; Osmotic potential ; Turgor ; Pressure-volume curve ; Dew-point hygrometry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Chaparral shrubs of California have a suite of morphological and physiological adaptations to withstand the prolonged summer droughts of a mediterranean climate. Not all species of chaparral have the same rooting depth and there is some evidence that those with shallow roots have tissue that is most tolerant to water stress. We tested this notion by comparing the tissue water relations of four co-occurring chaparral shrubs: Quercus durata, Heteromeles arbutifolia, Adenostoma fasciculatum, and Rhamnus californica. We used a pressure-volume technique and a dew-point hygrometer to metsure seasonal changes in osmotic potential when plant tissue was fully hydrated and osmotic potential at predawn, midday, and the turgor loss point. We also calculated seasonal changes in the minimum daily turgor potential, saturated weight/dry weight ratio of leaf tissue, and the bulk modulus of elasticity. We had information on the seasonal water use patterns and apparent rooting depths of these same four shrubs from a previous study (Davis and Mooney 1986). All evidence indicated that Rhamnus had shallow roots and Quercus deep roots. Our results indicated that the tissue water relations of our four co-occurring chaparral shrubs were not alike. Even though Rhamnus had shallow roots, it had the least xerophytic tissue. Seasonal osmotic potential and saturated weight/dry weight ratios were relatively high and bulk modulus of elasticity and minimum daily turgor potentials were low. Furthermore, even though Quercus had deep roots and experienced no seasonal water stress at our study site, its tissue water relations indicated relatively high tolerance to water stress. We conclude that seasonal drought tolerance of stem and leaf tissue of co-occurring chaparral shrubs does not necessarily correspond to rooting depth, to soil moisture resources available to the shrub, or to the degree of seasonal water stress experienced by the shrub.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379899
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  • 4
    Electronic Resource
    Electronic Resource
    Distribution of phosphorylated spindle-associated proteins in the diatom Stephanopyxis turris (1989)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 12 (1989), S. 33-41 
    Details
    ISSN: 0886-1544
    Keywords: phosphorylation ; MPM-2 ; mitotic spindle ; microtubule-associated protein ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Mitotic spindles isolated from the diatom Stephanopyxis turris become thiophosphorylated in the presence of ATPγS at specific locations within the mitotic apparatus, resulting in a stimulation of ATP-dependent spindle elongation in vitro. Here, using indirect immunofluorescence, we compare the staining pattern of an antibody against thiophosphorylated proteins to that of MPM-2, an antibody against mitosis-specific phosphoproteins, in isolated spindles. Both antibodies label spindle poles, kinetochores, and the midzone. Neither antibody exhibits reduced labeling in salt-extracted spindles, although prior salt extraction inhibits thiophosphorylation in ATPγS. Furthermore, both antibodies recognize a 205 kd band on immunoblots of spindle extracts. Microtubule-organizing centers and mitotic spindles label brightly with the MPM-2 antibody in intact cells. These results show that functional mitotic spindles isolated from S. turris are phosphorylated both in vivo and in vitro. We discuss the possible role of phosphorylated cytoskeletal proteins in the control of mitotic spindle function.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970120105
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  • 5
    Electronic Resource
    Electronic Resource
    Liver autophagy in the influenza B virus model of Reye's syndrome in mice (1986)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 31 (1986), S. 271-275 
    Details
    ISSN: 0730-2312
    Keywords: Reye's syndrome ; liver autophagy ; influenza B virus ; ornithine carbamoyl transferase ; glucose-6-phosphatase ; tritosomes ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Biochemical evidence is presented for the autophagic destruction of liver mitochondria in the influenza B virus model of Reye's syndrome in mice. Separation of lysosomes and autophagic vacuoles from mitochondria was accomplished by prior treatment of the mice with Triton WR-1339, resulting in uptake of detergent by these organelles (tritosomes), reducing their densities. The organelles were banded in a discontinuous sucrose gradient. Total protein in the heavy tritosomal fraction increased from 1-2% in controls to 7-8% in virus-treated animals. Ornithine carbamoyl transferase (OCTase), a mitochondrial marker, increased from 2-3% (controls) to 11-15% (virus-treated), and glucose-6-phosphatase, a marker for endoplasmic reticulum, increased from 1-2% (controls) to 8-10% (virus-treated). β-Galactosidase, a soluble enzyme in the lysosome, and OCTase also increase in the cell extract fraction following virus treatment, indicating that there was turnover of heavy lysosomal contents.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240310404
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  • 6
    Electronic Resource
    Electronic Resource
    The amdS gene of Aspergillus nidulans: Control by multiple regulatory signals (1986)
    New York, NY : Wiley-Blackwell
    BioEssays 5 (1986), S. 123-128 
    Details
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The amdS gene of A. nidulans has proved extremely favourable for the isolation of mutations affecting gene regulation. Trans-acting regulatory genes involved in amdS induction by small molecular weight effectors have been identified - amdR (ω-amino acids) facB (acetate) and amdA (acetate). Another gene, the areA gene, has properties expected of a major activator gene involved in nitrogen metabolite repression of amdS. All of these regulatory genes are also involved in the control of various other functions encoded by structural genes unlinked to amdS. Mutations in the 5′-region adjacent to amdS have been isolated and allow the identification of independent cis-acting sequences which are the target sites for the regulatory genes. The involvement of these sequences in regulatory product binding has been deduced from titration studies using transformants containing multiple copies of the 5′ sequences. A combination of genetics and molecular analysis is allowing a detailed characterization of this system.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bies.950050308
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  • 7
    Electronic Resource
    Electronic Resource
    Structural comparison of the Pichia pastoris alcohol oxidase genes (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Yeast 5 (1989), S. 167-177 
    Details
    ISSN: 0749-503X
    Keywords: Methylotrophic yeasts ; alcohol oxidase ; Pichia pastoris ; genome evolution ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In methylotrophic yeasts, alcohol oxidase is the first enzyme in the methanol-utilization pathway. The genome of one such yeast, Pichia pastoris, contains two alcohol oxidase genes, AOX1 and AOX2. Sequence analysis indicated that each gene encodes a similar protein of 663 amino acids. The protein-coding regions of the genes were 92% and 97% homologous at the nucleotide and predicted amino acid sequence levels, respectively. In contrast to homology observed within the protein-coding portions of the AOX genes, no homology was found in either the 5′ or 3′ non-coding regions. Although alcohol oxidase is found in peroxisomes of P. pastoris, the AOX amino acid sequences did not contain a peptide sequence similar to the peroxisomal transport sequence found at the C-terminus of some peroxisomally located proteins in higher eukaryotes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/yea.320050306
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  • 8
    Electronic Resource
    Electronic Resource
    Toward an understanding of liposome structure through the use of computer graphic image correlation (1986)
    New York, NY : Wiley-Blackwell
    Journal of Electron Microscopy Technique 3 (1986), S. 385-400 
    Details
    ISSN: 0741-0581
    Keywords: Freeze fractures ; Vesicles ; Liquid crystal ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Notes: A computer-aided graphics approach to correlating transmission electron microscope images of freeze-fractured and thin-sectioned samples is outlined. Any three-dimensional model of the imaged structure can be mathematically sectioned to provide a two-dimensional representation of the model in the “fracture” plane. The method is used to demonstrate that the structure of lamellar liquid crystalline liposomes is based on a family of Dupin cyclides; closed, parallel surfaces with a conjugate ellipse and hyperbola as curvature defects.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jemt.1060030403
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