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  • Dew-point hygrometry  (2)
  • gastrointestinal transit  (2)
  • Springer  (4)
  • 1985-1989  (4)
  • 1955-1959
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  • Springer  (4)
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Year
  • 1
    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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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    The effect of density on the gastric emptying of single- and multiple-unit dosage forms (1986)
    Springer
    Pharmaceutical research 3 (1986), S. 208-213 
    Details
    ISSN: 1573-904X
    Keywords: gastrointestinal transit ; pellet density ; floating formulations, gastric emptying
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The gastric emptying of pellets and single units of different densities has been followed in healthy subjects using the technique of gamma scintigraphy. The gastric emptying of the light pellets was affected by their buoyancy in the upper part of the stomach. However, the mean gastric emptying rates of pellets and single units were not significantly affected by density. Floating or buoyant delivery systems may have little advantage over conventional systems. The presence of food in the stomach was found to be the major factor in determining the gastric emptying of single units.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016334629169
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  • 4
    Electronic Resource
    Electronic Resource
    Correlation of Phenylpropanolamine Bioavailability with Gastrointestinal Transit by Scintigraphic Monitoring of 111In-Labeled Hydroxypropylmethylcellulose Matrices (1989)
    Springer
    Pharmaceutical research 6 (1989), S. 274-278 
    Details
    ISSN: 1573-904X
    Keywords: bioavailability ; scintigraphy ; gastrointestinal transit ; controlled release ; phenylpropanolamine ; hydroxypropylmethylcellulose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Two controlled-release hydroxypropylmethylcellulose (HPMC) matrix formulations, a single-unit and a multiple-unit system, have been evaluated in human volunteers. Both formulations contained the sympathomimetic drug phenylpropanolamine hydrochloride and each was radiolabeled with 111Inbound Amberlite IR 120 ion-exchange resin. The formulations were administered to each of six healthy male volunteers and gastrointestinal (GI) transit was monitored using a gamma camera. Serum samples were taken at set time intervals and assayed for phenylpropanolamine content, thus allowing blood drug levels to be correlated with the position of the dosage form in the GI tract. The multiple-unit system emptied from the stomach gradually over a period of about 180 min, when administered after a light breakfast, whereas the single-unit dosage forms had extremely variable gastric emptying times (range, 60 to 〉570 min). However, both formulations provided prolonged phenylpropanolamine blood levels. The differences in the blood profiles obtained with the two formulations were attributed to variations in their in vitro release rates and not to any differences in their GI transit times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1015986121822
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