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71.
Park S. Nobel 《Oecologia》1984,64(1):1-7
Summary An environmental productivity index based on physiological responses to three environmental variables was used to predict the net productivity of a common succulent perennial of the Sonoran Desert, Agave deserti, on a monthly basis. Productivity was also independently measured in the field from dry weight changes. The index was based on soil water availability, day/night air temperatures, and photosynthetically active radiation (PAR), which were individually varied in the laboratory and the effect on net CO2 uptake by the leaves determined. From monthly precipitation, temperature, and PAR at the field site together with the responses measured in the laboratory, an index (maximum value of unity) was assigned to each of these three environmental variables and their product was termed the environmental productivity index. This index indicates the fraction of maximal CO2 uptake expected in the field for each month (well-watered A. deserti assimilated 285 mmol CO2 m-2 leaf area day-1 at PAR saturation and optimal day/night temperatures of 25° C/15° C). The dry weight analysis was based on the monthly unfolding of new leaves from the central spike of the rosette and their seasonal increase in dry weight, which were determined in the field. The production of new leaves was highly correlated with the environmental productivity index (r2=0.93), which in turn was highly correlated with the water status index (r2=0.97). After correction for respiration by folded leaves, stem, and roots, plant productivity predicted by the average environmental productivity index (0.36) over a wet June-to-October period agreed within 4% with the productivity based on the conventional dry weight analysis. The net productivity of A. deserti over this 5-month period was 0.57 kg m-2 ground area (5.7 Mg ha-1), a large value for a desert CAM plant. The environmental productivity index proposed here may provide a reliable means for predicting net productivity on a monthly basis, which may be particularly useful for species in relatively variable environments such as deserts. 相似文献
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73.
The material properties of bone-particle impregnated PMMA 总被引:4,自引:0,他引:4
The elastic Young's modulus and shear modulus of bone-particle impregnated polymethylmethacrylate (PMMA) has been measured experimentally at room temperature as a function of bone particle concentration. It was found that the moduli increased with increasing bone particle content. This increase was less than the stiffness increase predicted by higher-order composite theory [1, 2] under the assumption of perfect bonding between particles and matrix. It was concluded that a bond existed but that it was not a perfect bond. 相似文献
74.
Monoclonal antibody-directed immunopurification and identification of cytochromes P-450 总被引:4,自引:0,他引:4
F K Friedman R C Robinson S S Park H V Gelboin 《Biochemical and biophysical research communications》1983,116(3):859-865
A 28 amino acid peptide with diuretic and natriuretic activity has been purified from rat atrial muscle. The primary structure of this atrial peptide is H-Ser-Leu-Arg-Arg-Ser-Ser-Cys-Phe-Gly-Gly-Arg-Ile-Asp-Arg-Ile-Gly- (sequence in text) Ala-Gln-Ser-Gly-Leu-Gly-Cys-Asn-Ser-Phe-(Arg)-Tyr-OH. The biological activity of this peptide is identical to that of atrial natriuretic factor and cardionatrin I isolated from rat atria. 相似文献
75.
The metabolism of [6,7-3H]ethinylestradiol [( 3H]EE2) by rat liver microsomes was studied in vitro. After incubation of [3H]EE2 with rat liver microsomes for 20 min, 90% of the substrate was metabolised and 18% of the 3H-labelled material irreversibly bound to microsomal protein. Ascorbic acid (1 mM) decreased irreversible binding of 3H and produced an accumulation of 2-hydroxyethinylestradiol (2OH-EE2), while mixed-function oxidase inhibitors (0.5 mM) decreased binding of 3H to protein by inhibiting EE2 2-hydroxylation. Addition of thiols gave water-soluble metabolites which were characterised as 1(4)-thioether derivatives of 2OH-EE2 by co-chromatography with synthetic products. The results are consistent with the hypothesis that the chemically reactive metabolite of EE2 formed in vitro is either a quinone or o-semiquinone derived from 2OH-EE2 [1]. 相似文献
76.
Antigens on human plasma cells identified by monoclonal antibodies 总被引:13,自引:0,他引:13
K C Anderson E K Park M P Bates R C Leonard R Hardy S F Schlossman L M Nadler 《Journal of immunology (Baltimore, Md. : 1950)》1983,130(3):1132-1138
Two monoclonal antibodies that define distinct plasma cell-associated antigens, termed PCA-1 and PCA-2, were developed against human plasma cell leukemia cells. These antigens are strongly expressed on human myelomas, plasma cell leukemia, and plasmacytoma tumor cells, but are not detected on other lymphoid malignancies of B, T, null, or myeloid origin. PCA-1 and PCA-2 are not expressed on either normal T or B lymphocytes, but are weakly expressed on granulocytes and monocytes. When pokeweed mitogen is used to induce human B lymphocyte differentiation, PCA-1 is expressed when other B cell determinants are lost and plasmacytoid morphology, intracytoplasmic immunoglobulins, and surface T10 staining characteristic of plasma cells appear. In contrast, PCA-2 cannot be induced and may therefore appear later in the B cell differentiation scheme. These antigens may be of utility for the study and regulation of normal and abnormal plasma cell growth, traffic, and tissue distribution and may aid in understanding heterogeneity within plasma cell dyscrasias. 相似文献
77.
Production of mature sporophores ofAgaricus bisporus was achieved for the first time in amended, autoclaved soil, gamma-sterilized soil, and soil-extract agar medium. The initiation of sporophores was triggered by metabolites of soil-inhabiting bacteria, particularly nodule forming isolates. Whether a single metabolite or several metabolites of these bacteria caused formation of sporophores could not be established; however, biotin alone when added to soil extract medium produced comparable results. The potentiality of different bacteria to induce sporophore formation varied considerably within species and isolates.Amino acids favored vegetative growth ofA. bisporus, but failed to induce formation of sporophores. Organic acids supported luxuriant growth and poor sporophore formation. Among several growth-promoting substances and vitamins, biotin induced abundant formation of mature sporophores.The authors are thankful to Dr. C. Corke, Department of Soil Microbiology, University of Guelph, Ontario, for providing some bacterial cultures used in this study. 相似文献
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