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  • 1995-1999  (4)
  • Photosynthesis  (2)
  • premenopausal bilateral breast neoplasms  (2)
  • 1
    ISSN: 1432-2285
    Keywords: Nitrogen ; Photosynthesis ; Picea sitchensis ; Thuja plicata ; Tsuga heterophylla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of differing, exponentially increasing rates of N addition (0.025, 0.05, 0.07 and 0.09 gN gN-1day-1) on photosynthesis, discrimination against13C and partitioning of foliar N to chlorophyll and major photosynthetic proteins were compared in seedlings of the evergreen conifersPicea sitchensis, Thuja plicata andTsuga heterophylla. T. heterophylla had the lowest range of foliar N concentrations (Nlm). Across species, photosynthetic rates (A) increased linearly with Nlm to a maximum at 21 mg g-1 and declined at higher Nlms. Species differences inA resulted from differences in Nlm, not from differences in photosynthetic N use efficiency. Self-shading may have causedA to decline at a high Nlm inP. sitchensis andT. plicata. Measurements of gas exchange and δ13C suggested that carboxylation capacity increased more than did stomatal conductance as Nlm increased. The responses were small and confined to Nlms associated with the lesser rates of N addition. Concentrations of total protein, ribulose 1,5-bisphosphate carboxylase (RUBISCO) and the light harvesting chlorophyll a/b protein complex (LHC) increased with Nlm, but the fraction of foliar N allocated to RUBISCO and LHC increased with Nlm only inP. sitchensis and only between the 0.025 and 0.05N regimes. The responsiveness ofA and concentrations of RUBISCO to Nlm were less than reported for deciduous C3 species.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0931-1890
    Keywords: Key words Nitrogen ; Photosynthesis ; Picea sitchensis ; Thuja plicata ; Tsuga heterophylla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The effects of differing, exponentially increasing rates of N addition (0.025, 0.05, 0.07 and 0.09 gN gN–1day–1) on photosynthesis, discrimination against 13C and partitioning of foliar N to chlorophyll and major photosynthetic proteins were compared in seedlings of the evergreen conifers Picea sitchensis, Thuja plicata and Tsuga heterophylla. T. heterophylla had the lowest range of foliar N concentrations (Nlm). Across species, photosynthetic rates (A) increased linearly with Nlm to a maximum at 21 mg g–1 and declined at higher Nlms. Species differences in A resulted from differences in Nlm, not from differences in photosynthetic N use efficiency. Self-shading may have caused A to decline at a high Nlm in P. sitchensis and T. plicata. Measurements of gas exchange and δ13C suggested that carboxylation capacity increased more than did stomatal conductance as Nlm increased. The responses were small and confined to Nlms associated with the lesser rates of N addition. Concentrations of total protein, ribulose 1,5-bisphosphate carboxylase (RUBISCO) and the light harvesting chlorophyll a/b protein complex (LHC) increased with Nlm, but the fraction of foliar N allocated to RUBISCO and LHC increased with Nlm only in P. sitchensis and only between the 0.025 and 0.05N regimes. The responsiveness of A and concentrations of RUBISCO to Nlm were less than reported for deciduous C3 species.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-7217
    Keywords: body mass ; obesity ; premenopausal bilateral breast neoplasms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Previous studies using current or recent adult body weight and body mass index are inconclusive as to a possible effect of increased body mass on premenopausal breast cancer incidence. Only five studies have presented data onearly adult body mass, and no study has reported these data for premenopausalbilateral breast cancer. Because premenopausal bilateral breast cancer is assumed to be partly genetic and partly environmental in origin, it is crucial to identify possible modifiable risk factors for this cancer. We present data on early adult body weight and body mass (Quetelet Index, QI) from a case-control study of 142 premenopausal bilateral breast cancer cases from Los Angeles County, California, Connecticut, and Quebec, Canada, and 229 sister controls. The odds ratio (and 95% confidence interval) of premenopausal breast cancer adjusted for age, education, alcohol consumption, and oral contraceptive use was 0.7 (0.3-1.4) for women in the highest tertile of QI at age 18. The results do not suggest thatelevated body mass index at a young age increases the risk of premenopausal bilateral breast cancer, but lend only weak support to the hypothesis of aninverse association between body mass index and premenopausal breast cancer.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-7217
    Keywords: reproductive factors ; alcohol ; smoking ; premenopausal bilateral breast neoplasms ; case-control study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Premenopausal bilateral breast cancer is characterized by a strong family risk, and, consequently, a high probability that inherited susceptibility genes may be segregating in these families. Determining whether risk factors that affect other breast cancer cases have a similar effect in the etiology of bilateral breast cancer is of interest. Therefore, as part of an ongoing genetic-epidemiologic study of premenopausal bilateral breast cancer, we conducted a case-control analysis of reproductive variables, benign breast disease, alcohol, and smoking. Cases had premenopausal bilateral breast cancer, and their unaffected sisters served as controls. A set of reproductive variables — including earlier age at menarche, nulliparity, and late age at first full term pregnancy — appeared to increase the risk of breast cancer; the corresponding confidence limits, however, were wide and straddled the null. In addition, other variables associated with increased premenopausal bilateral breast cancer risk were: use of oral contraceptives, history of benign breast disease, and high alcohol consumption. We found no positive association for smoking. Nulliparity and late age at first full-term pregnancy appeared to have different effects in women with family histories of breast cancer than in women without such a history. We detected no substantial effect modification for the other risk factors. In general, risk factors previously identified for breast cancer (usually postmenopausal, unilateral cases) appear also to increase the risk for premenopausal, bilateral breast cancer.
    Type of Medium: Electronic Resource
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