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  • Bone mineral density  (2)
  • Chlamydomonas (l-amino-acid oxidase)  (2)
  • Springer  (4)
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  • Springer  (4)
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  • 1
    ISSN: 1432-0827
    Keywords: Bone mineral density ; Smokers ; Premenopausal women ; Mineral metabolism ; Sex steroids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract Smoking is related to decreased bone mass and increased risk of osteoporotic fractures. However, the harmful effects of smoking on bone have not been well characterized. The purpose of this study was to assess the repercussions of smoking on bone mass in premenopausal women, and the relationship between these effects and parameters of mineral metabolism and hormone profile. We measured bone mineral density (BMD) in 101 premenopausal women (47 smokers, 54 nonsmokers) with dualenergy X-ray absorptiometry (DeXA) of the proximal femur and lumbar spine. In a subgroup of the sample (16 smokers, 15 nonsmokers) we measured biochemical indicators of mineral metabolism and hormone profile. BMD in the femoral neck, Ward's triangle, and the intertrochanter region was significantly lower in smoker (P〈0.05) than in nonsmokers. Concentrations of sex hormone-binding globulin were higher, and free testosterone index (FTI) was lower (P〈0.05) in smokers. We found no significant differences between the groups in parameters of mineral metabolism. Concentrations of dehydroepiandrosterone sulfate and free testosterone index were directly correlated with values of BMD in different sites. Our findings show that smoking by premenopausal women is associated with decreased BMD and characteristic changes in the hormone profile.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 57 (1995), S. 94-96 
    ISSN: 1432-0827
    Keywords: Androgen insensitivity syndrome ; Hormone replacement therapy ; Bone mineral density
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract The response of bone mass to long-term treatment with estrogen and progesterone in patients with complete androgen-insensitivity syndrome (AIS) is unknown. We report a 17-year-old female patient (karyotype 46 X, Y) with AIS studied during a 4-year period. Bone mineral density (BMD) measured by dual X-ray absorptiometry in lumbar spine and proximal femur was sharply reduced at the initial visit, and remained unchanged during long-term follow-up on hormone replacement therapy with estrogens and progestin. Bone metabolism markers were all in the normal range. The lack of significant increase in BMD highlights the importance of androgens on bone physiology that cannot be balanced in spite of an appropriate estrogenic milieu.
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  • 3
    ISSN: 1432-2048
    Keywords: l-amino-acid oxidase (molecular properties) ; Chlamydomonas (l-amino-acid oxidase) ; Flavoprotein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An l-amino-acid oxidase (EC 1.4.3.1) that catalyzes the oxidative deamination of twelve l-amino acids has been purified 21-fold and with 14% yield to electrophoretic homogeneity from Chlamydomonas reinhardtii cells by ammonium-sulfate fractionation, gel filtration through Sephacryl and Superose, anion-exchange chromatography and preparative electrophoresis in polyacrylamide gels. The native enzyme is a protein of 470 kDa and consists of eight identical or similarsized subunits of 60 kDa each. Optimum pH and temperature were 8.2 and 55° C, respectively, with a Q10 (45–55° C) of 1.7 and an activation energy of 45 kJ · mol−1. Its absorption spectrum showed, in the visible region, maxima at 360 and 444 nm, characteristic of a flavoprotein with a calculated flavin content of 7.7 mol FAD per mol of native enzyme. Apparent K m values of the twelve l-amino acids which can act as substrates of l-amino-acid oxidase ranged between 31 μM for phenylalanine and 176 μM for methionine. The effect of several specific group reagents, chelating agents and bivalent cations on enzyme activity has also been studied.
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  • 4
    ISSN: 1432-2048
    Keywords: l-amino-acid oxidase (molecular properties) ; Chlamydomonas (l-amino-acid oxidase) ; Flavoprotein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Anl-amino-acid oxidase (EC 1.4.3.1) that catalyzes the oxidative deamination of twelvel-amino acids has been purified 21-fold and with 14% yield to electrophoretic homogeneity fromChlamydomonas reinhardtii cells by ammonium-sulfate fractionation, gel filtration through Sephacryl and Superose, anion-exchange chromatography and preparative electrophoresis in polyacrylamide gels. The native enzyme is a protein of 470 kDa and consists of eight identical or similarsized subunits of 60 kDa each. Optimum pH and temperature were 8.2 and 55° C, respectively, with a Q10 (45–55° C) of 1.7 and an activation energy of 45 kJ · mol−1. Its absorption spectrum showed, in the visible region, maxima at 360 and 444 nm, characteristic of a flavoprotein with a calculated flavin content of 7.7 mol FAD per mol of native enzyme. ApparentK m values of the twelvel-amino acids which can act as substrates ofl-amino-acid oxidase ranged between 31 μM for phenylalanine and 176 μM for methionine. The effect of several specific group reagents, chelating agents and bivalent cations on enzyme activity has also been studied.
    Type of Medium: Electronic Resource
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