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  • Aluminum toxicity  (2)
  • breast cancer  (2)
  • Springer  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Planta 192 (1993), S. 98-103 
    ISSN: 1432-2048
    Keywords: Aluminum toxicity ; Calcium uptake ; Growth inhibition ; Root ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The cation Al3+ is toxic to plants at micromolar concentrations and can severely inhibit root growth in solution experiments. Trivalent aluminum hydrolyzes in solution, and, apart from the Al3+ ion, which dominates speciation below pH 5.0, various mononuclear and polynuclear hydroxy-Al species can also occur (Kinraide 1991). Accumulating evidence suggests that Al3+ is the rhizotoxic species under the experimental conditions used in the present study (Kinraide 1991; Kinraide et al. 1992). The inhibition of Ca2+ uptake in roots by Al3+ has been proposed as a possible mechanism for Al3+ toxicity, and in this study the hypothesis was tested directly. Root growth and Ca2+ uptake were measured in 5-d-old seedlings of wheat (Triticum aestivum L. Thell) during exposure to Al3+ in a low-Ca2+ basal medium, and to Al3+ in the presence of added cations. Uptake of Ca2+ in whole roots and translocation to the shoot were measured using 45Ca2+, and localized measurements of net Ca2+ flux were also made at the root apex using the technique of microelectrode ion-flux estimation. Treatment with 2.64 μM AlCl3 in 226 μM CaCl2, at pH 4.5, severely inhibited root growth without affecting Ca2+ uptake. Addition of 30 mM Na2+, 3 mM Mg2+ or 50 μM tris(ethylenediamine)cobalt(III) to this Al3+ treatment restored root growth but significantly reduced Ca2+ uptake measured over the entire root system and at the root apex. The Al3+ and Ca2+ concentrations were adjusted so that the activities of the Al3+ and Ca2+ ions were constant in all solutions (1.5 μM and 200 μM, respectively). Root growth can be severely inhibited by Al3+ concentrations that do not affect Ca2+ uptake, while the addition of ameliorating cations depresses Ca2+ uptake. These results argue against the hypothesis that Al3+ inhibits root growth by reducing Ca2+ uptake.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Planta 192 (1993), S. 104-109 
    ISSN: 1432-2048
    Keywords: Aluminum toxicity ; Calcium displacement ; Electrical potential ; Root ; Triticum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several mineral rhizotoxicities, including those induced by Al3+, H+, and Na+, can be relieved by elevated Ca2+ in the rooting medium. This leads to the hypothesis that the toxic cations displace Ca2+ from transport channels or surface ligands that must be occupied by Ca2+ in order for root elongation to occur. In this study with wheat (Triticum aestivum L.) seedlings, we have determined, in the case of Al3+, that (i) Ca2+, Mg2+, and Sr2+ are equally ameliorative, (ii) that root elongation does not increase as Ca2+ replaces Mg2+ or Sr2+ in the rooting media, and (iii) that rhizotoxicity is a function solely of Al3+ activity at the root-cell membrane surface as computed by a Gouy-Chapman-Stern model. The rhizotoxicity was indifferent to the computed membrane-surface Ca2+ activity. The rhizotoxicity induced by high levels of tris(ethylenediamine)cobaltic ion (TEC3+), in contrast to Al3+, was specifically relieved by Ca2+ at the membrane surface. The rhizotoxicity induced by H+ exhibited a weak specific response to Ca2+ at the membrane surface. We conclude that the Ca2+-displacement hypothesis fails in the case of Al3+ rhizotoxicity and that amelioration by cations (including monovalent cations) occurs because of decreased membrane-surface negativity and the consequent decrease in the membrane-surface activity of Al3+. However, TEC3+, but not Al3+, may be toxic because it inhibits Ca2+ uptake. The nature of the specific H+-Ca2+ interaction is uncertain.
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  • 3
    ISSN: 1573-0646
    Keywords: doxorubicin ; iproplatin ; breast cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Forty-eight patients with advanced breast cancer were treated in a disease-specific phase I trial of doxorubicin and iproplatin combination chemotherapy. The doses of doxorubicin ranged between 30 and 50 mg/m2, and the doses of iproplatin ranged between 150 and 250 mg/m2. Myelosuppression was observed at all levels, but was dose-limiting at the highest level. In addition, nausea, diarrhea and malaise were prominent toxicities. Neither cardiac nor renal toxicity was encountered. Nine of 26 (35%) of previously untreated patients, and 5 of 22 (23%) previously treated patients demonstrated partial or complete responses. Although this combination possesses therapeutic activity, given its toxicities, further evaluation of doxorubicin in combination with iproplatin is not recommended.
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  • 4
    ISSN: 1573-0646
    Keywords: breast cancer ; Iproplatin ; CHIP ; phase II study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Twenty-five women with advanced breast cancer were treated in a phase II trial of iproplatin 275 mg/m2 administered intravenously every 4 weeks. All patients had measurable or evaluable indicator lesions, and had undergone treatment with no more than one previous chemotherapy regimen, including adjuvant chemotherapy. Two of the twenty-four evaluable patients (8%) experienced major therapeutic responses. One patient had a complete regression of pulmonary nodules lasting 18 + months; another had a partial regression of metastatic disease in the liver (4 months). The inevaluable patient was ineligible for the study because of previous radiation to the indicator lesions on her chest wall; nonetheless, she experienced a 10 month partial regression of those nodules. Myelosuppression was generally dose limiting; thrombocytopenia was more profound, but leukopenia was more prolonged. Nausea, vomiting, diarrhea, and general malaise were prominent toxicities, and led to discontinuation of therapy in 4 patients. Iproplatin has limited activity in previously treated women with advanced breast cancer.
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