Browsing by Person "Lambert, Christine"

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Combined effects of drought and soil fertility on the synthesis of vitamins in green leafy vegetables
(2023) Park, Taewan; Fischer, Sahrah; Lambert, Christine; Hilger, Thomas; Jordan, Irmgard; Cadisch, Georg
Green leafy vegetables, such as Vigna unguiculata, Brassica oleraceae, and Solanum scabrum, are important sources of vitamins A, B1, and C. Although vitamin deficiencies considerably affect human health, not much is known about the effects of changing soil and climate conditions on vegetable vitamin concentrations. The effects of high or low soil fertility and three drought intensities (75%, 50%, and 25% pot capacity) on three plant species were analysed (n = 48 pots) in a greenhouse trial. The fresh yield was reduced in all the vegetables as a result of lower soil fertility during a severe drought. The vitamin concentrations increased with increasing drought stress in some species. Regardless, the total vitamin yields showed a net decrease due to the significant biomass loss. Changes in vitamin concentrations as a result of a degrading environment and increasing climate change events are an important factor to be considered for food composition calculations and nutrient balances, particularly due to the consequences on human health, and should therefore be considered in agricultural trials.
Role of reactive oxygen species in anti-cancer treatment: Investigations in 2-methoxyestradiol chemotherapy and 5-aminolevulinic acid based photodynamic therapy combined with hyperthermia
(2003) Lambert, Christine; Frank, Jürgen
The thesis deals with two different ROS-generating anti-cancer treatments: chemotherapy with the endogenous estrogen metabolite 2-methoxyestradiol and 5-aminolevulinic acid based photodynamic therapy. Both treatments were investigated with the rat DS-sarcoma model, which can be used in vitro and in vivo. It the first part, it could be shown that 2-methoxyestradiol induces apoptosis in DS-sarcoma cells. Translocation of the pro-apoptotic protein Bax to the mitochondria was identified as initial apoptotic event, followed by a decrease in mitochondrial transmembrane potential and the release of AIF out of the mitochondria. In addition, upregulation of FasL and TNFalpha by 2-ME, two death receptor ligands, was observed. Although, 2-ME administration resulted in activation of caspases, pan caspase inhibitor Z-VAD-FMK could not block 2-ME induced apoptotic cell death pointing to a caspase-independent mechanism. Furthermore, an increase in formation of reactive oxygen species was observed after 2-ME treatment. However, supplementation with different antioxidants could not decrease the toxic effect of 2-ME. This finding may indicate, that reactive oxygen species are not involved in apoptosis induction, rather they are a consequence of mitochondrial damage. In vitro and in vivo combination of 2-ME with another ROS-generating treatment resulted in a synergistic anti-tumour effect. In the second part of the thesis anti-tumour effects of 5-aminolevulinic acid based photodynamic therapy combined with simultaneous hyperthermia was investigated. Analysis of apoptosis associated nuclear changes clearly demonstrated the high efficiency of this treatment regime. Formation of reactive compounds (e.g. ROS, nitrogen monoxide, peroxynitrite) which is mainly responsible for toxicity of PDT, could be assessed in the shape of massive protein nitrosylation in tumours treated with PDT alone or the combined treatment. Detection of decreased amounts of heat shock proteins (HSP70 and HO-1) which protect tumour cells against damaging influences, lowered glutathione levels and reduced MMP-activity indicate an increase in degradation of proteins. This phenomenon may be caused by excessive generation of ROS. Taken together, the presented studies could demonstrate the high benefit of combining 2-ME resp. ALA-PDT with hyperthermia (or other ROS-generating therapies), which make them interesting candidates for future clinical applications.