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Biomedical subjects

E Aktas

Publications and source records attributed to E Aktas.

5 recordsLinked to original sources
PubMed2000

Reagentless enzyme electrode based on phenothiazine mediation of horseradish peroxidase for subnanomolar hydrogen peroxide determination.

The development and characterization of a highly sensitive enzyme immobilized carbon based electrode for the determination of subnanomolar concentrations of hydrogen peroxide in aqueous samples is described. The biosensor consists of horseradish peroxidase (HRP) immobilized in solid carbon paste along with a suitable redox mediator. The latter allows the acceleration of the electroreduction of HRP in the presence of hydrogen peroxide. Several phenothiazines as mediators are investigated in a comparative manner and with respect to dimethylferrocene using cyclic voltammetry and amperometry. Insolubilization of the HRP in the solid carbon paste is achieved by cross-linking the enzyme with glutaraldehyde and bovine serum albumin. Several experimental parameters such as pH, mediator and enzyme content are considered. The hydrogen peroxide determination is better carried out in 0.1 M acetate buffer, pH 4.5, by amperometry at an applied potential of 0.0 V versus Ag/AgCl, 3 M NaCl concentration and by using the phenothiazine base as redox mediator. The biosensor response is linear over the concentration range 2 nM-10 microM with a detection limit of 1 nM. The linear range of the hydrogen peroxide response without a mediator in the biosensor is found between 2 and 40 microM. The biosensor can be used for more than 180 measurements. Additional modification of the electrode by incorporation of Nafion SAC-13 microparticles in the solid carbon paste allows detection of concentrations of hydrogen peroxide as low as 0.1 nM.

Biosensing Techniques↗
PubMed1998

Phytoestrogens and inhibition of angiogenesis.

The consumption of a plant-based diet can prevent the development and progression of chronic diseases associated with extensive neovascularization, including the progression and growth of solid malignant tumours. We have previously shown that the plant-derived isoflavonoid genistein is a potent inhibitor of cell proliferation and in vitro angiogenesis. Moreover, the concentration of genistein in the urine of subjects consuming a plant-based diet is 30-fold higher than that in subjects consuming a traditional Western diet. We have also reported that certain structurally related flavonoids are more potent inhibitors than genistein. Indeed, 3-hydroxyflavone, 3',4'-dihydroxyflavone, 2',3'-dihydroxyflavone, fisetin, apigenin and luteolin inhibit the proliferation of normal and tumour cells as well as in vitro angiogenesis at half-maximal concentrations in the lower micromolar range. The wide distribution of isoflavonoids and flavonoids in the plant kingdom, together with their anti-angiogenic and anti-mitotic properties, suggest that these phytoestrogens may contribute to the preventive effect of a plant-based diet on chronic diseases, including solid tumours.

Cell Division↗
PubMed1997

Flavonoids, dietary-derived inhibitors of cell proliferation and in vitro angiogenesis.

Consumption of a plant-based diet can prevent the development and progression of chronic diseases associated with extensive neovascularization, including solid malignant tumors. In previous studies, we have shown that the plant-derived isoflavonoid genistein is a potent inhibitor of cell proliferation and in vitro angiogenesis. In the present study, we report that certain structurally related flavonoids are more potent inhibitors than genistein. Indeed, 3-hydroxyflavone, 3',4'-dihydroxyflavone, 2',3'-dihydroxyflavone, fisetin, apigenin, and luteolin inhibited the proliferation of normal and tumor cells, as well as in vitro angiogenesis, at half-maximal concentrations in the low micromolar range. We have previously demonstrated that genistein concentrations in the urine of subjects consuming a plant-based diet is 30-fold higher than in subjects consuming a traditional Western diet. The wider distribution and the more abundant presence of flavonoids in the plant kingdom, together with the present results, suggest that flavonoids may contribute to the preventive effect of a plant-based diet on chronic diseases, including solid tumors.

Animals↗
PubMed1995

The prognostic significance of cervico-vaginal cytology in endometrial cancer.

In patients with endometrial cancer, preoperative identification of certain poor prognostic factors is helpful in planning therapy. To determine the place of cervico-vaginal cytology in this respect, we have studied the relationship between cervico-vaginal cytology and the well-known prognostic factors of endometrial cancer such as grade, myometrial invasion, peritoneal cytology, stage and histological subtype. A hundred and sixty two patients, all of whom underwent surgical therapy in our clinic, were included in this study in order to correlate the cytological results with the pathological findings. Cervico-vaginal cytology was negative in 88 patients (54%), suspicious in 26 patients (16%) and malignant in 48 patients (30%). Twenty four per cent of cases with adenocarcinoma and adenoachantoma, and fifty two per cent of patients with adenosquamous carcinoma, papillary adenocarcinoma and clear cell carcinoma had positive cervicovaginal cytology (p < 0.001). Seventy four per cent of patients with negative cervico-vaginal cytology had grade I tumor, while 5% of patients with negative cytology had grade III tumor. On the other hand, only 9% of patients with positive cervico-vaginal cytology had grade I tumor, while 55% had grade III tumor (p < 0.001). 8% of patients with inner 1/2 myometrial invasion had positive cytology, whereas 51% of patients with 1/2 outer myometrial invasion had malignant cells in their smear (p < 0.001). As for the staging of the endometrial cancer according to FIGO, 19% of patients with Stage I disease had positive cervico-vaginal cytology while 60% of patients in Stage II and 66% of patients in Stage III-IV had positive cytology (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗