RESUMEN
BACKGROUND: Malignant glioma are often resistant to cisplatin. Numerous chemical modifications have been made to overcome this limitation. Analyzing such novel compounds, we previously hypothesized, that hydrophobicity improves the cytotoxicity of NH3 substituted platinum agents. MATERIALS AND METHODS: Testing this hypothesis, we synthesized further eight novel platinum agents, substituting the NH3 groups with various pyridyl ring systems. The cytotoxicity was measured in MTT tests using the cisplatin resistant human U25 1 malignant glioma cell line as a model. Solubility was measured in water using flameless atomic absorption spectroscopy. RESULTS: Cytotoxicity correlated significantly with low water solubility. The relation of cells surviving 72-hours of 1 OuM drug exposure was best described by a logarithmic formula: Surviving cells (% of control) = 6.4 + 38.4 log (water solubility in mg Pt/L) Adding an oximgroup to the aromatic substitute decreased cytotoxicity. CONCLUSIONS: These data confirmed that increased hydophobicity increases cytotoxicity in this group. This might be caused by better cellular penetration, or by shielding of DNA-adducts from repair processes. The data created a further hypothesis: A positive mesomeric effect as characteristic for the oxim-group might decrease DNA binding, a negative mesomeric might improve it.
Asunto(s)
Antineoplásicos/química , Diseño de Fármacos , Compuestos de Platino/química , Antineoplásicos/farmacología , Supervivencia Celular , Relación Dosis-Respuesta a Droga , Resistencia a Antineoplásicos , Ensayos de Selección de Medicamentos Antitumorales , Humanos , Peso Molecular , Compuestos de Platino/farmacología , Solubilidad , Células Tumorales Cultivadas/efectos de los fármacosRESUMEN
Transmission and reflection characteristics of inductive-mesh frequency-selective surfaces were measured in the 4-12-microm range. Specific issues investigated include the effect of interelement spacing on the location and width of the resonance and the influence of superstrate and substrate refractive indices on the spectral response of the structure.
RESUMEN
Comparisons of experiment and theory are presented for transmission spectra over the range 2-15 mum of a set of frequency-selective surfaces consisting of arrays of simple dipole patches of aluminum on or in silicon. The arrays are fabricated by direct-write electron-beam lithography. Important parameters controlling the spectral shape are identified, such as dipole length, spacing, resistance, and dielectric surroundings. The separate influence of these variables is exhibited. Encouraging agreement between simple model calculations and the measurements is found.
RESUMEN
The transmission of light along the surface normal through an air-quartz-glass interface covered with a periodic array of thin, rectangular gold patches has been studied over the visible to infrared range. The various structures that are observed can be qualitatively understood as arising from standing-wave resonances set by the size and surroundings of the metal patches. A method-of-moments calculational scheme provides simulations in good quantitative agreement with the data. It is shown how the standing-wave picture provides a useful conceptual framework to understand and exploit such systems.