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Biomedical subjects

M Kreitner

Publications and source records attributed to M Kreitner.

5 recordsLinked to original sources
PubMed1996

Natural products derived from plants as potential drugs for the photodynamic destruction of tumor cells.

Chlorophyll and some of its synthetically produced derivatives are important sensitizers in photodynamic cancer therapy. Other natural products from plants with light dependent activity include quinones like hypericin and fagopyrin. These compounds have extended pi-electron systems which upon photoexcitation with visible light are responsible for singlet oxygen production. Other plant constituents which show UV light induced photosensitizing activity are furanocumarins like psoralen and angelicin, aflatoxins and alkaloids, as well as thiophene derivatives, terthienyl and several polyacetylenes. The photodynamic properties of a chelidonium alkaloid derivative and data for its potential clinical applicability are given.

Antineoplastic Agents↗
PubMed1996

Hypericin in phototherapy.

We describe the first local use of hypericin as photosensitizer for photodynamic therapy in a patient with recurrent malignant mesothelioma. Hypericin is a polycyclic quinone, which has been shown to possess in vivo and in vitro antiretroviral and photosensitizing activity; moreover, it is used in depressive disorders. The semiquinone radical, singlet oxygen, and superoxide anion radical are reported to be the toxic agents in hypericin phototherapy. Our first experience with locally applied hypericin in a superficial tumor-plate was performed 8 weeks after the systemic administration of hematoporphyrin derivatives. For tumor light illumination we used an argon pumped dye laser tuned to 632 nm. Owing to satisfactory results, we repeated the same therapy 4 weeks later- and no therapeutic effect was noted. Following this, we proved the interstitial application of HPD and the combination of interstitial HDP and superficially applied hypericin. The subsequent light illumination 6 hours later had no efficacy in the HDP-photosensitized area but there was tumor destruction in the field with both administered photosensitizers. Our first experience suggests a potentiation of two photosensitizers: hematoporphyrin derivatives and hypericin.

Aged↗
PubMed1996

Determination of Photosan III in human plasma.

In order to develop an accurate and quick method for the determination of Photosan III in human plasma, we used statistically planned experiments with an aim to identify the factors that can influence the analysis. Through a series of 20 experiments based on acid extraction of the porphyrin from the plasma and subsequent fluorescence analysis a calibration was obtained between 0 and 3.3 x 10(-5) M. The deviation of the parameters around the regression line is 3.02%, the coefficient of variation 3.55%.

Adult↗
PubMed1993

A quantitative determination of singlet oxygen with horseradish peroxidase.

A singlet oxygen determination method based on the formation of dimethyl-(2,5)-2-methoxy-5-hydroperoxydihydrofuran (DMFO2) followed by acid hydrolysis with 0.1 N H2SO4 is described. Hydrogen peroxide is formed thereby as a product of hydrolysis which is then determined by the horseradish peroxidase-catalyzed formation of the homovanillic acid dimer. Since DMFO2 is a crystalline compound with sufficient stability it can be used as a primary standard for the determination. The peroxidase-catalyzed hydrogen peroxide determination allows detection of singlet oxygen concentrations as low as 10(-7) M.

Free Radicals↗