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Nalidixic acid (1) gives with 2-naphthol a yellow charge-transfer complex. The 7-methyl group of 1 condenses with vanillin (2) and Ehrlich's reagent (4) to the coloured (E)-benzylidene compounds 3 and 5. Treating 1 with thionyl chloride and subsequent reaction with aminopyrazolone (6) and sodium acetate leads to a mixture of trichloronalidixic acid (7) and its 3-carboxamide 8. The trichloromethyl group of 7 is converted with 6 in pyridine to form the amide 9. Nalidixic acid reacts with 1,3-dimethylbarbituric acid (10) in acetanhydride/acetic acid to yield the polymethine dyes 11-13, whose structures are confirmed by X-ray crystal structure analysis. The dyes 3 and 12 inhibit the growth of staphylococcus aureus and Escherichia coli, respectively.

Unlabelled: Hitherto secondary cataract has been usually treated by Nd:YAG laser, which results in a dissection of the capsule with possible complications e.g. retinal detachment. Selective removal of the epithelial cells from the posterior capsule has not been possible. By use of dyes in connection with laser light of a suitable wavelength, lens epithelial cells could potentially be selectively destroyed. We investigated the dye indocyanine green, which has a peak absorbtion at the emission wavelength of commercially available diode lasers., Methods: Human lens epithelial cells and 3T3 cells (mouse embryonal fibroblasts) were grown in MEM with 10% FBS. Confluent and preconfluent layers were incubated with indocyanine green and treated with a diode laser attached to a slit lamp (810 nm, Zeiss VISULAS, Zeiss Oberkochen, Germany)., Results: Indocyanine green alone was toxic in concentrations above 5 mg/ml (60 min). Combined with laser treatment (200 mW, 100 ms, 160 microns), indocyanine green led to cell damage in preconfluent cultures at concentrations above 0.01 mg/ml (10 min). After about 2 days irradiated cells became necrotic and began to desquamate from the culture disc. Cells in confluent cultures could be devitalised at concentrations above 0.05 mg/ml (10 min) using the same power. In contrast, neither indocyanine green alone nor diode laser alone could interfere with epithelial proliferation., Discussion: The experiments show the possibility of dye-enhanced therapy of lens epithelial cells with indocyanine green and diode laser. In contrast to other photosensitizers, indocyanine green is widely used in human function tests. Therefore its use for the treatment of secondary cataracts may merit discussion.

Inhibition of cyclo-oxygenase reaction during prostaglandin formation in the renal medulla of the rat by 1,4-naphthoquinone derivatives is compared with the known enzyme inhibition properties of natural and synthetic flavonols. Structure-activity relationship study shows strong correlation between chemical properties (vicinal hydroxy-oxo structure of planar molecules) and physicochemical parameters (polarity and acidity). The most potent compounds are 2-ethyl-5-hydroxy-1,4-naphthoquinone (9) and 2-methyl-3-hydroxy-1,4-naphthoquinone (6).

4 nonenzymatic biochemical systems (NADH-mediator-tetrazolium; NADH-riboflavin-tetrazolium; methionine-riboflavin-tetrazolium; potassium superoxide (KO2)-tetrazolium) were tested as models for histochemical tetrazolium reduction. A NADH-PMS-tetrazolium system was proved to be most suitable. The reaction rates of some histochemically used tetrazolium salts, the stimulation of the reaction rates by the detergents Tween, Triton X-100, and N-Cetylpyridinium chloride and the effectiveness of some histologic dyes (oxazines, phenazines, thiazines) as mediators were determined as examples of application. The reported results are discussed in relation to the role of detergents and oxygen in the mechanism of tetrazolium reduction.

The albumin-binding of bilirubin may be disturbed by pharmacologically inert substances. This is true for Cardiogreen as used for dye dilution curves. The displacement of bilirubin from its albumin-bindung, examined in vitro by Sephadex filtration, is stronger for Cardiogreen than for Gantrisin known to cause kernicterus even in mild hyperbilirubinemia. However, from differences in dosage and the pharmacokinetics of the two substances it may be concluded, that the risk of possibly causing a kernicterus by Cardiogreen is limited to only extrem cases.