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Biomedical subjects

A Bunke

Publications and source records attributed to A Bunke.

6 recordsLinked to original sources
PubMed2000

Validation of a capillary electrophoresis method for determination of 5-aminolevulinic acid and degradation products.

A capillary electrophoresis method was developed for simultaneous quantification of 5-aminolevulinic acid (ALA) and its degradation products 2,5-dicarboxyethyl-3,6-dihydropyrazine and 2,5-dicarboxyethylpyrazine in aqueous solution within a total analysis time of 9 min. The optimized method was validated with respect to specificity, precision, linearity, limits of detection and quantitation, and robustness. The degradation products were quantified with respect to the ALA peak. A related micellar electrokinetic chromatography method, involving the addition of sodium dodecylsulfate to the running buffer solution, was applied for direct injection of an oil-in-water emulsion containing ALA, i.e. without sample pretreatment.

Aminolevulinic Acid↗
PubMed2000

Degradation mechanism and stability of 5-aminolevulinic acid.

The physiological substance and precursor of the heme synthesis 5-aminolevulinic acid (ALA) is a promising prodrug for photodiagnosis and photodynamic therapy of epithelial tumors, particularly in urological and gynecological tissues. For the clinical use of this substance, a chemically stable and sterile drug formulation is required. In the present study, degradation mechanism of ALA in aqueous solution and possibilities to improve its stability were examined. A capillary electrophoretic method was developed that was suitable for the quantification of ALA and of two degradation products. The intermediate degradation product was 2, 5-dicarboxyethyl-3,6-dihydropyrazine, which was further oxidized to 2,5-dicarboxyethylpyrazine. The structures of the degradation products were proven by (1)H and (13)C nuclear magnetic resonance spectroscopy. ALA degradation was very efficiently inhibited by adjusting the pH of the aqueous solution to a value <5 and by purging with nitrogen. Additives such as antioxidants did not improve the ALA stability. These results demonstrated that low pH ALA aqueous solution may be one possible dosage form to be considered for market introduction.

Aminolevulinic Acid↗
PubMed1982

Argon laser trabecular surgery as an alternative to carbonic anhydrase therapy.

Thirty-four eyes (25 patients) with diagnosed chronic open angle glaucoma on maximal medical therapy were studied to determine whether argon laser trabecular surgery was a desirable alternative to carbonic anhydrase therapy. Ninety-four per cent of patients responded favourably to argon laser trabecular surgery as an alternative to carbonic anhydrase therapy. The average pressure drop was 9.9 mm Hg. Interestingly, there was a mean drop of 4.2 mm Hg in the contralateral eye. There was minimal, if any, iris response although there was a small but probably not clinically significant decrease in corneal endothelial cell count. Blanching of the trabecular wall was used as the endpoint to help minimize post-laser pressure rise. Blacks and aphakic patients responded satisfactorily. Laser surgery is best reserved for those patients with a pretreatment intraocular pressure no higher than the 30 to 35 mm Hg level. Trabeculectomy, in spite of its known complications, offers a better prognosis in those cases where the pretreatment pressure exceeds the 30 to 35 mm Hg level.

Aged↗
PubMed1981

Gradual increase in the sensitivity of extraocular muscles to acetylcholine during topical treatment of rabbit eyes with isoflurophate.

During the course of four to 14 days of topical application of isoflurophate ointment to rabbit eyes, there was a gradual increase in the sensitivity to acetylcholine of the superior recti muscles of treated eyes in vitro in the absence but not in the presence of eserine. The development of increased sensitivity to acetylcholine was accelerated when isoflurophate was applied twice daily. This increased sensitivity to acetylcholine was maintained when, after two weeks of twice-daily isoflurophate treatment, the frequency of administration was decreased to two applications per week. Partial reversal of this effect occurred seven to 14 days after the last isoflurophate treatment.

Acetylcholine↗
PubMed1978

Endophthalmitis after trabeculectomy.

Two cases of late endophthalmitis after trabeculectomy surgery are described. Despite intensive antibiotic therapy, the visual end result in both cases was poor. The incidence of endophthalmitis after trabeculectomy, according to this report is similar to that after Scheie's procedure, but less than that after trephination. A possible cause of endophthalmitis is the anterior dissection of the superficial scleral flap into the cornea.

Aged↗