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Biomedical subjects

B Roeder

Publications and source records attributed to B Roeder.

13 recordsLinked to original sources
PubMed1998

Improved healing with a collagen-alginate dressing in the chemical matricectomy.

A prospective clinical trial was conducted to evaluate the efficacy of a collagen-alginate wound dressing in the postoperative management of chemical matricectomies. The study involved 20 patients and 23 separate procedures. The collagen-alginate-dressing treatment group had an average healing time of 24.4 days, compared with 35.8 days for the control group, which received treatment consisting of soaks and daily dressing changes (P < .05). The authors suggest that using a collagen-alginate wound dressing in the postoperative management of chemical matricectomies will shorten healing time, thus reducing infection rates and increasing patient compliance and satisfaction.

Adolescent↗
PubMed1993

Photophysical properties of the photosensitizer pheophorbide a studied at high photon flux densities.

The photophysical properties of pheophorbide a (Pheo a) under two-step laser activation were investigated. For the first time quantum yields of higher excited state formation were calculated. It was shown that the quantum yields of the formation of these states depend strongly on the pulse duration of the excitation source. The nonlinear properties of Pheo a are quite different in dependence on the excitation wavelength but the quantum yields of the higher excited state formation in both cases (lambda exc = 337 nm and lambda exc = 667 nm) rise up increasing the photon flux density of the laser light up to 10(26) phot cm-2 s-1. A further increase of the photon flux density has no effect on the quantum yields.

Chlorophyll↗
PubMed1990

Photophysical studies of pheophorbide a and pheophytin a. Phosphorescence and photosensitized singlet oxygen luminescence.

The triplet states of pheophorbide a and pheophytin a were studied in several environments by direct measurement of the phosphorescence of the pigments and photosensitized singlet oxygen (1O2) luminescence. The spectra, lifetimes and quantum yields of phosphorescence and the quantum yields of 1O2 generation were determined. These parameters are similar for monomeric molecules of both pigments in all the environments studied. Aggregation of the pigment molecules leads to a strong decrease in the phosphorescence and 1O2 luminescence intensities, which is probably due to a large decrease in the triplet lifetime and triplet quantum yield in the aggregates. The results obtained for pheophorbide a and pheophytin a are compared with those previously reported for chlorophyll alpha. The data suggest that the photodynamic activity of the pigments in living tissues is probably determined by the monomeric pigment molecules formed in hydrophobic cellular structures. Aggregated molecules seem to have a much lower activity.

Chlorophyll↗
PubMed1990

Photophysical properties and photodynamic activity in vivo of some tetrapyrroles.

Some of the photophysical properties (stationary absorbance and fluorescence, fluorescence decay times and singlet oxygen quantum yields) of pheophorbide a, metal-free, ClAl-, Cu- and Mg-t-butyl-substituted phthalocyanines, metal-free, ClAl- and Cu-t-butyl-substituted naphthalocyanines and of a number of tetraphenylporphyrins (5,10,15,20-tetraphenylporphyrin, 5,10,15,20-tetra(m-hydroxyphenyl)porphyrin, 5,10,15,20-tetra(p-hydroxyphenyl)porphyrin) have been studied in comparison with hematoporphyrin IX in order to select potent photosensitizers for the photodynamic treatment of cancer. The photodynamic activity of these compounds was investigated using Lewis lung carcinoma in mice. As a consequence of the photophysical parameters (relatively short singlet state lifetimes, and high singlet oxygen quantum yields) the photodynamic activities of pheophorbide a, t-butyl-substituted ClAl-phthalocyanine and ClAl-naphthalocyanine were selected for study in greater detail. Under the conditions employed in the present study, pheophorbide a was found to be the most effective sensitizer, as judged from its strong absorption at the excitation wavelength as compared with the hematoporphyrin derivative and greater singlet oxygen quantum yield relative to the phthalocyanines and naphthalocyanines. The photodynamic activity was observed to be strongly dependent on the photophysical parameters of the compounds. The primary mechanism underlying the photodynamic activity of these sensitizers probably consists of energy transfer from the lowest triplet state of the dyes to molecular oxygen, resulting in the formation of singlet oxygen (type II of photosensitization).

Animals↗
PubMed1989

Generation of free radicals by photoexcitation of pheophorbide alpha, haematoporphyrin and protoporphyrin.

An investigation of the production of radical species by photoexcitation pheophorbide alpha, haematoporphyrin and protoporphyrin was performed. In an aqueous solution containing different amounts of ethanol, the superoxide radical was detected by the spin trapping technique. In addition, secondary radicals were observed. The generation of oxygen radicals was found to dominate in solutions with a low ethanol content.

Chlorophyll↗
PubMed1987

Time-resolved fluorescence spectroscopy of hematoporphyrin, mesoporphyrin, pheophorbide a and chlorin e6 in ethanol and aqueous solution.

The fluorescence decay I(t) and time-resolved spectra I(lambda, t) of some porphyrins and chlorins in ethanol and phosphate-buffered aqueous solution were investigated with a time-correlated single-photon-counting apparatus with a mode-locked Ar+ laser (514.5 nm) as the excitation source. The fluorescence of hematoporphyrin, mesoporphyrin and pheophorbide aa is considerably influenced by the conditions of aggregation (these compounds undergo aggregation in phosphate-buffered solution but not in ethanolic solution). The fluorescence decay of chlorin e6 which remains monomeric in both solvents is single exponential in all cases. The fluorescence spectra of hematoporphyrin, mesoporphyrin and pheophorbide a in phosphate-buffered solution are shifted with respect to the spectra obtained in ethanol; moreover, a new emission band (X band) appears, whose intensity increases on increasing the amount of equilibrium aggregates and shows a fast fluorescence decay. For hematoporphyrin and mesoporphyrin the appearance of the X band emission appears to be correlated with irreversible photoprocesses leading to fluorescent photoproducts. Analysis of the reported fluorescence spectra of cancer cells after incubation with hematoporphyrin derivative suggests that the fluorescent photoproducts might be formed also in vivo.

Chlorophyll↗
PubMedDate not supplied

Antibiotic beads in the treatment of diabetic pedal osteomyelitis.

Antibiotic-impregnated polymethylmethacrylate (PMMA) beads have improved the outcome of osteomyelitis treatment in both experimental models and clinical trials. The primary benefit of antibiotic-impregnated PMMA beads is that they provide high local concentrations of antibiotic while systemic levels of antibiotic remain low. Little has been written about the specific use of antibiotic-impregnated PMMA beads in the treatment of diabetic pedal osteomyelitis. The authors review antibiotic-impregnated PMMA beads and provide examples of their use in the treatment of diabetic pedal osteomyelitis.

Absorbable Implants↗