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K Stolze

Publications and source records attributed to K Stolze.

32 records · Page 2Linked to original sources
PubMed1991

Is oxidative stress primarily involved in reperfusion injury of the ischemic heart?

Reperfusion injury of ischemic organs is suggested to result from metabolic derangements initiating an imbalanced formation of free oxygen radicals. Most investigators in this field have used the spin-trap 5,5'-dimethyl-N-pyrroline-N-oxide (DMPO) to stabilize these short-lived radicals and make them visible by means of the electron spin resonance (ESR) technique. ESR signals obtained from intravascular DMPO were reported to indicate the formation of free OH. radicals and, in some cases, also carbon-centered radicals. We were unable to confirm these findings. Carbon-centered radicals were not obtained irrespectively of conditions studied, while oxygen-centered DMPO-adducts could only be detected in minor amounts. Instead, we observed an ascorbyl-related ESR signal. The addition of ethylenediaminetetraacetic acid (EDTA), which was used by many investigators in this field, was found to greatly influence ESR-spectra of the reperfusion fluid. The ascorbyl radical concentration was clearly reduced and the DMPO-OH. adduct became more prominent. The addition of iron further stimulated this change eliciting a Fenton-type reaction responsible for DMPO-OH.-related ESR spectra in the perfusate after ischemia. Accordingly, we observed the release of iron and ascorbic acid into the perfusate as a consequence of ischemia. We could demonstrate that iron in the presence of ascorbate and EDTA causes both types of radicals detected in the perfusate. DMPO-OH. generation in the presence of EDTA was found to result from free OH. radicals that were not generated in the absence of EDTA.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Formation of methemoglobin and phenoxyl radicals from p-hydroxyanisole and oxyhemoglobin.

The reaction of p-hydroxyanisole with oxyhemoglobin was investigated using electron spin resonance spectroscopy (ESR) and visible spectroscopy. As a reactive reaction intermediate we found the p-methoxyphenoxyl radical, the one-electron oxidation product of p-hydroxyanisole. Detection of this species required the rapid flow device elucidating the instability of this radical intermediate. The second reaction product formed is methemoglobin. Catalase or SOD had no effect upon the reaction kinetics. Accordingly, reactive oxygen species such as hydroxyl radicals or superoxide could not be observed although the spin trapping agent DMPO was used to make these short-lived species detectable. When the sulfhydryl blocking agents N-ethylmaleimide or mersalyl acid were used, an increase of the methemoglobin formation rate and of the phenoxyl radical concentration were observed. We have interpreted this observation in terms of a side reaction of free radical intermediates with thiol groups.

Anisoles↗
PubMed1990

EPR studies on the oxidation of hydroxyurea to paramagnetic compounds by oxyhemoglobin.

N. Hydroxyurea forms methemoglobin from oxyhemoglobin with concomitant formation of the aminocarbonylaminooxyl radical H2N-CO-NHO., as detected with electron paramagnetic resonance spectroscopy (EPR). This radical could be detected for several hours in a low steady-state concentration. Approximately 1 hr after the reaction had been started, the EPR spectra of two additional paramagnetic intermediates could be detected at low temperature (77 degrees K), a low-spin ferric methemoglobin complex with hydroxyurea (MetHb-NHOH-CO-NH2) and the hemoglobin-nitric oxide adduct (Hb2(+)-NO). The intensities of their EPR spectra increased steadily over the range of more than 64 hr. The low-spin ferric methemoglobin complex was immediately formed when hydroxyurea was dissolved in a methemoglobin whereas the nitric oxide complex was possibly an oxidation product of the MetHb-hydroxyurea adduct. Its oxidative degradation is known to lead to the very toxic compounds nitric oxide and nitrogen dioxide which can therefore contribute to the toxic action of hydroxyurea.

Animals↗
PubMed1990

Free radical intermediates in the oxidation of N-methylhydroxylamine and N,N-dimethylhydroxylamine by oxyhemoglobin.

Nitroxide radicals have been detected in the methemoglobin formation reaction between oxyhemoglobin and the substituted hydroxylamine compounds, N-methylhydroxylamine and N,N-dimethylhydroxylamine, by ESR spectroscopy. The stability of these nitroxide radicals was considerably higher than that of the NH2O. radical derived from unsubstituted hydroxylamine. Only in the case of N-methylhydroxylamine the detection of the nitroxide radical required the use of a flow system, because the radical was found to undergo a rapid degradation with the concomitant formation of a secondary product, the beta-aminonitroxide CH3NO.CH2NH2. The nitroxide radical derived from N,N-dimethylhydroxylamine and oxyhemoglobin was stable for more than 1 hour. In addition, formation of low-spin iron-(III)-complexes from methemoglobin and excess substituted hydroxylamine was observed in both cases. Neither N-methylhydroxylamine nor N,N-dimethyldroxylamine formed the hemoglobin-nitric oxide complex found with unsubstituted hydroxylamine. Parallels and differences in the reaction path of un-, mono- and disubstituted hydroxylamines are discussed.

Animals↗
PubMed1989

Detection of free radicals as intermediates in the methemoglobin formation from oxyhemoglobin induced by hydroxylamine.

Four distinct paramagnetic intermediates could be observed in the reaction between oxyhemoglobin and hydroxylamine using ESR spectroscopy. The radical species exhibited different stability properties thus different techniques were required for their detection. Two of them were identified as the hydronitroxide radical (NH2O.) and the hemoglobin-nitric oxide complex (Hb2+-NO). The third one is a low-spin iron-(III)-complex, possibly the methemoglobin-hydroxylamine adduct. A fourth paramagnetic species was detected only in the absence of the iron chelator DETAPAC thus indicating that free iron ions were responsible for the formation of this intermediate. The same species was observed when a Fenton system was used to generate the radicals. This species was identified as being the Fe(NO)2X2 complex described in the literature (X = inorganic anions such as OH- or PO3-(4). The identification of the radical intermediates detected in the hydroxylamine-induced methemoglobin formation contributes to a more detailed understanding of the reaction sequence.

Animals↗
PubMed1989

Free radical intermediates formed during the oxidation of cyanide by horseradish peroxidase/H2O2 as detected with nitroso spin traps.

Aqueous solutions of cyanide react with hydrogen peroxide/horseradish peroxidase and form the cyanyl radical, which can be trapped by 2-methyl-2-nitrosopropane (t-nitrosobutane, tNB) at pH 9.8. At lower pH a variety of radical adducts are formed; at higher pH, the main product was the spin adduct of the formamide radical with tNB. The use of deuterated tNB and 15N-labeled potassium cyanide allowed the observation of the very small nitrogen coupling of this radical adduct. Experiments using 3,5-dibromo-4-nitrosobenzenesulfonic acid (DBNBS) as the spin trap yielded only the formamide radical adduct, which was identified by an independent synthesis starting from formamide. Both hydrogen splittings of its amino group could be resolved using deuterated DBNBS as the spin trap.

Benzenesulfonates↗
PubMed1989

[Additional treatment with Esberitox N in patients with chemo-radiotherapy treatment of advanced breast cancer].

A study was made at random on 70 female patients with advanced mamma carcinoma to find out whether an additional treatment with Esberitox N prevents or diminishes the sideeffects of a combined chemo-radiation therapy. As it could not be excluded that the efficacy of Esberitox N on previous affliction by haematotoxic therapy would probably differ, the study was made on various groups of risk. The parameter to form an opinion were either the peripheral hematosis or the appearance of infections. It turned out, however, that Esberitox N proved only effective if there was only a minor damage of the bonemarrow. The efficacy seems to promote the recuperation of the haemapoetic system. There was no significant frequency of infections by the additional Esberitox N treatment, yet in tendency favourably influenced.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1988

Oxidation of cyanide to the cyanyl radical by peroxidase/H2O2 systems as determined by spin trapping.

The cyanyl radical was formed during the oxidation of potassium or sodium cyanide by horseradish peroxidase, lactoperoxidase, chloroperoxidase, NADH peroxidase, or methemoglobin in the presence of hydrogen peroxide. The spin adducts of the cyanyl radical with 5,5-dimethyl-1-pyrroline-N-oxide and N-tert-butyl-alpha-phenylnitrone were quite stable at neutral pH. The identity of these spin adducts could be demonstrated using 13C-labeled cyanide and by comparison with the spin adducts of the formamide radical, a hydrolysis product of the cyanyl radical adduct. The enzymatic conversion of cyanide to cyanyl radical by peroxidases should be considered in addition to its well-known role as a metal ligand. Furthermore, since cyanide is used routinely as an inhibitor of peroxidases, some consideration should be given to the biochemical consequences of this formation of the cyanyl radical by the catalytic activity of these enzymes.

Cyanides↗
PubMed1988

[Supplementary treatment with Esberitox of female patients undergoing curative adjuvant irradiation following breast cancer].

1. The study was supposed to investigate a possible prevention or reduction of the toxicity of radiotherapy by an additional treatment with Esberitox. This question arose when performing an investigation about the effect of Esberitox in a combined chemo-radiotherapy. Whereas the latter induces above all a systemic damage to the hemopoietic system, radiotherapy is a regional noxa. 2. The present prospective, randomized study was conducted with 50 patients submitted to curative adjuvant irradiation following surgery for mammary carcinoma. The radiotherapy was performed in the same way in all patients with irradiations of the thoracic wall and the regional lymph nodes. Two groups were built by randomization. The study group received an additional treatment with Esberitox, the control group did not receive an additional treatment. 3. As a result, no protective influence of Esberitox could be demonstrated. The parameters investigated were the peripheral blood count (leucocytes, granulocytes, lymphocytes, monocytes, thrombocytes, hemoglobin, hematocrit) and the incidence of infections. 4. This result diverging from literature is discussed. It is probably affected by volume and extension of the injury induced by a hematotoxic noxa and furthermore by the ability of regeneration. If this ability is exhausted, the protective effect of Esberitox can act no longer. Therefore the essential factor seems to be the duration of exposure to the noxa. Esberitox was effective in case of a short toxicity, it was ineffective in case of prolonged toxicity, if the treatment continuity (noxa) was not broken up by some regeneration intervals. The radiotherapy studied in this trial had a duration of 50 days, and its effect was that of a longterm injury.

Adult↗
PubMed1987

Spin trapping artifacts in DMSO.

Spin-trapping experiments in alkaline aqueous dimethyl sulfoxide (DMSO) solution using sodium 3,5-dibromo-4-nitrosobenzenesulfonate (DBNBS) yielded a strong signal of the sulfur trioxide anion radical adduct. This radical adduct is identical to that obtained by the oxidation of sulfite with horseradish peroxidase/hydrogen peroxide and subsequent spin trapping with DBNBS. This radical adduct is very stable, and satellite peaks of the natural abundance 13C and 33S could be obtained. Apparently, under alkaline conditions DMSO decomposes in air to form the sulfur trioxide anion radical. A comparison with a recent publication shows that this DMSO-derived radical adduct has been misassigned as a uniquely stable spin adduct of superoxide (Ozawa and Hanaki (1986) Biochem. Biophys. Res. Commun. 136, 657-664).

Benzenesulfonates↗
PubMed1978

Does a temperature gradient exist across the mucogingival junction?

On the assumption that the colour difference between attached gingiva and alveolar mucosa is accompanied by a temperature difference, twenty subjects with a high standard of oral health were studied. Five points on either side of the mucogingival junction were examined by means of a thermocouple probe. A mean difference amounting to about 2/3 degrees C was found between the surface temperatures of the two structures.

Adult↗