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Biomedical subjects

E F Elstner

Publications and source records attributed to E F Elstner.

At least 73 records · Page 4Linked to original sources
PubMed1985

Biochemical model reactions for cataract research.

There are several experimental indications that cataract formation is induced and/or enhanced by activated oxygen species including hydrogen peroxide, superoxide radical anion, singlet oxygen and hydroxyl radical. These species can be generated chemically, enzymatically or photodynamically. Taking advantage of endogenous photodynamic compounds in isolated lens, aqueous humor or vitreous preparations in the presence of S-methyl-alpha-ketobutyric acid (KMB), ethylene formation can be monitored for at least 2 h of light-dependent KMB degradation. This reaction is extremely sensitive and can be inhibited by potassium iodide in low concentrations. This model reaction might be useful for studying possibly inhibiting substances or stimulating processes involved in cataract formation.

Animals↗
PubMed1985

[The uptake of potassium iodide and its effect as an antioxidant in isolated rabbit eyes].

Potassium iodide (KI) passes the cornea of isolated rabbit eyes with kinetics of approximately 0.25 mumol/h/ml aqueous humor. In photodynamic reactions, simulated as light-dependent decay of S-methyl-alpha-ketobutyric acid in the presence of riboflavin, KI acts as an antioxidant cooperating with internal scavengers such as ascorbate. With the simple model reactions applied it may be possible to study mechanism and functions in vivo of eye-protecting factors or combinations of compounds.

Animals↗
PubMed1985

[Kinetics of uptake of Pherajod by the rabbit eye].

The aqueous humor and lenses of rabbit eyes contain inhibitors of photodynamic destructions. Preparations of vitreous, however, more likely seem to contain stimulatory compounds. The anticataractic drug Pherajod significantly blocks the photodynamic formation of destructive oxygen species. Inhibition by 65% of photodynamic destructions, measured as ethylene release from S-methyl-a-ketobutyric acid in the riboflavin-driven oxygen photoactivation, is observed with aqueous humor preparations isolated 5 min after start of incubation of rabbit eyes in Pherajod solution.

Animals↗
PubMed1985

Percoll reversibly inhibits superoxide dismutase.

Incubation of pea leaf extracts (Pisum sativum L.) at 6 degrees C in isoosmotic media containing different Percoll concentrations significantly represses the total superoxide dismutase (SOD) activity in a concentration- and time-dependent manner. After 24 h incubation at 6 degrees C, 30-45% Percoll concentrations bring about an inhibition of Mn-SOD activity of more than 50%. Isozyme Cu,Zn-SOD II is affected to a lesser extent, with a maximum inhibition of 36% at high Percoll concentrations, whereas isozyme Cu,Zn-SOD I undergoes only slight variations. However, dilution of the samples followed by electrophoresis completely removes the Percoll inhibitory action. Results suggest that superoxide dismutases could be adsorbed onto the Percoll surface through electrostatic interactions.

Fabaceae↗
PubMed1984

On the interaction of adriamycin with DNA: investigation of spectral changes.

The aerobic reduction of adriamycin by NADPH-cytochrome c-(ferredoxin)oxidoreductase was determined spectrophotometrically and found to consist of an initial slow phase, followed by a rapid stage. Superoxide was found to play a role in the reduction of the quinone drug only during the first phase. The second, faster stage of the reaction was not inhibited by superoxide dismutase, apparently due to the decreased oxygen tension in the reaction cuvette. When adriamycin was fully bound to DNA, no direct reduction by the enzymatic system was observed. However, in the presence of a superoxide-generating system, reduction of the adriamycin-DNA complex did occur.

Catalase↗
PubMed1982

Mechanisms of oxygen activation by nitrofurantoin and relevance to its toxicity.

Purified ferredoxin-(cytochrome c)-NADP+ oxidoreductase and xanthine oxidase were found to catalyse the reduction of nitrofurantoin to the free radical. Under aerobic conditions, the nitrofurantoin radical underwent autoxidation to regenerate the parent compound with the concomitant production of superoxide and eventually hydrogen peroxide. The nitrofurantoin radical was also shown to react with hydrogen peroxide to generate a highly reactive species which was capable of oxidising methionine to ethylene. This active oxygen radical appeared to be identical with the crypto-OH . radical, previously proposed as being formed from the analogous reaction of the methyl viologen radical with hydrogen peroxide [R.J. Youngman and E.F. Elstner, FEBS Lett. 129, 265 (1981)]. Catalase inhibited nitrofurantoin-dependent ethylene formation in both enzyme systems, whereas superoxide dismutase was only inhibitory in the xanthine oxidase mediated reaction. Although the primary function of the respective enzyme systems is to generate the nitrofurantoin radical, the xanthine oxidase reaction is markedly more complex than that of ferredoxin-(cytochrome c)-NADP+ oxidoreductase. The differences between the two enzyme reactions appear to be due to the endogenous autoxidation of xanthine oxidase. The aerobic activation of nitrofurantoin by xanthine oxidase involved the superoxide anion as an intermediate, whereas the nitrofuran was directly reduced by ferredoxin-(cytochrome c)-NADP+ oxidoreductase without a requirement for active oxygen species.

Catalase↗
PubMed1980

Oxygen utilization by Lactobacillus plantarum. I. Oxygen consuming reactions.

Lactobacillus plantarum (ATCC 8014) cells, grown aerobically on glucose medium, consumed molecular oxygen when incubated with either glucose, D/L-lactate or pyruvate as substrate. Cell extracts catalyzed the oxidation of NADH, D/L-lactate of pyruvate with O2. Per mol O2 2mol of NADH were consumed indicating that O2 was reduced to H2O; reduction proceeded via H2O2 involving a NADH oxidase and a NADH peroxidase. Catalase activity was absent. Pyruvate oxidation with O2 led to the formation of H2O2, lactate oxidation to the formation of H2O. Thus in L. plantarum different mechanisms are available by which molecular oxygen can be used as electron acceptor for oxidation reactions.

Glucose↗
PubMed1980

Oxygen utilization by Lactobacillus plantarum. II. Superoxide and superoxide dismutation.

Cell-free extracts of Lactobacillus plantarum contain non-proteinaceous compounds which mimic superoxide dismutase activity. Using the test system in which O-2 is generated by xanthine oxidase, superoxide dismutase activity is found in cell-free extracts, where proteins are removed by precipitation. This activity is strongly decreased after dialysis of cell-free extracts. Superoxide dismutase activity was also investigated by means of pulse radiolysis. Cell-free extracts of Escherichia coli were also investigated as a comparison, which were known to contain superoxide dismutase. With cell-free extracts of both L. plantarum and E. coli the decay of O-2 was markedly increased. However, the type of reaction of the O-2 decay was of first order in the presence of E. coli extracts due to superoxide dismutase(s), and of second order in the presence of L. plantarum extracts, indicating that O-2 elimination is not an enzymic reaction. Mn2+ phosphate(s) might be responsible for the observed elimination of O-2. The production of O-2 is not detectable during NADH-, lactate- or pyruvate oxidase reactions in L. plantarum extracts.

Cell-Free System↗
PubMed1980

Formation of ethylene from methionine. Reactivity of radiolytically produced oxygen radicals and effect of substrate activation.

Ethylene was determined by gas chromatography after reaction of radiolytically produced OH and O2- radicals with methionine, methionine + pyridoxal phosphate and S-adenosyl-methionine (SAM). Both oxygen radicals, alone or in combination, liberate ethylene from methionine and methionine/pyridoxal phosphate. From SAM ethylene was primarily produced by the combined attack of OH nad H2O2 or O2-.

Chromatography, Gas↗
PubMed1980

Production of Hexanal and Ethane by Phaeodactylum triconutum and Its Correlation to Fatty Acid Oxidation and Bleaching of Photosynthetic Pigments.

In a light-dependent reaction (3.5 kilolux) at pH 5, the evolution of hexanal, ethane, and ethylene has been established with cell suspensions of the diatom, Phaeodactylum tricornutum. During this process, chlorophyll and carotenoids are partially bleached. Addition of 25 millimolar alpha-linolenic acid or 12 millimolar docosahexaenoic acid yield total pigment destruction and enhancement of ethylene and ethane formation (by about 150 and 7,600%, respectively), whereas hexanal production decreases by 70%. Eicosapentaenoic acid, the major polyunsaturated fatty acid in diatoms, stimulates both ethane and hexanal formation (by about 1,400 and 130%, respectively), but reduces ethylene production (by about 60%). This competition suggests that the production of the volatile compounds is closely connected, although hexanal and ethylene obviously possess different unsaturated fatty acids as precursors. Both the kind of the fatty acids and their relative amounts seem to determine the pattern of the evolved hydrocarbons. The presence of 10 millimolar propylgallate inhibits the evolution of the volatile compounds by about 80%, indicating that radical formation might play a key role in this light-dependent cascade of reactions.

Journal Article↗
PubMed1980

Ethylene: indicator but not inducer of phytoalexin synthesis in soybean.

Cell wall preparations (elicitors) from Phytophthora megasperma var. sojae increase C(2)H(4) formation, phenylalanine ammonia lyase activity, and glyceollin accumulation in soybean cotyledons within about 1.5, 3, and 6 hours after treatment, respectively. The immediate precursor of C(2)H(4), 1-aminocyclopropane-1-carboxylic acid, stimulates C(2)H(4) formation like the elicitor within 1.5 hours after administration, whereas phenylalanine ammonia lyase activity and glyceollin concentration remain unchanged. Aminoethoxyvinylglycine, a specific inhibitor of C(2)H(4) formation in higher plants, inhibits elicitor-induced C(2)H(4) formation by about 95% but has no effects on phenylalanine ammonia lyase or glyceollin accumulation. It was concluded that C(2)H(4) is a signal accompanying the specific recognition process which finally leads to the induction of phytoalexin formation, but it is not functioning as a link or messenger in the induction sequence of glyceollin accumulation.

Journal Article↗
PubMed1978

Oxygen activation in isolated chloroplasts. Mechanism of ferredoxin-dependent ethylene formation from methionine.

Low-potential electron acceptors of photosystem I of chloroplast lamellae produce superoxide anions (0-2) and hydrogen peroxide by autoxidation, but have no effect on ethylene formation from methionine; equimolar amounts of ferredoxin are less active in photosynthetic O-2 and H2O2 production but strongly stimulate ethylene production from methionine. 2. Ten to fifty units of superoxide dismutase inhibit fifty to two hundred units of superoxide dismutase stimulate ethylene formation from methionine by chloroplast lamellae in the presence of ferredoxin. This stimulation is stronger at pH 7.0 than at pH 7.8. Catalase inhibits ethylene formation from methionine. 3. Pulse-radiolytic production of nitrite (NO-2) from hydroxylamine, initiated by hydroxyl radicals (.OH) or O-2, shows no difference in the presence or absence of ferredoxin, nor do the decay kinetics of O2. 4. From the above observations and from model reactions (xanthine/xanthine oxidase; iron salts in the presence of H2O2), it is concluded that reduced ferredoxin in the presence of H2O2 forms a Fenton-type oxidizing species for methionine, generating ethylene in the presence of pyridoxal phosphate. 5. Inhibitory effects of both superoxide dismutase and catalase in oxygen-dependent reactions need not necessarily indicate the participation of the 'Haber-Weiss' reaction.

Chloroplasts↗
PubMed1978

Ethane and ethylene formation by mitochondria as indication of aerobic lipid degradation in response to wounding of plant tissue.

During aerobic incubation of potato slices or potato mitochondria at acidic pH, ethane and ethylene in a ratio of approx. 50 : 1 are generated from an endogenous substrate. Both ethane and ethylene production are stimulated by the addition of alpha-linolenic acid. Ethane formation from linolenic acid is a radical mechanism dependent on oxygen and is not significantly influenced by mitochondrial electron transport. Ethane production may represent a sensitive marker for membrane damage.

Chloroplasts↗