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At least 19 recordsLinked to original sources
PubMed1978

New GLC analysis of urushiol congeners in different plant parts of poison ivy, Toxicodendron radicans.

Methods are presented for the direct GLC analysis of the catechol C15 alkenyl side-chain congeners contained in the urushiol fraction of poison ivy (Toxicodendron radicans) and the C17 homologs of poison oak (Toxicodendron diversilobum). A number of liquid phases were investigated and demonstrated varying degrees of separation. The methods developed were applied to the analysis of the urushiol fractions obtained from different plant parts of poison ivy. The effects of extraction before and after drying demonstrated tht a larger percentage of urushiol was obtained when the fresh plant material was extracted with ethanol.

Catechols↗
PubMed1979

Studies on poison ivy. In vitro lymphocyte transformation by urushiol-protein conjugates.

The isolation and purification of poison ivy urushiol is described. The preparation of urushiol-ski protein and urushiol human serum albumin is also described. Lymphocytes from eleven donor naturally sensitized to poison ivy and from four non-sensitive individuals have been cultured for 5 days in the presence of urushiol-carrier conjugates. Lymphocytes from seven of the eleven sensitive donors responded with a stimulation index greater than 3.0 to urushiol-albumin conjugate. When urushiol-skin protein conjugate was used as a stimulant, lymphocytes from only three of the eleven sensitive donors responded. The results suggest that urushiol-protein conjugates can stimulate sensitive lymphocytes in vitro, although a response is not observed in every individual naturally sensitized to poison ivy.

Adult↗
PubMed1975

Renal lesions accompanying poison oak dermatitis.

Renal damage associated with poison oak dermatitis is extremely rare in humans after exposure to urushiol antigen. Three renal lesions have been described: proliferative glomerulonephritis, arteritis, and membranous nephropathy. The present study reports on three patients who developed nephropathy after exposure to poison oak. One patient was studied by renal biopsy (including electron microscopy and immunofluorescence techniques) and another by autopsy findings. One of these patients had a typical membranous nephropathy, the other, proliferative glomerulonephritis with necrotizing arteritis and glomerulitis. In the patient with membranous nephropathy antibody to urushiol was discovered by passive cutaneous anaphylaxis in the guinea pig.

Animals↗
PubMed1976

Assay of topical corticosteroids. Efficacy of suppression of experimental Rhus dermatitis in humans.

Rhus dermatitis, experimentally induced in humans, was used as a model for determining the efficacy of various proprietary topical steroids. One-centimeter squares of vesicular dermatitis were induced by patch application of Rhus oleoresin. The steroids were then applied without occlusion once daily for four days, with readings of the therapeutic effect taken on the fifth day. Only potent steroids provided unequivocal suppression in this severe test. The rank order of efficacy corresponded to clinical experience. Cream and ointment formulations of the same steroid at the same strength did not differ. High strength preparations were more effective than regular strengths. Relief of pruritus was an important early effect of efficaceous steroids.

Administration, Topical↗
PubMed1976

Oxidation and reduction of copper ions in catalytic reactions of Rhus laccase.

1) It was demonstrated by colorimetric as well as EPR measurements that the native (aerobic, resting state) Rhus vernicifera laccase contains both Cu2+ and Cu+ (total Cu content was 4.0 gram atoms/mole). The ratio of Cu2+ to total Cu in laccase varied (42-90%) in samples of latex collected from various districts. The absorption maximum at 615 nm was proportional to the content of total Cu in the enzyme sample. Laccase activity was found to almost parallel the content of the Cu2+ form. The oxidized minus reduced difference absorbance of the enzyme at 330 nm shoulder was proportional to the amount of Cu2+. 2) Steady state level of oxidation of laccase copper during the laccase copper catalytic action, the rates of reduction by substrates and the oxidation by O2 were determined by following absorbance changes at 615 and 330 nm by the stopped flow method. 3) All the results from titrimetric and kinetic experiments were consistent with the laccase model previously proposed by Makino and Ogura in which a laccase molecule contains 1 Cu(615) and 3 Cu(330). Our expanded model states that a laccase sample originally contains active as well as inactive enzymes. In the active enzyme, Cu ions are reactive to O2 but in the inactive enzyme, Cu can be oxidized only by oxidizing agents such as H2O2 or ferricyanide, or by a slow intermolecular electron transfer from Cu(615) to the active enzyme. In both species of enzyme rapid reduction of Cu2+ ions by substrate takes place. In comparative studies of the reactivities of Cu ions in various copper proteins, we would like to suggest that oxidatic activity of a copper protein is due to the Cu+ form of the enzyme ions with O2.

Anaerobiosis↗
PubMed1977

[Therapy of recurrent herpes simplex and its surveillance by MIF determination: with levamisole, BCG, urushiol and herpes antigen vaccine (author's transl)].

Thirty patients with recurrent herpes simplex and 6 controls were included in our study. Before initiation of treatment, during therapy with Levamisole, BCG, poison ivy and herpes antigen vaccine and, thereafter, MIF-determinations were performed. The latter test proved to be a useful parameter in evaluating the sensitivity against herpes infection, (and subsequent recurrent manifestations), and effect of therapy. Treatment with Levamisole, BCG and herpes antigen vaccine was successful. MIF-inhibition values paralleled the therapeutic effect in the Levamisole- and herpes antigen vaccine treated group, not however, in the BCG-treated patients

Antigens, Viral↗
PubMed1976

Kinetic studies of Rhus vernicifera laccase. Role of the metal centers in electron transfer.

The reactions of Rhus vernicifera (monophenol,dihydroxyphenylalanine: oxygen oxidoreductase, EC 1.14.18.1) with the reducing substrates hydroquinone and ascorbic acid have been investigated with the stopped-flow technique. Rhus laccase appears to be present in two molecular forms with a pH-sensitive equilibrium constant regulating the relative concentrations of each species. A model for the reaction of Rhus laccase with reducing substrates has been formulated. The model is similar to one formulated earlier for the anaerobic reduction of laccase from Polyporus versicolor (Andréasson, L.-E., Malström, B.G., Strömberg, C. and Vänngård, T. (1973) Eur. J. Biochem. 34, 434-439) and accounts for the reduction also of this enzyme. The essentials of the model are as follows: Electrons are taken up from reductants one at a time. The type 1 Cu2+ has a central role in mediating the transfer of at least one of the electrons needed for the reduction of the co-operative two-electron acceptor. Intramolecular reactions determine the concentrations of two molecular forms of the enzyme and influence the rate of reduction of the two-electron acceptor. The model, which has been used for successful simulations of the anaerobic reduction of Rhus laccase, is capable of explaining the reduction of laccases also in the presence of the inhibitor F-. In addition, the model gives an explanation of the behaviour of the laccases when reducing substrates and O2 are simultaneously present and is consistent with earlier observations of the post-steady-state reduction of the type 1 Cu2+ and the two-electron accetor (Holwerda, R.A. and Gray, H.B. (1974) J. Am. Chem. Soc. 96, 6008-6022).

Anaerobiosis↗
PubMed1976

Kinetic studies of Rhus vernicifera laccase. Evidence for multi-electron transfer and an oxygen intermediate in the reoxidation reaction.

1. The reoxidation of reduced Rhus vernicifera laccase (monophenol,dihydroxyphenylalanine:oxygen oxidoreductase, EC 1.14.18.1) by molecular oxygen has been studied by optical absorption and EPR methods. 2. The reoxidation by oxygen of the type 1 Cu+ and the two-electron acceptor is characterized by a second-order rate constant of about 5-10(6) M-1-s-1. 3. The appearance of an optical intermediate (with an absorbance maximum around 360 nm) parallels the reoxidation of type 1 Cu+ and the two-electron acceptor. It disappears in a first-order reaction with a half-time of 20 s. A similar intermediate is formed during normal turnover. 4. The type 2 Cu+ appears to be reoxidized in an intramolecular reaction with a half-time of about 20 s, suggesting a correlation between the reoxidation of this site and the disappearance of the optical intermediate. 5. The results suggest that three electrons are rapidly transferred to oxygen leading to the formation of an enzyme-bound oxygen intermediate.

Catechol Oxidase↗
PubMed1978

Steady-state kinetics of laccasse from Rhus vernicifera.

The steady-state kinetics of laccasse (monophenol, dihydroxyphenylalanine: oxygen oxidoreductase, EC 1.14.18.1) from the lacquer tree Rhus vernicifera is investigated using the respirograph method to produce Lineweaver-Burk plots of oxygen consumption rate against oxygen concentration. A ping-pong mechanisms is established. The kinetic constants obtained according to the model is in close agreement with the corresponding values obtained from earlier studies on the transient reactions between the reduced enzyme and oxygen (Andréasson, L.E., Brändén, R. and Reinhammar, B. (1976) Biochim. Biophys. Acta 438, 370--379) and between the oxidized enzyme and reducing substrates (Andréasson, L.E. and Reinhammar, B. (1976) Biochim. Biophys. Acta 445, 579--597).

Catechol Oxidase↗
PubMed1979

The mechanism of electron transfer in laccase-catalysed reactions.

1. The reaction of the electron acceptors in Rhus vernicifera laccase (monophenol, dihydroxyphenylalanine:oxygen oxidoreductase, EC 1.14.18.1) have been studied with stopped-flow and rapid-freeze EPR techniques. The studies have been directed mainly towards elucidation of the role of the type 2Cu2+ as a possible pH-sensitve regulator of electron transfer. 2. Anaerobic reduction experiments with Rhus laccase indicate that the type 1 and 2 sites contribute one electron each to the reduction of the two-electron-accepting type 3 site. There is also evidence that the reduction of the type 1 Cu2+ triggers the reduction of the type 2 Cu2+. 3. Only at pH values at which the reduction of the two-electron acceptor is limited by a slow intramolecular reaction can an OH- be displaced from the type 2 Cu2+ by the inhibitor F-. 4. A model describing the role of the electron-accepting sites in catalysis is formulated.

Anaerobiosis↗
PubMed1979

Substituent effects on the electron transfer reactivity of hydroquinones with laccase blue copper.

Stopped-flow kinetic studies of the anaerobic reduction of Rhus vernicifera laccase (monophenol, dihydroxyphenylalanine:oxygen oxidoreductase, EC 1.14.18.1) type 1 copper by 25 mono- and disubstituted hydroquinones (H2Q-X) have been performed at 25 degrees C and pH 7.0 in 0.5 M phosphate. All of the data are compatible with a mechanism involving rapid enzyme-substrate complex formation followed by rate-limiting intra-complex electron transfer. ES complex formation constants (Qp) for many substrates are strikingly insensitive to the electronic characteristics of the substituent X, falling within the range 5--50 M-1. It is shown that this result may be accounted for if only the singly ionized forms of the substituted hydroquinones are bound by the enzyme. All of the substrates exhibiting exceptionally high Qp values (greater than 50 M-1) have X groups capable of functioning as ligands; substituents with lone pairs of electrons may facilitate enzyme-substrate complex formation by enabling hydroquinone to function as a bidentate bridging ligand between the type 2 and type 3 copper sites. Intra-complex electron transfer rate constants for most substrates are remarkably insensitive to the thermodynamic driving force for the oxidation of H2Q-X to the corresponding semiquinone, the average value for ten substrates being 30 +/- 10 s-1. The electron transfer reactivity of polyphenols with laccase blue copper therefore appears to be controlled largely by protein-dependent activation requirements rather than by the oxidizability of the substrate.

Binding Sites↗