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At least 1,279 records · Page 71Linked to original sources
PubMed1975

Physiology of sexual reproduction. I. A histochemical study of the embryo sac development in Zephyranthes rosea and Lagenaria vulgaris.

Using histochemical techniques, changes in the localization of different reserve substances (e.g. pectic compounds, starch, polysaccharides, proteins, nucleic acids, ascorbic acid) and enzymes (Acid phosphatase, alkaline phosphatase, ATP-ase, 5-nucleotidase, esterase, phosphorylase, succinate dehydrogenase, cytochrome oxidase and lipase) have been studied in the young and fertilized ovules of Zephyranthes sp. and Lagenaria sp. etc. Extensive changes in the enzyme activity and reserve substances are demonstrated during megasporogenesis and megagametogenesis and most of the substances exhibited interesting distributional pattern. Similarly, all the enzymes investigated have specific locale of distribution in the tissues which displayed differentiation of embryo sac. The earlier changes observed are in the megaspore which contained many reserve substances (starch; nucleic acids; ascorbic acid; proteins) and enzymes (peroxidase, succinate dehydrogenase, acid phosphatase, alkaline phosphatase and ATP-ase). In the matured embryo sac different cells have differential localization of the substances. Based on histochemical studies, distinct differences are made out between egg and synergids; egg and central cell. In general antipodals have maximum accumulation of physiologically active substances and intense activity of different enzymes. Nucellus cells also stored diverse substances and enzymes especially towards the chalazal end. Pollination stimulated accumulation of several reserve substances and enzymes in the tip of nucellus beak, micropylar zone and these included starch, peroxidase, phosphorylase succinate dehydrogenase, cytochrome oxidase etc.

Blastocyst↗
PubMed1981

A simple routine method for mono and diamine oxidase estimation in human serum.

The advantages and disadvantages of previous methods for the routine estimations of serum mono and diamine oxidase are reviewed. 4-hydroxy-3-methoxy phenyl acetic acid reacts wtih hydrogen peroxide and peroxidase to form an intensely fluorescent substance, and a simple method using this reaction as a basis for the estimation is described. The results are tabulated and discussed.

Adult↗
PubMed1981

[Inhibition and inactivation of horseradish peroxidase by thiourea].

The kinetics of horseradish peroxidase (EC 1.11.1.7)-catalyzed oxidation of o-dianisidine by hydrogen peroxide in the presence of thiourea were studied. At the first, fast step of this process thiourea acts as a competitive reversible inhibitor with respect to o-dianisidine (Ki = 0.22 mM). The formation of a thiourea-peroxidase complex was determined by the increase in the absorbance at A495 and A638 of the enzyme. The dissociation constant for the peroxidase-thiourea complex is equal to 2.0-2.7 mM. Thiourea is not a specific substrate of peroxidase during the oxidation reaction by H2O2, but is an oxidase substrate (although not a very active one) of peroxidase. The irreversible inactivation of the enzyme during its incubation with thiourea was studied. The first-order inactivation rate constant (kin) was shown to increase with a fall in the enzyme concentration. The curve of the dependence of kin on the initial concentration of thiourea shows a maximum at 5-7 mM. The enzyme inactivation is due to its modification by intermediate free radical products of thiourea oxidation. The inhibitors of the free radical reactions (o-dianisidine) protect the enzyme against inactivation. The degree of inactivation depends on concentrations and ratio of thiourea and peroxidase. A possible mechanism of peroxidase interaction with thiourea is discussed.

Horseradish Peroxidase↗
PubMed1988

Genetic differences in enzymes associated with peroxisome proliferation and hydrogen peroxide metabolism in inbred mouse strains.

Enzyme activities relating to H2O2 production (peroxisomal acyl-CoA oxidase) and degradation (catalase and glutathione peroxidase) were measured in the livers of male mice of the inbred strains C57BL/6J (C57) and C3H/HeJ (C3H) and their F1 hybrid, B6C3F1. Groups of the three genotypes were maintained on either a basal diet or one containing 0.1% of the peroxisome-proliferating agent, nafenopin, for six weeks. In both control and nafenopin-exposed groups, the C57 strain displayed higher acyl-CoA oxidase activity levels than the C3H mice, whereas the activity levels of catalase and glutathione peroxidase were not different for the two inbred strains. The groups of similarly fed B6C3F1 hybrids had intermediate values for acyl-CoA oxidase. Several other parameters relating to peroxisome proliferation did not differ among the three genotypes. Acyl-CoA oxidase levels in cultured hepatocytes from C57 mice were greater than those in hepatocytes obtained from the C3H strain during two days in culture and this difference was maintained for 4 days by nafenopin exposure. Acyl-CoA oxidase is central to the hypothetical H2O2 mechanism of peroxisome proliferator-induced hepatocarcinogenesis and, therefore, the genetic difference documented here may lead to a useful approach in testing this hypothesis.

Acyl-CoA Oxidase↗
PubMed1994

Inhibition of thyroid NADPH-oxidase by 2-iodohexadecanal in a cell-free system.

The major nonpolar iodolipid formed in horse thyroid cells has recently been identified as 2-iodohexadecanal (2-IHDA). We have investigated in vitro the effect of 2-IHDA on the NADPH-oxidase, NADPH-cytochrome c reductase, and thyroid peroxidase (TPO) activities of a porcine thyroid plasma membrane preparation. 2-IHDA inhibited NADPH-oxidase activity, with half-inhibition at 3-5 microM, but it had no effect on NADPH-cytochrome c reductase. It inhibited the TPO-catalyzed iodination of protein, but not iodide oxidation. Hexadecanal also inhibited NADPH-oxidase. Inhibition by the non-iodinated lipid aldehydes depended on the length of their aliphatic chain: dodecanal and tridecanal gave maximal inhibition. Free iodide, 2-iodohexadecanol and palmitic acid all had no inhibitory effect. Washing treated membranes showed that the inhibition of NADPH-oxidase by hexadecanal was fully reversible, whereas that of 2-IHDA and other iodinated or brominated alkanals was irreversible. Thus the interaction between some residues of the thyroid NADPH-oxidase and the lipid aldehyde groups was favored or stabilized by the iodine atom. Modification of primary amine and thiol groups of NADPH-oxidase inhibited its activity. These groups could also be the target of lipid aldehydes. We suggest that 2-IHDA, because it inhibits TPO and more profoundly the H2O2-generating system in thyroid plasma membrane, modulates iodide metabolism in the thyrocyte and may mediate the Wolff-Chaikoff effect.

Aldehydes↗
PubMed1999

Hydrogen peroxide production from reactive liposomes encapsulating enzymes.

Reactive cationic and anionic liposomes have been prepared from mixtures of dimyristoylphosphatidylcholine (DMPC) and cholesterol incorporating dimethyldioctadecylammonium bromide and DMPC incorporating phosphatidylinositol, respectively. The liposomes were prepared by the vesicle extrusion technique and had the enzymes glucose oxidase (GO) encapsulated in combination with horseradish peroxidase (HRP) or lactoperoxidase (LPO). The generation of hydrogen peroxide from the liposomes in response to externally added D-glucose substrate was monitored using a Rank electrode system polarised to +650 mV, relative to a standard silver-silver chloride electrode. The effects of encapsulated enzyme concentration, enzyme combinations (GO+HRP, GO+LPO), substrate concentration, electron donor and temperature on the production of hydrogen peroxide have been investigated. The electrode signal (peroxide production) was found to increase linearly with GO incorporation, was reduced on addition of HRP and an electron donor (o-dianisidine) and showed a maximum at the lipid chain-melting temperature from the anionic liposomes containing no cholesterol. To aid interpretation of the results, the permeability of the non-reactive substrate (methyl glucoside) across the bilayer membranes was measured. It was found that the encapsulation of the enzymes effected the permeability coefficients of methyl glucoside, increasing them in the case of anionic liposomes and decreasing them in the case of cationic liposomes. These observations are discussed in terms of enzyme bilayer interactions.

Cholesterol↗
PubMed1998

Enhanced glial cell line-derived neurotrophic factor mRNA expression upon (-)-deprenyl and melatonin treatments.

Glial cell line-derived neurotrophic factor (GDNF) has been shown to be a preferentially selective neurotrophic factor for dopamine (DA) neurons. In the present study, we have examined the distribution of GDNF mRNA expression in several major DA-containing cell body and terminal areas and the regulation of GDNF mRNA expression upon various pharmacological treatments. Results indicated that there is a relatively higher GDNF mRNA level in neurons of the nigrostriatal and mesolimbic dopaminergic pathways. Upon chronic 1-methyl-4-phenyl1,2,3,6-tetrahydropyridine (MPTP) treatment (30 mg/ kg, i.p., for 7 days), DA level was decreased, whereas GDNF mRNA expression was increased in the striatum, suggesting that more GDNF is synthesized and expressed to cope with the neurotoxin insult. Furthermore, among several DA neuron protective and/or therapeutic agents examined, both intrastriatal injections of (-)-deprenyl (1.25 microg and 2.5 microg) and melatonin (30 microg, 60 microg, and 120 microg) significantly enhanced GDNF mRNA expression in the striatum, whereas the same concentrations of (-)-deprenyl did not affect monoamine oxidase B (MAOB) activity, although it increased glutathione peroxidase (GPx) and/or superoxide dismutase (SOD) activities. Similarly, the same concentrations of melatonin did not alter SOD or GPx activities, except that the highest dose of melatonin (120 microg) increased lipid peroxidation in the striatum. Conversely, GM1 ganglioside injection (45 microg) lacked of an effect on GDNF mRNA expression. Together, these results suggest that both (-)-deprenyl and melatonin up-regulate GDNF gene expression at threshold doses lower than that needed for altering MAOB activity and/or the antioxidant enzyme systems, respectively. These results provide new information on the neuroprotective and therapeutic mechanisms of (-)-deprenyl and melatonin on DA neurons.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed2002

Effects of electromagnetic radiation from a cellular telephone on the oxidant and antioxidant levels in rabbits.

The number of reports on the effects induced by electromagnetic radiation (EMR) in various cellular systems is still increasing. Until now no satisfactory mechanism has been proposed to explain the biological effects of this radiation. Oxygen free radicals may play a role in mechanisms of adverse effects of EMR. This study was undertaken to investigate the influence of electromagnetic radiation of a digital GSM mobile telephone (900 MHz) on oxidant and antioxidant levels in rabbits. Adenosine deaminase, xanthine oxidase, catalase, myeloperoxidase, superoxide dismutase (SOD) and glutathione peroxidase activities as well as nitric oxide (NO) and malondialdehyde levels were measured in sera and brains of EMR-exposed and sham-exposed rabbits. Serum SOD activity increased, and serum NO levels decreased in EMR-exposed animals compared to the sham group. Other parameters were not changed in either group. This finding may indicate the possible role of increased oxidative stress in the pathophysiology of adverse effect of EMR. Decreased NO levels may also suggest a probable role of NO in the adverse effect.

Adenosine Deaminase↗
PubMedDate not supplied

Ischemia and reperfusion injury in isolated rat heart: effect of reperfusion duration on xanthine oxidase, lipid peroxidation, and enzyme antioxidant systems in myocardium.

The aim of this work was to assess the catalytic activity of xanthine oxidase, the level of lipid peroxides and enzymic antioxidant systems in isolated rat heart muscle subjected to a globally partial ischemia followed by varying durations of reperfusion. After 40 min of globally partial ischemia (residual perfusion flow rate: 0.1 ml/min), four different durations of reperfusion were investigated (0, 20, 40, and 60 min). After each experimental ischemia/reperfusion sequence, the heart was frozen in liquid nitrogen. Lipid peroxides were assayed in the cardiac homogenate and the catalytic activity of xanthine oxidase and enzymic antioxidant systems (glutathione peroxidase, superoxide dismutase and catalase) were determined in the centrifuged supernatant. In the different experimental protocols studied in this work, there was no significant increase in the activity of cardiac xanthine oxidase or in the level of lipid peroxides when compared to the non reperfused or to the continuously perfused hearts. Indeed, enzymic antioxidant systems were also not significantly modified in the different periods of reperfusion when compared to control hearts (continuously perfused hearts). These results suggest that xanthine oxidase is apparently not a major source of free radicals in the course of an ischemia-reperfusion sequence in heart muscle, in particular, if we consider the early phases of reperfusion. The process of lipid peroxidation, assessed by assaying thiobarbituric acid reactants, is not a predominant phenomenon of reperfusion-induced injury, at least in the experimental model used here. However, enzymic antioxidant systems investigated in this study do not seem modified. This could mean that the small quantity of oxygen free radicals produced does not overwhelm the enzymic antioxidant systems of myocardium which is in agreement with peroxidatized lipid results.

Animals↗
PubMed2001

Nonionic micellar liquid chromatography coupled to immobilized enzyme reactors.

Immobilized enzyme reactors are used as post-column reactors to modify the detectability of analytes. An immobilized amino acid oxidase reactor was prepared and coupled to an immobilized peroxidase reactor to detect low level of amino acids by fluorescence of the homovanilic dimer produced. A cholesterol oxidase reactor was prepared to detect cholesterol and metabolites by 241 nm UV absorbance of the enone produced. The preparation of the porous glass beads with the immobilized enzymes is described. Micellar liquid chromatography is used with non-ionic micellar phases to separate the amino acids or cholesterol derivatives. It is demonstrated that the non ionic Brij 35 micellar phases are very gentle for the enzyme activity allowing the reactor activity to remain at a higher level and for a much longer time than with hydro-organic classical chromatographic mobile phases or aqueous buffers. The coupling of nonionic micellar phases with enzymatic detection gave limits of detection of 32 pmol (4.8 ng injected) of methionine and 50 pmol (19 ng injected) of 20alpha-hydroxy cholesterol. The immobilized enzyme reactors could be used continuously for a week without losing their activity. It is shown that the low efficiency obtained with micellar liquid chromatography is compensated by the possibility offered by the technique to easily adjust selectivity.

1-Propanol↗
PubMed1994

A stable water-soluble tetramethylbenzidine-2-hydroxypropyl-beta-cyclodextrin inclusion complex and its applications in enzyme assays.

3,3',5,5'-Tetramethylbenzidine (TMB), a hydrophobic and noncarcinogenic chromogen with a high absorption coefficient widely used in solid-phase assays involving labeled horseradish peroxidase was rendered soluble (up to 40 mM) and more stable for at least 2 months at 22-24 degrees C by forming a water-soluble inclusion complex with 2-hydroxypropyl-beta-cyclodextrin (hp-beta-CyD). Cyclic voltammetry and absorbency measurement were employed to characterize the TMB-hp-beta-CyD complex. Well-defined cyclic voltammograms of TMB exhibited two oxidation waves which merged into a single wave with increasing hp-beta-CyD concentrations. Cyclic voltammetry was then used to examine the effect of complexation with hp-beta-CyD on the oxidation potential of TMB and provided evidence of a 1:1 complex between TMB and the cyclodextrin molecule with a formation constant of 1.6 M-1. Enzyme assays for D-glucose, lactate, and glutamate were performed by coupling the TMB-hp-beta-CyD/horseradish peroxidase system to the respective oxidase enzymes with the formation of either a blue (absorption coefficient of 35,800 M-1 cm-1 at 650 nm) or a yellow color (absorption coefficient of 67,300 M-1 cm-1 at 450 nm) as an indication of the metabolite concentration. These assays possessed a sensitivity limit below 10 microM and the results obtained were in excellent agreement with standard enzymatic assays when tested in various food and clinical samples.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed1992

Simultaneous visualization of cortical barrels and horseradish peroxidase-injected layer 5b vibrissa neurones in the rat.

1. Using diaminobenzidine (DAB) as a chromagen, horseradish peroxidase-injected neurones and cytochrome oxidase-stained barrels were visualized simultaneously in the rat vibrissa cortex. Neurones were initially tested during extracellular recording for responses to whisker deflections. This was followed by intracellular injection of the soma with horseradish peroxidase (HRP) and histological processing to visualize the HRP-stained neurone in an incubation solution which contained, in addition to DAB, cytochrome C for cytochrome oxidase (CO) reaction of the barrels. 2. Recording and intracellular staining were made in layer 5b under urethane anaesthesia. CO-stained barrels were observed in layer 4. Physiologically and morphologically characterized neurones were mostly large pyramidal neurones that responded to more than one whisker and displayed transient-type responses. 3. In tangential sections, the apical dendrite of the HRP-filled neurone was followed from the soma level upward as it ascended through the barrelfield in layer 4. The cross-section of the apical dendrite was found in the periphery of the CO-stained barrel. Using the apical dendrite as a guide, the basal dendritic field of the layer 5b pyramidal neurone was aligned on the pattern of layer 4 barrels. The soma was seen to project basal dendrites in all directions, involving one or two neighbouring barrels/columns. 4. In sixteen neurones examined in tangential sections, a complete spatial tuning map constructed by measuring sensitivity of the neurone to different whiskers could be compared to the basal dendritic field in relation to the pattern of overlying layer 4 barrels. The mean receptive field size in terms of the number of effective whiskers was 5.8 whereas the mean dendritic field size in terms of the number of barrels/columns involved was 2.2. In addition to the well-documented role of intracortical connectivity in elaboration of multi-whisker receptor fields in the cortical neurones, the role played by direct inputs from multi-whisker thalamic ventrobasal neurones was discussed.

3,3'-Diaminobenzidine↗
PubMed1995

Studies on hepatic xenobiotic-metabolizing enzymes in rats treated with insecticide deltamethrin.

The effects of the synthetic dibromo-pyrethroid insecticide deltamethrin on some hepatic phase I and II enzyme activities were studied in rat liver. The animals were treated with daily doses of 5 and 10 mg/kg of both pure insecticide or its commercial formulation (Decis), administered i.p. in corn oil for 7 days. The following enzyme activities were studied: NADPH-cytochrome-P450 reductase, aryl-hydrocarbon hydroxylase, aminopyrine N-demethylase, glutamyl cysteine synthetase, glutathione S-transferase, glutathione peroxidase, peroxisomal acyl-CoA oxidase, catalase, and urate oxidase. Both deltamethrin and its commercial formulation were effective in modifying the activities of several of these hepatic xenobiotic-metabolizing enzymes. However, some differences in enzyme modifications were found between treatment with pure or commercial deltamethrin, the latter being more active. This effect could be ascribed to additives, solvents, and chemical intermediates present in the Decis formulation. These results suggest that exposure to this deltamethrin commercial formulation could be more dangerous than exposure to deltamethrin alone, both in terms of its hepatotoxicity and/or alterations in the hepatic biotransformation of other occupational/environmental xenobiotics.

Aminopyrine N-Demethylase↗
PubMed2003

Early oxidative stress in the diabetic kidney: effect of DL-alpha-lipoic acid.

Oxidative stress is implicated in the pathogenesis of diabetic nephropathy. The attempts to identify early markers of diabetes-induced renal oxidative injury resulted in contradictory findings. We characterized early oxidative stress in renal cortex of diabetic rats, and evaluated whether it can be prevented by the potent antioxidant, DL-alpha-lipoic acid. The experiments were performed on control rats and streptozotocin-diabetic rats treated with/without DL-alpha-lipoic acid (100 mg/kg i.p., for 3 weeks from induction of diabetes). Malondialdehyde plus 4-hydroxyalkenal concentration was increased in diabetic rats vs. controls (p <.01) and this increase was partially prevented by DL-alpha-lipoic acid. F(2) isoprostane concentrations (measured by GCMS) expressed per either mg protein or arachidonic acid content were not different in control and diabetic rats but were decreased several-fold with DL-alpha-lipoic acid treatment. Both GSH and ascorbate (AA) levels were decreased and GSSG/GSH and dehydroascorbate/AA ratios increased in diabetic rats vs. controls (p <.01 for all comparisons), and these changes were completely or partially (AA) prevented by DL-alpha-lipoic acid. Superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione transferase, and NADH oxidase, but not catalase, were upregulated in diabetic rats vs. controls, and these activities, except glutathione peroxidase, were decreased by DL-alpha-lipoic acid. In conclusion, enhanced oxidative stress is present in rat renal cortex in early diabetes, and is prevented by DL-alpha-lipoic acid.

Albuminuria↗