Search results for "Enzyme Assay"
showing 10 items of 155 documents
Lysosomal alterations in heart and liver of mice treated with doxorubicin.
1985
This study was carried out to evaluate the influence of long-term treatment with doxorubicin (DXR) (4mg/kg IV for 5 weeks) on heart and liver lysosomes of mice. We evaluated the variations in both total and "sedimentable" enzyme activity of cathepsin D, which is the major endopeptidase of myocites and probably involved in physiologic and pathologic degradation of actomyosin and mitochondria, and that of acid phosphatase, which is more prominent in interstitial cells. Our results show that marked changes occur in both total and sedimentable enzyme activity of cathepsin D in the heart of treated animals and to a lesser extent in the liver. In contrast, no modification of either total or sedim…
Inhibition of the hydrolytic and transpeptidase activities of rat kidney gamma-glutamyl transpeptidase by specific monoclonal antibodies
1999
Monoclonal antibodies (mAb) against the native form of rat kidney gamma-glutamyl transpeptidase (GGT) were isolated by screening hybridomas with rat kidney brush-border membrane vesicles. They were directed against protein rather than sugar epitopes in that each recognized all GGT isoforms. All of them inhibited partially the enzyme activity of GGT. They were specific in that they inhibited the rat enzyme, but not the mouse or human enzyme. Kinetic analyses were carried out with free GGT and GGT-mAb complexes with d-gamma-glutamyl-p-nitroanilide in the presence or absence of maleate, or in the presence or absence of alanine, cysteine, cystine or glycylglycine as gamma-glutamyl acceptors. mA…
Amperometric detection of extended-spectrum β-lactamase activity : application to the characterization of resistant E.coli strains
2015
EA MERS CT3; International audience; The amperometric detection of extended-spectrum β-lactamase (ESBL) with carbon screen-printed sensors was investigated in the presence of the Nitrocefin, a commercially-available β-lactamase chromogenic cephalosporin substrate. Using an ESBL isolated from a clinical sample, it was shown for the first time that the intensity of a specific anodic pic current (EP = [similar]+0.3 V vs. Ag/AgCl) resulting from the catalytic hydrolysis of the β-lactam ring was proportional to the amount of ESBL. The proof-of-principle of a novel susceptibility assay for the rapid and accurate identification of ESBL- producing bacteria was then demonstrated. The detection schem…
Transglutaminase activity is involved in Saccharomyces cerevisiae wall construction
2002
Transglutaminase activity, which forms the interpeptidic cross-link N(epsilon)-(gamma-glutamyl)-lysine, was demonstrated in cell-free extracts of Saccharomyces cerevisiae by incorporation of [(14)C]lysine into an exogenous acceptor, N,N'-dimethylcasein. Higher levels of the activity were present in the cell wall, which also contained endogenous acceptors. The enzyme activity in the wall was inhibited by cystamine, a known inhibitor of transglutaminase, and by EDTA, indicating a cation-dependent activity. After the endogenous wall acceptors were labelled radioactively by transglutaminase, extraction with SDS solubilized about 50% of the total radioactivity, while Zymolyase and chitinase each…
The selection of serum-independent PC12 cells for a more-reliable manganese cytotoxicity test.
2007
A major issue concerning the protocols of heavy metal cytotoxicity tests with PC12 cells was the hypothesis that serum in the culture medium might sequester the metal, thus altering the results obtained. However, serum withdrawal impairs the viability of PC12 cells themselves, thus impeding cytotoxicity testing in the absence of serum. In this study, we repeatedly selected undifferentiated, totally non-adherent PC12 cells in Petri dishes. Surprisingly, we discovered that these cells could survive and proliferate in serum-free medium. Moreover, features such as NGF-responsiveness, resazurin reduction potential, doubling rate, protein content, and basal caspase-3 enzyme activity, were equiva…
Estradiol decreases xanthine dehydrogenase enzyme activity and protein expression innon-tumorigenicand malignant human mammary epithelial cells
2009
The retinoic acid deficiency in breast tumour epithelial cells has been ascribed to an insufficient expression of either the enzyme(s) involved in its biosynthesis or the cellular retinol binding protein (CRBP) or both. In an attempt to define the mechanisms underpinning retinoic acid deficiency in these cell model systems, we have investigated the potential regulatory effect of oestrogen (17β-estradiol) on one key player in retinoic acid biosynthesis, the xanthine dehydrogenase (XDH). This enzyme is consistently expressed and very active in non-malignant human mammary epithelial cells (HMEC), as opposed to tumour MDA-MB231 and MCF7 cells. In these latter two cell lines, as opposed to HMEC …
Effects of SO2 fumigations on photosynthetic CO2 gas exchange, chlorophyll a fluorescence emission and antioxidant enzymes in the lichens Evernia pru…
1999
The effects of elevated gaseous SO2 concentrations in the lichens Evernia prunastri (L.) Ach. and Ramalina farinacea (L.) Ach. were investigated by means of gas exchange, modulated chlorophyll fluorescence analysis and antioxidant enzyme assays. The response to SO2 of the studied species differed markedly. Net photosynthetic rates were more adversely affected in E. prunastri than in R. farinacea. In addition, processes dependent on thylakoid membrane integrity such as PSII-mediated electron flow and nonphotochemical quenching were reduced to a greater extent by exposure to SO2 in E. prunastri. Moreover, the ability to reoxidize the quinone pool was lower in this species. Finally, the activi…
Mammalian glial cells in culture synthesize acetylcholine.
1997
In the present study we demonstrate that acetylcholine is synthesized by cultured mammalian glial cells identified by cell-type specific markers. Primary cultures of rat brain astrocytes or microglia contained 2.0 and 1.6 pmol acetylcholine/10(6) cells on average respectively. Astrocyte cultures established from neonatal mouse brain contained even more acetylcholine (about 80 pmol acetylcholine/10(6) cells). Primary cultures of rat brain astrocytes showed choline acetyltransferase (ChAT) enzyme activity of 3 nmol/mg protein/h; ChAT activity was blocked by 10 microM bromoacetylcholine. In conclusion, these data demonstrate the synthesis of the "neurotransmitter" acetylcholine in cultured gli…
Use of sonication for measuring acid phosphatase activity in soil
2000
Extracellular enzymes in soil often occur in immobilised forms, a state that may alter their interactions with substrates in comparison with enzymes in the solution phase. Sonication was evaluated for its usefulness in studying immobilised acid phosphatase by dispersing soil aggregates. Factors affecting soil dispersion during ultrasound application were soil extraction ratio, total applied energy and power output ml−1 of sonicated soil slurry. For the clay loam soil used, optimal values for these variables were, respectively, 1:6 (w/v) and, at least, 1800 J ml−1 and 15 W ml−1. At the optimal sonication conditions for soil dispersion a substantial increase in phosphatase activity (up to 156…
Characterization of an ethanol-tolerant 1,4-β-xylosidase produced byPichia membranifaciens
2012
Aims: The purification and biochemical properties of the 1,4-β-xylosidase of an oenological yeast were investigated. Methods and Results: An ethanol-tolerant 1,4-β-xylosidase was purified from cultures of a strain of Pichia membranifaciens grown on xylan at 28°C. The enzyme was purified by sequential chromatography on DEAE cellulose and Sephadex G-100. The relative molecular mass of the enzyme was determined to be 50 kDa by SDS-PAGE. The activity of 1,4-β-xylosidase was optimum at pH 6·0 and at 35°C. The activity had a Km of 0·48 ± 0·06 mmol l−1 and a Vmax of 7·4 ± 0·1 μmol min−1 mg−1 protein for p-nitrophenyl-β-d-xylopyranoside. Conclusions: The enzyme characteristics (pH and thermal st…