Platelet aggregation by isolated and aggregated human IgG.
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Isolated myeloma proteins of the four human IgG subclasses, aggregated by heat of bis-diazotized benzidine (BDB), induced aggregation of human platelets (Pl.A.) demonstrable by the sedimentation pattern test. With this sensitive technique, approximately 0-1 mug/ml of BDB-aggregated IgG1 and IgG3 could be detected whereas 200 to 1000 times higher concentrations of IgG2 and IgG4 were required for the Pl.A. reaction. The reaction pattern showed similarities with complement fixation tests. (+info)
Functional modulation of a peroxygenase cytochrome P450: novel insight into the mechanisms of peroxygenase and peroxidase enzymes.
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Cytochrome P450(BSbeta) is a peroxygenase that catalyzes the alpha- or beta-hydroxylation of myristic acid by utilizing H(2)O(2). The wild-type enzyme not only hydroxylated myristic acid, but oxidized 3,5,3',5'-tetramethylbenzidine (TMB), a peroxidase substrate, in a myristic acid-dependent reaction. Study of inhibition of hydroxylation of myristic acid by TMB indicates these two substrates compete for the same highly reactive intermediate during the course of their respective reactions. When deuterated myristic acid was used as a substrate to decrease hydroxylation activity, the rate of TMB oxidation increased. This increased rate of TMB oxidation was greatly enhanced when the R242K mutant enzyme bound with deuterated myristic acid was used. These results suggest that there are critical structural elements at the distal active site which determine whether this enzyme acts as a peroxygenase or a peroxidase. (+info)
Assessment of genotoxicity of benzidine and its structural analogues to human lymphocytes using comet assay.
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Benzidine (BZ) and its six structural analogues (2-aminobiphenyl [2-ABP], 4-aminobiphenyl [4-ABP], 3,3'-diaminobenzidine [DABZ], 3,3'-dichlorobenzidine [DCBZ] 3,3'-dimethoxybenzidine [DEBZ], and 3,3'-dimthylbenzidine [DMBZ]) were examined for DNA damage in human lymphocytes using the alkaline comet assay. All the tested compounds showed a distinct disparity in their respective DNA-damaging capacities with an order of DABZ > BZ > DCBZ > 2-ABP > DEBZ > 4-ABP > DMBZ when lymphocytes were exposed to these chemicals for 2 h. Results show that the DNA-damaging effects of these compounds had no bearing on some physicochemical parameters including oxidation potentials, the energy differences between the lowest unoccupied molecular orbital and the highest occupied molecular orbital, ionization potentials, dipole moment, and relative partition coefficient. On the other hand, the free radical scavengers, including catalase, SOD, BHT, EDTA, and histidine exerted varying degrees of inhibitory effects on the DNA damage caused by benzidine. This suggests that genotoxicity in lymphocytes caused by benzidine proceeded via a reactive oxygen species (ROS)-mediated mechanism. (+info)
A method for coupling protein antigens to erythrocytes. I. Description of method.
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A technique has been described whereby tuberculin PPD is coupled, via tetrazotized benzidne, onto the surfaces of formalinized red blood cells. A stable antigen preparation is thereby obtained, which may be stored at -40 degrees C. The purpose of the present method is to facilitate the study of antibody to tuberculoprotein. (+info)
A method for coupling protein antigens to erythrocytes. II. Use of the method in the diagnosis of tuberculosis.
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A serological technique, using formalinized red cells coupled to tuberculin PPD as antigen, has been assayed in a trial series of 124 tuberculous and 139 non-tuberculous patients. The stability of the antigen preparation, and the omission of an adsorption procedure for the removal of isoagglutinins facilitated the performance of the test. The results indicate that the technique warrants further trial as a diagnostic criterion of infection tuberculosis. (+info)
Isolation of haemin-binding proteins of Neisseria gonorrhoeae.
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Although Neisseria gonorrhoeae can use haem as the sole exogenous iron source for growth in vitro, the mechanism of haem-iron uptake in the gonococcus is unknown. Two haemin-binding proteins (HmBPs) of 97 and 44 Kda were isolated by batch ligand affinity-chromatography from whole cells or total membranes of gonococci grown under iron-limited conditions but not from those grown under iron-sufficient conditions. Competition binding experiments indicated that the haemin-protein interaction was specific; only haemin or haem-containing proteins, such as human haemoglobin or equine cytochrome c111, but not protoporphyrin IX, iron loaded human transferrin or lactoferrin, could abrogate binding. Identical HmBPs were isolated from three other clinical gonococcal strains, suggesting that these may be interstrain structural and functional homogeneity amongst these polypeptides. (+info)
Biomarkers in occupational cancer epidemiology: considerations in study design.
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Epidemiologic studies of occupational groups have been central to the identification of human carcinogens. The incorporation of a biochemical component into occupational studies of cancer can expand the possibilities for identifying human carcinogens and for understanding the disease process. Two epidemiologic studies of occupation and cancer which include evaluation of biomarkers are described. The association of acetylator phenotype with bladder cancer risk was studied in benzidine-exposed workers. The association of benzene-related leukopenia with leukemia is being studied in benzene-exposed workers. These investigations illustrate issues in the use of biomarkers in epidemiologic studies of cancer risk. Such studies require the identification and characterization of the population at risk. Disease susceptibility factors are amenable for inclusion in these studies and can be statistically modeled as exposure-effect modifiers. Biomarkers of exposure are mainly of importance in short-term longitudinal and cross-sectional studies of exposure and intermediate outcomes and for validation of other data sources. Several sources of error can affect the results of molecular epidemiologic studies. Aside from minimizing laboratory error, consideration must be given in the design and execution of these studies to potential problems in subject selection and field collection of biologic samples and other relevant data. (+info)
Gastrointestinal blood loss after non-steroidal anti-inflammatory drugs. Measurement by selective determination of faecal porphyrins.
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1. A method for the detection of gastrointestinal blood loss based upon the selective measurement of faecal porphyrins was tested in two studies in healthy volunteers. 2. In the first study subjects (n = 6) received intragastric autologous blood (saline, 2 and 6 ml as a single dose) resulting in a dose dependent increase in faecal porphyrins. 3. In a subsequent placebo controlled cross over study in 12 subjects acetylsalicylic acid (ASA), nabumetone (a new NSAID) or placebo were administered for 5 days with a washout period of 9 days. They were no dietary restrictions. 4. All faeces were collected during the treatment period and both the full faecal homogenate and a random faecal sample were analyzed for deutero- and pemptoporphyrin content by h.p.l.c. Additionally a benzidine reaction was performed. 5. There was a highly significant correlation (r = 0.95) between the values obtained from random samples and the full homogenate. ASA increased the faecal porphyrin excretion (P less than 0.001) compared with placebo in contrast to nabumetone. Complaints of dyspepsia were most common after ASA. 6. Measurement of faecal porphyrins is useful for monitoring NSAID induced upper gastrointestinal blood loss and lacks some of the practical constraints of other methods. (+info)