ISSN:0098-4108    

DOI:10.1080/15287399309531782

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In this article, we briefly highlight the use of capillary electrophoresis for sampling, manipulating, and separating extremely small sample sizes. The extraordinary sensitivity that can be obtained by combined capillary electrophoresis‐mass spectrometry is then demonstrated using recent results. We briefly describe the ability to detect noncovalently associated complexes (e.g., double‐stranded DNA) by electrospray ionization‐mass spectrometry, and conclude with recent results that show the potential for using high‐resolution Fourier transform ion cyclotron resonance (FT‐ICR) mass spectrometry for characterization of biomolecules.

ISSN:0098-4108    

DOI:10.1080/15287399309531783

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

ISSN:0098-4108    

DOI:10.1080/15287399309531784

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The most common procedure to identify hemoglobin adducts has been to cleave the adducts from the protein and characterize the adducting species, by, for example, derivatization and gas chromatography/mass spectrometry. To extend these approaches we used electrospray ionization mass spectrometry (ESI‐MS) to characterize adducted hemoglobin. For this we incubated [14C]acrylamide with the purified human hemoglobin (type A0) under conditions that yielded high adduct levels. When the hemoglobin was separated by reversed‐phase high‐performance liquid chromatography (HPLO, 65% of the radioactivity copurified with the β‐subunit. Three adducted species were prominent in the ESI mass spectrum of the intact β‐subunit, indicating acrylamide adduction (i.e., mass increase of 71 Da) and two additional unidentified moieties with mass increments of 102 and 135 Da. Endoproteinase Glu‐C digestion of the adducted β‐subunit resulted in a peptide mixture that, upon reversed‐phase HPLC separation, provided several radiolabeled peptides.

ISSN:0098-4108    

DOI:10.1080/15287399309531785

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Mammalian organisms possess a variety of enzymes that catalyze the biotransformation of numerous chemicals with diverse structure. The gene superfamily comprising the cytochrome P‐450 monooxygenases (P‐450) are key participants in these reactions, and certain P‐450 genes are highly inducible upon xenobiotic exposure. Many of the standard techniques used in the study of these systems rely on the disruption of tissues and cells, together with the preparation of subcellular particles. We have adopted a sensitive new technique, scanning laser cytometry, to monitor P‐450‐mediated O‐dealkylation activities directly in cultured cells. Metabolism in single cells was quantified by fluorescence detection of resorufin, the P‐450‐mediated O‐dealkylation product of alkoxyresorufin ether substrate probes. Functional activities associated with P‐4501A1 and NADPH DT‐diaphorase were compared among a human hepatoma (Hep G2) cell line and cells derived from mouse (Hepa 1clc7 wt) and rat (H4‐II‐E) hepatomas. Pretreating cells with the polyaromat/c hydrocarbon indvcer β‐naphthoflavone resulted in 50‐ to 100‐fold increases in single cell rates of O‐dealkylation of ethoxyresorufin (EROD activity). The use of scanning laser cytometry enabled in situ analysis of both constitutive and inducible biotransformation activities without disruption of cells or intracellular processes that determine the toxi‐cologic fate of exogenous chemicals in vivo.

ISSN:0098-4108    

DOI:10.1080/15287399309531786

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Hazardous pollutants emitted from energy‐related technologies, chemical industries, or waste materials are of increasing public concern because of their potential adverse health effects. Many pollutants have chemical groups of toxicological importance that can be characterized and detected by Raman spectroscopy. Raman spectroscopy, however, has not been widely used in trace organic detection, even though the information contained in a Raman spectrum is valuable for chemical identification. One limitation of conventional Raman spectroscopy is its low sensitivity, which often necessitates the use of powerful and costly laser sources for sample excitation. Raman spectroscopists have recently been able to analyze dilute biological samples as a result of enhancements in the Raman scattering cross section by factors up to 10'° when a compound is adsorbed on or near a special electron‐conducting surface. These spectacular enhancement factors of the normally weak Raman scattering process help overcome the low sensitivity of Raman spectroscopy through a combination of electromagnetic and chemical interactions between the analyte molecule and the surface. The technique associated with this phenomenon is known as surface‐enhanced Raman scattering spectroscopy (SERS). The special conductive surface responsible for the scattering enhancement is referred to as a SERS substrate. For the past few years we have developed the SERS technique, using practical SERS‐active substrate materials based on silver‐coated microspheres deposited on glass. A wide variety of biomarkers have been investigated, including benzola]pyrene, dibenz[a,h]anthracene epoxides, 1 ,N9‐ethenoadenine, 3,N4‐ethenocytosine, and other substances. These biomarkers were measured at nanogram and subnanogram levels. The experimental results are of great analytical interest, since these chemicals are difficult to detect by other techniques, such as luminescence spectroscopy, because of the weak luminescence quantum yields of these DNA adducts. In this paper the potential usefulness of the SERS technique for assessing environmental and health effects from human exposure to toxic pollutants is demonstrated.

ISSN:0098-4108    

DOI:10.1080/15287399309531787

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Effective prevention of cancer requires sensitive early warning systems to identify groups, and ultimately individuals, who are at high risk of developing cancer and to accurately estimate the magnitude of their risk. Incorporated with molecular epidemiologic studies, biologic markers have the potential to provide quantitative human data on the biologically effective dose of carcinogens, resultant molecular effects, and genetic/acquired factors that modulate these effects. Clearly, this information is directly relevant to risk identification and to risk quantification.

ISSN:0098-4108    

DOI:10.1080/15287399309531788

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A method originally developed to detect topoisomerase DNA complexes has been adapted to determine DNA‐protein cross‐links formed in cells following their exposure in vitro and in vivo to cross‐linking agents. A preliminary study on welders and controls has been carried out to assess the feasibility of this assay to detect human exposure to chromium (Cr) and nickel (Ni) that are associated with increased DNA‐protein cross‐links. The percentage of cross‐link was significantly higher among welders (1.85% ± 1.14) than among controls (1.17% ± 0.46; p = .01) Cross‐links were not affected by age, weight, or smoking status. The assay developed has substantial advantages over previous methods, being considerably more simple, inexpensive, and sensitive.

ISSN:0098-4108    

DOI:10.1080/15287399309531789

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Biomarkers of effect have important potential in epidemiology, since they may enable ascertainment of exposure‐effect associations in relatively inexpensive cross‐sectional studies, with confirmation by short follow‐up after cessation of exposure. Arsenic is known to cause human skin and lung cancer, and may also cause various internal cancers including bladder, kidney, and liver cancer. The strongest epidemiological association between arsenic ingestion and an internal cancer is that with bladder cancer. Epidemiological studies of a Taiwanese population exposed to high levels of arsenic from drinking water reported relative risks for bladder cancer well above any other known environmental carcinogen. Populations at increased risk for bladder cancer from other exposures, such as smoking and schistosomiasis infection, have elevated frequencies of micronuclei in exfoliated bladder cells. We have therefore proposed that the bladder cell micronucleus assay could be an appropriate biological marker of genotoxic effect of arsenic exposure. In this paper, we present the rationale for choosing the bladder cell micronudeus assay as a potential biomarker of effect for arsenic. We also briefly describe the studies we are conducting using this biomarker in currently exposed populations.

ISSN:0098-4108    

DOI:10.1080/15287399309531790

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Porphyrins are formed as intermediates in the biosynthesis of heme. In humans and other mammals, porphyrins with eight, seven, six, five, and four carboxyl groups are excreted in the urine in a well‐established pattern. Mercury selectively alters porphyrin metabolism in kidney proximal tubule cells, leading to an altered urinary porphyrin excretion pattern. Previous studies in rats have shown that changes in the urinary porphyrin profile during exposure to mercury as methylmercury hydroxide are uniquely characterized by highly elevated (20‐ to 30‐fold) levels of four‐ and five‐carboxyl porphyrins and by the excretion of an atypical porphyrin (“precoproporphyrin”), which elutes on high performance liquid chromatography (HPLC) approximately midway between penta‐ and coproporphyrins. Changes in the urinary porphyrin profile are highly correlated with the dose and duration of mercury exposure and persist for up to 20 wk following cessation of mercury treatment. In the present studies, the utility of urinary porphyrin profile changes as a biomarker of mercury exposure in human subjects was evaluated. Urinary porphyrin concentrations were measured in dentists participating in the Health Screening Programs conducted during the 1991 and 1992 annual meetings of the American Dental Association and compared with urinary mercury levels measured in the same subjects. Among dentists with no detectable urinary mercury, mean concentrations of urinary porphyrins were within the established normal ranges for male human subjects.

ISSN:0098-4108    

DOI:10.1080/15287399309531791

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor