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PubMed1995

Instrument-dependent fluorochrome sensitivity in flow cytometric analyses.

Flow cytometry has become the preferred technique by which critical clinical evaluations are made such as CD4 counts and aneuploid analyses. Mounting concern has arisen over the numerous techniques, reagents, and different flow cytometric employed to determine these data. Several studies have documented significant differences in results when different flow cytometers are utilized to analyze the same sample. Fluorochrome-dependent instrument sensitivity also has been reported by numerous investigators. As more and more procedures are performed by cytometric analysis, light scatter and fluorescence limitations, which appear to be instrument dependent, demonstrate that not all flow cytometers have the same capabilities. Attempts were made to calculate molecules of equivalent soluble fluorochrome (MESF) values on nine different flow cytometers using fluorescein isothiocyanate (FITC) and R-phycoerythrin (R-PE) labeled microsphere reference standards produced by Flow Cytometry Standards Corporation (FCSC). Dramatic differences were observed in the ability of some cytometers to resolve these microspheres. The diminished resolution appeared to be instrument model and fluorochrome dependent. We propose that diminished fluorescence resolution in certain flow cytometers could be responsible for significant variability in clinical values reported from laboratories utilizing different flow cytometers.

Flow Cytometry↗
PubMed1991

Phosphorus 31 magnetic resonance spectroscopy of human placenta and quantitation with perchloric acid extracts.

Phosphorus 31 magnetic resonance spectroscopic studies of fresh placental tissue are reported that indicate resonances for adenosine triphosphate, inorganic phosphate, sugar phosphates-phosphomonoesters, and phosphodiesters. Perchloric acid extract methods were used to further characterize and quantitate phosphorous metabolites in term human placentas by phosphorus 31 magnetic resonance spectroscopy. The perchloric acid extracts give enhanced resolution of phosphorus signals and allow identification of other phosphorus metabolites including small amounts of phosphocreatine. Emphasis was placed on quantitating adenosine triphosphate levels in the acid extracts with the use of the external reference standard hexachlorocyclotriphosphazene in a coaxial capillary system. Adenosine triphosphate levels measured in this way ranged from 0.404 to 0.709 mumol per gram wet weight. Comparison with an internal standard method with phosphocreatine is also reported. Contribution to the measured high-energy phosphate pool from blood in the highly vascularized tissue was found to be relatively large and could range from 30% to 50% of the total adenosine triphosphate measured.

2,3-Diphosphoglycerate↗
PubMedDate not supplied

Some examples of the MRA application in trading of radionuclide products and radioecological monitoring.

Three examples of bilateral cooperation connected with trading of radionuclide products and radioecological monitoring, are discussed. The example in the field of trading is related to the shipment of Russian sources with a high specific activity of 60Co applied for radiation therapeutics to the UK. The examples in the field of radioecological monitoring concern the establishment of equivalence between the 235U reference standards used in Russia and the USA to classify SNM monitors and ensure radiation safety at salvage of the "Kursk" nuclear-powered submarine. The works accomplished are interpreted in the sense of interaction between the NMIs relative to the Mutual Recognition Arrangement (MRA) ideology. It is suggested to coordinate closely the metrological and applied aspects of the MRA when planning the key comparisons and actualizing the CMC Tables.

Commerce↗
PubMedDate not supplied

Comparative evaluation of five in vitro tests for assessing the eye irritation potential of hair-care products.

This study compared five methods, the isolated rabbit eye (IRE), bovine corneal opacity and permeability (BCOP), EpiOcular, fluorescein leakage (FL) and neutral red release (NRR) assays, for predicting the eye irritation potential of hair-care formulations. Ten shampoo and seven conditioner formulations of known ocular irritation potential were tested. Each group included a market-acceptable formulation as a comparative benchmark. Predictions of ocular irritation were made by using classification models (IRE, BCOP and EpiOcular assays) or by direct comparison with benchmarks (IRE, EpiOcular, FL and NRR assays). The BCOP assay was less sensitive than the IRE test in discriminating between formulations of different irritation potentials, and did not perform as well as the other assays in identifying mild formulations. All of the assays appeared to be better at discriminating correctly between the shampoos than between the conditioners. The EpiOcular assay showed the closest concordance between the in vivo results and the in vitro data from cell-based assays (particularly for shampoos). The FL assay also showed a high concordance (particularly for conditioners). There was a tendency for these in vitro assays to over-predict eye irritation potential, but there was no under-prediction and they were particularly successful at identifying mild formulations. The NRR assay was less predictive with both shampoos and conditioners. The results from this comparative evaluation fully support the continued use of the IRE test as a suitable alternative to in vivo eye irritation testing in rabbits, although it also over-predicted the irritancies of several of the formulations. The value of using concurrent benchmarks (reference standards), appropriate to the materials being tested, in interpreting the data obtained from in vitro tests, was also demonstrated. Overall, the results indicate that further comparisons of the IRE, EpiOcular and FL assays are warranted using much larger numbers of test materials.

Animal Testing Alternatives↗
PubMed2001

Dose variance associated with calibration and administration of radiopharmaceuticals.

Variation in the amounts of radioactivity that is associated with dose calibration and administration of gamma-emitting radioactive drugs was studied. Health systems use radionuclide dose calibrators when they need to assay drugs for radioactivity. However, the radioactive drugs commonly used for therapeutic or diagnostic purposes are compounded and assayed in or administered from containers that differ from those containing the standard reference materials (SRMs). SRMs for four radionuclides--technetium 99m, indium 111, thallium 201, and iodine 131--were drawn up into vials and syringe-needle assemblies of volumes and sizes represented in clinical practice. In each sample, the amount of radioactivity was calculated and compared with values obtained from three dose calibrators. In addition, over a four-month period, 101 samples of technetium Tc 99m medronate injection with a desired activity of 20 mCi were prepared in syringes; the radioactive dose in each syringe was calibrated for administration to a patient at a specific time that day. The amounts of radioactivity at the time of preparation and the time of administration, the amount remaining in the syringe and needle after administration, and the amount reported as administered were recorded. Measurement with the dose calibrators of the SRMs in containers supplied by the National Institute of Standards and Technology showed radioactivity within 10% of the labeled amount, the percentage of variation regulations allow. Measurements of the SRMs in syringe-needle assemblies were within 10% for technetium 99m and thallium 201, 9-16% for iodine 131, and 15-26% for indium 111. The individual doses of technetium 99m medronate injection were, on average, administered on time, but doses were administered up to 75 minutes before and 107 minutes after the calibration time. The mean +/- S.D. amount administered was 19.0 +/- 1.34 mCi. The mean +/- S.D. amount reported administered was 20 +/- 0.24 mCi. How radiopharmaceuticals were dose calibrated and administered influenced the actual dose available to patients.

Calibration↗
PubMed1996

Effects of feeding and short-term fasting on water and electrolyte turnover in female mink (Mustela vison).

Daily (24 h) rates of water and electrolyte turnover were measured in a conventional balance study in ten adult female pastel mink (Mustela vison) given free access to a standard mink feed for a 1-week conditioning period, followed by a 4 d experimental period and a 2 d fasting period. Drinking water was available throughout. In addition, the completeness of urine collection and the fraction of urine collected with the faeces were determined using a new experimental technique based on 24 h recoveries of specific urinary markers such as tritiated p-aminohippuric acid ([3H]PAH) or 14C-labelled inulin ([14C]IN) continuously delivered by small Alzet osmotic pumps implanted intraperitoneally. During feeding the mean individual percentage recovery in urine of [3H]PAH released from the osmotic pumps ranged from 68 to 88% (median 78%). The mean percentage of urinary [3H]PAH recovered from faecal collections was 6% (range 3-12%). In response to fasting the mean individual percentage recovery of [3H]PAH in urine ranged from 62 to 78% (median 68%). For urinary [14C]IN the mean percentage recoveries in fed and fasted animals were 79 and 63% respectively. Furthermore, during fasting, withdrawal of the supplies of dietary water caused a slight but insignificant (P = 0.17) increase in the daily intake of drinking water and, hence, the animals maintained their normal water balance by a dramatic reduction in urine excretion (P < 0.001). At the same time urinary solute excretion declined significantly (P < 0.001), due in part to the cessation of dietary electrolyte intake and in part to reduced formation of urea, whereas urinary osmolality decreased only moderately. The mean 24 h balances of Na, K, Ca, Mg, Cl and P were close to zero and only minor differences between the feeding and fasting periods were observed. When corrected for the measured inaccuracies in urine collection the balance data obtained in the present study represent useful reference standards for normally fed and fasted non-growing mink and, to some extent, useful guidelines for future studies in experimental animals.

Animals↗
PubMed2004

NMR regulatory analysis: determination and characterization of S-adenosyl-L-methionine in dietary supplements.

1H NMR methodology is described for the determination and characterization of the dietary supplement S-adenosyl-L-methionine (SAM), recently introduced to the US market, utilizing a 400 MHz spectrometer without the need of pure reference standards. The developed methodology is able to assess chemical structure, differentiate between biologically-active (S)-diastereomer and biologically-inactive (R)-diastereomer, and determine the ratio of each in the dietry supplement formulation. The determination of the percentage of declared SAM was based on the integrals for the methyl proton of 2-methyl-2-propanol served as an internal standard at delta 1.24 and the methine proton H1' of SAM ribose ring at delta 6.06. The percentage of the active diastereomer was calculated from the relative intensities of the sulfonium methyl singlets corresponding to the major component (S)-diastereomer at delta 2.98 and the minor (R)-counterpart at delta 2.93. The accuracy was established by analyzing synthetic mixtures of the analyte and the internal standard. Excellent agreement was verified between the assay results and the quantities of analyte in the mixture. The mean +/- SD recovery values for SAM and its (R)-diastereomer impurity from a set of 10 synthetic mixtures were 99.6 +/- 0.8% and 22.5 +/- 0.1%, respectively. Using 10 lots, the percentage of SAM ranged from 0 to 110.7% of the declared value and the percentage of the active (S)-diastereomer ranged from 0 to 82.3%.

Adenine↗
PubMed1986

Proposal of standardized methods and reference for assaying recombinant human tumor necrosis factor.

Two assay methods for recombinant human tumor necrosis factor (rH-TNF) were developed, one a biological L-cell assay and the other an enzyme-linked immunosorbent assay. The accuracy and reproducibility of each and the correlation between the two were studied. As a result of this investigation, the two assay methods were found appropriate for standardization of rH-TNF. A freeze-dried reference was prepared, and examination of its potency and stability showed it to be suitable for use as a reference standard for rH-TNF assays.

Antibodies, Monoclonal↗
PubMedDate not supplied

Computation of time-specified tolerance intervals for ambulatorily monitored blood pressure.

Hypertension is an important risk factor for strokes, heart attacks, and other vascular diseases. Pharmacologic treatment of high blood pressure reduces the incidence of these complications and prolongs life, so there is a strong incentive to identify and treat individuals with high blood pressure. The development of automatic instrumentation for noninvasive and ambulatory blood pressure monitoring makes it possible to follow the time course of blood pressure variations continuously in healthy peer groups to be used as a reference standard as well as in potentially hypertensive subjects. For clinical applications, tolerance intervals should be substituted, whenever possible for prediction limits. When only hybrid data (time series of data collected from a group of subjects) are available, such a tolerance interval can be difficult to determine following a parametric approach similar to the procedure used for the computation of prediction intervals when consideration of both within-subject and among-subjects variances is wanted. The authors have developed a nonparametric method for the computation of such tolerance intervals. Because the method is based on bootstrap techniques, it does not require the assumption of normality or symmetry in the data and is thus more appropriate when dealing with small samples. The method was used to establish time-qualified reference limits for series of blood pressure and heart rate values monitored automatically in healthy individuals of both genders. The use of these tolerance intervals may eliminate many false-positive and false-negative diagnoses that might be obtained when relying on time-unspecified single samples. These limits can serve as a reference for comparisons of a given subject's blood pressure series over time, yielding nonparametric measures of extent and timing of any blood pressure excess or deficit. Such indices can then be used for an objective and positive definition of health, for the screening and diagnosis of disease, and for gauging responses to treatment.

Adult↗
PubMed2003

Matrix-assisted laser-desorption time-of flight ionisation and high-performance liquid chromatography-electrospray ionisation mass spectral analyses of two glycosylated recombinant epoetins.

Mass spectrometric analyses of the recombinant proteins in Eprex and Aranesp were undertaken with the goal of producing reference mass spectra and evaluating strategies to improve its applicability as a method for equine and canine doping control of these substances. A simple, low chemical noise deglycosylation reaction removed microheterogeneity due to post-translational carbohydrate attachment and both proteins were detectable using MALDI-TOF-MS. Deglycosylated human erythropoietin (hEPO) was also detected using HPLC-ESI-MS. This is the first time that spectra of deglycosylated Eprex and Aranesp have been published. Eight synthetic reference standards, which match peptides produced by endoproteinase Glu-C enzymatic cleavage of Aranesp and/or Eprex, were analysed by ESI-MS and ESI-MS-MS. The E12 Glu-C peptide, common to both proteins, was detected at the low femtomole-level using gradient nano-HPLC-ESI-MS-MS in the positive ion mode.

Caffeic Acids↗
PubMed1998

Effect of patient position on sonographically measured renal length in neonates, infants, and children.

OBJECTIVE: Renal length as measured on sonography is fundamental in the evaluation of renal disease in children. Understanding the effect of patient position and imaging plane on measured renal length is important for the appropriate use of the standards for interpretation. The goal of this study was to determine how measurement of renal length on sonograms is affected by changes in patient position and imaging plane. SUBJECTS AND METHODS: One hundred seventy-six neonates, infants, and children who were 2 days to 17 years old underwent sonography froin October 1995 through June 1996. The largest long-axis renal dimension in sagittal, coronal, and prone planes was obtained for each kidney. Data were analyzed separately for each kidney to determine the individual variation of renal length. RESULTS: The correlation between maximum renal length on coronal, sagittal, and prone sonograms was greater than .95 for both right and left kidneys. The coronal plane yielded the largest measured renal length and the prone view, the smallest. The median of the absolute value of the differences between individual renal lengths as measured on sonograms in the different imaging planes was 2-3 mm for both left and right kidneys (mean difference, left kidney = 3.34-3.62 mm; mean difference, right kidney = 3.22-3.68 mm). CONCLUSION: The coronal and sagittal views yield the longest measurements and prone views, the shortest. Therefore, initial measurements should be made in coronal or sagittal planes. Prone views should be reserved for situations in which the suspicion exists that the kidney was foreshortened on other views. Reference standards done in a particular plane should be applicable in most situations regardless of the patient position necessary to obtain optimum length.

Adolescent↗
PubMed2006

Comparison of tests to detect oxacillin resistance in Staphylococcus intermedius, Staphylococcus schleiferi, and Staphylococcus aureus isolates from canine hosts.

Multiple tests were compared to the reference standard PBP2a latex agglutination test for detection of mecA-mediated oxacillin resistance in canine staphylococci. Cefoxitin disk diffusion, using breakpoints for human isolates of coagulase-negative Staphylococcus spp., had low sensitivity for detection of oxacillin resistance in members of the Staphylococcus intermedius group.

Animals↗
PubMed1998

Automated electrocardiograph ST segment trending monitors: accuracy in detecting myocardial ischemia.

UNLABELLED: Continuous automated ST segment trending devices (ST trending monitors) are included in most new operating room electrocardiography (ECG) monitors to facilitate ischemia detection, but their efficacy is not well validated. Therefore, we compared their accuracy with that of Holter ECG recorders in detecting ST segment changes (both analyzed offline) in 94 patients undergoing coronary artery bypass graft surgery. Holter ECG tapes were analyzed using standard criteria for determining ECG ischemic episodes, which were compared with those measured by the ST trending monitors. Overall, 42 ischemic episodes were detected by using the Holter monitor in 30 patients. Of the 42 episodes, 38 (90%) were also detected by the ST trending monitors. Sixteen episodes of ST segment deviation were detected by the ST trending monitors, but not by the Holter. The sensitivity of the three ST trending monitors in detecting ischemia was 75%, 78%, and 60% for the Marquette (Milwaukee, WI), Hewlett Packard (Andover, MA), and Datex (Helsinki, Finland) monitors, respectively, with a specificity of 89%, 71%, and 69% relative to the Holter. Compared with the HP and Datex monitors, the Marquette monitor has the best agreement with the Holter (K 0.64). Conditions in which ST trending monitors may be inaccurate were identified and included the appearance of small R-wave amplitude, drifting baseline, and during periods of conduction abnormalities and pacing. We conclude that ST trending monitors have only moderate sensitivity and specificity (< 75% overall) in accurately detecting ECG ST segment changes compared with Holter ECG recordings. Therefore, sole reliance on ST trending monitors for the detection of myocardial ischemia may be insufficient. IMPLICATIONS: Using Holter recordings as the reference standard for detection of intraoperative ischemia, ST trending monitors were found to have overall sensitivity and specificity of 74% and 73%, respectively. Several conditions contribute to the inaccuracy of ST trend monitoring, and additional modification of their performance is necessary to achieve better agreement with the Holter analysis.

Aged↗
PubMed2005

Simultaneous determination of synthetic phosphodiesterase-5 inhibitors found in a dietary supplement and pre-mixed bulk powders for dietary supplements using high-performance liquid chromatography with diode array detection and liquid chromatography-electrospray ionization tandem mass spectrometry.

A high-performance liquid chromatography-diode array detection (HPLC-DAD) method and a liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) method were developed to screen for the presence of synthetic phosphodiesterase-5 (PDE-5) inhibitors and their analogues, namely sildenafil, vardenafil, tadalafil, homosildenafil, acetildenafil and hydroxyhomosildenafil. The methods were applied to pre-market samples submitted to the Health Sciences Authority of Singapore (HSA) for testing. One sample was in the form of capsules while six other samples were pre-mixed bulk powder samples for dietary supplements to be repackaged or formulated into the final dosage forms (usually capsules). Identification of PDE-5 inhibitors and their analogues was achieved by comparing individual peak retention times, UV spectra and mass spectra with those of reference standards. The seven samples were found to contain at least one of the following compounds: sildenafil, vardenafil, hydroxyhomosildenafil, homosildenafil and acetildenafil. The five compounds were simultaneously determined by LC-ESI-MS/MS in multiple reactions monitoring (MRM) scan mode. The method has been validated for accuracy, precision, linearity and sensitivity.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed2003

Rapid analytical technique to identify alpha emitting isotopes in water, air-filters, urine, and solid matrices using a Frisch Grid detector.

A 5-inch-diameter Frisch Grid gas-proportional ionization chamber was utilized at Brookhaven National Laboratory (BNL) to rapidly characterize and quantify alpha-emitting actinides in unprocessed water, soil, air-filter, urine, and solid matrices. Instrument calibrations for the various matrices were performed by spiking representative samples with National Institute of Standards and Technology traceable isotopes of 230Th, 232U, 236Pu, and 243Am. Detection efficiencies were typically 15-20% for solid matrices (soil, concrete, filters, dry urine) and 45% for mass-less water samples. Instrument background over a 512-channel alpha-energy range of 3-8 MeV is very low at 0.01 cps. At optimum efficiency, minimum detectable levels of 0.56 mBq Kg(-1), 74 mBq L(-1) and 14.8 mBq filter(-1) were achievable for 40 x 10(-6) Kg soil, 1 x 10(-3) L tap water (or urine), and 4.5 cm diameter air-filter samples, respectively, each counted for 60 min. Data and spectra are presented showing the quality of results obtained using untreated samples obtained from the BNL Graphite Research Reactor Decommissioning Project. These samples contained Bq to MBq per gram amounts of (239,240)Pu, 241Am, and/or (234,235/238)U (as well as other beta/gamma emitters). Data and spectra are also presented for a very finely pulverized and homogeneous U.S. DOE/RESL soil reference standard (spiked with 239Pu, 241Am, and 233U) that was used to assess precision, accuracy, and reproducibility. Although this technique has its limitations, the advantages are (1) minimal sample preparation, (2) no separation chemistry required, (3) no chemical or hazardous waste generated, and (4) ability to immediately characterize and quantify alpha-emitting nuclides in most matrices. The benefits of this technique to the BNL/DOE Project Managers were rapid (1-2 d) turn-around times coupled with significant cost savings, as compared to commercial off-site analyses.

Air Pollutants, Radioactive↗
PubMed1992

Sandwich ELISA formats designed to detect 17 kDa IL-1 beta significantly underestimate 35 kDa IL-1 beta.

The IL-1 beta precursor (proIL-1 beta) represents a significant component of total IL-1 beta production in certain cell types such as keratinocytes, fibroblasts and alveolar macrophages. It has been presumed that immunodetection systems for the mature 17 kDa IL-1 beta can be used interchangeably for the 35 kDa intracellular proIL-1 beta. However, during attempts to purify alveolar macrophage proIL-1 beta, we found that conventional enzyme-linked immunoassays (ELISAs) (using antibodies directed against the 17 kDa mature IL-1 beta) underestimated the amounts of 35 kDa proIL-1 beta by at least ten-fold compared to detection by Western blot techniques. This difference was due to the fact that ELISAs, with an antigen capture format (i.e., that use more than one epitope), can more readily see these distinct epitopes on mature or partially processed IL-1 beta than on the proIL-1 beta molecule. This problem does not occur with the Western blot technique, either because only one antibody is needed and hence there is no stearic blockade of a second epitope or because it denatures 35 kDa proIL-1 beta during the immobilization step, presumably better exposing epitopes as expressed on mature 17 kDa IL-1 beta. The problem with the ELISA can be partially corrected by proteolytic removal of the aminoterminus of 35 kDa proIL-1 beta with neutrophil elastase. More accurate determinations of proIL-1 beta by ELISA can be made by using 35 kDa proIL-1 beta as the reference standard (when the 35 kDa proIL-1 beta is free of molecular weight IL-1 beta). These data suggest that there are conformational differences between the carboxyterminus of 35 kDa proIL-1 beta and mature 17 kDa IL-1 beta which may affect immunodetection when using antibodies directed against mature 17 kDa IL-1 beta.

Blotting, Western↗
PubMed2003

The development of QUADAS: a tool for the quality assessment of studies of diagnostic accuracy included in systematic reviews.

BACKGROUND: In the era of evidence based medicine, with systematic reviews as its cornerstone, adequate quality assessment tools should be available. There is currently a lack of a systematically developed and evaluated tool for the assessment of diagnostic accuracy studies. The aim of this project was to combine empirical evidence and expert opinion in a formal consensus method to develop a tool to be used in systematic reviews to assess the quality of primary studies of diagnostic accuracy. METHODS: We conducted a Delphi procedure to develop the quality assessment tool by refining an initial list of items. Members of the Delphi panel were experts in the area of diagnostic research. The results of three previously conducted reviews of the diagnostic literature were used to generate a list of potential items for inclusion in the tool and to provide an evidence base upon which to develop the tool. RESULTS: A total of nine experts in the field of diagnostics took part in the Delphi procedure. The Delphi procedure consisted of four rounds, after which agreement was reached on the items to be included in the tool which we have called QUADAS. The initial list of 28 items was reduced to fourteen items in the final tool. Items included covered patient spectrum, reference standard, disease progression bias, verification bias, review bias, clinical review bias, incorporation bias, test execution, study withdrawals, and indeterminate results. The QUADAS tool is presented together with guidelines for scoring each of the items included in the tool. CONCLUSIONS: This project has produced an evidence based quality assessment tool to be used in systematic reviews of diagnostic accuracy studies. Further work to determine the usability and validity of the tool continues.

Bias↗
PubMed2003

Investigations on the effect of cigarette smoking in the comet assay.

The comet assay (single-cell gel electrophoresis, SCG) is widely accepted as an in vitro and in vivo genotoxicity test. Because of its demonstrated ability to detect various kinds of DNA damage and its ease of application, the technique is being increasingly used in human biomonitoring. However, the assessment of small genotoxic effects as typically obtained in biomonitoring may be limited by the different sources of assay variability and the lack of an optimal protocol with high sensitivity. To better characterize the suitability of the comet assay for biomonitoring, we are performing a comprehensive investigation on blood samples from smokers and non-smokers. Because tobacco smoke is a well-documented source of a variety of potentially mutagenic and carcinogenic compounds, smokers should be a suitable study group with relevant mutagen exposure. Here, we report our results for the first sample of 20 healthy male smokers and 20 healthy male non-smokers. Baseline and benzo[a]pyrene diolepoxide (BPDE)-induced effects were analysed by two investigators using two image analysis systems. The study was repeated within 4 months. Furthermore, the influence of a repair inhibitor (aphidicolin, APC) on baseline and BPDE-induced DNA damage was comparatively analysed. In all experiments, a reference standard (untreated V79 cells) was included to correct for assay variability. None of these approaches revealed significant differences between smokers and non-smokers. Although more data is needed for a final conclusion, this study indicates some limitations of the comet assay with regard to the detection of DNA damage induced by environmental mutagens in peripheral blood cells.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗