Laser ablation single-collector inductively coupled plasma mass spectrometry for lead isotopic analysis to investigate evolution of the Bilbilis mint.

This work explores the performance of laser ablation-inductively coupled plasma mass spectrometry using different types of single-collector devices (sector field and time-of-flight instrumentation) for lead isotopic analysis of bronze coins, minted in the ancient city of Bilbilis. The aim of the study was achieving sufficient discrimination power to reveal similarities and differences for coins originating from different historical periods, and to obtain information on the possible source of the lead ores used in their production, while restricting the damage inflicted to the samples such that it is not visible to the naked eye. It was found that satisfactory results (RSD in the 0.15-0.30% range for (207)Pb/(206)Pb and (208)Pb/(206)Pb ratios) could be finally obtained, despite the noisy nature of signals generated upon ablation of the highly inhomogeneous coins, by means of a methodology based on: (a) selection of the line profiling ablation mode; (b) use of a dual pass spray chamber that permits the simultaneous introduction of a solution (containing thallium of known isotopic composition), thus resulting in a wet plasma that showed an increased robustness towards matrix effects and (c) detection using a TOF-ICPMS unit, which proved to be much better suited to deal with the transient signals obtained, while being also sufficiently sensitive to obtain good counting statistics, owing to the high lead level (average around 5%) present in the samples. Moreover, under these conditions, the simultaneous aspiration of the thallium spike permitted accurate correction for mass discrimination, such that it was not necessary to use external matrix-matched standards for calibration.

A linkage map of the Atlantic salmon (Salmo salar) based on EST-derived SNP markers.

BACKGROUND: The Atlantic salmon is a species of commercial and ecological significance. Like other salmonids, the species displays residual tetrasomy and a large difference in recombination rate between sexes. Linkage maps with full genome coverage, containing both type I and type II markers, are needed for progress in genomics. Furthermore, it is important to estimate levels of linkage disequilibrium (LD) in the species. In this study, we developed several hundred single nucleotide polymorphism (SNP) markers for the Atlantic salmon, and constructed male and female linkage maps containing SNP and microsatellite markers. We also investigated further the distribution of male and female recombination events across the genome, and estimated levels of LD between pairs of markers. RESULTS: The male map had 29 linkage groups and was 390 cM long. The female map had 30 linkage groups as was 1983 cM long. In total, the maps contained 138 microsatellite markers and 304 SNPs located within genes, most of which were successfully annotated. The ratio of male to female recombination events was either close to zero or very large, indicating that there is little overlap between regions in which male and female crossovers occur. The female map is likely to have close to full genome coverage, while the majority of male linkage groups probably lack markers in telomeric regions where male recombination events occur. Levels of r2 increased with decreasing inter-marker distance in a bimodal fashion; increasing slowly from approximately 60 cM, and more rapidly more from approximately 12 cM. Long-ranging LD may be consequence of recent admixture in the population, the population being a 'synthetic' breeding population with contributions from several distinct rivers. Levels of r2 dropped to half its maximum value (above baseline) within 15 cM, and were higher than 0.2 above baseline for unlinked markers ('useful LD') at inter-marker distances less than 5 cM. CONCLUSION: The linkage map presented here is an important resource for genetic, comparative, and physical mapping of the Atlantic salmon. The female map is likely to have a map coverage that is not far from complete, whereas the male map length is likely to be significantly shorter than the true map, due to suboptimal marker coverage in the apparently small physical regions where male crossovers occur. 'Useful LD' was found at inter-marker distances less than 5 cM.

Quantitative phase measurements using optical quadrature microscopy.

Imaging of phase or optical path length is becoming more important with the development of better imaging systems, computational algorithms, faster computers, and a greater interest in the imaging of transparent objects. Early phase imaging involved qualitative imaging of phase gradients. New computational algorithms can be used to extract some quantitative phase imaging from these techniques. In contrast, new hardware has enabled full-field quantitative phase imaging on a practical and cost-effective scale. We explore a quantitative comparison between two techniques for imaging phase. In the first technique, phase is recovered from a pair of differential interference contrast images, and in the second technique, phase is measured pixel-by-pixel interferometrically. It is shown, experimentally, that the overall results are similar, but each technique has its own advantages and disadvantages.

Determination of tributyltin in marine sediment: Comité Consultatif pour la Quantité de Matière (CCQM) pilot study P-18 international intercomparison.

The capabilities of National Metrology Institutes (NMIs-those which are members of the Comité Consultatif pour la Quantité de Matière (CCQM)of the CIPM) and selected outside "expert" laboratories to quantitate (C(4)H(9))(3)Sn(+) (TBT) in a prepared marine sediment were assessed. This exercise was sanctioned by the 7th CCQM meeting, April 4-6, 2001, as an activity of the Inorganic Analysis Working Group and was jointly piloted by the Institute for National Measurement Standards of the National Research Council of Canada (NRC) and the Laboratory of the Government Chemist (LGC), UK. A total of 11 laboratories submitted results (7 NMIs, and 4 external labs). Two external laboratories utilized a standard calibration approach based on a natural abundance TBT standard, whereas all NMIs relied upon isotope dilution mass spectrometry for quantitation. For this purpose, a species specific (117)Sn-enriched TBT standard was supplied by the LGC. No sample preparation methodology was prescribed by the piloting laboratories and, by consequence, a variety of approaches was adopted by the participants, including mechanical shaking, sonication, accelerated solvent extraction, microwave assisted extraction and heating in combination with Grignard derivatization, ethylation and direct sampling. Detection techniques included ICP-MS (with GC and HPLC sample introduction), GC-MS, GC-AED and GC-FPD. Recovery of TBT from a control standard (NRCC CRM PACS-2 marine sediment) averaged 93.5+/-2.4% ( n=14). Results for the pilot material averaged 0.680+/-0.015 micro mol kg(-1) ( n=14; 80.7+/-1.8 micro g kg(-1)) with a median value of 0.676 micro mol kg(-1). Overall, performance was substantially better than state-of-the-art expectations and the satisfactory agreement amongst participants permitted scheduling of a follow-up Key comparison for TBT (K-28), a Pilot intercomparison for DBT (P-43), and certification of the test sediment for TBT content and its release as a new Certified Reference Material (HIPA-1) with a TBT content of 0.679+/-0.089 micro mol kg(-1) (expanded uncertainty, k=2, as Sn) (80.5+/-10.6 micro g kg(-1)).

What's new with the NRC certified reference material program.

The environmental CRMs currently available from NRC Ottawa comprise four natural waters for trace elements, four biological tissues for trace elements and methylmercury, three marine sediments for major and trace elements (one sediment has certified values for butyltins) and one fish tissue for organochlorines (PCBs, dioxins). Although significant effort has been expended to maintain this suite of materials, several new initiatives have also recently been completed or are in progress. The certified value for arsenobetaine in Dogfish Muscle CRM DORM-2 has been established. The certification approaches, as well as the studies to determine extraction efficiency of this organoarsenic compound, are presented. A stability study has been completed for Hg in a natural water sample and plans are underway for production of a CRM. Assessment of micronutrient stability in seawater for the purposes of CRM production is continuing and progress on this initiative is discussed.

Ligand preference inferred from the structure of neutrophil gelatinase associated lipocalin.

Neutrophil gelatinase associated lipocalin (NGAL), a constituent of neutrophil granules, is a member of the lipocalin family of binding proteins. NGAL can also be highly induced in epithelial cells in both inflammatory and neoplastic colorectal disease. NGAL is proposed to mediate inflammatory responses by sequestering neutrophil chemoattractants, particularly N-formylated tripeptides and possibly leukotriene B(4) and platelet activating factor. The crystal structures of NGAL display a typical lipocalin fold, albeit with an unusually large and atypically polar binding site, or calyx. The fold of NGAL is most similar to the epididymal retinoic acid-binding protein, another lipocalin, though the overall architecture of the calyces are very different. The crystal structures also reveal either sulfate ions or an adventitiously copurified fatty acid bound in the binding site. Neither ligand is displaced by added N-formylated tripeptides. The size, shape, and character of the NGAL calyx, as well as the low relative affinity for N-formylated tripeptides, suggest that neither the copurified fatty acid nor any of the proposed ligands are likely to be the preferred ligand of this protein. Comparisons between the crystal structures and the recently reported solution structure of NGAL reveal significant differences, in terms of both the details of the structure and the overall flexibility of the fold.

Crystal structure of the MHC class I homolog MIC-A, a gammadelta T cell ligand.

The major histocompatibility complex (MHC) class I homolog MIC-A functions as a stress-inducible antigen that is recognized by a subset of gammadelta T cells independent of beta2-microglobulin and bound peptides. Its crystal structure reveals a dramatically altered MHC class I fold, both in detail and overall domain organization. The only remnant of a peptide-binding groove is a small cavity formed as the result of disordering a large section of one of the groove-defining helices. Loss of beta2-microglobulin binding is due to a restructuring of the interaction interfaces. Structural mapping of sequence variation suggests potential receptor binding sites on the underside of the platform on the side opposite of the surface recognized by alphabeta T cell receptors on MHC class I-peptide complexes.

Expression, purification, crystallization and crystallographic characterization of the human MHC class I related protein MICA.

Crystals of the human MHC-encoded molecule MICA, a homologue of MHC class I proteins, have been grown in hanging-drop vapor-diffusion trials using ammonium sulfate as a precipitating agent with recombinant protein expressed in a baculovirus-based system. Cryo-preserved crystals of MICA belong to the cubic space group F4132 with lattice constants a = b = c = 260.7 A and diffract to a resolution limit of 3.0 A when cryo-preserved. These crystals do not diffract when handled conventionally.

Determination of total mercury in biological tissues by flow injection cold vapour generation atomic absorption spectrometry following tetramethylammonium hydroxide digestion.

A simple, rapid and reliable method was developed for the determination of total mercury in biological samples. Samples were solubilized using tetramethylammonium hydroxide (TMAH). The organically bound mercury was cleaved and converted to inorganic mercury by on-line addition of KMnO4. The decomposed mercury together with inorganic mercury originally present in samples was determined by flow injection cold vapour atomic absorption spectrometry after reduction to elemental mercury vapour using NaBH4. A sample throughput of 100 measurements per hour was achieved after a 30 min dissolution with TMAH. The relative standard deviation for 20 micrograms l-1 Hg was 1.3% (n = 11) and the limit of detection was 0.1 microgram l-1 (3 sigma). The proposed method was validated by the analysis of a suite of certified marine biological reference materials, DORM-2 (dogfish muscle), DOLT-2 (dogfish liver) and TORT-2 (lobster hepatopancreas), with calibration against simple HgII standards.

Immobilization of 8-hydroxyquinoline onto silicone tubing for the determination of trace elements in seawater using flow injection ICP-MS.

A rapid and simple on-line method is described for the preconcentration of Mn, Co, Ni, Cu, Zn, Cd and Pb from sea water using 8-hydroxyquinoline immobilized onto silicone tubing (Sil-8-HQ) via the Mannich reaction. Recoveries between 35 and 95% and limits of detection in the ppt range were obtained using a 2 m long Sil-8-HQ tube with a sample flow rate of 1.0 ml min(-1). A tube could be subjected to sample loading and elution cycles over 200 times. The capacity was 1.5 and 1.3 mug cm(-2) for Cu and Mn, respectively. Cu, Cd, Co, Pb, Mn, Zn and Ni were determined in coastal and open ocean seawater using flow injection inductively coupled plasma mass spectrometry (FI-ICP-MS). Good agreement with certified values for the certified reference materials NASS-4 and CASS-3 was demonstrated when quantitation was undertaken by the method of additions.

Determination of total chromium in Marine Sediment Reference Material BCSS-1.

The determination of Cr in National Research Council of Canada Marine Sediment Reference Material BCSS-1 is addressed. Mixed acid digestions utilizing HF, HClO(4) and HNO(3) were investigated. Single microwave assisted digestions in closed vessels at medium pressures (8 bar) were inappropriate (80% recovery). Double digestion at moderate pressure and digestions at high pressure (70 bar) or lengthy open-beaker hot plate dissolutions resulted in 93+/-5% recovery of certified Cr content. Flame atomic absorption and inductively coupled plasma atomic emission spectrometry were used for quantitation. In all cases, the method of standard additions was necessary to eliminate the approximately 10% enhancement in re- sponce relative to unmatched standards. Compared to a certified content of 123+/-7 microg/g (mean and standard deviation), values of 116+/-6 were obtained using an open beaker digestion; 114+/-5 using a double microwave digestion at 8 bar; 113+/-2 for microwave digestion at high pressure and 111+/-4 at high pressure (81 bar) with triple microwave digestion in a Parr bomb. No acid dissolution procedure is adequate for Cr in this sample although recovery of total Cr is complete from National Institute of Standards and Technology Buffalo River Sediment (SRM 2704).

Position-dependent internal motions and effective correlation times for magnetization transfer in DNA.

An effective correlation time that accounts for position dependence of the combined local angular motions and collective twisting and bending deformations, as well as for anisotropic uniform rotation, is defined in terms of the magnetization-transfer rate and expressed in terms of molecular parameters. Application to measured magnetization-transfer rates from H6 to H5 of cytosine in cases where all other relevant data, including the uniform rotational diffusion coefficients, are known, suggests that the amplitude of local angular motion, as well as that due to collective deformations, is significantly greater for a penultimate base pair than for base pairs near the center of the molecule, and that such amplitudes might be approximately transferable from one molecule to another. Protocols are suggested for using estimated ratios of effective correlation times in the initial calibrations of internuclear distances and in the subsequent structure-refinement process.

Instrumental comparison for the determination of cadmium and lead in calcium supplements and other calcium-rich matrices.

Three brands of Ca supplement, a laboratory-reagent grade CaCO3 and a certified reference material (International Atomic Energy Agency H-5 Animal Bone) wee analysed for Cd and Pb by four different analytical techniques, viz., anodic stripping voltammetry inductively coupled plasma mass spectrometry, flame atomic absorption spectrometry and electrothermal atomic absorption spectrometry. The Pb levels measured by the four techniques in the bone powder were within the certified Pb level in this certified reference material. Similarly, no significant differences [p less than 0.05; analysis of variance (ANOVA)] were observed in samples with Pb concentrations greater than 1 microgram g-1. However, the Pb levels in the laboratory-reagent grade CaCO3 obtained by flame atomic absorption spectrometry (0.79 micrograms g-1) averaged about three times higher than those measured by the other three techniques (i.e., 0.25 micrograms g-1). Although no significant differences (p less than 0.05; ANOVA) in Cd levels were observed within any of the samples (intra-sample variability), the Cd concentration measured in the different Ca supplements (inter-sample variability) varied by three orders of magnitude (ranging from 0.07 to 3.59 micrograms g-1).

False-negative cytology rates in patients in whom invasive cervical cancer subsequently developed.

The 3-year screening interval recommended by the American Cancer Society would appear to decrease the detection of premalignant and malignant disease. The authors have shown that 20% of study patients in whom subsequently invasive cervical cancer developed had at least 2 negative Papanicolaou smears within 3 years of the diagnosis of cancer. Moreover, the majority of false-negative results in the series could be attributed to sample error. The authors recommend yearly or at least biennial cervical cytologic screening.

Concentration of trace metals from sea-water by complexation with 8-hydroxyquinoline and adsorption on C(18)-bonded silica gel.

A reversed-phase liquid chromatographic technique based on a combination of multielement chelation by 8-hydroxyquinoline with subsequent adsorption on C(18)-bonded silica gel is described for the concentration of Cd, Zn, Cu, Ni, Co, Mn and Fe from sea-water. Enrichment factors of 50-100 are readily obtained following elution of the absorbate with methanol to provide a matrix-free concentrate suitable for graphite-furnace atomic-absorption analysis. Quantitative recovery of these elements from near-shore samples of sea-water is demonstrated and the accuracy and precision of the technique are discussed.

The identification of Paragonimus westermanii in bronchial washings. Case report.

Ova of Paragonimus westermanii were identified on Papanicolaou stained slides prepared from bronchial washings of a 40 year-old Korean-American male. In addition to evaluation for neoplasia, a careful search of all cytological material for non-neoplastic conditions is mandatory in our routine practice, especially in this age of population mobility.

Dysplasia and carcinoma in situ of the uterine cervix: prevalence in very young women (under age 22). A one-year study in a health plan population.

An increased number of cervical epithelial abnormalities has been observed in women up to and including 21 years of age. The prevalence and incidence of dysplasia in adolescents and young women is increasing at a time when the incidence of cervical carcinoma is decreasing. We studied 247 women under age 22 with "other than negative" cytologic diagnoses identified during a one-year period (1973) in which approximately 27,500 women in this age group were screened. The prevalence rates of "other than negative" cytology and "other than negative" cytology with confirmed histopathologic abnormalities were 9/1,000 and 2.7/1,000, respectively. Repeat smears and/or tissue speciments were obtained in over 70 per cent of these cases. The majority of abnormalities identified were mild or moderate dysplasia; however eight severe dysplasias and three carcinomas in situ were identified. Fifty-nine percent of these women had a history of one or more pregnancies. Our findings emphasize the presence of dysplasia and carcinoma in situ in young women and suggest the need for re-evaluation of the age at which initiation of the Papanicolaou smear should be considered.