Interplatform comparison between three ion mobility techniques for human plasma lipid collision cross sections

The implementation of ion mobility spectrometry (IMS) in liquid chromatography-high-resolution mass spectrometry (LC-HRMS) workflows has become a valuable tool for improving compound annotation in metabolomics analyses by increasing peak capacity and by adding a new molecular descriptor, the collision cross section (CCS). Although some studies reported high repeatability and reproducibility of CCS determination and only few studies reported good interplatform agreement for small molecules, standardized protocols are still missing due to the lack of reference CCS values and reference materials. We present a comparison of CCS values of approximatively one hundred lipid species either commercially available or extracted from human plasma. We used three different commercial ion mobility technologies from different laboratories, drift tube IMS (DTIMS), travelling wave IMS (TWIMS) and trapped IMS (TIMS), to evaluate both instrument repeatability and interlaboratory reproducibility. We showed that CCS discrepancies of 0.3% (average) could occur depending on the data processing software tools. Moreover, eleven CCS calibrants were evaluated yielding mean RSD below 2% for eight calibrants, ESI Low concentration tuning mix (Tune Mix) showing the lowest RSD (< 0.5%) in both ion modes. Tune Mix calibrated CCS from the three different IMS instruments proved to be well correlated and highly reproducible (R2 > 0.995 and mean RSD ≤ 1%). More than 90% of the lipid CCS had deviations of less than 1%, demonstrating high comparability between techniques, and the possibility to use the CCS as molecular descriptor. We highlighted the need of standardized procedures for calibration, data acquisition, and data processing. This work demonstrates that using harmonized analytical conditions are required for interplatform reproducibility for CCS determination of human plasma lipids.

Impact of Source Conditions on Collision Cross Section Determination by Trapped Ion Mobility Spectrometry

Collision cross section (CCS) values determined in ion mobility-mass spectrometry (IM-MS) are increasingly employed as additional descriptors in metabolomics studies. CCS values must therefore be reproducible and the causes of deviations must be carefully known and controlled. Here, we analyzed lipid standards by trapped ion mobility spectrometry-mass spectrometry (TIMS-MS) to evaluate the effects of solvent and flow rate in flow injection analysis (FIA), as well as electrospray source parameters including nebulizer gas pressure, drying gas flow rate, and temperature, on the ion mobility and CCS values. The stability of ion mobility experiments was studied over 10 h, which established the need for a delay-time of 20 min to stabilize source parameters (mostly pressure and temperature). Modifications of electrospray source parameters induced shifts of ion mobility peaks and even the occurrence of an additional peak in the ion mobility spectra. This behavior could be essentially explained by ion-solvent cluster formation. Changes in source parameters were also found to impact CCS value measurements, resulting in deviations up to 0.8%. However, internal calibration with the Tune Mix calibrant reduced the CCS deviations to 0.1%. Thus, optimization of source parameters is essential to achieve a good desolvation of lipid ions and avoid misinterpretation of peaks in ion mobility spectra due to solvent effects. This work highlights the importance of internal calibration to ensure interoperable CCS values, usable in metabolomics annotation.

The history, development and the present status of the radon measurement programme in the United States of America

The US radon measurement programme began in the late 1950s by the US Public Health Service in Colorado, New Mexico and Utah during the uranium frenzy. After the 1967 Congressional Hearings on the working conditions in uranium mines, the US Atomic Energy Commission (AEC) was asked to conduct studies in active uranium mines to assess the exposure of the miners on the Colorado Plateau and in New Mexico. From 1967 to 1972, the Health and Safety Laboratory of the US AEC in New York investigated more than 20 uranium mines for radon and radon decay product concentrations and particle size in 4 large uranium mines in New Mexico. In 1970, the US Environmental Protection Agency (EPA) was established and took over some of the AEC radon measurement activities. Between 1975 and 1978, the Environmental Measurements Laboratory of the US Department of Energy conducted the first detailed indoor radon survey in the USA. Later in 1984, the very high concentrations of radon found in Pennsylvania homes set the wheels in motion and gave birth to the US Radon Industry. The US EPA expanded its involvement in radon issues and assumed an active role by establishing the National Radon Proficiency Program to evaluate the effectiveness of radon measurement and mitigation methods. In 1998, due to limited resources EPA privatised the radon programme. This paper presents a personal perspective of past events and current status of the US radon programme. It will present an update on radon health effects, the incidence rate of lung cancer in the USA and the number of radon measurements made from 1988 to 2013 using short-term test methods. More than 23 million measurements were made in the last 25 y and as a result more than 1.24 million homes were mitigated successfully. It is estimated that <2 % of the radon measurements performed in the USA are made using long-term testing devices. The number of homes above the US action level of 148 Bq m(-3) (4 pCi l(-1)) may be ∼8.5 million because ∼50 million homes were added since 1990 to the home inventory. This paper will discuss the current instruments and methods used to measure radon in the USA, and what is the effectiveness of radon resistant new construction, the current status of mitigation standards and the proposed testing protocols in schools and large buildings.

Abstract P2-06-03: A Polymorphic AAAG Repeat in the Estrogen Receptor-Related-Gamma Gene May Represent a Breast Cancer Predisposition Biomarker

Background: There is a strong genetic component to breast cancer, which is the most common neoplasm in women; however current risk markers are few, accounting for less than 10% of breast cancer cases. This means that the majority of familial breast cancers remain unexplained. Our laboratory has studied microsatellite polymorphisms for many years, and we developed techniques to assay these understudied regions of the genome en masse and individually via shot-gun methods to rapidly identify those that are likely to be polymorphic and therefore potentially contribute to phenotype.

Material and Methods: Using these novel approaches, we identified a polymorphic AAAG microsatellite repeat in the estrogen-related receptor gamma (ERR-γ) that is expanded in -10% of the general population. We genotyped over 300 individuals and found a longer allelic version (13+ repeat copies) in 14.3% of breast cancer patients, compared to only 4.8% in cancer-free individuals. We computationally identified 22 transcription factors that could bind directly to this AAAG repeat and the surrounding region. We hypothesized that the AAAG-containing region might serve as a promoter for ERR-y.

Results: We found a statistically significant number of breast cancer patients with the expanded AAAG allele, and preliminary experiments confirm that the AAAG-containing region of ERR-γ does indeed drive reporter gene expression in estrogen receptor positive (ER+) MCF-7 breast cancer cells. This was not the case for the ER-breast cancer cells (MDA-MB-231) we also examined. Our initial assessments also revealed that SKBR-3 breast cancer cells are naturally heterozygotic for the long and short allelic versions of the AAAG repeat. Our ongoing studies involve knockdown of transcription factors in MCF-7 cells that abrogate the endogenous expression of ERR-γ.

Discussion: The role of microsatellites in cancer is well defined for colon cancer, but few studies have been conducted to examine the contribution of these simple sequence repeats in breast cancer. We discovered a polymorphic AAAG repeat in the ERR-γ gene, and our studies indicate that a longer version of this repeat is more prevalent in the genomes of breast cancer patients. Based on our assessment, this allele carries a 2.98 relative risk for the development of breast cancer. The higher incidence of this putative biomarker in breast cancer patients may be a result of altered ERR-γ expression, as the AAAG-containing sequence can drive reporter expression. If the frequency of this potentially predictive marker is sustained in a larger population, and the mechanism by which it confers the cancer phenotype can be identified, it may contribute substantially as a biomarker offering surveillance, prophylactic surgery, and chemoprevention options to patients.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-06-03.

A long AAAG repeat allele in the 5' UTR of the ERR-γ gene is correlated with breast cancer predisposition and drives promoter activity in MCF-7 breast cancer cells

We sequenced the 5' UTR of the estrogen-related receptor gamma gene (ERR-γ) in ~500 patient and volunteer samples and found that longer alleles of the (AAAG)(n) microsatellite were statistically and significantly more likely to exist in the germlines of breast cancer patients when compared to healthy volunteers. This microsatellite region contains multiple binding sites for a number of transcription factors, and we hypothesized that the polymorphic AAAG-containing sequence in the 5' UTR region of ERR-γ might modulate expression of ERR-γ. We found that the 369 bp PCR product containing the AAAG repeat drove expression of a reporter gene in estrogen receptor positive breast cancer cells. Our results support a role for the 5' UTR region in ERR-γ expression, which is potentially mediated via binding to the variable tandem AAAG repeat, the length of which correlates with breast cancer pre-disposition. Our study indicates that the AAAG tetranucleotide repeat polymorphism in ERR-γ gene 5' UTR region may be a new biomarker for genetic susceptibility to breast cancer.

State-of-the-art instruments for measuring radon/thoron and their progeny in dwellings--a review

Radon and radon progeny measurements are conducted world-wide for the assessment of the radiation dose to workers and the general public. In the last 10 years, a variety of instruments have been developed that utilize different principles of detection for different measurement applications. The various instruments and methods used today depend on whether radon or radon/thoron progeny are being measured, the type of radiation being detected, and also the duration of the measurement. Other important design criteria are applicability, portability, convenience, reliability, and cost considerations. The instruments under consideration use the following detection systems: pulse ionization chambers, electret ionization chambers, scintillation detectors with zinc sulfide ZnS(Ag), alpha particle spectrometers with silicon diodes, surface barrier or diffused junction detectors, registration of nuclear tracks in solid-state materials, and gamma-ray spectometry with NaI(TI) scintillation crystals or germanium lithium (GeLi) semiconductors. Discussed in this paper are the advantages and disadvantages of the various portable instrumentation used for measuring radon, thoron, and their progeny. Also provided is guidance for their application in the field.

Passive measurement of working levels and effective diffusion constants of radon daughters by the nuclear track technique

Measurements were made of working level ratios and the effective diffusion constants of radon daughters using a special housing designed to provide a uniform diffusional environment at the passive detectors. For 2 of 7 exposures, the measured scale of the diffusion was too large to satisfy the uniformity requirement. For the other 5, it was satisfied and reasonable working level ratios (WLR) were obtained. Such a housing could be used for extended area working level measurements but is too bulky to be suitable for personnel dosimetry. Personnel dosimetry could be done in mines using a passive area measurement of WLR combined with individual passive 222Rn measurements.

Passive, integrated measurement of indoor radon using activated carbon

Activated carbon canisters were tested to determine their adsorption and retention characteristics for radon. Our tests conducted indoors under typical conditions of temperature and relative humidity indicate that simple, inexpensive and maintenance-free passive devices containing 150-200 g of activated carbon can measure radon conveniently and adequately. The amount of radon absorbed in the collector is determined by counting the gamma rays from the decay products of radon. The lower limit of detection for radon is 0.2 pCi/l. for an exposure of 72 hr. Greater sensitivity can be obtained with larger counting systems and devices containing carbon with more surface area. Tests in a residential building and in a test chamber indicate that the measured radon in the canister is proportional to the mean concentration of radon during the period of exposure when correction for relative humidity is made. For practical situations encountered indoors, the device yields results accurate to within +/- 20%. Results from field measurements indicate that the use of the device is feasible.

Radon and radon daughter measurements in solar buildings

Measurements of radon and radon daughters in 11 buildings in five states, using active or passive solar heating, showed no significant excess in concentrations over the levels measured in buildings with conventional heating systems. Radon levels in two buildings using rock storage in their active solar systems exceeded the U.S. Nuclear Regulatory Commission's limit of 3 pCi/l. for continuous exposure in uncontrolled areas. In the remainder of the buildings, radon concentrations were found to be at levels considered to be normal. It appears that the slightly elevated indoor radon concentrations result from the local geological formations and from the tightening of the buildings rather than as a result of the solar heating technology.

Indoor radon measurements in New Jersey, New York and Pennsylvania

The distribution of 222Rn concentrations in 33 buildings near Canonsburg, PA, Lewiston, NY and Middlesex, NJ was investigated over a 2-yr period. One or 2 week-long time-integrated measurements of radon concentration, repeated several times during the study period, were obtained in the living and working areas of the buildings. Average air concentrations of radon, measured over the study period, varied from 0.32 to 4.5 pCi/l. among the buildings, but in only one building did the annual radon concentration exceed the U.S. Nuclear Regulatory Commission's limit of 3pCi/l. for continuous exposure in uncontrolled areas.

Radon daughter plateout--I. Measurements

Radon daughter plateout (surface deposition) was measured directly in 1.9 and 20-m3 chambers. To test the effect of different parameters on plateout, measurements were made over a wide range of particle concentrations and sizes. The results indicate that plateout is strongly dependent on particle concentration. The ratio of surface-deposited activity to total daughter activity in the chamber varied from 4% at particle concentrations greater than 10(5)/cm3 to 86% for particle concentrations less than 10(3)/cm3. Comparison for the experimental data with a theoretical model shows that the theory overestimates plateout and underestimates the airborne concentration by factors of about 3.5 and 3.3, respectively.

Radon daughter plateout--II. Prediction model

By a linear programming procedure, we have optimized the Jacobi room model to fit our data on the partitioning of radon daughters between air and wall surfaces (plateout), obtained at high radon concentrations in a small chamber. Subsequently, the optimized model yielded estimates that compared well with plateout data obtained at lower concentrations in a room-sized chamber. (The experimental work is described separately.) The major change made in the Jacobi model was to reduce the deposition velocity of free airborne radon daughters from 1 to 0.05 cm/sec. This value was obtained by using a fast algorithm to solve the linear programming to arrive at the "best fit". Lesser changes were made in other parameters.

Size distribution of radon daughter particles in uranium mine atmospheres

The size distribution of radon daughters was measured in several uranium mines using four compact diffusion batteries and a round jet cascade impactor. Simultaneously, measurements were made of uncombined fractions of radon daughters, radon concentration, working level and particle concentration. The size distributions found for radon daughters were log normal. The activity median diameters ranged from 0.09 mum to 0.3 mum with a mean value of 0.17 mum. Geometric standard deviations were in the range from 1.3 to 4 with a mean value of 2.7. Uncombined fractions expressed in accordance with the ICRP definition ranged from 0.004 to 0.16 with a mean value of 0.04. The radon daughter sizes in these mines are greater than the sizes assumed by various authors in calculating respiratory tract dose. The disparity may reflect the widening use of diesel-powered equipment in large uranium mines.