Doses from beta radiation in sensitive layers of human lung and dose conversion factors due to <Superscript>222</Superscript>Rn/<Superscript>220</Superscript>Rn progeny

Great deal of work has been devoted to determine doses from alpha particles emitted by ²²²Rn and ²²⁰Rn progeny. In contrast, contribution of beta particles to total dose has been neglected by most of the authors. The present work describes a study of the detriment of ²²²Rn and ²²⁰Rn progeny to the human lung due to beta particles. The dose conversion factor (DCF) was introduced to relate effective dose and exposure to radon progeny; it is defined as effective dose per unit exposure to inhaled radon or thoron progeny. Doses and DCFs were determined for beta radiation in sensitive layers of bronchi (BB) and bronchioles (bb), taking into account inhaled ²²²Rn and ²²⁰Rn progeny deposited in mucus and cilia layer. The nuclei columnar secretory and short basal cells were considered to be sensitive target layers. For dose calculation, electron-absorbed fractions (AFs) in the sensitive layers of the BB and bb regions were used. Activities in the fast and slow mucus of the BB and bb regions were obtained using the LUNGDOSE software developed earlier. Calculated DCFs due to beta radiation were 0.21 mSv/WLM for ²²²Rn and 0.06 mSv/WLM for ²²⁰Rn progeny. In addition, the influence of Jacobi room parameters on DCFs was investigated, and it was shown that DCFs vary with these parameters by up to 50%.     

Thoron levels in traditional Chinese residential dwellings

A survey on radon (²²²Rn), thoron (²²⁰Rn) and its decay products (²²⁰RnD) was conducted in Chinese traditional residential dwellings constructed with loam bricks or soil wall. The activity concentrations in 164 dwellings under investigation were 72.4±59.2 (arithmetic mean, AM) and 57.5±2.0 Bq m⁻³ (geometric mean, GM) for ²²²Rn, and 318±368 and 162±3.7 Bq m⁻³ for ²²⁰Rn, respectively. For ²²⁰RnD, 67 dwellings were studied. The AM of the ²²⁰RnD equilibrium equivalent concentration was 3.8±3.3 Bq m⁻³ with a maximum value of 15.8 Bq m⁻³. On the basis of these results, the average annual effective doses to the local residents due to radon and thoron exposure were 1.44–4.62 mSv. Thoron contributes 12.9–56.6% to the total doses. Preliminary results show that there is a relation between ²²⁰RnD in air and ²³²Th in soil. The correlation factors of outdoor and indoor were 0.88 and 0.40. The ²³²Th activity content of Chinese soil is estimated to be about two times the world average. The traditional residential dwellings with soil construction are still common in China. Further investigations on the ²²⁰Rn level in these dwelling with the aim of dose reduction are proposed.     

D-pantolactone as a circular dichromism (CD) calibration.

A critical study of circular dichromism (CD) measurement at the wavelength region around 220 nm was made. Test sample methods gave deviations of abou 20%, at most, between instruments calibrated at 290 nm with D-10-camphorsulfonic acid. A calculation of the CD from optical rotatory dispersion (ORD) data was made for d-pantolactone which gave a CD maximum at 219 nm, [θ]₂₁₉²⁵ = ?17.3 × 10³ in water. A proposal is made to use this value for calibration of CD in the 220-nm region.     

Temporal variation of thoron decay product concentration in the atmosphere and comparison with radon decay product concentration

Seasonal and long-term variation of the airborne ²¹²Pb concentration, representative of the equilibrium equivalent concentration of thoron decay products (EEC_Rn220), was investigated from 1989 through 1996 at a semi-natural location in southern Germany. Continuous measurement yielded a long-term average concentration of 0.082 Bq m^–3, while daily mean concentrations varied from ≤0.01 to 0.34 Bq m^–3. An average annual effective dose of 1.4 mSv due to outdoor thoron progeny concen-tration was estimated. This is about 2% of the dose due to the average short-lived radon progeny concentration (EEC_Rn222) of 8.4 Bq m^–3 measured for this location in the same period. In most years the seasonal pattern of ²¹²Pb activity concentration in the atmosphere is characterized by two maxima: the first in May and the second one in September. Low concentrations are observed from November through February of each year. This is in contrast to the behaviour of the short-lived ²²²Rn progeny which exhibit enhanced concentrations exactly during these months. The most probable reason for the different temporal behaviour of ²¹²Pb is the extremely reduced flux of thoron gas from the ground during the winter months. Received: 19 August 1997 / Accepted in revised form: 22 January 1998     

Calibration of 192Ir high dose rate brachytherapy source using different calibration procedures

Aim

To calibrate Ir-192 high dose rate (HDR) brachytherapy source using different calibration methods and to determine the accuracy and suitability of each method for routine calibrations.

Background

The source calibration is an essential part of the quality assurance programme for dosimetry of brachytherapy sources. The clinical use of brachytherapy source requires an independent measurement of the air kerma strength according to the recommendations of medical physics societies.

Materials and methods

The Ir-192 HDR brachytherapy source from Gammamed plus machine (Varian Medical Systems, Palo Alto, CA) was calibrated using three different procedures, one using the well-type ionization chamber, second by the in-air calibration method and third using solid water phantoms. The reference air kerma rate (RAKR) of the source was determined using Deutsche Gesellschaft fur Medizinische Physik (DGMP) recommendations.

Results

The RAKR determined using different calibration methods are in good agreement with the manufacturer stated value. The mean percentage variations of 0.21, −0.94, −0.62 and 0.58 in RAKR values with respect to the manufacturer quoted values were observed with the well-type chamber, in-air calibration, cylindrical phantom and slab phantom measurements, respectively.

Conclusion

Measurements with a well-type chamber are relatively simple to perform. For in-air measurements, the indigenously designed calibration jig provides an accurate positioning of the source and chamber with minimum scatter contribution. The slab phantom system has an advantage that no additional phantom and chamber are required other than those used for external beam therapy dosimetry. All the methods of calibration discussed in this study are effective to be used for routine calibration purposes.     

Simultaneous Measurements of Estrogen Nuclear (E2Rn) and Progestin Cytosol (PRc) Receptors in the Hypothalamus and Pituitary Gland of Rats

Abstract

The present methods used to measure estrogen nuclear (E₂Rn) and progestin cytosol (PRc) receptors in the hypothalamus and pituitary gland require that separate assays be performed to determine the concentrations of each receptor. In the present studies we describe a method which simultaneously measures both E₂Rn and PRc in hypothalamic and pituitary tissue. Tissue samples were homogenized in tris-EDTA-glycerol-dithiothreitol buffer and centrifuged at 1500 × g for 5 min. The supernatant was purified for the PRc assay while the nuclear pellet was extracted for the E₂Rn exchange assay.

For the PRc assay, the supernatant was centrifuged at 106,500 × g for 30 min and aliquots from the resultant supernatant then were incubated with ³H-R5020. For the E₂Rn exchange assay, the original pellet was purified further by successively resuspending and centrifuging it through several sucrose solutions. Estrogen-receptor complexes were extracted from the chromatin pellet with a 0.4M KC1 solution and aliquots of the final supernatant were incubated with ³H-estradiol.

In both assays, the samples were placed onto Sephadex LH20 columns and the receptor bound ³H-steroid was eluted directly into scintillation vials. Scatchard analyses revealed that these assays measure a single class of binding sites for E₂Rn and PRc with dissociation constants (K_D) and maximal number of binding sites (Bmax) similar to those previously reported using a separate assay for each receptor.     

Air quality monitoring with regard to222Rn in buildings constructed on disused tin-mining areas

Secondary land uses have taken place on disused tin-mining areas in the form of mixed development projects consisting of housing schemes with commercial and recreational facilities. The cassiterite minerals containing tin are rich in thorium and uranium found in the xenotime and monazite minerals commonly present in the Malaysian terrains. With the upheaval of these minerals from tin-mining activities, the environment is basically exposed to the natural radioactive materials derived from the²³²Th and²³⁸U radionuclides. One of the daughter products is²²²Rn and it is known to be one of the main indoor air pollutants related to the sick-building syndrome. High concentrations of indoor²²²Rn will be hazardous to human health, which is often associated to lung cancer and other chronic diseases. The main purpose of this study is to determine the concentrations of indoor²²²Rn in residential areas constructed on former tin-mining areas with particular reference to places with high human activities such as commercial areas. Air samples were collected using the RDX-013 scintillator cell and the quantitity of²²²Rn determined by the RDA-200 radon/thoron detector. Measurements were made at different times and intervals for the purpose of looking at variations of²²²Rn levels present in the atmosphere. Results of this study showed that the concentration of indoor²²²Rn is higher in the morning (1.64 ± 0.20 pCi L) compared to the levels detected in the afternoon (1.30 ± 0.08 pCi L) for most residential areas. As expected, the concentration of²²²Rn outdoors is lower (1.08 ± 0.08 pCi L) compared to the concentration determined indoors (1.64 ± 0.20 pCi L). Recently constructed houses or buildings in commercial centers seemed to have²²²Rn concentrations relatively higher than those occupied for longer periods of time. However, the levels of²²²Rn concentrations in the study area showed that all were below the maximum permissible level of 4.0 pCi L as stipulated by the United States Environmental Protection Agency. This work also discussed the mitigation measures taken by the building management of commercial buildings to reduce the risk of²²²Rn buildup in an effort to improve public health as a result of the poor indoor air quality.     

Comparability analysis of protein therapeutics by bottom-up LC-MS with stable isotope-tagged reference standards

Comparability studies lie at the heart of assessments that evaluate differences amongst manufacturing processes and stability studies of protein therapeutics. Low resolution chromatographic and electrophoretic methods facilitate quantitation, but do not always yield detailed insight into the effect of the manufacturing change or environmental stress. Conversely, mass spectrometry (MS) can provide high resolution information on the molecule, but conventional methods are not very quantitative. This gap can be reconciled by use of a stable isotope-tagged reference standard (SITRS), a version of the analyte protein that is uniformly labeled with ¹³C₆-arginine and ¹³C₆-lysine. The SITRS serves as an internal control that is trypsin-digested and analyzed by liquid chromatography (LC)-MS with the analyte sample. The ratio of the ion intensities of each unlabeled and labeled peptide pair is then compared to that of other sample(s). A comparison of these ratios provides a readily accessible way to spot even minute differences among samples. In a study of a monoclonal antibody (mAb) spiked with varying amounts of the same antibody bearing point mutations, peptides containing the mutations were readily identified and quantified at concentrations as low as 2% relative to unmodified peptides. The method was robust, reproducible and produced a linear response for every peptide that was monitored. The method was also successfully used to distinguish between two batches of a mAb that were produced in two different cell lines while two batches produced from the same cell line were found to be highly comparable. Finally, the use of the SITRS method in the comparison of two stressed mAb samples enabled the identification of sites susceptible to deamidation and oxidation, as well as their quantitation. The experimental results indicate that use of a SITRS in a peptide mapping experiment with MS detection enables sensitive and quantitative comparability studies of proteins at high resolution.Key words: protein therapeutics, monoclonal antibodies, comparability, peptide mapping, mass spectrometry, LC-MS, stable isotope-tagged reference standard, SITRS     

Inexpensive Laboratory-Constructed Nephelometer

An inexpensive, simple-to-construct nephelometer which was used to monitor the lysis of spheroplasts is described. The nephelometer is a flow-through device with a linear response to cell concentration from the lower detection limit to 8 × 10⁸ cells per ml.     

Reversed-phase high-performance liquid chromatography of salmon calcitonin and its degradation products in biological samples using column switching and flow-through radioisotope detection

For the determination of salmon calcitonin and its degradation products in biological samples, a reversed-phase HPLC method with column switching and flow-through radioisotope detection has been developed using high specific activity [¹²⁵I]salmon calcitonin. Effects of the precolumn packing material and washing solvent were examined in terms of [¹²⁵I]salmon calcitonin recovery. Spiked samples of [¹²⁵I]salmon calcitonin in plasma and kidney homogenate were injected onto a LiChroprep RP-8 precolumn after dilution with 0.1% trifluoroacetic acid. After washing the polar interfering compounds with 0.1% trifluoroacetic acid, the concentrated [¹²⁵I]salmon calcitonin and its degradation products were eluted and separated on a W-Porex C₁₈ column with a gradient of 0.1% trifluoroacetic acid in acetonitrile-water. Detection and calibration of [¹²⁵I]salmon calcitonin were possible down to picogram levels. Reproducible kinetic data for the degradation of intact [¹²⁵I]salmon calcitonin by rat kidney homogenate could be traced.     

Kinetic spectrophotometric method for the determination of ramipril in pharmaceutical formulations

The objective of this research was to develop a kinetic spectrophotometric method for determination of ramipril in pure form and pharmaceutical formulations. The method was based on the reaction of carboxylic acid group of the drug with a mixture of potassium iodate (KIO₃) and potassium iodide (KI) in aqueous medium at room temperature. The reaction is followed spectrophotometrically by measuring the increase in absorbance at 352 nm as a function of time. The initial-rate and fixed-time methods were adopted for constructing the calibration curves. Both the calibration curves were linear in the concentration range of 10.0–70.0 μg mL⁻¹. The detection limits were 0.02μg mL⁻¹ and 0.15-μg mL⁻¹ for initial rate and fixed time methods, respectively. The proposed methods are validated statistically and through recovery studies. The point and interval hypothesis tests have been performed confirming that there is no significant difference between the proposed methods and the reference method. The experimental true bias of all samples is less than ±2%. The methods have been successfully applied to the determination of ramipril in tablets and capsules. Published: October 27, 2005     

Can the agricultural AquaCrop model simulate water use and yield of a poplar short‐rotation coppice?

We calibrated and evaluated the agricultural model AquaCrop for the simulation of water use and yield of a short‐rotation coppice (SRC) plantation with poplar (Populus) in East Flanders (Belgium) during the second and the third rotation (first 2 years only). Differences in crop development and growth during the course of the rotations were taken into account during the model calibration. Overall, the AquaCrop model showed good performance for the daily simulation of soil water content (R² of 0.57–0.85), of green canopy cover (R² > 0.87), of evapotranspiration (ET; R² > 0.76), and of potential yield. The simulated, total yearly water use of the SRC ranged between 55% and 85% of the water use of a reference grass ecosystem calculated under the same environmental conditions. Crop transpiration was between 67% and 93% of total ET, with lower percentages in the first than in the second year of each rotation. The observed (dry mass) yield ranged from 6.61 to 14.76 Mg ha^?1 yr^?1. A yield gap of around 30% was observed between the second and the third rotation, as well as between simulated and observed yield during the third rotation. This could possibly be explained by the expansion of the understory (weed) layer; the relative cover of understory weeds was 22% in the third year of the third rotation. The agricultural AquaCrop model simulated total water use and potential yield of the operational SRC in a reliable way. As the plantation was extensively managed, potential effects of irrigation and/or fertilization on ET and on yield were not considered in this study.     

Doses from radon progeny as a source of external beta and gamma radiation

Great deal of work has been devoted to determine doses from alpha particles emitted by ²²²Rn and its progeny. In contrast, contribution of beta particles and following gamma radiation to total dose has mostly been neglected so far. The present work describes a study of the detriment of ²²²Rn progeny for humans due to external exposure. Doses and dose conversion factors (DCFs) were determined for beta and gamma radiation in main organs and remainder tissue of the Oak Ridge National Laboratory phantom, taking into account ²²²Rn progeny ²¹⁴Pb and ²¹⁴Bi distributed in the middle of a standard or typical room with dimensions 4?m?×?5?m?×?2.8?m. The DCF was found to be 7.37?μSv/WLM. Skin and muscle tissue from remainder tissue receives largest dose. Beta and gamma radiation doses from external exposure were compared with alpha, beta, and gamma doses from internal exposure where the source of radioactivity was the lungs. Total doses received in all main organs and remainder tissues were obtained by summing up the doses from external and internal exposure and the corresponding DCF was found to be 20.67?μSv/WLM.     

An effective calibration technique for radiochromic films using a single-shot dose distribution in Gamma Knife®

PurposeA method of calibrating radiochromic films for Gamma Knife^® (GK) dosimetry was developed. The applicability and accuracy of the new method were examined.MethodsThe dose distribution for a sixteen millimeter single-shot from a GK was built using a reference film that was calibrated using the conventional multi-film calibration (MFC) method. Another film, the test film, from a different set of films was irradiated under the same conditions as the reference film. The calibration curve for the second set of films was obtained by assigning the dose distribution of the reference film to the optical density of the test film, point by point. To assess the accuracy of this single-film calibration (SFC) method, differences between gamma index pass rates (GIPRs) were calculated.ResultsThe SFC curves were successfully obtained with estimated errors of 1.46%. GIPRs obtained with the SFC method for films irradiated using a single-shot showed differences less than one percentage point when dose difference criterion (ΔD) was 2% and the distance to agreement criterion (Δd) was 1 mm. The GIPRs of the SFC method when the films were irradiated following a virtual target treatment plan were consistent with the GIPRs of the MFC method, with differences of less than 0.2 percentage points for ΔD = 1% and Δd = 1 mm.ConclusionThe accuracy of the SFC method is comparable to that of conventional multi-film calibration method for GK film dosimetry.     

Density measurements in a tenuous plasma by a high-frequency resonator with a periodic structure

It is proposed to measure plasma densities in the range of 10⁵–10⁹ cm^?3 by a high-frequency resonator with a periodic structure consisting of annual high-frequency electrodes mounted on oppositely directed racks. The method proposed substantially increases the proportionality factor between the electron density and the shift of the resonator eigenfrequency. This factor is determined by the calibration method using an electron beam with given parameters. The calibration ensures an accuracy of about 10% for density measurements in a plasma produced by a 5-MeV proton beam propagating in air at pressures of 10^?2–10^?5 torr.     

Radon fluxes in tropical forest ecosystems of Brazilian Amazonia: night-time CO2 net ecosystem exchange derived from radon and eddy covariance methods

Radon‐222 (Rn‐222) is used as a transport tracer of forest canopy–atmosphere CO₂ exchange in an old‐growth, tropical rain forest site near km 67 of the Tapajós National Forest, Pará, Brazil. Initial results, from month‐long periods at the end of the wet season (June–July) and the end of the dry season (November–December) in 2001, demonstrate the potential of new Rn measurement instruments and methods to quantify mass transport processes between forest canopies and the atmosphere. Gas exchange rates yield mean canopy air residence times ranging from minutes during turbulent daytime hours to greater than 12 h during calm nights. Rn is an effective tracer for net ecosystem exchange of CO₂ (CO₂ NEE) during calm, night‐time hours when eddy covariance‐based NEE measurements are less certain because of low atmospheric turbulence. Rn‐derived night‐time CO₂ NEE (9.00±0.99 μmol m^?2 s^?1 in the wet season, 6.39±0.59 in the dry season) was significantly higher than raw uncorrected, eddy covariance‐derived CO₂ NEE (5.96±0.51 wet season, 5.57±0.53 dry season), but agrees with corrected eddy covariance results (8.65±1.07 wet season, 6.56±0.73 dry season) derived by filtering out lower NEE values obtained during calm periods using independent meteorological criteria. The Rn CO₂ results suggest that uncorrected eddy covariance values underestimate night‐time CO₂ loss at this site. If generalizable to other sites, these observations indicate that previous reports of strong net CO₂ uptake in Amazonian terra firme forest may be overestimated.     

Absolute and relative quantification of RNA modifications via biosynthetic isotopomers

In the resurging field of RNA modifications, quantification is a bottleneck blocking many exciting avenues. With currently over 150 known nucleoside alterations, detection and quantification methods must encompass multiple modifications for a comprehensive profile. LC–MS/MS approaches offer a perspective for comprehensive parallel quantification of all the various modifications found in total RNA of a given organism. By feeding ¹³C-glucose as sole carbon source, we have generated a stable isotope-labeled internal standard (SIL-IS) for bacterial RNA, which facilitates relative comparison of all modifications. While conventional SIL-IS approaches require the chemical synthesis of single modifications in weighable quantities, this SIL-IS consists of a nucleoside mixture covering all detectable RNA modifications of Escherichia coli, yet in small and initially unknown quantities. For absolute in addition to relative quantification, those quantities were determined by a combination of external calibration and sample spiking of the biosynthetic SIL-IS. For each nucleoside, we thus obtained a very robust relative response factor, which permits direct conversion of the MS signal to absolute amounts of substance. The application of the validated SIL-IS allowed highly precise quantification with standard deviations <2% during a 12-week period, and a linear dynamic range that was extended by two orders of magnitude.     

An improvement of the method for calibrating measurements of photosynthetic CO2 flux

Measurements of rapid changes in concentrations and fluxes of gaseous compounds relating to photosynthetic gas exchange are commonly performed using flow-through cuvettes in connection with infrared gas analysers. The accuracy and repeatability of these measurements relies ultimately upon the design of the system as a whole, rather than upon each of its components, and therefore the calibration and testing of the system should be performed keeping this in mind. We present here a simple and efficient method for the calibration of such a measurement system using a precisely determined CO₂ flow. This method gives us the opportunity to take into account any disturbing effects caused by undesired properties of the chamber or tubing materials. With the proposed calibration method, the accuracy of the CO₂ flux measurement is improved from 8% up to the level of 2%, determined mainly by the accuracy of the control gas used for calibration of the CO₂ analyser.     

Calibration of the comet assay for the measurement of DNA damage in mammalian cells

We used X-rays from a linear accelerator and from a low energy therapeutic source to calibrate the single cell gel electrophoresis (comet assay), a widely used method to measure DNA damage. γ-Rays from ⁶⁰Co, with known efficiency in inducing DNA breakage, were used as reference. Human lymphocytes and one murine tumour cell line, F10-M3 cells, were irradiated under different experimental conditions. A similar relationship between radiation dose and induced DNA damage was obtained with γ- and X-rays. A calibration curve was constructed to convert the comet assay raw data into break frequency. The median levels of DNA breaks and oxidative damage in circulating lymphocytes from healthy volunteers were calculated to be 0.76 and 0.80 breaks/10⁹ Da, respectively, (0.50 and 0.52 breaks/10⁶ bp). The values of oxidative DNA damage were in the same order of magnitude as those found by others with HPLC methods.     

Response surface optimization for the continuous glucose isomerization process

Production of fructose via a continuous glucose isomerization process was optimized using response surface methodology. Glucose isomerization was performed using immobilized glucose isomerase in a flow-through tubular reactor. Process factors eg pH (7.0–7.8), temperature (50–60°C), flow rate (5–17 ml min^–1) and glucose content (30–50% w/w) of the feedstock solution were simultaneously tested according to a central composite experimental design. Measured responses such as % isomerization, and fructose yield (gh^–1) has an excellent correlation with tested factors. The highest desirability,D, (geometric mean of % isomerization and fructose yield) was obtained when the feedstock (56–60°C) had 34–36% glucose, a pH of 7.4–7.8 and was pumped at 15 ml min^–1.