Preliminary FISH-based assessment of external dose for residents exposed on the Techa River.

This paper presents the results of a feasibility cytogenetic study using the fluorescence in situ hybridization (FISH) translocation assay for residents of villages located on the Techa River (Southern Urals, Russia) contaminated with liquid radioactive wastes from the Mayak plutonium facility in 1949-1956. The study was conducted with two groups of donors that differed in their main pathways of exposure. The first group comprised 18 residents of the middle Techa region who were exposed predominantly from ingestion of radionuclides (mostly (89,90)Sr) via the river water and local foodstuffs. The second group included 20 residents of Metlino, the closest village to the site of releases, who were exposed to external γ radiation from the contaminated river bank and exposed internally from dietary intake of radionuclides. A significant linear dependence between the radiation-induced translocation frequency and individual red bone marrow dose from incorporated (89,90)Sr, calculated with the Techa River Dosimetry System (TRDS), was found in the first group of donors. This allowed us to take the contribution of (89,90)Sr to the total radiation-induced translocation frequency into account for the second group of donors and to analyze translocations resulting from external γ-ray exposure. Individual doses from external exposure derived from the corrected translocation frequency for the second group of donors (Metlino residents), using a linear dose-response coefficient of 0.015 translocation/cell/Gy recommended by Edwards et al. in 2005, were shown to vary up to 2.1 Gy, with an average value of 0.48 Gy, which was in agreement with TRDS-based external dose estimates for Metlino residents.

Interlaboratory variation in scoring dicentric chromosomes in a case of partial-body x-ray exposure: implications for biodosimetry networking and cytogenetic "triage mode" scoring.

The international radiation biodosimetry community has recently been engaged in activities focused on establishing cooperative networks for biodosimetric triage for radiation emergency scenarios involving mass casualties. To this end, there have been several recent publications in the literature regarding the potential for shared scoring in such an accident or incident. We present details from a medical irradiation case where two independently validated laboratories found very different yields of dicentric chromosome aberrations. The potential reasons for this disparity are discussed, and the actual reason is identified as being the partial-body nature of the radiation exposure combined with differing criteria for metaphase selection. In the context of the recent networking activity, this report is intended to highlight the fact that shared scoring may produce inconsistencies and that further validation of the scoring protocols and experimental techniques may be required before the networks are prepared to deal satisfactorily with a radiological or nuclear emergency. Also, the findings presented here clearly demonstrate the limitations of the dicentric assay for estimating radiation doses after partial-body exposures and bring into question the usefulness of rapid "triage mode" scoring in such exposure scenarios.

Chromatid damage in human lymphocytes is not affected by 50 Hz electromagnetic fields.

Cultured human blood lymphocytes were exposed during the S/G(2) phases of the cell cycle to continuous extremely low frequency (50 Hz) electromagnetic fields of 0.23, 0.47 or 0.7 mT either alone or immediately after an acute exposure to 1.0 Gy of gamma rays. The ionising radiation, as expected, induced chromosomal aberrations of the chromatid-type observed at the next metaphase. The field applied alone did not induce chromosomal damage nor did it modify the frequency of aberrations caused by the gamma rays.

The yield of radiation-induced chromosomal aberrations in first division human lymphocytes depends on the culture time.

PURPOSE: To investigate two long-held beliefs in radiation cytogenetics that were seemingly contradicted by reports that: (a) protracting gamma-ray exposures over 0.5 h halves the induced aberration yield compared with acute exposure, and (b) that induced aberration yields in guaranteed first in vitro division metaphases (M1) vary with culture time. MATERIALS AND METHODS: Replicate blood samples were exposed for 3 min to 3.0 Gy gamma-rays and standard phytohaemagglutinin stimulated lymphocyte cultures were harvested at 10 times ranging from 45-72 h. Forty-eight hour cultures were also made from blood exposed to 3.0 Gy for 30 min. Slides were differentially stained, combining the harlequin method with fluorescent in-situ hybridization (FISH) painting of chromosomes 2, 3 and 5. M1 metaphases were scored for 1- and 2-way translocations involving the painted chromosomes and all unstable aberrations in the full genomes. RESULTS: Dicentric and translocation yields from the 30 min exposure were approximately 10% lower than in 48 h cultures from cells exposed for 3 min, although this reduction is not significant. Dicentric aberration yields from the 3 min exposed cells cultured over the range 45-72 h remained constant up to 51 h then rose to a different constant value beyond 60 h. The increase at 60-70 h compared with the yield at 48 h was about 50%. A marginal increase at later times was also observed for translocations. CONCLUSION: The protracted exposure experiment produced results consistent with the G-function hypothesis that models the dose rate effect. Therefore the previous report of a marked departure from this model was not confirmed. The reports of aberration yields increasing with time of arrival at metaphase were confirmed. Possible explanations are discussed; the intercellular distributions of aberrations, or of doses to the cells or heterogeneous radiosensitivity of lymphocyte sub-populations. None alone seems sufficient quantitatively to explain the magnitude of the effect. The implications for biological dosimetry, which employs cultures times of approximately 48 h, are considered to be minor.

Criticality accident dosimetry by chromosomal analysis.

The technique of measuring the frequency of dicentric chromosomal aberrations in blood lymphocytes was used to estimate doses in a simulated criticality accident. The simulation consisted of three exposures; approximately 5 Gy with a bare source and 1 and 2 Gy with a lead-shielded source. Three laboratories made separate estimates of the doses. These were made by the iterative method of apportioning the observed dicentric frequencies between the gamma and neutron components, taking account of a given gamma/neutron dose ratio, and referring the separated dicentric frequencies to dose-response calibration curves. An alternative method, based on Bayesian ideas, was employed. This was developed for interpreting dicentric frequencies in situations where the gamma/neutron ratio is uncertain. Both methods gave very similar results. One laboratory produced dose estimates close to the eventual exercise reference doses and the other laboratories estimated slightly higher values. The main reason for the higher values was the calibration relationships for fission neutrons.

Long-term marine litter monitoring in the remote Great Australian Bight, South Australia.

The Anxious Bay beach litter clearance is the longest running annual survey of ocean-based litter in Australia. It's remoteness from centres of human population and location (with respect to prevailing winds and currents) make it an ideal place for monitoring ocean or ship-based litter in Australia's southern oceans and particularly, the Great Australian Bight. Over the 1991-1999 period, a large but gradual decline in the amount of beach washed litter was recorded (with minor peaks recorded during the 1992 and 1994 surveys). Beach washed litter decreased by approximately 86%, from 344 kg recorded in 1991 (13.2 kg/km) to 49 kg in 1999 (i.e. 1.9 kg/km), reaching a maximum of 390 kg in 1992 (or 15 kg/km of beach). However, a sharp increase in litter was recorded in 2000 (i.e. 252 kg or 9.7 kg/km). This increase in litter yield in 2000 is probably due to stronger than average onshore surface flow (or Ekman Transport) in the western Eyre Peninsula and Bight region. Prior to the survey in 2000, the results appeared to indicate that ocean litter on Anxious Bay beach was beginning to level out at around 50-70 kg/year (i.e. 2-3 kg/km). As the beach surveys involve the assumption that the beach is completely cleared of litter, this may represent a baseline level for ocean-based litter in the region. The yields and type of litter collected from the annual survey indicates that the majority of litter washed ashore originates from commercial fishing activities within the Great Australian Bight. Most of the fishing-related litter was directly sourced to the Southern Rock Lobster Fishery (i.e. bait buckets, baskets, pots), the Great Australian Bight Trawl Fishery (i.e. codends, trawl nets) and the Southern Shark Fishery (i.e. monofilament gillnets and longlines). Between 1994 and 1999, large reductions were observed in the amount of bait straps (77% reduction), lobster bait baskets/buckets (86% reduction), nets/ropes (62% reduction) and floats/buoys (83% reduction). Significantly, fishing-related litter in the Bight has reduced at a slower rate than domestic litter. While the level of glass and soft plastics on the beach have both reduced by almost 93% (i.e. 103-7 kg and 119-8 kg, respectively), the level of hard plastics, has diminished at a slower rate, with reductions of only 75% (i.e. 122-30 kg). Some fisheries (i.e. rock lobster, Southern Shark Fishery) have shown marked reductions in fishing-related litter. This is probably due, to some extent, to significant reductions in fishing effort in the region, although this requires further investigation. The information from the Anxious Bay beach litter survey is crucial in monitoring trends in ocean litter in Australia's southern oceans and compliance with international litter regulations. While fishing-related litter remains the major source of ship-based or ocean litter in Australia's southern oceans, the continued reduction in ship-based litter since 1991 supports increasing compliance to MARPOL (Annex V) by commercial fisheries and shipping in the Great Australian Bight. While Australia participates in marine debris monitoring programs in the Antarctic (under CCAMLR), there is currently no national program or management framework to assess, manage and monitor ocean-based litter along Australia's coasts, and monitor compliance with MARPOL. Apart from the commitments under CCAMLR for Antarctic (and sub-Antarctic) marine environments, there are no other regional programs, guidelines or monitoring protocols or to assess and manage ocean litter in the Southern Ocean.

The repair of gamma-ray-induced chromosomal damage in human lymphocytes after exposure to extremely low frequency electromagnetic fields.

G(0) human blood lymphocytes were irradiated with 2.0 Gy gamma-rays and cultured to metaphase whilst held in a 50-Hz power frequency magnetic field of 0.23, 0.47 or 0.7 mT. No differences were found in the frequencies of gamma-induced chromosome aberrations observed in cells held in the EM fields compared with replicates held in a sham coil. Similar field conditions have been reported to increase the frequency of gamma-induced HPRT mutations, leading to a suggestion that the EM fields alter the fidelity of repair of genomic lesions. This was not confirmed by the chromosome aberration assay described here.

Chromosome aberrations induced in human lymphocytes by heavy charged particles in track segment mode.

Human blood was irradiated with accelerated ions: 20 MeV 4He, 425 MeV 12C and 1480 MeV and 996 MeV 16O. For each ion, the blood was exposed to a range of doses as thin specimens in the track segment mode, so that irradiations took place at nearly constant LETs of 31.4, 61, 52 and 69 keV microm(-1), respectively. Lymphocytes were cultured to the first in vitro metaphase, analysed for chromosomal damage and the dicentric aberration frequencies fitted to the linear quadratic model of dose-response. For these high LET radiations, the linear (alpha) yield coefficient predominated and increased with LET, at least up to 60 keV microm(-1). Apart from the 996 MeV oxygen ions, the data indicated the presence of a quadratic (beta) coefficient, statistically consistent with values obtained with low LET radiations. However, the associated uncertainties on the measured beta values were large, illustrating the general problem that beta is more difficult to measure against a dominating and ever-increasing alpha term. The existence or otherwise of a beta component of the dose-response at these radiation qualities has important consequences for modelling mechanisms of aberration induction by radiation.

Possible associations between ELF electromagnetic fields, DNA damage response processes and childhood leukaemia.

Epidemiology has shown an association between exposure to extremely low frequency (ELF) electromagnetic fields (EMF) and childhood leukaemia. The causal nature and biological basis of this association are however questionable. Studies with aneuploid cell lines raised the hypothesis that ELF EMF may act as a coleukaemogen by compromising DNA damage response to genotoxic agents such as ionising radiation. We examined this hypothesis using gamma-ray-induced dicentric chromosome exchange in human lymphocytes. The results from 12 h post-gamma-ray exposure to fields of 0.23, 0.47 and 0.7 mT provide no support to the hypothesis. The power of the study was sufficient to exclude an ELF enhancement of chromosomal exchange of 10-15% (2SE).

Choosing metaphases for biological dosimetry by fluorescence in situ hybridization (FISH).

Data are presented for a subset of lymphocytes characterized by FISH as missing painted chromosomal material. These lymphocytes occur in both control and irradiated subjects. These cells have a much greater frequency of one-way translocations than cells in which all of the painted chromosomal material is present. Their presence contributes to interindividual variability in control translocation yields. These cells do not appear to be more prevalent in persons exposed to high radiation doses. It is suggested that their exclusion when selecting cells for analysis may improve the sensitivity of FISH as a biological dosimeter at low doses. Mechanisms for the production of these one-way translocations in vivo are also discussed, with a proposal that their variable frequency in individuals may be consistent with exposure to chemical clastogens.

The placental transfer of cerium: experimental studies and estimates of doses to the human fetus from 141Ce and 144Ce.

PURPOSE: To measure the transfer of cerium from mother to fetus in experimental animals and estimate doses to the human fetus following intakes of radioisotopes of Ce. MATERIALS AND METHODS: Cerium-141 in chloride solution was administered intravenously to rats at different stages of pregnancy (days 9.5, 12.5 or 18.5), and retention in the embryo/fetus and associated tissues was measured 3 days later in each case. Retention in rat fetal tissues on day 21.5 (shortly before birth) was also measured after administration of 141Ce chloride 1 month prior to conception or 141Ce citrate on day 18.5. Cerium-141 chloride was administered to guinea pigs on day 50 for measurements of fetal retention on day 57 (shortly before birth). RESULTS: Retention of 141Ce in the rat embryo/fetus, measured at 3 days after administration to the mother, increased from about 0.00002% of injected activity per embryo/fetus on day 12.5 to about 0.014% on day 21.5 of gestation. However, the relative concentrations of 141Ce in the embryo/fetus and mother (CF:CM ratio) were between 0.005 and 0.01 in each case. After 141Ce administration prior to conception, retention by the rat fetus on day 21.5 was substantially lower than after short-term administration. Comparison of retention of 141Ce on day 21.5 after administration on day 18.5 as either chloride or citrate showed similar levels in maternal tissues but greater transfer to the fetus (CF:CM ratio of 0.03). Retention in the guinea pig fetus in late gestation at 7 days after administration of (141)Ce chloride was about 0.05% injected activity per fetus, corresponding to a CF:CM ratio of about 0.02. CONCLUSION: These results and other published animal data have been used to specify CF:CM ratios for use in the calculation of doses to the human fetus. The values used were 0.05 for intakes during pregnancy and 0.01 for intakes prior to conception. Doses to the offspring after maternal ingestion of 141Ce or 144Ce are largely due to irradiation from activity in the maternal colon and are insensitive to CF:CM. After inhalation, however, absorption of Ce to blood is much greater and doses to the offspring are dominated by the contribution from activity in the fetus, and therefore dependent on the CF:CM ratio used.

A study to verify a reported excess of chromosomal aberrations in blood lymphocytes of Namibian uranium miners.

This report describes a study to verify an earlier report of excess chromosomal damage in the blood lymphocytes of uranium miners. Coded blood samples from 10 miners and 10 controls were analyzed conventionally for unstable aberrations and by FISH for translocations. Conventional analysis, scoring 1000 metaphases per subject, showed no significant difference between miners and controls in the frequencies of chromosome- and chromatid-type aberrations. Investigators at two laboratories undertook FISH analyses, each scoring 4000 metaphases per subject. When the data from each laboratory were examined separately, one found slightly more translocations in the miners while the other found fewer. In neither case was the difference significant at the 95% level of confidence. Combining the data likewise showed no significant excess of damage in the miners. This applied to simple one- and two-way translocations and to cells with complex exchanges. There was no correlation between levels of translocations and total lifetime doses from occupational and/or background irradiation. A borderline significant excess of rogue cells was found in the miners. This may be a chance observation, as these rare, highly abnormal cells are considered to be unrelated to radiation exposure and are probably due to a virus. The overall conclusion is that the frequency of chromosomal damage in the miners did not exceed that in the controls. Therefore, the result of the earlier study was not confirmed.

Simple chromosome exchanges are not linear with dose.

PURPOSE: To check whether simple chromosome exchanges are linearly related to radiation dose. MATERIALS AND METHODS: Go-irradiated lymphocytes were cultured to produce metaphase preparations. Chromosomes 1 and 2 were painted different colours and the remaining chromosomes counterstained. Cells containing a colour junction involving both chromosomes 1 and 2 were scored fully, so that simple and complex rearrangements were distinguished. RESULTS: At doses of 2 Gy and below very few complex rearrangements were seen. About 90% of exchanges were simple. At these doses the linear component of the dose-effect curve accounts on average for only approximately 30% of the observed yield. CONCLUSIONS: There is a square-law dose component to the yield of simple exchanges in addition to the linear term.

Vaccination for prevention of CAPD associated staphylococcal infection: results of a prospective multicentre clinical trial.

124 stable CAPD patients from 8 Australian and 3 New Zealand centers were randomly assigned in a blinded fashion to one of two groups to study the effect of vaccination using commercial preparations consisting of a combined staphylococcus toxoid and whole killed staphylococci (SB) or normal saline solution (SS) on the incidence of peritonitis and exit site infection and S. aureus nasal carriage over a 12-month prospective period. In addition, levels of IgG, IgA, IgM, C3 and C4 were monitored during the trial period in serum and dialysate; serum levels of anti-alpha hemolysin and dialysate levels of fibronectin and specific antistaphylococcal antibodies were also measured. Over the period, treatment with SB or SS did not affect the incidence of peritonitis, catheter-related infection or S. aureus nasal carriage. However, vaccination with SB elicited a significant increase in the level of serum anti-alpha hemolysin throughout the 12 month duration of the study, although the level of increase was unrelated to the subsequent rate of peritonitis. Vaccination with SB but not SS elicited a significant increase in the dialysate level of specific antibodies against S. aureus. Serum levels of IgG, IgA, IgM, complement C3 and C4 were within the normal range in the CAPD patients studied and remained unaffected by vaccination with SB. In addition, dialysate levels of IgG, IgA, IgM, complement C3 and C4 were 50-100 times lower than corresponding serum levels and remained unaffected by vaccination. In summary, immunisation with an anti-staphylococcal agent was not successful in reducing peritonitis or exit site infection in CAPD patients.

Sorbent membrane dialysis in uremia.

The inclusion of activated charcoal within hemodialysis membranes offers potentially improved plasma clearance of creatinine and middle molecules. However, the carbon becomes saturated with continued use and beyond 1 h removal of solutes is by dialysis alone. Two independently conducted crossover studies, to assess the efficacy of sorbent membrane dialysis (SMD) in the treatment of uremia, found predialysis urea levels increased by approximately 15%, creatinine by 10-15%, and inorganic phosphate levels by 10-18% on SMD compared to conventional hemodialysis. One study also observed "middle molecule' (peak "b') levels elevated. No differences were observable in the clinical status of patients. The results suggest that the charcoal content of the SMD device is too small to effect any advantages over conventional dialysis.

Hemodialyzer performance: an assessment of currently available units.

The performance characteristics of nine currently available disposable parallel-flow dialyzers were assessed, both before and immediately following dialysis, by measuring: (i) in vitro clearances of C14 labeled urea, creatinine, and sucrose and H3 labeled vitamin B12 at standard conditions, (ii) ultrafiltration rates in saline at 37C, and (iii) loss in the mass transfer coefficient-membrane area product (hoA), following a single dialysis. Parallel-plate dialyzers underwent considerable membrane stretching during dialysis and exhibited greater variability, particularly regarding vitamin B12 clearance and ultrafiltration ability, than did capillary dialyzers. The variability in plate units was greater for large-area dialyzers where there were 25 to 26 blood channels. However, despite considerable differences in performance characteristics, all dialyzers were judged to be clinically acceptable in terms of both solute clearance and ultrafiltration characteristics.