Correlations between potassium, rubidium and cesium ((133)Cs and (137)Cs) in sporocarps of Suillus variegatus in a Swedish boreal forest.

An analysis of sporocarps of ectomycorrhizal fungi Suillus variegatus assessed whether cesium ((133)Cs and (137)Cs) uptake was correlated with potassium (K) or rubidium (Rb) uptake. The question was whether intraspecific correlations of Rb, K and (133)Cs mass concentrations with (137)Cs activity concentrations in sporocarps were higher within, rather than among, different fungal species, and if genotypic origin of sporocarps within a population affected uptake and correlation. Sporocarps (n = 51) from a Swedish forest population affected by the fallout after the Chernobyl accident were studied. The concentrations were 31.9 ± 6.79 g kg(-1) for K (mean ± SD, dwt), 0.40 ± 0.09 g kg(-1) for Rb, 8.7 ± 4.36 mg kg(-1) for (133)Cs and 63.7 ± 24.2 kBq kg(-1) for (137)Cs. The mass concentrations of (133)Cs correlated with (137)Cs activity concentrations (r = 0.61). There was correlation between both (133)Cs concentrations (r = 0.75) and (137)Cs activity concentrations (r = 0.44) and Rb, but the (137)Cs/(133)Cs isotopic ratio negatively correlated with Rb concentration. Concentrations of K and Rb were weakly correlated (r = 0.51). The (133)Cs mass concentrations, (137)Cs activity concentrations and (137)Cs/(133)Cs isotopic ratios did not correlate with K concentrations. No differences between, within or, among genotypes in S. variegatus were found. This suggested the relationships between K, Rb, (133)Cs and (137)Cs in sporocarps of S. variegatus is similar to other fungal species.

Accumulation of potassium, rubidium and caesium (133Cs and 137Cs in various fractions of soil and fungi in a Swedish forest.

Radiocaesium ((137)Cs) was widely deposited over large areas of forest in Sweden as a result of the Chernobyl accident in 1986 and many people in Sweden eat wild fungi and game obtained from these contaminated forests. In terms of radioisotope accumulation in the food chain, it is well known that fungal sporocarps efficiently accumulate radiocaesium ((137)Cs), as well as the alkali metals potassium (K), rubidium (Rb) and caesium (Cs). The fungi then enhance uptake of these elements into host plants. This study compared the accumulation of these three alkali metals in bulk soil, rhizosphere, soil-root interface, fungal mycelium and sporocarps of mycorrhizal fungi in a Swedish forest. The soil-root interface was found to be distinctly enriched in K and Rb compared with the bulk soil. Potassium concentrations increased in the order: bulk soil

The distribution of (137)Cs, K, Rb and Cs in plants in a Sphagnum-dominated peatland in eastern central Sweden.

We record the distribution of (137)Cs, K, Rb and Cs within individual Sphagnum plants (down to 20cm depth) as well as (137)Cs in vascular plants growing on a peatland in eastern central Sweden. In Calluna vulgaris(137)Cs was mainly located within the green parts, whereas Andromeda polifolia, Eriophorum vaginatum and Vaccinium oxycoccos showed higher (137)Cs activity in roots. Carex rostrata and Menyanthes trifoliata showed variable distribution of (137)Cs within the plants. The patterns of (137)Cs activity concentration distribution as well as K, Rb and Cs concentrations within individual Sphagnum plants were rather similar and were usually highest in the capitula and/or in the subapical segments and lowest in the lower dead segments, which suggests continuous relocation of those elements to the actively growing apical part. The (137)Cs and K showed relatively weak correlations, especially in capitula and living green segments (0-10cm) of the plant (r=0.50). The strongest correlations were revealed between (137)Cs and Rb (r=0.89), and between (137)Cs and stable Cs (r=0.84). This suggests similarities between (137)Cs and Rb in uptake and relocation within the Sphagnum, but that (137)Cs differs from K.

137Cs in a raised bog in central Sweden.

The vertical distribution of (137)Cs activity in peat soil profiles and (137)Cs activity concentration in plants of various species was studied in samples collected at two sites on a raised bog in central Sweden. One site (open bog) was in an area with no trees and only a few sparsely growing plant species, while the other (low pine) was less than 100 m from the open bog site and had slowly growing Scots pine, a field layer dominated by some ericaceous plants and ground well-covered by plants. The plant samples were collected in 2004-2007 and were compared with samples collected in 1989 from the same open bog and low pine sites. Ground deposition of (137)Cs in 2005 was similar at both sites, 23,000 Bq m(-2). In the open bog peat profile it seems to be an upward transport of caesium since a clear peak of (137)Cs activity was found in the uppermost 1-4 cm of Sphagnum layers, whereas at the low pine site (137)Cs was mainly found in deeper (10-12 cm) layers. The migration rate was 0.57 cm yr(-1) at the open bog site and the migration centre of (137)Cs was at a depth of 10.7, while the rate at the low pine site was 0.78 cm yr(-1) and the migration centre was at 14.9 cm. Heather (Calluna vulgaris) was the plant species with the highest (137)Cs activity concentrations at both sites, 43.5 k Bq(-1) DM in 1989 decreasing to 20.4 in 2004-2007 on open bog and 22.3 k Bq kg(-1) DM in 1989 decreasing to 11.2 k Bq(-1) DM by the period 2004-2007 on the low pine site. (137)Cs transfer factors in plants varied between 0.88 and 1.35 on the open bog and between 0.48 and 0.69 m(2)kg(-1) DM at the low pine site.

DNA damage, cell kinetics and ODC activities studied in CBA mice exposed to electromagnetic fields generated by transmission lines.

CBA mice were exposed outdoors to 50 Hz electromagnetic fields (EMF), with a flux density of about 8 microT rms (root mean square), generated by a 220 kV transmission line. Assays were performed in order to investigate, the possible genotoxic effects after 11, 20 and 32 days of exposure, as well as the effects on body weight, leukocytes, erythrocytes, and the level of ornithine decarboxylase (ODC) activity in spleen and testis. DNA migration was studied on brain cells by single cell electrophoresis (comet assay). After 32 days of exposure a highly significant change of the tail/head ratio of the comets was observed (p < 0.001), showing DNA-damage. Further, a decreased number of mononuclear leukocytes (0.02 < p < 0.05) was observed in mice EMF-exposed for 20 days. In summary, our data indicate that transmission lines of this type may induce genotoxic effects in mice, seen as changes in the DNA migration. These results might have an important implication for health effects.

DNA damage induced in brain cells of CBA mice exposed to magnetic fields.

DNA migration, using single cell gel electrophoresis (comet assay), was studied on brain cells of CBA mice exposed continuously to 50 Hz, 0.5 mT magnetic fields (MF) for 2 hrs, 5 days or 14 days. No differences were observed in the groups MF-exposed for 2 hrs and 5 days compared with controls. However, in the group exposed to MF for 14 days, a significantly extended cell DNA migration was observed (0.02 < p < 0.05). These changes together with results from previous studies indicate that magnetic fields may have genotoxic effects in brain cells.

5-Iododeoxyuridine-125I incorporation in vivo after exposure to a 50 Hz magnetic field.

CBA male mice were continuously exposed or sham-exposed to 50 Hz magnetic fields (MF) for 54 hours. Cell proliferation was studied by measuring the incorporation of 125IUdR (5-iododeoxyuridine) in whole body and organs such as thymus, thyroid gland, heart, lung, kidney, liver, spleen, testis, stomach, caecum, small intestine and colon. No significant differences were found either in body weights or weights of organs in the MF-exposed animals compared with controls. The incorporation of 125I activity in the whole body and in the organs did not differ between MF-exposed and sham-exposed control animals. In conclusion, the results showed no effects on cell proliferation in mice exposed to a continuous 50 Hz MF, with a flux density of 14 mu T peak-peak (p-p) for 54 hours, at least not detectable with 125IUdR as a tracer during the last 30 hours.

Effects of exposure to 50Hz or 20kHz [corrected] magnetic fields on weights of body and some organs of CBA mice.

Males from mouse litters exposed to 50Hz magnetic fields (MF) during the fetal stages right up to 280 days of age, showed a significantly lower body weight as well as kidney and liver weights compared with control animals. These results were not found in females. Adult mice exposed to MF for 140 days showed a significantly lower growth. Similar effects were seen in younger male mice exposed for 60 days. After 90 days exposure kidney and liver weights were significantly lower than controls. Young male mice exposed only for a few days showed a trend towards decreased body weight compared with controls. Using a 20kHz MF, young male mice showed the opposite pattern after 60 days of exposure. In conclusion, we found that the effects depended on exposure time. Young mice and males were found to be more sensitive. Finally, the effects were larger at 50 Hz than at 20 kHz.

An evaluation of ratio systems in radioecological studies.

Replicate samples of soil, Juncus squarrosus and Calluna vulgaris were taken within a grid system on an organic peatland soil site in Ireland. A similar sampling survey was carried out on an organic rich forest soil site in Sweden, where Vaccinium myrtillus and Vaccinium vitis-idaea with corresponding soil samples were taken within a Picea abies stand. The data were used to investigate the relationship between soil and plant 137Cs content and to examine the validity of using ratios to describe this relationship. Findings from both countries were in agreement. There were no significant changes in plant 137Cs concentration associated with increasing soil content. When data from both countries were merged and treated as a single data set, a significant overall positive correlation (95% confidence level) between soil and plant 137Cs levels was observed. Concentration ratios and transfer factors were calculated for 137Cs and 40K uptake from soils to plants. Both ratio types exhibited a clearly defined decrease associated with increasing soil concentrations for both radionuclides. Findings demonstrate serious problems with the use of ratios for the evaluation of radionuclide transfer.

Fetal loss in mice exposed to magnetic fields during early pregnancy.

The effects of low-frequency magnetic fields (MFs) on early pregnancy were studied in CBA/S mice. The magnetic field was a 20 kHz, 15 microT sawtooth. Pregnant females were divided into four groups, two control groups and two exposed groups. One group was exposed to MFs continuously from day 1 postconception (pc) until day 5.5 pc, and the other group was exposed continuously until day 7 pc. All animals were sacrificed on day 19 pc, the day before partus, and their uterine contents were analyzed. No significant increase in the resorption (early fetal death) rate was found in the exposed animals compared to the sham controls. In the group exposed during days 1.0-5.5 pc, the body weight and length of the living fetuses were significantly decreased. Except on day 3 pc (progesterone) and day 13 pc (calcium) in the treated groups, there were no significant differences in progesterone and calcium levels in peripheral blood. Implantation occurred on the same day in MF-treated and control animals.

Radiocaesium transfer to man from moose and roe deer in Sweden.

Studies of radiocaesium in the forest ecosystems in Sweden resulted in aggregated transfer factors quantified for the transfer of 137Cs from soil to moose and roe deer. These aggregated transfer factors were 0.02 m2 kg-1 for moose and 0.05 m2 kg-1 for roe deer. There seems to be no decrease in the 137Cs activity concentrations in moose harvested in our research area and therefore we suggest the use of the physical half-life of 137Cs (30 years) as the effective ecological half-life. The time-integrated transfer of 137Cs from the Chernobyl fall-out to man by moose in Sweden was calculated and found to be 115 GBq, corresponding to 1500 man Sv for moose. The time-integrated transfer by roe deer to man was estimated to be between 25-48 GBq, corresponding to 327-620 man Sv for roe deer. The annual transfer of 137Cs to man by moose has varied between 2.0-2.7 GBq, corresponding to 27-34 man Sv. Depending on the group studied, the mean annual transfer of 137Cs can be calculated to be from about 250 to 43,000 Bq. For example, the mean annual transfer of 137Cs by moose to hunters and their families in Gävle commune, the most affected commune in Sweden, was estimated to be about 26,000 Bq, corresponding to 0.34 mSv.

Kinetics of micronuclei induced by 125IdU in cells of two lines.

The kinetics of the formation of cells carrying micronuclei (MN) after one doubling time (td) incorporation of 125I-iododeoxyuridine (125IdU) to Chinese hamster ovary (CHO) and rat anterior pituitary tumor (GC) cells was studied. Uptake of 125IdU by cells of both cell lines was linearly dependent on the concentration of extracellular 125I activity. The postlabeling time-dependent decrease in cellular activity of 125IdU was exponential in CHO cells and approximately linear in GC cells. The maximum yield of MN was seen during the second and third td after 125IdU incorporation. The frequency of cells with micronuclei increased monotonically with dose in the interval (1, 40) 125I decays cell-1td-1. The dose-response relationship could be fitted by straight lines with slopes of 1.0 (CHO) and 1.2 (GC) on the subinterval (1, 10) and of 0.6 or 0.5, respectively, for the subinterval (10, 40). Below one 125I decay cell-1td-1, the mean frequency of micronucleated binuclear cells was significantly lower than (CHO) or equal to (GC) the control. On average, one 125I decay/cell induced 0.95 +/- 0.5% (CHO) or 1.0 +/- 0.5% (GC) of micronucleated binuclear cells.

Biospheric 129I concentrations in the pre-nuclear and nuclear age.

In order to detect characteristic regional differences or temporal changes of 129I concentrations in the biosphere, thyroids from humans, grazing livestock, and herbivorous wildlife species (reindeer and roedeer) were collected in various areas of the world which are not affected by reprocessing plants. For reasons of comparison, all samples were analyzed for their 129I:127I atom ratios. Human and bovine thyroids taken from the 10th region in Southern Chile (39 degrees-41 degrees South) indicated values of the 129I:127I atom ratio between 1.1 x 10(-9) and 2.0 x 10(-9) and between 1.2 x 10(-10) and 9 x 10(-9), respectively. They showed no significant increase in the concentration of biospheric 129I in comparison with that established in the pre-nuclear age. Atom ratios found in human thyroids collected in Lower Saxony (Federal Republic of Germany), which is a region not directly affected by reprocessing plants, exhibited 129I:127I values between 8 x 10(-9) and 6 x 10(-8) from February 1988 to September 1990. Thyroid glands of reindeer and roedeer as well as heather, moss, and lichen were taken from the Vilhelmina, Heby, and Gävle communes in Sweden and analyzed for 129I and 127I. All three communes were found to be seriously contaminated by fallout from the Chernobyl accident. Highest 129I:127I atom ratios between 3.5 x 10(-7) and 1 x 10(-6) were found in the Gävle commune (approximately 150 km northwest of Stockholm) where the highest 137Cs ground deposition (70-80 kBq m-2) was measured. Two soil samples taken from Krasnaya Gora and Mirny locations in Russia (approximately 200 km northeast of Chernobyl) exhibited ratios of about 1 x 10(-6). These locations showed a 137Cs ground deposition of 370 and 1,300 kBq m-2, respectively.

Kinetics of micronucleus induction by 125I-labelled thyroid hormone in hormone-responsive cells.

Two cell lines, CHO and GC, different in their tissue origin, were investigated with the aim of discovering the correlation between the level of 125I-T3 binding and chromosomal damage induced by 125I decay. Incubation of cells with 125I-T3 has been performed in two exposure schedules: continuous incubation for one to six cell cycles and a pulse-chase schedule involving exposure for one cell cycle. The cellular uptake of 125I-T3, its compartmentization and kinetics were different in the two cell lines. GC cells contained about 7 times more 125I-T3 than CHO cells when incubated with the same external 125I activity concentration (74 kBq of 125I-T3 ml-1 medium). Approximately 70% of the cellular 125I-T3 was found in nuclei of GC cells and only 5% in the nuclei of CHO cells. During the long-term incubation of GC cells with 74 kBq of 125I-T3 ml-1 medium, the 125I activity concentration in cells and their nuclei initially decreased by a half, and thereafter reached a plateau after the third doubling time. In CHO cells and nuclei a very slow linear increase of 125I activity was observed. In GC cells, micronucleus frequency was found to be correlated with nuclear 125I activity. One cell cycle pulse labelling with 74 kBq of 125I-T3 ml-1 medium caused a significant enhancement of micronucleus frequency above the control level during six doubling times, with a maximum at the first post-labelling doubling time. In GC cells continuously incubated with 74 kBq of 125I-T3 ml-1 medium, the micronucleus frequency increased with the incubation time. A model of T3 receptor-dependent dose delivery to nuclei of GC cells continuously incubated with 125I-T3 is proposed. The frequency of micronuclei in the CHO cell line continuously incubated with 125I-T3 did not differ significantly from the control, whereas in the pulse-chase schedule the mean frequency of micronucleated binuclear cells was lower during 4 post-labelling doubling times (significantly at the first and second post-labelling doubling time and insignificantly at the later doubling times) than in the control. Incubation of GC cells with various activity concentrations in medium for four cell cycles resulted in a linear increase of 125I activity in cells and nuclei; however, with a saturation in the region of highest 125I-T3 concentrations used. The frequency of binuclear cells bearing micronuclei was linearly dependent on the nuclear 125I-T3 concentration.

Influence of zeolite on the availability of radiocaesium in soil to plants.

Plant availability of radiocaesium is usually high immediately after incorporation in a soil. However, for some Swedish soils, e.g, peat soils, a high radiocaesium uptake in plants has also been observed during a second growth period after contamination. For these soils the reduction in the plant availability of the nuclide seems to be a slow process. In the last two years the mineral zeolite has become of interest and has been tested as a caesium binding agent in both animal and in soil-plant systems. The aim of this study was to evaluate the time dependency and the effect of zeolite on the plant availability of radiocaesium in a peat soil-plant system. The pot experiments designed for this purpose were carried out in a climate chamber, using winter wheat as the test crop. A significant reduction of the uptake of 134Cs was obtained in wheat when increasing amounts of zeolite were added. This reduction in plant uptake, up to a factor of 8, might depend on two factors. One is that zeolite has reduced the activity concentration of radiocaesium in the soil solution available to the plant roots. The other is that the potassium added with the natural zeolite increased the degree of dilution of caesium in the soil solution. Also, increasing equilibration time for caesium in soil before sowing brought about an effective reduction in the caesium uptake.

Cesium-137 in moose diet; considerations on intake and accumulation.

An attempt was made to estimate the daily intake of 137Cs by moose during different months and seasons, and to compare this result with the 137Cs activity concentration in moose muscles. Plants representative of moose diet in central Sweden showed a high 137Cs activity concentration compared with plants from agricultural systems, and there appears to be very slow reduction of 137Cs activity concentration in these forest plants. It seems that the daily intake of 137Cs was low during the summer, but it exhibited a peak in the autumn, which corresponds to the 137Cs activity concentration in moose muscles and also coincides with the hunting season.

Microscopic and flow cytometric study of micronuclei in iododeoxyuridine labelled cells irradiated with soft x-rays.

Iododeoxyuridine labelled (IUdR(+)) and unlabelled (IUdR(-)) CHO cells irradiated with 2 Gy of soft x-rays showed only minor differences in the kinetics of micronuclei formation during the first 20 hours postirradiation period. Between 20 to 40 hours, the IUdR(-) cells showed approximately a constant number # of micronuclei while the number of micronuclei in IUdR(+) cells was still increasing. The frequency of micronuclei was higher in IUdR(+) cells compared to IUdR(-) cells at 24 hours after irradiation with various doses up to 4.0 Gy. Dose modifying factors were found to be 1.3 (microscopic evaluation) and 1.8 (flow cytometric evaluation). Flow cytometry with use of two parameters, fluorescence from propidium iodide and light scattering, seems to be a good tool to estimate the frequency of micronuclei in CHO cells in the dose range up to about 4 Gy. At higher doses perturbation of the cell cycle and the appearance of dying cells will influence the results.

Enhancement of radiation sensitivity in iododeoxyuridine labelled cells exposed to low energy x-rays.

In order to investigate if low-energy x-rays induce Auger cascades by photoelectric absorption in iodine present in DNA, CHO cells were labelled with iododeoxyuridine (IUdR) for 72 hours. Following labelling, the cells were either irradiated with low-energy x-rays (75 kV, 4 mm Al) or 137Cs-gamma-rays. The radiation response was measured using clonogenic survival, and the survival parameters were analyzed according to the linear quadratic model. The dose modifying factors were determined as the ratios of the alpha-coefficients. The IUdR labelled cells were found to be about 3.2 times as sensitive as the control cells when irradiated with low-energy x-rays. For 137Cs-gamma the ratio was about 1.5. The standard deviations were estimated by Gauss' approximation to be about 0.5 for both irradiation conditions.

Differential response of excision proficient and deficient L5178Y cells to UVC irradiation and benzamide.

L5178Y-R and L5178Y-S cells differ in sensitivity to UVC radiation (D0 values: 2.8 and 9.0 J m-2 respectively, exposure in Fischer's medium). The UVC sensitivity is related to the excision repair ability. Benzamide (Bz), an inhibitor of adenosine diphosphoribosyl transferase (ADPRT), does not modify the lethal effect of UVC radiation in L5178Y-R cells, whereas it sensitizes L5178Y-S cells. The content of NAD+ after irradiation decreases only in the latter cells and this decrease can be prevented by 2 mM Bz treatment. In agreement with the survival data, in L5178Y-R cells neither the proportion of abnormal cells nor the frequency of chromatid aberration are affected by 2 mM Bz treatment, in contrast with L5178Y-S cells. Bz slightly reverses inhibition of 3H-thymidine incorporation only in L5178Y-S cells, but it does not affect the proportions of cells in the different phases of the cell cycle in either cell strain after UVC exposure. These data could be taken as an indirect indication of the involvement of ADPRT in DNA repair in UVC-irradiated L5178Y-S cells. However, the increase in the number of DNA strand breaks in UVC-exposed, Bz-treated cells compared with UVC-exposed untreated cells is the same in both L5178Y strains.