Split (1)

train · 617k rows

text stringlengths 2 132k	source dict
(i.e. the χ2 is greater than the degrees of freedom (df)), then the standard error should be increased by ( χ2 /df) 1/2 . Many computer programs calculate SE values 49 that are based on the sum of squares, instead of the Poisson estimate of the variance, which may lead to a false underestimation of the Poisson error. F...	{ "page_id": null, "source": 7334, "title": "from dpo" }
and the z value was higher than 1.96 (the cut off value for the normal distribution; both values can be found in the standard tables). The F test, which is described in Annex VI, is a ratio of two Chi-squared distributions and F.05 [8, 8] means the cut off value for alpha = 0.05, for 8 degrees of freedom for the numera...	{ "page_id": null, "source": 7334, "title": "from dpo" }
There are, however, sufficient data published from surveys of subjects exposed only to background radiation to show that there is a small positive background level of aberrations. An alternative method adopted by some workers is 50 therefore to use a small positive background value as a data point and to ascribe a larg...	{ "page_id": null, "source": 7334, "title": "from dpo" }
fitted coefficients, as these are required for calculation of the uncertainties on dose estimates (Section 9.7.3). 2 R is a free software environment for statistical computing and is available for download from 51 9. DICENTRIC ANALYSIS The following text concerning cell culture, fixation and slide staining is written ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
48 hours. Medium should be supplemented with L-glutamine, heparin and antibiotics. Penicillin and streptomycin are commonly used (details found in Annex I). Depending on the manufacturer, many media already contain these antibiotics. However, antibiotics may need to be added when diluting the medium to working strength...	{ "page_id": null, "source": 7334, "title": "from dpo" }
the final culture mixture does not exceed about 50 μM (15.4 μg/mL). Above this level there is the possibility of BrdU causing excessive mitotic delay . With fresh (<24 hours) blood specimens, a final culture concentration of about 15 μM is often satisfactory. If blood specimens are delayed in transit so that they are m...	{ "page_id": null, "source": 7334, "title": "from dpo" }
for analysis purposes, select only those cells in first mitosis. The Cyt-B is added at 24 hours into the culture period at a final concentration of 2 μg/mL. This technique was first used by Hayata et. al. to identify cells in the first cell cycle, where differentiation was based on the number of chromosomes rather tha...	{ "page_id": null, "source": 7334, "title": "from dpo" }
is advisable to monitor its performance with, for example, a thermocouple and a chart recorder. Too low a temperature will result in a poor yield, if any, of metaphases after 48 hours. If the temperature is high (38°C, or above), cells will progress more quickly through the cycle so that unacceptably high numbers of se...	{ "page_id": null, "source": 7334, "title": "from dpo" }
which cultures can be set up. However, the number of resultant metaphases per microscope slide is generally smaller than with the other methods. The procedure is to add 0.3 mL of whole blood and 0.1 mL of PHA working solution to a vessel containing 4 mL of medium and 1 mL of serum and then to incubate. 9.1.5.2. Separat...	{ "page_id": null, "source": 7334, "title": "from dpo" }
to an optimum value. This value is likely to vary between laboratories and so should be independently established but it is likely to be in the range 0.5–2.0 x 10 6/mL. A detailed protocol for this has been given by Hayata et al . and McFee et al. [123, 124], who point out that the method is particularly suitable for p...	{ "page_id": null, "source": 7334, "title": "from dpo" }
. Early addition of Colcemid could allow cultures to be prolonged beyond 48 hours to allow for longer cell cycle times in some individuals, e.g. the elderly. 9.2. FIXATION PROCEDURE Lymphocyte cultures are conventionally incubated for 48 hours, although the exact time may vary between laboratories from 46 to 52 hours. ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
5–10 mL of freshly prepared fixative (3:1 methanol/acetic acid). The fixative should be added slowly, but at a constant rate, while the tube is agitated with, for example, a vortex mixer. This is important since it ensures that the cells are dispersed into a uniform suspension. The cells should then be spun down again ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
of distilled water and ice cubes. Improved wetting of the slides is obtained if some methanol is poured on top of the iced water, but not stirred in. Surface liquid should be shaken from the slide a moment before the cells are dispensed. Experience has shown that spreading of the chromosomes can be strongly influenced ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
(FPG) staining is recommended as this permits the analysis to be confined to the first in vitro division metaphases (M1) . However, this method has certain drawbacks which can be overcome by using conventional Giemsa staining, as well as FPG. Many workers have noted considerable variation in the quality of FPG staining...	{ "page_id": null, "source": 7334, "title": "from dpo" }
the level is higher, this may require an adjustment of the aberration yield which could introduce some extra error. This would require certain assumptions regarding, for example, the proportion of dicentrics in M2 cells which are still accompanied by an acentric fragment. As stressed earlier, it is a better policy to a...	{ "page_id": null, "source": 7334, "title": "from dpo" }
stained as described below. The RNase A cleaning procedure can also be used after destaining old slides or on micronucleus preparations. For these applications, concentrations and times may vary . 9.3.2. Fluorescence plus Giemsa (FPG) staining This method is derived from that published by Perry and Wolff with some mod...	{ "page_id": null, "source": 7334, "title": "from dpo" }
R66 improved) Giemsa stain in pH 6.8 phosphate buffer for 5 min, washed in buffer, briefly rinsed in distilled water and allowed to dry, finally mounted with a cover glass using a mounting medium. Figs 10 and 11 show Giemsa-stained metaphases. It is possible to modify the staining specifically to highlight centromeres ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
higher magnification to be of analysable quality. It is important that this initial scanning be done at a magnification low enough to prevent a bias towards selecting cells 60 which contain aberrations. Having found a likely metaphase, the scorer should switch to high magnification (about x 1000 to x 2000), ignore, if ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
should be recorded, although for dosimetry purposes only the data on dicentrics, or dicentrics plus rings will normally be used. The x and y stage co-ordinates of all complete cells analysed, including those free from aberrations, should be recorded for possible future reference. 9.4.2. Computer assisted microscopy Met...	{ "page_id": null, "source": 7334, "title": "from dpo" }
6. LAYOUT OF A DATA SHEET FOR RECORDING ABERRATIONS Slide No: Scorer: Microscope No: NDate: Cell No. Stage coordinates No. of chromosomal pieces Dicentrics Centric rings Excess acentrics Remarks x y1 100.1 1.2 46 2 103.4 1.5 47 1 13 105.4 1.2 49 2 1 24 112.4 1.6 46 5 112.7 1.8 48 26 120.1 1.2 46 17 122.7 1.5 47 18 124....	{ "page_id": null, "source": 7334, "title": "from dpo" }
more difficulty as it frequently fades after several months. It is advisable to keep the stained slides in a box in a dry place at room temperature. However, faded slides can be retrieved by carefully soaking off the coverslip and restaining 62 with conventional Giemsa. Attempts to restain with FPG will not succeed. St...	{ "page_id": null, "source": 7334, "title": "from dpo" }
Co / 137 Cs gamma ray curves. However, it is generally considered to lie closer to the latter, and so it is recommended that the gamma ray curve be used. 9.7.2. Number of cells to be analysed In order to produce a dose estimate with a statistical uncertainty small enough to be of value, a large number of cells usually ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
recommended as being applicable in all cases. However, as a general rule it is suggested that 500 cells or 100 dicentrics should be scored in order to give a reasonably accurate estimate of dose. Table 7 shows the limits calculated using this method for several dose estimates up to 1.0 Gy. 63 TABLE 7. THE EFFECT OF INC...	{ "page_id": null, "source": 7334, "title": "from dpo" }
by Merkle, it allows both the Poisson error on the yield and the errors on the calibration curve to be taken into account. Merkle’s approach, illustrated in Fig. 24, involves the following steps: (1) Assuming the Poisson distribution, calculate the yields corresponding to the lower and upper 95% confidence limits on th...	{ "page_id": null, "source": 7334, "title": "from dpo" }
dicentrics from 0 to 103. For the 25 dicentrics observed in this example the Y Lis 16.768/500 = 0.034 and Y U is 36.03/500 = 0.072. TABLE 8. THE POISSON UPPER AND LOWER 95% CONFIDENCE LIMITS ON OBSERVED NUMBERS (X) OF DICENTRICS (adapted from ) X Lower Upper X Lower Upper X Lower Upper X Lower Upper 0 0 3.285 26 16.77 ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
46 34.05 60.24 72 55.51 89.23 98 79.98 118.35 21 12.817 31.675 47 34.665 61.9 73 56.99 90.37 99 79.98 120.36 22 13.765 32.277 48 34.665 62.81 74 58.72 91.78 100 80.25 120.36 23 14.921 34.048 49 36.03 63.49 75 58.72 93.48 101 81.61 121.06 24 14.921 34.665 50 37.67 64.95 76 58.84 94.23 102 83.14 122.57 25 16.768 36.03 51...	{ "page_id": null, "source": 7334, "title": "from dpo" }
and D U are 0.51 and 0.97 Gy respectively. If covariances are not available, the confidence limits can be approximated by Eq. (8). This equation is valid as the contribution to uncertainty from the covariances is comparatively small. 422 var var var DDCRDDCY βαβα ++±++= (8) With well-established calibration curves base...	{ "page_id": null, "source": 7334, "title": "from dpo" }
U and Y L are: 1074 025 03 36 500 03 36 19 1 ...Y.U =⎟⎠⎞⎜⎝⎛×= (10) 0217 025 77 16 500 77 16 19 1 ...Y.L =⎟⎠⎞⎜⎝⎛×= (11) Using these values D L and D U are 0.39 and 1.19 Gy respectively. 9.7.4. Extension of dose calculations for more complex exposure scenarios The previous section applies to cases where a large acute acc...	{ "page_id": null, "source": 7334, "title": "from dpo" }
rays or gamma rays from 60 Co, 192 Ir and 137 Cs sources, the effect is sufficiently small for the dicentrics to have an approximately Poisson distribution. Accidental exposure to high LET radiation such as neutrons will also produce an overdispersed distribution because of the manner in which the dose is deposited at ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
give a new value for the neutron yield; (5) Repeat steps 1 to 4 until self-consistent estimates are obtained. In the case where a physical estimate of the ratio of neutron: gamma dose is not available, the above method is not possible. One approach would be to express the dose in Gy-Eq as was done for the Tokai-mura ac...	{ "page_id": null, "source": 7334, "title": "from dpo" }
persons rarely understand the concept of uncertainty. There are a number of approaches that can be used to aid interpretation of results. Firstly, although it is not strictly statistically accurate, it can be explained that there is only a 2.5% chance of the dose being greater than the upper 95% confidence limit. Addit...	{ "page_id": null, "source": 7334, "title": "from dpo" }
/e –8.2 , which is 0.36788/0.00027 which is approximately 1300. The values of mean, lower and upper confidence intervals on dose, plus the odds ratio for zero dose: badge dose, are shown in the top line of Table 9, with other values below that would have been quoted if different numbers of dicentrics had been seen in 1...	{ "page_id": null, "source": 7334, "title": "from dpo" }
as potentially a partial-body exposure scenario. In cases of uncertainties in whether there are significant differences between the whole body and partial body dose estimates (Section 9.7.3), then the recommendation is to use the two methods described here only when the data are significantly non-Poisson. Method 1 This...	{ "page_id": null, "source": 7334, "title": "from dpo" }
if free from aberrations, to be less likely than unexposed cells to reach metaphase by 48 hours in culture. If the fraction of irradiated cells which reach metaphase was p, the fraction of the body irradiated, F, is given by pffpfF +−= 1 (14) 71 The p value is estimated by the equation P = exp(-D/D o ) (15) where: D is...	{ "page_id": null, "source": 7334, "title": "from dpo" }
or more aberrations. Qdr is the expected yield of dicentrics and rings among the damaged cells, N U, and is given by 2111 > YYU eYNXQdr −−== (16) where: X is the number of dicentrics and rings, and Y 1 and Y 2 are yields of dicentrics plus rings and of excess acentrics, respectively. As Y 1 and Y 2 are known functions ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
that some lymphocytes containing aberrations continue to exist in the peripheral circulation for many years after an irradiation. However, a delay of more than a few weeks between irradiation and sampling has been shown to reduce the aberration yield. This is particularly apparent following large doses that are suffici...	{ "page_id": null, "source": 7334, "title": "from dpo" }
these studies there was a long initial plateau in aberration yield, lasting about 20 weeks, which was followed by a steep fall which persisted over four years. Over the first four years they calculated that the dicentric yield dropped at a rate of about 43% per year and thereafter the decline was about 14% per year. In...	{ "page_id": null, "source": 7334, "title": "from dpo" }
damage is offset by unimpeded divisions from the stem cell pool. Laborious banded karyotyping has now been replaced by FISH as the optimum method for screening large numbers of cells for the presence of rare, random, non-constitutional stable translocations for retrospective biological dosimetry. This is described in S...	{ "page_id": null, "source": 7334, "title": "from dpo" }
been shown to be on the order of ~ 2 hours [96, 147]. Therefore, in the case of continuous irradiation, it is necessary to know the length of time for which the exposure has lasted and to make the simplifying assumption that the dose rate during the exposure remained more or less constant. It is only worth attempting t...	{ "page_id": null, "source": 7334, "title": "from dpo" }
emitted, the metabolic pathways into which the nuclide may be incorporated and the subject’s physiological status. Chromosome aberrations in excess of background levels may be seen in lymphocytes taken from people who are internally contaminated. However, because of the many confounding factors, it is not possible to u...	{ "page_id": null, "source": 7334, "title": "from dpo" }
in practice, a linear dose–response would be expected. In the absence of a specific in vitro dose–effect curve for tritium, an X ray curve around 200–300 kVp will suffice. Prosser et al. have demonstrated an RBE of 1.13 at low doses or dose rates for tritium with respect to 250 kVp X rays. 9.7.5. Examples of dose esti...	{ "page_id": null, "source": 7334, "title": "from dpo" }
scored and 120 dicentrics observed, i.e. 1.2 dicentrics per cell. The neutron to gamma ratio supplied from physical measurements is 2:3 in absorbed dose. Cytogenetic dose estimates are to be made using calibration curves for 0.7 MeV fission spectrum neutrons and 60 Co gamma rays. The yield equations for these curves ar...	{ "page_id": null, "source": 7334, "title": "from dpo" }
a penetrating radiation exposure of 250 mSv. No colleagues who regularly worked alongside him recorded exposures on their dosimeters. There was no evidence of any systems failure or any other explanation for the overdosed badge. The case was referred for cytogenetic analysis where 1000 metaphases were scored and all we...	{ "page_id": null, "source": 7334, "title": "from dpo" }
dicentrics per irradiated cell, which corresponds on the dose–response curve to 2.97 Gy. The size of the irradiated fraction, f, is given by solving Eq. (13), which, in this example, gives f = 0.176. As this value represents the population of cells which was irradiated and survived, it needs to be adjusted, as describe...	{ "page_id": null, "source": 7334, "title": "from dpo" }
the dicentric yield Stephan et al. have reported an accident in which two men were fairly uniformly exposed for about five minutes to a 60 Co gamma ray source. They wore film badges which indicated 470 and 170 mSv and these values agreed very well with physical calculations of the doses. Unfortunately, blood sampling ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
evident from skin burns. This was further reflected in the aberration data, where doses estimated by the Qdr method were 1.95 and 1.50 Gy, substantially higher than the values of 1.52 and 0.54 Gy whole-body 78 dose, respectively, from the yields of dicentrics and rings on a per cell basis. The values of dicentrics and ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
forced diuresis. A committed dose to soft tissue was obtained from measuring the concentration and rate of excretion of tritium in her urine. Dicentric yields were measured in blood samples taken at various times after the event, and data from 40–50 days were used for biological dosimetry as by then all committed dose ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
of DNA which can be used as probes to particular part of the genome and then by attachment of various fluorochromes to highlight or ‘paint’ the regions in different colours. Translocations are seen as coloured rearrangements in a fluorescence microscope (shown in Figs 26 and 27). FIG. 26. Human metaphase with coloured ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
FIXING PROCEDURES The procedures for obtaining blood, culturing the lymphocytes and harvesting fixed cells are similar to those described for the dicentric assay (Sections 9.1 and 9.2). Although translocations are stable through mitosis, it is still good practice to carry out the analysis on M1 metaphases. This is part...	{ "page_id": null, "source": 7334, "title": "from dpo" }
the effect of high LET radiations and therefore these methods have particular applications for researching radiation quality effects. For most retrospective biological dosimetry applications it is sufficient to detect just inter-chromosomal translocations and ideally mFISH can provide the maximum information from each...	{ "page_id": null, "source": 7334, "title": "from dpo" }
vivo during immunological development and may thus confound the quantification of a radiation effect [171, 172]. For retrospective biological dosimetry a single colour FISH for a triple cocktail of target chromosomes appears to be sufficient. Multiple colour painting of the triplet increases the detection efficiency (i...	{ "page_id": null, "source": 7334, "title": "from dpo" }
acentrics, are constant with time [64, 174]. Therefore it is recommended to record whether each translocation occurs in a stable or unstable cell. > 10.3.2. Nomenclature and recording data To describe the chromosome aberrations detected by painting two specific nomenclature systems were developed independently, and des...	{ "page_id": null, "source": 7334, "title": "from dpo" }
However, it can be used with dual and triple paint patterns but each painted chromosome has to be scored in isolation irrespective of the colours of > 86 partners . This nomenclature has considerable uses in mechanistic studies, particularly, for example, in understanding complex rearrangements. A more conventional ter...	{ "page_id": null, "source": 7334, "title": "from dpo" }
pieces appeared unrejoined. For example, t(Ba) seen with t(Ab) is regarded as a simple complete or two-way translocation, and either pattern alone is regarded as a simple incomplete or one-way translocation when seen alone in a metaphase, sometimes with an associated painted acentric, t(Ba) plus ace(b). Complexes are r...	{ "page_id": null, "source": 7334, "title": "from dpo" }
approximation. However, there is a consensus that using the (DNA content) in the Lucas formula, larger chromosomes may tend to be overestimated in their participation in simple exchange aberrations compared to the smaller ones [187, 188]. Therefore, the use in the Lucas formula of the (DNA content) 2/3 rather than the ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
translocations. Therefore, to obtain the full genome translocation yield the observed yield is divided by 0.36. 10.4.2. Two colour painting Suppose a fraction, f 1 , is painted red, another fraction, f 2 , is painted green and (1 – f 1 – f 2 )= f 3 is counterstained blue. There will be: f12 red–red exchanges f22 green–...	{ "page_id": null, "source": 7334, "title": "from dpo" }
sample from the accidentally irradiated subject or from a population study group is unavailable, and therefore an assumed value based on generic survey data has to be used. Ideally a laboratory should develop its own control database but this is an extensive undertaking given that it would have to cover a number of con...	{ "page_id": null, "source": 7334, "title": "from dpo" }
from the 30–39-year-age group (p 31 ppm) Kim et al. Smith et al. (< 31 ppm) Zhang et al. Industrial pollution Beskid et al. Beskid et al. Sram et al. Heavy metals Maeng et al. (Chromium, smokers only) Dulout et al. (Arsenic) Doherty et al. (Chromium) Maeng et al. (Chromium, Non-smokers only) Only alcohol ten...	{ "page_id": null, "source": 7334, "title": "from dpo" }
some studies [202–204]. All three reported a significant effect when they studied only the t (8; 21) and t (14;18) translocation rates. However, 3 studies were identified in which the translocations between those chromosomes and all the others were examined, and none showed significant results. Substances that are used...	{ "page_id": null, "source": 7334, "title": "from dpo" }
of mutagenic substances. Fig. 32 illustrates the impact of the factors studied on the rate of translocations as a function of the type of factor, of the exposure, and of the studies. > 0510 15 20 25 30 35 40 > Burim, 2004 Badr, 1982 Ramsey, 1995 Pressl, 1999 Bothwell, 2000 Tucker, 2003 Whitehouse, 2005 Beskid, 2007 Van...	{ "page_id": null, "source": 7334, "title": "from dpo" }
or benzene are chronic. Exposures are designated as chronic when the individual is exposed to the genotoxic agent for all or a significant part of their life span (lifestyle or occupational exposure). Fig. 32 also shows that the translocation rates encountered in populations exposed to alcohol, smoking, and pesticides ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
makes them more suited for retrospective biological dosimetry. The persistence of the translocation frequency has long been a matter of discussion. Several years after the Goiânia accident in Brazil, the frequency of translocations was found to be lower than the frequency of dicentrics observed just after the exposure ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
for doses below 1–3 Gy but a decrease was observed after higher doses [217, 218]. In cancer patients treated with radiotherapy, a clear reduction of the yield of translocations with time post irradiation was observed, which was more pronounced in persons with a higher initial frequency of translocations. [219–222]. A p...	{ "page_id": null, "source": 7334, "title": "from dpo" }
this study taken with the theoretical likelihood that after a long period of time only stable cells will remain, suggests that to consider the yield of translocations in stable cells is more appropriate than the yield of translocations in all cells. This can only be finally resolved by good follow-up studies with FISH ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
curves have enough scoring in the low dose range to have obtained a sufficiently reliable linear coefficient with a small confidence range . To construct a linear dose relationship, several dose points below 1 Gy each with a large number of cells need to be scored and this comprises a considerable workload. In the inte...	{ "page_id": null, "source": 7334, "title": "from dpo" }
where cells containing unstable aberrations will be eliminated. Retrospective dosimetry assumes that these are not major confounders and the recent literature suggests that this is of no practical importance . In conclusion, dose reconstruction on the basis of translocations in stable cells is an established method bu...	{ "page_id": null, "source": 7334, "title": "from dpo" }
Chernobyl accident, and all were treated for symptoms of the delayed stage of the cutaneous radiation syndrome. These studies began in 1991 and follow-ups were performed until 1994 [212, 233, 234]. In 1991, biological dose equivalent estimates were determined, either by measuring the frequency of dicentric and ring chr...	{ "page_id": null, "source": 7334, "title": "from dpo" }
translocations. However, by contrast, a significant difference was found for four workers irradiated during the Oak Ridge (USA) Y-12 accident in 1959, where some years later the translocation frequencies were substantially below expected values . A pilot study carried out in 1994 of about 60 personnel recruited from Es...	{ "page_id": null, "source": 7334, "title": "from dpo" }
from 73 radiation exposed residents from settlements along the Techa river. The study group comprised two subgroups living in settlements either 7 to 60 km or 78 to 148 km downstream from the facility. Both were distinguished from controls, and significantly higher mean translocation frequencies were observed . Biologi...	{ "page_id": null, "source": 7334, "title": "from dpo" }
dicentric yields consistent with a disappearance half-time of 3.3 years. Six and eleven years after the accident, FISH dosimetry was attempted using the combined yields of one- and two-way translocations. On the first occasion, one laboratory made the analysis by single colour painting chromosomes #1, 2 and 4, and for ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
after radiation exposure (from 1992 onwards) at higher doses (>1 Gy) were two to three times lower than the initial dicentrics determined in 1987. For exposure levels estimated to be <0.9 Gy small differences were found between the frequencies of translocation and the initial dicentric yields. The accuracy of these dos...	{ "page_id": null, "source": 7334, "title": "from dpo" }
after the accident indicated that scoring translocations in stable cells appeared to abolish the decline in translocations observed in all cells. In stable cells, the yield of translocations was independent of time during the first years of follow-up . Istanbul accident In Section 9.7.5.6, a case is described where sev...	{ "page_id": null, "source": 7334, "title": "from dpo" }
considered to be quite adequate. Georgian accident Eleven young frontier guards were accidentally exposed to one or several 137 Cs sources with activity not exceeding 150 GBq, at the Lilo military training centre. The sources were intended for training and instrument calibration purposes. The victims were irradiated fo...	{ "page_id": null, "source": 7334, "title": "from dpo" }
the FISH translocations assay was also carried out, considering all cells and not confined to stable cells only. Three pairs of chromosome (# 2, 4 and 12) painted together with a pan-centromeric probe. For person 2 no difference was seen in the doses estimated by using dicentrics or translocations yields (Table 13). Fo...	{ "page_id": null, "source": 7334, "title": "from dpo" }
aberrations. The later FISH data are possibly indicating the dose received by the bone marrow stem cells. > 101 11. PREMATURE CHROMOSOME CONDENSATION (PCC) ANALYSIS Biological dosimetry is generally performed by analysing dicentrics and/or translocations at the first mitosis following in vitro PHA blastic transformatio...	{ "page_id": null, "source": 7334, "title": "from dpo" }
small spared fraction (as low as 5%). The assay similarly could also be better able to quantify small localized burns from partial body exposures. > 11.1.1. Cell culture and cell fusion conditions 11.1.1.1. Using CHO mitotic cells Chinese hamster ovary (CHO) mitotic cells should be prepared before performing the PCC an...	{ "page_id": null, "source": 7334, "title": "from dpo" }
(ratio 5:1) that possess a mitotic promoting factor in the presence of PEG. The fusion process takes only 4 min (1 min in PEG alone, and then wash medium F-10 should be added gradually). This is followed by a one hour incubation in complete medium with Colcemid at 37°C [67, 72, 251]. 11.1.1.5. Fixation procedures In pr...	{ "page_id": null, "source": 7334, "title": "from dpo" }
some fragments arrowed produced by the mitotic fusion method. (2) Dicentric analysis using C banding. In addition to chromosome breaks, dicentrics can also be visualized. For this, slides should be pretreated with barium hydroxide and salt solution, (Section 9.3.3) followed by Giemsa staining, which highlights the cent...	{ "page_id": null, "source": 7334, "title": "from dpo" }
annotation of digitized images. The microscope stage coordinates of PCC spreads on slides should be recorded and the selection method of candidate PCC spreads for scoring should not introduce bias to distort aberration yields. > 107 Analysis involves counting the number of chromosome elements, which appear as single ch...	{ "page_id": null, "source": 7334, "title": "from dpo" }
concept to the Qdr method introduced by Sasaki and Miyata (see Section 9.7.4.3). Following C banding or using a pan-centromeric probe and chromosome specific DNA libraries employing the FISH technique, slides can be scored for the presence of dicentrics and/or translocations (see Fig. 37), recorded and analysed, as de...	{ "page_id": null, "source": 7334, "title": "from dpo" }
. 11.2.2. The PCC ring assay Among the chemically-induced PCC methods for biological dosimetry, a simple and useful procedure is the scoring of rings in Giemsa-stained chromosomes. This technique still requires the lymphocytes to be cultured and the method, described by Kanda et al. recommends 48 hours cultures. It th...	{ "page_id": null, "source": 7334, "title": "from dpo" }
very high-dose exposure, isolating lymphocytes is strongly recommended. The standard protocol for PCC induction is that okadaic acid (500 nM) or calyculin A (20–50 nM) is added to the cultures during the final hour and this will therefore produce a mixture of PCC cells in all stages of the first cell cycle. However, th...	{ "page_id": null, "source": 7334, "title": "from dpo" }
pooled. A circular shaped chromosome is scored as a PCC ring. The centromeres are not clearly visualized in PCC cells stained just with Giemsa so that PCC rings are not classified into centric or acentric forms. Just as with dicentrics, (Section 9.7.4.3) the analysis of the intercellular distribution of PCC rings compa...	{ "page_id": null, "source": 7334, "title": "from dpo" }
was specially defined for characterizing high dose exposure as a product of absorbed organ dose and RBE in order to evaluate onset of deterministic health effects . The RBE of 200 kV X rays is set to 1. The unit of RBE-weighted dose is J kg -1 and is called in the gray-equivalent (Gy-Eq). For the most highly irradiate...	{ "page_id": null, "source": 7334, "title": "from dpo" }
and B) or γ-rays (patient C). b Ishigure et al . , where the neutron RBE is assessed at 1.5–2.0. 112 12. THE CYTOKINESIS-BLOCK MICRONUCLEUS (CBMN) ASSAY 12.1. BACKGROUND Ionizing radiation induces the formation of acentric chromosome fragments and to a small extent malsegregation of whole chromosomes. Acentric chromoso...	{ "page_id": null, "source": 7334, "title": "from dpo" }
of cell divisions occurring in vivo . One might therefore expect that some may already contain MN. Thus, it has been shown that scoring MN in mononucleated lymphocytes in conventional blood smears could be particularly useful for monitoring genetic damage in chronically exposed populations [259–263]. Furthermore, scori...	{ "page_id": null, "source": 7334, "title": "from dpo" }
> 113 (Tf-Ret; CD71) . Evaluation of the reticulocyte assay in patients treated with radioiodine for thyroid cancer shows that the method may be of use for monitoring individuals after suspected accidental radiation exposure [270, 271]. 12.2. LYMPHOCITE CULTURE FOR CBMN ASSAY The lymphocyte culture method is similar to...	{ "page_id": null, "source": 7334, "title": "from dpo" }
staining intensity. (d) The two nuclei within a BN cell may be unconnected or may be attached by one or more fine nucleoplasmic bridges, which are no wider than 1/4th of the nuclear diameter. (e) The two main nuclei in a BN cell may touch but ideally should not overlap each other. A cell with two overlapping nuclei can...	{ "page_id": null, "source": 7334, "title": "from dpo" }
2 500 1 + 2 1000 Remarks: 12.3.3. Criteria for scoring nucleoplasmic bridges A nucleoplasmic bridge (NPB) is a continuous DNA-containing structure linking the nuclei in a binucleated cell. NPB originate from dicentric chromosomes (resulting from misrepaired DNA breaks or telomere end fusions) in which the centromeres a...	{ "page_id": null, "source": 7334, "title": "from dpo" }
do not touch. 12.4. CBMN ASSAY DATA HANDLING 12.4.1. Dose–response The procedures for producing in vitro dose–response calibration curves are as previously described in Section 8. Many studies have shown that the number of radiation induced micronuclei is strongly correlated with radiation dose and quality [87, 272–275...	{ "page_id": null, "source": 7334, "title": "from dpo" }
workers [278–280]. These values are in agreement with the large scale study of Fenech of variables influencing baseline micronucleus frequencies: 0.31 MN/1000/year. For a female control population a more prominent increase of 0.58 MN/1000/year was found , again in agreement with Fenech : 0.52 MN//1000/year. Analysis o...	{ "page_id": null, "source": 7334, "title": "from dpo" }
probe, the majority of spontaneous MN were centromere positive (MNCM +ve )(respectively 73 and 71%) while most radiation induced MN were centromere negative (MNCM -ve ). The number of MNCM +ve only showed a very small increase with dose (respectively 3.7 and 5.3 MNCM +ve per Gy per 1000 BN cells). By manual scoring of ...	{ "page_id": null, "source": 7334, "title": "from dpo" }
nuclei are observed if the cell cycle time is much shorter than normal or the cytokinesis-blocking time is too long. 12.4.3.2. Calculating the NDI Five hundred viable cells are scored to determine the frequency of cells with 1, 2, 3 or 4 nuclei and the NDI is calculated by using the formula (36): N MMMMNDI 4321 432 +++...	{ "page_id": null, "source": 7334, "title": "from dpo" }
n is the sum of the total number of cells times their respective numbers of micronuclei (equivalent to the numerator of the NDI equation), and pi and pj are the probabilities of Mi` and Mj` which are equal to Mi ` or Mj` divided by n.Using the definition of covariance, it can then be shown that the variance of NDI is d...	{ "page_id": null, "source": 7334, "title": "from dpo" }
had volunteered a blood sample for an in vitro study of micronucleus expression following external exposure to graded doses of X rays (198 mGy/min). The background frequency (pre-treatment baseline) in the unexposed culture showed a mean frequency of 6.0 MN per 1,000 binucleated (BN) cells while mean values of 18.5, 29...	{ "page_id": null, "source": 7334, "title": "from dpo" }
such studies are not able to determine local dose to the target tissue which in this case was any residual thyroid cells plus metastases of thyroidal origin. 12.5.2. Biomonitoring studies After having been validated as an in vivo biomonitor in several patient studies, the CBMN assay as well as the CBMN-centromere assay...	{ "page_id": null, "source": 7334, "title": "from dpo" }
in 1986 were tested for their MN frequency in BN lymphocytes between 1989 and 1991 . In this study whole body counts for 134 Cs and 137 Cs were performed, so that the MN frequency could be related to body dose. Multiple regression analysis of the data from the 80 subjects showed that (a) the MN frequencies were signifi...	{ "page_id": null, "source": 7334, "title": "from dpo" }
after high doses. 12.5.3.3. Semipalatinsk Nuclear Test Site The Semipalatinsk nuclear test site area has been highly contaminated with radioactive fallout during 40 years of continual weapons testing (1949–1989). Individuals living near the site have been exposed to both internal and external radiation. Dicentric and M...	{ "page_id": null, "source": 7334, "title": "from dpo" }
observed in radiotherapy patients . 12.5.3.5. Large scale radiation accidents In case of large scale radiation accidents, when hundreds of people may be exposed, it is important to distinguish the severely exposed individuals ( ≥ 1 Gy), who require early medical treatment, from those less exposed. For this purpose, a r...	{ "page_id": null, "source": 7334, "title": "from dpo" }
blood handling station may be equipped with a large customized work deck, a bar-code reader for maintaining chain-of-custody of samples, robotic arms for liquid-handling and transporting of vacutainers, centrifuge tubes, and a wash station for pipette tips. The robot can also be integrated with both a cell viability an...	{ "page_id": null, "source": 7334, "title": "from dpo" }

Subsets and Splits

No community queries yet

The top public SQL queries from the community will appear here once available.