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1.
Cell Cycle Kinetics Following UVA Irradiation in Comparison to UVB and UVC Irradiation 总被引:1,自引:0,他引:1
Annemarie de Laat Marloes van Tilburg Jan C. van der Leun Willem A. van Vloten Frank R. de Gruijl 《Photochemistry and photobiology》1996,63(4):492-497
Abstract— There is limited information about the carcinogenic effect of longwave ultraviolet radiation (UVA: 315-400 nm). In particular very little is known about the relevant genotoxic damage caused by physiological doses of UVA radiation. A general response of cells to DNA damage is a delay or arrest of the cell cycle. Conversely, such cellular responses after UVA irradiation would indicate significant genotoxic damage. The aim of this study is to compare cell cycle kinetics of human fibroblasts after UVC (190-280 nm radiation), UVB (280-315 nm radiation) and UVA irradiation. Changes in the cell cycle kinetics were assessed by bivariate flow cytometric analysis of DNA synthesis and of DNA content. After UVC, UVB or UVA irradiation of human fibroblasts a suppression was seen of bromodeoxyuridine (BrdU) incorporation at all stages of S phase. The magnitude of this suppression appeared dose dependent. Maximum suppression was reached at 5-7 h after UVB exposure and directly after UVA exposure, and normal levels were reached 25 h after UVB and 7 h after UVA exposure. The lowered BrdU uptake corresponded with a lengthening of the S phase. No dramatic changes in percentages of cells in G1 , S and G2 /M were seen after the various UV irradiations. Apparently, UVA irradiation, like UVB and UVC irradiation, can temporarily inhibit DNA synthesis, which is indicative of genotoxic damage. 相似文献
2.
TRANSMISSION OF HUMAN EPIDERMIS AND STRATUM CORNEUM AS A FUNCTION OF THICKNESS IN THE ULTRAVIOLET AND VISIBLE WAVELENGTHS 总被引:8,自引:1,他引:8
Wiel A. G. Bruls H. Slaper Jan C. van der Leun L. Berrens 《Photochemistry and photobiology》1984,40(4):485-494
Abstract The dependence of radiation transmission on sample thickness was studied in isolated samples of human stratum corneum and full-thickness epidermis. The investigation also included samples of skin repeatedly exposed to UV-B. Transmission was measured in the ultraviolet and in the visible from 248–546 nm. Two methods, one microscopic and the other mechanical, were used to measure thickness. There was a good correlation between the results.
The dependence of transmission on thickness in these samples could be described satisfactorily by an exponential function, implying that the Lambert-Beer law is approximately valid. Thus, a single parameter, such as the half-value layer ( d½ ), is sufficient to characterize absorption in the skin samples.
Water content of the isolated stratum corneum was influenced by maintenance conditions: samples floating on water containing a small amount of NaCl were more hydrated than samples floating on a more concentrated salt solution, or stored in air. Changes in water content of the samples resulted in changes of thickness and, to a lesser extent, of transmission. Approximate in vivo values of d½ were computed after estimating the in vivo water content of stratum corneum.
Differences found in the shape of the transmission spectra of stratum corneum and full-thickness epidermis may reflect differences in chemical composition. The influence of wetting of the skin on its sensitivity to sunlight is explained in a new way. 相似文献
The dependence of transmission on thickness in these samples could be described satisfactorily by an exponential function, implying that the Lambert-Beer law is approximately valid. Thus, a single parameter, such as the half-value layer ( d
Water content of the isolated stratum corneum was influenced by maintenance conditions: samples floating on water containing a small amount of NaCl were more hydrated than samples floating on a more concentrated salt solution, or stored in air. Changes in water content of the samples resulted in changes of thickness and, to a lesser extent, of transmission. Approximate in vivo values of d
Differences found in the shape of the transmission spectra of stratum corneum and full-thickness epidermis may reflect differences in chemical composition. The influence of wetting of the skin on its sensitivity to sunlight is explained in a new way. 相似文献
3.
Analysis of the γ-ray angular distributions measured at 16 36S(p, γ)37Cl resonances yields the spins and/or parities of 21 bound states of 37Cl in addition to the resonance spins. Among the latter are four resonances. For several other bound states the possible spins have been restricted. Multipolarity mixing ratios have been deduced from the same data. Lifetimes (or lifetime limits) of 29 bound states have been deduced from DSA measurements.This extensive experimental information allows a comparison with the results of a shell-model calculation for both the even- and odd-parity states of 37Cl. In this calculation either zero, one or two particles are promoted from the 2s or 1d to the 1f or 2p subshells. Up to an excitation energy of about 5 MeV a one-to-one correspondence is found between experimental and calculated levels. 相似文献
4.
5.
A precision measurement of the 26Alm---26Mg mass difference brings the anomalously low ft value for the super-allowed pure Fermi transition 26Alm(β+)26Mg closer to the average of the ft values of six similar β+ transitions. The anomaly, however, is still significant. 相似文献
6.
G Kelfkens H van Weelden F R de Gruijl J C van der Leun 《Journal of photochemistry and photobiology. B, Biology》1991,10(1-2):41-50
To gain an insight into the relationship between the time in which a daily UV dose is delivered and its carcinogenic effectiveness, the following experiment was performed. Three groups of 24 albino hairless mice (Skh-hr1) were exposed to the same daily dose of UVB radiation (600 J m-2; Philips TL12). The exposure times for the three groups were 1.25, 4 and 12 h per day. A fourth unirradiated group served as a control. All animals exposed to UVB developed multiple skin tumours, whereas the control animals did not develop any observable tumours. Tumour development in the groups exposed for 4 and 12 h was virtually identical. Tumour development was significantly faster in the groups exposed for 4 and 12 h per day than in the group exposed for 1.25 h: the median tumour induction time was reduced by 12%. In terms of the effective dose, this is equivalent to a 25% increase in effectiveness for the 4 and 12 h groups relative to the 1.25 h group. In conclusion, the present experiment shows that prolongation of the exposure duration increases the carcinogenic efficacy of UVB radiation. 相似文献
7.
The lifetimes of the 23Na levels at Ex = 7.89 and 4.43 MeV have been measured in resonant-absorption experiments as τm = 220 ± 17 and 350 ± 70 as, respectively. In both cases the γ-ray source was a 30Si(p, γ)31P resonance. The implications of these results for the application of the resonant-absorption technique are discussed. 相似文献
8.
J.W. Maas E. Somorjai H.D. Graber C.A. Van Den Wijngaart C. Van Der Leun P.M. Endt 《Nuclear Physics A》1978,301(2):213-236
Particle energies have been measured for resonances in the 27Al(p, γ)28Si and 24Mg(α, γ)28Si reactions with an accuracy of 0.5 × 10?4 and 1 × 10?4, respectively. The Ep = 991.88 ± 0.04 keV27Al(p, γ)28Si resonance served as calibration point. From these data the Q-value of the reaction 27Al(p, α)24Mg has been determined as 1600.14 ± 0.21 keV. Excitation energies of 28Si levels have been measured with the 27Al(p, γ)28Si reaction; the reaction energy is Q = 11584.5 ± 0.4 keV.Of 33 resonances observed in the 24Mg(α, γ)28Si reaction (Eα = 1.5–3.8 MeV), energies, strengths and γ-ray decay have been measured; five of these resonances had not been reported previously. The γ-ray angular distribution measurements at three resonances yield the resonance Jπ values and the mixing ratios of the strongest transitions involved in the decay. The 10.38 MeV level has Jπ = 3+, T = 1. The arguments on which T-assignments can be based are critically reviewed. These arguments are used to assign T = 1 character to 19 states of 28Si. 相似文献
9.
UV-carcinogenesis 总被引:1,自引:0,他引:1
J C van der Leun 《Photochemistry and photobiology》1984,39(6):861-868
10.
WielA. G. BrulsJoop A. J. Faber†Jan C. van der Leun 《Photochemistry and photobiology》1982,36(5):531-535
The minimal erythema dose (MED) is often used as a quantity by which the influence of certain treatments of the skin can be measured. Differential measurements are performed by assessing the difference of the MED on the skin treated in some way and the untreated skin.
As the MED-measuring scale is discrete, the question is sometimes raised whether it is possible to measure differences smaller than one scale unit. In the present paper it is shown that this is indeed possible; in principle the discreteness of the scale does not impose any restriction on the smallest value of the difference that can be measured. The discreteness of the scale introduces an extra random variation into the measurement. This variation is estimated theoretically. It is automatically included in the usual error analysis.
The discreteness variance is small when compared to other variance components, which are computed from an analysis of variance of actual experiments. Reducing the discreteness variance, by reducing the dose decrement of the MED-measuring scale, therefore, does not enhance the overall accuracy considerably. Finally, it is found that the assessments of the MED by the various observers do not differ significantly from each other, and that multiple assessments do increase the accuracy, especially for small effects. 相似文献
As the MED-measuring scale is discrete, the question is sometimes raised whether it is possible to measure differences smaller than one scale unit. In the present paper it is shown that this is indeed possible; in principle the discreteness of the scale does not impose any restriction on the smallest value of the difference that can be measured. The discreteness of the scale introduces an extra random variation into the measurement. This variation is estimated theoretically. It is automatically included in the usual error analysis.
The discreteness variance is small when compared to other variance components, which are computed from an analysis of variance of actual experiments. Reducing the discreteness variance, by reducing the dose decrement of the MED-measuring scale, therefore, does not enhance the overall accuracy considerably. Finally, it is found that the assessments of the MED by the various observers do not differ significantly from each other, and that multiple assessments do increase the accuracy, especially for small effects. 相似文献