International journal of radiation biology and related studies in physics, chemistry, and medicine最新文献

A total of 1328 atomic bomb survivors in Hiroshima were studied to determine alterations in the number of blood lymphocytes belonging to T-cell subpopulations, the number of CD19 antigen-positive B cells and the number of Leu 7 and CD16 antigen-positive lymphocytes. Overall, with increasing age, significant decreasing trends in the numbers of some lymphocytes in T-cell subpopulations and of B cells were observed. Furthermore, the number of blood lymphocytes positive for CD5 antigen was significantly lower in the people exposed to radiation (greater than 1 Gy) in the older age group (more than 30 years old at the time of the bombing). A similar tendency for decreases in the numbers of CD4, CD8, and CD19 antigen-positive cells was observed in these older survivors, although the differences were not statistically significant. These results suggest that aging of the T-cell related immune system is accelerated in the irradiated people of advanced age. This may be explained by the age-related decrease in thymic function in those subjects who were older at the time of the bombing resulting in a decreased functional ability of the immune system after radiation injury. On the contrary, the number of Leu 7 or CD16 antigen-positive cells was found to be increased significantly in the older age group compared to the younger group, although there was little dependence on dose.

Human lymphocytes exposed to low doses of ionizing radiation from incorporated tritiated thymidine or from X-rays become less susceptible to the induction of chromatid breaks by high doses of X-rays. This response can be induced by 0.01 Gy (1 rad) of X-rays, and has been attributed to the induction of a repair mechanism that causes the restitution of X-ray-induced chromosome breaks. Because the major lesions responsible for the induction of chromosome breakage are double-strand breaks in DNA, attempts have been made to see if the repair mechanism can affect various types of clastogenic lesions induced in DNA by chemical mutagens and carcinogens. When cells exposed to 0.01 Gy of X-rays or to low doses of tritiated thymidine were subsequently challenged with high doses of tritiated thymidine or bleomycin, which can induce double-strand breaks in DNA, or mitomycin C, which can induce cross-links in DNA, approximately half as many chromatid breaks were induced as expected. When, on the other hand, the cells were challenged with the alkylating agent methyl methanesulfonate (MMS), which can produce single-strand breaks in DNA, approximately twice as much damage was found as was induced by MMS alone. The results indicate that prior exposure to 0.01 Gy of X-rays reduces the number of chromosome breaks induced by double-strand breaks, and perhaps even by cross-links, in DNA, but has the opposite effect on breaks induced by the alkylating agent MMS. The results also show that the induced repair mechanism is different from that observed in the adaptive response that follows exposure to low doses of alkylating agents.

A culture system was used to evaluate the radiosensitivity of CD4+ and CD8+ T cells, Leu 19+ cells, and B cells obtained from normal adult males. Unstimulated CD8+ lymphocytes (D0 = 55 cGy) were twice as radiosensitive as CD4+ cells (D0 = 115 cGy). B cells had an intermediate radiosensitivity (D0 = 100 cGy). Leu 19+ cells were much more radioresistant and expressed a D0 of 550 cGy. When lymphoid cells were irradiated 1 or 4 days before phytohemagglutinin (PHA) stimulation, they were more radiosensitive than if they were first stimulated with PHA and then irradiated. When lymphoid cells were irradiated 1 h after PHA stimulation each lymphocyte subset was characterized by an increase in the D0 to 150 cGy for B cells to 290 cGy for CD4+ cells, and to 240 cGy for CD8+ cells. In contrast, Leu 19+ cells exhibited a decrease in their D0 to 290 cGy after they were stimulated by PHA.

The blood lymphocyte population was examined in 34 patients who were treated with 131I for toxic or atoxic nodular goitre. One to three doses of 300-550 MBq of 131I were administered at 1-week intervals. Lymphocyte counts were found to be significantly reduced at both 1 and 6 weeks after treatment. This decrease was accompanied by a changed composition of the lymphocyte subpopulations. The frequency of lymphocytes expressing membrane receptors for C'3 (EAC-rosette forming cells) was significantly reduced at 1 and 6 weeks following 131I administration. At 6 weeks there was a small but statistically significant increase of the frequency of T cells as identified by Leu 1 monoclonal antibodies. This was essentially due to an increased proportion of helper/inducer T cells as identified by Leu 3 monoclonals. 131I treatment also decreased the capacity of lymphocytes to secrete immunoglobulins (Ig) when stimulated with pokeweed mitogen (PWM). The greatest effect was observed for IgM. Secretion of IgG and IgA were less reduced. Mitogenic stimulations of lymphocytes with phytohemagglutinin (PHA) and concanavalin A were not significantly changed. It is concluded that these findings, with the exception of mitogen reactivity, are largely similar to those occurring following external radiation therapy for cancer. It is suggested that blood lymphocytes passing through the continuously irradiated gland are damaged mainly by beta-rays. The effect of 32P treatment on the blood lymphocyte population was examined in 16 patients with polycythemia vera. Before treatment the lymphocyte counts were within the normal range but the expression of certain membrane structures, as identified by monoclonal antibodies against total T cells (Leu 1 and 4), helper/inducer (Leu 3) and suppressor/cytotoxic T cells (Leu 2), were slightly decreased. Moreover, mitogenic responses of the lymphocytes to PHA and PWM-induced Ig secretion were impaired. Following a single oral dose of 32P (150-305 MBq), which normalized the production of erythrocytes and/or platelets, the blood lymphocyte counts were reduced by approximately 40 per cent 12 weeks after treatment. Examination of subsets demonstrated that the proportion of B-cells, as identified by B1 monoclonal antibodies, was decreased by the highest relative extent. On the other hand, lymphocytes expressing the above-mentioned T cell markers were somewhat increased. 32P treatment markedly increased PHA reactivity but it further reduced PWM-induced Ig secretion. The latter observation was in agreement with the finding that serum concentrations of Ig were reduced after treatment.

Thymocytes are highly radiosensitive and show 'interphase death' within a few hours after low doses of irradiation. However, the mechanisms responsible for this type of death remain ill-defined. Separation of the dead thymocyte fraction from irradiated thymocyte suspensions by centrifugation on Percoll gradients provided homogeneous populations of dead cells suitable for detailed study. Using this method, radiation-induced interphase death of thymocytes was found to involve a sharp but transient increase in buoyant density, concomitant with the appearance of distinctive morphologic changes which included disappearance of microvilli and blistering of the cell surface. The chromatin in the dead cells had a molecular weight sufficiently low to resist sedimentation, and consisted of short oligonucleosome chains. We were unable to detect populations of cells intermediate between the dead and normal in the above characteristics. Interphase death thus involves a discrete, abrupt transition from the normal state and is not merely the consequence of progressive and degenerative changes. Furthermore, immediate cessation of development of interphase death by cycloheximide suggested a possible involvement of protein synthesis on this transition step.

The classical types of generalized autoimmune disease in man are systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Several murine strains which develop SLE and sometimes RA-like diseases are now available. They should help in the understanding of the etiopathology of SLE and RA. Basically two main therapeutic strategies which use solely irradiation have been tried; one being sublethal whole-body irradiation (WBI) and the other fractionated total lymphoid irradiation (TLI). Other protocols which combine lethal WBI and stem cell transplantation have often been attempted. It was regularly found that the bone marrow transplant (BMT) dictates the immune status of the recipient. This paper reviews the data published about NZB, NZB/W, BXSB and MRL mice in this context.

The majority of radiation-induced murine myeloid leukaemias are characterized by deletion and/or translocation of an interstitial region of chromosome 2, and there is evidence that such events may occur very early in myeloid leukaemogenesis. Analyses presented and discussed here on the structure and function of two possibly relevant chromosome 2 encoded genes (c-abl and beta 2M) lead to the preliminary conclusion that neither are directly involved nor activationally changed by the characteristic chromosome 2 rearrangements.

Preliminary studies on the long-term effects of prenatal and early postnatal irradiation on the immune response to arsonate were performed using A/J mice. Pregnant mice were irradiated (0.5 Gy, X-rays) or sham-irradiated on a single occasion during gestation (between day 5 and 18 post-conception). Alternatively, newborn mice received the same treatment between day 2 and 7 after birth. Mice were immunized with keyhole limpet haemocyanin-arsonate (KLH-Ars) in adjuvant from 2 months after birth. The levels of specific antibodies to arsonate (anti-Ars) were measured by radioimmunoassay. In addition, the Ars-related cross-reactive idiotype (CRIA) was measured by the haemagglutination technique. In the primary response the titre of anti-Ars was reduced in animals that had been irradiated between day 12 and 15 of gestation. In the second response, in contrast, they had increased levels of anti-Ars. After immunization with KLH-Ars, high levels of CRIA were observed in all groups. However, in mice irradiated 18-20 days after conception the level of CRIA was often much higher than the level of anti-Ars, indicating that a large proportion of the CRIA-positive molecules were not specific for Ars. Thus, in this particular case, some specificity of the immune response was lost after irradiation. The expression of recurrent idiotypes may be a sensitive indicator of immunological perturbations after irradiation.

In order to better understand the apparent physiologic up-regulation in response to low levels of potentially lethal insults, murine T lymphocytes were analysed for functional and phenotypic alterations after exposure to 0.005 Gy/day, 0.01 Gy/day and 0.04 Gy/day in groups of ad-libitum-fed and calorie-restricted mice. These studies were conducted in two strains of mice: the long-lived and immunologically normal C57Bl/6 +/+ and the congenic short-lived immunologically depressed C57Bl/6 lpr/lpr. Whole-body exposure to 0.01 Gy/day and 0.04 Gy/day for an extended period of 20 days was associated with an increase in splenic proliferative response and with shifts in the proportions of T cell subpopulations in the thymus and spleen of both strains. Caloric restriction independently altered functional activity and T cell subpopulations in the same direction as low dose rates of ionizing radiation. Although the dose-response augmentation in proliferative activity was similar in the two strains, observed alterations in thymic and splenic T cell subpopulations were clearly different, suggesting that different mechanisms were responsible for immune enhancement in each strain.

The dose-response for radiation-induced chromosome aberrations in human lymphocytes is usually fitted to the quadratic model. This assumes that the slope is essentially linear at low doses. Empirical observations of linearity at less than 200 mGy are, however, sparse. Some data have been published indicating a non-linear (threshold) response and these are reviewed. In particular one study with X-rays showed a plateau in response up to 50 mGy and with a significant dip below the control level at 4 mGy. The mechanism proposed to explain non-linearity is that low doses stimulate the enzymic repair capability of lymphocytes. Preliminary data are presented from a large experiment by six laboratories in which the low dose-response for X-rays has been re-examined. The plateau in the dose-response relationship, if it exists, does not extend to doses above approximately 10 mGy. No irradiated cells yielded aberration levels significantly below the control. Over the range 0-300 mGy the response can be fitted to a linear regression. There are, however, variations in sensitivity between cells from different donors. An unexpected finding was that some lymphocytes contained greater than 1 exchange aberrations. This may indicate a small subset of cells that are especially susceptible to the induction of aberrations by low doses.