Ultrastructure of the thymus after gamma irradiation during inhibition of steroidogenesis

Experimental investigations on rats have shown that development of dyshormonal immunodepression after ionizing radiation in sublethal doses depends on indirect effect of corticosteroids. Inhibition of steroidogenesis corrects ultrastructural lesions of the thymus after gamma irradiation.     

The thymus of mice at different periods after irradiation with fast carbon ions

Irradiation of mice with energy-fast carbon ions 4.0 in dose impairs histological structure of thymus on the first day after the challenge. Non differentiated cell forms (blasts and large lymphocytes) and middle lymphocytes were most sensitive to the irradiation. As a result mitotic activity decrease was noted. Reparative process in thymus begins on d 22 after irradiation with carbon ions when stem cells obviously accumulate. At the same time mitotic activity intensifies. Although at distant terms T cells differentiation and formation are inhibited which is reflected in significantly reduced number small lymphocytes in thymus cortex and medulla on d 60 of postirradiation period as compared to that in control.     

The risk of contralateral breast cancer in daughters of women with and without breast cancer

We aimed to estimate the 15‐year and lifetime risks of contralateral breast cancer in breast cancer patients according to the age of diagnosis of the first cancer and the history of breast cancer in the mother. The risks of contralateral breast cancer were estimated for all 78,775 breast cancer patients in the Swedish Family‐Cancer Database (age at diagnosis of first breast cancer <70 years). The risk of experiencing a contralateral breast cancer within 15 years of diagnosis was 8.4% [95% confidence interval (CI): 8.1–8.7%] for women with an unaffected mother, was 12% (95%CI: 11–13%) for a woman with a mother with unilateral breast cancer and was 13% (95%CI: 9.5–17%) for women with a mother with bilateral breast cancer. In early‐onset diagnosed women (<50 years) with an unaffected mother, the risk of contralateral breast cancer until age 80 was 23% (95%CI: 20–26%) and for late‐onset (50–69 years) diagnosed women it was 17% (95%CI: 14–21%). In a woman with a mother with an early‐onset unilateral breast cancer, risk of contralateral breast cancer by age 80 was 35% (95%CI: 25–46%). Women with a mother with early‐onset bilateral breast cancer had 31% (95%CI: 12–67%) lifetime risk of contralateral breast cancer. The risk of contralateral breast cancer is higher for daughters of breast cancer patients than for daughters of women without breast cancer. Maternal cancer history and age at onset of first breast cancer in women should be taken into account when counseling breast cancer patients about their risk of contralateral breast cancer.     

Morphofunctional transformations in the thymus and lymph nodes after irradiation with a helium-neon laser

Morphological transformations occurring in the thymus and lymph nodes are studied in Wistar rats after irradiation of the thymus projection area and transcutaneous irradiation of peripheral blood with a low-energy helium-neon laser during a 7-day period. Irradiation of the thymus projection area stimulates lymphopoiesis in T-dependent zones of lymph nodes, while irradiation of peripheral blood increases lymph flow through lymph node parenchyma and activates B-dependent zones. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 123, No. 5, pp. 588–590, May, 1997     

The entry of the prothymocyte into the thymus after lethal irradiation and bone marrow transplantation. I. Seeding of bone marrow cells into the thymus

Bone marrow (BM) cells arrive in the thymus of lethally irradiated mice as early as three hours after bone marrow transplantation (BMT). They can be recognized by labeling of the injected cells with Hoechst 33342 (direct homing assay). In order to relate the immigrated BM cells to thymocyte precursor cells, direct homing and thymus repopulation experiments were compared. It was shown that homing of BM cells depends on the time between lethal irradiation and BMT, while it was previously shown that thymus repopulation does not. In addition, thymic immigrants were smaller than precursor cells committed to the T cell limeage (prothymocytes) and their progenitors. A cell population obtained from normal BM cells and enriched in stem cells (purified stem cells) was previously shown to repopulate the thymus similarly as BM cells from mice pretreated in vivo with 5-fluorouracil (FUBM). Both cell suspension showed a delayed thymus repopulation when compared to normal BM. This is indicative for a depletion of prothymocytes in these cell suspensions. In the direct homing assay, however, it was found that relatively many cells from FUBM seeded into the thymus, while purified stem cells did not. These results indicate that most if not all donor cells that are present in the thymus at three hours after BMT are not thymocyte precursor cells.     

Mortality from breast cancer after irradiation during fluoroscopic examinations in patients being treated for tuberculosis

The increasing use of mammography to screen asymptomatic women makes it important to know the risk of breast cancer associated with exposure to low levels of ionizing radiation. We examined the mortality from breast cancer in a cohort of 31,710 women who had been treated for tuberculosis at Canadian sanatoriums between 1930 and 1952. A substantial proportion (26.4 percent) had received radiation doses to the breast of 10 cGy or more from repeated fluoroscopic examinations during therapeutic pneumothoraxes. Women exposed to greater than or equal to 10 cGy of radiation had a relative risk of death from breast cancer of 1.36, as compared with those exposed to less than 10 cGy (95 percent confidence interval, 1.11 to 1.67; P = 0.001). The data were most consistent with a linear dose-response relation. The risk was greatest among women who had been exposed to radiation when they were between 10 and 14 years of age; they had a relative risk of 4.5 per gray, and an additive risk of 6.1 per 10(4) person-years per gray. With increasing age at first exposure, there was substantially less excess risk, and the radiation effect appeared to peak approximately 25 to 34 years after the first exposure. Our additive model for lifetime risk predicts that exposure to 1 cGy at the age of 40 increases the number of deaths from breast cancer by 42 per million women. We conclude that the risk of breast cancer associated with radiation decreases sharply with increasing age at exposure and that even a small benefit to women of screening mammography would outweigh any possible risk of radiation-induced breast cancer.