[Effects of ionizing radiation on the embryo and fetus]. / Vliianie na ionizirashtite l'cheniia v'rkhy embriona i fetusa.

The developing embryo and fetus are extremely sensitive to ionizing radiation. The main effects of radiation on he human embryo and fetus are: growth retardation, prenatal or neonatal death, congenital malformations and mental retardation. The incidence of these radiation effects at different stages of gestation, the relations with absorbed doses and threshold doses are discussed. Epidemiological data that reveal high susceptibility to carcinogenic effects of radiation during in utero life are presented. A dose of 0.1 Gy (10 rad) to the embryo and fetus is recommended as a threshold dose, above which a therapeutic abortion should be considered. Diagnostic radiation exposures will reach this level in a very rare cases. The threshold dose, which is an indication for pregnancy termination must be flexible, in a large tolerance, depending on other possible risks of the pregnancy as well as the personality of the future parents.

Frequency of micronuclei in lymphocytes from in vitro gamma-irradiated human peripheral blood.

The micronucleus assay technique of Högstedt was used in studies of time-response and dose-response to single acute 137Cs gamma-ray exposure of human blood in vitro. Time-response following a 2 Gy dose was examined at postradiation times 48, 72, 77, 96, and 120 hours; micronucleated lymphocyte frequencies peaked at 77 hours, dropping insignificantly at 96 hours. Unirradiated control blood showed relatively low values peaking at 77 hours. The dose-response data obtained at 77 hours with single irradiations at dose levels 0.5, 1, 2, or 4 Gy were a good fit to a linear-quadratic relationship: Y = 0.5 + 1.17D + 0.338D2 (Y, micronucleated lymphocyte percentage; D, radiation dose in Gy). The evidence obtained and the rapidity and case of assay performance give us ground to assume that the method is applicable as a initial screening test to estimate the cytogenetic effect of human exposure in vivo.

[Cytogenetic effect of thaliblastine in a culture of human peripheral blood lymphocytes]. / Tsitogenetichekii éffekt taliblastina v kul'ture limfotsitov perifericheskoi krovi cheloveka.

The mutagenicity of thaliblastine (Bulgarian potential antitumor drug) was investigated in vitro in lymphocytes from healthy donors, and in vivo in lymphocytes of oncological patients after thaliblastine administration. No increase in the rate of chromosome aberrations was noted with increasing thaliblastine concentrations in vitro and in the course of therapy in vivo. Some polyploid metaphases were found in the lymphocytes of the patients treated with thaliblastine, as a result of the statmokinetic effect of the drug. Thaliblastine exerts extraordinarily slight mutagenic effect, as compared with other cytostatics.

[Mutagenic effect of the cytostatic drug thaliblastine on rat bone marrow cells when administered alone and in combination with radiation]. / Issledovanie mutagennogo éffekta tsitostatika taliblastina na kletkakh kostnogo mozga krys pri razdel'nom i sochetannom s oblucheniem vozdeistviiakh.

The cytogenetic analysis was performed in the bone marrow cells of Wistar rats treated with a therapeutic dose of thaliblastine (250 mg/kg) and exposed to gamma-rays (2 Gy). Thaliblastine alone induced chromosome aberrations and polyploid cells. The latter were the result of the stathmokinetic effect of the drug. In contrast to gamma-radiation of 2 Gy thaliblastine elicited a minor mutagenic effect. The cytogenetic effect of the combined treatment is greater than the sum of the two agents delivered separately, the maximum effect of radiation and thaliblastine being exhibited on the 8th and the 12th hour, respectively. The difference between the sum of aberrations after separate treatments and the yield of aberrations after the combined treatment is due to chromatid fragments.