Mathematical models of strontium-90 behavior in a "water--fresh-water fish spawn" system in several individual cases of radionuclide entry into bodies of water

A group of 72 gilts, aged between eight and nine months, were treated 20 days each by administration of 5 g Suisynchronpr?mix (Zinc Metallibur/Sui), followed by 24-hour treatment with 750 IU PMS (Prolosanserum). Fifty per cent of the group received 500 IU per animal of HCG (Gonabion) at 11 a.m., on the fourth day after Sui. All animals were artificially inseminated at 3.30 p.m. on the fifth day after Sui. and at 7.30 a.m. on the sixth day after Sui. Laparotomy was performed on 50 per cent of the HCG-treated and untreated animals in the afternoon of the sixth day after Sui. Animals with no recordable ovulation had to undergo another laparotomy in the morning of the seventh day. The above approach resulted in regrouping by four therapeutic categories: 1. HCG with laparotomy, 2. No HCG, 3. HCG with no laparotomy, 4. No HCG and no laparotomy. In the afternoon of the sixth day after Sui (51-56 hours after HCG) ovulation had begun in all 17 measurable animals of the first group, but only in one of 18 animals of the second. The animals were slaughtered between the seventh and twelfth days after Sui, and the following ovulation percentages were established: 100 per cent in the first group, 83.3 per cent in the second, 55.6 per cent in the third, and 72.2 per cent in the fourth. The animals that had been given HCG treatment (Groups 1 and 3) were found to be superior in terms of percentual ovulation to the untreated animals (Groups 2 and 4). However, Group 2 was the only group that had been exposed to the extraordinary stress of two laparotomies, and this should be borne in mind for evaluation. Ovarian cysts (more than 10 mm) began to develop on the eighth day on the laparotomised groups (1 and 2) and on the tenth day on the non-laparotomized groups (3 and 4). Cysts developed in 41.1 per cent of all animals in Group 1, 38.9 per cent in Group 2, 27.8 per cent in Group 3, and 22.2 per cent in Group 4. Therefore, cyst formation is thought to have been stimulated by laparotomy. Ovocyte tests suggested fertilisation of all animals in the first group. The embryonation rates of the second, third, and fourth groups are discussed with reference to the dates of insemination.     

Effect of sterols on melittin incorporation into liposomal membranes

Effects of various sterols on the values of intensity, spectrum position and polarization of tryptophan fluorescence (P) of melittin incorporated in lecithin liposomes at different lipid/protein molar ratios (Ri) were studied. A difference in sterol effects has been revealed at the values of Ri > 5. At Ri < 5, fluorescence parameters were determined mainly by melittin in the aqueous solution. Assuming that melittin was bound to lecithin, the lecithin/melittin binding ratio was found to be in the range of 25-50. Unlike cholesterol and stigmasterol, the incorporation into membranes of ergosterol and 7-dehydrocholesterol produced a decrease in the intensity of tryptophan fluorescence and an increase in the P value. This difference might result from the presence of an additional double bond in one of sterol rings of ergosterol and 7-dehydrocholesterol molecules. Analysis of the results obtained enabled us to suggest that the structure of the steroid B ring is responsible for the effect exerted by sterols on melittin-lipid interactions.     

Modulation of the antitumor activity of 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosoure a by O(6)-methyl-2'-deoxyguanosine--a new inhibitor of O(6)-alkylguanine-DNA-alkyltransferase

O6-Methyl-2'-deoxyguanosine (O6-MedG), a novel inhibitor of O6-alkylguanine-DNA alkyltransferase (O6-AGT), has been synthesized. The ability of O6-MedG to deplete the O6-AGT activity in leukemia L1210 and melanoma B16 cells in vivo has been studied. After intraperitoneal administration of O6-MedG to mice bearing leukemia L1210 or melanoma B16, the activity of O6-AGT in tumour cells decreased by 50%. Pretreatment of leukemia L1210 bearing mice with O6-MedG (200 mg/kg) 24 hours prior to ACNU (15 mg/kg) administration resulted in six out of seven 60-day survivors. Treatment of mice with ACNU (15 mg/kg) alone increased the life span by 200%. Treatment of melanoma B16 bearing mice with O6-MedG and 3 hours thereafter with ACNU resulted in a 50% inhibition of tumour growth, whereas the inhibiting effect of ACNU alone was 16%. There was no difference in leukemia growth when L1210/BCNU bearing mice were treated with O6-MedG followed by ACNU treatment. In vivo ACNU (15 mg/kg) produced a deep and prolonged inhibition of DNA, RNA and protein synthesis in leukemia L1210 cells. The DNA synthesis in leukemia L1210/BCNU cells was shown to recover more rapidly than in L1210 cells. The activities of DNA-polymerases alpha and beta and, especially, of O6-AGT were elevated in ACNU-resistant leukemia cells as compared with ACNU-sensitive cells. The activation of some repairing enzymes, such as O6-AGT, DNA-polymerases alpha and beta as well as increased levels of GSH may play a role in the development of drug resistance to ACNU.