Effect of heparin on the antiradiation activity of cystamine, decreasing with a reduction in radiation intensity

It was shown that a single injection of heparin (250 units/kg) 15 min and 24 h before irradiation potentiated a slight radioprotective effect of cystamine (dichlorohydrate, 170 mg/kg) which was registered after the administration thereof to mice 30 min before irradiation with an absolutely lethal dose at a dose rate of 0.0025 Gy/c.     

Radioprotective effect of pyrazolone derivatives]

The intraperitoneal injection of analgin (1000 mg/kg), antipurine (400 mg/kg), amidopyrine (100 mg/kg) 3 hours before the irradiation of mice in a dose of 800 R led to survival of 30 to 45% of the animals (against 12.5% in control) and to increase in the average duration of life of the animals that perished. 80-95% of mice survived the period of "intestinal deaths" (the 7th day after the irradiation) after combined prophylactic use of purasolone derivatives and cystamine before the irradiation of these animals in a dose of 1050 R. The radioprotective effect of pyrasolone derivatives given in therapeutic doses was less pronounced.     

Modifying properties of 2,5-diphenyloxazole during low-dose X-ray exposure of mice

The ability of 2,5-diphenyloxazole (DPO) to modify biological consequences of the X-rays irradiation of mice was studied with a dose of 16 cGy at the administration of the agent in a wide range of concentrations before or after irradiation was studied. It was shown that the administration of the agent in doses 9.9 x 10(-3)-9.8 mg/kg 35-60 min before irradiation causes a reliable decrease in the spleen mass within 1 month after the action; for the dose 1 mg/kg, it causes the tendency to decrease of the content of lipid peroxidation (LPO) products; the dose 9.8 mg/kg causes a decrease in the cell-free DNA amount in blood plasma of mice. The administration of DPO before irradiation causes changes in the scale and direction of the correlation between the DNA and LPO products contents in blood plasma of irradiated mice compared with the control. The administration of DPO 15-60 min after irradiation do not cause any reliable changes in the investigated parameters. The aviability of the study of the radioprotective properties of the DPO derivatives as agents with a nontraditional character of action is supposed.     

Radioprotective action of a combination of poly I-poly C and mexamine

In experiments on (CBA X C57Bl)F1 mice irradiated with doses of 8-12 Gy a study was made of the effect of a mixture of polyI-polyC (2.5 mg/kg, 2 days before irradiation) and mexamine (30 mg/kg, 5 min before irradiation) on the survival rate of animals and the times of their death. It was shown that polyI-polyC potentiates the protective effect of mexamine not increasing its toxicity. The protective agents used in a combination decrease the "intestinal" death of irradiated animals while used separately fail to produce this effect.     

Therapeutic effect of vegetable oils and ubiquinone-9 on radiation injuries

The comparison was made of the protective (the administration 3 h before irradiation with a dose of 7.3 Gy) and therapeutic (the administration immediately and later after exposure) effects of soya oil (150 mg/kg) and oil solution of ubiquinone-9 (100-200 mg/kg) on survival of exposed rats. It was shown that soya oil and ubiquinone-9 increased the survival rate of rats when administered before and, to a lesser extent, immediately after irradiation. Corn oil administered immediately after exposure increased the survival rate as well. DMF for the therapeutic effect of soya oil solution of ubiquinone-9 was 1.08.     

Modifications by BCG of the mortality of the irradiated mouse]

Freeze-dried Bacillus Calmette Guerin (B.C.G.) of Institut Pasteur was given by intravenous route to mice at 1,2 and 4 mg/kg before and after gamma irradiation of animals by 1 000 rad. B.C.G. 1 mg/kg injected the day or the day after irradiation has a protective effect (mortality reduced from 77% for controls to 58% and 50% for treated mice). B.C.G. given before irradiation in single or double doses increased mortality.     

Optimization of tumour radiotherapy: Part V--Radiosensitization by 2-deoxy-D-glucose and DNA ligand Hoechst-33342 in a murine tumour

Radiosensitizing effects of combination of a minor groove DNA ligand, Hoechst-33342, with the glucose analogue and inhibitor of glycolysis, 2-deoxy-D-glucose (2-DG) have been investigated in Ehrlich ascites tumour (EAT) bearing mice following focal irradiation of the tumour with 60Co gamma-rays. Treatment-induced tumour growth delay and tumour free animal survival were evaluated as parameters of radiation response. Focal irradiation of the tumour with a single fraction of 10 Gy induced a moderate delay in tumour growth but did not lead to complete regression in any of the tumours. Intravenous administration of H-342 1 hr before irradiation enhanced radiation-induced growth delay in a dose dependent manner. Complete regression of the tumour was observed only at a dose of 10 mg/kg body wt, leading to a cure (tumour free survival for more than 100 days) rate of 55%. Administration of 2-DG (2 g/kg body wt; i.v.), immediately before irradiation significantly enhanced radiation-induced growth delay and resulted in a cure rate of 45%. In combination with this dose of 2-DG (2 g/kg body wt), H-342 at a lower dose (5 mg/kg body wt) significantly enhanced the cure rate to 66%. H-342 or 2-DG given alone or in combination at the doses investigated here did not show any significant effects on the unirradiated tumour.     

Parameters of proliferative activity of hematopoietic cells in mice protected from irradiation by indralin in combination with Zn-metallothionein

One day after the irradiation (dose 6 Gy) of mice protected by the injection of Zn-metallothionein (Zn-MT) in doze 8.6 mg/kg, 10-20 min before irradiation, then alpha-adrenomimetic indraline (150 mg/kg) 5-10 min before irradiation the increase in nucleic cell number, [3H] thymidine incorporation, and antioxidant activity in bone marrow in comparison with the control and indraline per se was revealed. In mice protected according to the scheme: Zn-MT in the same doze, then indraline (100 mg/kg) one day after, and then in 5-10 min exposure to 6 Gy it was found more than 9 times increase of endogeneous CFC in spleen on 8th day while indraline per se raised CFC number only 4.8 times. It was found that Zn-MT reduce the indraline acute toxicity. The data on radioprotective activity of monomeric and polymeric Zn-MT forms are submitted.     

Selenium Pretreatment Enhances the Radioprotective Effect and Reduces the Lethal Toxicity of Wr-2721

Although WR-2721, S-2-(3-aminopropylamino)ethylphosphorothioic acid, is an effective radioprotector, its use is limited by its toxicity. Combining WR-2721 with other agents might decrease its toxicity and/or increase its effectiveness. The effect of selenium (Se) pretreatment on the acute toxicity and radioprotective effect of WR-2721 was studied in male CD2F1 mice. Injection of 1.6mg/kg Se 24 hr before WR-2721 (800-1200 mg/kg, IP) decreased the lethality of WR-2721 significantly. Lower doses of Se were also effective, but simultaneous administration was not effective. Se injection alone (1.6 mg/kg) 24 hr before cobalt-60 irradiation increased the survival (dose reduction factor, DRF = 1.1) significantly. A synergistic effect on post-irradiation survival was observed when Se was injected 24 hr before WR-2721 (200-600 mg/ kg IP before irradiation). For example, after exposure to 22 Gy (1 Gy/min), 30-day survival was 100% when mice were treated with both Se and 600mg/kg WR-2721, and was 13% with WR-2721 alone. The DRF after 400 mg/kg WR-2721 was 2.6 with Se compared to 2.2 without Se pretreatment. Alkaline phosphatase activity in bone marrow cells and serum was significantly depressed after treatment with 1.6 mg/kg Se, suggesting that a retardation of conversion of WR-2721 to its active free sulfhydryl form through the action of alkaline phosphatase might be partly responsible for the effects of Se. Other possible mechanisms related to the antioxidant properties of Se are under investigation.     

Selenium Pretreatment Enhances the Radioprotective Effect and Reduces the Lethal Toxicity of Wr-2721

Although WR-2721, S-2-(3-aminopropylamino)ethylphosphorothioic acid, is an effective radioprotector, its use is limited by its toxicity. Combining WR-2721 with other agents might decrease its toxicity and/or increase its effectiveness. The effect of selenium (Se) pretreatment on the acute toxicity and radioprotective effect of WR-2721 was studied in male CD2F1 mice. Injection of 1.6mg/kg Se 24 hr before WR-2721 (800-1200 mg/kg, IP) decreased the lethality of WR-2721 significantly. Lower doses of Se were also effective, but simultaneous administration was not effective. Se injection alone (1.6 mg/kg) 24 hr before cobalt-60 irradiation increased the survival (dose reduction factor, DRF = 1.1) significantly. A synergistic effect on post-irradiation survival was observed when Se was injected 24 hr before WR-2721 (200-600 mg/ kg IP before irradiation). For example, after exposure to 22 Gy (1 Gy/min), 30-day survival was 100% when mice were treated with both Se and 600mg/kg WR-2721, and was 13% with WR-2721 alone. The DRF after 400 mg/kg WR-2721 was 2.6 with Se compared to 2.2 without Se pretreatment. Alkaline phosphatase activity in bone marrow cells and serum was significantly depressed after treatment with 1.6 mg/kg Se, suggesting that a retardation of conversion of WR-2721 to its active free sulfhydryl form through the action of alkaline phosphatase might be partly responsible for the effects of Se. Other possible mechanisms related to the antioxidant properties of Se are under investigation.     

Radiomodifying properties of the synthetic analog of prostaglandin F2 alpha-estrofan

Estrofan (0.1 to 5 mg/kg) administered to rats and mice 5 min prior to gamma irradiation with doses of 8.5 to 9.5 Gy (LD90/30) increases the survival rate up to 30-40 per cent. The drug is ineffective when administered 30 and 60 min before irradiation.     

Protection by interleukin 1 against lung toxicity caused by cyclophosphamide and irradiation

Interleukin 1 has been shown to provide protection against the toxic effects of cyclophosphamide given in combination with localized irradiation of the lung. A single dose of 15 micrograms/kg interleukin 1 was given 24 h before cyclophosphamide (25-125 mg/kg) which was followed 1 day later by five daily exposures of 4.5 or 5.0 Gy, localized to the lung. Interleukin 1 significantly reduced early measurements of breathing rate for mice treated with high cyclophosphamide doses and irradiation, and at cyclophosphamide doses above 50 mg/kg, there was a significant reduction in the lethality from the combined treatment. At lower levels of cyclophosphamide, however, there seemed to be no effect.     

Hematopoietic Recovery and Amelioration of Radiation-Induced Lethality by the Vitamin E Isoform δ-Tocotrienol

δ-Tocotrienol (DT3), a vitamin E isoform, is associated with strong antioxidant and immunomodulatory properties. We confirmed the potent antioxidant activity in membrane systems and showed that DT3 is an effective radiation protector and mitigator. DT3 (4 μM, P < 0.001) inhibited lipid peroxidation in mouse liver microsomes and nitric oxide (NO) formation (20 μM DT3, P < 0.01) in RAW264.7 cells, a murine alveolar macrophage line. In CD2F1 mice exposed to lethal total-body radiation from a (60)Co γ-radiation source, a single subcutaneous (s.c.) injection of DT3 before or after irradiation produced a significant increase in 30-day survival. DT3 was effective from 18.75 to 300 mg/kg (--24 h, P < 0.001). A single dose of 150 or 300 mg/kg DT3 given 24 h before irradiation (radioprotection) resulted in dose reduction factors (DRFs) of 1.19 and 1.27, respectively (P < 0.001). Further, DT3 reduced radiation lethality when administered 2, 6 or 12 h after irradiation, and 150 mg/kg DT3 administered 2 h after exposure conferred a DRF of 1.1 (mitigation). The optimum schedule of 300 mg/kg DT3 24 h prior to 7 Gy significantly reduced pancytopenia compared to irradiated controls (P < 0.05). The large therapeutic potential of and multi-lineage hematopoietic recovery for DT3 warrants further studies.     

The radiation modifying properties of carnosine

The influence of carnosine (beta-alanyl-l-histidine) on the survival rate of albino mice subjected to whole-body X-irradiation has been investigated. Carnosine (50-200 mg/kg/day) administered per os during a period of 20 days before irradiation (5.0 Gy) increased the survival rate by 45-65%, whereas the administration of carnosine within 30 days after irradiation (5.5 Gy) produced an insignificant protective effect and caused inhibition of the postirradiation histamine accumulation in the spleen.     

Histomorphological changes in murine fibrosarcoma after hypericin-based photodynamic therapy

Histomorphological changes in murine fibrosarcoma after photodynamic therapy (PDT) based on the natural photosensitizer hypericin were evaluated. C3H/DiSn mice were inoculated with fibrosarcoma G5:1:13 cells. When the tumour reached a volume of 40-80 mm(3) the mice were intraperitoneally injected with hypericin, either in a single dose (5 mg/kg; 1 or 6 h before laser irradiation) or two fractionated doses (2.5 mg/kg; 6 and 1 h before irradiation with laser light; 532 nm, 70 mW/cm(2), 168 J/cm(2)). All groups of PDT-treated animals with single and fractionated hypericin dosing presented primary vascular reactions including vascular dilatation, congestion, thrombosis and oedema. Two hours after PDT there were necrotic changes with small, rather focal appearance. One day after therapy the necrotic areas were enhanced, often affecting a complete superficial layer of tumour tissue. Necrotic areas were accompanied with inflammation and haemorrhages.     

Bone marrow toxicity of total-body irradiation combined with radiosensitizers

The effect of the addition of radiosensitizers to low-dose total-body irradiation was studied. SR2508 (1 g/kg) or misonidazole (0.35 g/kg) was given 30 min prior to single-dose total-body irradiation, delivered at 0.1 Gy/min. Six dogs received either SR2508 or misonidazole and 2 Gy irradiation, and 14 dogs served as controls, receiving no drug and either 2 or 3 Gy of total-body irradiation. All dogs had a decline in their white blood cell and platelet counts and were supported with prophylactic antibiotics and platelet transfusions. High plasma levels of both radiosensitizers were achieved. The degree of cytopenia with 2 Gy total-body irradiation when combined with either radiosensitizer was not significantly greater than that seen with 2 Gy alone, and the neutropenia was significantly less than that seen with 3 Gy alone. The only observed toxicity of the drugs was vomiting, which started shortly after the infusion of SR2508 and before the radiation treatment. A single high-dose infusion of a radiosensitizer combined with total-body irradiation appears to cause a mild increase in bone marrow toxicity but is otherwise well tolerated.     

Effect of subtherapeutic doses of docetaxel (taxotere) on the efficacy of radiotherapy and pro-oxidant-antioxidant balance in rats with Guerin's carcinoma

In the experiments at Wistar male rats the effect of subtherapeutic doses of docetaxel (5 and 10 mg/kg) on the radiotherapy efficacy (20 Gy of single-dose X-rays) namely growth rate of Guerin's tumor and prooxidant-antioxidant balance in liver and blood of animals bearing tumors was investigated. It has been demonstrated that docetaxel at dose 5 mg/kg given 18 hours before irradiation resulted in significant tumor growth delay (2.3-2.7-fold) in comparison with group of rats that received only irradiation. After application of higher dose of docetaxel there was no statistically significant change of tumor size along the whole experiment (14 and 21 days after tumor implantation). Content of lipid peroxidation products was revealed to be considerably increased after chemotherapy and concurrent irradiation when docetaxel was used in a dose of 10 mg/kg. At the same time glutatione peroxidase activity and antioxidative activity of blood plasma were reduced. In the rat liver chemoradiotherapy led to decrease of glutathion peroxidase and glutathione-S-transferase activity to greater degree at docetaxel dose of 10 mg/kg. The obtained results allow to conclude that higher dose of docetaxel and concurrent irradiation resulted in the most effective Guerin's carcinoma growth delay and considerable deviation of antioxidant-prooxidant balance of tissues in the direction of the last.     

Effect of choline on the DNA supramolecular complex in rats and their survival following gamma irradiation

The injection of choline-chloride (200 mg/kg) to rats 15 min before 6 Gy irradiation was shown to increase their survival rate over a period of 30 days, to prolong their average life, and to promote the complete restoration of elastoviscosity of DNA supramolecular complexes in thymus, spleen, liver and brain. When administered immediately after irradiation the drug increased the survival rate of rats.     

In vivo radiosensitization by diethyldithiocarbamate

Diethyldithiocarbamate (DDC) has been suggested to have both radiosensitizing (due to superoxide dismutase (SOD) inhibition) and radioprotective properties. We have studied the activity of SOD up to 24 h after intratumoral administration of 50, 100, 150, and 300 mg/kg DDC in 3-methylcholanthrene-induced tumors in BALB/c mice. Maximal inhibition of SOD (8% of control) was obtained 1 h after administration of 100 mg/kg DDC. Tumor response to DDC and X irradiation was assessed using a tumor growth-delay assay, after 11 Gy 100-kVp X rays given up to 24 h after DDC administration. Radiation-induced tumor growth delay (7.11 +/- 1.76 days) was enhanced only when tumors were irradiated 2-4 h after 50 mg/kg DDC. When higher doses of DDC were used, tumor cure was noted when DDC was injected 1-6 h before irradiation. We suggest our findings are consistent with radiosensitization being due to SOD inhibition, but that if insufficient time is allowed between DDC injection and irradiation, the sensitization is masked by a radioprotective effect. We believe that further investigations as to the therapeutic potential of DDC in human patients with cancer are warranted.     

The response of murine stem spermatogonia to radiation combined with 3-aminobenzamide

The influence of 3-aminobenzamide (3-AB) on the radiation response of the stem spermatogonia of the CBA mouse has been investigated. Doses of 3-AB from 66 to 450 mg/kg, administered 1 h before irradiation, significantly enhanced stem-cell killing. Enhancement was observed when 3-AB (450 mg/kg) was given up to 5 h before, but not if administered after, irradiation. When radiation was delivered at a lower dose rate (5 cGy/min compared to 180 cGy/min) significant dose sparing was achieved for radiation alone. Pretreatment with 3-AB resulted in slightly less enhancement at the low dose rate than at the high. Split-dose studies (9 Gy total dose) with radiation alone resulted in a recovery ratio of 1.4-1.5. Administration of 3-AB before the first dose resulted in a similar recovery ratio, but if given immediately after the first dose the ratio was smaller. Pretreatment of mice with the radiosensitizer RSU-1069 indicated that at least some of the stem cells were radiobiologically hypoxic. We suggest therefore that the enhancement of spermatogonial stem-cell killing by 3-AB is not entirely due to inhibition of repair processes but may also involve modification of the oxygen status of the testis.