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.     

The antiradiation properties of the ecdysteroid-containing compounds

The antiradiation properties of the ecdysteroid-containing preparations ("serpisten" and inokosterone) are studied under their application before or after the 22.6 cGy chronic low intensity gamma-irradiation of mice. It is shown that the antiradiation of these compounds depend on the dose of preparations and time of the application before or after irradiation of mice. "Serpisten" prevented the decrease of the growth of the body mass of irradiated mice. The normalization of the phospholipid composition of the mice liver and blood erythrocytes for the most investigated parameters revealed under the application of this compound at the dose of 50 mg/kg after the irradiation of animals. The capacity of "serpisten" to decompose of peroxides is shown in vitro. Inokosterone had the certain anabolic properties, caused the normalization of the total peroxidase activity of blood and intensity of the lipid peroxidation (LPO) in brain and in liver, and also the repair of the interrelation between the LPO intensity and catalase activity in the irradiated mice liver. The obtained results allow to conclude that the antiradiation properties of the ecdysteroid-containing preparations under the chronic low intensity irradiation of animals at the low dose due to their capacity to depend on the LPO regulatory system parameters.     

Oral oxymetholone reduces mortality induced by gamma irradiation in mice through stimulation of hematopoietic cells

Oxymetholone is a 17α -alkylated anabolic-androgenic steroid. This drug can stimulate bone marrow cells and increase the blood cells in the peripheral blood vessels. It has been used for the treatment of anemia caused by low red cell production. Since oxymetholone has hematopoietic effect, we studied radioprotective effects of this drug in mice. In this study, we determined percentage of survival, dose-reduction factor (DRF) and hematological parameters in irradiated mice which treated with or without oxymetholone. Oxymetholone administrated at different doses 80, 160, 320, 640 mg/kg by gavages at 24 h before 8 Gy gamma irradiation. At 30 days after treatment, the following percentage of animals survival in each group was as: 80 mg/kg, 50%; 160 mg/kg, 50%; 320 mg/kg, 55%; 640 mg/kg, 75% and vehicle, 15%. Percentage of survival increased in all of treated groups statistically compared with irradiated-vehicle group. In the groups treated by oxymetholone, maximum protection was realized at 640 mg/kg. In order to calculate the DRF for oxymetholone, mice were exposed to whole-body gamma irradiation with dose ranges between 5.83 and 11.23 Gy. The probit line for oxymetholone-treated mice was shifted to the right with a DRF of 1.14. In mice exposed to whole-body gamma-irradiation (4 Gy), an oral administration of 640 mg/kg oxymetholone ameliorated radiation-induced decreases in circulating platelets and erythrocytes, but had a less effect on total number of WBC. These results demonstrate that oxymetholone stimulates myelopoiesis and thrombocytopenia and enhances survival in mice after ionizing radiation.     

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.     

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.     

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.     

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.     

Changes in the sensitivity of mice to the action of gamma irradiation by Viscum album L. polysaccharides]

The influence of water-soluble polysaccharides of Viscum album L. on the survival of mice subjected to whole-body gamma-irradiation has been investigated. Polysaccharides were shown to exert a radioprotective effect which was a function of both the radiation dose and the drug dose and time of its injection. The maximum radioprotective efficacy of polysaccharides was observed after their injection 15 min before irradiation. A single intraperitoneal administration of polysaccharides (25 mg/kg) before irradiation with LD50/30 and LD100/10-12 increased the 60-day survival rate up to 95% and 27% respectively. The postirradiation injection of polysaccharides prevented death of 80% of mice given LD50 and increased the average life expectancy of animals irradiated with absolutely lethal doses.     

Melatonin and protection from whole-body irradiation: survival studies in mice

The radioprotective ability of melatonin was investigated in mice exposed to an acute whole-body gamma radiation dose of 815 cGy (estimated LD50/30 dose). The animals were observed for mortality over a period of 30 days following irradiation. The results indicated 100% survival for unirradiated and untreated control mice, and for mice treated with melatonin or solvent alone. Forty-five percent of mice exposed to 815 cGy radiation alone, and 50% of mice pretreated with solvent and irradiated with 815 cGy were alive at the end of 30 days. Irradiated mice which were pretreated with 125 mg/kg melatonin exhibited a slight increase in their survival (60%) (p=0.3421). In contrast, 85% of irradiated mice which were pretreated with 250 mg/kg melatonin were alive at the end of 30 days (p=0.0080). These results indicate that melatonin (at a dose as high as 250 mg/kg) is non-toxic, and that high doses of melatonin are effective in protecting mice from lethal effects of acute whole-body irradiation.     

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.     

Suppression of delayed-type hypersensitivity to oxazolone in whole-body-irradiated mice and protection by WR-2721

The effect of whole-body irradiation on cellular immunity, as measured in vivo by delayed-type hypersensitivity (DTH) to oxazolone (4- ethoxymethylene -2-phenyl- oxazol -5-one), was determined in CD2F1 mice. DTH, determined by changes in ear swelling after challenge with oxazolone, was significantly depressed in irradiated mice (500-900 rad of 60Co) in a dose-dependent fashion when animals were irradiated after sensitization and before challenge with oxazolone. Administration of WR-2721 [S-2-(3-aminopropylamino)ethylphosphorothioic acid] 30 min before irradiation (2 days after sensitization) resulted in protection against suppression of DTH, which was dependent on drug and radiation dose. An effective dose of WR-2721 (200 mg/kg body wt) provided an approximate dose-modifying factor of 1.3. The data suggest that WR-2721 interacts with cells involved in that DTH response (lymphocytes and/or macrophages) and that WR-2721 may be useful in protecting against radiation-induced decrements in cell-mediated immunity.     

Radioprotection by mangiferin in DBAxC57BL mice: a preliminary study

The radioprotective effects of various concentrations (0, 0.25, 0.5, 1, 2, 5, 10, 17.5, 25, 50, 75 and 100 mg/kg b.wt.) of mangiferin (MGN) was studied in the DBAxC57BL mice whole body exposed to 10 Gy of gamma-irradiation. Treatment of mice with different doses of MGN, one hour before irradiation reduced the symptoms of radiation sickness and delayed the onset of mortality when compared with the non-drug treated irradiated controls. The radioprotective action of MGN increased in a dose dependent manner up to 2mg/kg and declined thereafter. The highest radioprotective effect was observed at 2mg/kg MGN, where greatest number of animals survived against the radiation-induced mortality. The administration of 0.5, 1, 2, 5, 10 and 17.5 mg/kg MGN reduced the radiation-induced gastrointestinal death as evident by a greater number of survivors up to 10 days in this group when compared with the DDW + 10 Gy irradiation group. A similar effect of MGN was observed for the radiation-induced bone marrow deaths also. Our study demonstrates that mangiferin, a gluosylxanthone, present in the Mangifera indica protected mice against the radiation-induced sickness and mortality and the optimum protective dose of 2mg/kg was 1/200 of LD50 dose (400 mg/kg) of MGN. The administration of 400 mg/kg MGN induced 50% mortality, therefore LD50 of the drug was considered to be 400 mg/kg.     

Multi-endpoint biological monitoring of phosphine workers

5-Aminosalicylic acid (5ASA), a prescribed drug for ulcerative colitis, is a potent scavenger of oxygen-derived free radicals. The present study was undertaken to ascertain its ability to protect against radiation-induced damage. The drug dose-dependent effect, optimum time of drug administration and radiation dose-dependent effect (0-4 Gy) on in vivo radiation protection against micronuclei induction in polychromatic erythrocytes (PCE) and normochromatic erythrocytes (NCE) were studied in the bone marrow of mice. Intraperitoneal injection of 10-125 mg/kg of the drug 30 min before whole body irradiation with 3 Gy produced a significant reduction in the frequency of micronucleated erythrocytes at 24 h after exposure. The optimum dose for protection without drug toxicity was 25 mg/kg body weight. Injection of 25 mg/kg of the drug 60 or 30 min before or within 15 min after 3 Gy whole body gamma-irradiation resulted in a significant decrease in the radiation-induced PCE and NCE with micronuclei (MPCE and MNCE) and an increase in the ratio of PCE to NCE (P/N), at 24 h post-irradiation. Maximum effect was seen when the drug was administered 30 min before irradiation. Therefore, to study the radiation dose-response, mice were pre-treated with 25 mg/kg of 5ASA 30 min before 1-4 Gy of gamma-irradiation. Radiation increased the MN frequency linearly (r(2)=0.99) with dose. Pre-treatment with 5ASA significantly reduced the MN counts to 40-50% of the radiation (RT) alone values, giving a dose modification factor (DMF) of 2.02 (MPCE) and 2.53 (MNCE). Irradiation resulted in a dose-dependent decline in the P/N ratio at all the doses of radiation studied. 5ASA produced a significant increase in the P/N ratio from that of irradiated controls, at all doses of radiations tested. These results show that 5ASA protect mice against radiation-induced MN formation and mitotic arrest.     

Aromatase inhibition by R 83 842, the dextro isomer of R 76 713, in JEG-3 choriocarcinoma grown in ovariectomized nude mice

The effects of repeated (5 days) dosing with the non-steroidal aromatase inhibitor R 83 842 (the dextro isomer of R 76 713) on tumor aromatase and uterus weight in ovariectomized nude mice bearing JEG-3 tumors were examined. In animals bearing an androstenedione implant the presence of a JEG-3 tumor significantly increased uterus weight, proving that tumor aromatase indeed converted androgens to estrogens. Oral administration of R 76 713 (10 mg/kg) for 5 days reduced the increase in uterus weight by 84% in tumor bearing mice revealing true in vivo aromatase inhibition by R 76 713.

Experiments performed in the absence of exogenously added androgens gave similar results. Uterus weights in tumor bearing mice were significantly higher than in control mice. Oral administration of R 83 842 (5 mg/kg) for 5 days reduced uterus weight in the tumor bearing animals. Ex vivo aromatase measurements performed in JEG-3 tumors from these animals showed an aromatase inhibition of 93.9% in treated mice as compared to untreated mice. Five days oral treatment with R 83 842 dose-dependently lowered both aromatase activity and uterus weight. Doses of 5 and 0.5 mg/kg inhibited tumor aromatase by 94.1 and 74.7%, respectively, and reduced uterus weight. After a dose of 0.05 mg/kg aromatase activity and uterus weight were similar to those in the control group.     

Radioprotective effect of melatonin assessed by measuring chromosomal damage in mitotic and meiotic cells.

This study was taken to evaluate the radioprotective effects of melatonin. Male adult albino mice were treated (intraperitoneal, i.p.) with 10 mg/kg melatonin either 1 h before or 1/2 h after exposure to 1.5 Gy of gamma-irradiation. Control, melatonin, irradiated and melatonin plus irradiation groups were sacrificed 24 h following treatment. The incidence of micronuclei (MN) in bone marrow cells was determined in all groups. The results show that melatonin caused a significant reduction in micronuclei polychromatic erythrocytes (MNPCE) when animals were treated with melatonin before and not after exposure to radiation. Mitotic and meiotic metaphases were prepared from spermatogonial and primary spermatocytes, respectively. Examination and analysis of metaphases showed no mutagenic effect of melatonin on chromosomal aberration (CA) frequency in spermatogonial chromosomes. Administration of one single dose of melatonin to animals before irradiation lowered total CA from 46 to 32%. However, no significant effect was observed when melatonin was given after irradiation. Similarly, the frequency of CA in meiotic metaphases decreased from 43.5% in the irradiated group to 31.5% in the irradiated group treated with melatonin 1 h before irradiation, but no change was observed when melatonin was administered after irradiation. The data obtained in this study suggest that melatonin administration confers protection against damage inflicted by radiation when given prior to exposure to irradiation and not after, and support the contention that melatonin radioprotection is achieved by its ability as a scavenger for free radicals generated by ionizing radiation.     

Photoinduced antitumour effect of hypericin can be enhanced by fractionated dosing

The in vivo antitumour activity of the natural photosensitizer hypericin was evaluated. C3H/DiSn mice were inoculated with fibrosarcoma G5:1:13 cells. When the tumour reached a volume of 40-80mm3 the mice were intraperitoneally injected with hypericin, either in a single dose (5mg/kg; 1 or 6h before laser irradiation) or two fractionated doses (2.5 mg/kg; 6 and 1 h before irradiation with laser light; 532 nm, 70mW/cm2, 168 J/cm2). All tumours in control groups treated with hypericin alone as well as those irradiated with laser light alone had similar growth rates and none of these tumours regressed spontaneously. Complete remission of tumour in photodynamic therapy (PDT)-treated groups was similar (14-17% single dose vs. 33% fractionated dose), but the fractionated schedule of hypericin dosing was found to be more efficient than the single dose, measured by survival assay (p < 0.05). Our experimental model showed that fractionated administration of hypericin can produce a better therapeutic response than single administration.     

Protective effect of corticosteroids on radiation pneumonitis in mice

We explored the protective effect of corticosteroids on the mortality of mice that received thoracic irradiation. Methylprednisolone, 100 mg/kg/week, given from 11 weeks after gamma irradiation of the thorax resulted in an increase in the LD50 (11-26 weeks) from 14.3 +/- 0.3 (mean +/- SE) Gy to 17.6 +/- 0.4 Gy, P less than 0.001, a protection factor of 1.2. Withdrawal of steroids at various times during the period of radiation pneumonitis resulted in accelerated mortality in the next 2-4 weeks, so that the cumulative mortality "caught up" with that of control animals by 4 weeks after steroid withdrawal. However, after the end of the usual period of pneumonitis withdrawal of steroids did not result in accelerated mortality, suggesting that the time when steroids are protective corresponds to the duration of pneumonitis. A smaller dose of steroids, 25 mg/kg/week, was found to be as protective as the larger dose used in the above experiments. The possibility that corticosteroids reduce mortality, even when given many weeks after radiation, may have important practical and theoretical implications.     

Anti-inflammatory activity of hydroxydihydrocarvone

Hydroxydihydrocarvone (HC) is a synthetic intermediate obtained by hydration of the natural compound (R)-(-)-carvone. The aim of the present study was to investigate the possible anti-inflammatory activity of orally administered HC. Toxicity, motor coordination, tail immersion test, as well as carrageenan-induced paw edema and myeloperoxidase (MPO) activity or peritonitis were all evaluated in rodents. HC was force-fed to the animals 1 h before the stimulus. The lethal dose 50% (LD50) of orally administered HC was 1259 mg/kg. No changes in motor coordination were recorded in HC-treated mice in the rotarod test. The time of response to the thermoceptive stimulus in the tail immersion test was longer in HC-treated animals (50, 100, and 200 mg/kg) than in the vehicle-treated group. HC also significantly decreased the area under curve of carrageenan-induced rat paw edema at 100 and 200 mg/kg and MPO activity at 200 mg/kg. Carrageenan-induced neutrophil recruitment to the peritoneal cavity was significantly reduced by HC at doses of 100 or 200 mg/kg, but not 50 mg/kg. These findings demonstrate that orally administered HC exerts antinociceptive and anti-inflammatory activities in rats and mice.     

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.