The effect of gas hypoxia (10% O2) and dextran sulfate on the radiosensitivity of the stem cells of the intestinal epithelium in mice]

Injection of dextran sulphate before irradiation was shown to protect jejunal epithelium stem cells (D0 increased from 1.13 to 1.82 Gy). The protective effect of a combination of dextran sulphate and gas hypoxic mixture (10% O2) did not exceed that of the administration of the gas hypoxic mixture (10% O2) alone.     

Effect of intermittent normobaric hypoxic activity on the development of acute radiation disease]

The experiments on 260 male mice of colony SHK, 352 mongrel rats and 20 Wistar rats were carried out to study the ability of using the normobaric hypoxic stimulation method for acute radiation sickness. Hypoxic stimulation using gas mixture with 10% of oxygen and 90% of nitrogen was conducted for two weeks after irradiation for 30 min. every day. It is shown that under influence of ionizing radiation (7 and 5.5 Gy) the postradiation hypoxic action increased the 30-day survival rate of mice, reduced disturbances of the qualitative composition of leukocytes in peripheric blood, promoted more rapid restoration of thromboelastography indices and caused no reliable changes in the postradial content of albumin and creatinine in blood.     

Manifestation of oxygen effect during normobaric hypoxic hypoxia in the intrauterine and postnatal developmental periods]

The experiments on rats have shown that hypoxic gas mixture containing 10% of oxygen and 90% of nitrogen (HGM-10) under normobaric conditions exerts a highly reliable radioprotective effect on progeny when 11-day pregnant animals are exposed to total irradiation (60Co, 20 Gy). As distinct from the known radioprotector, mexamine, (5-methoxytryptamine), HGM-10 has a pronounced radioprotective effect during the first days (1-5) after birth. Radioresistance of new-born rats correlates with the level of pO2 in the tissues which progressively decreases with respiration of HGM-10 and remains unchanged after mexamine (10 mg/kg) introduction.     

Radiomodifying effect of acute hypoxia in neutron-irradiated dogs

A pronounced protective effect of acute hypoxia was demonstrated on dogs exposed to fast neutrons (4.0 Gy). Breathing of 10% gas hypoxic mixture protected more than half of the exposed animals from death and provided the development of a light form of radiation sickness instead of a serious one. Possible mechanism of the effect observed are discussed.     

Modification of the radiation injury of hematopoiesis in rats using the gaseous hypoxic mixture GHM-10

In experiments on Wistar rats it was shown that gas hypoxic mixture containing O2 (10%) and N2 (90%) had a radioprotective action with regard to the survival rate for 30 days and to the haemopoietic system status. The application of gas hypoxic mixture reduced the postirradiation cytopenia in the blood and lowered the degree of the bone marrow depletion by the 3d day following irradiation; DMF was 1.25 as determined by total bone marrow cellularity.     

The effect of x-ray radiation and hypoxia on the proteolytic activity of the normal rat spleen and during tumor growth

The influence of X-radiation on activity of lysosomal enzymes (D, L, H cathepsins) in rat spleen tissue and in inoculated rat sarcoma 45 has been investigated. Intact rats and rats with tumors were subjected to whole-body and sarcoma 45 to local irradiation with doses of 0.155 C/kg and 0.31 C/kg in conditions of breathing gas hypoxic mixture containing 90% of nitrogen and 10% of oxygen (GHM-10). The combined exposure to radiation and GHM-10 was shown to produce a certain protective action (e.g. normalized cathepsin activity) in the spleen. In the tumor tissue the protective effect of GHM-10 was absent.     

Radiosensitization of murine tumors by Fluosol-DA 20%

The effect of perfluorochemicals in combination with carbogen breathing on the response of SCK tumors of mice to fractionated irradiation was investigated. The SCK tumors of A/J mice were irradiated twice a day at 3 Gy per fraction (6 Gy per day), with a total dose of 18 Gy over 3 days. When the host animals were treated with an intravenous (iv) injection of 12 ml/kg of Fluosol-DA 20% before the first daily tumor irradiation and carbogen breathing during every X irradiation with Fluosol-DA 20% injection without carbogen breathing. The hypoxic cell fraction, as determined by an in vivo-in vitro cloning assay, decreased significantly, and the intratumor pO2, as determined with microelectrodes, was markedly increased by Fluosol-DA 20% injection and carbogen breathing. It was concluded that oxygenation of hypoxic cells in SCK tumors during the course of fractionated irradiation was improved by the iv injection of Fluosol-DA 20% and carbogen breathing.     

Dominant lethal effect of 60Co gamma radiation in Biomphalaria glabrata (SAY, 1818)

The dominant lethal effects of gamma radiation of 60Co in the snail Biomphalaria glabrata were studied. Three groups of 13 wild-type snails were irradiated with single doses of 2.5; 10 and 20 Gy. Crossings were carried out at intervals of 7, 17, 23, 30 and 36 days after irradiation. The dominant lethal effect was observed only at the first crossing occurring 7 days after irradiation with 2.5 Gy. With 10 and 20 Gy, the induction of lethal mutations was detected at 7, 17 and 23 days after irradiation; a dose-response effect was observed. The effect was stronger 7 days after irradiation, decreasing in the succeeding crossings up to 30 days. Cell-killing effects on germ cells were detected in the crossings at 23 days and 30 days after irradiation with 20 Gy. After 36 days, frequencies of malformations resumed background levels; crossing rates partially recovered. These results show that gamma radiation affected all the stages of spermatogenesis. Germ cells at later phases were more sensitive to the mutagenic effect of radiation and the cell killing effects were observed on the youngest cells. This response was similar to the highly homogeneous pattern observed in widely different species and allowed us to estimate some parameters of spermatogenesis in B. glabrata.     

Effect of the gaseous hypoxic mixture GHM-10 on the radiosensitivity of the fetus and the development of offspring

A gas hypoxic mixture containing 10 percent of O2 and 90 percent of N2 was shown to exert a radioprotective action on pregnant rats and young rats of the first generation if animals were exposed to ionizing radiation during the periods of preimplantation, organogenesis and fetus development. The effect depended on the radiation dose and the period of the intrauterine development of fetus.     

Reduced oxygen enhancement ratio at low doses of ionizing radiation

A decreased oxygen enhancement ratio (OER) at lower radiation doses has been previously reported (B. Palcic, J. W. Brosing, and L. D. Skarsgard, Br. J. Cancer 46, 980-984 (1984]. The question remained whether or not this effect is due to a possible oxygen contamination at low doses, which was not the case at high doses. To ensure a sufficient degree of hypoxia prior to the start of irradiation, Chinese hamster cells (CHO) were made hypoxic by gas exchange combined with metabolic consumption of oxygen at 37 degrees C. At the same time oxygen levels in cell suspension were measured using a Clark electrode. It was found that under experimental conditions used in this laboratory for hypoxic irradiations, the oxygen levels before the start of irradiation are always below the levels which could give any significant enhancement to radiation inactivation by X rays. Full survival curves were determined in the dose range 0-30 Gy using the conventional survival assay and in the dose range 0-3 Gy using the low dose survival assay. The results confirmed the earlier finding that the OER decreases at low doses. It is therefore believed that the dose-dependent OER is a true radiobiological phenomenon and not an artifact of the experimental method used in the low dose survival assay.     

Effect of gaseous hypoxic mixture GHM-10 on the intestinal death of Wistar rats and Na+,K+-ATPase activity of the plasma membrane of the small intestine mucosa after irradiation

It was shown that gas hypoxic mixture containing O2 (10%) and N2 (90%) significantly decreases "intestinal" death of Wistar rats on the 5th day following irradiation and normalizes Na+,K+-ATPase activity of the small intestine mucosa plasma membranes.     

Use of respiratory mixture containing 8.0-8.5% of oxygen in hypoxic radiotherapy of cervical neoplasms]

Combined radiotherapy of patients with cervical carcinoma of stages IIb and IIIb was conducted. Hypoxia (8.0-8.5% of O2 in the respiratory mixture) was used in microfractionated (2 Gy) irradiation of metastatic spreading zones. When irradiating under conditions of hypoxia, the number of fractions was brought up to 28 as compared to 20 in control. Despite a 40%-increase of the dose, seriousness of radiation reactions and remote injuries remained at the same level. It is found that patients endure well the respiratory mixture for 6 min. necessary for irradiation.     

A comparison of the radiation response of the epidermis in two strains of pig

The response of the epidermis was compared in two strains of pig, the English Large White and the G?ttinger Miniature, after irradiation with 90Sr beta rays. The effects of two types of anesthesia were also tested in pigs of each strain, a volatile gas mixture of approximately 70% oxygen, approximately 30% nitrous oxide, and 2% halothane, and an intravenously administered narcotic azaperon/etimodat with the animals breathing air. Strain- and anesthetic-related changes were compared on the basis of dose-effect curves for the incidence of moist desquamation from which ED50 values (+/- SE) were determined, i.e., the dose required to produce this effect in 50% of the fields irradiated. For English Large White pigs anesthetized with the volatile gas mixture, an ED50 of 27.32 +/- 0.52 Gy was obtained for moist desquamation. Irradiation with the azaperon/etomidat anesthesia in this strain of pig produced a significantly higher ED50 of 33.36 +/- 0.76 Gy (P less than 0.001). This appeared to be related to the fact that the animals were breathing air, i.e., a lower oxygen concentration (approximately 21%), at the time of irradiation. For the G?ttinger Miniature pig the ED50 values for moist desquamation were 38.93 +/- 3.12 Gy and 43.36 +/- 1.34 Gy while using the gaseous anesthetic mixture and the azaperon/etomidat anesthesia with the animals breathing air, respectively. These ED50 values are 10-11 Gy higher than those obtained for the English Large White pig under identical conditions of anesthesia, which resulted in a strain difference ratio of approximately 1.35. Radiation under the volatile gas mixture anesthesia resulted in a uniform irradiation response over the skin of the flank in both strains of pig. Radiation under azaperon/etomidat anesthesia resulted in a nonuniform skin response over the flank. The ED50 for moist desquamation was significantly higher in dorsal sites on the flank compared with the ventral area of English Large White pigs; a similar trend was seen in G?ttinger Miniature pigs. This difference in the radiosensitivity over the flank skin while the animals are under azaperon/etomidat anesthesia at the time of irradiation was associated with the animals breathing air and is in agreement with findings published previously for animals under halothane anesthesia and breathing air.     

In vitro and in vivo expression of endothelial von Willebrand factor and leukocyte accumulation after fractionated irradiation

Previous investigations have demonstrated an increased release of von Willebrand factor (VWF; also known as vWF) in endothelial cells after high single-dose irradiation in vitro. We have also found increased levels of Vwf protein in mouse glomeruli after a high single dose of renal irradiation in vivo. In addition, increased numbers of leukocytes were observed in the renal cortex after irradiation in vivo. The aim of the present study was to investigate and quantify these biological processes after clinically relevant fractionated irradiation and to relate them to changes in renal function. A significantly greater increase in release of VWF was observed in cultured human umbilical vein endothelial cells (HUVECs) after fractionated irradiation (20 x 1.0 Gy) than after a single dose of 20 Gy (147% compared to 115% of control, respectively, P < 0.0005). In contrast with the in vitro observations, glomerular Vwf staining was lower after fractionated irradiation in vivo (20 x 2.0 Gy or 10 x 1.6 Gy +/- re-irradiation) than after a single dose of 16 Gy. The number of leukocytes accumulating in the renal cortex was also lower after fractionated in vivo irradiation than after a single radiation dose. The onset of these events preceded renal functional and histopathological changes by approximately 10 weeks. These data indicate that radiation-induced changes in endothelial VWF expression after in vivo irradiation may be distinct from the in vitro observations. Increased VWF expression may reflect pivotal processes in the pathogenesis of late radiation nephropathy and provide a clue to appropriate timing of pharmacological intervention.     

Radioprotective action of GHM-10 when administered with dextran sulfate and heparin

A single administration of dextransulfate (40 mg/kg, 1-3 days before irradiation), or a double injection of heparin (250 units/kg, 24 hr and 15 min before irradiation) potentiated a weak radioprotective effect of gas hypoxic mixture (GHM-10) on animals exposed to absolutely lethal doses.     

Chemical radiosensitization by misonidazole: production and repair of DNA single-strand breaks in Yoshida ascites tumor cells.

Formation of strand-breaks in DNA and its repair in Yoshida ascites tumor cells exposed to gamma radiation (100-400 Gy) in presence and absence of misonidazole (10 mM) were studied. The methodology involved pre-labelling of cellular DNA by 3H-thymidine during cell proliferation in rats, irradiation of cells in vitro and analysing sedimentation profile of DNA by ultracentrifugation in alkaline sucrose density gradients. Irradiation under euoxic conditions resulted in formation of about 1.5 times greater number of strand breaks as compared to those formed during irradiation under hypoxic conditions. Misonidazole (10 mM) by its presence along with the cells during irradiation under hypoxic conditions caused a 3-fold increase in the number of single strand breaks, but under euoxic conditions of irradiation the presence of misonidazole did not enhance the strand break formation. Incubation of cells irradiated in absence of misonidazole for 1 hr in tissue culture medium at 37 degrees C resulted in repair of substantial fraction of the strand breaks while there was no repair of the DNA strand breaks in cells irradiated in the presence of the chemical.     

Radioprotective effectiveness of gas hypoxic mixture GHM-10 in experiments on dogs

In experiments on 128 dogs (males and females) weighing 7-24 kg it was demonstrated that inhalation of gas hypoxic mixture containing O2 (10%) and N2 (90%) decreased significantly the level of PO2 in radiosensitive tissues and exerted a radioprotective effect on the exposed animals (60Co, doses of 2.8, 3.5-3.8 and 4.2 Gy, DMF = 1.3). At a dose of 8 Gy the average life of animals increased from 6.2 +/- 0.8 days (control) up to 9.3 +/- 1.1 days after the application of GHM -10.     

Radiosensitization in multifraction schedules. I. Evidence for an extremely low oxygen enhancement ratio

Stable monolayers of contact-inhibited C3H 10T1/2 cells were used in multifraction radiation experiments to measure the oxygen enhancement ratio (OER) at low doses/fraction under conditions where cell cycle effects (repopulation, redistribution) were minimal. Consistent with there being a dose-dependent reduction in the OER at low doses, an extremely low OER of 1.34 was measured after 20 fractions of 1.7 Gy every 12 h. The sparing effects of fractionating radiation doses were not apparent for cells irradiated under hypoxic conditions (i.e., multifraction survivals were lower than acute single-dose values) until doses exceeding 15 Gy were reached. This result suggested a deficiency in the recovery from sublethal and/or potentially lethal damage might exist after hypoxic irradiations, thereby reducing the OER. The capacity to repair potentially lethal damage was found to be nearly the same after hypoxic as compared to aerobic irradiations. However, there was an apparent absence of sublethal damage repair by 10T1/2 cells between two hypoxic irradiations which could be a major contributing factor to the extremely low OER value measured in this multifraction schedule.     

射线诱导在体造血细胞凋亡的量时效关系的研究

以4—10Gy射线在体损伤的小鼠为模型,应用DNA电泳和流式细胞术等方法证实细胞凋亡是射线损伤在体骨髓造血细胞的途径之一,发现射线诱导的造血细胞凋亡有明显的量效和时效关系。4、6、8和10Gy照射后,细胞凋亡发生率均表现为升高-降低过程,各剂量诱导的凋亡发生率峰值分别出现在照后12、8、4和4h,6和8Gy诱导的凋亡发生率已达最高水平,约为30％,10Gy诱导的凋亡反而要低。上述结果表明,诱导细胞凋亡是射线损伤骨髓造血细胞的一个重要途径,而且凋亡的发生率受照射剂量和照后时间的影响。因此,深入研究射线诱导的细胞凋亡,将有助于揭示射线损伤造血功能的机理。     

Evaluation of the radioprotective effect of total gaseous hypoxia based on the criteria of delayed radiation damage

Breathing with gas mixture containing 6-8% of oxygen during whole-body and large-field irradiation of mice diminishes the radiation-induced life-span shortening (DMF = 2.2) and decreases the degree of canescence (DMF = 1.5), the frequency and severity of nephro- and cardiosclerosis (DMF = 1.5), and the probability of occurrence of pleura and pericardium edemas provoked by cardiopulmonary insufficiency (DMF = 1.4). The fact that hypoxic hypoxia retains its high radioprotective efficiency in relation to the delayed effects of radiation is important for radiotherapy of tumors.