Radiosensitivity of Ehrlich ascites carcinoma clonogenic cells irradiated with Co60 gamma rays in hypoxic conditions

A study was made of the survival rate of Ehrlich ascites clonogenic cells on the 7th day following inoculation depending on 60Co-gamma-radiation dose delivered under hypoxic and oxygenating conditions in vitro. In both cases the survival curves had a small shoulder and an exponential part. The oxygen enhancement ratio determined as a ratio of D0 for hypoxic (6.59 Gy) and oxygenated (2.06 Gy) cells was 3.2.     

On (3)H beta-particle and (60)Co gamma irradiation of aqueous systems

The chemistry of water and aqueous solutions is very different after irradiation with (3)H beta particles and high-energy electrons or (60)Co gamma rays. The greater the linear energy transfer (LET) of the medium for (3)H beta particles compared to high-energy electrons or (60)Co gamma rays leads to an increased local concentration of reactants. There is an increased amount of intratrack chemistry, which reduces the escape yield of and OH by about 50%, but increases the yield of H(2) by about 50% and of H(2)O(2) by about 35%. Analysis of stochastic-diffusion kinetic calculations employing simulated track structures reveals that the yield of H(2) produced by diffusion-kinetic processes increases significantly for (3)H beta particles compared to (60)Co gamma radiation, while production of H(2) by sub-picosecond processes is essentially the same. In both (3)H beta-particle and (60)Co gamma radiolysis, the reactions + and are equally important in the production of H(2). In the former case, each reaction has a yield of approximately 0.18, and in the latter a yield of approximately 0.08. In neutral water, the reaction (H + H) is negligible. The yield of Fe(III) in (3)H beta-particle radiolysis of the Fricke dosimeter is much smaller than in radiolysis with more energetic electrons. Simulations show that this change is primarily due to the reduced escape yield of H, formed from the scavenging of by the bulk H(3)O(+) of the acid. The chemical differences observed in experiments, and in calculations, reflect the underlying structure of the electron tracks: Examination of the track structure simulations demonstrates that primary events are considerably more well-separated in high-energy electron tracks compared to (3)H beta-particle tracks.     

Hypodontia in the beagle after perinatal whole-body 60Co gamma irradiation

As part of a long-term study to evaluate health effects of pre- and postnatal irradiation, dental development was examined. Beagles were irradiated in utero at 8, 28, or 55 days postcoitus or postnatally at 2, 70, or 365 days postpartum. Whole-body 60Co gamma radiation doses ranged from 0 to 3.8 Gy. There was an age-dependent dose-related increase in premolar hypodontia for animals irradiated at 55 days postcoitus or 2 days postpartum with doses of 0.83 Gy or higher and for those irradiated at 28 days postcoitus with 1.2 Gy or higher.     

The effect of the dose rate on the development of rat pups under chronic gamma irradiation]

Chronic exposure of rat pups to gamma radiation, during their intensive growth, at a dose rate of 0.01, 0.11 and 0.5 cGy/day did not affect their development throughout a two-month period of observation. At a dose rate of 12.9 cGy/day rat growth was inhibited during the first 15 days. With further exposure at the same dose rate (over a period of up to five months) the rate of rat pup growth was restored, which indicated the presence of adaptation processes.     

Role of bone marrow stroma in the phenomenon of hybrid resistance]

In the site of hemopoiesis produced by implantation of an irradiated bone marrow plug beneath the kidney capsule all dividing hemopoietic cells were of recipient origin, as shown by karyologic analysis. In such implants hybrid resistance was of the donor's type. It is suggested that the migrating cells of hemopoietic origin, including lymphocytes and macrophages, do not participate in producing the hybrid resistance.     

Radiosensitivity of colony-forming units of dog bone marrow in agar cultures]

Radiosensitivity of the bone-marrow colony-forming cells was determined by a modified method of hemopoietic cells cloning in vivo in semihard agar gel in diffusion chambers. Do for the commited precursor cells of granulopoiesis (CFUc) was 144 +/- 14.8 rad (n = 0.8), and Do for the precursor cells forming "stellate" colonies of fibroblast-like cells (PFUf) was 468 +/- 35.8 rad (n == 0.9). A conclusion was drawn that PFUf were referred to the class of stromal precursors of the hemopoietic organs. This system can be applied for a simultaneous study of the hemopoietic and stromal precursor cells in dogs.     

Micronucleus formation in the bone marrow cells of chronically irradiated mice with subsequent acute gamma irradiation]

With the use of the micronuclear test method it has been shown that mice preirradiated with gamma rays at a low dose rate exhibit a decreased frequency of chromosome aberrations induced in bone marrow cells by subsequent acute exposure to gamma radiation as compared to mice not subjected to preliminary irradiation. Such animals have a higher radioresistance with respect to the survival rate. The results obtained suggest the possibility of induction by ionizing radiation, at a low dose rate, of adaptive repair response at the organism level.     

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.     

Recovery of CFUc in rat bone marrow after prolonged fractionated irradiation with various total doses

The rate and the degree of recovery of committed precursors of granulocytes and monocytes (CFUc) following long-term fractionated irradiation were a function of a cumulative radiation dose. In rats exposed to doses of 9.7 and 19.4 Gy the number of CFUc of myelokaryocytes and granulocytes of blood reached the control values after 1-3 months. The increase in CFUc of animals exposed to a dose of 29.1 Gy was transient and did not provide the recovery of granulocytopoiesis.     

Growth of murine bone marrow under various oxygen conditions in media buffered with HEPES

Increased plating efficiencies were observed for marrow granulocyte-macrophage precursor cells (CFU-gm) cultured in an experimental system at reduced gas-phase oxygen concentrations. However, only a small component of this increase was attributable to decreased oxygen. The changed media buffering system was the more dominant factor contributing to increased plating efficiency, suggesting that other factors in addition to a reduction in oxygen may influence clonogenicity.     

Radiosensitivity of mouse bone marrow and spleen CFUdc during gamma-irradiation in different oxygenation conditions

After exposure in vitro and in situ CFUdc of CBA mouse bone marrow and spleen were characterized by the comparable parameters of radiosensitivity and oxygen-dependent modification: the values of D0 for bone marrow and spleen cells were 1.31 and 1.35 Gy (in vitro) and 1.36 and 1.37 Gy (in situ), and the values of the oxygen effect were 2.3 and 2.5, respectively.     

The antiradiation properties of betamide under conditions of sublethal and lethal gamma irradiation]

Bone marrow cellularity in the femur, mass and cellularity of the spleen and small intestine, and nucleic acid concentration in the leukocyte mass of blood were investigated after the intraperitoneal administration of betamide (500 mg/kg) 15 min before gamma irradiation of mice with doses of 4, 7 and 9 Gy. The number of myelokaryocytes and splenocytes in the protected animals was shown to exceed considerably that in the controls on days 3 and 9 after irradiation with the three doses. With betamide injected on day 9 following irradiation the number of nucleated cells of the small intestine was larger and the nucleic acid concentration in leukocytes higher than the same indices in the irradiated control.     

Sinusoids of the bone marrow stroma in the human iliac bone

Results of histological and ultramicroscopic investigations of sinusoid vessels are presented. Interrupted structure of the basal membrane and continuous endothelial lining are revealed. Endotheliocytes of two types are described. At places of blood cells migration functional activity of endothelium is increased and the basal membrane is absent. A suggestion is made that the endothelial cells directly influence hemopoiesis.