Effect of low doses of external and internal ionizing radiation on proteinases of cells in the rat cerebral cortex of rats]

Single external gamma-irradiation in a dose of 0.5-2 Gy as well as the long-term (30 days) internal irradiation caused by the everyday influx of Cs-137 and Sr-85 isotopes to the organism have been studied for their effect on the activity and properties of histone-specific proteinase from the nuclei of the rat brain cortex cells. It is found out that external irradiation induces a dose-dependent increase of the activity during the first 24 hours after irradiation followed by its decrease 7-30 days later. Internal irradiation induces a decrease of the enzyme activity at the 30th day as well. Certain specificity of the studied indices depending on the type of irradiation has been also observed.     

The radiosensitivity of kidney colony-forming cells: a short-term assay in situ in the mouse

A short-term colony assay for renal tubule epithelium has been developed. Uranyl nitrate (UN) is a heavy metal nephrotoxin that induces acute tubule necrosis followed by a large compensatory increase in the rate of cell proliferation in the nephron. UN was used to precipitate latent damage following renal irradiation. Using a subcapsular colony count at 14 days after unilateral irradiation, a single-dose cell survival curve was obtained with a D0 of 4.2 +/- 0.3 Gy. High-dose irradiation of an exteriorized kidney resulted in a survival curve which was biphasic, with a plateau in survival between 18 and 40 Gy. Subtraction of this plateau level from all the survival data gave D0 values of 2.5 +/- 0.2 Gy (data analyzed between 7.5 and 16 Gy) or 2.0 +/- 0.2 Gy (over range 12-16 Gy). The D0 value obtained at 20 months after bilateral (or unilateral) kidney irradiation, without the use of UN, was 2.9 +/- 1.1 Gy (over range 10-14 Gy).     

Participation of Poly(ADP-ribose)-polymerase of nuclear matrix in DNA repair

The poly(ADP-ribose)-polymerase activity of brain and liver cell nuclei is changed during X-irradiation of rats. In the nuclear matrix, poly(ADP-ribose)-polymerase activity increases at a low dose of irradiation (1.7 Gy) and decreases at a high dose (6.7 Gy). A significant part of the activity of nuclear NMN-adenylyltransferase, a key enzyme for biosynthesis of NAD (the substrate of poly(ADP-ribose)-polymerase), has been found in the nuclear matrix. An interrelation between ADP-ribosylation taking place on the matrix level and eukaryotic cell DNA repair is suggested.     

Activity of purine enzyme metabolism in rat thymocytes after irradiation and after administration of riboxine

It has been established, that the total X-ray irradiation of animals takes influence upon the functional activity of key enzymes of adenine nucleotides metabolism: adenylatekinase, AMP deaminase, 5'-nucleotidase, adenosine deaminase and purine nucleoside phosphorylase in rat's thymocytes. The increase of activity of the investigated enzymes is observed in our experiment, except 5'-nucleotidase, which activity is authentically decreasing after irradiation (1.0 and 7.78 Gy). The injection of the preparation riboxine to experimental animals 15 min prior to the exposure has normalized the purine exchange enzymes activity.     

Effect of gamma irradiation on insulin receptor interaction in rat erythrocytes

An insulin receptor interaction has been studied in rat erythrocytes after whole-body gamma irradiation (1 Gy). Specific binding of insulin was found to increase 30 days following irradiation against the background of a decreased immunoreactive insulin concentration in the blood. A change in the postirradiation activity of insulin receptors is considered as a manifestation of the homeostatic mechanism of "up" regulation in exposed animals.     

Effect of the substances "Ammivit" and "cerloplasmin" on lipid peroxidation products level and of antioxidant system indicators under irradiation

It has been shown, that the total X-ray irradiation in the dozes of 0.5 and 1 Gy influences on the content of lipid peroxidation products and enzymatic activity of antioxidant system in rat spleen and thymus cells. The influence of preparations "AMMIVIT" and "Ceruloplasmin" on these processes is investigated also. So, the animals feeding by the vitamin concentrate "AMMIVIT" have lead to increase of MDA level (a final product of lipid peroxidation) and the overactivity of some antioxidant enzymes in rat spleen and thymus cells. Injection of the preparation "Ceruloplasmin" to experimental animals up 1 hour before the irradiation has normalized LPO intensity and activity of AO enzymes.     

The effect of a high-intensity radiation exposure on the brain function of monkeys. The postradiation changes in brain bioelectrical activity

In experiments with Macaca fascicularis it has been found that changes in the total bioelectric activity of the brain within the EEG range that occur during the first 60 min following whole-body irradiation with a dose of 45 Gy (6.5 Gy/s) are interrelated with the dynamics of nervous and psychic activity of the exposed animals, exhibit a definite stereotype of their development (disorganization of rhythms: generalized synchronization of biopotentials; and development of synchronous processes), and coincide in time with the main stages of the development of the clinical picture of the acute postirradiation period (noncoordinated stimulation, sopor or coma, and partial recovery).     

Prevention of type I diabetes by low-dose gamma irradiation in NOD mice

Pretreatment with nonlethal, low-dose irradiation has been shown to have a protective effect against oxidative injury in animal tissues. Since oxidative injury of tissues is known to be a major cause of many human diseases, we examined the effect of low-dose irradiation on the progression of type I diabetes in mice. Nonobese diabetic (NOD) mice were treated with gamma irradiation and the progression of the disease was monitored. An elevated level of glucose in urine was first detected at 15 weeks of age in the control NOD mice, whereas the detection was delayed as long as 7 weeks when the mice received a single dose of 0.5 Gy total-body irradiation between 12 and 14 weeks of age. The greatest effect was observed in the mice irradiated at 13 weeks of age. The increase in blood glucose and decrease in blood insulin were effectively suppressed by irradiation at 13 weeks of age. Both suppression of cell death by apoptosis and an increase in superoxide dismutase (SOD) activity were observed in the pancreas 1 week after irradiation. The results indicate that treatment with 0.5 Gy gamma rays suppresses progression of type I diabetes in NOD mice. This is the first report on the preventive effect of low-dose irradiation on disease progression.     

The effect of a high-intensity radiation exposure on the brain function of monkeys. The postradiation changes in the EEG response to rhythmic photostimulation]

In experiments with monkeys (Macaca fascicularis) it has been shown that whole-body irradiation with a dose of 45 Gy (6.5 Gy/s) causes considerable changes in the EEG response to rhythmic photostimulation (PS). These changes are: reduction of the desynchronizing effect of PS with regard to a background rhythmicity; decrease in the reception rate of the rhythms of light flashes (RLF); narrowing of the RLF frequency range; and increase in the reaction momentum. The postirradiation changes in the EEG response to PS are considered as a manifestation of inhibition of the cortex functional activity and impairment of sensory information processing in the brain.     

Early changes in the ultrastructure of axodendritic synapses in the rat sensorimotor cortex following whole-body irradiation with high-dose fast neutrons

Changes in morphometric parameters have been established in axodendritic synapses of sensorimotor cortex of adult mature rats exposed to neutron irradiation. Neutron irradiation dose and summarized dose rate were 10 Gy and 0.35 Gy, respectively. The changes were observed 0.25, 1, 3, 6 and 24 hours after irradiation. The observations suggest an increase in synaptic activity, with the range of irradiation action and functional characteristics decreasing in subsequent time periods.     

Transferrin binding of bone marrow cells and metabolic activity of erythrocytes after 5 Gy irradiation

The effect of total body irradiation (5 Gy) on functional mouse erythroid lineage has been studied. The transferrin binding capacity by bone marrow cells and the activity of glycolytic regulatory enzymes and intracellular levels of 2,3 bisphosphoglycerate in peripheral blood erythrocytes have been determined. Results obtained along one year post-irradiation period suggest a complete recovery in the erythroid cell lineage with respect to the biological endpoints investigated.     

Radio-protective effects of melatonin against irradiation-induced oxidative damage in rat peripheral blood

During radiotherapy, ionizing irradiation interacts with biological systems to produce free radicals, which attacks various cellular components. The hematopoietic system is well-known to be radiosensitive and its damage may be life-threatening. Melatonin synergistically acts as an immunostimulator and antioxidant. In this study we used a total of 120 rats with 20 rats in each group. Group 1 did not receive melatonin or irradiation (Control group), Group 2 received only 10 mg/kg melatonin (Mel group), Group 3 exposed to dose of 2 Gy irradiation (2 Gy Rad group), Group 4 exposed to 8 Gy irradiation (8 Gy Rad group), Group 5 received 2 Gy irradiation plus 10 mg/kg melatonin (Mel +2 Gy Rad group) and Group 6 received 8 Gy irradiation plus 10 mg/kg melatonin (Mel+8 Gy Rad group). Following exposure to radiation, five rats from each group were sacrificed at 4, 24, 48 and 72 h. Exposure to different doses of irradiation resulted in a dose-dependent decline in the antioxidant enzymes activity and lymphocyte count (LC) and an increase in the nitric oxide (NO) levels of the serum. Pre-treatment with melatonin (10 mg/kg) ameliorates harmful effects of 2 and 8 Gy irradiation by increasing lymphocyte count(LC) as well as antioxidant enzymes activity and decreasing NO levels at all time-points. In conclusion 10 mg/kg melatonin is likely to be a threshold concentration for significant protection against lower dose of 2 Gy gamma irradiation compared to higher dose of 8 Gy. Therefore, it seems that radio-protective effects of melatonin are dose-dependent.     

The effect of He-Ne laser radiation on the survival of HeLa cells subjected to ionizing radiation]

A monolayer of HeLa cells, at the stationary phase of growth, exposed to He-Ne laser radiation (632.8 nm; 100 J/m2) either 5 min or 60 min prior to gamma irradiation (0.1-10 Gy; 6.75 Gy/min), or 5 min after irradiation has been investigated. With a 5-min interval between irradiation sessions (both sequences) the survival curves are virtually the same as those for gamma-irradiated cells only. With He-Ne laser radiation delivered 60 min before gamma irradiation with doses exceeding 5 Gy, a fraction of radioresistant cells is identified whose D0 is almost twice as high as D0 of basic cell mass (3.6 and 1.7 Gy respectively. The survival curve becomes a two-component one. A hypothesis is proposed that He-Ne laser radiation activates, in some cells, the processes that promote the repair of radiation damages.     

碳离子辐照对四尾栅藻光合色素及抗氧化活性的影响

为了探讨重离子辐照对微藻的生物学效应,实验研究了不同剂量碳离子辐照（10~80 Gy）对四尾栅藻（Scenedesmus quadricauda）光合色素及抗氧化活性的影响,分别测定了辐照后短期内其叶绿素a（Chl a）、叶绿素b（Chl b）和类胡萝卜素含量、脂质过氧化物丙二醛(MDA)含量及超氧化物歧化酶（SOD）活性。结果显示：(1)较低剂量（10~20 Gy）辐照后,光合色素含量变化较小或无显著变化,中等剂量（40~60 Gy）辐照后,光合色素含量显著升高,之后又回落,恢复至正常水平,高剂量（80 Gy）辐照后,光合色素含量明显降低,不能恢复正常;(2)低剂量（10 Gy）辐照后,丙二醛（MDA）含量显著上升,8 h后出现回落,到24~48 h时,回升至正常水平,较低剂量（20 Gy）辐照后,MDA含量瞬时有所下降,到24~48 h时,回升至正常水平,中等至高剂量（40~80 Gy）辐照后,MDA含量降低,24~48 h时显著升高,不能恢复正常;(3)低剂量（10 Gy）辐照后,超氧化物歧化酶（SOD）活性显著上升,8 h后出现回落,恢复正常,中等剂量（20~60 Gy）辐照后,SOD活性显著上升,到48 h时回落至正常水平,高剂量（80 Gy）辐照后,SOD活性无明显上升,到48 h时,活性明显降低,不能恢复正常。     

The cytogenetic damage, radiosensitivity and adaptive response in children living in the different districts of Moscow

The spontaneous level of blood lymphocytes with micronuclei (MN), the sensitivity to 1.0 Gy irradiation and adaptive response (AR) after adaptive irradiation with a dose of 0.05 Gy 5 hr later have been studied in children population living in different districts of Moscow. It was shown that spontaneous frequency of cells with MN, the sensitivity to 1.0 Gy acute irradiation and the AR manifestation have significant differences in samples taken from children living in different districts. The individual variability is significant also. In each group of children the individuals with the enhanced radiosensitivity after adaptive irradiation have been observed. In conformance with the data of radioecological inspection the radiation situation in different Moscow districts is quite safe on overage but in some districts the spontaneous level of lymphocytes with MN, and radiosensitivity after 0.05 Gy irradiation were enhanced, the AR was not found.     

Metallothionein induction as a potent means of radiation protection in mice

A striking resistance to lethal damage from a single dose of 6-8 Gy of X rays has been found in mice which had received various pretreatments to induce metallothionein (MT) synthesis in the liver prior to irradiation. Mice were injected with manganese (10 mg Mn/kg) or cadmium (3 mg Cd/kg) salt subcutaneously, or a patch of dorsal skin (2 X 2 cm2) was excised 1 or 2 days prior to irradiation. The increased tolerance of these mice to radiation was established by a marked decrease of mortality rate, an increase of mean survival time, a reduction of weight loss, and a smaller decrease in the number of leukocytes as compared with the control group. The LD50/30 for control mice was 6.3 Gy, while the corresponding values for the groups pretreated with Mn, Cd, and skin excision were 7.5, 7.7, and 7.9 Gy, respectively. The normal level of MT in mouse liver was approximately 25 micrograms/g tissue. This level increased 2.5- to 3-fold 24 h after 6.3 Gy irradiation. The MT levels of mice pretreated with Cd, Mn, and skin excision were increased 8-, 5-, and 7-fold, respectively, prior to irradiation as compared with the preirradiation control. These results indicate that the induction of MT in mouse liver is a significant factor in the mechanism of protection against radiation.     

Effect of X irradiation on adenosine triphosphate and glucose-6-phosphate dehydrogenase in the CaNT mouse tumor

The levels of adenosine triphosphate (ATP) in the transplantable CaNT murine tumor grown in CBA mice at various times following 5, 10, and 15 Gy X rays (100 kVp) were increased within 45 min. Maximal ATP levels occurred at 2.5 h following the 10 Gy dose (3.8 times that of unirradiated controls), returning almost to control levels by 13 h after irradiation. The specific activity of glucose-6-phosphate dehydrogenase (G-6-PDH) after 10 Gy increased about 1.5-fold 1 h after irradiation, returning to control levels by 48 h. It is suggested that the increased ATP following irradiation might play a major role in energy provision when cellular repair processes are able to operate. The increased G-6-PDH activity after irradiation may reflect enhanced metabolism associated with cellular repair mechanisms.     

Cytogenetic study of the bone marrow and peripheral blood lymphocytes in monkeys in long-term gamma irradiation

A comparative study of chromosome structures of bone marrow and peripheral blood cells has been carried out in 8 rhesus macaques (2-7 years of age), 4 of which survived after prolonged low-capacity (3.87 microA/kg) gamma irradiation, the total dose being 7.97 Gy (LD50/60). It has been established that prolonged low-capacity gamma irradiation was of a high mutagenic activity. Various tissues of irradiated monkeys showed differences in the frequency (4 months) and types (4-33 months) of aberrations within the period of 4 to 33 months following irradiation. Mutagenic effect characteristic of the early period after the irradiation was retained in the peripheral blood of irradiated monkeys within the period of observation.     

Effect of adrenaline on the succinate dehydrogenase activity of peripheral blood lymphocytes of rats following exposure to ionizing radiation

In experiments with albino mongrel female rats, the influence of adrenaline on succinate dehydrogenase (SDG) activity in the peripheral blood lymphocytes of irradiated and intact animals has been investigated. Two minutes after the intraperitoneal administration of adrenaline (1 mg/kg) to intact rats SDG activity sharply rises and 3-4 min it drastically falls. In 6 to 8 min the second peak in the enzyme activity is registered. Twenty minutes after irradiation of rats in the cranio-caudal direction with a dose of 75 Gy delivered to head, the reaction to adrenaline, manifested by the rise in SDG activity, is absent.     

Changes after irradiation in the number of mitotic cells and apoptotic fragments in growing mouse hair follicles and in the width of their hairs

The hair follicle or its differentiated product, the hair, which represents the linear historical record of the follicular proliferative activity, could provide a biological dosimeter of value for dose distribution determinations after accidental exposure. Here we present some further studies on irradiated mouse hair follicles and hair, and discuss the difficulties in obtaining similar data for humans. The incidence of cell death in the follicles has been shown elsewhere to be maximum 12 h after irradiation, and it increases with dose. Here we confirm that doses of 0.2-0.4 Gy can be readily detected. We show here that there is only a little more cell death in the larger follicles even though they contain many more cells and mitotic figures. About one-third of all the dead cell fragments in a follicle can be seen in a good longitudinal follicle section. Mitotic activity declines progressively with dose in the large follicles, which start with more mitotic cells, showing the dose-dependent changes most readily. The dead cells are morphologically identical to apoptotic cells at the level of the light microscope, and they fragment into several bodies, the number of which increases with dose. The total number of apoptotic bodies or fragments in whole large follicles increases almost 100-fold over a range of 1.3 Gy (from 0.2 to 1.5 Gy) and about tenfold over the range 0.2-0.5 Gy. The estimated number of dead (apoptotic) cells increases about sevenfold over the same 1.3-Gy range. The width of the middle portion of the broadest, awl, hairs measured 12 days after irradiation decreases with increasing dose. About 80% of the hairs show an obvious reduction in width after 2 Gy and the effects of a dose of about 1 Gy can be detected. The width of the hair is reduced by 10-14% per Gy. A comparison has been made between BDF1 (black) and BALB-c (albino) mice. The large follicles contain similar numbers of mitotic cells, but the BALB-c mice are more sensitive both in terms of the radiation-induced apoptosis and in terms of a reduction in awl hair width.