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At least 523 records · Page 29Linked to original sources
PubMed2003

Imperceptible effect of radiation based on stable type chromosome aberrations accumulated in the lymphocytes of residents in the high background radiation area in China.

Cytogenetic investigation of stable type aberrations (translocations) was performed with our improved methods in 6 children and 15 elderly persons in a high background radiation area (HBRA) in China, and in 8 children and 11 elderly persons in a control area. The total numbers of cells analyzed in elderly persons were 68,297 in HBRA and 35,378 in controls and in children were 45,535 in HBRA and 56,198 in controls. On average 5138 cells per subject were analyzed. The variation in the frequencies of translocations per 1000 cells was small in children while it was large in elderly persons. No significant difference was found in the frequencies between HBRA and control (P > 0.05, Mann-Whitney U test). On the other hand, correlation between age and translocation frequencies was significant at the 1% level (rs = 0.658 with 37DF, Spearman rank correlation test). The contribution of an elevated level of natural radiation in HBRA in China to the induction of stable type chromosome aberrations does not have a significant effect compared with the contribution of chemical mutagens and/or metabolic factors. The present study suggests that the probability of the risk of causing malignant and/or congenital diseases by the increased amount of radiation is imperceptible in HBRA where the level of natural radiation is 3 to 5 times higher than that in the control area.

Aged↗
PubMed2001

Contribution of base lesions to radiation-induced clustered DNA damage: implication for models of radiation response.

Biophysical modeling of radiation-induced DNA damage shows that significant yields of clustered DNA damage are formed after energy deposition by a single radiation track. To date, the majority of studies on radiation-induced DNA damage in cells have concentrated on determination of the yields of single- and double-strand breaks (DSBs), the latter representing one type of clustered DNA damage. It was recognized, however, that clustered DNA damage, which does not contain a DSB, might contain a combination of DNA base lesions and single-strand breaks in proximity. This mini-review discusses some of the recent experimental data confirming the induction of non-DSB, clustered DNA damage by radiation.

DNA↗
PubMed2002

Influence of prior exposure to low-dose adapting radiation on radiation-induced teratogenic effects in fetal mice with varying Trp53 function.

Teratogenesis in tails and limb digits of fetal mice with varying Trp53 status was examined after exposure of pregnant females to 4 Gy gamma radiation with and without a prior 30-cGy exposure. Prior low-dose exposure modified the teratogenic effects of radiation in a manner dependent upon Trp53 status and gestation time. A 4-Gy exposure on gestation day 11 resulted in tail shortening and digit abnormalities. A 30-cGy exposure 24 h prior to a 4-Gy radiation exposure on day 11 reduced the extent of both digit abnormalities and the tail-shortening effects in Trp53(+/+) fetuses and also reduced tail shortening in Trp53(+/-) fetuses, but to a lesser extent. However, the pre-exposure enhanced the tail-shortening effects of 4 Gy in Trp53(-/-) fetuses. In contrast, a 30-cGy exposure given 24 h prior to a 4-Gy exposure on gestation day 12 had no effect on the reduced tail length resulting from the 4-Gy exposure of Trp53(+/+) or Trp53(+/-) fetuses, but it partly protected Trp53(-/-) fetuses against reduced tail length. A 4-Gy exposure alone on day 12 did not result in any increase in the frequency of digit abnormalities in Trp53(-/-) fetuses so any protective effect of the preirradiation could not be detected. However, the preirradiation did result in protection against in digit abnormalities in Trp53(+/-) fetuses. We conclude that radiation-induced teratogenesis reflects both Trp53-dependent and independent processes that lead to apoptosis, and these respond differently to prior adapting doses.

Abnormalities, Radiation-Induced↗
PubMed1996

Comparison of whole brain radiation therapy and locally limited radiation therapy in the treatment of solitary brain metastases from non-small cell lung cancer.

The benefit and risk of whole brain radiation therapy (WBRT) compared to locally limited radiation therapy was assessed in 61 patients with solitary brain metastases from non-small cell lung cancer without an unresectable active primary lesion or systemic dissemination in the other organs. Twenty-three patients received local irradiation (Group A), and 38 patients received whole brain irradiation with or without local irradiation (Group B). The survival was significantly better in Group A than in Group B (p < 0.05), with median survivals of 83.1 and 30.7 weeks, respectively. One-year local recurrence rates were 7% in Group A and 21% in Group B, but the difference was not statistically significant. The 1-year distant recurrence rate was similar at 18%. Radiation-induced dementia occurred in two patients in Group A (8.7%) and seven in Group B (18.4%), but was not statistically significant (p = 0.30). There is no obvious benefit and possible disadvantages of WBRT compared to local irradiation for the population of patients investigated in this study. Intraoperative radiation therapy or stereotactic radiosurgery without WBRT should be considered in the patients with solitary brain metastases.

Adult↗
PubMedDate not supplied

Hyperthermia enhancement of radiation response and inhibition of recovery from radiation damage in human glioma cells.

Three human glioma cell lines were tested for the effectiveness of hyperthermia and thermal radiosensitization. Thermal sensitization was evaluated from the perspective of increased radiosensitivity as well as inhibition of recovery from radiation damage. The three glioma cell lines tested showed large shoulders on the radiation survival curve and a large capacity for recovery of potentially lethal radiation damage. Hyperthermia caused radiosensitization in all three cell lines, which was primarily characterized by the reduction of the survival curve shoulder with moderate decreases in the survival curve slope. The radiosensitization was dependent on the time and temperature of the hyperthermia treatment. At 45 degree C for 60 min the shoulder of the radiation survival curve could be completely eliminated and the degree of enhanced cell killing at the 2 Gy level ranged from factors of 10 to 20 under the various conditions. When hyperthermia was given to cells which were irradiated and then plated immediately, or delayed for 8 h before plating to allow recovery, hyperthermia was found to cause radiosensitization under both conditions. In addition, when the hyperthermia dose was increased the difference between the immediate plating and the delayed plating survival curve decreased and for 45 degrees C for 60 min this difference was completely eliminated, concomitantly with the elimination of the survival curve shoulder. These data indicate that hyperthermia may play a role in radiosensitization for the treatment of human glioma.

Brain Neoplasms↗
PubMed1987

Radiation pneumonitis and fibrosis following split-course radiation therapy for lung cancer. A radiologic and physiologic study.

Radiographic signs of radiation pneumonitis and fibrosis were assessed and pulmonary function monitored in lung cancer patients after two different split-course radiation therapy schedules, one with a rest interval of 3 weeks and the other with a rest interval of 5 weeks, the total radiation dose being the same in both treatments (55 Gy/20 fractions/7 or 9 weeks). Post-mortem findings were analysed when available. Spirometric measurement of vital capacity, determination of diffusing capacity for carbon monoxide (DL) and alveolar volume with the single breath technique, and determination of regional distribution of lung perfusion by two different techniques, radiospirometry and gamma camera digital display following intravenous injection of 133Xe, were carried out before and at various times after the completion of irradiation. Of the physiologic parameters, only DL showed a significant decrease 6 as well as 9 months post-treatment (p less than 0.05). No difference between the two treatment schedules could be shown with regard to grade or time pattern of radiologic changes or decrease in DL. The findings suggest that measurement of DL may be of value in monitoring patients included in research protocols for radiation therapy of lung cancer as well as in selection of patients for this treatment.

Aged↗
PubMed1977

[Analysis of errors of radiation relay--errors of relay controller using the radiation scaler (author's transl)].

Radiation relay using the radiation scaler acts at the time when the output of the scaler comes to a set value. By this action, the stop valve in infusing line (or exhausting line) is closed and the increment (or decrement) of liquid level of tank is stopped. Same as radiation relay using CR rate meter, switching time of the relay of this system varies statistically due to the statistical property of radioactivity. In this paper, the probability density function of the switching time is calculated on the assumption that the pulse train is the Poisson process. Then, the relation between the switching time and the uncertainty in the stop level is examined under a constant incremental (or decremental) velocity of liquid level. Using these results, the minimum intensity of radiation which is necessary to obtain a given accuracy is calculated and the optimum scaling time is given to minimize the uncertainty corresponding to various velocity of liquid level.

Computers↗
PubMed2002

The treatment of unresectable, locally advanced non-small-cell lung cancer: a radiation therapy perspective with an emphasis on the trials of the Radiation Therapy Oncology Group.

Radiation therapy used as a single modality in the treatment of locally advanced non-small-cell lung cancer is potentially curative, but long-term survival rates are disappointing due to both locoregional and distant failures. The trials of the Radiation Therapy Oncology Group (RTOG) have been instrumental in defining the optimal management of this disease. The conclusions and questions posed by the RTOG are discussed in this review. The conclusions of this review include the following: chemotherapy combined with radiation therapy improves survival in patients with good performance, with increased toxicity; concurrent chemoradiation is superior to sequential chemoradiation. Questions remain regarding the value of the addition of induction or consolidation chemotherapy to concurrent chemoradiation, the value of three-dimensional conformal radiation therapy, the role of altered fractionation regimens in combination with chemotherapy, the optimal chemotherapeutic regimen, and the role of novel biologic agents.

Journal Article↗
PubMed2003

[Usefulness of intensity-modulated radiation therapy for breast conserving radiation therapy: a three-dimensional treatment planning system comparison of irradiation methods].

Until recently, conservative radiation therapy of breast cancer using a wedge-filter combined with rectangular tangential irradiation was widely carried out. This method of irradiation creates uniform dose distribution in the target, minimizing the radiation dose to the lung. However, this method of irradiation results in many cases in which the amount of dose in the irradiated area differs as a result of the shape and size of the breast. It is necessary to prevent excessive doses from reaching the lung. IMRT ensures a uniform dose to the target. Therefore, IMRT was examined because of the possibility that the normal tissue dose can be effectively utilized in cases of conservative radiation therapy of breast cancer by providing a minimum dose. To compare the irradiation of each method of rectangular tangential irradiation, an electronic compensator (ELC), and IMRT, which uses Dynamic MLC, we evaluated target dose uniformity, standard deviation, and target differential DVH in 13 examples. We evaluated the lung dose of the irradiated side (V(30), 30 Gy volume) of the lung to the volume of the lung on the irradiated side based on the report of Hernando.(6)) With this method of irradiation, irrespective of the difference in the shape and size of the target, dose uniformity with ELC was very good. IMRT can reduce the lung dose in comparison with the other irradiation methods. However, it is apt to cause a high-dose area in the irradiation field. In addition, it affects the target and the skin-extracting contour, and the dose to the skin surface declines. Although ELC cannot offer lung doses that are as low as those of IMRT, most of the 13 examples planned for cure with ELC showed rates of 22% of V(30) and below. In conservative radiation therapy of breast cancer, ELC is more effective than the rectangular tangential irradiation method and IMRT.

Breast Neoplasms↗
PubMed1997

[Effects of different components of serum from radiation, burn and combined radiation-burn injury on L-type calcium channel of cultured myocardial cells].

The effects of different components of serum from radiation, burn and combined radiation-burn injury on the activity of L-type calcium channel in cultured myocardial cells were investigated in this study. The results revealed that the serum from different injury groups could all activate the L-type calcium channel of cultured myocardial cells. These changes altered the calcium level in cells, which might be an important cause of dysfunction in cardiovascular system. Among the components of postinjury serum, the effect of high molecular components (> 8-10 kD) was not significant, whereas low molecule (< 8-10kD) and lipid components were the major effective components. The low molecule of postinjury serum affected not only on the opening activity of L-type channel, but also on the state of molecular movement in the membrane. The effect of serum lipids from injury groups could be depressed by SOD, which suggests that there may be free radical reactions during the serum lipids effect on calcium channel. The effects of serum and its components from combined radiation-burn group were the most intensive, and those from radiation injury were the weakest. The nature of the toxic material in serum remains to be further investigated.

Animals↗
PubMed2003

[Risk management from the perspective of the radiation protection officer. Consequences of new radiation protection laws in hospitals].

The implications of the new radiation protection law for hospitals. The novel German radiation control regulation ("Roentgenverordnung") came into effect on July 1, 2002. It contains a number of new rules the majority of which clearly take a more restrictive approach towards the application of ionising radiation. New dose thresholds have been set for control and monitoring areas and written working instructions are now required for all areas of radiology departments. The new regulations also require the indication for a radiological examination to be checked by a radiologist who has completed a formalised training in radiation protection. This particular aspect will have serious implications for every day practice. The necessity of having a trained radiologist on site for 24 hours a day will cause problems in many hospitals. The power of the responsible external independent control body ("ärztliche Stelle") has been increased as have the duties of medical physicists. The performance of x-ray examinations that are not medically indicated is punishable by law as bodily harm. This as well as many other regulations are currently being checked for applicability in terms of guidelines, the majority of which are not yet available.

Germany↗
PubMedDate not supplied

[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.

Cell Survival↗
PubMedDate not supplied

Radiation and thermal characteristics of mouse lymphoma cells and their radiation-sensitive mutant.

Radiation and thermal characteristics of L5178Y cells and their radiation-sensitive mutant M10 cells were studied by the colony-forming method and the dye-exclusion method using eosin-Y. Although M10 cells were remarkably radiation-sensitive compared with L5178Y cells, it was difficult to cause interphase death of M10 after a large dose of irradiation. After heat treatments, L5178Y cells revealed more cell destruction and were stained well by eosin-Y, but it was relatively difficult to produce cell destruction of M10 cells, which showed poor staining by eosin-Y. When assayed by the colony-forming method, M10 cells were also heat-resistant compared to L5178Y. The dye-exclusion rate was closely correlated with cell survival after hyperthermia of L5178Y cells, suggesting that this is a simple method of detecting the thermosensitivity and thermotolerance of cancer cells. The difference in survival of L5178Y cells and M10 cells after combined treatment with gamma irradiation and hyperthermia was smaller than with gamma irradiation alone. It was also found that there was a relationship between radiation-induced interphase death and hyperthermia-induced interphase death, and that interphase death accounted for a major part of cell death caused by hyperthermia in mouse leukemia cells.

Animals↗
PubMed1979

Radiation necrosis of the brain: correlation between patterns on computed tomography and dose of radiation.

Recurrent symptoms after radiation therapy of a brain tumor are not always the result of regrowth of the neoplasm but may represent radiation necrosis of the brain. Seventeen patients with proven cerebral radionecrosis are included in the present study. In five patients who received 5,000 to 5,500 rads, areas of radiation necrosis of the brain were shown on computed tomography (CT) as low density lesions with no mass effect or contrast enhancement. In 12 patients who received 6,000 to 7,000 rads, radionecrosis was shown on the CT scans either as a localized mass with contrast enhancement or as diffuse low density, isodense, or high density lesions with no mass effect but with occasional enhancement. In all cases, the lesions coincided well with volumes of the brain that received a threshold dose of radiation determined from the isodose reconstruction maps.

Brain↗
PubMed1984

[Effect of gamma radiation on the immunobiological and immunochemical properties of cholera exotoxin. I. Change in the biological activity of nonpurified cholera exotoxin as affected by ionizing radiation].

Crude cholera exotoxin (filtrate toxin) was irradiated with increasing doses of gamma radiation. A significant drop in enterotoxicity, in the activity of the permeation factor and a decrease in toxicity were shown to occur as radiation doses increased. Radiation doses of 50-70 kGy were found to completely inactivate enterotoxicity in liquid toxic preparations. A higher radioresistance of dried preparations in comparison with liquid ones was registered: inactivation occurred at 150-200 kGy. Different batches of the initial filtrate toxin had varying radiosensitivity. The sterilizing effect of gamma radiation was achieved at doses of 20 kGy for liquid preparations and 30 kGy for dried preparations. During the prolonged storage of the irradiated preparations of crude toxin (the term of observation being 1.5 years) at different temperatures no reversion of toxicity was found to occur, while their immunogenic properties remained unchanged.

Animals↗
PubMedDate not supplied

[Clinical characteristics of radiation sickness with radiation exposure of different parts of the human body].

The clinical picture of radiation sickness of 139 radiological patients exposed to local irradiation of the head, chest and stomach with efficient doses of 210 rad was examined. It was found that at fractionated local irradiations the clinical symptom-complex of radiation sickness was identical to that seen as a result of total-body irradiation. During head irradiation the major symptom was headache and during stomach irradiation nausea. The severity level of radiation damage measured with respect to the clinical symptom-complex as a whole with the aid of the bioinformation model was similar during irradiations of the head and stomach much higher during irradiation of the chest. During head and stomach irradiations the severity level of radiation damage was proportional to the efficient dose. During chest irradiation there was no correlation between the severity level and the exposure to doses of 210 rad.

Abdomen↗
PubMed1994

[Evaluation of radiation and non-radiation factors in the development of lung cancer in radiochemical plant employees].

Five hundred workers of a nuclear facility (162 cases of lung cancer and 338 healthy subjects) were examined on a case-control basis using the logical regression method and 10 radiation and non-radiation factors. Five significant factors were identified. The following rick values were obtained for them: tobacco smoking-6.6; plutonium-associated pneumosclerosis-4.6; plutonium incorporation-3.1; chronic non-specific diseases of the lung-2.1 and gamma ray exposure-1.6. Radiation-associated rick was under 25%, while that of non-radiation factors not less than 70%.

Aged↗
PubMed1994

Role of vitamin A in modulating the radiation-induced changes in intestinal disaccharidases of rats exposed to multifractionated gamma-radiations.

PURPOSE: The aim of this investigation was to determine whether pre- or post-administration of vitamin A will be effective in reducing the radiation-induced alterations in intestinal disaccharidases in rats. MATERIAL AND METHODS: Rats were subjected to fractionated whole-body irradiation (20 x 0.5 Gy). Intestinal lactase activity as well as maltase and sucrase activities were assessed. Vitamin A was administered at daily intraperitoneal dose of 15,000 IU/kg body weight for 7 days prior to radiotherapy and thereafter twice weekly throughout therapy up to 7 days post irradiation. RESULTS: In irradiated rats a marked decrease in intestinal lactase activity to about one-fourth of those in non-irradiated rats was observed. In addition, a significant reduction in maltase and sucrase activities to one half of the control group was observed. The application of vitamin A significantly improved the radiation-induced inhibition of intestinal enzymes. Pretreatment application of vitamin A is more efficient to protect against radiation injury than a posttreatment application. CONCLUSIONS: The usage of vitamin A for modulation of radiation-induced changes in intestinal enzymes provides sufficient protection against treatment side effects induced by large volume radiotherapy.

Animals↗