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At least 919 records · Page 51Linked to original sources
PubMed2002

[Effect of ultraviolet radiation on the immune system and the effect of exogenous photochemoprotecive agents on the ultraviolet radiation induced immunosuppression].

Ultraviolet radiation (UVR) of the UVB- and UVA-region suppresses immunity and in the dose relation manner it induces cutaneous or systemic state of immunotolerance. It was proved by the successful experimental transplantation of a tumor graft to the skin of UV-radiated animals and on the other side by unsuccessful attempts at skin contact-sensitization. UVR induces this condition either by direct inhibition of antigen-presentating function of the Langerhans cells, or indirectly by the stimulation of secretion of immunomodulatory cytokines in keratinocytes. UVR inhibits also functions of the natural killer cells in apoptotic and lytic cell-processes. It directly correlates with carcinogeneity in conditions of the dysbalance in developing expression of the tumor-suppressive gene p53, mutated by the irradiation and that of bcl-2 gene preventing apoptotic changes in somatic cells. Moreover, the immunosuppression is enhanced by the isomerization of urocanic acid and by the development of damaged DNA-photoproducts. Also various neuropeptides, namely propiomelanocortin, have their partial role in immunomodulation. Local photoprotective substances prevent UVR-penetration into the skin and thus block the immunosuppressive effects in relation to their chemical composition and to the SPF (solar photoprotective factor) value. Their effect depends on the width of the UVR-region blocked, which should include both the UVB and UVA band, and also on the concentration, chemical stability and on the method of their application.

Animals↗
PubMed1975

The properties of bird feathers as converse piezoelectric transducers and as receptors of microwave radiation. II. Bird feathers as dielectric receptors of microwave radiation.

The characteristics of bird feathers as receptors of microwave fields were investigated in the 10- to 16-GHz region. Experiments were conducted coupling the specimen (feather) to a length of waveguide which served, together with other microwave components, as a primary detector. Microwave power radiation patterns were measured both in the presence and in the absence of the specimen. Results indicated a substantial increase in the microwave power collected in the forward direction and a decrease of the radiation pattern beam width when the feather was present. Fruthermore, some experiemental evidence indicated the possibility of inducing piezoelectric effects in the specimen by audiofrequency pulse-modulated microwave fields. These results are important in view of (i) the fundamental role that feathers play in the life of birds and (ii) the influence of environmental factors on bird behaviour.

Animals↗
PubMed1988

A randomized clinical trial comparing radiation therapy v radiation therapy plus cis-dichlorodiammine platinum (II) in the treatment of locally advanced non-small cell lung cancer.

Cis-Dichlorodiammine platinum (II) (cis-DDP) was demonstrated to be a potentiator of radiation therapy (RT) in experimental tumor models and in cultured cells. To assess the effectiveness of a combined modality treatment including RT and a weekly low-dose administration of cis-DDP, from January 1986 to June 1987, 95 patients with unresectable locally advanced non-small cell carcinoma of the lung (stage IIIa, b) were randomized for study. Fifty patients received RT alone at doses of 50 Gy; 45 patients received the same RT plus cis-DDP 15 mg/m2 IV weekly. An overall response rate of 50% and 64% was observed in the RT and RT + cis-DDP group, respectively. No statistically significant differences were detected with regard to median survival time (11 months for RT v 16 months for RT + cis-DDP) and progression-free interval (7 months in the RT arm v 9 months in the RT + cis-DDP arm), but the patterns of the first failure appeared to be affected by treatment. In fact, a lower number of intrathoracic relapses was observed in the RT + cis-DDP arm (12 in the RT + cis-DDP v 23 in the RT arm). Toxicity was mild and the feasibility of this schedule must be remarked. A better local control of disease can be obtained using cis-DDP as a radiation potentiator, but the true influence of this combined modality treatment on the length of survival, and the optimal cis-DDP timing and dosage are still to be evaluated in further clinical trials.

Carcinoma, Non-Small-Cell Lung↗
PubMedDate not supplied

[Quantitative evaluation of the combined effect of external gamma radiation and internal alpha radiation from 239Pu based on biochemical indices of the organs of the rat immune system].

The combined effect of external gamma-radiation (137Cs, 103-26 mC/kg) and incorporated alpha-radiation (239Pu nitrate, 93-9.3 kBq/kg body mass) was estimated by changes in the nucleic acid metabolism and the number of cells in rat thymus, spleen and bone marrow. The data obtained were processed using a model of multiplicate action of the factors which is equivalent, in the case of low effects, to a traditional model of additive effects. The results of the combined action of the two factors may be estimated by the coefficient of the interaction and the coefficient of the enhancement of the effects.

Alpha Particles↗
PubMed1988

Administration of radiation or cyclophosphamide versus alternated radiation and cyclophosphamide treatment of primary tumor and pulmonary metastases.

The experimental tumor 3924A in ACI rats metastasizes to the lungs, but this is rarely apparent unless the life span of the animal is increased by treatment of the tumor. Pulmonary metastases were prevalent among animals given radiation daily or in multiple fractions per day over periods of 3-4 weeks at total doses ranging from 3,000 to 11,250 rad. Multiple doses of cyclophosphamide, each at the level that was lethal to 10% of the animals, did not cure the primary tumor but appeared to delay the appearance of metastases. Treatment schedules that alternated the delivery of multiple 250-rad fractions of radiation during 2-day periods with cyclophosphamide at a dose of 150 mg/kg for a total of three courses were effective in curing the primary tumor and eliminating pulmonary metastases.

Animals↗
PubMed1987

[Results of radiation therapy of extranodal non-Hodgkin's lymphoma of the head and neck--a study of the Japan Lymphoma Radiation Therapy Study Group].

During the years 1972-81, 168 patients with extranodal Non-Hodgkin's lymphoma localized in the head and neck were treated with radiation. Five-year survival rates were 62% in stage I, 56% in stage II, and 91% in diffuse well-differentiated lymphocytic, 77% in diffuse mixed, 52% in diffuse poorly-differentiated lymphocytic and diffuse histiocytic each. Marginal relapse was rare after radiation therapy, but relapses were not infrequently noticed in distant extranodal sites. Bone and/or soft tissue relapses were frequently noticed in patients with lesions initially located in the nasal cavity, paranasal sinus and oral cavity.

Adolescent↗
PubMed1985

A study of dynamic development in radiolesion and cell death of eukaryotes after exposure to ionizing radiation--the visualization of the dynamic reaction by means of cytochemical method with lactate dehydrogenase (LDH) as a nuclear marker and radiation-induced nuclear anomalization by an ultramicrostructural manifestation: a dynamic explanation.

The present work deals with the radiation effect on adult rats suffering from acute, whole-body irradiation with cobalt-60 gamma rays of dosages 100R and 300R respectively. The morphological alteration of the lymphocytic nucleus and exhibition of cytochemical reaction of LDH in intra- or extra-nuclear region has been observed at the end of predetermined time intervals after irradiation. A close relationship between the percentage of damage of the lymphocytic nucleus and that of positivity of LDH reaction is seen from their variations with time parallel. From technical color microphotographs which exhibit cytochemical reactions, the existence of enzyme LDH in the nucleus so far obscure has been visually recognized. The events happening in enzymic reaction and the leakage of enzyme across the nuclear envelope reflect the dynamic nature. The ultrastructural alteration of nuclear anomalization confirms the dynamic development of inducing radiolesion. The experimental facts inspire us to attempt an explanation of cellular radiolesion and cell death owing to ionization radiation in light of the dynamic concept.

Animals↗
PubMed1985

[Planning combined radiation therapy of rectal cancer taking into account the biological effect of the radiation].

Biologically equivalent doses with various single values, fractionation, irradiated areas, relative biological efficacy, the time of radiation therapy for schedules of intracavitary and gamma-beam radiotherapy were determined for concomitant radiotherapy of rectal cancer patients. A radiation effect implementation factor was introduced making it possible to sum up equivalent dose values in critical points and to obtain equivalent isodose distributions.

Brachytherapy↗
PubMedDate not supplied

[Enhancement of the biological effectiveness of low-energy quantum radiation. Microdosimetric basis for a selective radiation effect on chromosome material in cells].

Microdosimetric data are presented indicating the possibility of a selective action of ionizing radiation on the chromosomal material of cells using low-energy electrons and photoelectrons formed, as the result of the photoeffect, on the incorporated or native atoms inside DNA upon irradiation with low-energy quantum radiation ("X-activating" effect). A presumed biological effectiveness of the "X-activating" effect on B-16 melanocarcinoma, with bromine and iodine incorporated into the DNA molecule, was estimated.

Bromine↗
PubMed1983

Correlation between initial and long-term responses of spontaneous pet animal tumors to heat and radiation or radiation alone.

Most early-phase testing of new therapeutic modalities involves analysis of initial tumor response as opposed to estimation of long-term response. In this study, the validity of initial response rates to predict long-term responses was examined for tumors treated with radiotherapy alone compared with heat combined with radiotherapy. A total of 130 pet animals with either squamous cell carcinomas, melanomas, fibrosarcomas, mammary adenocarcinomas, or mast cell sarcomas were randomized to receive either radiation alone (XRT) or heat + radiation (delta + XRT). Responses to treatment were evaluated by response rates and response duration. The complete response (CR) rates were consistently higher for delta + XRT than for XRT across different histology groups. The combined therapy led to prolonged tumor response in all histological subgroups except melanomas, which had a longer response duration when treated with XRT alone (p = 0.043). This was in spite of a relatively high CR rate in that group (100% versus 12.5% for delta + XRT and XRT, respectively). In contrast, while no significant improvement in CR rate was observed for dermal squamous cell carcinomas treated with delta + XRT (XRT = 52.9%; delta + XRT = 68.8%), a significant improvement in response duration was noted (p = 0.002). These are two examples where CR rate did not predict long-term response. When all histological subgroups were combined (except melanomas), the CR rate was higher (p less than 0.001), and response duration was prolonged (p = 0.031) for delta + XRT compared to XRT alone.

Animals↗
PubMed1983

Comparison of mutagenicity and induction of sister chromatid exchange in Chinese hamster cells exposed to hematoporphyrin derivative photoradiation, ionizing radiation, or ultraviolet radiation.

Cell culture studies have been performed to compare the mutagenic potential and the induction of sister chromatid exchanges for hematoporphyrin derivative photoradiation, ionizing radiation, and UV radiation. The mutation frequency in Chinese hamster ovary cells at the hypoxanthine-guanine phosphoribosyltransferase locus was measured using resistance to 6-thioguanine. Phenotypic expression time prior to mutation selection was also examined. Treatment with either X-rays or UV was effective in producing mutants resistant to 6-thioguanine, but treatment with hematoporphyrin derivative photoradiation (at comparable toxicity levels) did not induce any mutagenic activity above background levels. The hematoporphyrin derivative incubation and photosensitization conditions used in this study did induce sister chromatid exchanges at frequencies comparable to those induced by X-rays but at lower frequencies than for UV treatments.

Animals↗
PubMed1993

A mathematical formalism describing the yield of radiation-induced single- and double-strand DNA breaks, and its dependence on radiation quality.

The purpose of this paper is to describe mathematically the observed dependence of the number of DNA single-strand breaks (SSBs) per unit dose on radiation quality (e.g., LET) by invoking the concept of matrix saturation (i.e., the fact that a nucleotide can be the site of one SSB only and therefore further local energy deposition is wasted), and to show that, based on this, one obtains a characteristic variation of the yield of DNA double-strand breaks with variation of LET, in qualitative agreement with certain experimental determinations. The formalism developed here makes use of methodology from the field of integral geometry, introduced by Kellerer [Radiat. Prot. Dosim. 31, 9-16, 1990] in microdosimetry.

DNA↗
PubMedDate not supplied

Radiation therapy of bone metastases in the elderly: a multicentric survey of the Italian "Geriatric Radiation Oncology Group".

External radiation therapy (ERT) has been reported to be the elective treatment of symptomatic bone metastases. A nationwide survey on the use of ERT in elderly patients with bone metastases has been conducted by the Italian "Geriatric Radiation Oncology Group" with a three-fold aim: define the state of the art of ERT, evaluate the analgesic efficacy and identify the optimal dosage and schedule, if any. 347 patients aged 70 or over, treated in 29 different institutions for a period of six months were analyzed. Conclusive results were: a significant pain relief achieved shortly after ERT completion; an improvement in the quality of life; a decrease in the dose of analgesics and consequently, a reduction in treatment-related costs. Unfortunately the optimal treatment schedule remains unidentified; ERT was neither aggressive nor toxic in this series of elderly patients.

Aged↗
PubMed1998

[A clinical evaluation of combination therapy with radiation, MCNU, carboplatin and IFN-beta or with radiation, MCNU, carboplatin, etoposide and IFN-beta for malignant gliomas].

In this study, we examined the clinical course and prognosis of 32 patients with malignant glioma (17 patients with anaplastic astrocytoma, 15 patients with glioblastoma) treated with the MIC regimen (radiation, MCNU, carboplatin and IFN-beta) or MICE regimen (radiation, MCNU, carboplatin, etoposide and IFN-beta). Ten patients were treated with the MIC regimen and 22 patients with the MICE regimen. The patients treated with the MIC and MICE regimens exhibited no significant difference in clinical background factors. The response rate was 50.0% among the 8 evaluable patients treated with the MIC regimen, and 40.0% among the 20 evaluable patients treated with the MICE regimen. The first- and second-year survival rates for the MIC regimen were 40.0% and 30.0%, and those for the MICE regimen were 68.2% and 36.4%. The overall first- and second-year survivals were 59.4% and 33.9%, respectively. The 50% survival time was 8.6 months for the MIC regimen, 14.9 months for the MICE regimen, and 13.4 months overall. There was no significant difference in response rate or survival period between the group treated with the MIC regimen and that treated with the MICE regimen. Age, histological grade of malignancy, radicality of surgery and total dose of irradiation did not affect length of survival. The only factors significantly related to length of survival were response to the induction therapy and performance of maintenance therapy. These results did not demonstrate the superiority of either the MIC or MICE regimen to other regimens previously reported for the treatment of glioma. In addition, etoposide was found not to improve the efficacy of this type of combined chemoradiation therapy.

Adolescent↗
PubMed2002

Thyroid cancer incidence among liquidators of the Chernobyl accident. Absence of dependence of radiation risks on external radiation dose.

The increase of thyroid cancer incidence rate among children living in the Chernobyl contaminated territories of Belarus, Russia and Ukraine has widely been accepted. Our current work deals with thyroid cancer incidence in the cohort of liquidators (99024 persons) living in 6 regions of Russia: North-West, Volgo-Vyatsky, Central-Chernozemny, Povolzhsky, North-Caucasus and Urals. In the period 1986-1998, a total of 58 thyroid cancer cases were detected in this cohort. We found a statistically significant increase of the thyroid cancer incidence rate in liquidators as compared to the baseline (male population of Russia) level (SIR=4.33, 95% CI: 3.29; 5.60). It was demonstrated that there is no dependence of incidence rates due to external radiation exposure (ERR/Gy=-2.23, 95% CI: -4.67; 0.22).

Adolescent↗
PubMed1980

Analyses of differential sensitivities of synchronized HeLa S3 cells to radiations and chemical carcinogens during the cell cycle. Par V. Radiation- and chemical carcinogen-induced mutagenesis.

8-Azaguanine(8AG)-resistant mutations induced by X-rays, ultraviolet radiation (UV) and a chemical carcinogen, 4-hydroxyaminoquinoline 1-oxide (4-HAQO) were examined during the cell cycle of synchronized HeLa S3 cells. Mutants induced by 400 R of X-rays occurred in a higher frequency in the X-ray-SENSITIVE Gl-S boundary phase than in the X-ray-resistant G1, S and early G2 phases. 8AG-resistant mutants induced by treatment with 10(-5) M 4-HAQO for 20 min appeared in a higher frequency in the early to middle S phases than in the other phases. In the case of UV, however, we found no significant difference in the induced mutation frequencies during the cell cycle, because the mutation frequencies induced by the UV doses (0-20 J/m2) used were too low for detection of the difference. These results suggest that there is a close correlation between the critical damage induced in DNA molecule(s) at the DNA-synthetic phase in the cell cycle and mutagenesis, because mitotic cells have a low mutability in spite of their high radio-sensitivity.

4-Hydroxyaminoquinoline-1-oxide↗
PubMed1981

A mouse-cell mutant sensitive to ionizing radiation is hypermutable by low doses of gamma-radiation.

The mutant mouse lymphoma cell M10, which is sensitive to methyl methanesulfonate and ionizing radiation, was compared with the parental L5178Y cells for mutation induction after gamma-irradiation. The rate of induced mutations to 6-thioguanine resistance in L5178Y cells was 2-3 X 10(-7) per R, as determined after exposures ranging from 25 to 500 R. The induced mutation frequency per unit dose per locus in M10 cells was about 4 times higher than that in L5178Y cells at the lower doses of exposure (25-75 R), but it declined sharply at the higher doses of gamma-rays (100-150 R). The rate of induced mutation per unit cell killing in M10 cells was nearly the same as that in L5178Y cells when they were compared at the levels of lower cell killing.

Animals↗