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At least 19 recordsLinked to original sources
PubMed1992

Down-regulation of cell cycle control genes by ionizing radiation.

The cellular responses to ionizing radiation include growth arrest, DNA repair, and lethality. However, little is known about the signaling events responsible for these responses. The present studies have examined the effects of ionizing radiation on the expression of genes involved in cell cycle control. The results demonstrate that the treatment of asynchronous cells with 20 Gy ionizing radiation is associated with transient down-regulation of the cdc2, cyclin A, cyclin B, and cdc25 genes. This effect was associated with transient induction of the c-jun gene. RNA stability studies demonstrate that the down-regulation of gene expression following ionizing radiation exposure is at least in part due to a decrease in transcript half-life. Other studies were performed with elutriated cells enriched for populations in G1 and S phases. Treatment of G1 enriched cell populations with 10 Gy resulted in a selective decrease in cyclin B mRNA levels, whereas this effect on cyclin B expression was less pronounced at 5 Gy and undetectable at 1 Gy. Similar results were obtained with S phase enriched cells. Taken together with clonogenic survival studies, these findings indicate that down-regulation of cell cycle control gene expression is associated with lethality, whereas lower doses of ionizing radiation have little, if any, effect on the expression of these genes. The findings also suggest that DNA damage may activate signaling events which regulate expression of cell cycle control genes.

CDC2 Protein Kinase↗
PubMedDate not supplied

[Inactivation of isogenous strains of Bacillus subtilis and their mixtures by ionizing radiation].

Resistance to ionizing radiation of vegetative cells, spores and dehydrated cultures was studied with isogenous strains of Bacillus subtilis with defects in the repair systems. In vegetative cells of different classes of the recombination deficient mutants, DL90 was 31-35% of LD90 of the wild type cells. Differences in radiosensitivity of the vegetative cells were more pronounced cf. the spores and dehydrated cells: LD90 of rec- mutants was 55-88%; LD90 of uvr- mutants was 120% of LD90 of the parent bacterial cells.

Bacillus subtilis↗
PubMed1992

Fixation for biological ultrastructure. II. Cross-linking of bovine serum albumin by nanosecond pulses of ionizing radiation.

Very large doses of ionizing radiation were delivered quickly to concentrated albumin solutions by pulses of 500 keV in air. The electrons penetrated the aluminium foil bottom of the test cell and into the solution. A dose of 4.6 Mrad (4.6 x 10(4) Gy) produced a gel in the albumin solution comparable to the long-term effect of 0.36% glutaraldehyde in the same albumin solution. The cross-links created by the radiation leading to gel formation are probably irreversible and quite different from those leading to gelation in the glutaraldehyde-albumin reaction. Single large pulses of ionizing radiation may be useful for fast fixation of cells and tissues for microscopy.

Equipment Design↗
PubMed1976

The new special names of SI units in the field of ionizing radiations.

New SI units for ionizing radiations have been recommended by the internation Commission on Radiation Units and Measurements (ICRU). These are the becquerel (symbol Bq), equal to the second to the power -1, and the gray (symbol Gy), equal to the joule per kilogram. It was recommended that the roentgen be replaced as the unit of exposure by the coulomb per kilogram (C/kg), for which no new name was proposed. The ICRU recommends that the units rad, roentgen, and curie be gradually abandoned over a period of ten years and that preparatory steps to this end be taken as soon as possible by various national and international bodies in order to facilitate a smooth, safe, and efficient transition.

Radiation Dosage↗
PubMed1978

Studies on the sterilization of pharmaceutical base materials with ionizing radiation and ethylene oxide.

The use of ionizing radiation and ethylene oxide for the sterilization of pharmaceutical base materials of animal origin, used to produce organopreparations, was studied. The materials included liver extract, pancreas extract, dried thyroid and intrinsic factor. The effective sterilizing doses for the examined materials and dependence between effective ionizing radiation dose and primary contamination were determined.

Animals↗
PubMed1992

Involvement of reactive oxygen intermediates in the induction of c-jun gene transcription by ionizing radiation.

Previous work has demonstrated that the cellular response to ionizing radiation includes transcriptional activation of the c-jun gene. The signaling events responsible for this response, however, remain unclear. The present studies have examined the effects of ionizing radiation on c-jun expression in a variant of HL-60 cells, designated HL-525, which is deficient in protein kinase C (PKC)-mediated signal transduction. The results demonstrate that these cells express low levels of PKC alpha and PKC beta transcripts and exhibit an attenuated induction of c-jun expression following treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA). In contrast, HL-525 cells respond to ionizing radiation with an increase in c-jun mRNA which is more pronounced than that in wild-type HL-60 cells. These cells similarly respond to ionizing radiation with increased expression of the jun-B, jun-D, c-fos, and fos-B genes. Nuclear run-on assays demonstrate that X-ray-induced c-jun expression in HL-525 cells is regulated by increases in the rate of c-jun gene transcription. Moreover, mRNA stability studies in irradiated HL-525 cells demonstrate that the half-life of c-jun transcripts is prolonged compared to that in wild-type cells. Studies with N-acetyl-L-cysteine (NAC), an antioxidant, suggest that X-ray-induced transcriptional activation of the c-jun gene is mediated at least in part through the formation of reactive oxygen intermediates (ROIs). In this context, H2O2 also induced c-jun expression in HL-525 cells, and this effect was inhibited by NAC.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Nucleus↗
PubMed1992

Mitogenic signal transduction: a common target for oncogenes that induce resistance to ionizing radiations.

We hypothesized that resistance to ionizing radiations accompanying neoplastic transformation caused by some oncogenes was due to common biochemical pathways affecting the mechanism of mitogenic signal transduction. In order to verify this hypothesis, we studied the formation of mitogenic second messengers in cells transformed by oncogenes that induce radioresistance. We observed an increase of diacylglycerol which activates protein kinase C, an increase of phosphatidylcholine metabolism, with a concomitant decrease of inositol lipid metabolism. Our data show that sensitivity to ionizing radiations was inversely related to the intracellular level of diacylglycerol; study of signalling alterations in spontaneous tumors could provide predictive indications about the responsiveness of neoplasia to radiation therapy.

3T3 Cells↗
PubMed1977

Infrared spectral characterization of peptidic material produced by ionizing radiation in aqueous cyanides.

Oligomers formed by ionizing radiation in aqueous cyanide solutions, under various experimental conditions, have been characterized by infrared spectroscopy. IR bands appear in the region known to be characteristic for amides and peptides. The results are discussed in relation to radiation-induced formation of peptidic material and the potential role of ionizing radiation as an energy source for some processes in prebiotic molecular evolution.

Cyanides↗
PubMed1992

Effects of ionizing radiation and beta-adrenergic stimulation on the expression of early response genes in rat parotid glands.

There is little known about the regulation of gene expression in rat parotid glands after exposure to ionizing radiation. The present studies investigate the effects of in vivo ionizing radiation, with subsequent stimulation of beta-adrenergic receptors by isoproterenol, on parotid gland function and on the expression of the early response genes, c-fos, c-jun, and jun B. Ionizing radiation diminished parotid gland weight and saliva output. Treatment of irradiated rats with isoproterenol increased the gland weight to levels similar to those in nonirradiated rats. However, such treatment had no effect on saliva output as indicated by measurements of parotid salivary flow rate. Irradiation alone increased the expression of c-fos, c-jun, and jun B. The combination of irradiation and isoproterenol had an additional effect on the levels of c-fos and jun B mRNAs and proteins particularly at earlier experimental times (1 to 8 h). Isoproterenol alone induced high levels of c-fos and jun B mRNA but not of c-jun mRNA. However, c-jun mRNA was induced markedly by radiation and 8 h of isoproterenol treatment, indicating a combined effect on c-jun gene expression. These observations suggest that the expression of the proto-oncogenes c-fos, c-jun, and jun B is probably regulated through differential signal transduction pathways which may be activated by these external stimuli and may be associated with functional changes induced in the rat parotid gland by ionizing radiation and by ionizing radiation and isoproterenol.

Animals↗
PubMed1992

Ionizing radiation stimulates unidentified tyrosine-specific protein kinases in human B-lymphocyte precursors, triggering apoptosis and clonogenic cell death.

Very little is known regarding the effects of ionizing radiation on cytoplasmic signal transduction pathways. Here, we show that ionizing radiation induces enhanced tyrosine phosphorylation of multiple substrates in human B-lymphocyte precursors. This response to ionizing radiation was also observed in cells pretreated with vanadate, a potent protein-tyrosine-phosphatase (PTPase) inhibitor, and phosphotyrosyl [Val5]angiotensin II phosphatase assays showed no decreased PTPase activity in irradiated cells. Thus, enhanced tyrosine phosphorylation in irradiated B-lymphocyte precursors is not triggered by inhibition of total cellular PTPase activity. Immune-complex kinase assays using anti-phosphotyrosine antibodies demonstrated enhanced protein-tyrosine kinase (PTK) activity in the immunoprecipitates from irradiated cells, and the PTK inhibitors genistein and herbimycin effectively prevented radiation-induced tyrosine phosphorylation. Immune-complex kinase assays on irradiated and unirradiated B-lymphocyte precursors using antibodies prepared against unique amino acid sequences of p59fyn, p56/p53lyn, p55blk, and p56lck demonstrated that these Src-family tyrosine kinases were not the primary PTKs responsible for enhanced tyrosine kinase activity in the anti-phosphotyrosine antibody immunoprecipitates or for enhanced tyrosine phosphorylation of multiple substrates. Thus, our findings favor the hypothesis that ionizing radiation induces enhanced tyrosine phosphorylation in B-lymphocyte precursors by stimulation of as yet unidentified PTKs. Tyrosine phosphorylation appears to be an important proximal step in radiation-induced apoptosis and clonogenic cell death because inhibition of PTK prevents DNA fragmentation and loss of clonogenicity of irradiated B-lymphocyte precursors. Since PTKs play myriad roles in the regulation of cell function and proliferation, the activation of a PTK cascade, as detailed in this report, may explain some of the pleiotropic effects of ionizing radiation on cellular functions of B-lymphocytes and their precursors.

Apoptosis↗
PubMed1992

No adaptive response of Chinese hamster ovary cells to low doses of ionizing radiation.

Chinese hamster ovary (CHO) cells that had been exposed to very low doses of ionizing radiation from incorporated tritiated thymidine or X-rays were shown not to be more resistant to the induction of chromatid aberrations by a subsequent higher dose of ionizing radiation than previously untreated cells. The adaptive response to ionizing radiation was absent both in cells challenged with high doses of X-rays (1.25 Gy) and in cells post-treated with thermal neutrons (0.5-1 x 10(12) n/cm2). In agreement with these observations in CHO cells we were unable to demonstrate an adaptive response to X-rays also in human lymphocytes from five different donors.

Adaptation, Physiological↗
PubMed1977

[Radiation therapy in patients with electronic cardiac pacemakers: interferences with the pacemaker's function by ionizing radiation and other sources of disturbances (author's transl)].

In the course of radiation therapy and connected diagnostical measures ionizing radiation and other sources of disturbance may interfere with the function of permanent pacemakers. The conditions of such hazards are investigated in theory and practice making allowance for the different susceptibility to trouble of various models of permanent pacemakers. It appears that no extension of long-term follow-up of the cardiac pacemaker's function is needed with regard to possible late effects of ionizing radiation, but that the follow-up of pacemaker-patients during their first period of treatment should not be neglected, since other sources of electronic interference may be present. Routine checks as radiotherapy installations should also include possible sources of disturbance to electronic pacemakers.

Aged↗
PubMedDate not supplied

[Modification of the body's resistance to acute ionizing radiation by synthetic beta-carotene].

Radiomodifying efficiency of short-term and chronic medicinal and treatment-prophylactic enrichment of rations with artificial beta-carotene, administered at single doses of 0.1-10.0 mg, were studied after acute external gamma-irradiation of adult nonlinear and Wistar rats (0.029 Gy/s) or female SBA mice (0.0037 Gy/s), where the absorbed dose was equal to 8-3 Gy or 9.9-9.5 Gy, respectively. Suspension of beta-carotene paste in olive oil accelerated death of rats irradiated at doses of 8 and 7 Gy (P = 0.04), and shortened their lifespan. At a dose of 6 Gy single and long-term enrichment of rations with beta-carotene decreased the rate of rat death within 30 days from 33.3% to 16.7% (P = 0.14) and 3.3% (P = 0.01), while their life time was increased from 48 days to 67 days (P = 0.05) and 508 days (P = 0.01). beta-Carotene was found to affect favourably the radiation-induced (5 Gy) leukocytopenia, and decreased thymus mass (6 Gy) and body weight (8 Gy). In treatment-prophylactic enrichment with beta-carotene of mice (9.9 Gy) ration their survival was increased from 15% to 30% and lifespan from 14.4 days to 28.9 days (P = 0.05). During medicinal or treatment-prophylactic courses of beta-carotene death of mice (9.7 Gy) was decreased from 75% to 35% (P = 0.01) or 60% and life time was increased from 16.7 days to 22.17 days or 39.9 days (P = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1975

[State of hemodynamics, according to radiocardiographic data, in persons working in contact with ionizing radiation sources].

The presented results illustrate the study of the cardiovascular system by means of radiocardiography conducted in normal individuals working in contact with sources of ionizing radiation. The study includes 51 persons in the test group and 42 in the control group that was similar to the test one in terms of age, sex and type of work performed, with the only exception that these in the control group had no contact with ionizing radiation. Persons working under the effect of ionizing radiation displayed a moderate increase in the stroke and minute index and the circulating blood volume, with the blood flow rate somewhat decelerated. The changes were deeper in those with over 5 years of service, and in those with functional changes in the nervous system, like neurocirculatory dystonia. The moderate level of these reactions and their reversibility permit to interpret them as an adaptative reaction to the effect of low doses of ionizing radiation.

Angiocardiography↗
PubMedDate not supplied

A review of the processes by which ultrasound is generated through the interaction of ionizing radiation and irradiated materials: some possible applications.

The production of acoustic waves following the absorption of energy deposited by ionizing radiation, with a consequent production of localized thermal spikes has been confirmed by a number of papers published in the physics literature. This paper reviews the basic theory and presents most of the supporting experimental data. Some of the experimental methods used and the results obtained are summarized. In addition to the rather straightforward and routine use of acoustic phenomena produced by ionizing radiation for the detection and measurements of such radiation, there are some special applications that appear to be especially attractive for medical physics. Some of these are unique to ionizing radiation in that the amplitude of the ultrasound wave is proportional to the energy deposited in small volumes at localized sites of these interactions, while others derive from methodologies already in use with nonionizing radiations. The detection and measurement of this ultrasonic radiation could possibly lead to methods for the study of such fundamental phenomenon as track structure, precision localization of therapeutic treatment beams, and even the possible imaging of internal anatomic structures to provide on-line portal images.

Hot Temperature↗
PubMed1992

Brain myelination in rats treated with ionizing radiation in utero.

Effects of ionizing radiation on brain myelination and some physical development parameters were studied in laboratory rats (Fisher F-344 inbred strain). Rats were treated with three different doses of radiation (150 rad, 15 rad, and 6.8 rad) delivered on the 20th day of prenatal life. Exposure to 150 rad reduced body, brain, ovary, kidney, heart and spleen weights. Prenatal exposure to 150 rad of radiation reduced the cerebral cortex weight by 22 percent at 30 days of age, and 20 percent at 52 days of age which caused a reduction in cerebral cortex myelin content by 20 and 23 percent at the ages of 30 and 52 days respectively. This dose did not affect the myelin content of the cerebellum or the brain stem, or the myelin concentration (mg myelin/g brain tissue) of the cerebral cortex, cerebellum, and the brain stem. The cerebral cortex weight of the 15 rad treated rats was reduced at the age of 30 days. Exposure to 15 rad, and 6.8 rad did not affect either the myelin content or the myelin concentration of these brain areas.

Animals↗