Mixed Neutron-gamma Radiation Research Articles

A high-pressure ionisation chamber to measure the mean neutron energy and the gamma ray dose fraction of an unspecified neutron-gamma radiation field

A prototype small high-pressure parallel-plate tissue-equivalent ionisation chamber with a sensitive volume of 0.63 cm3 is described. The chamber was designed to measure the mean incident neutron energy or the gamma ray absorbed dose fraction of unspecified neutron-gamma radiation fields on the basis of initial recombination theory in the neutron energy range 0.1-10 MeV. Calibration was carried out separately in gamma ray and neutron fields. The angular response of the ionisation chamber was investigated with gamma rays and angular independence demonstrated. The chamber was tested at the National Physical Laboratory at neutron energies of 2.4, 1.6 and 1.05 MeV and determined the mean incident neutron energy to within 5%. Experiments were also performed in Leeds in the mixed neutron-gamma radiation field of an Am-Be source; the gamma ray absorbed dose fraction was provided independently by the microdosimetric method and the mean incident neutron energy in this case was predicted to within 8%. The present method can also be used to provide the gamma ray absorbed dose fraction in the case where the mean incident neutron energy is independently known and this is illustrated for the case of the Am-Be neutron-gamma source where the gamma ray dose fraction was determined to within 12%.

A novel application of the high-pressure ionisation chamber to measure the mean neutron energy or the gamma ray dose fraction in a mixed neutron-gamma radiation field

A novel application of the tissue-equivalent ionisation chamber operated at high pressure of 8 atm (1 atm=101325 Pa) is presented to measure the mean incident neutron energy or gamma ray absorbed dose fraction of an unspecified neutron-gamma radiation field in the neutron energy region 0.1-10 MeV. The method is based on initial recombination in high-pressure ionisation chambers irradiated by neutrons and gamma rays simultaneously. The concept of a 'spectrum-equivalent electron' which was introduced in a previous paper describing recombination of charge carriers produced by gamma rays is generalised here to include recombination of charge carriers in neutron recoil tracks (protons, alpha particles and heavy ions) produced in tissue-equivalent plastic. Empirical relations are then established between the recombination quantities, the mean incident neutron energy and the gamma ray absorbed dose fraction for neutrons in the energy range 0.1-10 MeV. The estimated total uncertainties in the mean neutron energy and gamma ray dose fraction are of the order of 10%.

Dose Independent Use of LiF Detectors in Mixed Neutron-Gamma Radiation Fields

Dose Independent Use of LiF Detectors in Mixed Neutron-Gamma Radiation Fields

Experiences of glow curve analysis of LiF detectors

The glow curves of LiF detectors have at least of seven peaks, e.g. in the 100-400°C temperature range. Unfortunately these peaks are strongly overlapping, however, the readings are made with special care. The glow curve reminds us of a NaJ spectra of poor resolution. The common light integration leads to questionable results, if the ratios of different peaks are not constant. It is the situation for instance, if a LiF detector is exposed in mixed neutron-gamma radiation field, because the peak ratios are different for the two kinds of radiation. This effect can be observed alike in the case of TLD-100, TLD-600 and TLD-700 detectors. Many glow curves of TLD-100, TLD-600 and TLD-700 detectors were investigated at different proportion mixing of neutron and gamma radiations. The possible adaptation of programs used in gamma spectroscopy for glow-peak selection was studied. This report gives a scope of our experiences.

Radiation-induced chromosome aberrations in nuclear-dockyard workers.

The incidence of chromosome aberrations in peripheral blood lymphocytes of 197 dockyard workers has been followed over a 10-yr period. These workers were exposed to mixed neutron-gamma radiation during the refuelling of nuclear reactors, but most exposures were below the internationally accepted maximum permissible level of 5 rem per yr. There was a significant increase in chromosome damage with increasing exposure; aberration frequency was a linear function of dose and was unfluenced by age and time of blood sampling after exposure.

Radiation-released histamine in the rhesus monkey as modified by mast-cell depletion and antihistamine.

4000 rads of mixed gamma neutron radiation administered to rhesus monkeys released a significant amount of histamine into their circulation. When the monkeys were treated with a mast-cell histamine depleter (compound 48/80) for 4 days and then irradiated, no increase in circulating histamine was seen. When 48/80 was give 20 min after irradiation, only a slight increase in histamine was seen, indicating that 4000 rads had released most of the mast-cell histamine.

Radiation-Induced Changes in the Activity of Brain Enzymes Involved in Neurotransmitter Metabolism

Sprague-Dawley adult male rats were exposed to incapacitating doses of mixed gamma-neutron radiation in a single pulse from the AFRRI-TRIGA reactor. The activities of the enzymes choline acetyltransferase (ChAc), acetylcholinesterase (AChE), monoamine oxidase (MAO) and RNA polymerase (RNAp) were determined in the cerebral cortex, cerebellum and hippocampus. It was found that as early as 4 min after irradiation of the animal the activity of MAO was markedly decreased in all 3 brain areas investigated. ChAc and RNAp activities were also decreased but to a lesser extent. No appreciable changes in the activity of AChE were observed.

Electroencephalographic Responses to 2500 Rads of Whole-Body Gamma-Neutron Radiation in the Monkey Macaca mulatta

Monkeys were trained on a behavioral task and instrumented with chronic EEG recording electrodes and systemic arterial catheters for blood pressure measurement. They were then exposed to a 2500-rad pulse of mixed gamma-neutron radiation. Spectral analysis of the cortical electroencephalogram revealed changes in both frequency content and amplitude of the EEG related to periods of behavioral incapacitation. Simultaneous measurements of systemic blood pressure did not show any close relationships with EEG or behavioral changes.

The prevention of radiation-induced, early, transient incapacitation of monkeys by an antihistamine.

ConclusionsThe antihistamine chlorpheniramine maleate is effective in preventing ETI, postirradiation performance decrement, and in reducing the hypotension observed in monkeys after a 4000-rad dose of mixed gamma-neutron radiation. Since the major pharmacological effect of chlorpheniramine is blocking histamine receptor sites, its effectiveness in preventing or modifying the radiation-induced performance changes and hypotension can be taken as further evidence that histamine is involved in acute radiation syndrome. However, the ETI-ameliorating properties of chlorpheniramine are not mediated through the maintenance of arterial blood pressure. An earlier study (9) in which similarity trained and irradiated monkeys were infused with norepinephrine so that blood pressure was maintained above 100 mm Hg did not show significant differences in performance from controls. Some mechanism other than deficient blood pressure, yet capable of being ameliorated by chlorpheniramine, is implicated in ETI.

Gamma-aminobutyric acid metabolism early in the postirradiation response of the rat.

Abstract : The metabolism of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) was studied in rats subjected to 10,000 or 20,000 rads of pulsed mixed gamma-neutron radiation. Whole brain GABA levels were found to rise above control levels by 20 minutes following 10,000 rads and as early as one minute following 20,000 rads. L-glutamic acid decarboxylase activity was also observed to rise as early as one minute following either dose of radiation. The results are consistent with the hypothesis that GABA is involved in the etiology of the transient central nervous system disorders (apathy, disorientation, ataxia) observed in rats shortly after high doses of ionizing radiation.

The Response of Rat Liver Enzymes Involved in Fatty Acid Synthesis to Increasing Doses of Ionizing Radiation in Vivo

The effect of various doses of x-rays and of mixed neutron-gamma radiation on the fatty acid-synthesizing liver enzyme system in rats has been investigated. It was found that the activity of this enzyme system first increased with radiation dose and then decreased in rats exposed to either x-rays or mixed neutron-gamma radiation. Acetyl CoA carboxylase activity was found to be more sensitive to mixed neutron-gamma radiation (decreased) than to x-rays, whereas fatty acid synthetase appeared to be more sensitive to x-rays (increased) than to mixed neutron-gamma radiation.

Canine Intestinal Vasoactivity during the Development of the Gastrointestinal Radiation Syndrome

Abstract : The functional vascular integrity of the small intestine in relationship to its morphological alterations during the post irradiation period was examined Dogs were exposed to 1500 rads (midline tissue dose) of mixed gamma-neutron radiation. Hemodynamic parameters of an in situ intestinal loop were measured in response to the systemic administration of norepinephrine, isoproterenol and gradual bleeding and reinfusion. The results indicate that 48 hours postirradiation when the capillaries are virtually intact and the systemic hemodynamic parameters are not altered yet, the functional integrity of the intestinal vasculature is already significantly deteriorated. The intestinal resistance vessels of the irradiated animals did not exert 'autoregulatory escape' as the controls did. After 72 hours the vasocompensation to the sudden blood pressure changes was also markedly changed. The fluctuation of the intestinal resistance values during the bleeding and reinfusion periods demonstrated neurohumoral imbalance in the postirradiation period. On the basis of these results it is postulated that the terminal cardiovascular collapse in irradiated animals might be due to the development of intestinal ischemic shock.

Erythropoietic stem cell recovery in irradiated polycythemic dogs.

ARTICLESErythropoietic stem cell recovery in irradiated polycythemic dogsSJ Baum, and DE WyantSJ Baum, and DE WyantPublished Online:01 Jan 1972https://doi.org/10.1152/ajplegacy.1972.222.1.92MoreSectionsPDF (801 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByComputersimulationen von ZellerneuerungssystemenBlut Zeitschrift für die Gesamte Blutforschung, Vol. 31, No. 6 More from this issue > Volume 222Issue 1January 1972Pages 92-94 Copyright & PermissionsCopyright © 1972 by American Physiological Societyhttps://doi.org/10.1152/ajplegacy.1972.222.1.92PubMed4258451History Published online 1 January 1972 Published in print 1 January 1972 Metrics

Activity of rat liver enzymes responsible for glycogen metabolism after whole-body irradiation

1. 1. The activities of liver enzymes involved in the breakdown and synthesis of glycogen have been investigated in this study after whole-body exposure of rats to 1200 rads of X-ray of mixed gamma-neutron radiation. 2. 2. It was found that glycogen phosphorylase and amylo-1,6-glucosidase (debranching enzyme), both of which are involved in the breakdown of glycogen to “glucose” units, are inhibited by both qualities of radiation. A considerable inhibition in the activity of amylo-1,4→1,6 transglucosidase (branching enzyme) was also observed. In contrast, it was found that the activity of UDPglucose-glycogen transglucosylase which is responsible for the in vivo synthesis of 1,4-polysaccharides is enhanced whether the animal received X-rays or mixed gamma-neutron radiation. 3. 3. Electron micrographs verifeid the presence of large deposits of glycogen in liver of irradiated rats 48 h after their removal from the exposure room, although no food was given to these animals following irradiation.

Prognostic Significance of Concentrations of Four Classes of Protein-Bound Carbohydrates in the Serum of Dogs

Abstract : Three groups of eight dogs each were given doses of 225, 230, and 400 rads of mixed gamma-neutron radiation, respectively. The doses were delivered at a rate of approximately 20 rads/minute from the AFRRI-TRIGA reactor. In animals with poor prognosis, the serum protein concentrations (milligrams carbohydrate per 100 mg biuret protein) of neutral hexoses, hexosamines, and sialic acid started to rise at varying times postirradiation, continued upward, and remained high until the death of the animal. Moderate to marked fluctuations in the protein concentrations were seen in the time course of all these carbohydrates, especially in the two lower dose groups. The protein concentration of the neutral hexoses gave the clearest warning of unfavorable prognosis in the animals which died and exhibited the greatest stability in those which survived. No significant changes in the concentration of protein- bound fucose were seen in any of the 24 dogs. Serum protein-bound neutral hexose concentrations offer promise for development of a relatively simple, objective prognostic test to supplement clinical observation in cases of radiation injury. Thus, numerical ranges of protein concentrations of neutral hexoses are proposed to indicate good, guarded, and poor prognoses for this species. These tentative ranges were tested in nine additional dogs and were found to be effective for prediction.

Effectiveness of Tranquilizing Drugs in Rats Exposed to Mixed Gamma-Neutron Radiations

Chlorpromazine, triflupromazine, and chlordiazepoxide were studied for their effect on a conditioned avoidance response in rats at selected times following 500-, 1000-, and 10 000-rad whole-body doses of mixed gamma-neutron radiations. The ED50 of the drugs increased in the rats receiving 1000 rads and decreased in those receiving 10 000 rads when compared to unirradiated controls. Although the dose-respone curve may be altered in irradiated rats, the three drugs studied remained effective even after radiation doses associated with central nervous system damage.

Alteration of postirradiation hypotension and incapacitation in the monkey by administration of vasopressor drugs.

Abstract : The effect of vasopressor drugs on the early hypotension and incapacitation observed in monkeys following a 4-krad pulsed dose of mixed gamma-neutron radiation was investigated. Seven monkeys received only the 4- krad dose of radiation and served as controls. Norepinephrine or angiotensin was administered to five other monkeys by intravenous infusion from 5 minutes prior to irradiation until death, except that infusion was temporarily interrupted several times after irradiation of the animals. Blood pressure was continuously monitored in all animals. Drug-induced blood pressure elevation prior to irradiation did not prevent the characteristic early postirradiation fall in mean blood pressure, but severity of the resulting hypotension was reduced. Cessation of drug infusion after irradiation resulted in a rapid drop in blood pressure with the animal becoming incapacitated (loss of consciousness) when mean blood pressure fell below a critical level of about 50 mm Hg. After drug infusion was resumed, consciousness returned as the blood pressure rose above the critical level. This sequence was repeated several times before the animal failed to respond to drug administration and died abruptly in a hypotensive state. Five other monkeys were given a single intravenous injection of ephedrine or amphetamine 1 hour before irradiation; these animals received no further treatment. Ephedrine administration appeared to be as effective at maintaining satisfactory postirradiation blood pressure as norepinephrine and angiotensin.

Effectiveness of Pressor Drugs in Beagles Exposed to Mixed Gamma-Neutron Radiations

SummaryAortic pressure, right atrial pressure, heart rate, and cardiac output were measured; and mean pressure, stroke volume, and peripheral resistance were calculated in 27 male beagles before and after 5000- or 10,000-rad whole body doses of mixed gamma-neutron radiations. The response of these beagles to levarterenol, phenylephrine, or metaraminol was also determined before and after irradiation. Irradiation caused a decrease in aortic pressure, cardiac output, and stroke volume; and an increase in heart rate. Peripheral resistance increased, but not significantly, in irradiated beagles. Phenylephrine and metaraminol were equally effective before and after the dogs were irradiated, while levarterenol was more effective in irradiated dogs. The results are interpreted as follows: (i) radiation induced hypotension cannot be fully explained by radiation effects on peripheral blood vessels; (ii) pressor drugs are effective in irradiated beagles with hypotension, and drug effectiveness is probably decreased...

Miniature Pig Performance after Fractionated Supralethal Doses of Ionizing Radiation

Miniature pigs, trained to traverse, on cue, a two-chambered shuttlebox, received fractionated and unfractionated doses of pulsed mixed gamma-neutron radiation. Performance was significantly better when 6,800- to 13,000-rad doses were delivered in two equal fractions, 5 hours apart, than when given in a single pulse; the early transitory incapacitation period was shorter and the pigs recovered more rapidly to an acceptable performance level. Performance was also significantly better after an 8800-rad fractionated dose given as two 4400-rad fractions from 1/2 to 51 hours apart than after an 8600-rad unfractionated dose. Furthermore, the pigs generally had less severe clinical symptoms (convulsions and coma) after the second half than after the first half of the fractionated doses. When the first dose was reduced to 3400 or to 1700 rads, however, early transient incapacitation did occur after the subsequent 4800- to 5000-rad dose and was more frequently accompanied by convulsions when the initial dose was o...

Hematopoietic Recovery in Irradiated Dogs

Hematological recovery in dogs exposed once or repeatedly to either 150 rads of x-rays or 150 rads of mixed gamma-neutron radiation was measured. Comparisons were made among animals exposed to each...