Cobalt-60 Gamma Radiation Research Articles

Survival of Hibernating Ground Squirrels (Citellus tridecemlineatus) after Single and Fractionated Doses of Cobalt-60 Gamma Radiation

The effects of hibernation on survival after irradiation was studied in thirteen-lined ground squirrels (Citellus tridecemlineatus). The ${\rm LD}_{50(90)}$ for a single dose of60 Co gamma radiation was 1024 rads for ground squirrels irradiated and maintained at 23°C, whereas the ${\rm LD}_{50(90)}$ was 1127 rads for ground squirrels irradiated during hibernation and subsequently maintained in the cold room at 5°C for 3 weeks before they were returned to 23°C. Survival was higher in ground squirrels aroused from hibernation 1 day after an exposure to 1160 rads (79%) than in ground squirrels aroused from hibernation 2 weeks after exposure to 1160 rads (37%). The squirrels that were given 1160 rads at 23°C and maintained at 23°C had 9% survival. When ground squirrels were given two doses of 668 rads, 6 hours apart, survival was greatest (73%) in the hibernating group that was kept in the cold room 3 days before, during the interval between, and for 20 hours after the second dose of gamma rays. The next high...

A preliminary study of injury and recovery of the male germinal epithelium and spermatogenesis in Macaca mulatta following whole body cobalt-60 gamma irradiation.

A preliminary study of injury and recovery of the male germinal epithelium and spermatogenesis in Macaca mulatta following whole body cobalt-60 gamma irradiation.

Determining the Repair Rate for Radiation-Induced Chromatid Deletions during the First 24 Hours after Irradiation

The number of chromatid plus isochromatid deletions present in the testes and bone marrow of the Chinese hamster was measured as a function of time following acute exposure to cobalt-60 gamma irradiation. The number of breaks remaining scorable at any time after irradiation exposure could be represented by a simple exponential equation (N = Noe-kt). The values of No and k, calculated after 100 roentgens of cobalt-60 gamma irradiation, were 1.15 breaks/cell and 0.16/hour, respectively, for the testes, and 0.53 break/cell and 0.14/hour, respectively, for the bone marrow. The average length of time that the breaks remain scorable, 1/k, was found to be 6.3 hours for the testes and 7.1 hours for the bone marrow. By suitable formulation, it was possible to predict the number of breaks present by using varied radiation exposure rates and times after exposure. This formulation could be used for both single and multiple radiation exposures.

The Response of the Beagle Dog to Cobalt-60 Gamma Radiation: Determination of the LD 50(30) and Description of Associated Changes

The ${\rm LD}_{50(30)}$ of ${}^{60}{\rm Co} \gamma \text{-radiation}$, given as a single, bilateral exposure at a rate of approximately 15 R/min to the whole body of 13-month-old, purebred beagle dogs, was determined to be 258 rads, expressed as the average absorbed dose. The method for computing radiation dose allows compensation for the individual variations in size of dogs. This has a significant effect on the overall result. Detailed examination of the dogs-by clinical methods, hematology, blood biochemistry, and gross and microscopic inspection of tissues-led to the conclusion that acute bacteremia, secondary to bone marrow damage was the primary cause of death. There were no sex-related differences. Bacteremia intervenes in the progression of the radiation syndrome as the granulocyte count approaches the critical level of about $1000 \text{cells}/{\rm mm}^{3}$ of blood. Thus the complete expression of biologic response versus radiation dose is masked by the invasion of bacteria. The effect of such...

Inactivation of Amino Acid Transport Systems in Ehrlich Ascites Carcinoma Cells by Cobalt-60 Gamma Radiation

Suspensions of Ehrlich ascites cells were subjected to doses up to 8.27 × 105 rads of γ-radiation from a60 Co source. Initial rates of uptake of α-aminoisobutyric acid (AIB) and L-serine by the A r...

Effect of Cobalt-60 Gamma Irradiation on Blood Pressure and Cerebral Blood Flow in the Macaca mulatta

Sixteen Macaca mulatta monkeys were exposed to a single 2500-R dose of cobalt-60 gamma irradiation at a dose rate of 500 R/min. Immediately following irradiation there was precipitous decline in cerebral blood flow. The initial decline was followed by a period of partial recovery within 20 to 30 minutes, with a subsequent slower secondary decrease in cerebral blood flow thereafter. Alterations in cerebral blood flow were accompanied by parallel changes in systemic blood pressure. Following irradiation there was a phase of immediate hypotension followed by transient partial recovery at 20 to 30 minutes. Contributing to the observed decrease in cerebral blood flow following irradiation was an apparent impairment of the normal regulatory function of the cerebral vasculature in maintaining adequate blood flow. The cerebral blood flow decline was of a degree that might be expected to produce impairment of normal CNS function. It occurred at a time during which behavioral incapacitation has been observed follow...

Radiation-enhanced surface activity of an organic explosive, γ-HMX

The surface activity of one-micron particle size γ-octahydro-1,3,5,7-tetranitro-1,3,5,7, tetraazocine (γ-HMX) was studied as a function of cobalt-60 gamma-irradiation in vacuo and in vapors of H 2O, NO and NO 2. Changes in surface activity were measured by a radiometric determination of adsorption of carbon-14 labelled stearyl trimethyl ammonium bromide (STAB) from solution. Observed enhancement of surface activity is attributed to a one-Mrad irradiation-induced adsorbate-substrate interaction which produces polar surface adducts. The mechanism of energy transfer from the bulk of the substrate to the surface-vapor phase interface suggested for various other substrates is postulated to apply to crystalline organic solids such as γ-HMX.

A Prediction and Selection System for Radiation Effects in Planar Transistors

Radiation tests on a wide range of planar silicon bipolar transistors under high-energy radiation indicate that the degradation of gain due to the ionizing component of radiation is due to a namely, an increase in the surface recombination velocity near the emitter-base junction. This effect is dominant in many real-life operating environments encountered by space electronic systems, and can produce quite serious losses of gain. The authors have devised a practical prediction technique for the surface effect and applied it to a wide range of space-approved bipolar transistor devices. Specifications of the expected levels of surface damage, devised from such data, have only rarely been exceeded in subsequent sampling tests. The prediction technique requires data from a Cobalt-60 gamma-ray test of 10 to 20 samples of each device type. Progress in using this prediction technique is reported. During testing of many devices under Cobalt-60 gamma radiation, infrequent cases have been noted where the surface damage levels exceed those predicted. Some devices are anomalously sensitive, with damage levels falling well outside the normal statistical distribution of sensitivity. It is thus important to discover a method of detecting these rare, but excessively sensitive units. The authors describe a detection or method for such anomalously sensitive devices. The conclusion of the investigation is that the irradiate-anneal form of component preselection cycle can produce, from a commercial batch of planar transistors, a set of devices possessing a uniform, minimized sensitivity to ionizing radiation.

Comparison of Radiation-Induced Chromatid Aberrations in the Testes and Bone Marrow of the Chinese Hamster

Cells from the testes and bone marrow of the Chinese hamster were sampled at 6 hours after the end of exposure to cobalt-60 gamma irradiation, and the number of chromatid-type aberrations was score...

Injury Accumulation and Recovery in Sheep Exposed to Protracted Cobalt-60 Gamma Radiation

Abstract : A modified split-dose technique was used to measure the accumulation of injury during protracted exposures of the domestic sheep to Cobalt-60 gamma radiation. An initial or conditioning exposure of 165 R was given at 0.5, 0.95, 1.85, and 3.94 R/hr, and the acute exposure LD50/60 was determined immediately thereafter. These studies indicate that there is a dose rate threshold for injury accumulation under these conditions or protracted irradiation and that the threshold lies between 1.0 and 1.5 R/hr. Recovery from injury accumulated during protracted exposures has been studied by determining the LD50/60 at various times after protracted exposures. These studies indicate a rapid recovery without a lag period that proceeds to a transient acquired radioresistance 15 days after the conclusion of the protracted irradiation. (Author)

Growth in the Chicken after High-Rate and Low-Rate Cobalt-60 Gamma Irradiation

Injury from exposure to ionizing radiation is reflected in subsequent growth. However, few attempts to quantitate the relative influence of dose and period of exposure on gross weight have been made. Studies on the chick show that, for acute mortality, the effectiveness of a single radiation dose decreases with increase in exposure time (1, 2). In these investigations, the exposure period was varied from a few minutes to 24 hours, and the amount of lethality occurring within 30 days served as the measure of radiation injury. It was found that half of the irradiated chicks died within 30 days when subjected to a single dose of approximately 920 R of Co60 y-rays delivered in 3 to 30 minutes, whereas with doses protracted over 24 hours 1620 R was required to achieve the same mortality. The survivors of an acute irradiation have sustained some injury which can be assessed with other measures of damage. We address ourselves to the question: When newly hatched chicks are irradiated, is loss in dose effectiveness with protraction measurably reflected in postirradiation growth? This report describes the accretion in weight of chicks that survive at least 30 days after a single acutely lethal exposure to Co60 y-rays. Exposure was either completed in a few minutes or extended uniformly over 24 hours. Differences between the weight-age patterns under these two exposure conditions are observed and are used to deduce a measure of the change in dose effectiveness. The statistical approach is based on the assumption that the weight-age dependence is the resultant of two deterministic processes, one characterized by a Gompertz function (3) and the other by a linear function. In 1926, Wright (4) pointed out that the growth of individual organisms could be represented by a Gompertz function. If growth is uninhibited, an exponential increase in weight with age is expected; that is, the rate of increase in weight is a constant proportion of the weight attained. Usually the magnitude of this proportion is not constant, but decreases with age at an approximately uniform percentage rate. This conceptual structure

The Relative Biological Effectiveness of 138-Mev Protons as Compared to Cobalt-60 Gamma Radiation

The Harvard Synchrocyclotron Facility was the source of protons. A diagram of the experimental arrangement used for the irradiations with the cyclotron is shown in Fig. 1. Exposures were made in the primary proton beam which was defocused by a lead scatterer of 7.6 gm/cm2 placed at the exit of the cyclotron drift pipe. During exposure the mice were held in individual aluminum-screen cylindrical cages 3.8 cm in diameter by 10.2 cm long, stacked on 3.93-cm centers and oriented as shown in the diagram. The irradiations were performed with 4 mice at a time at a distance of 161 cm from the scatterer, with 6 mice at a time at 228 cm, and with

Studies on the eradication of Anopheles pharoensis Theobald by the sterile-male technique using cobalt-60. I. Biological effects of gamma radiation on the different developmental stages.

Pupae of Anopheles pharoensis Theobald were subjected to Cobalt-60 gamma radiation from 500R to 7000R with 500R increments, to study the biological effects of gamma rays on fitness components. The results indicate clearly that lifetime egg production increased significantly at lower doses (1000R) with no significant effects at doses between 1500 and 2000R, after which a highly significant decline was observed. Percentage of hatchability was greatly affected at all doses, falling below 1% at 5000R, above which it remained constant. Percentages of pupation and emergence, sex ratio, and longevity of adults were not affected by irradiation; irradiated adults live longer than controls, though not significantly so.

On the mechanism of inactivation of antibody activity by cobalt-60 gamma radiation—I

On the mechanism of inactivation of antibody activity by cobalt-60 gamma radiation—I

On the mechanism of inactivation of antibody activity by cobalt-60 gamma radiation—I

On the mechanism of inactivation of antibody activity by cobalt-60 gamma radiation—I

A multipurpose cobalt-60 gamma irradiation facility

A multipurpose Co 60 γ-irradiation facility has been developed and used at the Puerto Rico Nuclear Center that has applications in biological, chemical and solid-state physics research. The facility uses water as a shield so that direct visual observations of the source and mechanisms involved in irradiation procedures can be made. The source can be arranged in several geometries providing a dose-rate range of 3500–1,500,000 r/hr and providing a field up to 18 in. in diameter. Temperature control as well as control of the gaseous environment of the sample during irradiation is possible with different sample holders. Materials which have been irradiated include: seeds, bacterial cultures, small animals, maize tassels, bananas, chick embryos, insects, organic crystals, chemical solutions and vegetative cuttings of plants.

Effect of whole brain cobalt-60 gamma irradiation on cortical arousal in the burro

The acute effects of single, whole brain, cobalt-60 gamma irradiation on the cortical arousal to the conditioned stimulus were examined on normal male adult burros up to 7 days following 200 r, 400 r and 600 r. 1. 1. A 200 r irradiation did affect, neither the resting patterns of electrocorticograms, nor the CS-induced cortical arousal. 2. 2. Degradation and rapid loss of the CS-induced cortical arousal were observed only if the subjects were irradiated with 400 r or 600 r. 3. 3. Since the 600 r exposed subjects suffered from significant physiological changes and died early of radiogenic neuropathic death, a facilitated extinction of the cortical arousal observed in this group might merely reflect effects of radiation sickness. 4. 4. Collateral data indicated that facilitation of extinction of the CS-induced cortical arousal would not be caused by radiogenic changes in the US efficacy and in attention, but by difficulties in getting emotion activation in response to learned cues.

CLINICALLY USEFUL CALCULATIONS TOF THE DOSE DISTRIBUTION FROM MULTIPLE RADIATION SOURCES.

Carcinoma of the cervix is commonly treated by a combination of intracavitary radium and external high-energy x-ray or cobalt-60 gamma radiation. Standard values of dose are essentially preselected, i.e., 6,000 R to Point A in two seventy-two-hour radium applications two weeks apart and 3,000 R by external radiation. More description, however, is not only needed, but is essential to the understanding of what an “ideal” radium application should be and what the actual application will achieve. The radium application is designed to achieve a bell-shaped zone of irradiation by the loadings selected for the tandem and ovoids. Certain values in the determination of dose are predetermined. The total dose to be given by intracavitary radium is known, and the tolerance values for bladder and rectum can be established within limits. Almost any loading in any configuration will produce the standard dose in the three-day application. There is some difficulty in determining where this bell-shaped zone of radiation lies in relation to the anatomy. The real problem is dose distribution. Where should the standard dose be delivered and is it in fact delivered where the clinician intends ? What variation in distribution can be accepted as satisfactory? Such questions have been answered in part. The whole development of dosimetry for intracavitary radium has been toward providing more information about the distribution of zones of radiation. The Manchester System relied on predetermined loadings used with various sizes and combinations of tandems and ovoids to give an ideal dose distribution. The loadings were designed to deliver a pre-calculated dose of 1,000 R per day at a point designated as Point A. Generally, right and left Points A lie 2 cm above the level of the cervical os and 2 cm lateral from the midline. Point B is 3 cm lateral to Point A. Symmetrical applications are not always achieved, however, and in actuality the critical spacing and interrelation of the sources necessary for an ideal application are not always possible. If the symmetrical application is not achieved, the problem in dosimetry is still the determination of where the 1,000 R per day zone actually is in relation to the individual anatomy. Several points including Point A are commonly selected, and calculations are made to determine the dose rate at these points of interest. The calculation requires that the distance be determined from each source to each point for which dose information is desired. This is measured on radiographs in two projections with a correction for distortion due to magnification and requires the careful application of geometry in 3 planes. Once the distance from each source to the point of interest is known, the contribution of each source is determined by the inverse-square law. The determination of dose at even a few points is tedious and time-consuming, and the time required for many calculations soon becomes more valuable than the information obtained.

Radiation protection by an auxin analogue, beta-2,4,5-trichlorophenoxyethanol, in C57BL-6J mice exposed to cobalt-60 gamma radiation.

OUR previous studies1,2 have demonstrated that certain analogues of plant growth regulators kill free cells of the Ehrlich ascites carcinoma, both in vitro and in vivo. The specificity of the chemical structure of the auxin analogues for this cytocidal action suggests the possibility that the neoplastic transformation of an initially normal mammalian cell consists of its reversion to the primitive type of growth-control that is characteristic of a plant tumour cell. If this is indeed the case, it might be possible for auxin analogues to influence the rate and/or magnitude of responses of animals to ionizing radiation. Accordingly, we designed experiments to test the ability of such compounds to delay or prevent the death of mice subjected to normally lethal doses of γ-radiation from a cobalt-60 source. These experiments have shown that a 150-mg/kg dose of β-2,4,5-trichlorophenoxyethanol (2,4,5-TOH), an analogue of the selective herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), administered shortly before irradiation, affords a high degree of protection to C57BL/6J mice.

Effect of cobalt-60 gamma radiation on the determination of uranium(IV) in phosphoric acid solutions of uranium(iv) oxide

The effect of 60Co γ-radiation on aerated and deaerated phosphoric acid solutions of uranium(IV) oxide (UO 2) was studied as a function of temperature, concentration of UO 2, and radiation dose rate. The effect was measured in terms of the radiolytic yield of uranium(VI),Gu VI. For solutions of high initial UO 2 concentration, Gu(VI) is largest for the aerated solutions at 25°; it is lowest for the deaerated solutions at 140°. The Gu(VI) is lower for the solution of low initial UO 2 concentration than for any of the solutions of high initial UO 2 concentration. At the high starting UO 2 concentration, the initial Gu(VI) values are always higher than the succeeding values; this effect is attributed to the depletion of oxygen originally present in the solution. Gamma radiation causes an error in the determination of the stoichiometry of UO 2; the error is a function of the radiation dose. This error can be minimized by excluding oxygen from solutions of UO 2 and by keeping the initial UO 2 concentration as low as possible.