Long-term Effects Of Radiation Research Articles

The Long-Term Effects of Radiation on Complementary MOS Logic Networks

The Long-Term Effects of Radiation on Complementary MOS Logic Networks

77. Long-term radiation effects on graphite

77. Long-term radiation effects on graphite

The Effects of X-Rays on the Regrowth of Hair in the Mouse and Their Modification by Cysteamine

The mouse hair follicle was used as a biological model for studying relatively long-term radiation effects and for evaluating radioprotective agents. The flank hair was plucked 3 days before irradiation, and four areas were given exposures of varying magnitude (500 to 5000 R). It was found that the delay in regrowth and the permanent damage (at 100 days postirradiation and later) increased with increasing exposure. The effect of cysteamine in protecting the hair follicle was to diminish the delay of regrowth and the degree of permanent epilation, though the general character of the response was unchanged. The dose-reduction factor appeared to diminish with increasing dose of radiation. A tentative explanation for this finding, based on the hypothesis of there being some hypoxic cells present, is suggested. The advantages of this type of nondestructive radiobiological model are discussed.

Laser radiation. II. Long-term effects of laser radiation on certain intracranial structures.

Laser radiation. II. Long-term effects of laser radiation on certain intracranial structures.

Frequency of Live Births among Survivors of Hiroshima and Nagasaki Atomic Bombings

The purpose of this report is to present the results of an analysis of the distribution of live births among atomic bomb survivors in Nagasaki and Hiroshima. It represents a segment of an effort to assess the long-term effects of the radiation on fertility. The importance of research on the fertility of the survivors has been recognized since the earliest investigations in those cities. The Joint Commission for the Investigation of the Atomic Bomb in Japan reported on the period just subsequent to the bomb (1). A diminution in sperm counts correlating with distance from the hypocenter was noted. Histological changes, particularly in the germinal epithelium of the testes, were seen in fatal cases within the first few weeks after the bomb. Abnormal terminations, mostly inviable, were relatively frequent in a sample of pregnancies in Nagasaki observed during the three months after the bomb. Neel and Schull' studied pregnancy terminations in the two cities between 1948 and 1953. Whereas small alterations in the sex ratio were noted, no well-defined relationships were observed in their malformation or stillbirth data. The above studies were not directly concerned with the long-term effect of radiation on fertility. The former was a study of the immediate postbomb months, and the interest of the latter was in genetic effects. Most of the links in the chain of events leading to the production of viable births cannot conveniently be analyzed. Some are unknown to the subject, such as quality and number of gametes. Others are highly personal and not readily reported, such as frequency of intercourse, use of contraceptives, and the practice of abortions. Affecting this chain, moreover, are covariables that may be partially confounded with radiation. These include education, age, and income, for example.

Frequency of Live Births among Survivors of Hiroshima and Nagasaki Atomic Bombings

The purpose of this report is to present the results of an analysis of the distribution of live births among atomic bomb survivors in Nagasaki and Hiroshima. It represents a segment of an effort to assess the long-term effects of the radiation on fertility. The importance of research on the fertility of the survivors has been recognized since the earliest investigations in those cities. The Joint Commission for the Investigation of the Atomic Bomb in Japan reported on the period just subsequent to the bomb (1). A diminution in sperm counts correlating with distance from the hypocenter was noted. Histological changes, particularly in the germinal epithelium of the testes, were seen in fatal cases within the first few weeks after the bomb. Abnormal terminations, mostly inviable, were relatively frequent in a sample of pregnancies in Nagasaki observed during the three months after the bomb. Neel and Schull' studied pregnancy terminations in the two cities between 1948 and 1953. Whereas small alterations in the sex ratio were noted, no well-defined relationships were observed in their malformation or stillbirth data. The above studies were not directly concerned with the long-term effect of radiation on fertility. The former was a study of the immediate postbomb months, and the interest of the latter was in genetic effects. Most of the links in the chain of events leading to the production of viable births cannot conveniently be analyzed. Some are unknown to the subject, such as quality and number of gametes. Others are highly personal and not readily reported, such as frequency of intercourse, use of contraceptives, and the practice of abortions. Affecting this chain, moreover, are covariables that may be partially confounded with radiation. These include education, age, and income, for example.

Serum Lactic Dehydrogenase Levels in Adult Beagle Dogs with Internally Deposited Radionuclides

Innumerable reports have been made concerning the correlation, or lack of it, between lactic dehydrogenase (LDH) activity in serum, plasma, or tissue homogenates, and the presence of neoplastic disease. Interpretation of results has been complicated by the use of myriad methods of assay, and testing of many different species. Thus, comparisons between LDH catalyzing pyruvate to lactate (1-4), and LDH catalyzing the reverse reaction (5), the many modifications of these procedures, and the differences in the various isozymes (6-8) of LDH must all be considered. Moreover, not only are the normal values for these procedures not comparable, they differ according to species tested for both average values and those found during disease states. In our laboratory, as well as in others, studies on the long-term effects of internally deposited radionuclides are being pursued in a large colony of beagle dogs (9). Since a very important long-term effect of radiation is the formation of tumors, especially osteogenic sarcomas in this colony, a method of detecting the early presence of neoplastic tissue is desirable. Moreover, irradiation itself could be the cause of metabolic alterations reflected in measurable enzymatic abnormalities. It was our purpose, in this study, to establish a norm for LDH in dog serum, and to determine whether LDH level is a good indicator of the presence, growth, and extent of neoplasia, or length and level of exposure to radiation.

The effects of X-rays on quantitative characters

1. The rate of production by X-rays of new genetic variation in two quantitative characters inDrosophila melanogaster(sternital and sternopleural bristles) has been investigated, using ‘plateaued’ populations which had reached the limit under artificial selection and, for sternital bristles only, populations which had been made genetically invariant by inbreeding. The genetic variation was always measured by the response of the population to selection. The X-rays dose given in any generation was always 1800 r. to adults.2. Seven plateaued lines had eight cycles of alternate irradiation and selection, each with its non-irradiated control. All the responses were small but in three lines they were significantly greater after irradiation.3. Selection was applied to three different inbred lines, genetically marked to detect contamination, after varying periods of irradiation. At the same time, the inbred lines and lines derived from them which had been mass mated in bottles were selected. The irradiated populations showed a greater response. The new genetic variance produced by the irradiation was approximately 10−5units/r. The estimate of the dose required to introduce new variation equal to that in a standard outbred population was 500,000 r.4. The effective population size was an important factor in the interpretation of some of these results on the long-term effects of radiation. By observing the variation between replicate lines in the frequency of a gene with a visible effect under these culture conditions (i.e. in a single culture bottle) the effective population size was estimated at sixty. Outbred populations kept under these conditions for many generations showed a reduction of genetic variability in agreement with this value.5. To investigate the possibility that the deleterious genes produced by irradiation would interfere with the response to artificial selection, a standard outbred population was irradiated and selected. In spite of the observed high frequency of recessive lethals produced, the response to selection was very similar to that of the standard population.

I. The Age Factor in Radiation Sensitivity in Mice

The effect of age on the sensitivity of man to ionizing radiations has for many years been recognised by radiotherapists who, on a somewhat empirical basis, have planned their treatment to take this factor into account. In animal work the importance of age as a factor influencing radiation sensitivity had virtually been neglected until a few years ago. One still finds papers describing work with animals, in which the age changes are relevant to the radiation effect studied, and yet the age of the animal is not even mentioned. Such neglect can lead to misleading interpretations, particularly when the effect studied is not large. There are two difficulties in attempting to take the age factor into account in the experimental design: (a) our knowledge of the normal variation with age of form, function and composition is inadequate; (b) the obtaining of large numbers of animals of a specified age is costly and time consuming. However, in proportion to the cost of most biological experiments, this additional budgeting would be well worthwhile. In this paper we shall discuss the variation with age of the sensitivity both for acute and long-term effects of radiation. Several workers (Quastler, 1945; Zirkle, 1946; Abrams, 1951; Hursh and Casarett, 1956; Sacher, 1957) have studied the age variation over portions of the life-span using such criteria as mean survival time, dose accumulated to death and the LD50 for deaths within a specified period.

THE EFFECT OF IRRADIATION ON THE MAMMALIAN FETUS

The experimental use of radiation in pregnant mammals and the exposure of hunnan fetuses to radiation have demonstrated the approximate dose that results in growth retarda tion, death, and malformation of the fetus. The long- term results of irradiation, namely, genetic. tumorigenic, and life-shortening effects, have to be evaluated specifically for the fetus because of the possibility of altered fetal radiosensitivity to these long-term radiation effects. Suggestions are presented for reducing certain more remedial radiation hazards and placing others in their proper prospective. The importance of background radiation, fall-out radiation, and medical irradiation are presented. The quantitative importance of these sources of irradiation with the possible radiation effects to the fetus are discussed. 93 references. (auth)

Late Effects of Fast Neutrons versus X-Rays in Mice: Nephrosclerosis, Tumors, Longevity

Groups of mice exposed to sublethal doses of fast neutrons or to lethal doses of x-rays were followed until natural death in order to study long-term irradiation effects. The x-irradiated mice were protected against acute death by injection of hematopoietic cells or limb shielding. Gastrointestinal carcinomas were much more common in the neutron-irradiated than in the x-irradiated mice. However, in the small group of mice surviving superalethal doses of x rays of 1000 to 1100 r following thigh shielding during exposure, 21% exhibited intestinal carcinomas. A neutron RBE value of 2 to 3 is therefore indicated for these tumors, as late effects. Nephrosclerosis, on the other hand, was more common in the x-irradiated mice, with an apparent neutron RBE value close to unity for this late lesion. (auth)

Variation of sensitivity to ionizing radiation with age.

THE relation between the long-term effects of radiation and ageing has been the subject of much investigation in recent years, but little quantitative work has been done on the variation with age of the effects produced by a given dose of radiation. Using a single dose, Abrams1 found a maximum mortality-rate in mice 4 weeks old. Hursh and Casarett2 measured the LD50 in rats of different ages, and found a decrease with age in the latter period of life ; somewhat similar results were obtained by Sacher3 for mice. We are carrying out a systematic study4 of the long-term effects of radiation in mice, with particular reference to the dependence of these effects on age. As part of this work, we have investigated the variation of sensitivity with age, using as a criterion of radiation damage the LD50 at 30 days.

Natural Aging and the Effects of Radiation

Neither studies of occupational exposure nor military experiments, deliberate and accidental, have yet yielded satisfactory evidence on the long- term effects of radiation on individual human aging or on the life span of human populations. Natural aging is defined as a proressive decline in vigor with increasing age, which is probably universal in warm-blooded vertebrates. The mechanisms which bring about mammalian aging are wholly unknown, and it can be discussed only in the most general descriptive terms. It is not known whether the loss of vigor occurs at a cellular or a tissue level, whether there is a timekeeping process common to all manmmals, or whether aging is an assemhly of processes whose only commoa propenty is that they increase vulnerability. Results of studies on rats give some evidence that aging may be dissociable from general metabolism. Results are reviewed from a number of studies on animal survival in which factors other than radiation are considered. Data are summarized from a number of studies on the long-term effects of irradiation on life span. Survival curves of control and irradiated animals are compared. All the experimental studies indicate that ionizing radiations, at least above a certain threshold of exposure, shorten life.more » It is pointed out that the observations are difficult to compare because of their heterogeneity in type, relative efficiency, variation in methods of radiation dosimetry, choice of animals and strain, methods of analysis, and methods of expressing results. It is also pointed out that mathematical consideration of possible mechanisms in radiation injury has so far outstripped experiment. It is concluded that radiation biology can offer fundsmental information about natural aging processes. The author states that sufficient time has now been devoted to experiments in which radiations have been administered to animals and shown to do them no good. This point having been established, it should be possible to fix the requirements for more instructive compsrisons. Some areas for future research are suggested. 66 references. (C.H.)« less

Effect of sweating and changes in blood flow on heating of human skin.

Summary and Conclusions1. Acetylcho-line-induced sweating decreases and atropine-induced inhibition of sweating increases heating effects of radiated heat energy. Increased blood content of tissues has a slight effect and increased blood flow a more pronounced effect on lowering the heating effect. 2. The effects of sweating appear to be due partly to vaporization of water at the skin surface and partly to a change in the thermal characteristics of the skin itself. 3. Increased blood flow through the skin raises the temperature and therewith increases the heating effects of low-energy, short-time radiation. However, the thermal characteristics of the skin are changed in a way to combat these heating effects. Therefore, the harmful effects of high energy and long term radiation are decreased. 4. Pain threshold is frequently measured as temperature elevation or as reaction time, and then it is markedly affected by changes in blood flow and rate of sweating. However, if it is studied in terms of tissue tempe...