Long-term Effects Of Radiation Research Articles

History, current status, and trends of radiation protection standards.

Quantitative standards for protection against exposure to ionizing radiation were first formulated in the 1930s. Since that time, standards have been restated periodically in different radiation units and conceptual frameworks that reflect improved understanding of the biological effects of radiation interactions and their consequences for human health. In the 1970s the expression of protection standards shifted from a dose- to a risk-based approach, with dose limits established to yield risks to radiation workers comparable with those for workers in other "safe" industries. Over the years, radiation protection standards have exhibited a downward trend to more rigorous limits that require increased commitments of personnel and resources for their enforcement. There are several reasons for this trend, including increased recognition of the long-term health effects of radiation, improved protection measures that permit radiation use at lower levels of exposure, growing numbers of persons exposed occupationally to radiation, and probably a greater intolerance to involuntary risks in society, with radiation targeted as a highly visible source of involuntary risks in the form of nuclear power plants and radioactive waste sites. In the past few years, reports of the Radiation Effects Research Foundation, United Nations Scientific Committee on the Effects of Atomic Radiation, and the National Research Council of the U.S. National Academy of Sciences have presented increased risk estimates for radiation exposure as a consequence of ongoing epidemiological analyses of human populations exposed to ionizing radiation. These risk estimates have enhanced public concern about radiation exposure and set the stage for discussions about the desirability of further reductions in exposure standards for radiation workers and members of the public. Such reductions would directly affect the professional activities, educational responsibilities, and administrative burdens of most medical and health physicists. These persons should understand the process of deriving risk estimates from epidemiological data, the factors that influence the risk estimates, how risk estimates are integrated into radiation protection standards, and the possible impact of more rigorous standards on the use of radiation in medicine.

Effects of Total-Body Irradiation on Bone Marrow Erythroid Burst-Forming Units (BFU-E) and Hemopoietic Regeneration in Dogs

The acute and long-term effects of total-body X irradiation (TBI) on early erythroid progenitors, burst-forming units (BFU-E), in the bone marrow of beagles were studied for midline tissue doses of 1.6 and 2.4 Gy. After both radiation doses the initial reduction in the concentration of BFU-E was greater than that found for the granulocyte-macrophage progenitor cells (GM-CFC) and thus was in general agreement with the higher in vitro radiosensitivity of BFU-E compared to GM-CFC. After TBI with 1.6 Gy the GM-CFC and BFU-E returned to their normal levels within 2-4 weeks without showing long-term radiation effects. In contrast, after TBI with 2.4 Gy the concentrations of GM-CFC and BFU-E remained below the pretreatment levels up to 1 year after exposure. For a given midline tissue dose, the extent of the long-term effect of radiation on the BFU-E in a certain bone marrow site seems to be dependent on the local radiation dose in the respective bone marrow space. The minor radiation effects observed in the erythrocyte concentration in the peripheral blood, the hematocrit, and the hemoglobin concentration point to the enormous compensatory capacity of the more mature erythropoietic transit population to increase the proliferative capacity upon demand.

Issues in Contemporary Drug Delivery

Objective To provide an overview of the selection criteria for and proper use of sunscreen products. The effects of ultraviolet (UV) radiation on the skin are also discussed. Data Sources References were selected from published bibliographies of books and articles dealing with UV radiation and sunscreen agents, manufacturers’ product information, and topical searches in MEDLINE computerized database (English language, through 1991). Study Selection Studies that investigated the short- and long-term effects of UV radiation (UVA and UVB) on human skin were reviewed. Equal weight was given to information published in authoritative textbooks by prominent photobiologists and dermatologists. Data relating to human skin were selected in preference to animal data, and data involving ingredients approved for use in the US were used in preference to those of products approved in foreign countries. Data Synthesis The literature describing the effects of both UVA and UVB on human skin is substantial. However, there is considerably less information on UVA in terms of how its effects impact the formulation and use of commercially produced sunscreen products. Information regarding the proper use of currently available sunscreen products and the appropriate patient counseling information for pharmacists is both considerable and consistent. Conclusions In recent years, the concerns about UV radiation have shifted from the short-term hazards of sunburn to the long-term hazards of skin cancer and premature aging of the skin. Available data suggest that a life-long approach to minimizing exposure to UV radiation including the use of sunscreens with a minimum sun protection factor of 15 will reduce overall morbidity and mortality. Authorities in the field are calling for the continuing development of commercial sunscreen products that provide a broad spectrum of protection against both UVA and UVB and their proper use by the public.

Radiation-induced hearing impairment--a pilot study in patients treated for malignant parotid tumours.

There are few reports in the literature concerning the long-term effects of radiation on hearing. A recent paper reviewed eight studies which estimated the incidence of post-irradiation hearing loss at 0–54% (Talmi et al, 1989). The nature of the impairment is unclear, since both sensorineural and conductive deafness are reported. Most surveys have studied patients with cancer of the nasopharynx or paediatric tumours, the management of which require bilateral radiotherapy techniques, thus any deterioration in hearing that may occur after radiotherapy (XRT) owing to the lack of controls cannot be definitely ascribed to the effects of ionizing radiation. Radical radiation of parotid tumours involves unilateral techniques which encompass the entire ear. The 10 year survival from parotid tumours is high—71% at the Princess Margaret Hospital (PMH) (Theriault & Fitzpatrick, 1986)—and, therefore, such patients are ideal candidates to be evaluated for the long-term effects of XRT on the ear. We recently reviewed 269 patients with malignant parotid tumours treated at PMH between 1970 and 1986 and noted that 10 patients out of 202 who received XRT reported unilateral hearing loss during follow-up. This number may be an underestimate of the true incidence because auditory function is not routinely discussed at routine follow-up visits. Therefore, in an attempt to elucidate the magnitude of this problem, we contacted all patients in the above survey treated between 1978 and 1983, who therefore had at least 7 years of follow-up, and we requested their attendance for a formal audiometric evaluation.

Radiosensitivity of small-cell lung cancer xenografts compared with activity of c-myc, N-myc, L-myc, c-raf-1 and K-ras proto-oncogenes.

Oncogenes of the myc family c-raf-1 and K-ras have been reported to modulate radiosensitivity. We examined the possible relationship between in vivo radiosensitivity to single-dose irradiation with 3-10 Gy, and activity of these proto-oncogenes in 2 sets of small-cell lung cancer (SCLC) xenografts, the CPH and the GLC series. CPH-54A and CPH-54B are in vitro-derived subclones of a SCLC cell line, while the GLC tumours were established as cell lines from a patient during longitudinal follow-up. Both tumours were later transferred into nude mice. CPH-54A was more sensitive to single-dose irradiation than CPH-54B, while, with respect to the 3 GLC tumours examined, GLC-16 was most sensitive, followed by GLC-14 and GLC-19. The CPH tumours expressed similar amounts of c-myc and c-raf-1 mRNA, and neither expressed N-myc or L-myc. GLC-14 expressed N-myc and c-raf-1 mRNA but no c-myc. GLC-16 and GLC-19 expressed identical amounts of c-raf-1 and high levels of c-myc mRNA, but neither expressed N-myc or L-myc. None of the tumours was mutated at codon 12 or K-ras. Our results show that SCLC xenografts with different radiosensitivity may express identical amounts of some of the proto-oncogenes reported to modulate radiosensitivity. Thus, factors other than activation of the examined proto-oncogenes must be involved in causing the differences in radiosensitivity found in the SCLC xenografts. Possible long-term effects of irradiation on proto-oncogene expression was examined in xenografts of GLC-16, following regrowth after single-dose irradiation. No long-term difference in expression of c-raf-1 or c-myc mRNA was detected between control tumours and tumours irradiated with 5 or 10 Gy.

Advances in the Care of Children with Brain Tumors

Recent advances in diagnostic imaging, neurosurgical techniques and oncologic therapies provide a more optimistic outlook for practitioners, children with brain tumors and their families. Newer imaging modalities such as magnetic resonance imaging and positron emission tomography improve accuracy of both initial diagnosis and follow-up evaluation for recurrence or metastasis. Recent advances in microsurgical technique allow for more complete tumor resection. Improving immunological and chemotherapeutic agents show future promise for tumor-specific treatment. Craniospinal irradiation techniques are changing in response to research into long-term effects of radiation on the developing nervous system and patterns of tumor recurrence and metastasis. Stereotactic radiation allows high-dose radiation to be given to focal areas minimizing radiation effects to surrounding normal structures. These changes impact the nursing care of children, requiring neuroscience nurses to be aware of current treatment modalities. Greater awareness of these changes ensures optimum patient care.

Protracted Treatment of C57B1 Mice with Zn-DTPA after241Am Injection Reduces the Long-term Radiation Effects

Repeated intraperitoneal injections of ZnNa3-diethylenetriaminepenta-acetate (ZnDTPA), once a week, during 8 successive weeks, and starting 4 days after injection of 58 and 373 kBq 241Am/kg to C57B1 mice, were an effective protection against long-term radiation damage. At both dose levels of 241Am, Zn-DTPA reduced the 241Am concentration in bones by between 33% and 45%, and in the liver by 97%. Mean survival with 241Am was shortened in Zn-DTPA-treated mice, by 17% at the lower dose level and by 70% at the higher dose level. After treatment with DTPA at the lower 241Am level, survival became equal to that of control mice without 241Am, while at the higher level life span was still shortened. After the lower 241Am dose the incidence of bone tumours, liver carcinomas and the total number of all malignant tumours were significantly reduced by chelation therapy. The decrease in bone tumour incidence was proportional to the decrease in 241Am concentration and reduction in cumulative radiation dose in bone after chelation therapy. The incidence of liver carcinomas was reduced to that in non-241Am-injected mice and the reduction was thus proportional to the 97% reduction in 241Am concentration of the liver at the end of chelation therapy. After the higher 241Am dose no tumours showed up in sham-treated mice, probably due to the overkill effect on the cells at risk. In the corresponding Zn-DTPA-treated mice, bone tumours and a few other malignant tumours were observed.

Case report 571

A case of a 23-year-old man with deformities of the spine and hip is presented, demonstrating the bizarre long term effects of radiation on developing bone. The spectrum of radiation-induced growth abnormalities is reviewed. Multiple variables, including age of the patient, the quantity of radiation delivered, and the site of delivery, all effect the eventual radiographic appearance.

Book reviews

This multi-author book is an authoritative review of the longterm effects of chemotherapy and radiation on bone marrow function. The editors must be commended on their choice of authors who have not only made contributions to the field but are also able to write clearly and concisely. The bibliographies at the end of each chapter are in general good and will be of considerable help to the reader wishing to pursue an issue further.

Nonlinear seismic analysis of a graphite reactor core

Design and construction of the Department of Energy's N-Reactor located in Richland, Washington was begun in the late 1950s and completed in the early 1960s. Since then, the reactor core's structural integrity has been under review and is considered by some to be a possible safety concern. The reactor core is moderated by graphite. The safety concern stems from the degradation of the graphite due to the effects of long-term irradiation. To assess the safety of the reactor core when subjected to seismic loads, a dynamic time-history structural analysis was performed. The graphite core consists of 89 layers of numerous graphite blocks which are assembled in a ‘lincoln-log’ lattice. This assembly permits venting of steam in the event of a pressure tube rupture. However, such a design gives rise to a highly nonlinear structure when subjected to earthquake loads. The structural model accounted for the nonlinear interlayer sliding and for the closure and opening of gaps between the graphite blocks. The model was subjected to simulated earthquake loading, and the time-varying response of selected elements critical to safety were monitored. The analytically predicted responses (displacements and strains) were compared to allowable responses to assess margins of safety.

Long-term radiation effects on gallium arsenide directional coupler optical waveguides

The effects of 1.17-MeV and 1.33-MeV gamma rays on the propagation characteristics of a gallium arsenide directional coupler optical waveguide is reported. Under doses of 4100-190000 rad (GaAs), no measurable change in either coupling characteristics or transmission loss was found. However, it is uncertain whether the radiation-induced loss component in the optical waveguides is less than 3 dB. A suggestion for eliminating this optical-alignment-induced experimental uncertainty is given.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A Comparative Study between Individuals Receiving Thymic Irradiation in Infancy and Their Nontreated Siblings: Clinical and Laboratory Thyroid Abnormalities

While impairment of thyroid function has been demonstrated for high-dose external radiation (e.g., for Hodgkin's disease), the long-term functional effects of low-dose external radiation have not been fully explored. One hundred fifty-three subjects with a past history of thymic irradiation during infancy were stratified into three dose levels and compared with 51 nonirradiated subjects from a sibling cohort with respect to previously undiagnosed clinical and laboratory thyroidal abnormalities. There was no apparent association between previous thymic irradiation and mean serum levels of T4, free T4, TSH, or antithyroid antibodies, nor was the prevalence of undetected hypothyroidism or hyperthyroidism significantly altered in the irradiated group. Serum thyroglobulin levels were elevated in subjects with palpable thyroid nodules, all of which occurred in thymic-irradiated subjects. Thus persons who have received low-level external thymic irradiation in infancy should continue to have periodic thyroid examinations, but routine serial measurement of other serum thyroidal parameters does not appear to be indicated.

The effect of long-term irradiation with fluorescent light on the rat fundus.

In the rat, continuous exposure to so-called "cold light" of 800 lux leads to a nearly complete loss of retinal photoreceptors, which occurs within 4 weeks. This process is followed by vascularization of the retinal pigment epithelium (RPE). The origin, extent, and expansion of such proliferations within 6 months after the onset of irradiation were evaluated by means of light microscopy, transmission electron microscopy, scanning electron microscopy, corrosion cast preparation, india ink injection, and trypsin digest preparation. The vessels within the RPE were found to be fenestrated and to form a network with the vessels of the neurosensory retina. Invasion of Bruch's membrane and formation of chorioretinal anastomoses were not observed. The occurrence of vessels within the RPE coincided with a massive regression of capillaries in the neurosensory retina.

Histopathological changes in dental pulp in rats after irradiation of Nd:YAG laser

The long-term effects of irradiation with the continuous wave Nd: YAG laser on the dental pulp of the rats were examined histopathologically. The rat mandibular first molar with or without the coating of laser absorption black material (Indian ink) was irradiated by the Nd: YAG laser, and the histopathological changes of the dental pulp were examined immediately, 1 week, 1 month, 4 months, 6 months and 12 months after the irradiation. The pulp of the lased teeth with Indian ink coating showed a marked formation of the secondary dentin following prominent cellular dynamics. Immediately after irradiation, the pulp showed exudative inflammatory changes with hyperemia and focal degeneration of the odontoblasts. One week after irradiation, these changes improved with the proliferation of the differentiated mesenchymal cells. Subsequently, the odontoblastic layer became thickened with differentiation of new odontoblasts. After 4 months, the pulp space gradually became reduced in size with the continuous formation of the secondary dentin. On the contrary, the pulp of the lased teeth without the Indian ink coating did not show any cellular dynamics and formation of the secondary dentin. These results suggested that the irradiation of the rat molar with the continuous wave Nd: YAG laser would have some kind of prolonged biological effects on the dental pulp tissue when the teeth are coated with laser absorption black material.

Radiation-induced thyroid and other head and neck tumors: occurrence of multiple tumors and analysis of risk factors.

In 2561 patients who received conventional external radiation treatment before age 15 yr for benign conditions of the head, neck, and upper thoracic area, we found an increase in the number of salivary gland tumors and benign neural tumors of the head and neck area. To determine whether patients who developed these relatively uncommon tumors were more susceptible to the long term effects of radiation, we analyzed how frequently these patients also developed benign and malignant thyroid neoplasms. Compared to the remainder of the irradiated population, the patients with salivary and neural tumors had an increased frequency of thyroid disease (19.4% vs. 11.2% for thyroid cancer and 52.4% vs. 39.9% for all thyroid nodules). Various risk factors were studied to determine whether they were related to the eventual occurrence of thyroid disease. Higher doses, being female, and lower ages at time of treatment were associated with increased risk. However, these factors did not fully explain the differences in the frequency of coexisting tumors, suggesting that additional factors, such as radiation sensitivity, may account for the increased risk.

The effect of space radiation of the nervous system

The long-term effects of irradiation by accelerated heavy ions on the structure and function of the nervous system have not been studied extensively. Although the adult brain is relatively resistant to low LET radiation, cellular studies indicate that individual heavy ions can produce serious membrane lesions and multiple chromatin breaks. Capillary hemorrhages may follow high LET particle irradiation of the developing brain as high RBE effects. Evidence has been accumulating that the glial system and blood-brain barrier (BBB) are relatively sensitive to injury by ionizing radiation. While DNA repair is active in neural systems, it may be assumed that a significant portion of this molecular process is misrepair. Since the expression of cell lethality usually requires cell division, and nerve cells have an extremely low rate of division, it is possible that some of the characteristic changes of premature aging may represent a delayed effect of chromatin misrepair in brain. Altered microcirculation, decreased local metabolism, entanglement and reduction in synaptic density, premature loss of neurons, myelin degeneration, and glial proliferation are late signs of such injuries. HZE particles are very efficient in producing carcinogenic cell transformation, reaching a peak for iron particles. The promotion of viral transformation is also efficient up to an energy transfer of approximately 300 keV/micron. The RBE for carcinogenesis in nerve tissues remains unknown. On the basis of available information concerning HZE particle flux in interplanetary space, only general estimates of the magnitude of the effects of long-term spaceflight on some nervous system parameters may be constructed.

Scanning electron microscopic study of microvascular anastomoses on irradiated vessels: long-term effect of irradiation.

A study was performed to determine the effect of preoperative irradiation on microvascular arterial anastomoses. The study focused on microthrombi and epithelial regeneration. Using scanning electron microscopy (SEM), a clear difference was seen comparing nonirradiated to irradiated vessels. No difference was found between short- and long-term effects of irradiation.

Short- and Long-Term Effects of Irradiation on Bone Regeneration

Jacobsson, Magnus G. M.D.; Jonsson, Anders K. M.D.; Albrektsson, Tomas O. M.D., Ph.D.; Turesson, Ingela E. M.D., Ph.D.; Saha, Subrata Ph.D. Author Information

Long-term residual radiation effect in the murine hematopoietic stem cell compartment.

For the measurement of long-term residual radiation effect in the murine hematopoietic system a test system was developed that quantifies the proliferation ability of progeny of spleen repopulating cells by the proliferation factor (PF). The PF expresses the ratios of 125IUdR incorporation in the recipient spleens at days 3 and 5 following cell transfusion, thus measuring the relative increase in number of proliferating cells. Following 500 rad whole-body gamma irradiation, PF recovered up to 6 months and remained thereafter, on the average, at 80% of control. Recovery of the number of 7-day CFU-S was similar to recovery of PF. Various studies were aimed at elucidating the reasons for reduction in PF. Loss of incorporated 125IUdR activity from spleens between days 3 and 5 after cell transfusion indicates loss of mature labeled cells. When the doubling time of proliferating cells of CFU-S progeny (td) is corrected for cell loss, td for control bone marrow approaches mitotic cycle time in normal bone marrow as was found elsewhere. Following 500 rad, both cell loss and td were initially increased and recovered in parallel with PF and number of CFU-S. Reduction of PF could be brought about by radiation-induced increase in transient CFU-S with the consequence of increased loss of mature cells between days 3 and 5. This possibility was excluded by the observation that 1 year after 500 rad the number of colonies per spleen did not decrease from day 7 to day 12 after cell transfusion, as was expected from a higher proportion of transient CFU-S, but increased more than in the controls. Measurement of these 12-day colonies showed a significantly reduced size. Average progeny from irradiated CFU-S, apparently, grow more slowly. It is concluded that sublethal injury resides in stem cells, increases mitotic cycle time, and causes precocious loss of cells from spleens probably by enhanced differentiation and maturation due to interference with endocellular control of cell proliferation and differentiation. Probably the observed recovery proceeds via replacement of injured stem cells by less injured or normal stem cells.

International Review of Child Neurology Series

Raven Press, a leader in publishing good neurology texts, has done it again. These two monographs, the second and third volumes of theInternational Review of Child Neurology Series, are excellent and timely reviews of two neurological disorders not recently reviewed elsewhere. The volumes are sponsored by the International Child Neurological Association, which is devoted to providing an outlet for the exchange of professional ideas and to advancing neurological sciences in infancy and childhood. These official publications of the association have definitely achieved that goal. The authorship is broad, representing a superb field of child neurology in the United States and throughout the world. Brain Tumors in Childrenincludes sections on principles of diagnosis and treatment, management, and complications. In this single volume new concepts of epidemiology, neuroradiologic diagnosis, surgical excision, radiation therapy, chemotherapy, and the long-term effects of radiation and chemotherapy are discussed. Case examples and algorithms are used