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Kleiman NJ, Edmondson EF, Weil MM, Fallgren CM, King A, Schmidt C, Hall EJ. Radiation cataract in Heterogeneous Stock mice after γ-ray or HZE ion exposure. LIFE SCIENCES IN SPACE RESEARCH 2024; 40:97-105. [PMID: 38245354 PMCID: PMC10800003 DOI: 10.1016/j.lssr.2023.09.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 09/12/2023] [Accepted: 09/13/2023] [Indexed: 01/22/2024]
Abstract
Health effects of space radiation are a serious concern for astronauts on long-duration missions. The lens of the eye is one of the most radiosensitive tissues in the body and, therefore, ocular health risks for astronauts is a significant concern. Studies in humans and animals indicate that ionizing radiation exposure to the eye produces characteristic lens changes, termed "radiation cataract," that can affect visual function. Animal models of radiation cataractogenesis have previously utilized inbred mouse or rat strains. These studies were essential for determining morphological changes and dose-response relationships between radiation exposure and cataract. However, the relevance of these studies to human radiosensitivity is limited by the narrow phenotypic range of genetically homogeneous animal models. To model radiation cataract in genetically diverse populations, longitudinal cataract phenotyping was nested within a lifetime carcinogenesis study in male and female heterogeneous stock (HS/Npt) mice exposed to 0.4 Gy HZE ions (n = 609) or 3.0 Gy γ-rays (n = 602) and in unirradiated controls (n = 603). Cataractous change was quantified in each eye for up to 2 years using Merriam-Focht grading criteria by dilated slit lamp examination. Virtual Optomotry™ measurement of visual acuity and contrast sensitivity was utilized to assess visual function in a subgroup of mice. Prevalence and severity of posterior lens opacifications were 2.6-fold higher in HZE ion and 2.3-fold higher in γ-ray irradiated mice compared to unirradiated controls. Male mice were at greater risk for spontaneous and radiation associated cataracts. Risk for cataractogenesis was associated with family structure, demonstrating that HS/Npt mice are well-suited to evaluate genetic determinants of ocular radiosensitivity. Last, mice were extensively evaluated for cataract and tumor formation, which revealed an overlap between individual susceptibility to both cancer and cataract.
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Affiliation(s)
- Norman J Kleiman
- Department of Environmental Health Sciences, Eye Radiation and Environmental Research Laboratory, Columbia University, Mailman School of Public Health, 722 West 168th St., 11th Floor, New York, NY, 10032, United States.
| | - Elijah F Edmondson
- Department of Microbiology, Immunology and Pathology, Colorado State University, Fort Collins, CO, 80523, United States; Frederick National Laboratory for Cancer Research, Frederick, Maryland, 21702, United States
| | - Michael M Weil
- Department of Environment and Radiological Health Sciences, Colorado State University, Fort Collins, CO, 80523, United States
| | - Christina M Fallgren
- Department of Environment and Radiological Health Sciences, Colorado State University, Fort Collins, CO, 80523, United States
| | - Adam King
- Department of Clinical Sciences, Colorado State University, Fort Collins, CO, 80523, United States; MedVet Chicago, Chicago, IL, 60618, United States
| | - Catherine Schmidt
- Department of Clinical Sciences, Colorado State University, Fort Collins, CO, 80523, United States; Veterinary Eye Specialists, Thornwood, NY, 10594, , United States
| | - Eric J Hall
- Center for Radiological Research, Columbia University, College of Physicians and Surgeons, 630W. 168th St., New York, NY,10032, , United States
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From international ophthalmology to space ophthalmology: the threats to vision on the way to Moon and Mars colonization. Int Ophthalmol 2019; 40:775-786. [PMID: 31722052 DOI: 10.1007/s10792-019-01212-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 10/28/2019] [Indexed: 12/29/2022]
Abstract
PURPOSE To report the ophthalmological risks of space travel. METHODS The literature about the effect of microgravity and cosmic radiation on the human eye has been reviewed, focusing on the so-called "spaceflight related neuro-ocular syndrome (SANS)", and possible remedies. RESULTS The eye is the major candidate to suffer from the adverse space conditions, so much so that SANS is the main concern of the National Aeronautics and Space Administration (NASA). SANS, that affects astronauts engaged in long-duration spaceflights, is characterized by optic nerve head swelling, flattening of the posterior region of the scleral shell, choroidal folds, retinal cotton wool spots, and hyperopic shift. Even if it seems related to an increased volume of the cerebrospinal fluid in the brain and the optic nerve sheaths, its pathogenesis is still unclear. In addition, cataract is related to the effect of galactic cosmic rays on the lens. Centrifuges, pressurizing chambers, and mechanical counter-pressure suits have been advanced to counteract the upward fluid shift responsible for the SANS syndrome. Shields with a high content of hydrogen, magnetic shielding systems, and wearable radiation shielding devices are under study to mitigate the exposure to galactic cosmic rays. CONCLUSIONS Since 1961, the year of the first manned mission outside the Earth, history has shown that the human being may venture in space. Yet, visual impairment is the top health risk for long-duration spaceflight. Effective remediation is mandatory in anticipation of long space missions and Moon and Mars colonization.
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The Effect of Microgravity on Ocular Structures and Visual Function: A Review. Surv Ophthalmol 2013; 58:155-63. [DOI: 10.1016/j.survophthal.2012.04.002] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Revised: 04/08/2012] [Accepted: 04/10/2012] [Indexed: 11/17/2022]
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Abstract
Until very recently, ocular exposure guidelines were based on the assumption that radiation cataract is a deterministic event requiring threshold doses generally greater than 2 Gy. This view was, in part, based on older studies which generally had short follow-up periods, failed to take into account increasing latency as dose decreased, had relatively few subjects with doses below a few Gy, and were not designed to detect early lens changes. Newer findings, including those in populations exposed to much lower radiation doses and in subjects as diverse as astronauts, medical workers, atomic bomb survivors, accidentally exposed individuals, and those undergoing diagnostic or radiotherapeutic procedures, strongly suggest dose-related lens opacification at significantly lower doses. These observations resulted in a recent re-evaluation of current lens occupational exposure guidelines, and a proposed lowering of the presumptive radiation cataract threshold to 0.5 Gy/year and the occupational lens exposure limit to 20 mSv/year, regardless of whether received as an acute, protracted, or chronic exposure. Experimental animal studies support these conclusions and suggest a role for genotoxicity in the development of radiation cataract. Recent findings of a low or even zero threshold for radiation-induced lens opacification are likely to influence current research efforts and directions concerning the cellular and molecular mechanisms underlying this pathology. Furthermore, new guidelines are likely to have significant implications for occupational and/or accidental exposure, and the need for occupational eye protection (e.g. in fields such as interventional medicine).
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Affiliation(s)
- N J Kleiman
- Eye Radiation and Environmental Research Laboratory, Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, NY 10032, USA.
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Stewart FA, Akleyev AV, Hauer-Jensen M, Hendry JH, Kleiman NJ, Macvittie TJ, Aleman BM, Edgar AB, Mabuchi K, Muirhead CR, Shore RE, Wallace WH. ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs--threshold doses for tissue reactions in a radiation protection context. Ann ICRP 2012; 41:1-322. [PMID: 22925378 DOI: 10.1016/j.icrp.2012.02.001] [Citation(s) in RCA: 810] [Impact Index Per Article: 67.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
This report provides a review of early and late effects of radiation in normal tissues and organs with respect to radiation protection. It was instigated following a recommendation in Publication 103 (ICRP, 2007), and it provides updated estimates of 'practical' threshold doses for tissue injury defined at the level of 1% incidence. Estimates are given for morbidity and mortality endpoints in all organ systems following acute, fractionated, or chronic exposure. The organ systems comprise the haematopoietic, immune, reproductive, circulatory, respiratory, musculoskeletal, endocrine, and nervous systems; the digestive and urinary tracts; the skin; and the eye. Particular attention is paid to circulatory disease and cataracts because of recent evidence of higher incidences of injury than expected after lower doses; hence, threshold doses appear to be lower than previously considered. This is largely because of the increasing incidences with increasing times after exposure. In the context of protection, it is the threshold doses for very long follow-up times that are the most relevant for workers and the public; for example, the atomic bomb survivors with 40-50years of follow-up. Radiotherapy data generally apply for shorter follow-up times because of competing causes of death in cancer patients, and hence the risks of radiation-induced circulatory disease at those earlier times are lower. A variety of biological response modifiers have been used to help reduce late reactions in many tissues. These include antioxidants, radical scavengers, inhibitors of apoptosis, anti-inflammatory drugs, angiotensin-converting enzyme inhibitors, growth factors, and cytokines. In many cases, these give dose modification factors of 1.1-1.2, and in a few cases 1.5-2, indicating the potential for increasing threshold doses in known exposure cases. In contrast, there are agents that enhance radiation responses, notably other cytotoxic agents such as antimetabolites, alkylating agents, anti-angiogenic drugs, and antibiotics, as well as genetic and comorbidity factors. Most tissues show a sparing effect of dose fractionation, so that total doses for a given endpoint are higher if the dose is fractionated rather than when given as a single dose. However, for reactions manifesting very late after low total doses, particularly for cataracts and circulatory disease, it appears that the rate of dose delivery does not modify the low incidence. This implies that the injury in these cases and at these low dose levels is caused by single-hit irreparable-type events. For these two tissues, a threshold dose of 0.5Gy is proposed herein for practical purposes, irrespective of the rate of dose delivery, and future studies may elucidate this judgement further.
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Dynlacht JR, Valluri S, Garrett J, Mendonca MS, Lopez JT, Caperell-Grant A, Bigsby RM. Age and hormonal status as determinants of cataractogenesis induced by ionizing radiation. I. Densely ionizing (high-LET) radiation. Radiat Res 2010; 175:37-43. [PMID: 21175345 DOI: 10.1667/rr2319.1] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Astronauts participating in extended lunar missions or the projected mission to Mars would likely be exposed to significant doses of high-linear energy transfer (LET) heavy energetic charged (HZE) particles. Exposure to even relatively low doses of such space radiation may result in a reduced latent period for and an increased incidence of lens opacification. However, the determinants of cataractogenesis induced by densely ionizing radiation have not been clearly elucidated. In the current study, we show that age at the time of exposure is a key determinant of cataractogenesis in rats whose eyes have been exposed to 2 Gy of (56)Fe ions. The rate of progression of cataractogenesis was significantly greater in the irradiated eyes of 1-year-old rats compared to young (56-day-old) rats. Furthermore, older ovariectomized rats that received exogenous estrogen treatment (17-β-estradiol) commencing 1 week prior to irradiation and continuing throughout the period of observation of up to approximately 600 days after irradiation showed an increased incidence of cataracts and faster progression of opacification compared to intact rats with endogenous estrogen or ovariectomized rats. The same potentiating effect (higher incidence, reduced latent period) was observed for irradiated eyes of young rats. Modulation of estrogen status in the 1-year-old animals (e.g., removal of estrogen by ovariectomy or continuous exposure to estrogen) did not increase the latent period or reduce the incidence to that of intact 56-day-old rats. Since the rapid onset and progression of cataracts in 1-year-old compared to 56-day-old rats was independent of estrogen status, we conclude that estrogen cannot account for the age-dependent differences in cataractogenesis induced by high-LET radiation.
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Affiliation(s)
- Joseph R Dynlacht
- Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.
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Davis JG, Wan XS, Ware JH, Kennedy AR. Dietary supplements reduce the cataractogenic potential of proton and HZE-particle radiation in mice. Radiat Res 2010; 173:353-61. [PMID: 20199220 DOI: 10.1667/rr1398.1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Abstract The present study was undertaken to investigate the ability of dietary supplements to reduce the formation and severity of cataracts in mice irradiated with high-energy protons or iron ions, which are important components of the radiation encountered by astronauts during space travel. The mice were exposed to proton or iron-ion radiation and fed with a control diet or diets supplemented with the soybean-derived protease inhibitor, Bowman-Birk inhibitor (BBI), in the form of BBI Concentrate (BBIC) or an antioxidant formulation [containing l-selenomethionine (SeM), N-acetyl cysteine (NAC), ascorbic acid, co-enzyme Q10, alpha-lipoic acid and vitamin E succinate] both before and after the radiation exposure. At approximately 2 years after the radiation exposure, the animals were killed humanely and lenses were harvested and characterized using an established classification system that assigns discrete scores based on the severity of the lens opacifications. The results showed that exposure to 1 GeV/nucleon proton (3 Gy) or iron-ion (50 cGy) radiation significantly increased the cataract prevalence and severity in CBA/J mice to levels above the baseline levels of age-induced cataract formation in this mouse strain. Treatment with BBIC or the antioxidant formulation significantly reduced the prevalence and severity of the lens opacifications in the mice exposed to iron-ion radiation. Treatment with BBIC or the antioxidant formulation also decreased the severity of the lens opacifications in the mice exposed to proton radiation; however, the decrease did not reach statistical significance. These results indicate that BBIC and the antioxidant formulation evaluated in this study could be useful for protecting astronauts against space radiation-induced cataracts during or after long-term manned space missions.
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Affiliation(s)
- James G Davis
- Department of Radiation Oncology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6072, USA
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Henderson MA, Valluri S, Garrett J, Lopez JT, Caperell-Grant A, Mendonca MS, Rusek A, Bigsby RM, Dynlacht JR. Effects of estrogen and gender on cataractogenesis induced by high-LET radiation. Radiat Res 2010; 173:191-6. [PMID: 20095851 DOI: 10.1667/rr1917.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Planning for long-duration manned lunar and interplanetary missions requires an understanding of radiation-induced cataractogenesis. Previously, it was demonstrated that low-linear energy transfer (LET) irradiation with 10 Gy of (60)Co gamma rays resulted in an increased incidence of cataracts in male rats compared to female rats. This gender difference was not due to differences in estrogen, since male rats treated with the major secreted estrogen 17-beta-estradiol (E2) showed an identical increase compared to untreated males. We now compare the incidence and rate of progression of cataracts induced by high-LET radiation in male and female Sprague-Dawley rats. Rats received a single dose of 1 Gy of 600 MeV (56)Fe ions. Lens opacification was measured at 2-4-week intervals with a slit lamp. The incidence and rate of progression of radiation-induced cataracts was significantly increased in the animals in which estrogen was available from endogenous or exogenous sources. Male rats with E2 capsules implanted had significantly higher rates of progression compared to male rats with empty capsules implanted (P = 0.025) but not compared to the intact female rats. These results contrast with data obtained after low-LET irradiation and suggest the possibility that the different types of damage caused by high- and low-LET radiation may be influenced differentially by steroid sex hormones.
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Affiliation(s)
- Mark A Henderson
- Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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Kleiman NJ, David J, Elliston CD, Hopkins KM, Smilenov LB, Brenner DJ, Worgul BV, Hall EJ, Lieberman HB. Mrad9 and Atm Haploinsufficiency Enhance Spontaneous and X-Ray-Induced Cataractogenesis in Mice. Radiat Res 2007; 168:567-73. [PMID: 17973559 DOI: 10.1667/rr1122.1] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2007] [Accepted: 07/02/2007] [Indexed: 11/03/2022]
Affiliation(s)
- Norman J Kleiman
- Center for Radiological Research, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA
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Hall EJ, Worgul BV, Smilenov L, Elliston CD, Brenner DJ. The relative biological effectiveness of densely ionizing heavy-ion radiation for inducing ocular cataracts in wild type versus mice heterozygous for the ATM gene. RADIATION AND ENVIRONMENTAL BIOPHYSICS 2006; 45:99-104. [PMID: 16799786 DOI: 10.1007/s00411-006-0052-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2005] [Accepted: 05/08/2006] [Indexed: 05/10/2023]
Abstract
The accelerated appearance of ocular cataracts at younger ages has been recorded in both astronauts and airline pilots, and is usually attributed to high-energy heavy ions in galactic cosmic ray radiation. We have previously shown that high-LET 1-GeV/nucleon (56)Fe ions are significantly more effective than X-rays in producing cataracts in mice. We have also shown that mice haploinsufficient for ATM develop cataracts earlier than wild-type animals, when exposed to either low-LET X-rays or high-LET (56)Fe ions. In this paper we derive quantitative estimates for the relative biological effectiveness (RBE) of high energy (56)Fe ions compared with X-rays, both for wild type and for mice haploinsufficient for ATM. There is a clear trend toward higher RBE's in haploinsufficient animals, both for low- and high-grade cataracts. Haploinsufficiency for ATM results in an enhanced sensitivity to X-rays compared with the wild type, and this enhancement appears even larger after exposure to high-LET heavy ions.
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Affiliation(s)
- Eric J Hall
- Center for Radiological Research, Columbia University Medical Center, 630 West 168th Street, New York, NY 10032, USA.
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Baumstark-Khan C, Heilmann J, Rink H. Induction and repair of DNA strand breaks in bovine lens epithelial cells after high LET irradiation. ADVANCES IN SPACE RESEARCH : THE OFFICIAL JOURNAL OF THE COMMITTEE ON SPACE RESEARCH (COSPAR) 2003; 31:1583-1591. [PMID: 12971414 DOI: 10.1016/s0273-1177(03)00095-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The lens epithelium is the initiation site for the development of radiation induced cataracts. Radiation in the cortex and nucleus interacts with proteins, while in the epithelium, experimental results reveal mutagenic and cytotoxic effects. It is suggested that incorrectly repaired DNA damage may be lethal in terms of cellular reproduction and also may initiate the development of mutations or transformations in surviving cells. The occurrence of such genetically modified cells may lead to lens opacification. For a quantitative risk estimation for astronauts and space travelers it is necessary to know the relative biological effectiveness (RBE), because the spacial and temporal distribution of initial physical damage induced by cosmic radiation differ significantly from that of X-rays. RBEs for the induction of DNA strand breaks and the efficiency of repair of these breaks were measured in cultured diploid bovine lens epithelial cells exposed to different LET irradiation to either 300 kV X-rays or to heavy ions at the UNILAC accelerator at GSI. Accelerated ions from Z=8 (O) to Z=92 (U) were used. Strand breaks were measured by hydroxyapatite chromatography of alkaline unwound DNA (overall strand breaks). Results showed that DNA damage occurs as a function of dose, of kinetic energy and of LET. For particles having the same LET the severity of the DNA damage increases with dose. For a given particle dose, as the LET rises, the numbers of DNA strand breaks increase to a maximum and then reach a plateau or decrease. Repair kinetics depend on the fluence (irradiation dose). At any LET value, repair is much slower after heavy ion exposure than after X-irradiation. For ions with an LET of less than 10,000 keV micrometers-1 more than 90 percent of the strand breaks induced are repaired within 24 hours. At higher particle fluences, especially for low energetic particles with a very high local density of energy deposition within the particle track, a higher proportion of non-rejoined breaks is found, even after prolonged periods of incubation. At the highest LET value (16,300 keV micrometers-1) no significant repair is observed. These LET-dependencies are consistent with the current mechanistic model for radiation induced cataractogenesis which postulates that genomic damage to the surviving fraction of epithelial cells is responsible for lens opacification.
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Affiliation(s)
- C Baumstark-Khan
- Institute of Aerospace Medicine, German Aerospace Center, Koln, Germany.
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Worgul BV, Krebs W, Koniarek JP. Microlesions: theory and reality. ADVANCES IN SPACE RESEARCH : THE OFFICIAL JOURNAL OF THE COMMITTEE ON SPACE RESEARCH (COSPAR) 1989; 9:315-323. [PMID: 11537311 DOI: 10.1016/0273-1177(89)90454-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Efforts to assess radiation risk in space have been complicated by the considerable unknowns regarding the biological effects of the heavy ion component (HZE particles) of the cosmic rays. The attention has focused primarily on the assignation of a quality factor (Q) which would take into account the greater effectiveness of heavy ions vis-a-vis other forms of ionizing radiation. If however, as the so-called "Microlesion Theory" allows, the passage of HZE particles through living tissue produces unique biological damage, the traditional use of Q becomes meaningless. Therefore, it is critical to determine if microlesions, in fact, do exist. While the concept does not necessarily require detectable morphological damage, "tunnel-lesions" or holes in ocular tissues have been cited as evidence of microlesions. These data, however, are open to reinterpretation. On-going light, scanning and transmission electron microscopic studies of the corneas, lenses and retinas of rat eyes exposed to 450 MeV/amu 56Fe ions thus far have not revealed tunnel-lesion damage. The morphological effects of the heavy ions have been found to be qualitatively similar to the changes following other kinds of ionizing radiation.
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Affiliation(s)
- B V Worgul
- Department of Ophthalmology, Columbia University, NY
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Ainsworth EJ, Afzal SM, Crouse DA, Hanson WR, Fry RJ. Tissue responses to low protracted doses of high LET radiations or photons: early and late damage relevant to radio-protective countermeasures. ADVANCES IN SPACE RESEARCH : THE OFFICIAL JOURNAL OF THE COMMITTEE ON SPACE RESEARCH (COSPAR) 1989; 9:299-313. [PMID: 11537307 DOI: 10.1016/0273-1177(89)90453-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Early and late murine tissue responses to single or fractionated low doses of heavy charged particles, fission-spectrum neutrons or gamma rays are considered. Damage to the hematopoietic system is emphasized, but results on acute lethality, host response to challenge with transplanted leukemia cells and life-shortening are presented. Low dose rates per fraction were used in some neutron experiments. Split-dose lethality studies (LD 50/30) with fission neutrons indicated greater accumulation of injury during a 9 fraction course (over 17 days) than was the case for gamma-radiation. When total doses of 96 or 247 cGy of neutrons or gamma rays were given as a single dose or in 9 fractions, a significant sparing effect on femur CFU-S depression was observed for both radiation qualities during the first 11 days, but there was not an earlier return to normal with dose fractionation. During the 9 fraction sequence, a significant sparing effect of low dose rate on CFU-S depression was observed in both neutron and gamma-irradiated mice. CFU-S content at the end of the fractionation sequence did not correlate with measured LD 50/30. Sustained depression of femur and spleen CFU-S and a significant thrombocytopenia were observed when a total neutron dose of 240 cGy was given in 72 fractions over 24 weeks at low dose rates. The temporal aspects of CFU-S repopulation were different after a single versus fractionated neutron doses. The sustained reduction in the size of the CFU-S population was accompanied by an increase in the fraction in DNA synthesis. The proliferation characteristics and effects of age were different for radial CFU-S population closely associated with bone, compared with the axial population that can be readily aspirated from the femur. In aged irradiated animals, the CFU-S proliferation/redistribution response to typhoid vaccine showed both an age and radiation effect. After high single doses of neutrons or gamma rays, a significant age- and radiation-related deficiency in host defense mechanisms was detected by a shorter mean survival time following challenge with transplantable leukemia cells. Comparison of dose-response curves for life shortening after irradiation with fission-spectrum neutrons or high energy silicon particles indicated high initial slopes for both radiation qualities at low doses, but for higher doses of silicon, the effect per Gy decreased to a value similar to that for gamma rays. The two component life-shortening curve for silicon particles has implications for the potential efficacy of radioprotectants. Recent studies on protection against early and late effects by aminothiols, prostaglandins, and other compounds are discussed.
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Affiliation(s)
- E J Ainsworth
- Lawrence Berkeley Laboratory, University of California, Berkeley 94720
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Reitz G, Bucker H, Facius R, Horneck G, Graul EH, Berger H, Ruther W, Heinrich W, Beaujean R, Enge W, Alpatov AM, Ushakov IA, Mesland DA. Influence of cosmic radiation and/or microgravity on development of Carausius morosus. ADVANCES IN SPACE RESEARCH : THE OFFICIAL JOURNAL OF THE COMMITTEE ON SPACE RESEARCH (COSPAR) 1989; 9:161-173. [PMID: 11537289 DOI: 10.1016/0273-1177(89)90435-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Eggs of Carausius morosus were exposed to spaceflight conditions in two spaceflight missions, the German 7 day Spacelab Mission D1 and the Soviet 12.56 day Biosatellite Mission "COSMOS 1887". During spaceflight the eggs continued their development. Eggs of five different ages representing different sensitivity to radiation and different capacity to regeneration were used to investigate the influence of cosmic radiation and/or microgravity on insect development. Using the Biostack concept--eggs in monolayers sandwiched between nuclear track detectors--and the 1 g reference centrifuge of BIORACK in D1 we were able to separate effects of heavy ions of the cosmic radiation from microgravity effects and also from combined effects of these two factors in space. After retrieval, hatching rates, embryonic and larval growth kinetics and anomaly frequencies were determined. Microgravity leads to a reduced hatching rate of eggs exposed in the early stages of development. Hatching was normal in eggs which were exposed on the 1 g reference centrifuge. Hits by heavy ions caused body anomalies. The combined action of heavy ions and microgravity resulted in an unexpectedly high frequency of anomalies. These results obtained from the Spacelab Mission D1, were confirmed in an experiment onboard of COSMOS 1887. In addition to the previous analysis, embryonic development before hatching was followed which showed no major difference between flight and the ground control specimens. Since a reconfirmation of reduced hatching rates was observed in COSMOS 1887, too, the above results suggest some microgravity induced functional impairment of the hatching activity, rather than blockage in embryonic development.
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Affiliation(s)
- G Reitz
- DFVLR, Institute of Aerospace Medicine, Linder Hohe, Koln, F.R.G
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Ainsworth EJ. Early and late mammalian responses to heavy charged particles. ADVANCES IN SPACE RESEARCH : THE OFFICIAL JOURNAL OF THE COMMITTEE ON SPACE RESEARCH (COSPAR) 1986; 6:153-165. [PMID: 11537215 DOI: 10.1016/0273-1177(86)90288-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
This overview summarizes murine results on acute lethality responses, inactivation of marrow CFU-S and intestinal microcolonies, testes weight loss, life span shortening, and posterior lens opacification in mice irradiated with heavy charged particles. RBE-LET relationships for these mammalian responses are compared with results from in vitro studies. The trend is that the maximum RBE for in vivo responses tends to be lower and occurs at a lower LET than for inactivation of V79 and T-1 cells in culture. Based on inactivation cross sections, the response of CFU-S in vivo conforms to expectations from earlier studies with prokaryotic systems and mammalian cells in culture. Effects of heavy ions are compared with fission spectrum neutrons, and the results are consistent with the interpretation that RBEs are lower than for fission neutrons at about the same LET, probably due to differences in track structure. Issues discussed focus on challenges associated with assessments of early and late effects of charged particles based on dose, RBE and LET, and with the concordance or discordance of results obtained with in vivo and in vitro model systems. Models for radiation damage/repair and misrepair should consider effects observed with in vivo as well as in vitro model systems.
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Affiliation(s)
- E J Ainsworth
- Lawrence Berkeley Laboratory, University of California, Berkeley 94720, USA
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